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WO2000065150A1 - Procede de gazeification de liqueur residuaire a haute temperature et haute pression - Google Patents

Procede de gazeification de liqueur residuaire a haute temperature et haute pression Download PDF

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Publication number
WO2000065150A1
WO2000065150A1 PCT/US2000/010995 US0010995W WO0065150A1 WO 2000065150 A1 WO2000065150 A1 WO 2000065150A1 US 0010995 W US0010995 W US 0010995W WO 0065150 A1 WO0065150 A1 WO 0065150A1
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WO
WIPO (PCT)
Prior art keywords
liquor
fuel gas
gas
quenched
sweet
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.)
Ceased
Application number
PCT/US2000/010995
Other languages
English (en)
Other versions
WO2000065150A9 (fr
Inventor
Jerry D. Blue
William Downs
Timothy A. Fuller
Christopher L. Verrill
Paul S. Weitzel
Phung H. M. Chan
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.)
Jacobs Canada Inc
Babcock and Wilcox Co
McDermott Technology Inc
Original Assignee
McDermott Engineers and Constructors Canada Ltd
Babcock and Wilcox Co
McDermott Technology Inc
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 McDermott Engineers and Constructors Canada Ltd, Babcock and Wilcox Co, McDermott Technology Inc filed Critical McDermott Engineers and Constructors Canada Ltd
Priority to AU46596/00A priority Critical patent/AU4659600A/en
Priority to CA002370968A priority patent/CA2370968C/fr
Publication of WO2000065150A1 publication Critical patent/WO2000065150A1/fr
Anticipated expiration legal-status Critical
Publication of WO2000065150A9 publication Critical patent/WO2000065150A9/fr
Ceased legal-status Critical Current

Links

Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/12—Combustion of pulp liquors
    • D21C11/125—Decomposition of the pulp liquors in reducing atmosphere or in the absence of oxidants, i.e. gasification or pyrolysis
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/06—Treatment of pulp gases; Recovery of the heat content of the gases; Treatment of gases arising from various sources in pulp and paper mills; Regeneration of gaseous SO2, e.g. arising from liquors containing sulfur compounds
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J15/00—Arrangements of devices for treating smoke or fumes
    • F23J15/06—Arrangements of devices for treating smoke or fumes of coolers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2209/00—Specific waste
    • F23G2209/10—Liquid waste
    • F23G2209/101—Waste liquor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J2215/00—Preventing emissions
    • F23J2215/20—Sulfur; Compounds thereof
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J2219/00—Treatment devices
    • F23J2219/30—Sorption devices using carbon, e.g. coke
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/30—Technologies for a more efficient combustion or heat usage
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/40—Production or processing of lime, e.g. limestone regeneration of lime in pulp and sugar mills

Definitions

  • the present invention relates in general to pulp and paper spent chemical recovery processes, and in particular to a new and useful spent liquor gasification process, such as a black liquor gasification process, which provides a more efficient utilization of the spent chemical's fuel value in the production of electric power.
  • FIG. 1 A schematic representation of a conventional kraft recovery process is depicted in Fig. 1.
  • This process consists of several unit operations. The key ones are the combustion of black liquor in a process recovery boiler 10, the conversion of green liquor to white liquor in a slaker/causticizer 12, the production of steam 14 for both process use and electric power production, and the calcination of calcium carbonate to lime (calcium oxide) in a lime kiln 16. Gases from the recovery boiler 10 are passed to a dust collection apparatus
  • Salt cake is returned at 22 to the inlet of recovery boiler 10 where it is mixed with incoming black liquor and combusted with air.
  • Smelt at 24 from boiler 10 is passed to a dissolving tank 26 where it is contacted with weak wash 28.
  • Dissolving tank 26 discharges green liquor 30 for input into the slaker/causticizer 12.
  • White liquor 32 from the slaker/causticizer 12 is supplied to a digester (not shown) while reburned lime at 34 from kiln 16 is provided into the slaker/causticizer 12 where it reacts with sodium carbonate to produce the white liquor and solid calcium carbonate 36.
  • the white liquor and solid calcium carbonate 36 are separated on a filter, 38, into a filter cake called lime mud 40 and the filtrate, i.e. the white liquor.
  • the lime mud is washed with water, and the filtrate from the washing step is called weak wash 28.
  • the lime mud 40 is provided to the kiln 16 which discharges flue gas 42 to a kiln stack (not shown).
  • Fig. 2 illustrates one of the principal advantages of black liquor gasification over the conventional kraft recovery process, i.e., a substantial improvement in cycle efficiency through the use of combined cycle technology in the form of a gas turbine/steam turbine couple 50.
  • the same reference numerals will be used to designate the same, or functionally similar parts.
  • the black liquor gasification process can also generate a significant quantity of sub-micron sized alkali fume and soot.
  • Alkali fume is extremely damaging to gas turbine blades. For this reason, it is vitally important that alkali fume and soot be controlled to a significant extent, perhaps to a removal efficiency as high as 99.9997% (five nines control).
  • the conventional BLG process purports to do adequate control of fine particulate in a single venruri scrubber 60. However, the energy required to achieve adequate fume control in the single venturi scrubber 60 again places a significant energy penalty on the BLG process.
  • An object of the present invention is to provide a method and apparatus for producing clean, sweet, fuel gas for use in a combustion process by processing a waste stream from digestion of lignocellulosic material.
  • the invention includes partially oxidizing the waste stream to form hot gases and molten salts, and cooling the hot gases and molten salts using a quench liquor to form quenched gas and carbonate liquor. Particles are removed from the quenched gas to form a raw fuel gas by subjecting the quenched gas to a multi-step fume reduction process which includes heat extraction from the quenched gas to reduce particulate load and water content of the quenched gas to form a low fume fuel gas.
  • H 2 S is removed from the low fume fuel gas using an H 2 S removal process which is more selective for H 2 S than it is for CO 2 , the removing step forming clean, sweet, fuel gas and acid gases. Finally, the clean, sweet, fuel gas is conveyed to a combustion process.
  • Fig. 1 is a flow chart showing a prior art kraft recovery apparatus and method
  • Fig. 2 is a flow chart showing a prior art black liquor gasification apparatus and method
  • Fig. 3 is a flow chart showing the apparatus and method of the present invention
  • Fig. 4 is a schematic diagram of a fume and soot collection system of the present invention.
  • the apparatus includes several elements that are common to the generic BLG process depicted in Figure 2.
  • the process of the present invention begins with the atomization, partial combustion and gasification of a mixed organic/inorganic waste stream resulting from the digestion of wood or other lignocellulosic materials.
  • An oxidant such as air or oxygen is used for the partial combustion.
  • the method and apparatus of the present invention will likely find first commercial application to the processing of black liquor produced in the well known kraft pulping and recovery process, the present invention is not limited to that particular type of pulping process.
  • the present invention can also be applied to process alkaline, acidic, or neutral sulfite spent liquors, as well as polysulfide spent liquors.
  • black liquor or “smelt” are commonly used in connection with the kraft pulping process, while sulfite spent liquors are commonly called “red” liquors and not “black”, and polysulfite pulping liquor is commonly called “ orange” liquor and not “white” liquor.
  • the present invention employs the term "lignocellulosic" to encompass all of the various types of feed stocks which one might want to employ in a pulping process, to broadly include woody and non- woody plants, whether or not the kraft type pulping process or other types of pulping processes are employed.
  • lignocellulosic to encompass all of the various types of feed stocks which one might want to employ in a pulping process, to broadly include woody and non- woody plants, whether or not the kraft type pulping process or other types of pulping processes are employed.
  • STEAM Its Generation and Use 40 th Ed., Stultz and Kitto, Eds., ⁇ 1992
  • the Babcock & Wilcox Company particularly to Chapter 26 - Chemical and Heat Recovery in the Paper Industry, the text of which is hereby incorporated by reference as though fully set forth herein.
  • a gasifier 70 of the invention is required, and preferably comprises a water jacketed, refractory lined vessel where a waste stream produced by the digestion of lignocellulosic materials, such as black liquor 72, typically containing less than 40% water is atomized and partially combusted with an oxidant 74, such as air or preferably oxygen or mixtures thereof.
  • the gasifier 70 operates in a pressure range from atmospheric up to 800 psia, and preferably 300 to 600 psia.
  • a stream 78 leaving the gasifier 70 will be in the temperature range of 1600 to 2200 F, typically about 1800 F and comprises fuel gas 76 constituents, molten salts referred to in the pulp and paper industry as "smelt" (in a kraft recovery process), and a sub-micron sized mixture of alkali fume and soot.
  • the molten smelt comprises relatively large molten droplets and or streams which flow down the walls of the gasifier 70 towards a quencher 26.
  • a relatively coarse spray comprising a mixture 29 of weak wash 28 (a slightly alkaline solution) and condensate with dissolved fume 100, is used to cool the fuel gas 76 to its adiabatic saturation temperature, which is typically in the range of about 300 to 400 F. While the evaporative cooling takes place in the quencher 26, the smelt constituents are collected quantitatively by the quench spray and dissolved therein. The resulting mixture 30 is sulfide lean and is known as green liquor. This stream 30 of green liquor will be subsequently causticized to white liquor in the slaker/causticizer 12. That portion of the process will be described in more detail later.
  • the raw fuel gas 76 upon leaving the gasifier quencher 26, will typically contain about 3500 ppm of H 2 S, about 8% CO 2 , a water content of over 1.75 lbs H 2 O/lb dry gas, and a fume concentration as high as 800 grains per ft 3 of fuel gas 76.
  • a three-step process 80 (shown in greater detail in Fig. 4) is employed according to the present invention.
  • a first venturi scrubber 82 first contacts the fuel gas 76.
  • the venturi scrubber 82 depicted in Fig. 4 will typically operate at a pressure drop of about 2 to 5 psi.
  • Scrubber 82 uses a circulation of water 88 from a circulation pump 90, for example, through venturi 86 where the aqueous spray contacts the fuel gas 76 in the throat of the venturi 86.
  • the water 88 may be taken from the quencher stream 100.
  • the relatively high gas velocity (> 200 ft/sec) and low liquid flow rate ( ⁇ 1 lb liquid/lb gas) promotes atomization of the liquid in the venturi throat and subsequent inertial impaction between the liquid droplets and the fume particles in venturi scrubber enclosure 84.
  • the purpose of this first venturi scrubber 82 is to reduce the dust loading of the fuel gas 76 to less than about 8 grains/ft 3 .
  • the fuel gas 76 is cooled (schematically indicated at 91 in Fig. 4) and the water content is reduced to less than about 0.35 lb H 2 O/lb dry gas.
  • Three separate approaches are available for this task.
  • the fuel gas 76 can be cooled in a heat exchanger 91 , advantageously a condensing heat exchanger, using cold, high-pressure process water from the mill or another source such as a cooling tower. After exiting the heat exchanger 91 , the cooling water will be heated sufficiently for use in resaturating the fuel gas 76 after the H 2 S removal operation (at 106) as described below. Thus, energy removed from the fuel gas 76 during the particulate control operations can be efficiently returned to the fuel gas later in the process.
  • the fuel gas 76 can be cooled in the first venturi scrubber 82 by using cooled water from 89 as the aqueous spray 88.
  • the heat absorbed by this water in the venturi scrubber 82 can be rejected by a liquid-to-liquid heat exchanger.
  • the water condensed from the fuel gas 76 in this manner leaves the venturi 86 as blowdown 101.
  • the fuel gas 76 can be passed through a boiler 91 to generate steam for use within the paper making process.
  • the reduction in water content of the fuel gas 76 from 1.75 to 0.35 lb H 2 O/lb dry gas represents a greater than 50% reduction in total volumetric flow rate of fuel gas 76.
  • the fuel gas treatment equipment to follow is greatly reduced in size.
  • the fuel gas 76 with the dust loading reduced to less than 8 grains/ft 3 enters an electrostatic agglomerator-venturi scrubber arrangement depicted in Fig. 4.
  • the electrostatic agglomerator (ESA) 92 is sized to collect at least 99.9% of the fume and soot not captured by the first venturi scrubber 82.
  • the ESA 92 is designed to temporarily retain the collected material on the walls of its collection tubes 94 whereby it is re-entrained by the suitable use of rappers (not shown).
  • a second venturi scrubber 96 subsequently captures the agglomerated solids.
  • a source of water from quench stream 100, and a blowdown stream 103 may be employed as described above in connection with the first venturi scrubber 82.
  • sour fuel gas 98 Upon leaving the particulate control section 80, sour fuel gas 98 will contain about 7700 ppm H 2 S and about 17% CO 2 . The temperature will be about 325 F. This fuel gas 98 temperature is too hot to be effectively treated by conventional absorption-stripping processes for H 2 S removal.
  • the fuel gas 98 be cooled further.
  • This cooling preferably takes place in another heat exchanger 99 again preferably a condensing heat exchanger, to cool the fuel gas stream 98.
  • the fuel gas 98 water content has been lowered to about 0.01 lb H 2 O/ lb dry fuel gas.
  • the H 2 S concentration is raised to 10,900 ppm and the CO 2 concentration is 24.4%.
  • the water condensed from the fuel gas stream in the two heat exchangers 91, 99 (or alternate devices as described) and blowdown streams 101, 103 from the two venturi scrubbers 82, 96 are collected and sent to the quencher stream 100.
  • this aqueous stream is to control the concentration of salts in the green liquor 30.
  • the pulp and paper mill requires that the green liquor salt concentration be within a specified range; typically 120-130 g/L as Na 2 O.
  • the water collected from the two venturi scrubbers and the heat exchangers is also contaminated with low levels of salts from the alkaline fume carryover. By taking this water back to the quencher 26, all alkali compounds are returned to the process.
  • the sour fuel gas 98 next enters an absorption column 102 (part of a sulfur removal system generally designated 105) where H 2 S is preferentially absorbed from the fuel gas 98.
  • the column 102 is designed to remove over 99% of the H 2 S in the fuel gas. Some CO 2 is also removed from the fuel gas 98 in this absorption column.
  • Chemical solvents such as methyldiethanolamine, MDEA, or a physical solvent such as the SELEXOL solvent can be used here.
  • the fuel gas 98 leaving the absorption column at 104 is next contacted with a stream of hot water and/or steam at 106.
  • the hot water can come from the condensing heat exchanger 91 after the first venturi scrubber 82 as described earlier.
  • the purpose is to produce reheated and humidified fuel gas 109 which is provided into a gas turbine 110.
  • the fuel gas 109 is heated to a suitable temperature for the selected gas turbine.
  • a suitable temperature for the selected gas turbine For example, for a General Electric Model 6FA gas turbine the fuel gas 109 is reheated to about 385 F, a water content of about 0.5 lb H 2 O/lb dry fuel gas, and a pressure of about 300 psia.
  • these gases are throttled before mixing with the combustion air in such a manner that the combustor 112 operates at about 50 psi below the fuel gas 109 inlet pressure.
  • the gas turbine 110 is coupled to both an electric generator 117 and to a compressor
  • the system is flexible and can easily accommodate other gas turbine requirements.
  • the hot exhaust gases 120 leave the gas turbine 110 at a temperature above about 1000 F. These gases 120 contain in excess of 10% oxygen. Since these gases 120 are well above the auto-ignition temperature of natural gas, additional heat can be added to the turbine exhaust gases 120 by contacting these gases with natural gas in a duct burner 122. In this manner, the gases can be heated to above 1500 F before entry into a waste heat boiler 124. This permits the generation of high pressure steam at, for example, 1250 psi and 925 F, but again other steam cycles can be used. This steam is suitable for use in a back pressure steam turbine 126 to produce electric power via electric generator 127, and also process steam.
  • the solvent used in the abso ⁇ tion step is transferred to a stripping column 107 where the pressure is reduced preferably to less than 30 psia.
  • the solvent is then regenerated by heating.
  • the combination of low pressure and high temperature causes the absorbed H 2 S and CO 2 to evolve from the solvent into the gas phase.
  • This unit operation is known as solvent regeneration.
  • the gas 134 that evolves from the stripping column 107 is referred to as acid gas since it contains mostly H 2 S and CO 2 .
  • the lean solvent leaving the stripping column is cooled and pumped to the pressure of the abso ⁇ tion column 102 for reuse.
  • the cooling is accomplished by contacting the lean solvent with the rich solvent in a liquid-liquid heat exchanger or an air cooled heat exchanger.
  • the H 2 S selectivity of the abso ⁇ tion-stripping process is critical.
  • the ratio of H 2 S to CO 2 in the raw, sour fuel gas 98 entering the abso ⁇ tion column will be on the order of 1 part H 2 S to 20 parts CO 2 on a molar basis.
  • the H 2 S to CO 2 ratio in the acid gas leaving the steam stripper must be at least 1 part H 2 S to 1 part CO 2 .
  • a ratio of 4 parts H 2 S to 1 part CO 2 or higher is preferred.
  • the SELEXOL process available from UOP Canada Inc., Toronto, Canada, is one of the processes capable of this degree of H 2 S selectivity.
  • SELEXOL is a trademark of UOP Canada Inc. for its process and a solvent used in the process.
  • the acid gases 134 are next contacted with sulfide lean white liquor 140 in an abso ⁇ tion column 136 designed to have a high selectivity for H 2 S abso ⁇ tion over CO 2 .
  • the sulfide can be returned to the pulping liquor stream as white liquor 138 without significant carbonation thereof.
  • the white liquor 138 can in this manner be used directly in the pulping process without further chemical processing.
  • the production of pulping liquor for the digestion of wood chips begins (in the context of a black liquor gasification process) with the production of green liquor 30 in the quencher 26.
  • the green liquor consists of a mixture of sodium carbonate, sodium hydroxide, and sodium sulfide.
  • the weak wash 28 is produced when fresh water is used to wash white liquor from the filter cake of calcium carbonate that is produced in the causticizing operations at 12. This weak wash is shown as stream 28 in Fig. 3. From a chemical composition standpoint, the weak wash 28 can be thought of as dilute white liquor.
  • the recycled water contains low levels of alkali compounds from the fume carryover.
  • the recycled water is shown as stream 100 in Fig. 3.
  • the calcium carbonate is produced as a suspended solid when green liquor contacts an aqueous suspension of calcium hydroxide in the causticizing plant 12.
  • the solid calcium hydroxide reacts with the dissolved sodium carbonate to produce dissolved sodium hydroxide and solid calcium carbonate.
  • Soot (a sub-micron sized carbonaceous aerosol) that is caught by the venturi scrubbers 82 and 96 is removed from the aqueous phase at the mud filter 38 leaves the process by combustion in the lime kiln 16.
  • the green liquor stream 30 leaving the quencher 26 differs substantially from that of a conventional kraft recovery process as illustrated in Fig. 1.
  • Green liquor stream 30 in Fig. 3 will contain as little as 50% of the sulfide of a conventional green liquor. That situation results from the much greater partition of sulfur as H 2 S in the gas phase of the gasification process.
  • This is one of the principal differences between black liquor gasification (BLG) and conventional kraft recovery. This difference provides the opportunity for several process improvements over conventional kraft recovery.
  • the BLG scheme offers a causticizing improvement.
  • One of the means by which sulfur is lost from the conventional kraft recovery process is through the precipitation of calcium sulfide (CaS).
  • This precipitated CaS is separated along with the calcium carbonate (lime mud 40) on the vacuum filter 38 from the white liquor.
  • This lime mud is then separated and taken to the rotary lime kiln 16 where any calcium sulfide co-mingled with the calcium carbonate is decomposed to CaO and SO 2 .
  • the green liquor since the green liquor is lean of sulfide, there is a proportionate reduction of calcium sulfide mixed with the lime mud sent to the kiln 16.
  • Another advantage of the low sulfidity green liquor in the BLG process is the fact that the white liquor produced from this green liquor will have a proportionately lower sulfidity.
  • the Tomlinson recovery boiler is the current standard method and apparatus for chemical recovery in the kraft pulping process.
  • Recovery boilers are costly, prone to corrosion and catastrophic smelt-water explosions and are limited to relatively modest steam temperatures and pressures. These limits constrain the ability of this standard technology to effect improvements in electric power production. Black liquor gasification is widely viewed as the technology most likely to replace the recovery boiler.
  • BLG systems can provide more efficient utilization of black liquor fuel value and produce more electrical power relative to steam. This is an attractive feature for future mills where higher electrical usage will be required to operate mechanical pulping and pollution control equipment. Smelt-water explosions are a serious risk associated with recover)' boilers and most BLG concepts eliminate the possibility of these catastrophic events. Unlike recovery boilers, BLG systems recover sodium and sulfur as separate streams which can be blended to produce a wide range of pulping liquor composition. This increased process flexibility of BLG may be a significant asset in future kraft pulping operations.
  • the specific embodiment of the present invention offers advantages that constitute improvements over other BLG systems.
  • Other BLG processes can cause a significant burden on the causticizing plant, because of co-abso ⁇ tion of CO 2 . This process avoids that problem by including the abso ⁇ tion-stripping process that greatly increases the ratio of H 2 S to CO 2 in the gas that contacts the white liquor. This process provides means to eliminate alkali fume problems that could be a problem in other BLG processes.
  • the process and apparatus described in the present invention can realistically reduce fume and aerosol emissions below the gas turbine allowable limits.
  • the rapid quench of fuel gas from 1800 F to about 400 F by adiabatic humidification represents a significant portion of the chemical energy in the black liquor, or other type of waste stream.
  • the means used to reclaim that energy into useful form is a challenge for any BLG process.
  • the use of a heat exchanger or boiler to raise process steam between the first venturi 82 and the ESA 92 is an efficient way to recover nearly all of that waste heat as low-pressure (nominally about 80 psig) steam. This steam can be used as process steam throughout the pulp mill.
  • a condensing heat exchanger could be used to raise the temperature of high-pressure water from about 130 F to about 340 F. This hot, high-pressure water can then be contacted with the fuel gas in a saturator as at 106. The excess water that is not evaporated into the fuel gas is cooled in a liquid-to-liquid heat exchanger, increased in pressure and sent back to the condensing heat exchanger thus forming a closed-loop system. In this embodiment, the heat that is not returned to the fuel gas in the form of water vapor is simply rejected from the system. In an alternate embodiment an economizer section from a boiler could be used in place of the condensing heat exchanger. Here, the fuel gas would generate low-pressure steam that could be used elsewhere in the paper plant.
  • the process by which the H 2 S is scrubbed from the fuel gas and delivered to the white liquor is subject to various possibilities.
  • SELEXOL process is the preferred means, other abso ⁇ tion-stripping processes are suitable for this gasification process.
  • Sterically hindered tertiary amines such as methyldiethanolamine are one such compound that can be used in a conventional abso ⁇ tion-stripping process.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Treating Waste Gases (AREA)
  • Paper (AREA)
  • Industrial Gases (AREA)

Abstract

L'invention concerne un procédé et un appareil de production de gaz combustible propre non corrosif s'utilisant dans un processus de combustion. Ledit procédé consiste à traiter un flux de déchets provenant de la digestion de matières lignocellulosiques, en oxydant partiellement le flux de déchets afin de former des gaz chauds et des sels fondus, puis en faisant refroidir les gaz chauds et les sels fondus à l'aide d'une liqueur de trempe pour former un gaz trempé (76) et une liqueur carbonate (30). Des particules sont retirées du gaz trempé pour former un gaz combustible brut en soumettant le gaz trempé à un processus à phases multiples de réduction d'émanations (80), comprenant l'extraction de la chaleur (91) du gaz trempé afin de réduire la charge de particules et le contenu en eau du gaz trempé pour former un gaz combustible à faibles émanations. H2S est retiré du gaz combustible à faibles émanations à l'aide d'un processus de retrait de H2S (105) qui est plus sélectif pour H2S qu'il ne l'est pour CO2, la phase de retrait formant un gaz combustible propre non corrosif et des gaz acides.
PCT/US2000/010995 1999-04-23 2000-04-21 Procede de gazeification de liqueur residuaire a haute temperature et haute pression Ceased WO2000065150A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU46596/00A AU4659600A (en) 1999-04-23 2000-04-21 Gasification process for spent liquor at high temperature and high pressure
CA002370968A CA2370968C (fr) 1999-04-23 2000-04-21 Procede de gazeification de liqueur residuaire a haute temperature et haute pression

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US29853399A 1999-04-23 1999-04-23
US09/298,533 1999-04-23

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WO2000065150A1 true WO2000065150A1 (fr) 2000-11-02
WO2000065150A9 WO2000065150A9 (fr) 2002-04-18

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EP2592186A1 (fr) * 2011-11-08 2013-05-15 Södra Cell AB Procédé de réduction en pâte kraft

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Publication number Priority date Publication date Assignee Title
CN101012925B (zh) * 2007-01-31 2012-08-22 徐建明 烃燃料与水或水蒸汽燃烧产生的废气回收后再循环燃烧利用的方法
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