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EP4637972A1 - <sup2/>? <sub2/>?2?réduction de la teneur en nox et no dans le dégagement gazeux d'installations de cuisson fonctionnant au nh <ns3:sub>3</ns3:sub> - Google Patents

<sup2/>? <sub2/>?2?réduction de la teneur en nox et no dans le dégagement gazeux d'installations de cuisson fonctionnant au nh <ns3:sub>3</ns3:sub>

Info

Publication number
EP4637972A1
EP4637972A1 EP23838095.0A EP23838095A EP4637972A1 EP 4637972 A1 EP4637972 A1 EP 4637972A1 EP 23838095 A EP23838095 A EP 23838095A EP 4637972 A1 EP4637972 A1 EP 4637972A1
Authority
EP
European Patent Office
Prior art keywords
exhaust gas
ppmv
combustion
catalyst
heat exchanger
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP23838095.0A
Other languages
German (de)
English (en)
Inventor
Michael Groves
Meinhard Schwefer
Alexander Kleyensteiber
Stefan PINNOW
Rolf Siefert
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ThyssenKrupp AG
ThyssenKrupp Industrial Solutions AG
Original Assignee
ThyssenKrupp AG
ThyssenKrupp Uhde GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ThyssenKrupp AG, ThyssenKrupp Uhde GmbH filed Critical ThyssenKrupp AG
Publication of EP4637972A1 publication Critical patent/EP4637972A1/fr
Pending legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9413—Processes characterised by a specific catalyst
    • B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/005—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by heat treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/343—Heat recovery
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8696—Controlling the catalytic process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/88—Handling or mounting catalysts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/90—Injecting reactants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9413—Processes characterised by a specific catalyst
    • B01D53/9427—Processes characterised by a specific catalyst for removing nitrous oxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
    • C01B3/047—Decomposition of ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/202—Hydrogen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/204—Carbon monoxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2062—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/208—Hydrocarbons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/10—Noble metals or compounds thereof
    • B01D2255/102—Platinum group metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20738—Iron
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20746—Cobalt
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20761—Copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/50—Zeolites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/904—Multiple catalysts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/40—Nitrogen compounds
    • B01D2257/402—Dinitrogen oxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/40—Nitrogen compounds
    • B01D2257/404—Nitrogen oxides other than dinitrogen oxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0283—Flue gases
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)

Definitions

  • the combustion system preferably comprises a combustion device in which NH3 is burned to generate combustion heat, as well as an NH3 decomposition device which is in heat exchange with the combustion device and in which NH3 is catalytically decomposed into N2 and H2.
  • the heat required for the catalytic decomposition of NH3 in the NH3 decomposition device is provided by the combustion of NH3 in the combustion device.
  • the combustion device preferably comprises at least one burner and a combustion chamber.
  • the combustion system is preferably designed analogously to a primary reformer. [0003]
  • H2 can be obtained from H2O using renewable energies and then converted into NH3 with N2.
  • NH3 can be stored and transported much more safely than H2.
  • NH3 can then be decomposed again into H2 and N2.
  • H2 finds a wide variety of industrial applications.
  • a variety of materials have been proposed as catalysts for the decomposition of NH3, which are active at different temperatures (cf. e.g. Il. Lucentini et al., Ind. Eng. Chem. Res.
  • NH 3 is liquid in cooled tanks at atmospheric pressure and -32.8°C.
  • a pump is used to pump NH 3 fed into the system at system pressure. Due to the increased system pressure, the boiling point of the NH 3 , e.g. at 27.8 bar a to about 62.2°C.
  • the NH 3 the supply of heat is necessary.
  • Conventional processes for the catalytic decomposition of NH3 generate considerable amounts of heat, which can be used to evaporate NH3.
  • US 4704267 A relates to the production of high-purity H 2 from liquid, anhydrous NH 3 NH3 is vaporized and then split into its constituents.
  • FR 1469045 A relates to an apparatus comprising a preheater fed with NH3, a tube bundle enclosing a catalyst for splitting NH3 and optionally a cell for purifying H2 by diffusion, which are connected to one another and located in a single housing containing heating means.
  • CN 111957270 A relates to an NH3 decomposition device comprising an NH3 decomposition unit and a combustion unit acting on the NH3 decomposition unit.
  • NH3 enters the NH3 decomposition unit via a first purified gas inlet to perform a decomposition reaction of NH3.
  • Produced mixed gas is discharged via a second purified gas outlet and then enters the combustion unit via a second purified gas inlet.
  • the mixed gas includes N2, H2 and undecomposed NH3.
  • the mixed gas enters the combustion unit to provide heat for the decomposition reaction of NH3 of the NH3 decomposition unit, so that self-sufficiency of heat is realized in the NH3 decomposition-H2 production system. No additional fuel is required for energy supply and the cost of NH 3 -Decomposition-H 2 -production system are reduced.
  • CN 113896168 A relates to a process for producing H2 or reducing gas by cracking NH3 with a two-stage process comprising the following steps:
  • the liquid NH3 of the raw material is completely gasified and heated by a heat exchange gasification system and then enters a heat exchange NH 3 -Cracking reaction system of the first stage to achieve partial NH 3 -Cracking reaction.
  • the reaction gas from the heat exchange NH 3 -Cracking- reaction system of the first stage enters a high temperature NH 3 -Cracking reaction system of the second stage to obtain a residual NH 3 -Crack reaction.
  • WO 2001/087770 A1 relates to the autothermal decomposition of NH 3 for the production of high purity H 2 .
  • WO 2011/107279 A1 relates to a NH 3 based H 2 -Generation reactor comprising a NH 3 -Gap chamber with a NH 3 - cracking catalyst, an inner combustion chamber with a combustion or oxidation catalyst which is in thermal contact with the NH3 cracking chamber, an NH3 gas preheating chamber and an outer shroud ring for heat recovery from the combustion products emerging from the combustion chamber, wherein the cracking chamber, the inner combustion chamber, the preheating chamber and the heat recovery shroud ring are arranged concentrically.
  • WO 2017/160154 A1 relates to a method for generating energy with a gas turbine, comprising the following steps: (i) evaporating and preheating liquid NH3 to produce preheated NH3 gas; (ii) introducing the preheated NH3 gas into an NH3 cracking device which is suitable for converting NH3 gas into a mixture of H2 and N2; (iii) converting the preheated NH3 gas into a mixture of H2 and N2 in the device; (iv) cooling the mixture of H2 and N2 to obtain a cooled H2 and N2 mixture; (v) introducing the cooled H2 and N2 mixture into a gas turbine; and (vi) combusting the cooled H2 and N2 mixture in the gas turbine to generate energy.
  • WO 2019/038251 A1 relates to a method for producing a product gas containing N2 and H2 from NH3, comprising the steps of non-catalytic partial oxidation of NH3 with an O2-containing gas to a process gas containing N2, water, amounts of nitrogen oxides and residual amounts of NH3; Cracking at least a portion of the residual amounts of NH3 to H2 and N2 in the process gas by contact with a nickel-containing catalyst and simultaneously reducing the amounts of nitrogen oxides to N2 and water by reaction with a portion of the H2 formed during the cracking of the process gas by contact of the process gas with the nickel-containing catalyst; and withdrawing the product gas containing H2 and N2.
  • WO 2012/039183 A1 relates to an NH 3 -Decomposition device that H 2 as a combustion improver, and a NH 3 -Oxidation device which converts part of the introduced NH 3 with O 2 using an oxidation catalyst, which causes combustion to produce the NH 3 - to provide the heat required for the decomposition reaction.
  • WO 2012/090739 A1 relates to a H 2 -Generator comprising a decomposition device which decomposes a compound containing an H atom and an N atom and produces H 2 generated; a compound supply device which supplies the compound to the decomposition device; and an O 2 -Feeding device which is connected to the decomposition device O 2 supplies.
  • WO 2020/095467 A relates to a device for generating H 2 -Gas comprising: a NH 3 - Evaporation device that produces liquid NH 3 heated to NH 3 -gas; a main thermal decomposition device which causes the combustion of a fuel gas, whereby the NH 3 -Evaporation device produced NH 3 -Gas heated and converted into N 2 -Gas and H 2 gas is decomposed; a cooler which cools a gas produced by the decomposition, which contains the N2 gas and the H2 gas produced by the decomposition by the main thermal decomposition device; and a separator which separates the H 2 -gas from the cooled gas produced by the decomposition.
  • WO 2021/257944 A1 relates to the recovery of H 2 from a NH 3 -Cracking process in which the cracked gas is purified in a PSA device.
  • the use of a membrane separator for the PSA exhaust gas improves recovery.
  • WO 2022/096529 A1 relates to a process for cracking NH3, producing H2 and generating electric power, comprising electrolysis of water in supplied NH3, evaporation, preheating and cracking NH3 using NH3 synthesis catalysts at low temperatures.
  • WO 2022/243410 A1 relates to a process for synthesizing H2 via the catalytic cracking of NH3; wherein an NH3-containing stream is subjected to a catalytic cracking step in the presence of heat to obtain a combusted gas and a thermally cracked stream containing N2, H2 and possibly residual NH3 and optionally water; wherein the thermally cracked stream is subjected to a H2 recovery step to obtain a high purity H2 stream.
  • WO 2022/265647 A1 relates to the recovery of a renewable H2 product from an NH3 cracking process in which the cracked gas is purified in a first PSA device and at least a portion of the first PSA tail gas is recycled as fuel to reduce the carbon intensity of the renewable H2 product.
  • WO 2022/265648 A1 relates to the removal of ⁇ X contaminants by selective catalytic reduction (SCR) from a flue gas produced in an NH3 cracking process using an aqueous NH3 solution produced by cooling the compressed exhaust gas from an H2 PSA device to purify the cracked gas.
  • SCR selective catalytic reduction
  • WO 2022/265649 A1 relates to the reduction of the water content of the NH3 used in an NH3 cracking process, which enables the use of water-incompatible cracking catalysts. The water removal process can also be used to recover and recycle NH3 from the cracking gas.
  • WO 2022/265650 A1 relates to an NH 3 -Fission process in which fission gas is cleaned in a PSA system. Remaining NH 3 in a first fission gas is further H 2 and N 2 converted by feeding PSA residual gas or a gas derived from it to a secondary fission reactor and further processing a second fission gas.
  • WO 2022/265651 A1 relates to a process in which residual NH 3 in a H 2 -PSA system with a non-zeolitic adsorbent such as activated carbon, activated alumina or silica gel made of NH 3 - cracked gas is removed.
  • a non-zeolitic adsorbent such as activated carbon, activated alumina or silica gel made of NH 3 - cracked gas is removed.
  • US 2003/0143142 A1 and US 2017/0334722 A1 describe processes for reducing NO X -Concentration and N 2 O concentration of the residual gas from nitric acid production.
  • CN 114412668 A relates to ammonia fuel engines, in particular to an ammonia-hydrogen fusion type hybrid energy system and an engine.
  • JP 2023026798A published on March 1, 2023, relates to an exhaust gas processing system of an ammonia engine comprising, as a first catalyst, an oxidation catalyst comprising a catalyst layer containing Pt and zeolite, and, as a second catalyst, a denitration catalyst comprising a catalyst layer containing zeolite ion-exchanged with Cu, Co or Fe ions.
  • Y.K. Park, Chemical Engineering Journal, Volume 461, 141958, published on April 1, 2023 is a review of the catalytic removal of nitrogen oxides (NO, NO2, N2O) from exhaust gas produced when ammonia is used as fuel.
  • NO, NO2, N2O nitrogen oxides
  • KR 2023095308 A published on June 29, 2023, relates to a system with a catalytic reactor; a storage tank for liquid ammonia; a first distributor for supplying at least a portion of the ammonia supplied from the storage tank to a catalytic reactor as decomposition ammonia; wherein the ammonia supplied to the catalytic reactor is brought into contact with an ammonia cracking catalyst to generate nitrogen and hydrogen.
  • a second distributor feeds remaining ammonia that has passed through the first distributor to a denitrification reactor and a mixer.
  • NH3 has a comparatively low calorific value and a low flame propagation rate and carries the risk of flame extinction, resulting in incomplete combustion.
  • Cyanides can be formed and separated using alkaline washes, but these must then be disposed of as highly toxic compounds.
  • HCN can be converted to CO2, H2O, N2 and various nitrogen oxides.
  • the resulting nitrogen oxides must be broken down in a further process step, e.g. using SCR. Passing over special catalysts, e.g. based on TiO2, to hydrolyze the HCN according to HCN + H2O CO + NH3 is described. In this case, too, subsequent oxidation using appropriate separate oxidation catalysts is necessary.
  • ammonia slip catalysts were developed, which are usually based on precious metals from the platinum group (i.e. Ru, Rh, Pd, Os, Ir, Pt). Such catalysts are not only cost-intensive, but also not very selective (i.e. they form NH 3 if applicable NO X or N 2 O) and susceptible to chlorine and chlorine compounds. [0037] There is therefore a need for measures that are suitable for - nitrogen oxides (especially N 2 O and NE X (i.e.
  • the combustion plants comprise a combustion device in which NH 3 is burned to produce combustion heat, and a NH 3 -Decomposition device, which is in heat exchange with the combustion device and in which NH 3 catalytic in N 2 and H 2 is decomposed.
  • NH3 is preferably only oxidized to the N2 stage, for which no catalysts are usually necessary and this conversion usually takes place at atmospheric pressure.
  • Typical water contents in the exhaust gas are well above 3 vol.%.
  • the combustion of pure NH3 in air with a residual oxygen content of 3 mol.% produces more than 28 mol.% water.
  • the main aim of the combustion of NH3 is to generate the energy required for the catalytic decomposition reaction of NH3 into N2 and H2.
  • Low levels of nitrogen oxides in the exhaust gases formed during combustion are advantageous because only a relatively small exhaust gas treatment plant is then required to reduce the nitrogen oxide content in the flue gas and thus meet the official requirements with regard to permissible emissions, or because only then can sufficiently low residual concentrations be achieved using known methods for reducing nitrogen oxides.
  • the high water content leads to a progressive deactivation of the catalysts due to the hydrothermal loading of the catalysts in the exhaust gas treatment system, especially in the case of zeolite material, at the same time as high temperatures.
  • the maximum temperature should therefore be limited.
  • the chemical reduction of NOX is hardly affected by the high water content, while the breakdown of N2O by decomposition and/or chemical reduction is significantly affected by the high water content.
  • Another difference between the exhaust gases to be treated according to the invention compared to the production of HNO3 is the relatively high NOX content, which can amount to several thousand ppmv.
  • the NOX content depends on the conditions of combustion of NH3, in particular the NH3 content, any other combustible gases present (H2 and/or CH4 (natural gas)) and the air ratio ⁇ . Due to the high temperatures during combustion of up to 1000°C and more, the NOX is initially present almost exclusively as NO, i.e. with a very high proportion of NO and a very low proportion of NO2. Due to the preferential cooling in the downstream heat exchanger, only a small proportion of the NO is converted into NO2 due to the slow formation kinetics of NO2 at high temperatures. This means that the degree of oxidation ( ⁇ ) of the NOX, i.e.
  • the degree of NOX oxidation of residual gases in the HNO3 production before entering the corresponding exhaust gas treatment plant is typically between 30 and 70 vol.%, i.e. close to the ideal stoichiometric ratio for NO X -reduction according to the very fast SCR.
  • the high NO X content, combined with a very low NO X -Oxidation level and high water content at the same time as low operating pressure (close to atmospheric pressure) poses particular challenges to the effectiveness of the exhaust gas treatment system according to the invention in the present case. Added to this is the challenge or necessity of eliminating the Exhaust gas contains N 2 O, which can be produced using conventional SCR processes based on V 2 O 5 /TiO 2 -catalysts is not reducible.
  • the exhaust gas often has, at a comparatively high pressure, - a comparatively low content of NOX; - a comparatively high proportion of NO2; - a comparatively high content of N2O; - a comparatively low content of water; and - no proportion of unburned NH3 (NH3 slip).
  • the exhaust gas often has, at a comparatively low pressure, - a comparatively high content of NOX; - a comparatively low proportion of NO2; - a comparatively low content of N2O; - a significantly higher content of water; - possibly a not insignificant proportion of unburned NH3 (NH3 slip); and - possibly a non-negligible proportion of HCN, if NH3 is burned together with CH4 (natural gas); [0050]
  • NOX and N2O preferably comprising combustion devices and NH3 decomposition devices for splitting NH3 into N2 and H2
  • NOX i.e. NO and NO2
  • N2O NH3 operated combustion plants
  • NH 3 operated combustion plants preferably comprising a combustion device for burning NH 3 and a NH 3 -Decomposition device for splitting NH 3 in N 2 and H 2
  • a first aspect of the invention relates to a method for reducing the content of NO X and N 2 O in the exhaust gas of a NH 3 operated combustion plant, preferably comprising a combustion device for burning NH 3 and a NH 3 -Decomposition device for splitting NH 3 in N 2 and H 2 , the method comprising the following steps: (a) Burning of NH 3 (possibly in a mixture with one or more other flammable gases, such as H 2 , CH 4 , etc.) for operating the combustion plant, preferably comprising a combustion device for burning NH 3 (preferably comprising at least one burner and a combustion chamber) and a NH 3 -Decomposition device for splitting NH 3 in N 2 and H 2 , producing an exhaust gas which comprises N2, H2O, NOX and N2O and possibly HCN and which the combustion plant, preferably comprising a combustion device for burning NH 3 and a NH 3 -Decomposition device for splitting NH 3 in N 2 and H 2 , leaves;
  • the invention relates to a method for reducing the content of NOX and N2O in the exhaust gas of a combustion plant operated with NH3 and H2, preferably comprising a combustion device for burning NH3 and an NH3 decomposition device for splitting NH3 into N2 and H2, wherein the method comprises the following steps: (a) burning NH3 and H2 to operate the combustion plant, preferably comprising a combustion device for burning NH3 (preferably comprising at least one burner and a combustion chamber) and an NH3 decomposition device for splitting NH3 into N2 and H 2 , producing an exhaust gas which contains N 2 , H 2 O, NO X and N 2 O and which comprises the combustion plant, preferably comprising a combustion device for burning NH 3 and a NH 3 -Decomposition device for splitting NH 3 in N 2
  • the content of NO X in the flue gas can be used advantageously.
  • a considerable amount of heat is generated during the chemical reduction of NOX with a reducing agent, preferably with NH3, which can be transferred to a suitable heat transfer medium with the help of one or more heat exchangers.
  • the heat transfer medium used is preferably water or steam, which has advantages in terms of safety, among other things.
  • the heat absorbed by the heat transfer medium is then preferably used to heat NH3, which is fed as a feed stream to the NH3 decomposition device. Alternatively or additionally, the heat can also be used to preheat combustion air.
  • this aspect relates to a process for producing H 2 by catalytic decomposition of NH 3 comprising the method according to the invention for reducing the content of NO X and N 2 O in the exhaust gas of a NH 3 and H 2 operated combustion plant, preferably comprising a combustion device for burning NH 3 and a NH 3 -Decomposition device for splitting NH 3 in N 2 and H 2 .
  • the exhaust gas treatment system according to the invention comprises at least - an N 2 O reduction catalyst and/or a N 2 O decomposition catalyst; and - a NO X -reduction catalyst; which can be the same or different depending on the given functionality or multiple functionality and can be present in common or separate reaction zones (catalyst beds).
  • the exhaust gas treatment system according to the invention comprises - an N2O reduction catalyst; - an N 2 O decomposition catalyst; and - a NO X -reduction catalyst; which can be the same or different depending on the given functionality or multiple functionality and can be present in common or separate reaction zones (catalyst beds).
  • the exhaust gas treatment system according to the invention additionally comprises at least one further catalyst or one of the above-mentioned N2O reduction, N2O decomposition or NOX reduction catalysts fulfills at least one further functionality selected from - NH3 oxidation catalyst; - HCN degradation catalyst; and - CO oxidation catalyst.
  • the NH3 oxidation catalyst is preferably used when the proportion of unburned NH3 in the exhaust gas (NH3 slip) is greater than the need for NH3 as a reducing agent for NOX and/or N2O in the exhaust gas treatment system, so that after passing through steps (d1) and/or (d2) and (e), the exhaust gas still contains residual amounts of NH3 which should not or must not be released into the environment. These residual amounts of NH3 can then be broken down with the help of the downstream NH3 oxidation catalyst by oxidation of NH3.
  • the HCN degradation catalyst is preferably used when the fuel contains hydrocarbons (CH4, natural gas, etc.) in addition to NH3 and the exhaust gas formed during combustion contains certain amounts of HCN.
  • the resulting HCN can then be degraded using the HCN degradation catalyst by hydrolysis of the HCN and oxidation of the hydrolysis products (hydrolysates) formed, i.e. NH 3 and CO, with NO preferably contained in the exhaust gas X and N 2 O are broken down (removed).
  • hydrolysis products hydrolysis products formed, i.e. NH 3 and CO
  • NO preferably contained in the exhaust gas X and N 2 O are broken down (removed).
  • HCN in water-containing exhaust gases which simultaneously contain NOX and N2O in a molar amount that is greater than or equal to the molar amount of HCN, can be converted to N by passing the exhaust gas over a zeolitic catalyst loaded with transition metals, e.g.
  • a pack of catalyst pellets containing an iron-loaded zeolitic material of the BEA structure type, at temperatures of 300 to 600°C (preferably 350 to 550°C). 2 , H 2 O and CO 2 can be dismantled.
  • this method can achieve complete removal of HCN, i.e. conversion into non-toxic substances, in a single-stage process, i.e. in one process step without the use of expensive precious metal catalysts.
  • NO X and N 2 O containing exhaust gas additionally NH 3 for NOX and N2O reduction and, if necessary, CO or hydrocarbons such as CH4 or propane for N2O reduction.
  • the amount of reducing agent in this case is based on the molar input amounts of N 2 O and NE X , each reduced by the molar amount of HCN contained in the exhaust gas. If excess amounts of N 2 O in the exhaust gas, which reacts with NH 3 or CO or hydrocarbons are to be reduced, the NO X -content using NH 3 in any case to zero (or close to zero). If CO or hydrocarbons are used as additional reducing agents, an additional CO oxidation catalyst can be used downstream of the zeolite catalyst to eliminate any CO emissions.
  • the CO oxidation catalyst is preferably used when (i) hydrocarbons (CH4, natural gas, etc.) are used as reducing agents for N2O; and/or (ii) an HCN degradation catalyst is used to degrade HCN, the degradation products of which contain CO.
  • the CO that may be produced in this case can then be broken down to CO2 by oxidation using the downstream CO oxidation catalyst.
  • the exhaust gas treatment system according to the invention comprises an NH3 oxidation catalyst, it may be preferred according to the invention to first cool the exhaust gas within the exhaust gas treatment system with a heat exchanger to a lower temperature than at the inlet to the exhaust gas treatment system, so that the NH3 oxidation catalyst can develop its effect in an optimized manner.
  • the exhaust gas treatment system according to the invention therefore additionally comprises one or more heat exchangers.
  • “and/or” means either “or” or “and”, so that, for example, "A and/or B” has the following three meanings: (i) only A but not B, (ii) only B but not A, and (iii) both A and B.
  • NOX includes nitrogen monoxide (NO) and nitrogen dioxide (NO2), but not nitrous oxide (N2O).
  • Catalysts accelerate certain chemical reactions by lowering their activation energies.
  • all data in ppm are based on volume, i.e.
  • Steps (b) and (f) of the process according to the invention are optional and preferred independently of one another.
  • Steps (a), optionally (b), and (c) of the process according to the invention are carried out one after the other in alphabetical order, followed by steps (d) and (e) in basically any order. Step (d) can therefore take place before step (e) or after step (e) or simultaneously with step (e). Mixed forms of partial simultaneity are also possible.
  • Steps (d1) and (d2) are considered separately for the purpose of description, but both serve the common purpose of reducing the N2O content in the exhaust gas.
  • Steps (d1), (d2) and (e) can also be carried out in any order, with mixed forms of partial simultaneity also being possible in this regard.
  • the process according to the invention comprises steps (a), optionally (b), (c), (d1), (e) and optionally (f); steps (a), optionally (b), (c), (d2), (e) and optionally (f); or steps (a), optionally (b), (c), (d1), (d2), (e) and optionally (f).
  • the exhaust gas passes through the steps of the process according to the invention in one of the following orders: (i) (a) ⁇ (c) ⁇ (d1) ⁇ (e); (ii) (a) ⁇ (c) ⁇ (e) ⁇ (d2); (iii) (a) ⁇ (c) ⁇ (e) ⁇ (d2) ⁇ (d1); (iv) (a) ⁇ (c) ⁇ (e) ⁇ (d1+d2); or (v) (a) ⁇ (c) ⁇ (e) ⁇ (d1).
  • the exhaust gas passes through the steps of the process according to the invention in one of the following orders: (vi) (a) ⁇ (b) ⁇ (c) ⁇ (d1) ⁇ (e); (vii) (a) ⁇ (b) ⁇ (c) ⁇ (e) ⁇ (d2); (viii) (a) ⁇ (b) ⁇ (c) ⁇ (e) ⁇ (d 2 ) ⁇ (d 1 ); (ix) (a) ⁇ (b) ⁇ (c) ⁇ (e) ⁇ (d1+d2); or (x) (a) ⁇ (b) ⁇ (c) ⁇ (e) ⁇ (d 1 ).
  • the exhaust gas passes through the steps of the method according to the invention in one of the following orders: (xi) (a) ⁇ (b) ⁇ (c) ⁇ (d 1 ) ⁇ (e) ⁇ (f); (xii) (a) ⁇ (b) ⁇ (c) ⁇ (e) ⁇ (d 2 ) ⁇ (f); (xiii) (a) ⁇ (b) ⁇ (c) ⁇ (e) ⁇ (d 2 ) ⁇ (d 1 ) ⁇ (f); (xiv) (a) ⁇ (b) ⁇ (c) ⁇ (e) ⁇ (d1+d2) ⁇ (f); or (xv) (a) ⁇ (b) ⁇ (c) ⁇ (e) ⁇ (d1) ⁇ (f).
  • step (d1+d2) means that both step (d 1 ) as well as step (d 2 ), whereby the execution of these two steps (d 1 ) and (d 2 ) takes place at least partly simultaneously, i.e. both steps take place in parallel. [0082] Further steps not expressly mentioned can take place between these steps.
  • NH3 reactant
  • NH3 decomposition device a downstream NH3 decomposition device
  • main reactor upstream NH3 decomposition device
  • intermediate product gas a partial catalytic decomposition of NH3, typically H2, N2 and comparatively large amounts of non-decomposed NH3
  • product gas obtained by the catalytic decomposition of NH3, typically H2, N2 and comparatively small amounts of non-decomposed NH3
  • the product gas is the gas mixture that leaves the last of the NH3 decomposition devices
  • step (a) of the process according to the invention the combustion of NH 3 for operating a combustion plant.
  • NH 3 burned, possibly in a mixture with other components (e.g. H 2 or CH 4 ).
  • the combustion plant comprises a combustion device in which NH 3 is burned to produce combustion heat, and a NH 3 -Decomposition device, which is in heat exchange with the combustion device and in which NH 3 catalytic in N 2 and H 2 is decomposed.
  • combustion plants in the sense of the invention generate heat through combustion processes.
  • the combustion plants preferably comprise a combustion device for burning NH3 and an NH3 decomposition device for splitting NH3 into N2 and H2. Heat is generated by burning combustion gases.
  • Combustion plants or the “combustion devices” included therein in the sense of the invention are any plants in which NH3 or a fuel containing NH3 is oxidized with O2 (preferably from combustion air) with the aim of generating N2 and H2O in particular as the main products.
  • Plants in which NH3 is oxidized with O2 with the aim of producing nitrogen compounds with high oxidation numbers (e.g. NOX) as the main products, as is the case, for example, in the production of nitric acid, are neither combustion plants nor combustion devices within the meaning of the invention. Catalysts are usually required to produce such nitrogen compounds with high oxidation numbers as the main products.
  • the combustion plant according to the invention is preferably not equipped with a catalyst, i.e. the combustion of NH3 and H2 according to the invention is preferably not catalyzed.
  • the combustion of NH3 means the oxidation of NH3 with O2, whereby this conversion does not have to be complete according to the invention, so that the exhaust gas can contain residual, unburned (unoxidized, unconverted) NH3 (NH3 slip, NH3 breakthrough).
  • NH3 slip, NH3 breakthrough residual, unburned (unoxidized, unconverted) NH3
  • CH4 natural gas
  • the O2 used for combustion can be used in the form of combustion air, whereby the combustion air may be mixed with O 2 may be enriched.
  • step (a) of the process according to the invention the combustion of NH 3 in a combustion plant which has a combustion device for burning NH 3 and a NH 3 -Decomposition device for splitting NH 3 in N 2 and H 2
  • the combustion of NH 3 in the combustion facility serves to heat the NH 3 -Decomposition device, preferably a reactor filled with catalyst, for cracking NH 3 in N 2 and H 2 .
  • the splitting of NH 3 in N 2 and H 2 According to the invention, this occurs as a catalytic decomposition of NH 3 at a NH 3 -decomposition catalyst.
  • the catalytic decomposition of NH 3 the formation of N 2 and H 2 , sometimes referred to in the art as "cleavage” or “cracking".
  • the terms “catalytic decomposition”, “decomposition”, “catalytic cleavage”, “cleavage”, “catalytic cracking” and “cracking” of NH 3 are used as interchangeable synonyms for the purpose of description.
  • the catalytic decomposition of NH 3 is preferably carried out in the absence of O 2
  • the combustion system according to the invention preferably comprises a combustion device and an NH3 decomposition device, which are in heat exchange with one another.
  • a combustion gas which contains NH3 and preferably H2 is burned together with combustion air, which contains O2, to generate combustion heat.
  • the combustion heat generated in this way is at least partially supplied as a heat flow to the NH3 decomposition device (or transferred to the NH3 decomposition device) in order to supply the heat required for the endothermic catalytic decomposition of NH3 to H2 and N2.
  • the combustion heat is preferably used according to the invention to preheat the NH3 to be decomposed, the combustion gas and the combustion air to an elevated temperature.
  • the NH3 decomposition device is preferably a tube reactor which is designed analogously to a primary reformer for producing synthesis gas or hydrogen from natural gas.
  • the basic design of such a fired tube reactor which is designed analogously to a primary reformer, includes one or more tubes containing the NH3 decomposition catalyst, which are arranged in a combustion chamber, into which flames from burners protrude and in which the radiant heat and convection heat of the flames and the hot exhaust gas cause heat transfer to the NH3 (process gas) flowing through the NH3 decomposition catalyst.
  • the combustion device thus preferably comprises a combustion chamber and one or more burners, preferably several burners.
  • the NH3 decomposition device (parallel arranged tubes) is then located within the combustion device (combustion chamber, combustion chamber).
  • the exhaust gas is discharged from the combustion device by means of an imposed pressure gradient, for example by using compressors in the supply of combustion air or the discharge of the exhaust gas.
  • the exhaust gas In order to ensure a uniform energy input over the length of the NH 3 -decomposition catalyst bed inside the tubes, the exhaust gas must also be 3 -decomposition catalyst bed, i.e. at the end of the pipes, still have a sufficiently high temperature that allows a significant release of radiant heat.
  • the exhaust gas leaves the combustion device (combustion chamber, combustion chamber) therefore with high temperatures, which in the case of a tube reactor designed analogously to a primary reformer can be over 1000°C.
  • the proportion of the energy used in the endothermic catalytic decomposition of NH 3 accounts for about 40-60% of the total energy generated by the combustion of the combustion gas. The remaining heat can be used for other purposes.
  • the exhaust gas is preferably passed through an exhaust duct, which preferably fulfills three essential tasks: 1.
  • step (a) of the method according to the invention i.e.
  • the combustion of NH3 and preferably H2 to operate the combustion plant to produce an exhaust gas which leaves the combustion plant comprises the following sub-steps: (a1) optionally and preferably heating and evaporating (liquid) NH3; (a2) optionally and preferably heating combustion air (preferably comprising N2 and O2); (a3) burning combustion gas (comprising NH3 and preferably H2) and combustion air (comprising O2) in a combustion plant, preferably a combustion device, whereby an exhaust gas (comprising N2, H2O, NOX and N2O) is generated and combustion heat is released, whereby at least part of the combustion heat flows into an NH3 decomposition device; and (a 4 ) catalytic decomposition of NH 3 in the NH 3 -Decomposition device on a NH 3 -decomposition catalyst, whereby combustion heat from sub-step (a 3 ) and a product gas is produced (comprising H 2 and N 2 ).
  • combustion of combustion gas and combustion air [0095]
  • the combustion of NH 3 as the sole fuel i.e. it is used alongside the NH 3
  • no further gas is burned.
  • NH 3 in a mixture with H 2 i.e. it is used alongside the NH 3
  • the combustion of NH 3 in a mixture with CH 4 (natural gas) are also referred to as "combustion gas" for the purpose of description.
  • the combustion gas may contain other components, e.g. N 2
  • heat is provided by combustion of a combustion gas in a combustion system, preferably in a combustion device.
  • the combustion device preferably has one or more burners for this purpose, preferably at least two burners, more preferably at least three burners.
  • the combustion gas contains a mixture of H2 and NH3, among other things because this mixture produces a medium flame temperature and has better combustion properties than pure NH3.
  • the content of nitrogen oxides can also be influenced by a suitable mixing ratio of H2 and NH3.
  • the combustion of NH3, i.e. the oxidation of NH3 with O2 (or the mixture of NH3 with another combustible gas, such as H2, CH4, etc.) does not take place on a catalyst, i.e. the combustion is not carried out in the presence of a heterogeneous catalyst.
  • the H2 which is present in the combustion gas in a mixture with the NH3 to be burned is formed by thermal and/or catalytic decomposition of NH3 (sub-step (a4)).
  • the integrated combustion of NH3 with O2 preferably provides the energy for the catalytic decomposition (cracking).
  • the combustion of NH3 is integrated into a process for the thermal and/or catalytic decomposition of NH3 into N2 and H2.
  • the composition of the exhaust gas formed during combustion depends on the combustion gas used. In preferred embodiments, sufficient H2 is added to NH3 to change the combustion properties of the combustion gas such that a largely quantitative conversion is achieved during combustion.
  • the combustion gas used is a mixture of the effluent of a separation unit for purifying the H2, preferably from the off-gas of a pressure swing adsorption device or the retentate of a membrane unit, preferably a pressure swing adsorption device, and a portion of the NH 3 or the H produced as a product 2 [0101] If the catalytic decomposition of NH3 is incomplete, the product gas (i.e. the product of the catalytic decomposition) contains N 2 and H 2 additional remaining, unreacted NH 3 .
  • the preferred option is H 2 , which is present in the combustion gas in the mixture with the NH to be burned.
  • the separation efficiency of the device for the purification of H 2 about how much H 2 in the off-gas of the pressure swing adsorption device or in the retentate of the membrane unit and therefore also has an influence on the composition of the exhaust gas formed from it during combustion.
  • the quantitative separation of the total amount of H2 is not technically possible or not economical, which is why the separated gas mixture (off-gas of the pressure swing adsorption) often contains a certain amount of H2.
  • a mixture of NH3 and H2 is obtained, which can either be burned directly as such or first enriched with further NH3 (or H2).
  • This gas mixture separated from the product gas by pressure swing adsorption is therefore preferably used as combustion gas according to the invention.
  • the separated gas mixture can be used as such as combustion gas, unchanged, or an appropriate amount of NH3 or H2 is added to set the desired ratio of NH3 to H2. If the catalytic decomposition is complete or almost complete, the NH3 content in the separated gas mixture (off-gas of the pressure swing adsorption) may still be too low and the required amount of NH3 must still be added.
  • the exact composition of the exhaust gas formed during combustion of the combustion gas depends on the composition of the combustion gas and the combustion air. An important parameter in describing the combustion properties of the combustion gas, the emission of pollutants and the composition of the exhaust gas is the mixing ratio of NH3 to H2.
  • the inventive process #5 has a significantly flatter temperature profile in the exhaust duct than the other process regimes and can therefore include more heat integration steps, including those that are possible at low flue gas temperatures. As process instructions #5 to #7 illustrate, this enables (almost) complete energy integration.
  • the temperature profile in the exhaust duct would have to be significantly steeper because a small volume of exhaust gas is available. Since the heat exchangers in the exhaust duct require a minimum temperature difference in order to be designed economically, with steep temperature profiles the risk of leaving residual heat that cannot be transferred unused due to the required temperature difference is significantly greater. In any case, the exhaust gas entering the exhaust duct is significantly hotter in these cases and requires the use of more complex materials.
  • the combustion gas contains a mixture ratio of NH 3 and H 2 which is optimized with regard to the subsequent combustion.
  • the proportion of H 2 at most 80 mol%, more preferably at most 70 mol%, even more preferably at most 60 mol%, most preferably at most 50 mol%, and in particular at most 40 mol%.
  • the proportion of H2 is at most 30 mol%, more preferably at most 20 mol%, even more preferably at most 15 mol%, most preferably at most 10 mol%, and in particular at most 5 mol%.
  • the proportion of H is 2 at least 1 mol%, more preferably at least 2 mol%, even more preferably at least 3 mol%, most preferably at least 4 mol%, and in particular at least 5 mol%.
  • the proportion of H2 is preferably at least 10 mol%, more preferably at least 20 mol%, even more preferably at least 30 mol%, most preferably at least 40 mol%, and in particular at least 50 mol%.
  • the molar ratio of H2:NH3 in the mixture is in the range from 45:55 to 90:10, preferably 50:50 to 85:15, more preferably 55:45 to 80:20, even more preferably 60:40 to 75:25, most preferably 65:35 to 70:30 or 70:30 to 75:25. Since according to the invention the separated gas mixture of a gas exchange adsorption system is preferably used as the combustion gas, the molar ratio of H2:NH3 depends mainly on its hydrogen yield and can be about 15:1 in extreme cases.
  • the air ratio ⁇ for the combustion is preferably in the range from 0.9 to 1.7, more preferably 1.0 to 1.6, even more preferably 1.1 to 1.5, most preferably 1.2 to 1.4. Another very preferred range of the air ratio ⁇ is between 1.0 and 1.2. [0113] In particularly preferred embodiments, the air ratio is in the range of 1.06 ⁇ 0.06, preferably 1.06 ⁇ 0.05, more preferably 1.06 ⁇ 0.04, even more preferably 1.06 ⁇ 0.03, most preferably 1.06 ⁇ 0.02, and in particular 1.06 ⁇ 0.01. [0114] The air ratio ⁇ (i.e.
  • the combustion air ratio indicates the mass ratio of combustion air to combustion gas relative to the stoichiometrically ideal ratio for a theoretically complete combustion process. It is defined as the ratio of air to fuel which contains a sufficient mass of oxygen to achieve complete combustion of a given mass of fuel (see e.g. K. Soman, Thermal Engineering, PHI, 2011, page 224, no. 5.4.2). In principle, the ratio can be expressed in terms of mass or amount of substance (see e.g. P. Majumdar, Design of Thermal Energy Systems, Wiley 2021, page 66, no. 2.13.5.2). For the purpose of description, the ratio is mass-related. If not air but another oxygen-containing gas is used for a combustion process, "air” is strictly speaking to be replaced by "oxygen carrier".
  • the parameter ⁇ is still used in the above definition.
  • the equivalence ratio NH 3 /H 2 ( ⁇ ) (not to be confused with the reciprocal of the air ratio 1/ ⁇ ) in the range from 0.55 to 1.40, preferably 1.05 to 1.20.
  • the formation of nitrogen oxides depends, among other things, on the content of residual oxygen in the exhaust gas, which can be, for example, 3 mol% or 1 mol%. In order to achieve a residual oxygen content of 1 mol%, for example, an air ratio of approximately 1.1 is required.
  • the concentration of nitrogen oxides (in particular NO, NO 2 and N 2 O) and the dew points of condensable components are two parameters that are of great importance for the technical design and equipment of the exhaust gas duct. These parameters are also largely determined by the composition of the exhaust gas.
  • Nitrogen oxides in particular NO, NO2 and N2O are produced in combustion reactions by various mechanisms.
  • thermal nitrogen oxides In tubular reactors, which are designed analogously to a primary reformer, only so-called “thermal nitrogen oxides” are produced with a combustion gas that does not contain NH3, namely by recombination of nitrogen radicals with oxygen, the formation of which is preferred at high temperatures.
  • a combustion gas that contains NH3 nitrogen oxides can form via various reaction paths in the complex kinetics of the combustion of NH3, so-called “kinetic nitrogen oxides”.
  • kinetic nitrogen oxides In plants for the production of H2 from NH3, both thermal nitrogen oxides and kinetic nitrogen oxides can be formed. The presence of H2 in the combustion gas increases the flame temperature, and the addition of NH3 increases the tendency to form kinetic nitrogen oxides.
  • An example of an exhaust gas with a comparatively low content of nitrogen oxides contains 500 ppmv NO, 10 ppmv NO2 and 10 ppmv N2O (case A).
  • An example of an exhaust gas with a comparatively high content of nitrogen oxides contains 5000 ppmv NO, 10 ppmv NO2 and 50 ppmv N2O (case B).
  • the dew point of H 2 O depends on the partial pressure of H2O in the exhaust gas.
  • the exhaust gas contains mainly N2 and only a comparatively small amount of H2O, which generally leads to rather low dew points.
  • the rotor can be damaged.
  • the condensation of liquid H 2 O is therefore not desired.
  • a distance of 25 K between the minimum exhaust gas temperature and the dew point should be maintained in the exhaust gas duct.
  • the exhaust gas is therefore preferably not cooled below approx. 81-88°C in the exhaust gas duct, depending on the respective conditions. This temperature is therefore the technically achievable minimum, and the internal energy of the exhaust gas cannot be used any further. This is therefore an unavoidable energy loss.
  • the dew point of NH 4 NO 3 is relevant because systems for removing nitrogen oxides from exhaust gases (exhaust gas treatment systems) can have a slip of nitrogen oxides that have not been completely broken down, usually NO.
  • the NH3 added to the exhaust gas treatment system as a reducing agent is often not fully converted either, so that small amounts of NO and NH3 slip through. Cooling the exhaust gas in the exhaust duct can cause the dew point of NH4NO3 to fall below, which can precipitate on the pipes of a heat exchanger. can. This precipitation poses a risk to the safe operation of the system as it is sensitive to impact and can react explosively.
  • the table shows the dew points of NH 4 NO 3 at different typical residual contents of NO and NH 3 in the exhaust gas: Pressure [bar a] 1.00 1.00 1.00 1.00 residual NH3 [ppmv v] 10 10 50 10 residual NOX [ppmv v] 10 10 10 50 NO ratio 2 /NO 1 9 1 1
  • the critical temperature for the precipitation of NH 4 NO 3 To achieve this, the gas flow does not necessarily have to reach or fall below this temperature, even the wall temperature of the tube of a heat exchanger can be sufficient and lead to the precipitation of NH 4 NO 3 Since the combustion system requires combustion air, which is usually drawn in at ambient temperature, there is a risk of NH precipitating on the pipes of a heat exchanger for preheating combustion air under normal operating conditions.
  • the device for removing nitrogen oxides is operated according to the invention in such a way that the slip is either from NO X or NH 3 , or ideally both, is reduced to a maximum of 1 ppmv.
  • This can be achieved according to the invention by suitable reaction control during the chemical reduction of NOX with NH3, and preferably with a reactor for the post-oxidation of NH3 with residual oxygen from the exhaust gas.
  • Catalytic decomposition of NH 3 in H 2 and N 2 [0128]
  • the catalytic decomposition of NH3 basically takes place thermally, but is accelerated by the use of an NH3 decomposition catalyst.
  • the catalytic decomposition of NH3 can be carried out under various conditions using various NH3 decomposition catalysts and with various connections with different reactor types.
  • the catalytic decomposition of NH3 preferably takes place by supplying heat in the presence of an NH3 decomposition catalyst.
  • Important parameters for the catalytic decomposition of NH3 are the type of NH3 decomposition catalyst, the reaction temperature and the reaction pressure.
  • NH3 decomposition catalyst various materials can be considered as NH3 decomposition catalyst.
  • the reaction temperature at which the catalytic decomposition of NH3 takes place is determined in particular by the choice of the NH3 decomposition catalyst.
  • Suitable processes for the thermal and/or catalytic decomposition of NH3 into N2 and H2 are known to a person skilled in the art.
  • Suitable catalysts for the catalytic decomposition of NH3 into N2 and H2 are, for example, Ru supported on Al2O3 or SiO2, Fe, Co, Ni supported on MgAl2O4, Cu or Ru, or Co 3 Mon 3 N (A. Boisen et al., Journal of Catalysis 230 (2005) 309-312; I.
  • a nickel-based NH 3 -decomposition catalyst is used.
  • the reaction temperature and the reaction pressure determine the equilibrium conversion. At 900°C and 20 bar pressure, the decomposition of NH 3 almost quantitatively. At 650°C the conversion of NH 3 about 98.5%, at 500°C only about 95%.
  • reaction temperatures are set in the range from about 550°C to about 900°C, preferably about 550°C to about 700°C, so that a high conversion is achieved.
  • reaction temperatures are set in the range from about 600°C to about 900°C, preferably about 600°C to about 700°C, so that a high conversion is achieved.
  • optimal reaction temperatures are in the range from about 630°C to 640°C. Nickel-based NH3 decomposition catalysts are advantageous despite the comparatively high reaction temperature.
  • the NH3 decomposition catalyst preferably comprises supported nickel.
  • Preferred carrier materials are selected from the group consisting of Al2O3, MgO, SiO2, mesoporous SiO2 (e.g. MCF-17, MCM-41, SBA-15), zeolite (e.g.
  • a ruthenium-based NH3 decomposition catalyst is used.
  • reaction temperatures in the range from about 450°C to about 500°C are preferably set according to the invention, although somewhat lower conversions of, for example, about 95% can be achieved, so that the remaining residual content of undecomposed NH3 in the product gas is greater.
  • other NH 3 -decomposition catalysts can be used at even lower reaction temperatures. The lower the reaction temperature, the lower the conversion and the more non-decomposed NH 3 must be separated from the product gas and returned.
  • the reaction pressure is preferably about 15 bar a to about 25 bar a.
  • reaction pressure is particularly predetermined by the design of the purification of H2.
  • the pressure swing absorption (PSA) preferred according to the invention for the purification of H2 can preferably be operated effectively at a pressure in the range of about 15 bar to about 25 bar.
  • the pressure of the product gas when leaving the NH3 decomposition device is in the range from about 15 to about 25 bar a, more preferably about 18 bar a to about 22 bar a, even more preferably about 19 bar a to about 21 bar a. In this way, a good balance is found between the requirements of pressure swing adsorption on the one hand and the conversion achieved on the other.
  • the catalytic decomposition of NH3 can in principle take place in different types of reactor.
  • adiabatic reaction the internal heat of the reaction gas is used as an energy source for the reaction.
  • Suitable reactors for this are autothermal reformers and secondary reformers, which work with internal energy generation. Combustion air is added to the process gas and part of the reaction gas is burned in order to increase the temperature so that the desired temperature prevails at the reactor outlet.
  • a disadvantage is the presence of water in the process gas that is produced during combustion and has to be removed by condensation. A portion of the non-decomposed NH3 then dissolves in the condensed water and is lost. In addition, the high temperatures lead to the formation of considerable amounts of nitrogen oxides. [0143] According to the invention, these disadvantages are avoided by the product gas preferably being physically separated from the combustion gas and the exhaust gas formed therefrom.
  • the product gas is in the NH3 according to the invention 3 -Decomposition device of the combustion plant by decomposition of NH 3 formed and leaves the NH 3 -Decomposition device preferably via its own outlet.
  • the combustion gas is burned together with combustion air in the combustion device of the combustion plant and the exhaust gas formed thereby preferably also leaves the combustion device via its own outlet, preferably into an exhaust duct.
  • Product gas and exhaust gas are preferably not mixed with each other, but remain physically separated from each other.
  • the catalytic decomposition of NH3 takes place in a reactor analogous to a primary reformer.
  • the reactor comprises both the NH3 decomposition device according to the invention and the combustion device according to the invention.
  • the NH 3 -decomposition catalyst is preferably present in at least one of NH 3 through which the NH3 flows, more preferably at least two tubes, even more preferably at least three tubes.
  • the at least one tube contains the NH3 decomposition catalyst.
  • the at least one tube is preferably flowed through from top to bottom with NH3.
  • a mixture of NH3 and H2 is preferably burned together with combustion air as combustion gas (combustion device).
  • the N2 formed alongside H2 during the catalytic decomposition of NH3 is inert and serves as an additional heat carrier.
  • NH3 is preheated before entering the NH3 decomposition device according to the invention. Due to this preheating, the temperature of the NH3 before entering the NH3 decomposition device according to the invention is preferably at least about 600°C, preferably at least about 630°C. The temperature of the NH3 is preferably at most about 850°C, more preferably at most about 820°C.
  • the temperature of the NH3 when entering the NH3 decomposition device according to the invention is particularly preferably about 780°C to 820°C, preferably about 800°C.
  • the NH3 decomposition device according to the invention and the combustion device according to the invention preferably form a reactor designed analogously to a primary reformer.
  • the NH is preferably 3 -Decomposition catalyst nickel-based.
  • the reaction temperature in the NH 3 -decomposition device, preferably in the at least one tube, which the NH 3 -decomposition catalyst and through which the NH 3 is passed preferably about 630°C to about 670°C, preferably about 650°C.
  • this temperature is about 660°C to 700°C, preferably about 680°C.
  • the product gas leaves the reactor (the NH 3 -decomposition device) preferably at a pressure of about 15 bar a to about 25 bar a, preferably about 20 bar a.
  • the decomposition of NH 3 two-stage in two successively flowing NH 3 -decomposition facilities. In a pre-reactor (first NH 3 -decomposition device) initially only a part of the NH 3 The remaining decomposition of NH 3 up to the maximum conversion achieved then takes place in a second NH3 decomposition device.
  • the second NH3 decomposition device together with the combustion device according to the invention forms a reactor as described in more detail above, designed analogously to a primary reformer.
  • the NH 3 before introduction into the pre-reactor (first NH 3 -decomposition device) Preferably, the temperature of the NH3 after heating and upon entry into the pre-reactor (first NH3 decomposition device) is about 620°C to about 680°C, more preferably about 650°C.
  • the preheated NH3 then enters the pre-reactor, which contains NH3 decomposition catalyst and in which a catalytic decomposition of NH3 to N2 and H2 takes place to a certain extent.
  • an intermediate product gas is formed which still contains considerable residual amounts of undecomposed NH3, but also N2 and H2 which have already been formed.
  • the intermediate product gas preferably cools down.
  • the conversion of decomposed NH3 in the pre-reactor is at most 30%, more preferably at most 25%, even more preferably at most 20% of the total conversion achieved overall.
  • the conversion of decomposed NH3 in the pre-reactor is at least 10%, more preferably at least 15% of the total conversion achieved.
  • the intermediate product gas is preferably reheated before it enters the downstream, second NH3 decomposition device.
  • the temperature of the intermediate product gas after reheating and upon entry into the second NH3 decomposition device is about 550°C to about 680°C, more preferably about 580°C.
  • the temperature of the intermediate product gas after reheating and upon entry into the second NH3 decomposition device is about 620°C to about 680°C, more preferably about 650°C.
  • the remaining decomposition of NH3 then takes place in the second NH3 decomposition device until the total conversion is achieved.
  • the temperature of the intermediate product gas when entering the pre-reactor (first NH3 decomposition device) and when entering the second NH3 decomposition device can each be lower than the temperature of the NH 3 in single-stage decomposition of NH 3 , i.e. if only a single NH 3 -Decomposition device- tion. Due to the lower temperature, nitriding of the pipes occurs to a lesser extent, which increases the service life of the steel treated with NH 3 comes into contact.
  • the NH 3 -Decomposition catalyst in the first NH 3 -Decomposition device (pre-reactor) is preferably the same as in the second NH 3 -Decomposition device.
  • the exhaust gas By burning combustion gas with combustion air, an exhaust gas is generated in the combustion plant, preferably the combustion device, which leaves the combustion plant, preferably into an exhaust gas duct.
  • the exhaust gas has one or more of the following properties when leaving the combustion plant, preferably the combustion device, and when entering the exhaust gas duct: [0160]
  • the exhaust gas has a NOX content which is greater than the N2O content.
  • the NOX content is at least twice as high, more preferably at least three times as high, even more preferably at least four times as high, most preferably at least seven times as high and in particular at least ten times as high as the N2O content.
  • the molar ratio of NOX:N2O is more than 10:1, more preferably at least 20:1, even more preferably at least 30:1, most preferably at least 40:1, and in particular at least 50:1.
  • the exhaust gas has a NO content which is greater than the N2O content.
  • the NO content is at least twice as high, more preferably at least three times as high, even more preferably at least four times as high, most preferably at least seven times as high, and in particular at least ten times as high as the N2O content.
  • the exhaust gas has a NO2 content which is greater than the N2O content.
  • the NO2 content is at least twice as high, more preferably at least three times as high, even more preferably at least four times as high, most preferably at least seven times as high, and in particular at least ten times as high as the N2O content.
  • the exhaust gas has a content of NO X of at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, and in particular at least 50 ppmv.
  • the exhaust gas preferably has a NOX content of at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, and in particular at least 250 ppmv.
  • exhaust gas has a content of NO X of at least 500 ppmv, preferably at least 1000 ppmv, more preferably at least 2000 ppmv, even more preferably at least 3000 ppmv, and in particular at least 3500 ppmv.
  • the exhaust gas has a content of N 2 O of at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, and in particular at least 50 ppmv.
  • the exhaust gas has an N2O content of at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, and in particular at least 250 ppmv.
  • Preferred exhaust gases have a NO content X in the range from 1500 to 3000 ppmv, preferably 2000 to 3000 ppmv, and an N2O content in the range from 20 to 100 ppmv.
  • the exhaust gas has an H2O content of more than 4.0 vol.%; preferably at least 5.0 vol.%, more preferably at least 6.0 vol.%, even more preferably at least 7.0 vol.%, most preferably at least 8.0 vol.%, and in particular at least 9.0 vol.%.
  • the exhaust gas has an H2O content of at least 10 vol.%; preferably at least 12 vol.%, more preferably at least 14 vol.%, even more preferably at least 16 vol.%, most preferably at least 18 vol.%, and in particular at least 20 vol.%.
  • the exhaust gas has a content of H2O in the range of 10 ⁇ 8 vol.%; preferably in the range of 10 ⁇ 7 vol.%, more preferably in the range of 10 ⁇ 6 vol.%, even more preferably in the range of 10 ⁇ 5 vol.%, most preferably in the range of 10 ⁇ 4 vol.%, and in particular in the range of 10 ⁇ 3 vol.%.
  • the exhaust gas has a content of H2O in the range of 15 ⁇ 8 vol.%; preferably in the range of 15 ⁇ 7 vol.%, more preferably in the range of 15 ⁇ 6 vol.%, even more preferably in the range of 15 ⁇ 5 vol.%, most preferably in the range of 15 ⁇ 4 vol.%, and in particular in the range of 15 ⁇ 3 vol.%.
  • the exhaust gas has a content of H 2 O in the range of 25 ⁇ 8 vol.%; preferably in the range of 25 ⁇ 7 vol.%, more preferably in the range of 25 ⁇ 6 vol.%, still more preferably in the range of 25 ⁇ 5 vol.%, most preferably in the range of 25 ⁇ 4 vol.%, and in particular in the range of 25 ⁇ 3 vol.%.
  • the exhaust gas preferably has an N2 content of 2 of at least 40 vol.%, preferably at least 50 vol.%, more preferably at least 60 vol.%, even more preferably at least 70 vol.%, most preferably at least 80 vol.%, and in particular at least 90 vol.%.
  • the exhaust gas on leaving the firing system preferably the combustion device, has a temperature T1 of at least 500°C, more preferably at least 600°C, even more preferably at least 700°C, most preferably at least 800°C, and in particular at least 900°C.
  • the exhaust gas on leaving the firing system preferably the combustion device
  • the exhaust gas has a pressure of at most 1.5 bar when leaving the combustion plant, preferably the combustion device; preferably atmospheric pressure.
  • the exhaust gas has an oxidation level of NOX of at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, and in particular at least 50% when leaving the combustion plant, preferably the combustion device.
  • the exhaust gas has an oxidation level of NO of at least 10% when leaving the combustion plant, preferably the combustion device.
  • X of at most 90%, more preferably at most 80%, even more preferably at most 70%, most preferably at most 60%, and in particular at most 50%.
  • the exhaust gas has an O2 content of less than 2.0 vol.% when leaving the combustion plant, preferably the combustion device.
  • the optimized temperature depends on the selected design of steps (d) and (e), i.e. on the type and sequence of the individual process steps for N 2 O reduction and NO X -reduction and in particular the type of catalyst materials used for the N 2 O decomposition catalyst and/or N 2 O reduction catalyst and NO X -Reduction catalyst.
  • Suitable devices for changing the temperature of the exhaust gas are known to a person skilled in the art and include in particular heat exchangers, which can be designed, for example, as plate heat exchangers or tube heat exchangers.
  • the cooling of the exhaust gas preferably takes place in at least one heat exchanger which is arranged downstream of the combustion plant in the flow direction of the exhaust gas.
  • the exhaust gas from a tube reactor designed analogously to a primary reformer contains considerable amounts of internal energy.
  • the process for generating H2 from NH3 requires the supply of process streams at high temperatures.
  • the exhaust gas is used to preheat these process streams and is cooled in the process.
  • the effectiveness of different process variants can be measured by the hydrogen yield. This is defined as follows: ⁇ [0189]
  • the hydrogen yield of the plant is the ratio of the molar flow of H 2 that leaves the plant as a product compared to the mole flow of NH 3 which enters the plant in the feed stream, including a possible branch to the combustion gas.
  • a number of process streams are available for the absorption of heat from the exhaust gas: - Preheating and evaporation of NH 3 (also possible indirectly); - further heating of vaporized NH3 and of intermediate product gas; - heating of combustion air; - preheating of boiler feed water; - heating of water; - heating of combustion gas; - Evaporation of boiler feed water to generate steam; - Superheating of steam; - Auxiliary streams (heat transfer medium for preheating NH3 or for the evaporator of an NH3 desorption unit).
  • the target temperature of the process streams to be heated usually determines the order in which they are heated.
  • the heat contained in the product gas for the following measures for heat integration: - generation of water vapor; - preheating of NH3; - preheating of H2O for the generation of water vapor; and/or - cooling of the product gas with subsequent heat integration of the cooling water.
  • the heat contained in the exhaust gas for the following measures for heat integration: - preheating of the NH 3 on the inlet temperature for the NH 3 Decomposition device; - preheating of boiler feed water; and/or - preheating of combustion air.
  • Heat exchangers according to the invention serve to transfer heat from one medium to another medium without the media being mixed with one another.
  • the medium A that releases the heat is mentioned first, followed by the medium B that absorbs the heat.
  • an "exhaust gas/NH3 heat exchanger” serves to release heat contained in the exhaust gas to NH3.
  • the exhaust gas/NH3 heat exchanger is connected accordingly, i.e. its warmer side is flowed through by exhaust gas, whereas its cooler side is flowed through by NH3.
  • NH3 is used in the nomenclature for starting material and for any intermediate product gas that still contains significant amounts of NH3.
  • Heat exchangers with the same functionality may be numbered to distinguish them, although a specific number does not necessarily mean that all heat exchangers with the same functionality and a lower number must necessarily be present at the same time. It is therefore possible that, for example, a second exhaust gas/combustion air heat exchanger is present, but a first exhaust gas/combustion air heat exchanger is not.
  • Each heat exchanger according to the invention can be present independently of one another, if necessary as an individual heat exchanger of the described design or connection, or if necessary also as part of a plurality of several, e.g. two or three heat exchangers connected directly one after the other with the same functionality of the described design or connection.
  • the medium that emits the heat and the medium that absorbs the heat are then the same in the plurality of heat exchangers with the same functionality.
  • This division of a single heat exchanger into, for example, two heat exchangers connected one after the other with the same functionality can have structural and/or design advantages.
  • the exhaust gas leaves the combustion system, preferably the combustion device, at a temperature T 1 and is preferably heated in step (b) to a temperature T 2 cooled, where the exhaust gas then subsequently transferred to the exhaust gas treatment system.
  • both the at least one heat exchanger and the exhaust gas treatment system are arranged in an exhaust gas duct.
  • a single heat exchanger is arranged in the flow direction of the exhaust gas downstream of the combustion system, in which the cooling of the exhaust gas takes place (see Figure 2).
  • at least two heat exchangers are arranged in the flow direction of the exhaust gas downstream of the combustion system, in which the cooling of the exhaust gas takes place one after the other (see Figures 3, 5 and 6).
  • at least three heat exchangers are arranged in the flow direction of the exhaust gas downstream of the combustion system, in which the cooling of the exhaust gas takes place one after the other (see Figure 4).
  • the cooling of the exhaust gas in the at least one heat exchanger takes place by releasing heat from the exhaust gas to a heat transfer medium.
  • NH3 is preferably used as the heat transfer medium, which is then subsequently fed to the catalytic decomposition in an NH3 decomposition device on an NH3 decomposition catalyst.
  • the cooling of the exhaust gas takes place in at least one first exhaust gas/NH3 heat exchanger, which is arranged downstream of the combustion system in the flow direction of the exhaust gas.
  • an NH3 decomposition device is arranged in the flow direction of the NH3 downstream of the first exhaust gas/NH3 heat exchanger, in which a catalytic decomposition of the heated NH3 takes place on an NH3 decomposition catalyst to produce a product gas.
  • step (b) of the method according to the invention the cooling of the exhaust gas takes place - in a first exhaust gas/NH3 heat exchanger, which is arranged downstream of the combustion plant in the flow direction of the exhaust gas, and - in a second exhaust gas/NH3 heat exchanger, which is arranged downstream of the first exhaust gas/NH 3 -heat exchanger is arranged.
  • a first NH3 decomposition device (pre-reactor) is arranged, in which a partial catalytic decomposition of the heated NH3 takes place on an NH3 decomposition catalyst to produce an intermediate product gas.
  • a first NH3 decomposition device pre-reactor
  • the second exhaust gas/NH 3 -Heat exchanger arranged.
  • a second NH 3 -decomposition device in which a catalytic decomposition of the heated NH 3 at a NH 3 -decomposition catalyst to produce a product gas.
  • the NH 3 (or the intermediate gas) is in the first exhaust gas/NH 3 -Heat exchanger and in the second exhaust gas/NH 3 -Heat exchanger is heated by absorbing heat from the exhaust gas.
  • the exhaust gas first flows through the first exhaust gas/NH3 heat exchanger and then through the second exhaust gas/NH3 heat exchanger.
  • the NH 3 (or the intermediate product gas) initially flows through the first exhaust gas/NH 3 -Heat exchanger and absorbs heat from the exhaust gas.
  • the heated NH 3 into the first NH3 decomposition device, in which a partial catalytic decomposition of the heated NH3 takes place on an NH3 decomposition catalyst to produce an intermediate product gas.
  • step (b) of the method according to the invention the cooling of the exhaust gas takes place - in a first exhaust gas/NH3 heat exchanger, which is arranged downstream of the combustion plant in the flow direction of the exhaust gas, - in a second exhaust gas/NH3 heat exchanger, which is arranged downstream of the first exhaust gas/NH3 heat exchanger in the flow direction of the exhaust gas, and - in a third exhaust gas/NH3 heat exchanger, which is arranged downstream of the second exhaust gas/NH3 heat exchanger in the flow direction of the exhaust gas.
  • a first NH 3 -decomposition device (first pre-reactor) is arranged, in which a partial catalytic decomposition of the heated NH 3 at a NH 3 -decomposition catalyst to produce a first intermediate gas.
  • the second exhaust gas/NH 3 -Heat exchanger is arranged in the flow direction of the NH 3 downstream of the first NH 3 -Decomposition device (first pre-reactor).
  • a second NH 3 -decomposition device (second pre-reactor) is arranged, in which a further partial catalytic decomposition of the heated NH 3 (first intermediate gas) at a NH 3 - decomposition catalyst to produce a second intermediate gas.
  • second pre-reactor Preference is given to Flow direction of the NH 3 downstream of the second NH 3 -Decomposition device (second pre-reactor) the third exhaust gas/NH 3 -Heat exchanger is arranged.
  • a third NH 3 -decomposition device in which a catalytic decomposition of the heated NH 3 (second intermediate gas) at a NH 3 -decomposition catalyst to produce a product gas.
  • the NH3 (or the first intermediate product gas or the second intermediate product gas) is heated in the first exhaust gas/NH3 heat exchanger, in the second exhaust gas/NH3 heat exchanger and in the third exhaust gas/NH3 heat exchanger by absorbing heat from the exhaust gas.
  • the exhaust gas first flows through the first exhaust gas/NH 3 -Heat exchanger, then the second exhaust gas/NH3 heat exchanger and then the third exhaust gas/NH3 heat exchanger.
  • the NH3 (or the first intermediate product gas or the second intermediate product gas) first flows through the first exhaust gas/NH3 heat exchanger and absorbs heat from the exhaust gas therein.
  • the heated NH3 then flows into the first NH3 decomposition device, in which a partial catalytic decomposition of the heated NH3 takes place on an NH3 decomposition catalyst to produce a first intermediate product gas.
  • the first intermediate product gas thus formed which still contains considerable amounts of undecomposed NH3, then flows through the second exhaust gas/NH3 heat exchanger and again absorbs heat from the exhaust gas therein.
  • the heated first intermediate product gas then flows into the second NH3 decomposition device, in which a further partial catalytic decomposition of the heated NH3 takes place on an NH3 decomposition catalyst to produce a second intermediate product gas.
  • the second intermediate product gas thus formed which still contains considerable amounts of undecomposed NH3, then flows through the third exhaust gas/NH3 heat exchanger and again absorbs heat from the exhaust gas therein.
  • the heated second intermediate product gas flows into the third NH3 decomposition device, in which a catalytic decomposition of the heated NH3 takes place on an NH3 decomposition catalyst to produce a product gas (see Figure 4).
  • the exhaust gas is preferably heated to a temperature T 2 cooled, in which the exhaust gas is then subsequently transferred to the exhaust gas treatment plant.
  • the temperature T2 is at least 360°C, more preferably at least 370°C, even more preferably at least 380°C, most preferably at least 390°C, and in particular at least 400°C.
  • the temperature T 2 at most 500°C, more preferably at most 480°C, even more preferably at most 460°C, most preferably at most 440°C, and in particular at most 420°C.
  • the temperature T 2 in the range of 400 to 450°C, preferably 400 to 420°C.
  • the ideal temperature T 2 depends on the NO X -entry concentration and the associated heat emission. Per 1000 ppmv NO X A ⁇ T of around 12K is to be expected. For example, if the exhaust gas contains 7000 ppmv NO X , this would correspond to around 80-90 K.
  • the outlet temperature should not be too high, because the stability of the catalysts in the exhaust gas treatment system is a critical factor due to the high water content of the exhaust gas.
  • a multi-stage arrangement of catalyst beds with multi-stage NH 3 -Feed and intermediate heat exchangers are provided. In this way, excessively high temperatures are avoided. In addition, this enables a significantly higher NOX and N2O degradation (with the same catalyst volume).
  • the exhaust gas has a temperature T2 on entering the exhaust gas treatment system which is relatively at least 20°C, preferably at least 40°C, more preferably at least 60°C, even more preferably at least 80°C, most preferably at least 100°C, and in particular at least 120°C below the temperature T1 which the exhaust gas has on leaving the firing system, preferably the combustion device.
  • the temperature T2 is relatively at least 50°C lower than the temperature T1, more preferably at least 100°C, even more preferably at least 150°C, most preferably at least 200°C, and in particular at least 250°C.
  • the optionally cooled exhaust gas is transferred to an exhaust gas treatment system, i.e. from the combustion system from step (a) or from the at least one heat exchanger from the optional and preferred step (b) to an exhaust gas treatment system.
  • the exhaust gas which has left the combustion system, preferably the combustion device, and which was possibly cooled in step (b) is transferred to an exhaust gas treatment system.
  • This can be done, for example, by pipes which connect the outlet of the combustion system, preferably the combustion device, to the inlet of the exhaust gas treatment system. This connection is preferably made via an exhaust gas duct.
  • the method according to the invention is preferably carried out at atmospheric pressure, no special requirements are typically placed on such pipes or on the walls of the exhaust gas duct with regard to possible pressure stress.
  • the pipes or walls of the exhaust gas duct should withstand the temperatures which the exhaust gas has when leaving the combustion plant, preferably the combustion device, or when entering the exhaust gas treatment plant.
  • steps (d) and (e) of the method according to the invention take place.
  • the exhaust gas treatment plant is equipped with the N 2 O decomposition catalyst for step (d 1 ) and/or with the N 2 O reduction catalyst for step (d 2 ) and the NO X -Reduction catalyst for step (e).
  • the exhaust gas treatment system according to the invention additionally comprises at least one further catalyst or one of the above-mentioned N2O reduction, N2O decomposition or NOX reduction catalysts fulfills at least one further functionality, at least one of the following steps (g1) to (g4 is preferably additionally carried out in the exhaust gas treatment system according to the invention: (g1) cooling the exhaust gas in at least one heat exchanger, which is preferably arranged within the exhaust gas treatment system; preferably in the flow direction of the exhaust gas upstream of the NH3 oxidation catalyst; (g2) reducing the content of NH3 in the exhaust gas by oxidation with an oxidizing agent on an NH3 oxidation catalyst; wherein the oxidizing agent preferably comprises O2; (g3) reducing the content of HCN in the exhaust gas by hydrolysis and oxidation of the hydrolysates with an oxidizing agent on an HCN degradation catalyst; wherein the oxidizing agent preferably comprises NOX and/or N2O; and (g4) reducing the CO content in the
  • step (d) of the process according to the invention the N2O content in the exhaust gas is reduced. This can be done by (d1) decomposition of N2O on a N2O decomposition catalyst and/or (d2) chemical reduction of N2O with reducing agent on a N2O reduction catalyst.
  • N2 and O2 are formed according to the following overall reaction: 2 N 2 O ⁇ 2 N 2 + O 2 .
  • Decomposition of N 2 O therefore means decomposition into N 2 and O 2 .
  • a "N 2 O decomposition catalyst" in the sense of the invention catalyzes the decomposition of N2O.
  • the achievable reduction of N2O by catalytic decomposition depends not only on the type, i.e. the chemical nature and physical configuration of the N 2 O decomposition catalyst and the existing pressure and temperature conditions, especially also dependent on the selected space velocity, i.e. the ratio of exhaust gas volume flow to the catalyst volume.
  • the catalytic activity of an N 2 O decomposition catalyst does not have to be limited exclusively to this reaction. It is therefore entirely possible and, according to the invention, also preferred that the N 2 O decomposition catalyst can also catalyze other reactions, such as the chemical reduction of N 2 O and/or the chemical reduction of NOX.
  • CO is also preferred as a reducing agent according to the invention. It can react further with N2O to form CO2, e.g. according to: N2O + CO ⁇ N2 + CO2.
  • An "N2O reduction catalyst" in the sense of the invention catalyzes the chemical reduction of N2O with reducing agent. However, the catalytic activity of an N2O reduction catalyst does not have to be limited exclusively to this reaction.
  • the N2O reduction catalyst can also catalyze further reactions, for example the decomposition of N2O and/or the chemical reduction of NO X . Whether such further reactions actually take place depends on the conditions of the individual case, in particular the type of catalyst, and the kinetics of any processes taking place in parallel, for example the presence or amount of the reducing agent and the presence or amount of other reaction partners.
  • NO X -Reduction catalysts which preferably enable the selective catalytic reduction (SCR) of the nitrogen oxides contained in the exhaust gas
  • NO X enable i.e. the NOX reduction catalysts primarily catalyze the oxidation of NH3 with NOX and not or only to a lesser extent the oxidation of NH3 with free oxygen (O2) possibly present in the exhaust gas.
  • SCR selective catalytic reduction
  • the NOX reduction catalysts primarily catalyze the oxidation of NH3 with NOX and not or only to a lesser extent the oxidation of NH3 with free oxygen (O2) possibly present in the exhaust gas.
  • O2 free oxygen
  • N2 and H2O in particular are formed during the chemical reduction of NOX, depending on the type of NOX reduction catalyst and the ratio of NO to NO2, e.g. according to: 4 NH3 + 2 NO + 2 NO2 ⁇ 4 N2 + 6 H2O (so-called fast SCR) 4 NH3 + 4 NO + O2 ⁇ 4 N2 + 6 H2O (so-called normal SCR) 8 NH3 + 6 NO2 ⁇ 7 N2 + 12 H2O (so-called NO2 SCR).
  • the joint selective catalytic reduction is referred to as so-called fast SCR and generally proceeds much faster than the so-called normal SCR or NO2 SCR.
  • a "NOX reduction catalyst” in the sense of the invention catalyzes the chemical reduction of NOX with reducing agent.
  • the catalytic activity of a NOX reduction catalyst does not have to be limited exclusively to this reaction. It is therefore entirely possible and also preferred according to the invention that the NOX reduction catalyst can also catalyze further reactions, for example the decomposition of N2O, the chemical reduction of N2O and/or the adjustment of the NOX equilibrium or the selective oxidation of excess NH3 with free O2. Whether such further reactions actually take place depends on the conditions of the individual case and the kinetics of the processes that may take place in parallel, for example the presence or amount of the reducing agent and the presence or amount of other reaction partners.
  • N 2 O decomposition catalysts are known per se and a wide variety of substance classes can be used.
  • N 2 O decomposition catalysts which, for example, have a high catalytic activity for the decomposition of N in the temperature range of 350 to 600°C. 2 O to N 2 and O 2 exhibit.
  • Preferred examples of N according to the invention 2 O decomposition catalysts are metal-loaded zeolite catalysts, for example zeolite catalysts loaded with copper or cobalt or in particular with iron, noble metal catalysts or transition metal oxide catalysts, such as catalysts containing cobalt oxide. Examples of suitable catalysts are described by Kapteijn et al. in Appl. Cat.
  • N2O decomposition catalysts are catalysts whose activity for N2O decomposition is significantly limited by the presence of NOX.
  • Such N2O decomposition catalysts are also referred to as "NOX-sensitive N2O decomposition catalysts" for the purposes of the description.
  • These catalysts contain one or more catalytically active compounds of elements selected from groups 5 to 11 of the Periodic Table of the Elements (PSE).
  • PSE Periodic Table of the Elements
  • Compounds of the elements of groups 9 to 11 of the PSE are particularly preferred. Of these, preference is given to compounds of the elements Co, Pt, Pd, Ir, Rh, Ni and/or Cu, preferably Co, Rh, Ni and/or Cu and in particular Co or Rh.
  • the catalyst is an N2O decomposition catalyst based on noble metals, which are preferably supported on refractory oxides, or based on mixtures of transition metal oxides, in particular mixed oxides or simple transition metal oxides, each either supported or preferably as full catalysts.
  • the catalytically active compounds themselves can be metallic and/or oxidic compounds, the latter being able to be present both as singular oxides or as binary, ternary or polynary mixed oxides of different structural types, such as perovskites or spinels. Such compounds are described, for example, in Catalysis Letters 35 (1995) 372-382, Applied Catalysis 73 (1991) 165- 171, Catal. Rev.-Sci.
  • catalytically active compounds can also be used.
  • particularly preferred catalytically active compounds are metallic rhodium, rhodium oxides such as RhO 2 , or Rh 2 O 3 , CoO, Co 2 O 3 , Co-containing spinels such as Co3O4, CuxCo3-xO4 or Co-containing perovskites such as LaCoO3 or Co-containing perovskites substituted on A and B sites.
  • the catalytically active compounds can be contained in the catalysts in pure form or applied to suitable support materials or mixed with such.
  • full catalysts which, in addition to active compounds, also contain the following to the person skilled in the art: known additives such as binders or other additives required during production such as plasticizers, pore formers, fiber reinforcements or pressing aids.
  • known additives such as binders or other additives required during production such as plasticizers, pore formers, fiber reinforcements or pressing aids.
  • the methods for producing such catalysts are known to those skilled in the art.
  • the catalytically active compounds are applied to the support material. This causes the catalytically active compound to be dispersed and stabilized against both mechanical and thermal stress.
  • the methods for producing such catalysts are also known to those skilled in the art.
  • the support materials are preferably refractory oxides, such as SiO 2 , TiO 2 , ZrO 2 or Al 2 O 3 or mixtures of two or more thereof or materials which themselves have a certain catalytic activity for N2O decomposition, such as, for example, MgO, zeolites, hydrotalcites or mixtures of two or more thereof. Preference is given to using catalysts which contain no or essentially no zeolites, preferably less than 15% by weight of zeolites, in particular less than 5% by weight of zeolites.
  • Preferred support materials for Rh-containing compounds are ZrO2, TiO2, Al2O3, hydrotalcites or zeolites, e.g. of the MFI structure type.
  • Rh-containing compounds are ZrO2, TiO2 and hydrotalcites.
  • the Rh content of these catalysts is preferably 0.1 to 10% by weight, preferably 0.5 to 5% by weight.
  • Rh-containing catalysts contain CeO2 in addition to Rh.
  • the proportion of CeO2 is preferably 5 to 50% by weight, in particular 10 to 30% by weight.
  • Preferred supports for Co-containing compounds are zeolites or the preferred supports contain magnesium oxide. In the case of zeolites, Si-rich structural types such as MFI, BEA, FER, MEL or MOR are particularly preferred.
  • Co-doped zeolites are known to the person skilled in the art.
  • it can be pure MgO or MgO-containing compounds such as hydrotalcites.
  • Such catalysts are described, for example, in Appl. Catal. B: Environmental 7 (1996) 397-406 or Appl. Catal. B: Environmental 13 (1997) 69-79.
  • catalysts are those which essentially consist of at least one oxidic magnesium compound and at least one oxidic cobalt compound, the content of oxidic cobalt compounds being in the range from 0.1 to 50% by weight and the content of oxidic magnesium compounds being in the range from 50 to 99.9% by weight, each based on the total mass of the catalyst, and at least 30% by weight of the Co atoms contained in the catalyst being in the chemically trivalent state.
  • oxidic magnesium compound essentially consist of at least one oxidic magnesium compound and at least one oxidic cobalt compound, the content of oxidic cobalt compounds being in the range from 0.1 to 50% by weight and the content of oxidic magnesium compounds being in the range from 50 to 99.9% by weight, each based on the total mass of the catalyst, and at least 30% by weight of the Co atoms contained in the catalyst being in the chemically trivalent state.
  • the N 2 O decomposition catalyst can be in the form of a shaped body of any size and geometry, preferably in geometries that have a large surface to volume ratio and through which the lowest possible pressure loss is generated. Typical geometries are all those known in catalysis, such as cylinders, hollow cylinders, multi-hole cylinders, rings, granulate fragments, trilobes or honeycomb structures.
  • N 2 O reduction catalysts and NO X -Reduction catalysts are also known per se and a wide variety of classes of materials can also be used. Examples of these are metal-loaded zeolite catalysts, such as zeolite catalysts loaded with copper or cobalt, or in particular zeolite catalysts loaded with iron, or noble metal catalysts or catalysts which are used in the known SCR processes (Selective Catalytic Reduction).
  • the N2O decomposition catalyst and/or the N2O reduction catalyst and/or the NOX reduction catalyst independently of one another contain a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably a zeolite loaded with iron; more preferably, independently of one another, an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL.
  • a zeolitic material preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper
  • a zeolite loaded with iron more preferably, independently of one another, an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL.
  • both the N2O decomposition catalyst and/or the N2O reduction catalyst and the NOX reduction catalyst independently of one another comprise a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; more preferably, independently of one another, an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL.
  • These can be different catalysts or the same catalysts.
  • Iron-loaded zeolite catalysts used with particular preference according to the invention contain essentially, preferably > 50% by weight, in particular > 70% by weight, of one or more iron-loaded zeolites.
  • an Fe-ZSM-5 zeolite in addition to an Fe-ZSM-5 zeolite, another iron-containing zeolite, such as an iron-containing zeolite of the FER type, can be contained in the catalyst used according to the invention.
  • the catalyst used according to the invention can contain other additives known to the person skilled in the art, such as binders.
  • the iron content of the zeolites used with preference can be up to 25% based on the mass of zeolite, but preferably 0.1 to 10%.
  • the process according to the invention also includes the use of zeolites in which the lattice aluminum is partially isomorphously substituted by one or more elements, for example by one or more elements selected from B, Be, Ga, Fe, Cr, V, As, Sb and Bi. Also included is the use of zeolites in which the lattice silicon is replaced by one or several elements are isomorphously substituted, for example by one or more elements selected from Ge, Ti, Zr and Hf. Precise information on the structure of the zeolites preferably used according to the invention is given in the Atlas of Zeolite Structure Types, Elsevier, 4" revised Edition 1996, to which reference is hereby expressly made.
  • Zeolite catalysts which have been treated with steam are very particularly preferably used in the process according to the invention.
  • These hydrothermally treated zeolite catalysts are characterized by a particularly high activity in the process according to the invention.
  • Hydrothermally treated zeolite catalysts which have been loaded with iron and in which the ratio of extra-lattice aluminum to lattice aluminum is at least 1:2, preferably 1:2 to 20:1, are preferably used.
  • the N2O decomposition catalyst and/or the The N2O reduction catalyst and the NOX reduction catalyst preferably each independently comprise zeolites loaded with transition metal, more preferably zeolites loaded with iron (Fe zeolites), even more preferably zeolites loaded with iron of the same structural type, most preferably with the same external shape (e.g. honeycomb or pellet).
  • the N2O decomposition catalyst and the N2O reduction catalyst are made of the same material.
  • the N2O decomposition catalyst and the NOX reduction catalyst are made of the same material.
  • the N2O reduction catalyst and the NOX reduction catalyst are made of the same material.
  • the N2O decomposition catalyst, the N2O reduction catalyst and the NOX reduction catalyst are made of the same material.
  • the exhaust gas is cooled after leaving the combustion plant, preferably the combustion device, in the course of the optional and preferred step (b) of the process according to the invention, wherein steps (d1) and/or (d2) and/or (e) can introduce new heat.
  • N2O decomposition catalysts for the purposes of the description also "zeolites" which are reacted with at least one transition metal (atomic numbers 21-30, 39-48, 57-80, 89-112) and/or with at least one lanthanide (also "lanthanide”).
  • transition metals and lanthanides are referred to jointly as “transition metals” for the sake of simplicity.
  • the transition metals iron (“Fe zeolites”), copper (“Cu zeolites”) and cobalt (“Co zeolites”) are preferred.
  • Zeolitic materials loaded with iron i.e. Fe zeolites
  • the zeolitic materials according to the invention preferably have a high hydrothermal resistance.
  • SiO 2 -rich zeolites so-called "high-silica zeolites", which have a molar ratio of [SiO 2 ]- to [AlO 2 -] units, and thus a molar Si/Al ratio of at least 8, preferably at least 9, more preferably at least 10, even more preferably at least 11, most preferably at least 12, and in particular at least 13.
  • Zeolitic materials preferred according to the invention essentially have a zeolite structure of the structure type BEA, MFI, MOR, MEL or FER, more preferably of the structure type MFI and BEA, even more preferably of the structure type BEA. In the case of the structure type MFI, the type ZSM-5 is particularly preferred.
  • N2O decomposition, N2O reduction or NOX reduction catalysts according to the invention contain independently of one another at least 50% by weight of Fe zeolite in relation to the total weight of the zeolitic material, more preferably at least 70% by weight of Fe zeolite, where a single structural type or also several structural types can be present.
  • Fe-BEA zeolite in addition to Fe-BEA zeolite, another Fe zeolite of a different structural type is present, preferably Fe-MOR zeolite.
  • the loading (doping) of the zeolitic materials with the transition metals/lanthanides can be carried out according to relevant methods for loading or doping zeolites with transition metals/lanthanides, which are known to those skilled in the art.
  • the loading is carried out starting from the commercially available H form or preferably NH4 form of the zeolitic materials by ion exchange with corresponding salts of the transition metals, in the aqueous phase or by solid-state reaction.
  • the loaded zeolitic materials obtained in this way are then calcined, preferably in air in an oven at temperatures in the range of 400 to 650°C.
  • the loaded zeolitic materials are washed intensively in distilled water and the filtered loaded zeolitic materials are then dried.
  • the loaded zeolitic materials obtained in this way are mixed with suitable binders, such as aluminosilicates, boehmite or silica sol, and optionally auxiliary materials for plasticizing or for producing slips.
  • suitable binders such as aluminosilicates, boehmite or silica sol
  • auxiliary materials for plasticizing or for producing slips.
  • the mixtures obtained in this way are extruded to form catalyst bodies (full catalysts) and finally calcined.
  • the mixtures thus obtained are applied to catalyst supports (supported catalysts) and finally calcined.
  • the N 2 O-decomposition, N 2 O-reduction, NO X -Reduction, NH 3 -Oxidation, HCN degradation and CO oxidation catalysts can be present independently of one another as shaped bodies of any size and geometry, preferably in geometries that have a large surface to volume ratio and through which the lowest possible pressure loss is generated.
  • Typical geometries are all geometries known in catalysis, such as cylinders, hollow cylinders, multi-hole cylinders, rings, trilobes or star-shaped extrudates.
  • Monolithic catalyst elements with parallel channels running through them are particularly preferred, e.g.
  • the exhaust gas treatment system according to the invention or the catalyst beds contained therein preferably have catalyst honeycombs, preferably a plurality of catalyst honeycombs, which are arranged parallel to one another in the exhaust gas duct with honeycomb channels each aligned longitudinally to the flow direction of the exhaust gas.
  • the geometry of the cross-sectional area of the catalyst honeycombs (perpendicular to the flow direction of the exhaust gas) is in principle freely selectable.
  • the catalyst honeycombs preferably have a rectangular or, in particular, square cross-sectional area, but other cross-sectional areas are also possible, in particular hexagonal, triangular, trapezoidal, etc. Suitable geometries are known to those skilled in the art.
  • honeycomb is therefore not restricted according to the invention to a rectangular or square cross-sectional area.
  • the exhaust gas treatment system comprises a first reaction zone (first catalyst bed) and a second reaction zone (second catalyst bed) downstream in the flow direction of the exhaust gas, which is preferred according to the invention
  • the first and second reaction zones preferably have a plurality of catalyst honeycombs which are arranged parallel to one another in the exhaust gas channel with honeycomb channels each aligned longitudinally to the flow direction of the exhaust gas.
  • a plurality of catalyst honeycombs i.e. a plurality of monolithic honeycomb bodies, are combined to form a honeycomb module, preferably by a metal frame which is open in the flow direction of the exhaust gas.
  • honeycomb bodies Preferably, two, four or six honeycomb bodies, preferably monolithic honeycomb bodies, are combined to form a honeycomb module.
  • This modular construction allows good utilization of the available cross-sectional area of the exhaust duct and easy replacement of defective or deactivated honeycomb bodies.
  • the honeycomb bodies preferably have a rectangular cross-section.
  • the rectangular cross-section a first edge length (perpendicular to the flow direction of the exhaust gas) in the range from 5 to 20 cm, more preferably 10 to 15 cm, and a second edge length (also perpendicular to the flow direction of the exhaust gas) in the range from 5 to 20 cm, preferably 10 to 15 cm.
  • the height of a honeycomb body (flow direction of the exhaust gas) is preferably in the range from 5 to 25 cm, preferably in the range from 7.5 to 15 cm.
  • the so-called cell density i.e. density of the channels of an individual catalyst honeycomb, is preferably 150 to 500 cpsi, more preferably 180 to 450 cpsi (cell per square inch).
  • 100 cpsi i.e. 100 cells or honeycomb channels per square inch, correspond to approximately 15.5 catalyst channels per cm2.
  • the individual honeycomb modules are stacked one above the other and next to the other in the flow direction and fixed by appropriate holder devices so that the best possible use of the inflow area, i.e.
  • cross-sectional area of the exhaust duct is achieved.
  • Bypass flows between the individual honeycomb modules or in the outer edge area between the outer edge of the honeycomb modules and the inner wall of the exhaust duct should be avoided.
  • suitable sealing materials are preferably applied between the individual honeycomb modules and between the outer honeycomb modules and the inner wall and, for larger wall distances, cover plates are used which are attached to the inner wall of the exhaust duct in the flow direction in front of and/or behind the packing of the honeycomb modules.
  • the cover plates are preferably covered with seals at the contact points with the honeycomb modules.
  • the honeycomb modules are preferably arranged and sized so that the usable flow area of the catalyst is preferably at least 60% of the inner cross-sectional area of the exhaust duct, more preferably at least 70%, even more preferably at least 80%.
  • the gussets that form in the edge area of the packing of the honeycomb modules are preferably not filled with specially cut honeycomb bodies, but are closed with blanking plates. This has the advantage that when replacing used honeycomb bodies, only standardized honeycomb modules need to be replaced and no special adaptations are required.
  • honeycomb bodies or honeycomb body modules are arranged in the flow direction of the exhaust gas in several layers that are offset along the longitudinal axis.
  • the honeycomb bodies or honeycomb body modules are preferably arranged in 2 to 5 layers, particularly preferably in 2 to 3 layers. Between the layers, i.e.
  • a distance is preferably provided, preferably in the range of 3 to 30 mm, more preferably 4 to 20 mm.
  • the distance can enable intermediate, in particular radial, mixing of the gas flow emerging from a first layer of the honeycomb bodies or honeycomb body modules. Furthermore, it can be avoided that a possible slip of unreacted reducing agent and/or of its not yet fully oxidized reaction products propagates from the first layer of the honeycomb bodies into a subsequent, second layer of the honeycomb bodies.
  • the supply and distribution of the reducing agents for NO X and if necessary N 2 O is preferably carried out via a multiply branched pipe system provided with a large number of openings or nozzles, which is arranged in the exhaust duct or in the exhaust line in the flow direction upstream of the respective catalyst bed, preferably the packing of the catalyst honeycombs as honeycomb bodies or honeycomb body modules.
  • the distributor pipes are preferably designed in the form of grids, so-called grids, or in the form of concentrically connected circles, which extend as far as possible over the cross-sectional area of the exhaust duct or the inflow area of the catalyst bed.
  • NH3 oxidation catalysts are known to experts.
  • the NH3 oxidation catalyst is free of platinum group metals, more preferably free of noble metals.
  • free of platinum group metals means that essentially no metal of the platinum group (i.e. Ru, Rh, Pd, Os, Ir, Pt) is present. Analytically detectable, minimal traces of platinum group metals are possible, however.
  • the NH 3 -Oxidation catalyst is a zeolite loaded with iron or copper; preferably a zeolite loaded with iron or copper of the structure type MFI, BEA, FER, MOR, FAU, AEI and/or MEL (hereinafter referred to as "NH 3 -oxidation-active, iron or copper-loaded zeolite catalyst").
  • Preferred platinum group metal-free NH 3 -Oxidation catalysts are selected from transition metal oxides (e.g.
  • metal-loaded zeolites e.g. described ben in Handbook of Heterogeneous Catalysis, Wiley-VCH, Edited by Ertl, Knötzinger, Schüth, Weit- kamp, 2nd Ed. 2008, Volume 5, Chapter 11.5 “Solid Catalysts for the Oxidation of Volatile Organic Compounds”.
  • the device according to the invention contains no further NH3 oxidation catalyst in addition to the zeolite loaded with iron or copper.
  • the NH3 oxidation catalyst preferably the NH3 oxidation-active, iron-loaded zeolite catalyst, has a molar ratio of iron to zeolitic aluminum n(Fe)/n(Al) of less than 0.50 to greater than 0.05; preferably less than 0.40 to greater than 0.05, more preferably less than 0.25 to greater than 0.05, even more preferably less than 0.15 to greater than 0.05.
  • the NH3 oxidation catalyst preferably the NH3 oxidation-active, copper-loaded zeolite catalyst, has a molar ratio of copper to zeolitic aluminum n(Cu)/n(Al) of less than 1.00 to greater than 0.10; preferably less than 0.80 to greater than 0.10, more preferably less than 0.50 to greater than 0.10, even more preferably less than 0.30 to greater than 0.10.
  • zeolites loaded with iron or copper in which only a portion of the potentially available cation sites are occupied by Fe or Cu ions, so that the remaining cation sites are essentially saturated by protons, have a significantly increased activity for the oxidation of NH3 with free oxygen.
  • the ratio of iron or copper to zeolitic aluminum can be adjusted by selecting the Al content during the synthesis of the zeolitic material, in particular by the proportions of the selected Si and Al starting materials, as well as by the subsequent loading with iron or copper ions.
  • the selected Si and Al starting materials are usually in alkaline solution, often under increased pressure, which causes crystallization to form microporous, three-dimensionally linked AlO 2 -- and SiO 2 -units, the zeolites.
  • structure-directing reagents e.g. organic cations
  • the structure type of the zeolite can be specifically adjusted or controlled.
  • the synthesis methods are industrially established. Zeolites of different structure types with different Si/Al ratios and loaded with different cations, e.g. in Na or NH 4 - form are commercially available.
  • the so-called degree of exchange is 100%.
  • the exact Al content of the zeolitic material present or of the catalyst moldings produced from it can be determined, as is known, by X-ray fluorescence analysis (XRF), just like the Fe content. This is conveniently carried out in accordance with DIN EN 169-2 (section 5) after determining the loss on ignition and after lithium tetraborate digestion.
  • XRF X-ray fluorescence analysis
  • the Al content of the underlying zeolitic material is to be subsequently determined on the finished molded body, it must be noted that the molded body can also contain Al-based binder components which cannot be distinguished from zeolitic Al by XRF.
  • the NH3 oxidation catalyst preferably the NH3 oxidation-active, iron-loaded zeolite catalyst, has a total iron content (indicated as the mass content of Fe 2 O 3 ) from less than 10.0 wt.% to greater than 2.0 wt.%, preferably from less than 7.0 wt.% to greater than 2.0 wt.%, more preferably from less than 5.0 wt.% to greater than 2.0 wt.% and even more preferably from less than 4.0 wt.% to greater than 2.0 wt.%.
  • the NH 3 -Oxidation catalyst preferably NH 3 -oxidation-active, copper-loaded zeolite catalyst, a total copper content (expressed as mass content Cu 2 O) from less than 9.0 wt.% to greater than 1.5 wt.%; preferably from less than 6.5 wt.% to greater than 1.5 wt.%, more preferably from less than 4.5 wt.% to greater than 1.5 wt.% and even more preferably from less than 3.5 wt.% to greater than 1.5 wt.%.
  • a total copper content (expressed as mass content Cu 2 O) from less than 9.0 wt.% to greater than 1.5 wt.%; preferably from less than 6.5 wt.% to greater than 1.5 wt.%, more preferably from less than 4.5 wt.% to greater than 1.5 wt.% and even more preferably from less than 3.5 wt.% to greater than 1.5 wt.%.
  • the NH 3 -Oxidation catalyst preferably NH 3 -oxidation-active, iron or copper-loaded zeolite catalyst, configured for the selective oxidation of NH3 with O2 to N2 and H2O, and effected when filled as a particulate bed, the particles of which have an equivalent diameter of 3.5 to 5.5 mm, which is defined as the diameter of a spherical particle of the same volume, and wherein the ratio of the outer, geometrically detectable surface of the particles to the volume of the particulate bed is 1000 m2/m3 to 1500 m2/m3, in an amount of 8.0 ⁇ 0.5 mL in an isothermally operated, axially flowing tubular reactor with an inner diameter of 20 ⁇ 3 mm, subjected to a volume flow of a gas mixture consisting of 500 ⁇ 50 ppmv NH3, 2.5 ⁇ 0.1 vol.% O2 and 0.30 ⁇ 0.05 vol.% H2O in N2 at a space velocity of 10,000 ⁇ 500 h-1
  • the N2O decomposition catalyst and/or the N2O reduction catalyst and/or the NOX reduction catalyst and/or the NH3 oxidation catalyst independently of one another have a honeycomb-shaped monolithic structure.
  • the N2O decomposition catalyst and/or the N2O reduction catalyst and/or the NOX reduction catalyst and/or the NH3 oxidation catalyst independently of one another have a honeycomb-shaped monolithic structure.
  • the NH3 oxidation catalyst and the N2O decomposition catalyst are made of the same material.
  • the NH3 oxidation catalyst and the N2O reduction catalyst are made of the same material.
  • the NH3 oxidation catalyst and the NOX reduction catalyst are made of the same material.
  • the NH3 oxidation catalyst, the NOX reduction catalyst and the N2O decomposition catalyst are made of the same material.
  • steps (d 1 ) and/or (d 2 ) and/or (e) the process according to the invention at different temperatures, i.e. at different temperatures temperature levels, with a step carried out earlier in time or upstream in the flow direction of the exhaust gas preferably taking place at a higher temperature than a step carried out later in time or downstream in the flow direction of the exhaust gas.
  • the steps may not be completely separable from one another, neither spatially nor temporally. If a catalyst used is used simultaneously to catalyze several of the steps (d 1 ), (d 2 ) and (e), these steps may take place simultaneously and/or sequentially.
  • a catalyst used is used simultaneously to catalyze several of the steps (d 1 ), (d 2 ) and (e), these steps may take place simultaneously and/or sequentially.
  • individual segments of one and the same catalyst can be considered, through which the exhaust gas flows one after the other and on which different reactions may dominate. In which segment which reaction dominates depends in particular on the respective reaction kinetics, the local temperature and the local concentrations of the reactants, possibly including the concentration of reducing agent and possibly including the concentration of co-catalytically active species.
  • the exhaust gas treatment system according to the invention serves in particular to carry out steps (d) and (e) of the method according to the invention. However, it is also possible for further steps to be carried out and chemical reactions to take place within the exhaust gas treatment system in addition to steps (d) and (e).
  • This preferably relates to the installation of a catalyst bed arranged downstream in the flow direction of the exhaust gas for the oxidation of incompletely converted reducing agents or of their incompletely oxidized reaction products, i.e. for example for the oxidation of NH3 (NH3 oxidation catalyst) or CO (CO oxidation catalyst; when using hydrocarbons as reducing agents).
  • the exhaust gas is preferably cooled before it is introduced into the catalyst bed arranged downstream, i.e. the oxidation of NH3 and/or CO preferably takes place at a lower temperature than steps (d) and (e).
  • steps (d) and (e) of the process according to the invention there are various preferred variants of the process according to the invention, which can differ from one another with regard to the order of the reactions taking place, the catalysts used, the reducing agents used, the space velocities and other reaction conditions.
  • these reactions are carried out in a common reaction zone (catalyst bed) which is equipped upstream with a device for metering reducing agent into the exhaust gas.
  • these reactions are carried out in two successively arranged, separate reaction zones (catalyst beds), of which preferably at least one reaction zone, preferably both reaction zones independently of one another, are equipped upstream with a device for metering reducing agent into the exhaust gas. is or are.
  • the exhaust gas then flows first through the first reaction zone and then through the second reaction zone.
  • Particularly preferred variants/embodiments include [a] (d 2 ) the chemical reduction of N 2 O with NH 3 and (e) the chemical reduction of NO X with NH3, preferably together in a reaction zone; [b] (d2) the chemical reduction of N2O with hydrocarbon (CH4, natural gas, etc.) and (e) the chemical reduction of NO X with NH 3 , preferably together in a reaction zone; [c] (d 1 ) the decomposition of N 2 O and (e) the chemical reduction of NO X with NH 3 , preferably together in a reaction zone; [d] (d 1 ) the decomposition of N 2 O and (d 2 ) the chemical reduction of N 2 O with NH 3 and (e) the chemical reduction of NOX with NH3, preferably together in one reaction zone; [e] (d1) the decomposition of N2O and (d2) the chemical reduction of N2O with hydrocarbon (CH4, natural gas, etc.) and (e) the chemical reduction of NOX with
  • the decomposition of N2O is typically superimposed on the chemical reduction of N2O with NH3, and the extent of the chemical reduction of N2O can be increased by increasing the amount of NH3 added.
  • "*" indicates a process sub-step which was previously only incompletely carried out in a similar process sub-step, with the process sub-step marked with "*" subsequently continuing the process sub-step which was previously only incompletely carried out, but possibly in a different reaction zone or a different catalyst bed.
  • the result achieved at the end of all process sub-steps is not quantitatively determined.
  • the exhaust gas treatment system comprises at least one feed point for reducing agents.
  • the exhaust gas treatment system can comprise several feed points for reducing agents.
  • the type of introduction of the reducing agents into the exhaust gas stream to be treated can be freely designed according to the invention, as long as this is in the flow direction upstream of the N 2 O reduction catalyst or NO X -reduction catalyst.
  • the reducing agent can be introduced in the form of a gas or a liquid or aqueous solution that evaporates in the exhaust gas stream to be treated.
  • the feed is made through a suitable device, such as a corresponding pressure valve or appropriately designed nozzles, which lead into a mixer for the exhaust gas stream to be treated and the supplied reducing agent.
  • the feed and introduction into the exhaust gas can be carried out separately or together.
  • the supply and distribution of the reducing agents for NOX and possibly N2O to the one or more reaction zones (catalyst beds) preferably takes place via a multiply branched pipe system provided with a large number of openings or nozzles, which is arranged in the flow direction of the exhaust gas upstream of the respective reaction zone (catalyst bed), i.e. the packing of the catalyst honeycombs or honeycomb body modules.
  • the distributors are preferably designed in the form of grids, so-called “grids”, or concentrically interconnected circles, which extend as far as possible over the cross-sectional area of the exhaust gas channel or the inflow area of the reaction zone (catalyst bed).
  • the specific design and dimensioning of these distributors, including suitable outlet nozzles, is part of the specialist knowledge in catalytic exhaust gas purification technology and is widely used, for example, in the exhaust gas purification of coal-fired power plants.
  • the exhaust gas treatment system according to the invention can comprise a single reaction zone.
  • the catalyst used in this single reaction zone serves as an N2O decomposition catalyst and/or N2O reduction catalyst as well as a NOX reduction catalyst.
  • steps (d) and (e) of the method according to the invention take place essentially simultaneously within this reaction zone.
  • the kinetics of the individual reactions can be quite different.
  • the chemical reduction of NO X with NH 3 as a reducing agent can be carried out much faster than the chemical reduction of N2O with NH3. If NOX and N2O are present in the mixture and NH3 is fed in as a reducing agent, different reactions take place in the front section of the single reaction zone than in the rear section of the single reaction zone. In the front section, the chemical reduction of NO predominantly takes place due to the faster kinetics.
  • the exhaust gas treatment system can comprise a plurality of reaction zones, which is preferred according to the invention. If a plurality of reaction zones are comprised, these are preferably arranged one after the other, i.e. the exhaust gas flows through them one after the other, first the first reaction zone and then the second reaction zone and optionally then the third reaction zone.
  • the reaction zones are each catalyst beds spatially separated from one another.
  • the exhaust gas passes through the steps of the process according to the invention in one of the following orders: (i) (a) ⁇ (b) ⁇ (c) ⁇ (d1) ⁇ (e); wherein preferably step (d1) takes place in a first reaction zone; and step (e) takes place in a second reaction zone; (ii) (a) ⁇ (b) ⁇ (c) ⁇ (e) ⁇ (d2); wherein preferably step (e) takes place in a first reaction zone; and step (d2) takes place in a second reaction zone; (iii) (a) ⁇ (b) ⁇ (c) ⁇ (e) ⁇ (d2) ⁇ (d1); wherein preferably step (e) takes place in a first reaction zone; step (d2) takes place in a second reaction zone; and step (d1) takes place in a third reaction zone; (iv) (a) ⁇ (b) ⁇ (c) ⁇ (e) ⁇ (d1)+(d2)
  • reaction zones it is also possible for several reaction zones to be implemented by a single catalyst bed.
  • Two reaction zones on a common catalyst bed can be formed in particular by feeding in reducing agent in the middle (or another position along the longitudinal extent) of the catalyst bed. Upstream of the feed point, no reducing agent is then present, so that steps (d2) and (e) of the process according to the invention cannot take place in the absence of reducing agent.
  • the decomposition of N2O then essentially takes place upstream in accordance with step (d1) (first reaction zone). Downstream of the feed point, reducing agent is present, so that steps (d2) and (e) of the process according to the invention can take place, optionally superimposed by step (d1) of the process according to the invention (second reaction zone).
  • the exhaust gas treatment system comprises a first reaction zone and a second reaction zone. It is possible for further reaction zones to be present.
  • the first reaction zone and the second reaction zone are spatially separated from one another. In this case, they are preferably separate catalyst beds.
  • the temperature in the first reaction zone is higher than the temperature in the second reaction zone (in the second catalyst bed).
  • the temperature in the first reaction zone is at least 450°C, more preferably at least 500°C, even more preferably at least 550°C, most preferably at least 600°C and in particular at least 650°C.
  • the temperature in the second reaction zone (in the second catalyst bed) is at most 600°C, more preferably at most 550°C, even more preferably at most 500°C, most preferably at most 450°C and in particular at most 400°C.
  • the temperature in the first reaction zone (in the first catalyst bed) is relatively higher by at least 20°C, more preferably by at least 40°C, even more preferably by at least 60°C, most preferably by at least 80°C and in particular by at least 100°C than the temperature in the second reaction zone (in the second catalyst bed).
  • the temperature in the second reaction zone (in the second catalyst bed) is relatively higher than the temperature in the first reaction zone (in the first catalyst bed) by at least 20°C, more preferably by at least 40°C, even more preferably by at least 60°C, most preferably by at least 80°C and in particular by at least 100°C.
  • the temperature in the first reaction zone (in the first catalyst bed) is relatively higher than the temperature in the second reaction zone (in the second catalyst bed) by at least 120°C, more preferably by at least 140°C, even more preferably by at least 160°C, most preferably by at least 180°C and in particular by at least 200°C.
  • the temperature in the second reaction zone (in the second catalyst bed) is relatively higher than the temperature in the first reaction zone (in the first catalyst bed) by at least 120°C, more preferably by at least 140°C, even more preferably by at least 160°C, most preferably by at least 180°C and in particular by at least 200°C.
  • the temperature of the exhaust gas at the inlet into the first reaction zone (into the first catalyst bed) is at least 400°C, more preferably at least 425°C, even more preferably at least 450°C, most preferably at least 500°C.
  • the temperature of the exhaust gas at the outlet from the second reaction zone (from the second catalyst bed) is at most 600°C, more preferably at most 550°C, even more preferably at most 500°C.
  • the temperature of the exhaust gas at the inlet into the first reaction zone (into the first catalyst bed) is relatively higher by at least 20K, more preferably by at least 40K, even more preferably by at least 60K, most preferably by at least 80K and in particular by at least 100K than the temperature of the exhaust gas at the inlet into the second reaction zone (into the second catalyst bed).
  • the temperature of the exhaust gas at the inlet into the second reaction zone (into the second catalyst bed) is relatively higher by at least 10K, more preferably by at least 20K, even more preferably by at least 30K, most preferably by at least 40K and in particular by at least 50K than the temperature of the exhaust gas at the inlet into the first reaction zone (into the first catalyst bed).
  • the temperature in the first reaction zone (in the first catalyst bed) is relatively higher by at least 120K, more preferably by at least 140K, even more preferably by at least 160K, most preferably by at least 180K and in particular by at least 200K than the temperature in the second reaction zone (in the first catalyst bed).
  • the temperature in the second reaction zone (in the second catalyst bed) is relatively higher than the temperature in the first reaction zone (in the first catalyst bed) by at least 120K, more preferably by at least 140K, even more preferably by at least 160K, most preferably by at least 180K and in particular by at least 200K.
  • the first reaction zone and the second reaction zone are spatially connected to one another. In this case, it is preferably a common catalyst bed, with external influences causing a division into reaction zones, in particular by the location of the feed of reducing agent, so that reducing agent is not present equally everywhere on the catalyst bed.
  • the first reaction zone and the second reaction zone are preferably arranged in a common container.
  • the temperature of the exhaust gas in the first reaction zone and in the second reaction zone is each independently of one another at most 500°C, preferably it is each independently of one another in the range from 350 to 450°C.
  • the space velocity in the first reaction zone is greater than the space velocity in the second reaction zone.
  • the space velocity in the first reaction zone is at least a factor of 1.2, more preferably at least a factor of 1.4, even more preferably at least a factor of 1.6, most preferably at least a factor of 1.8, and in particular at least a factor of 2.0 greater than the space velocity in the second reaction zone.
  • the space velocity in the second reaction zone is greater than the space velocity in the first reaction zone.
  • the space velocity in the second reaction zone is at least a factor of 1.5, more preferably at least a factor of 2.0, even more preferably at least a factor of 3.0, most preferably at least a factor of 5.0, and in particular at least a factor of 10.0 greater than the space velocity in the first reaction zone.
  • "space velocity" is to be understood as the quotient of the volume flow of the gas mixture passed through the catalyst bed (measured at 0 °C and 1.014 bara and usually given in Nm3 ⁇ h-1) based on the volume of the catalyst or catalyst bed.
  • the exhaust gas has a temperature of at least 300°C, more preferably at least 350°C, even more preferably at least 400°C, most preferably at least 425°C, and in particular at least 450°C when entering the exhaust gas treatment system.
  • the exhaust gas has a temperature of at least 500°C, more preferably at least 550°C, even more preferably at least 600°C, most preferably at least 625°C, and in particular at least 650°C, when entering the exhaust gas treatment system.
  • the exhaust gas has a temperature of at most 825°C, more preferably at most 800°C, even more preferably at most 775°C, most preferably at most 750°C, and in particular at most 725°C, when entering the exhaust gas treatment system.
  • the exhaust gas has a temperature of at most 700°C, more preferably at most 650°C, even more preferably at most 600°C, most preferably at most 550°C, and in particular at most 500°C, when entering the exhaust gas treatment system.
  • the exhaust gas has a pressure of at most 1.4 bara, preferably of at most 1.3 bara, more preferably of at most 1.2 bara when it enters the exhaust gas treatment system.
  • the exhaust gas has a negative pressure when it enters the exhaust gas treatment system, preferably of about -5 mbar. This has the advantage that in the event of any leaks, no gas is released into the environment.
  • the exhaust gas has an oxidation level of NOX of at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, and in particular at least 50% when it enters the exhaust gas treatment system.
  • the exhaust gas has an oxidation level of NO of at least 10% when it enters the exhaust gas treatment system.
  • X of at most 90%, more preferably at most 80%, even more preferably at most 70%, most preferably at most 60%, and in particular at most 50%.
  • the degree of oxidation can also be significantly lower, with the degree of oxidation decreasing with increasing combustion temperature.
  • the exhaust gas has an oxidation degree of NO when entering the exhaust gas treatment plant. X of at most 15%, more preferably at most 12.5%, even more preferably at most 10%, most preferably at most 7.5%, and in particular at most 5.0%.
  • the exhaust gas at the entry into the exhaust gas treatment plant has a content of O 2 of less than 2.0 vol.%.
  • the exhaust gas at the entry into the exhaust gas treatment plant has a content of O 2 of more than 4.0 vol.%.
  • the content of N 2 O in the exhaust gas This can be done in different ways, namely by (d 1 ) Decomposition of N 2 O on an N 2 O decomposition catalyst and/or by (d2) chemical reduction of N2O with reducing agent on a N2O reduction catalyst. Step (d) of the process according to the invention is carried out in the exhaust gas treatment plant.
  • step (d) comprises reducing the content of N 2 O in the exhaust gas by (d1) decomposition of N2O on an N2O decomposition catalyst.
  • the N2O decomposition catalyst comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL.
  • the N2O decomposition catalyst is a ⁇ X-sensitive N2O decomposition catalyst in the sense of the invention, which has already been described in more detail above.
  • the exhaust gas preferably first passes through step (e), i.e. the NOX content in the exhaust gas is first reduced, preferably quantitatively, by chemical reduction of NOX with reducing agent on a NOX reduction catalyst, before the exhaust gas then comes into contact with the NOX-sensitive N2O decomposition catalyst.
  • the N2O decomposition catalyst is preferably arranged in a radial basket through which the flow is axial.
  • the N2O decomposition catalyst is preferably particulate and comprises at least 50 particles.
  • step (d) comprises reducing the N2O content in the exhaust gas by (d2) chemical reduction of N2O with reducing agent on a N2O reduction catalyst; preferably where the N 2 O reduction catalyst comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL.
  • the N 2 O reduction catalyst is arranged in a radial basket through which the flow is axial.
  • the N 2 O reduction catalyst is particulate and comprises at least 50 particles.
  • step (d) comprises reducing the content of N 2 O in the exhaust gas - both by (d 1 ) Decomposition of N 2 O on an N 2 O decomposition catalyst; preferably wherein the N 2 O decomposition catalyst comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably a zeolite loaded with iron; even more preferably an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL; - thus also by (d 2 ) chemical reduction of N 2 O with reducing agent at a N 2 O-reduction catalyst; preferably wherein the N 2 O reduction catalyst comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or
  • the reducing agent in step (d2) is selected from NH3, hydrocarbons, CO, H2 and mixtures thereof; preferably NH3.
  • the reducing agent in step (d2) is NH3, which is preferably used in an amount of 0.5 to 2.0 molar proportions, more preferably in an amount of 0.8 to 1.8 molar proportions, based on a molar proportion of N2O to be chemically reduced, i.e. based on the amount of N2O at the inlet into the catalyst bed of the N2O reduction catalyst.
  • the reducing agent in step (d2) is NH3, which is preferably used in an amount of 0.5 to 2.0 molar proportions, more preferably in an amount of 0.8 to 1.8 molar proportions, based on the molar amount of N2O in the exhaust gas at the inlet into the catalyst bed of the N2O reduction catalyst. This amount is additive to the amount of NH3 possibly required for NOX reduction, provided that step (e) also takes place in the catalyst bed of the N2O reduction catalyst.
  • the reducing agent is a hydrocarbon or a mixture of several hydrocarbons, which is preferably present in an amount of 0.2 to 1.0 molar proportions, more preferably 0.2 to 0.7 molar proportions, based on the molar amount of N2O in the exhaust gas at the inlet into the catalyst bed of the N 2 O reduction catalyst. This amount is also additive to the possibly required amount of NH 3 to NO X -reduction, provided that step (e) also takes place in the catalyst bed of the N 2 O reduction catalyst.
  • the reducing agent can also already be present in the exhaust gas, e.g. as residual combustion gases and/or their oxidation products.
  • step (e) of the process according to the invention the content of NO X (i.e. NO and NO 2 ) in the exhaust gas. This is done by chemical reduction of NO X with reducing agent on a NO X -reduction catalyst. Step (e) of the process according to the invention is also carried out in the exhaust gas treatment plant.
  • the NO X -Reduction catalyst is a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably a zeolite loaded with iron; even more preferably an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL.
  • the NOX reduction catalyst is preferably arranged in a radial basket through which the flow is axial.
  • the NOX reduction catalyst is preferably particulate and comprises at least 50 particles.
  • the reducing agent in step (e) is preferably selected from NH3, hydrocarbons, CO, H2 and mixtures thereof; preferably NH3.
  • the reducing agent in step (e) is preferably NH3, which is used in an amount of 0.9 to 2.5 molar proportions, preferably 1.0 to 1.4 molar proportions, more preferably 1.0 to 1.2 molar proportions, based on a molar proportion of NOX to be chemically reduced.
  • the reducing agent in step (d2) is the same as the reducing agent in step (e); preferably NH3.
  • nitrogen-containing reducing agents are also suitable in steps (d2) and/or (e) of the process according to the invention, for example hydrogen compounds of nitrogen, such as azanes, hydroxyl derivatives of azanes, and also amines, oximes, carbamates, urea or urea derivatives.
  • nitrogen such as azanes, hydroxyl derivatives of azanes, and also amines, oximes, carbamates, urea or urea derivatives.
  • azanes are hydrazine and very particularly ammonia.
  • hydroxyl derivatives of azanes are hydroxylamine.
  • amines are primary aliphatic amines, such as methylamine.
  • An example of carbamates is ammonium carbamate.
  • urea derivatives are N,N'-substituted ureas, such as N,N'-dimethylurea.
  • the exhaust gas treatment system comprises a first reaction zone and a second reaction zone arranged behind it, through which the exhaust gas flows one after the other; wherein reducing agent is added to the exhaust gas before the first reaction zone; wherein firstly in the first reaction zone the content of NOX in the exhaust gas is reduced by chemical reduction of NOX with reducing agent on a NOX reduction catalyst (step (e)), (DeNO X -level); optionally the N content 2 O in the exhaust gas by decomposition of N 2 O on an N 2 O decomposition catalyst (step (d 1 )) and/or by chemical reduction of N 2 O with reducing agent at a N 2 O
  • the NOX reduction catalyst in the first reaction zone comprises a conventional, preferably non-zeolitic SCR catalyst, e.g. based on V2O5-WO3-/TiO2.
  • the temperature of the exhaust gas on entry into the first reaction zone is at most 400°C, preferably at most 350°C.
  • the N2O decomposition catalyst in the second reaction zone comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL.
  • the temperature of the exhaust gas on entry into the second reaction zone is in the range from 300 to 550°C, preferably 350 to 500°C.
  • the exhaust gas after leaving the first reaction zone and before entering the second reaction zone has a content of NO X in the range of 0 to 200 ppmv, preferably 1 to 200 ppmv, and a content of N 2 O in the range of 200 to 2000 ppmv.
  • the exhaust gas treatment system also comprises a first reaction zone and a second reaction zone arranged behind it, through which the exhaust gas flows one after the other; reducing agent is added to the exhaust gas before the first reaction zone; whereby in the first reaction zone the NO content X in exhaust gases by chemical reduction of NO X with reducing agent on a NO X -reduction catalyst; (step (e)) (DeNO X -level); optionally the N content 2 O in the exhaust gas by decomposition of N 2 O on an N 2 O decomposition catalyst (step (d 1 )) and/or by chemical reduction of N 2 O is reduced with reducing agent on a N2O reduction catalyst (step (d2)); optionally, further reducing agent is added to the exhaust gas before the second reaction zone; and subsequently, in the second reaction zone, the content of N 2 O in the exhaust gas by decomposition of N 2 O on an N 2 O decomposition catalyst (step (d 1 ))
  • the NOX reduction catalyst in the first reaction zone comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL.
  • the temperature of the exhaust gas on entry into the first reaction zone is at least 300°C, more preferably at least 350°C, even more preferably at least 400°C.
  • the temperature of the exhaust gas when entering the first reaction zone is at most 600°C, more preferably at most 550°C.
  • the N2O decomposition catalyst in the second reaction zone comprises a NOX-sensitive N2O decomposition catalyst in the sense of the invention, which has already been described in more detail above.
  • the temperature of the exhaust gas when entering the second reaction zone is at least 300°C, more preferably at least 350°C, even more preferably at least 400°C.
  • the temperature of the exhaust gas when entering the second reaction zone is at most 600°C, more preferably at most 550°C.
  • the exhaust gas after leaving the first reaction zone and before entering the second reaction zone has a NO content X of not more than 20 ppmv, more preferably not more than 10 ppmv, even more preferably not more than 5 ppmv and a content of N 2 O in the range of 200 to 2000 ppmv.
  • the exhaust gas treatment system comprises a first catalyst bed and a second catalyst bed spatially separated therefrom; the first catalyst bed being upstream of the second catalyst bed in the flow direction of the exhaust gas is arranged; optionally and preferably upstream of the first catalyst bed, a first device with a first control valve for metering NH 3 into the exhaust gas; wherein downstream of the first catalyst bed and upstream of the second catalyst bed a second device with a second control valve for metering NH 3 in the exhaust gas, with which further NH3 is metered into the exhaust gas; wherein both the first catalyst bed and the second catalyst bed each contain an iron-loaded zeolite catalyst; wherein (i) in the first catalyst bed (d 1 ) N 2 O is decomposed; and (e) NO X incomplete with NH 3 is chemically reduced, optionally and preferably at least a portion of the NH 3 from incomplete combustion of NH 3 in
  • the catalytic decomposition of N2O in the first catalyst bed is co-catalyzed by NOX present in the exhaust gas.
  • the incomplete chemical reduction of NOX with NH3 in the first catalyst bed leads to a predetermined residual content of NOX, which is sufficient to cause a co-catalytic effect on the decomposition of N2O in the first catalyst bed. Since in the first catalyst bed the chemical reduction of NOX with NH3 typically proceeds significantly faster than the chemical reduction of N2O with NH3 and not the entire amount of NOX is chemically reduced in the first catalyst bed, the extent of the chemical reduction of N2O with NH3 that may occur in parallel in the first catalyst bed is typically negligible.
  • additional NH3 is metered into the exhaust gas via the first device for NOX reduction; preferably under feedback control, i.e. a certain value for the concentration of NOX at the outlet of the first catalyst bed is specified as a target value (setpoint value) and the actual concentration of NOX at the outlet of the first catalyst bed is measured (actual value) and in the event of a difference between the setpoint value and the actual value (control difference), the control level of the first control valve is changed in order to minimize the difference.
  • the setpoint value of the NOX concentration at the outlet of the first catalyst bed and thus the amount of additional NH3 is selected such that the residual concentration of NOX at the outlet of the first catalyst bed is at most 1000 ppmv, preferably at most 500 ppmv, more preferably at most 100 ppmv.
  • the setpoint value of the NOX concentration at the outlet of the first catalyst bed and thus the amount of additional NH3 is selected so that the residual concentration of NO X at the outlet of the first catalyst bed is at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 40 ppmv.
  • the expected specific consumption of NH 3 for the chemical reduction of NO X in the first catalyst bed is typically in the range of 0.9 to 1.1 mol NH 3 per mole reduced NO X and is therefore significantly smaller than the expected specific (mol/mol) consumption of NH 3 in the second catalyst bed.
  • the temperature of the exhaust gas at the outlet from the first catalyst bed is in the range from 400 to 550°C.
  • the exhaust gas at the outlet from the first catalyst bed has a pressure which is greater than atmospheric pressure, i.e. ⁇ 1.0 bara, but at most 1.2 bara, more preferably at most 1.1 bara.
  • the exhaust gas at the outlet from the first catalyst bed has an oxidation degree of NOX of at least 5.0%, preferably at least 7.5%, more preferably at least 10%, even more preferably at least 12.5%, most preferably at least 15%, and in particular at least 17.5%.
  • the exhaust gas at the outlet from the first catalyst bed has an oxidation degree of NOX in the range from 30 to 50%.
  • the exhaust gas at the outlet from the first catalyst bed has an oxidation level of NOX in the range from 15 to 35%, preferably 15 to 30%.
  • the exhaust gas at the outlet from the first catalyst bed has an oxidation level of NOX in the range from 10 to 20%.
  • the exhaust gas at the outlet from the first catalyst bed has an oxidation level of NOX in the range from 5 to 15%.
  • residual N2O is broken down in the second catalyst bed to a residual concentration of N2O at the outlet of the second catalyst bed of at most 20 ppmv, more preferably at most 10 ppmv, even more preferably at most 5 ppmv, most preferably at most 2 ppmv.
  • residual NOX in the second catalyst bed is broken down to a residual concentration of NOX at the outlet of the second catalyst bed of at most 20 ppmv, more preferably at most 10 ppmv, even more preferably at most 5 ppmv, most preferably at most 2 ppmv.
  • the further NH3 is metered in using the second device under feedforward control, i.e.
  • the concentrations of NOX and optionally preferably of N2O are measured at the outlet of the first catalyst bed or optionally at the inlet to the second catalyst bed; taking into account the amount of exhaust gas entering the second catalyst bed, the amount of NH3 required for NOX reduction and, optionally, preferably, the sum of the amount of NH3 required for NOX reduction and N2O reduction is calculated using stored ratios, i.e., for example, molar ratios (mol/mol) of NH3/NOX and, optionally, preferably, of NH3//N2O or factors derived therefrom; and the calculated result (control variable) is used to change the control level of the second control valve in order to achieve the required amount of NH 3 to add doses.
  • stored ratios i.e., for example, molar ratios (mol/mol) of NH3/NOX and, optionally, preferably, of NH3//N2O or factors derived therefrom.
  • the molar NH 3 -Concentration [NH 3 ] of the exhaust gas at the inlet to the second catalyst bed is preferably in the range of the sum of 0.7 x [N 2 O] and 1.0 x [NO X ] to the sum of 4.0 x [N 2 O] and 2.0 x [NO X ], preferably in the range of the sum of 1.0 x [N 2 O] and 1.1 x [NO X ] to the sum of 3.0 x [N 2 O] and 1.6 x [NO X ], more preferably in the range from the sum of 1.5 x [N2O] and 1.2 x [NOX] to the sum of 2.5 x [N2O] and 1.4 x [NOX], where [N2O] is the molar concentration of N2O and [NOX] is the molar concentration of NOX in the exhaust gas at the inlet to the second catalyst bed.
  • a molar ratio of NH3/NOX in the range of 1.0 to 2.0; preferably 1.1 to 1.6; more preferably 1.2 to 1.4 is selected.
  • a molar ratio of NH3/N2O in the range of 0.7 to 4.0; preferably 1.0 to 3.0; more preferably 1.5 to 2.5 is selected.
  • the additional NH3 is not dosed with the second device under feedback control, since the aim is to achieve the most complete chemical reduction of NOX in the second catalyst bed, i.e. no or only very low residual concentrations of NOX and N2O result, which would be difficult to use as control variables in terms of control technology.
  • the amount of catalyst and the amount of additional NH3 are preferably selected such that the molar ratio of NOX/N2O at the outlet of the first catalyst bed is at least 5, more preferably at least 10, even more preferably at least 20.
  • the space velocity of the first catalyst bed is preferably in the range from 5,000 h-1 to 100,000 h-1, more preferably 10,000 h-1 to 50,000 h-1, even more preferably 15,000 h-1 to 45,000 h-1.
  • the metering of NH3 into the second catalyst bed via the second device can preferably be carried out solely in relation to the amount of NO entering.
  • the temperature of the exhaust gas upon entry into the first catalyst bed is at least 400°C, more preferably at least 425°C, even more preferably at least 450°C.
  • the temperature of the exhaust gas upon entry into the first catalyst bed is at most 550°C, more preferably at most 525°C, even more preferably at most 500°C.
  • the temperature can be adjusted by measures which are known to experts, in particular the design of heat exchangers and conditions for the combustion of NH 3
  • the inlet temperature of the exhaust gas into the first catalyst bed is preferably selected such that the temperature of the exhaust gas at the outlet of the second catalyst bed is at most 600°C, more preferably at most 550°C, even more preferably at most 520°C.
  • the space velocity of the second catalyst bed is preferably in the range from 5,000 h-1 to 100,000 h-1, more preferably 10,000 h-1 to 50,000 h-1, even more preferably 15,000 h-1 to 45,000 h-1.
  • ⁇ the pressure of the exhaust gas on entry into the first catalyst bed is at most 5 bara, more preferably at most 4 bara, even more preferably at most 1.3 bara, most preferably at most 1.2 bara and in particular at most 1.1 bara;
  • ⁇ the content of H 2 O in the exhaust gas upon entry into the first catalyst bed is at least 5 vol.%, more preferably at least 10 vol.%, even more preferably at least 15 vol.%, most preferably at least 20 vol.% and in particular at least 25 vol.%;
  • ⁇ the content of NO X in the exhaust gas upon entry into the first catalyst bed is at least 500 ppmv, more preferably at least 1000 ppmv, even more preferably at least 1500 ppmv, most preferably at least 2000 ppmv, and in particular at least 2500 ppmv;
  • ⁇ the N2O content in the exhaust gas upon entry into the first catalyst bed is at most ⁇ 500 ppmv, more
  • the NO is X -Oxidation level (molar ratio of NO 2 /(NO + NO 2 )) before entering the first catalyst bed due to the upstream NH 3 -Combustion at very high temperatures and the slow establishment of equilibrium in the gas phase when cooling the exhaust gas in the heat exchanger(s) that may be connected, is expected to be less than 5% and is therefore well below the thermodynamic equilibrium applicable for the inlet temperature into the first catalyst bed.
  • this is very disadvantageous for an efficient chemical reduction of NO X , as this only removes a small proportion of the NO present in the exhaust gas X can be reduced in accordance with an almost SCR and a large part of the NO X or the remaining NO must be broken down according to the significantly slower normal SCR.
  • the inlet temperature of the exhaust gas into the second catalyst bed is preferably at least 400°C, more preferably at least 425°C, even more preferably at least 450°C, then the excess NH dosed within the limits of the invention 3 through the residual oxygen content of the exhaust gas to N 2 and H 2 O oxidized.
  • All these advantages can be achieved by using classical V 2 O 5 /TiO 2 -based SCR catalysts, such as those typically used for denitrification of exhaust gases from natural gas-fired reformers, cannot be realized in a single or multi-stage arrangement. For stability reasons, these classic SCR catalysts typically cannot be operated at temperatures above 400°C, which limits the achievable reaction rates of the degradation reaction.
  • the second device with a second control valve for metering NH3 into the exhaust gas is omitted, whereby the spatial separation of the first catalyst bed from the second catalyst bed is preferably omitted - there is then in fact only one common catalyst bed, whereby a first device with a first control valve for metering NH3 into the exhaust gas is preferably arranged upstream of this common catalyst bed.
  • Additional NH3 is preferably metered into the exhaust gas via the first device; preferably under feedforward control, i.e.
  • the concentration of NOX, N2O and NH3 in the exhaust gas upstream of the common catalyst bed is measured; taking into account the amount of exhaust gas entering the common catalyst bed, the additional amount of NH3 still required is calculated; and the calculated result (control variable) is used to change the control level of the first control valve in order to meter in the amount of additional NH3 still required.
  • an NH3 oxidation catalyst is arranged downstream of the common catalyst bed in order to reduce possible NH3 slip.
  • step (a) the combustion of a mixture of CH 4 and NH 3 with air and/or oxygen to produce an exhaust gas which, in addition to NO X and N 2 O additional CO 2 , CO and HCN.
  • the first catalyst bed preferably takes on the additional function of catalytic cleavage of HCN by hydrolysis with water present in the exhaust gas into the products CO and NH 3 according to HCN + H 2 O ⁇ CO + NH 3
  • the resulting products CO and NH 3 can then subsequently with regard to NH 3 preferred to NE X -Reduction in the first catalyst bed and with regard to CO preferentially to N 2 O reduction in the second catalyst bed as a reducing agent for the removal of N 2 O and NE X in the exhaust gas.
  • HCN is to be limited or eliminated as a pollutant and greenhouse gas due to its toxicity, its longevity in the atmosphere and its absorption in the infrared.
  • the exhaust gas treatment system comprises a first reaction zone and a second reaction zone arranged behind it, through which the exhaust gas flows one after the other; wherein reducing agent is added to the exhaust gas between the first reaction zone and the second reaction zone; wherein firstly in the first reaction zone the content of N2O in the exhaust gas is reduced by decomposition of N2O on an N2O decomposition catalyst (step (d1)) (DeN2O stage); and wherein the NOX content in the exhaust gas is then reduced in the second reaction zone by chemical reduction of NOX with reducing agent on a NOX reduction catalyst (step (e)) (DeNOX stage); wherein optionally the N2O content in the exhaust gas is additionally further reduced by further decomposition of N2O on a N2O decomposition catalyst (step (d1)) and/or by chemical reduction of N2O with reducing agent on a N2O reduction catalyst (step (d2)).
  • no reducing agent is added to the exhaust gas before the first reaction zone.
  • Such a process is particularly preferred according to the invention. It makes it possible to initially reduce the relative NO content without consuming reducing agent. X and N 2 O. While the absolute content of NO X in the first reaction zone remains practically unchanged, the content of N 2 O in the exhaust gas is reduced by decomposition. This can be done to the extent required to set the desired relative content of NOX and N2O.
  • the amount of N2O decomposition catalyst is preferably not chosen to be so large that a quantitatively complete reduction in the content of N 2 O in the exhaust gas is removed by decomposition (0 ppmv), but a compromise is found between the decomposition rate and the dimensioning of the N 2 O decomposition catalyst.
  • the N 2 O decomposition catalyst in the first reaction zone is a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL.
  • the N 2 O decomposition catalyst in the first reaction zone a NO X -sensitive N 2 O decomposition catalyst in the sense of the invention, which has already been described above.
  • the NOX reduction catalyst in the second reaction zone comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL.
  • the first reaction zone and the second reaction zone are operated at different temperature levels.
  • the N2O decomposition catalyst in the first reaction zone comprises a NOX-sensitive N2O decomposition catalyst; wherein the temperature of the exhaust gas in the first reaction zone is preferably at least 450°C, more preferably at least 500°C, even more preferably at least 550°C, most preferably at least 600°C; and - the NOX reduction catalyst in the second reaction zone is a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the structure type MFI, BEA, FER, MOR, FAU and/or MEL; wherein the temperature of the exhaust gas in the second reaction zone is preferably at most 550°C, more preferably at most 500°C, even more preferably at most 450°C, most preferably at most 400°C; and wherein preferably in the second reaction zone, in addition to
  • the space velocity in the first reaction zone is adjusted so that in the first reaction zone a reduction of the content of N 2 O in the exhaust gas by at most 95%, preferably by at most 90%, more preferably by at most 85%, based on the content of N2O in the exhaust gas upon entry into the first reaction zone.
  • the content of N 2 O in the exhaust gas after leaving the first reaction zone and before entering the second reaction zone at least 20 ppmv, preferably at least 40 ppmv, more preferably at least 60 ppmv, most preferably at least 80 ppmv and especially at least 100 ppmv.
  • the content of N is 2 O in the exhaust gas after leaving the first reaction zone and before entering the second reaction zone is at most 400 ppmv, more preferably at most 300 ppmv, even more preferably at most 200 ppmv, most preferably at most 100 ppmv and in particular at most 50 ppmv.
  • the space velocity in the second reaction zone is set such that in the second reaction zone there is a further reduction in the N2O content in the exhaust gas by at least 30%, preferably by at least 40%, more preferably by at least 50%, based on the N2O content in the exhaust gas when entering the second reaction zone.
  • the further reduction in the N2O content in the second reaction zone can take place both by decomposition on an N2O decomposition catalyst (step (d1)) and by chemical reduction with reducing agent on an N2O reduction catalyst (step (d2)).
  • a further reduction in the N2O content in the exhaust gas takes place by chemical reduction of N2O with reducing agent on an N2O reduction catalyst (step (d2)).
  • a reduction in the NOX content takes place by chemical reduction with reducing agent on an NOX reduction catalyst. This reduction typically has rapid kinetics and according to the invention preferably proceeds practically quantitatively.
  • the exhaust gas is cooled in at least one heat exchanger which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas.
  • a single heat exchanger is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, in which the cooling of the exhaust gas takes place.
  • at least two heat exchangers are arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, in which the exhaust gas is cooled one after the other (see Figures 2, 3 and 4).
  • At least three heat exchangers are arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, in which the exhaust gas is cooled one after the other (see Figure 5).
  • at least four heat exchangers are arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, in which the exhaust gas is cooled one after the other.
  • at least five heat exchangers are arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, in which the exhaust gas is cooled one after the other (see Figure 6).
  • the cooling of the exhaust gas in the at least one heat exchanger takes place by releasing heat from the exhaust gas to a heat transfer medium.
  • the heat transfer medium used is preferably a heat transfer medium selected from the group consisting of water, water vapor, combustion air, NH 3 and combinations thereof. Water or water vapor as a heat transfer medium is particularly preferred, among other things for reasons of safety.
  • the cooling of the exhaust gas takes place in a first exhaust gas/H2O heat exchanger, which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas.
  • the H2O is heated in the first exhaust gas/H2O heat exchanger by absorbing heat from the exhaust gas.
  • the heated H2O which can be liquid and/or water vapor, is preferably used to heat NH3.
  • an H2O/NH3 heat exchanger is preferably arranged downstream of the first exhaust gas/H2O heat exchanger in the flow direction of the H2O, in which NH3 is heated by absorbing heat from the H2O (see Figures 2-6).
  • the exhaust gas is cooled in a first exhaust gas/combustion air heat exchanger, which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas.
  • the combustion air is heated in the first exhaust gas/combustion air heat exchanger by absorbing heat from the exhaust gas.
  • the heated combustion air is preferably used to burn NH3 and H2 in the combustion device, which is arranged downstream of the first exhaust gas/combustion air heat exchanger in the flow direction of the combustion air (cf. Figures 2-6).
  • the exhaust gas is cooled - in a first exhaust gas/H 2 O heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, and - in a first exhaust gas/combustion air heat exchanger described above, which is also arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system; preferably downstream of the first exhaust gas/H 2 O heat exchanger (see Figures 2-6).
  • the exhaust gas in step (f) of the method according to the invention, is cooled - in a first exhaust gas/combustion air heat exchanger, which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, and - in a second exhaust gas/combustion air heat exchanger, which is arranged downstream of the first exhaust gas/combustion air heat exchanger in the flow direction of the exhaust gas.
  • the combustion air is heated in the first exhaust gas/combustion air heat exchanger and in the second exhaust gas/combustion air heat exchanger by absorbing heat from the exhaust gas.
  • the exhaust gas preferably flows first through the first exhaust gas/combustion air heat exchanger and then through the second exhaust gas/combustion air heat exchanger.
  • the combustion air first flows through the second exhaust gas/combustion air heat exchanger and then through the first exhaust gas/combustion air heat exchanger, which is why the first exhaust gas/combustion air heat exchanger is preferably arranged downstream of the second exhaust gas/combustion air heat exchanger in the flow direction of the combustion gas.
  • the heated combustion air is used to burn NH3 and H2 in the combustion device, which is arranged downstream of the first exhaust gas/combustion air heat exchanger in the flow direction of the combustion air (see Figures 5 and 6).
  • step (f) of the method according to the invention the cooling of the exhaust gas takes place - in a first exhaust gas/combustion air heat exchanger described above, which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, - in a first exhaust gas/H2O heat exchanger described above, which is arranged downstream of the first exhaust gas/combustion air heat exchanger in the flow direction of the exhaust gas, and - in a second exhaust gas/combustion air heat exchanger described above, which is arranged downstream of the first exhaust gas/H2O heat exchanger in the flow direction of the exhaust gas (cf. Figures 4-6).
  • step (f) of the method according to the invention the cooling of the exhaust gas takes place in at least one exhaust gas/combustion gas heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, preferably downstream of the above-described first exhaust gas/combustion air heat exchanger, the above-described first exhaust gas/H 2 O heat exchanger, and/or the one described above second exhaust gas/combustion air heat exchanger.
  • the combustion gas is heated in the exhaust gas/combustion gas heat exchanger by absorbing heat from the exhaust gas.
  • the heated combustion gas is preferably used for combustion in the combustion device, which is arranged downstream of the exhaust gas/combustion gas heat exchanger in the flow direction of the combustion gas (see Figure 6).
  • the exhaust gas is cooled in at least one second exhaust gas/H 2 O heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, preferably downstream of the first exhaust gas/combustion air heat exchanger described above, the first exhaust gas/H2O heat exchanger described above, and/or the second exhaust gas/combustion air heat exchanger described above.
  • step (f) of the method according to the invention the cooling of the exhaust gas takes place - in a first exhaust gas/combustion air heat exchanger described above, which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, - in a first exhaust gas/H2O heat exchanger described above, which is arranged downstream of the first exhaust gas/combustion air heat exchanger in the flow direction of the exhaust gas, - in a second exhaust gas/combustion air heat exchanger described above, which is arranged downstream of the first exhaust gas/H2O heat exchanger in the flow direction of the exhaust gas, and - in an exhaust gas/combustion gas heat exchanger described above, which is arranged downstream of the second exhaust gas/combustion air heat exchanger in the flow direction of the exhaust gas (see Figure 6).
  • step (f) of the method according to the invention the cooling of the exhaust gas takes place - in a first exhaust gas/combustion air heat exchanger described above, which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, - in a first exhaust gas/H2O heat exchanger described above, which is arranged downstream of the first exhaust gas/combustion air heat exchanger in the flow direction of the exhaust gas, - in a second exhaust gas/combustion air heat exchanger described above, which is arranged downstream of the first exhaust gas/H 2 O heat exchanger, and - in a second exhaust gas/H 2 O heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the second exhaust gas/combustion air heat exchanger (see Figure 6).
  • step (f) of the method according to the invention the cooling of the exhaust gas takes place - in a first exhaust gas/combustion air heat exchanger described above, which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, - in a first exhaust gas/H2O heat exchanger described above, which is arranged downstream of the first exhaust gas/combustion air heat exchanger in the flow direction of the exhaust gas, - in a second exhaust gas/combustion air heat exchanger described above, which is arranged downstream of the first exhaust gas/H 2 O heat exchanger, - in an exhaust gas/combustion gas heat exchanger described above, which is arranged downstream of the second exhaust gas/combustion air heat exchanger in the flow direction of the exhaust gas, and - in a second exhaust gas/H2O heat exchanger described above, which is arranged downstream of the exhaust gas/combustion gas heat exchanger in the flow direction of the exhaust gas (see Figure 6).
  • the inlet temperature of the exhaust gas into the exhaust duct is therefore limited downwards by the preheating temperatures given up due to the requirements of the process in the tube reactor designed analogously to a primary reformer or possible pre-reactors (preferably adiabatic fixed bed reactors).
  • Heterogeneous catalysts achieve higher reaction rates at higher temperatures by accelerating diffusion and kinetics. However, their operation is often limited by their decreasing stability against deactivation at high temperatures.
  • this window is below the range in which operation leads to deactivation and loss of catalytic effectiveness.
  • Another criterion for evaluating efficient energy integration is therefore whether the inlet temperature of the exhaust gas into the exhaust gas treatment system is within this optimal window.
  • the third factor for evaluating the effectiveness of a configuration of the exhaust duct is the temperature of the exhaust gas entering the chimney. Together with the mass flow of the exhaust gas, it determines the loss of energy through the flow compared to the theoretical optimum, achieved at the dew point of water plus the required safety margin of 25 K.
  • the yield of H 2 should be as high as possible in order to increase the economic efficiency of the operation of the system. A high yield is typically directly linked to a low inlet temperature of the exhaust gas in the chimney.
  • the method according to the invention is preferably controlled.
  • at least one parameter is measured as the first measured variable, which is characteristic of the current operating state of the combustion system, preferably the combustion device.
  • This first measured variable or the parameter is preferably selected from the group consisting of combustion temperature and NH3 consumption of the combustion system, preferably the combustion device.
  • the combustion device in particular - NOX content in the exhaust gas; - degree of oxidation of the NOX in the exhaust gas; - N2O content in the exhaust gas; - content of other components in the exhaust gas, such as H2O, O2, and N2; - temperature of the exhaust gas; - pressure of the exhaust gas; and - volume flow of the exhaust gas; the process conditions can be optimized in order to achieve an efficient and economical reduction in the NO content.
  • X and N 2 O in the exhaust gas in particular - NOX content in the exhaust gas; - degree of oxidation of the NOX in the exhaust gas; - N2O content in the exhaust gas; - content of other components in the exhaust gas, such as H2O, O2, and N2; - temperature of the exhaust gas; - pressure of the exhaust gas; and - volume flow of the exhaust gas; the process conditions can be optimized in order to achieve an efficient and economical reduction in the NO content.
  • X and N 2 O in the exhaust gas in particular - NOX content in the exhaust gas
  • This is preferably second measured value or parameter selected from the group consisting of NO content X in the exhaust gas; degree of oxidation of NO X in exhaust gas; N content 2 O in the exhaust gas; content of other components in the exhaust gas, such as H 2 Oh, Oh 2 , and N 2 ; temperature of the exhaust gas; pressure of the exhaust gas; and volume flow of the exhaust gas.
  • At least one parameter which is characteristic of the current state of the exhaust gas at the outlet of the exhaust gas treatment system is measured as a third measured variable, either in addition to the first measured variable or instead of the first measured variable, and either in addition to the second measured variable or instead of the second measured variable, for the control of the method according to the invention.
  • This third measured variable or the parameter is preferably selected from the group consisting of NOX content in the exhaust gas; degree of oxidation of the NOX in the exhaust gas; N2O content in the exhaust gas; content of other components in the exhaust gas, such as H2O, O2, and N2; temperature of the exhaust gas; pressure of the exhaust gas; and volume flow of the exhaust gas.
  • the exhaust gas treatment system comprises a first reaction zone and a second reaction zone through which the exhaust gas flows one after the other, with reducing agent being fed in between the first reaction zone and the second reaction zone
  • at least one parameter is measured as a fourth measured variable, either in addition to the first measured variable or instead of the first measured variable, and either in addition to the second measured variable or instead of the second measured variable, and either in addition to the third measured variable or instead of the third measured variable, which is characteristic of the current state of the exhaust gas after leaving the first reaction zone and before entering the second reaction zone.
  • This fourth measured variable or the parameter is preferably selected from the group consisting of NOX content in the exhaust gas; degree of oxidation of the NOX in the exhaust gas; N2O content in the exhaust gas; content of other components in the exhaust gas, such as H2O, O2, and N2; temperature of the exhaust gas; pressure of the exhaust gas; and volume flow of the exhaust gas.
  • at least one manipulated variable is preferably changed to regulate or control the method according to the invention.
  • the method is therefore preferably regulated or controlled using the first measured variable and/or the second measured variable and/or the third measured variable and/or the fourth measured variable by specifically changing the manipulated variable (control variable), preferably by specifically changing the amount of reducing agent added.
  • control variable preferably by specifically changing the amount of reducing agent added.
  • the following are preferred: - the dimensioning of the exhaust gas treatment device; - the type, quantity and flow direction of the N 2 O decomposition catalyst and/or N 2 O reduction catalyst; - the type, quantity and flow direction of the NO X -reduction catalyst; - the type of reducing agent; - the pressure of the exhaust gas; - the position of the reducing agent feed; and - the arrangement of the first reaction zone and second reaction zone relative to one another are not manipulated variables, i.e. these parameters preferably remain constant during implementation of the method according to the invention. [0488] However, these parameters can be selected or set during the planning and design of the exhaust gas treatment system so that the method according to the invention can be regulated within wide limits.
  • Preferred manipulated variables (control variables) according to the invention are: - the amount of reducing agent; - if applicable, the temperature of the exhaust gas; and - if applicable, the temperature of the catalysts.
  • the exhaust gas leaves the exhaust gas treatment plant and has a residual NOX content of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, and in particular at most 2.5 ppmv.
  • the exhaust gas leaves the exhaust gas treatment plant and has a residual N 2 O of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, and in particular at most 2.5 ppmv.
  • a further aspect of the invention relates to a device comprising (i) a NH 3 Combustion plant, preferably comprising a combustion device for burning NH 3 and a NH 3 -Decomposition device for splitting NH 3 in N 2 and H 2 , and (ii) an exhaust gas treatment plant; wherein the device is configured to carry out the method according to the invention described above.
  • the device according to the invention is preferably a plant complex for producing pure hydrogen comprising - one (or more) NH 3 -Decomposition device(s) for the catalytic decomposition of NH 3 in N 2 and H 2 , preferably a reactor filled with catalyst; - a combustion device for directly or indirectly heating the NH3 decomposition device(s), preferably comprising a combustion chamber and at least one burner for burning a fuel with (atmospheric) oxygen, wherein the fuel contains NH3 or consists essentially thereof; - a device for purifying a product stream of the NH3 decomposition device, preferably by PSA; - an exhaust gas treatment system for purifying the exhaust gases of the combustion device comprising one or more catalyst beds for reducing NOX, optionally for N2O reduction and/or N2O decomposition, and preferably for oxidizing unreacted reducing agents and/or their incompletely oxidized reaction products (preferably a downstream catalyst bed with NH3 oxidation catalyst).
  • Sentence 1 A method for reducing the content of NOX and N2O in the exhaust gas of a combustion plant operated with NH3, the method comprising the following steps: (a) burning NH3 to operate the combustion plant, preferably a furnace, preferably comprising a combustion device and NH3 decomposition device, for catalytically decomposing NH3 into N2 and H2, to produce an exhaust gas which comprises N2, H2O, NOX and N2O and which leaves the combustion plant; (b) optionally and preferably cooling the exhaust gas in at least one heat exchanger which is arranged downstream of the combustion plant in the flow direction of the exhaust gas; (c) transferring the optionally cooled exhaust gas to an exhaust gas treatment plant; (d) reducing the content of N2O in the exhaust gas by (d1) decomposition of N2O on a N2O decomposition catalyst and/or (d2) chemical reduction of N2O with reducing agent on a N2O reduction catalyst; (d1) decomposition of N2O on a N2O decomposition
  • Sentence 2 The method according to sentence 1 for reducing the NO content X and N 2 O in the exhaust gas of a NH 3 and H 2 operated combustion plant, which is converted into a plant for the catalytic decomposition of NH 3 to N 2 and H 2 is integrated, the process comprising the following steps: (a) burning NH 3 and H 2 for operating the combustion plant (preferably in a combustion facility) to produce an exhaust gas which contains N 2 , H 2 O, NO X and N 2 O and leaves the combustion plant; (b) optionally and preferably cooling the exhaust gas in at least one heat exchanger which is arranged downstream of the combustion plant in the flow direction of the exhaust gas; (c) transferring the optionally cooled exhaust gas to an exhaust gas treatment plant which is arranged downstream of the combustion plant and optionally of the at least one heat exchanger in the flow direction of the exhaust gas; (d) reducing the content of N 2 O in the exhaust gas by (d 1 ) Decomposition of N 2 O on an N 2 O decomposition catalyst and/or (d 2
  • Sentence 3 The method according to one of the preceding sentences, wherein a single heat exchanger is arranged downstream of the combustion system in the flow direction of the exhaust gas, in which the cooling of the exhaust gas takes place.
  • Sentence 4 The method according to one of the preceding sentences, wherein at least two heat exchangers are arranged downstream of the combustion system in the flow direction of the exhaust gas, in which the cooling of the exhaust gas takes place one after the other.
  • Sentence 5 The method according to one of the preceding sentences, wherein at least three heat exchangers are arranged downstream of the combustion system in the flow direction of the exhaust gas, in which the cooling of the exhaust gas takes place one after the other.
  • Sentence 6 The method according to one of the preceding sentences, wherein in step (b) the cooling of the exhaust gas in the at least one heat exchanger takes place by releasing heat from the exhaust gas to a heat transfer medium, wherein NH3 is preferably used as the heat transfer medium, which is then subsequently fed to the catalytic decomposition in an NH3 decomposition device on an NH3 decomposition catalyst.
  • Sentence 7 The method according to one of the preceding sentences, wherein in step (b) the cooling of the exhaust gas in at least one first exhaust gas/NH 3 -heat exchanger, which is arranged downstream of the combustion plant in the flow direction of the exhaust gas.
  • Sentence 8 The method according to one of the preceding sentences, wherein in step (b) the cooling of the exhaust gas takes place - in a first exhaust gas/NH 3 -Heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the combustion plant, and - in a second exhaust gas/NH 3 -Heat exchanger, which is located in the flow direction of the exhaust gas downstream of the first exhaust gas/NH 3 -Heat exchanger is arranged.
  • Sentence 9 The method according to one of the preceding sentences, wherein in step (b) the cooling of the exhaust gas takes place - in a first exhaust gas/NH 3 -Heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the combustion plant, - in a second exhaust gas/NH 3 -Heat exchanger, which is located in the flow direction of the exhaust gas downstream of the first exhaust gas/NH 3 -heat exchanger is arranged, and - in a third exhaust gas/NH3 heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the second exhaust gas/NH3 heat exchanger.
  • Sentence 10 The method according to one of the preceding sentences, wherein the exhaust gas in step (b) is cooled to a temperature T2 in the range from 400 to 450°C, more preferably 400 to 420°C.
  • Sentence 11 The method according to one of the preceding sentences, wherein the N 2 O decomposition catalyst and/or the N 2 O reduction catalyst and/or the NO X -reduction catalyst independently comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably, independently, an iron-loaded zeolite of the MFI, BEA, FER, MOR, FAU and/or MEL type.
  • transition metal including lanthanide
  • Sentence 12 The process according to any one of the preceding sentences, wherein the N2O decomposition catalyst and the N2O reduction catalyst are made of the same material.
  • Sentence 13 The process according to any one of the preceding sentences, wherein the N2O decomposition catalyst and the NOX reduction catalyst are made of the same material.
  • Sentence 14 The process according to any one of the preceding sentences, wherein the N2O reduction catalyst and the NOX reduction catalyst are made of the same material.
  • Sentence 15 The process according to one of the preceding sentences, wherein the N2O decomposition catalyst, the N2O reduction catalyst and the NOX reduction catalyst are made of the same material.
  • Sentence 16 The process according to one of the preceding sentences, wherein in step (a) the combustion of NH3 does not take place on a catalyst.
  • Sentence 17 The process according to one of the preceding sentences, wherein the proportion of H2 in the mixture with NH3 is at most 80 mol%, more preferably at most 70 mol%, even more preferably at most 60 mol%, most preferably at most 50 mol%, and in particular at most 40 mol%.
  • Sentence 18 The process according to one of the preceding sentences, wherein the proportion of H 2 in a mixture with NH 3 at least 10 mol%, more preferably at least 20 mol%, even more preferably at least 30 mol%, most preferably at least 40 mol%, and especially at least 50 mol%.
  • Sentence 19 The process according to any one of the preceding sentences, wherein the molar ratio of H 2 : NH 3 in the mixture is in the range from 45:55 to 90:10, preferably 50:50 to 85:15, more preferably 55:45 to 80:20, even more preferably 60:40 to 75:25, most preferably 65:35 to 70:30.
  • Sentence 20 The process according to one of the preceding sentences, wherein the air ratio ⁇ is in the range from 0.9 to 1.7, more preferably 1.0 to 1.6, even more preferably 1.1 to 1.5, most preferably 1.2 to 1.4.
  • Sentence 21 The method according to one of the preceding sentences, wherein the combustion plant, preferably the furnace (preferably comprising combustion device and NH 3 -decomposition facility), into a plant for the thermal and/or catalytic decomposition of NH 3 in N 2 and H 2
  • Sentence 22 The process according to one of the preceding sentences, wherein the exhaust gas has a content of NO X which is greater than the content of N 2 O; preferably wherein the content of NO X at least twice as large, more preferably at least three times as large, even more preferably at least four times as large, most preferably at least seven times as large and in particular at least ten times as large as the N2O content.
  • Sentence 23 The process according to one of the preceding sentences, wherein the exhaust gas has a NO content which is greater than the N content. 2 O; preferably wherein the NO content is at least twice as high, more preferably at least three times as high, even more preferably at least four times as high, most preferably at least seven times as high and in particular at least ten times as high as the N2O content.
  • Sentence 24 The method according to one of the preceding sentences, wherein the exhaust gas has an NO2 content which is greater than the N2O content; preferably wherein the NO2 content is at least twice as high, more preferably at least three times as high, even more preferably at least four times as high, most preferably at least seven times as high and in particular at least ten times as high as the N2O content.
  • Sentence 25 The method according to one of the preceding sentences, wherein the exhaust gas has an N2O content which is greater than the NOX content; preferably wherein the N2O content is at least twice as high, more preferably at least three times as high, even more preferably at least four times as high, most preferably at least seven times as high and in particular at least ten times as high as the NOX content.
  • Sentence 26 The method according to one of the preceding sentences, wherein the exhaust gas has an N2O content which is greater than the NO content; preferably wherein the N2O content is at least twice as high, more preferably at least three times as high, even more preferably at least four times as high, most preferably at least seven times as high and in particular at least ten times as high as the NO content.
  • Sentence 27 The method according to one of the preceding sentences, wherein the exhaust gas has an N2O content which is greater than the NO2 content; preferably wherein the N2O content is at least twice as high, more preferably at least three times as high, even more preferably at least four times as high, most preferably at least seven times as high and in particular at least ten times as high as the NO content. 2 .
  • Sentence 28 The process according to one of the preceding sentences, wherein the exhaust gas has a content of NO X of at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, and in particular at least 50 ppmv.
  • Sentence 29 The process according to one of the preceding sentences, wherein the exhaust gas has a content of NO X of at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, and in particular at least 250 ppmv.
  • Sentence 30 The method according to one of the preceding sentences, wherein the exhaust gas has a content of NO X of at least 500 ppmv, preferably at least 1000 ppmv, more preferably at least 2000 ppmv, even more preferably at least 3000 ppmv, and in particular at least 3500 ppmv.
  • Sentence 31 The process according to one of the preceding sentences, wherein the exhaust gas has a content of N 2 O of at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, and in particular at least 50 ppmv.
  • Sentence 32 The process according to one of the preceding sentences, wherein the exhaust gas has an N2O content of at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, and in particular at least 250 ppmv.
  • Sentence 33 The process according to one of the preceding sentences, wherein the exhaust gas has an N2O content of at least 500 ppmv, preferably at least 1000 ppmv, more preferably at least 2000 ppmv, even more preferably at least 3000 ppmv, and in particular at least 3500 ppmv.
  • Sentence 34 The process according to one of the preceding sentences, wherein the exhaust gas has an H2O content of less than 2.0 vol.%.
  • Sentence 35 The process according to one of the preceding sentences, wherein the exhaust gas has an H2O content of more than 4.0 vol.%; preferably at least 5.0 vol.%, more preferably at least 6.0 vol.%, even more preferably at least 7.0 vol.%, most preferably at least 8.0 vol.%, and in particular at least 9.0 vol.%.
  • Sentence 36 The process according to one of the preceding sentences, wherein the exhaust gas has an H2O content of at least 10 vol.%; preferably at least 12 vol.%, more preferably at least 14 vol.%, even more preferably at least 16 vol.%, most preferably at least 18 vol.%, and in particular at least 20 vol.%.
  • Sentence 37 The process according to one of the preceding sentences, wherein the exhaust gas has an H2O content in the range of 10 ⁇ 8 vol.%; preferably in the range of 10 ⁇ 7 vol.%, more preferably in the range of 10 ⁇ 6 vol.%, even more preferably in the range of 10 ⁇ 5 vol.%, most preferably in the range of 10 ⁇ 4 vol.%, and in particular in the range of 10 ⁇ 3 vol.%.
  • Sentence 38 The process according to one of the preceding sentences, wherein the exhaust gas has a content of H 2 O in the range of 15 ⁇ 8 vol.%; preferably in the range of 15 ⁇ 7 vol.%, more preferably in the range of 15 ⁇ 6 vol.%, even more preferably in the range of 15 ⁇ 5 vol.%, most preferably in the range of 15 ⁇ 4 vol.%, and in particular in the range of 15 ⁇ 3 vol.%.
  • Sentence 39 The process according to one of the preceding sentences, wherein the exhaust gas has a content of H 2 O in the range of 20 ⁇ 8 vol.%; preferably in the range of 20 ⁇ 7 vol.%, more preferably in the range of 20 ⁇ 6 vol.%, more preferably in the range of 20 ⁇ 5 vol.%, most preferably in the range of 20 ⁇ 4 vol.%, and in particular in the range of 20 ⁇ 3 vol.%.
  • Sentence 40 The process according to one of the preceding sentences, wherein the exhaust gas has a content of H 2 O in the range of 25 ⁇ 8 vol.%; preferably in the range of 25 ⁇ 7 vol.%, more preferably in the range of 25 ⁇ 6 vol.%, even more preferably in the range of 25 ⁇ 5 vol.%, most preferably in the range of 25 ⁇ 4 vol.%, and in particular in the range of 25 ⁇ 3 vol.%.
  • Sentence 41 The process according to one of the preceding sentences, wherein the exhaust gas has a content of H 2 O in the range of 30 ⁇ 8 vol.%; preferably in the range of 30 ⁇ 7 vol.%, more preferably in the range of 30 ⁇ 6 vol.%, even more preferably in the range of 30 ⁇ 5 vol.%, most preferably in the range of 30 ⁇ 4 vol.%, and in particular in the range of 30 ⁇ 3 vol.%.
  • Sentence 42 The process according to one of the preceding sentences, wherein the exhaust gas has an N2 content of at most 95 vol.%, preferably at most 90 vol.%, more preferably at most 85 vol.%, even more preferably at most 80 vol.%, most preferably at most 75 vol.%, and in particular at most 70 vol.%.
  • Sentence 43 The method according to one of the preceding sentences, wherein the exhaust gas has an N2 content of at least 40 vol. %, preferably at least 50 vol. %, more preferably at least 60 vol. %, even more preferably at least 70 vol. %, most preferably at least 80 vol. %, and in particular at least 90 vol. %.
  • Sentence 44 The method according to one of the preceding sentences, wherein the exhaust gas comprises further gaseous components; preferably selected from the group consisting of O2, CO, CO2, NH3, CH4 and mixtures thereof.
  • Sentence 45 The method according to one of the preceding sentences, wherein the exhaust gas has a temperature of at least 500°C, more preferably at least 600°C, even more preferably at least 700°C, most preferably at least 800°C, and in particular at least 900°C when leaving the firing system, preferably the furnace, more preferably the combustion device.
  • Sentence 46 The method according to one of the preceding sentences, wherein the exhaust gas when leaving the combustion system, preferably the furnace, more preferably the combustion device has a temperature of at most 1100°C, more preferably at most 1000°C, even more preferably at most 900°C, most preferably at most 800°C, and in particular at most 700°C.
  • Sentence 47 The method according to one of the preceding sentences, wherein the exhaust gas when leaving the combustion system, preferably the furnace, more preferably the combustion device has a pressure of at most 1.5 bar; preferably atmospheric pressure.
  • Sentence 48 The method according to one of the preceding sentences, wherein the exhaust gas when leaving the combustion system, preferably the furnace, more preferably the combustion device has an oxidation level of NO X of at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, and in particular at least 50%.
  • Sentence 49 The method according to one of the preceding sentences, wherein the exhaust gas when leaving the combustion plant, preferably the furnace, more preferably the combustion device, has an oxidation level of NO X of at most 90%, more preferably at most 80%, even more preferably at most 70%, most preferably at most 60%, and in particular at most 50%.
  • Sentence 50 The method according to one of the preceding sentences, wherein the exhaust gas when leaving the combustion plant, preferably the furnace, more preferably the combustion device has a content of O 2 of less than 2.0 vol. %.
  • Sentence 51 The process according to one of the preceding sentences, wherein the exhaust gas when leaving the combustion plant, preferably the furnace, more preferably the combustion device, has a content of O 2 of more than 4.0 vol. %.
  • Sentence 52 The method according to one of the preceding sentences, wherein the exhaust gas has a temperature of at least 300°C, more preferably at least 350°C, even more preferably at least 400°C, most preferably at least 425°C, and in particular at least 450°C upon entering the exhaust gas treatment plant.
  • Sentence 53 The method according to one of the preceding sentences, wherein the exhaust gas has a temperature of at least 500°C, more preferably at least 550°C, even more preferably at least 600°C, most preferably at least 625°C, and in particular at least 650°C upon entering the exhaust gas treatment plant.
  • Sentence 54 The method according to one of the preceding sentences, wherein the exhaust gas has a temperature of at most 825°C, more preferably at most 800°C, even more preferably at most 775°C, most preferably at most 750°C, and in particular at most 725°C when entering the exhaust gas treatment plant.
  • Sentence 55 The method according to one of the preceding sentences, wherein the exhaust gas has a temperature of at most 700°C, more preferably at most 650°C, even more preferably at most 600°C, most preferably at most 550°C, and in particular at most 500°C when entering the exhaust gas treatment plant.
  • Sentence 56 The method according to one of the preceding sentences, wherein the exhaust gas has a temperature when entering the exhaust gas treatment plant which is relatively at least 20°C, preferably at least 40°C, more preferably at least 60°C, even more preferably at least 80°C, most preferably at least 100°C, and in particular at least 120°C below the temperature which the exhaust gas has when leaving the combustion plant, preferably the furnace, more preferably the combustion device.
  • Sentence 57 The method according to one of the preceding sentences, wherein the exhaust gas has a pressure of at most 1.2 bar when entering the exhaust gas treatment plant; preferably atmospheric pressure.
  • Sentence 58 The method according to one of the preceding sentences, wherein the exhaust gas has an oxidation level of NO when entering the exhaust gas treatment plant X of at least 10%, preferably at least 20%, more preferably at least 30%, most preferably at least 40%, and in particular at least 50%.
  • Sentence 59 The method according to one of the preceding sentences, wherein the exhaust gas has an oxidation level of NO when entering the exhaust gas treatment plant X of at most 90%, more preferably at most 80%, even more preferably at most 70%, most preferably at most 60%, and in particular at most 50%.
  • Sentence 60 The process according to one of the preceding sentences, wherein the exhaust gas has a content of O 2 of less than 2.0 vol.%.
  • Sentence 61 The process according to any one of the preceding sentences, wherein the exhaust gas has an O2 content of more than 4.0 vol.% on entry into the exhaust gas treatment plant.
  • Sentence 62 The process according to any one of the preceding sentences, wherein step (d) comprises reducing the N2O content in the exhaust gas by (d1) decomposition of N2O on an N2O decomposition catalyst; preferably wherein the N2O decomposition catalyst comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the MFI, BEA, FER, MOR, FAU and/or MEL type.
  • the N2O decomposition catalyst comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the MFI, BEA, FER, MOR, FAU and/or MEL type.
  • Sentence 63 The process according to any one of the preceding sentences, wherein step (d) comprises reducing the content of N2O in the exhaust gas by (d2) chemically reducing N2O with reducing agent on a N2O reduction catalyst; preferably wherein the N2O reduction catalyst comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the type MFI, BEA, FER, MOR, FAU and/or MEL.
  • the N2O reduction catalyst comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the type MFI, BEA, FER, MOR, FAU and/or MEL.
  • Sentence 64 The process according to any one of the preceding sentences, wherein the reducing agent in step (d2) is selected from NH3, hydrocarbons, CO, H2 and mixtures thereof; preferably NH3.
  • Sentence 65 The process according to one of the preceding sentences, wherein the reducing agent in step (d2) is NH3, which is used in an amount of 0.5 to 2.0 molar parts, preferably 0.8 to 1.8 molar parts, based on a molar proportion of N2O to be chemically reduced.
  • Sentence 66 The process according to one of the preceding sentences, wherein the reducing agent in step (d2) is a hydrocarbon or a mixture of several hydrocarbons, which are preferably used in an amount of 0.2 to 1.0 molar parts, more preferably 0.2 to 0.7 molar parts, based on a molar proportion of N to be reduced. 2 O.
  • the reducing agent in step (d2) is a hydrocarbon or a mixture of several hydrocarbons, which are preferably used in an amount of 0.2 to 1.0 molar parts, more preferably 0.2 to 0.7 molar parts, based on a molar proportion of N to be reduced. 2 O.
  • Sentence 67 The procedure according to one of the preceding sentences, where the NO X -Reduction catalyst comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the MFI, BEA, FER, MOR, FAU and/or MEL type.
  • Set 68 The process of any preceding set, wherein the reducing agent in step (e) is selected from NH 3 , hydrocarbons, CO, H 2 and mixtures thereof; preferably NH 3 .
  • Clause 69 The process according to any preceding clause, wherein the reducing agent in step (e) is NH 3 which is used in an amount of 0.9 to 2.5 molar parts, preferably 1.0 to 1.4 molar parts, more preferably 1.0 to 1.2 molar parts, based on a molar proportion of NO to be chemically reduced X .
  • Sentence 70 The process according to any one of the preceding sentences, wherein the reducing agent in step (d 2 ) is the same as the reducing agent in step (e); preferably NH 3 .
  • Sentence 71 The method according to one of the preceding sentences, wherein the exhaust gas treatment system comprises a first reaction zone and a second reaction zone arranged behind it, through which the exhaust gas flows one after the other; wherein reducing agent is added to the exhaust gas upstream of the first reaction zone; wherein firstly in the first reaction zone the content of NOX in the exhaust gas is reduced by chemical reduction of NOX with reducing agent on a NOX reduction catalyst; (step (e)); wherein optionally additionally the content of N2O in the exhaust gas is reduced by decomposition of N2O on a N2O decomposition catalyst (step (d1)) and/or by chemical reduction of N2O with reducing agent on a N2O reduction catalyst (step (d2)); wherein optionally further reducing agent is added to the exhaust gas upstream of the second reaction zone; and wherein subsequently in the second reaction zone the content of N2O in the exhaust gas is reduced by decomposition of N2O on an N2O decomposition catalyst (step (d1)) and/or by
  • Sentence 72 The method according to sentence 71, wherein the NOX reduction catalyst in the first reaction zone comprises a conventional SCR catalyst, preferably based on V2O5-WO3-/TiO2.
  • Sentence 73 The method according to sentence 71 or 72, wherein the temperature of the exhaust gas on entry into the first reaction zone is at most 400°C, preferably at most 350°C.
  • Sentence 74 The process according to one of sentences 71 to 73, wherein the N2O decomposition catalyst in the second reaction zone comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the MFI, BEA, FER, MOR, FAU and/or MEL type.
  • Sentence 75 The process according to one of sentences 71 to 74, wherein the temperature of the exhaust gas upon entry into the second reaction zone is in the range of 300 to 550°C, preferably 350 to 500°C.
  • Sentence 76 The process according to one of sentences 71 to 75, wherein the NO X -reduction catalyst in the first reaction zone comprises a zeolitic material; preferably a transition metal (a- including lanthanide), in particular a zeolite loaded with iron, cobalt or copper; more preferably a zeolite loaded with iron; even more preferably an iron-loaded zeolite of the MFI, BEA, FER, MOR, FAU and/or MEL type.
  • Sentence 77 The process according to one of sentences 71 to 76, wherein the temperature of the exhaust gas upon entering the first reaction zone is at least 300°C, more preferably at least 350°C, even more preferably at least 400°C.
  • Sentence 78 The process according to one of sentences 71 to 77, wherein the temperature of the exhaust gas upon entering the first reaction zone is at most 600°C, more preferably at most 550°C.
  • Sentence 79 The process according to any one of sentences 71 to 78, wherein the N2O decomposition catalyst in the second reaction zone comprises a NOX-sensitive N2O decomposition catalyst.
  • Sentence 80 The process according to any one of sentences 71 to 79, wherein the temperature of the exhaust gas upon entering the second reaction zone is at least 300°C, more preferably at least 350°C, even more preferably at least 400°C.
  • Sentence 81 The process according to any one of sentences 71 to 80, wherein the temperature of the exhaust gas upon entering the second reaction zone is at most 600°C, more preferably at most 550°C.
  • Sentence 82 The method according to one of sentences 71 to 81, wherein the exhaust gas after leaving the first reaction zone and before entering the second reaction zone has a NOX content in the range of 0 to 200 ppmv, preferably 1 to 200 ppmv, and an N2O content in the range of 200 to 2000 ppmv.
  • Sentence 83 The method according to one of sentences 71 to 82, wherein the exhaust gas after leaving the first reaction zone and before entering the second reaction zone has a NOX content of at most 20 ppmv, more preferably at most 10 ppmv, even more preferably at most 5 ppmv, and an N2O content in the range of 200 to 2000 ppmv.
  • Sentence 84 The method according to one of the preceding sentences, wherein the exhaust gas treatment plant comprises a first reaction zone and a second reaction zone arranged behind it, through which the exhaust gas flows one after the other; wherein reducing agent is added to the exhaust gas between the first reaction zone and the second reaction zone; wherein firstly in the first reaction zone the content of N2O in the exhaust gas is reduced by decomposition of N2O on an N2O decomposition catalyst (step (d1)); and wherein subsequently in the second reaction zone the content of NOX in the exhaust gas is reduced by chemical reduction of NOX with reducing agent on an NOX reduction catalyst (step (e)); wherein optionally additionally the content of N 2 O in the exhaust gas by further decomposition of N 2 O on an N 2 O decomposition catalyst (step (d 1 )) and/or by chemical reduction of N 2 O with reducing agent at a N 2 O-reduction catalyst (step (d 2 )) is further reduced.
  • Sentence 85 The process according to sentence 84, wherein no reducing agent is added to the exhaust gas before the first reaction zone.
  • Sentence 86 The procedure according to sentence 84 or 85, where the N 2 O decomposition catalyst in the first reaction zone comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably an iron-loaded zeolite; even more preferably an iron-loaded zeolite of the MFI, BEA, FER, MOR, FAU and/or MEL type.
  • transition metal including lanthanide
  • Sentence 87 The process according to any one of sentences 84 to 86, wherein the N 2 O decomposition catalyst in the first reaction zone a NO X -sensitive N 2 O decomposition catalyst.
  • Clause 88 The process according to any one of clauses 84 to 87, wherein the NO X -Reduction catalyst in the second reaction zone comprises a zeolitic material; preferably a zeolite loaded with transition metal (including lanthanide), in particular with iron, cobalt or copper; more preferably a zeolite loaded with iron; even more preferably an iron-loaded zeolite of the MFI, BEA, FER, MOR, FAU and/or MEL type.
  • Sentence 89 The process according to one of sentences 84 to 88, wherein in the first reaction zone and in the second reaction zone the space velocities are adjusted such that in the first reaction zone the content of N2O in the exhaust gas is reduced by at most 95%, preferably at most 90%, based on the content of N2O in the exhaust gas on entry into the first reaction zone.
  • Sentence 90 The method according to one of sentences 84 to 89, wherein in the second reaction zone there is a further reduction in the N2O content in the exhaust gas by at least 30%, preferably at least 40%, more preferably at least 50%, based on the N2O content in the exhaust gas on entry into the second reaction zone.
  • Sentence 91 The method according to one of sentences 84 to 90, wherein in the second reaction zone there is a further reduction in the N2O content in the exhaust gas by chemical reduction of N2O with reducing agent on an N2O reduction catalyst (step (d2)).
  • Sentence 92 The method according to one of sentences 71 to 91, wherein the first reaction zone and the second reaction zone are spatially separated.
  • Sentence 93 The method according to one of sentences 71 to 92, wherein the first reaction zone and the second reaction zone are spatially connected to one another.
  • Sentence 94 The process according to one of sentences 71 to 93, wherein the first reaction zone and the second reaction zone are arranged in a common container.
  • Sentence 95 The process according to one of sentences 71 to 94, wherein the temperature of the exhaust gas in the first reaction zone and in the second reaction zone is at most 500°C, preferably in the range from 350 to 450°C.
  • Sentence 96 The process according to one of sentences 71 to 95, wherein the space velocity in the first reaction zone is greater than in the second reaction zone; preferably by at least a factor of 1.2, more preferably at least a factor of 1.4, even more preferably at least a factor of 1.6, most preferably at least a factor of 1.8, and in particular at least a factor of 2.0.
  • Sentence 97 The process according to any one of sentences 71 to 96, wherein the space velocity in the first reaction zone is lower than in the second reaction zone; preferably by at least a factor of 1.5, more preferably at least a factor of 2.0, even more preferably at least a factor of 3.0, most preferably at least a factor of 5.0, and especially at least a factor of 10.0.
  • Sentence 98 The process according to any one of sentences 71 to 97, wherein the temperature in the first reaction zone is at least 450°C, more preferably at least 500°C, even more preferably at least 550°C, most preferably at least 600°C, and especially at least 650°C.
  • Sentence 99 The process according to any one of sentences 71 to 98, wherein the temperature in the second reaction zone is at most 600°C, more preferably at most 550°C, even more preferably at most 500°C, most preferably at most 450°C and in particular at most 400°C.
  • Sentence 100 The process according to any one of sentences 71 to 99, wherein the temperature in the first reaction zone is relatively higher than the temperature in the second reaction zone by at least 20°C, more preferably by at least 40°C, even more preferably by at least 60°C, most preferably by at least 80°C and in particular by at least 100°C.
  • Sentence 101 The process according to any one of sentences 71 to 100, wherein the temperature in the first reaction zone is relatively higher than the temperature in the second reaction zone by at least 120°C, more preferably by at least 140°C, even more preferably by at least 160°C, most preferably by at least 180°C and in particular by at least 200°C.
  • Sentence 102 The process according to any one of the preceding sentences, wherein the exhaust gas leaves the exhaust gas treatment plant and has a residual NOX content of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, and in particular at most 2.5 ppmv.
  • Sentence 103 The method according to one of the preceding sentences, wherein the exhaust gas leaves the exhaust gas treatment system and has a residual N2O content of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, and in particular at most 2.5 ppmv.
  • Sentence 104 The method according to one of the preceding sentences, wherein the N2O decomposition catalyst is arranged in a radial basket through which the flow is axial.
  • Sentence 105 The method according to one of the preceding sentences, wherein the N2O decomposition catalyst is particulate and comprises at least 50 particles.
  • Sentence 106 The method according to one of the preceding sentences, wherein the N 2 O reduction catalyst is arranged in a radial basket through which the flow is axial.
  • Sentence 107 The method according to one of the preceding sentences, wherein the N 2 O reduction catalyst is particulate and comprises at least 50 particles.
  • Sentence 108 The process according to one of the preceding sentences, wherein the NO X -Reduction catalyst is arranged in a radial basket through which the flow is axial.
  • Sentence 109 The procedure according to one of the preceding sentences, whereby the NO X -reduction catalyst is particulate and comprises at least 50 particles.
  • Sentence 110 The method according to one of the preceding sentences, wherein in the combustion plant at least one parameter is measured as a first measured variable which is characteristic of the current operating state of the combustion plant.
  • Sentence 111 The method according to sentence 110, wherein the first measured variable is selected from the group consisting of combustion temperature, NH 3 -Consumption, if applicable rotation speed, and noise level of the combustion system.
  • Sentence 112 The method according to one of the preceding sentences, wherein before entering the exhaust gas treatment system, at least one parameter is measured as a second measurement variable, which is characteristic of the current state of the exhaust gas before entering the exhaust gas treatment system.
  • Sentence 113 The method according to sentence 112, wherein the second measurement variable is selected from the group consisting of NOX content in the exhaust gas; degree of oxidation of the NOX in the exhaust gas; N2O content in the exhaust gas; content of other components in the exhaust gas, such as H2O, O2, and N2; temperature of the exhaust gas; pressure of the exhaust gas; and volume flow of the exhaust gas.
  • Sentence 114 The method according to one of the preceding sentences, wherein at the outlet of the exhaust gas treatment system, at least one parameter is measured as a third measurement variable, which is characteristic of the current state of the exhaust gas at the outlet of the exhaust gas treatment system.
  • Sentence 115 The method according to sentence 114, wherein the third measured variable is selected from the group consisting of NOX content in the exhaust gas; degree of oxidation of the NOX in the exhaust gas; N2O content in the exhaust gas; content of other components in the exhaust gas, such as H2O, O2, and N2; temperature of the exhaust gas; pressure of the exhaust gas; and volume flow of the exhaust gas.
  • Sentence 116 The method according to one of the preceding sentences, wherein the exhaust gas treatment system comprises a first reaction zone and a second reaction zone, through which the exhaust gas flows one after the other, wherein reducing agent is fed between the first reaction zone and the second reaction zone, and wherein after leaving the first reaction zone and before entering the second reaction zone, at least one parameter is measured as a fourth measured variable, which is characteristic of the current state of the exhaust gas after leaving the first reaction zone and before entering the second reaction zone.
  • Sentence 117 The method according to sentence 116, wherein the fourth measured variable is selected from the group consisting of NO content X in the exhaust gas; degree of oxidation of NO X in exhaust gas; N content 2 O in the exhaust gas; content of other components in the exhaust gas, such as H 2 Oh, Oh 2 , and N 2 ; temperature of the exhaust gas; pressure of the exhaust gas; and volume flow of the exhaust gas.
  • Sentence 118 The method according to one of the sentences 110 to 117, wherein the control of the method is carried out based on the first measured variable and/or based on the second measured variable and/or based on the third measured variable and/or based on the fourth measured variable by specifically changing a control variable.
  • Sentence 119 The method according to sentence 118, wherein the control variable is the amount of reducing agent added.
  • Sentence 120 The method according to one of the preceding sentences, wherein a single heat exchanger is arranged downstream of the exhaust gas treatment system in the direction of flow of the exhaust gas, in which the cooling of the exhaust gas takes place.
  • Sentence 121 The method according to one of the preceding sentences, wherein at least two heat exchangers are arranged downstream of the exhaust gas treatment system in the direction of flow of the exhaust gas, in which the cooling of the exhaust gas takes place one after the other.
  • Sentence 122 The method according to one of the preceding sentences, wherein at least three heat exchangers are arranged downstream of the exhaust gas treatment system in the direction of flow of the exhaust gas, in which the cooling of the exhaust gas takes place one after the other.
  • Sentence 123 The method according to one of the preceding sentences, wherein at least four heat exchangers are arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, in which the exhaust gas is cooled one after the other.
  • Sentence 124 The method according to one of the preceding sentences, wherein at least five heat exchangers are arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, in which the exhaust gas is cooled one after the other.
  • Sentence 125 The method according to one of the preceding sentences, wherein in step (f) the exhaust gas is cooled in the at least one heat exchanger by releasing heat from the exhaust gas to a heat transfer medium; wherein the heat transfer medium is preferably selected from the group consisting of water, water vapor, combustion air, NH3 and combinations thereof.
  • Sentence 126 The method according to one of the preceding sentences, wherein in step (f) the cooling of the exhaust gas takes place in a first exhaust gas/H2O heat exchanger, which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas.
  • Sentence 127 The method according to one of the preceding sentences, wherein in step (f) the cooling of the exhaust gas takes place in a first exhaust gas/combustion air heat exchanger, which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas.
  • Sentence 128 The method according to one of the preceding sentences, wherein in step (f) the cooling of the exhaust gas takes place - in a first exhaust gas/H 2 O heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, and - in a first exhaust gas/combustion air heat exchanger, which is also arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system; preferably downstream of the first exhaust gas/H 2 O heat exchanger sentence 129: The method according to one of the preceding sentences, wherein in step (f) the cooling of the exhaust gas takes place - in a first exhaust gas/combustion air heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, and - in a second Exhaust gas/combustion air heat exchanger, which is arranged downstream of the first exhaust gas/combustion air heat exchanger in the flow direction of the exhaust gas.
  • Sentence 130 The method according to one of the preceding sentences, wherein in step (f) the cooling of the exhaust gas takes place - in a first exhaust gas/combustion air heat exchanger, which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, - in a first exhaust gas/H 2 O heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the first exhaust gas/combustion air heat exchanger, and - in a second exhaust gas/combustion air heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the first exhaust gas/H2O heat exchanger.
  • a first exhaust gas/combustion air heat exchanger which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas
  • a first exhaust gas/H 2 O heat exchanger which is arranged in the flow direction of the exhaust gas downstream of the first exhaust gas/combustion air heat exchanger
  • a second exhaust gas/combustion air heat exchanger which is arranged in the flow direction of the exhaust
  • Sentence 131 The method according to one of the preceding sentences, wherein in step (f) the cooling of the exhaust gas takes place in at least one exhaust gas/combustion gas heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, preferably downstream of the first exhaust gas/combustion air heat exchanger, the first exhaust gas/H2O heat exchanger, and/or the second exhaust gas/combustion air heat exchanger.
  • Sentence 132 The method according to one of the preceding sentences, wherein in step (f) the cooling of the exhaust gas takes place in at least one exhaust gas/combustion gas heat exchanger which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, preferably downstream of the first exhaust gas/combustion air heat exchanger, the first exhaust gas/H2O heat exchanger, and/or the second exhaust gas/combustion air heat exchanger.
  • Sentence 133 The method according to one of the preceding sentences, wherein in step (f) the cooling of the exhaust gas takes place in at least one second exhaust gas/H2O heat exchanger which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, preferably downstream of the first exhaust gas/combustion air heat exchanger, the first exhaust gas/H2O heat exchanger, and/or the second exhaust gas/combustion air heat exchanger.
  • Sentence 134 The method according to one of the preceding sentences, wherein in step (f) of the method the cooling of the exhaust gas takes place - in a first exhaust gas/combustion air heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, - in a first exhaust gas/H 2 O heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the first exhaust gas/combustion air heat exchanger, - in a second exhaust gas/combustion air heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the first exhaust gas/H 2 O heat exchanger, and - in an exhaust gas/combustion gas heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the second exhaust gas/combustion air heat exchanger.
  • Sentence 135 The method according to one of the preceding sentences, wherein in step (f) the cooling of the exhaust gas takes place - in a first exhaust gas/combustion air heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the exhaust gas treatment system, - in a first gas/H 2 O heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the first exhaust gas/combustion air heat exchanger, - in a second exhaust gas/combustion air heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the first exhaust gas/H 2 O heat exchanger, and - in a second exhaust gas/H 2 O heat exchanger, which is arranged in the flow direction of the exhaust gas downstream of the second exhaust gas/combustion air heat exchanger.
  • Sentence 136 The method according to one of the preceding sentences, wherein in step (f) the cooling of the exhaust gas takes place - in a first exhaust gas/combustion air heat exchanger, which is arranged downstream of the exhaust gas treatment system in the flow direction of the exhaust gas, - in a first exhaust gas/H2O heat exchanger, which is arranged downstream of the first exhaust gas/combustion air heat exchanger in the flow direction of the exhaust gas, - in a second exhaust gas/combustion air heat exchanger, which is arranged downstream of the first exhaust gas/H2O heat exchanger in the flow direction of the exhaust gas, - in an exhaust gas/combustion gas heat exchanger, which is arranged downstream of the second exhaust gas/combustion air heat exchanger in the flow direction of the exhaust gas, and - in a second exhaust gas/H2O heat exchanger, which is arranged downstream of the Exhaust gas/combustion gas heat exchanger is arranged.
  • Sentence 137 A device comprising (i) a combustion system operated with NH3; preferably a furnace (preferably comprising combustion device and NH3 decomposition device) for catalytic decomposition of NH3 into N2 and H2; and (ii) an exhaust gas treatment system; wherein the device is configured to carry out the method according to one of the preceding sentences.
  • a combustion system operated with NH3 preferably a furnace (preferably comprising combustion device and NH3 decomposition device) for catalytic decomposition of NH3 into N2 and H2; and (ii) an exhaust gas treatment system; wherein the device is configured to carry out the method according to one of the preceding sentences.
  • NH3 is preferably preheated with steam and steam condensate, optionally exclusively or additionally.
  • Figure 1 shows a schematic of a preferred embodiment of the invention.
  • NH3 is fed into an NH3 decomposition device (1), which is designed analogously to a primary reformer, and therein on an NH 3 -Decomposition catalyst catalytically decomposes into a product gas comprising H 2 +N 2 +NH 3
  • a combustion gas comprising NH 3 +N 2 +H 2 in a combustion device (2) mixed with combustion air comprising N2+O2 and burned.
  • the combustion heat generated thereby fires the NH3 decomposition device (1).
  • the exhaust gas generated during combustion comprising N2+H2O+NOX+N2O enters an exhaust gas duct (3) and is fed to an exhaust gas treatment system (4), in which the content of NOX and N2O is practically completely removed.
  • FIG. 1 shows a schematic representation of a preferred embodiment of the invention (process variant #1).
  • the exhaust gas channel contains a first exhaust gas/NH 3 -Heat exchanger (Q1) in which NH 3 absorbs heat from the exhaust gas and then the NH 3 -decomposition device.
  • FIG. 1 shows a schematic of a preferred embodiment of the invention (process variant #2).
  • the exhaust gas channel contains a first exhaust gas/NH3 heat exchanger (Q1) in the flow direction of the exhaust gas, in which NH3 absorbs heat from the exhaust gas and is then fed to a first pre-reactor (NH3 decomposition device) for the partial catalytic decomposition of NH3.
  • the intermediate product gas is preferably cooled, for example from 650°C at the inlet of the first pre-reactor to 360°C at the outlet of the first pre-reactor.
  • the exhaust gas treatment system is arranged downstream of the second exhaust gas/NH3 heat exchanger (Q2).
  • a first exhaust gas/H2O heat exchanger (Q5) in which water absorbs heat from the exhaust gas.
  • FIG. 4 shows schematically a preferred embodiment of the invention (process variant #3).
  • the exhaust gas channel contains a first exhaust gas/NH 3 -Heat exchanger (Q1) in which NH 3 absorbs heat from the exhaust gas and then feeds it to a first pre-reactor (NH 3 -decomposition device) for the partial catalytic decomposition of NH 3 is fed.
  • the first intermediate product gas preferably cools down, for example from 650°C at the inlet of the first pre-reactor to 480°C at the outlet of the first pre-reactor.
  • a second exhaust gas/NH3 heat exchanger (Q2) is arranged downstream of the first exhaust gas/NH3 heat exchanger (Q1), in which intermediate product gas absorbs heat from the exhaust gas and then passes it to a second pre-reactor (NH 3 -decomposition device) for the partial catalytic decomposition of NH 3 is fed.
  • the second intermediate product gas is preferably cooled, for example from 630°C at the inlet of the second pre-reactor to 510°C at the outlet of the second pre-reactor.
  • a third Exhaust gas/NH 3 -Heat exchanger (Q3) is arranged in which intermediate product gas absorbs heat from the exhaust gas and then the NH 3 -Decomposition device for the catalytic decomposition of NH 3
  • downstream of the third exhaust gas/NH 3 -heat exchanger (Q3) is arranged in the exhaust gas treatment system.
  • a first exhaust gas/H2O heat exchanger (Q5) is arranged downstream of the exhaust gas treatment system, in which water absorbs heat from the exhaust gas.
  • FIG. 5 shows a schematic of a preferred embodiment of the invention (process variant #4).
  • the exhaust gas channel contains a first exhaust gas/NH3 heat exchanger (Q1) in the flow direction of the exhaust gas, in which NH3 absorbs heat from the exhaust gas and is then fed to a first pre-reactor (NH3 decomposition device) for the partial catalytic decomposition of NH3.
  • the intermediate product gas is preferably cooled, for example from 650°C at the inlet of the first pre-reactor to 360°C at the outlet of the first pre-reactor.
  • a second exhaust gas/NH3 heat exchanger in which intermediate product gas absorbs heat from the exhaust gas and is then fed to the NH3 decomposition device for the catalytic decomposition of NH3.
  • downstream of the second exhaust gas/NH3 heat exchanger downstream of the second exhaust gas/NH3 heat exchanger (Q2) there is the exhaust gas treatment system.
  • first exhaust gas/combustion air heat exchanger in which combustion air absorbs heat from the exhaust gas.
  • first exhaust gas/H2O heat exchanger downstream of the first exhaust gas/combustion air heat exchanger (Q4) there is a first exhaust gas/H2O heat exchanger (Q5) in which water absorbs heat from the exhaust gas.
  • a second exhaust gas/combustion air heat exchanger is arranged downstream of the first exhaust gas/H2O heat exchanger (Q5), in which combustion air absorbs heat from the exhaust gas, is then fed to the first exhaust gas/combustion air heat exchanger (Q4) and then to the combustion device.
  • FIG. 6 schematically shows three preferred embodiments of the invention, which are similar to one another (process variants #5, #6 and #7).
  • the exhaust gas duct in the flow direction of the exhaust gas contains a first exhaust gas/NH 3 -Heat exchanger (Q1) in which NH 3 absorbs heat from the exhaust gas and then feeds it to a first pre-reactor (NH 3 -decomposition device) for the partial catalytic decomposition of NH 3
  • the intermediate product gas cools preferentially, for example from 650°C at the inlet of the first pre-reactor to 360°C at the Outlet of the first pre-reactor.
  • a second exhaust gas/NH 3 -Heat exchanger (Q2) is arranged in which the intermediate product gas absorbs heat from the exhaust gas and then the NH 3 -Decomposition device for the catalytic decomposition of NH 3 is supplied.
  • the exhaust gas treatment system is arranged downstream of the second exhaust gas/NH3 heat exchanger (Q2).
  • a first exhaust gas/combustion air heat exchanger (Q4) is arranged downstream of the exhaust gas treatment system, in which combustion air absorbs heat from the exhaust gas.
  • a first exhaust gas/H 2 O heat exchanger (Q5) is arranged in which water absorbs heat from the exhaust gas.
  • a second exhaust gas/combustion air heat exchanger (Q6) is arranged, in which combustion air absorbs heat from the exhaust gas, is then fed to the first exhaust gas/combustion air heat exchanger (Q4) and then to the combustion device.
  • the heating of the combustion air thus takes place in two stages, first in the second exhaust gas/combustion air heat exchanger (Q6) and then in the first exhaust gas/combustion air heat exchanger (Q4).
  • an exhaust gas/combustion gas heat exchanger (Q7) is arranged, in which combustion gas, namely the off-gas of the pressure swing adsorption device, absorbs heat from the exhaust gas and is then fed to the combustion device.
  • a second exhaust gas/H2O heat exchanger (Q8) is arranged, in which water absorbs heat from the exhaust gas.
  • process variant #5 the residual heat remaining in the exhaust gas is removed with water in the second exhaust gas/H2O heat exchanger (Q8) and given off to NH3, which is thus preheated from the liquid state (storage temperature -33.5°C) to, for example, -8°C.
  • heat is removed with water in the first exhaust gas/H2O heat exchanger (Q5) and given off to NH3, which is thus preheated from the liquid state to, for example, 30°C.
  • the residual heat remaining in the exhaust gas is removed with water in the second exhaust gas/H 2 O heat exchanger (Q8) with water and also to NH 3 which is then heated to, for example, 45°C.
  • process variant #7 heat is removed in the first exhaust gas/H2O heat exchanger (Q5) with water and transferred to NH 3 which is preheated from the liquid state to, for example, 30°C.
  • the residual heat remaining in the exhaust gas is released in the second exhaust gas/H 2 O heat exchanger (Q8) with water and also to NH 3 which is then heated to 39°C, for example.
  • the amount of preheated boiler feed water is increased compared to the amount required to produce steam.
  • the excess boiler feed water is stored below of a NH 3 evaporator into a stream of steam condensate and serves as an additional heat carrier.
  • the exhaust gas contains a comparatively high content of nitrogen oxides of 5000 ppmv NO, 10 ppmv NO2 and 50 ppmv N2O: [0506]
  • Process variant #1 Process variant 1A 1 2 3 4 5 6 7 8 9 1 0 CO2 Mol.- 0.00 0.00 0.00 0.00 0.00 0.00 % Ar Mol.- 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 % H2 Mol.- 0.00 0.00 0.00 0.00 74.29 0.00 28.81 % N 2 Mol.- 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 74.29 0.00 28.81 % N 2 Mol.- 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 74.29 0.00 28.81 % N 2 Mol.- 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 68.55 % NH3 Mol.- 99.81 99.81 99.81 0.86 99.

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  • Chemical & Material Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Analytical Chemistry (AREA)
  • Biomedical Technology (AREA)
  • Organic Chemistry (AREA)
  • Combustion & Propulsion (AREA)
  • Inorganic Chemistry (AREA)
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  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

L'invention concerne la réduction de la teneur en NOX et N2O dans le dégagement gazeux (gaz de combustion) d'une installation de cuisson fonctionnant au NH3 qui est intégrée dans une installation pour la décomposition catalytique de NH3 en N2 et H2. A cet effet, l'installation de cuisson comprend de préférence un moyen de combustion dans lequel NH3 est brûlé pour produire de la chaleur de combustion et un moyen de décomposition NH 3 qui est en échange de chaleur avec le moyen de combustion et dans lequel NH 3 est décomposé catalytiquement pour obtenir N2 et H2. La chaleur requise pour la décomposition catalytique de NH3 dans le moyen de décomposition NH3 est fournie par la combustion de NH3 dans le moyen de combustion. Le moyen de combustion comprend de préférence au moins un brûleur et un espace de combustion. L'installation de cuisson est de préférence conçue de manière analogue à un reformeur primaire.
EP23838095.0A 2022-12-23 2023-12-22 <sup2/>? <sub2/>?2?réduction de la teneur en nox et no dans le dégagement gazeux d'installations de cuisson fonctionnant au nh <ns3:sub>3</ns3:sub> Pending EP4637972A1 (fr)

Applications Claiming Priority (4)

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EP22216421 2022-12-23
EP23165192 2023-03-29
DE102023118563 2023-07-13
PCT/EP2023/087681 WO2024133916A1 (fr) 2022-12-23 2023-12-22 Réduction de la teneur en nox et n2o dans le dégagement gazeux d'installations de cuisson fonctionnant au nh3

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EP (1) EP4637972A1 (fr)
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