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WO2012029279A1 - Exhaust gas treatment device - Google Patents

Exhaust gas treatment device Download PDF

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Publication number
WO2012029279A1
WO2012029279A1 PCT/JP2011/004794 JP2011004794W WO2012029279A1 WO 2012029279 A1 WO2012029279 A1 WO 2012029279A1 JP 2011004794 W JP2011004794 W JP 2011004794W WO 2012029279 A1 WO2012029279 A1 WO 2012029279A1
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WO
WIPO (PCT)
Prior art keywords
exhaust gas
mercury
gas treatment
treatment apparatus
denitration
Prior art date
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Ceased
Application number
PCT/JP2011/004794
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French (fr)
Japanese (ja)
Inventor
宍戸　聡
石岡　正明
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Mitsubishi Power Ltd
Original Assignee
Babcock Hitachi KK
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Filing date
Publication date
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Priority to GB1303447.5A priority Critical patent/GB2498272B/en
Priority to CN2011800408000A priority patent/CN103079692A/en
Publication of WO2012029279A1 publication Critical patent/WO2012029279A1/en
Anticipated expiration legal-status Critical
Ceased 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
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/75—Multi-step processes
    • 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
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur 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
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
    • B01D53/502—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound characterised by a specific solution or suspension
    • 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
    • B01D53/46—Removing components of defined structure
    • B01D53/64—Heavy metals or compounds thereof, e.g. mercury
    • 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
    • B01D53/46—Removing components of defined structure
    • B01D53/68—Halogens or halogen compounds
    • 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
    • B01D53/77—Liquid phase processes
    • 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
    • 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
    • B01D53/92—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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/063—Titanium; Oxides or hydroxides thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/24—Chromium, molybdenum or tungsten
    • B01J23/30—Tungsten
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
    • C10L5/00—Solid fuels
    • 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
    • B01D2252/00—Absorbents, i.e. solvents and liquid materials for gas absorption
    • B01D2252/10—Inorganic absorbents
    • B01D2252/103—Water
    • B01D2252/1035—Sea water
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/102—Carbon
    • 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
    • B01D2255/20707—Titanium
    • 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
    • B01D2255/20776—Tungsten
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/20—Halogens or halogen compounds
    • B01D2257/204—Inorganic halogen compounds
    • B01D2257/2045—Hydrochloric acid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/30—Sulfur compounds
    • B01D2257/302—Sulfur oxides
    • 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
    • B01D2257/00—Components to be removed
    • B01D2257/60—Heavy metals or heavy metal compounds
    • B01D2257/602—Mercury or mercury compounds
    • 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
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Definitions

  • the present invention relates to an exhaust gas treatment apparatus, and more particularly, to a technology for removing sulfur oxides in acidic exhaust gas containing mercury generated by coal combustion by absorbing it into seawater.
  • Patent Document 1 acidic exhaust gas containing nitrogen oxides and sulfur oxides generated by coal combustion is introduced into a denitration apparatus, and nitrogen oxides are reduced with a reducing agent such as ammonia in the presence of a catalyst, and denitration is performed.
  • a reducing agent such as ammonia in the presence of a catalyst
  • an exhaust gas treatment apparatus that removes sulfur oxide in acidic exhaust gas discharged from the apparatus by absorbing it in a calcium-based absorption liquid.
  • mercury contained in acidic exhaust gas reacts with halogens such as chlorine contained in the exhaust gas by the catalyst of the denitration device and is converted to mercury oxide. It is described that it is absorbed and removed by the absorbent. Therefore, this document promotes the generation reaction of mercury oxide in the denitration apparatus to remove mercury.
  • Patent Document 2 when a desulfurization apparatus is constructed near the sea, it is proposed to use seawater as an absorbent for the desulfurization apparatus in order to perform desulfurization at a low cost.
  • seawater is sprayed on exhaust gas containing sulfur oxide to absorb the sulfur oxide in the seawater, and then the seawater is neutralized with calcium carbonate and returned to the sea.
  • the problem to be solved by the present invention is to use seawater as the absorbing liquid of the desulfurization apparatus, and to suppress the mercury concentration in the discharged seawater below the allowable value without providing any special waste water treatment.
  • the present invention provides a denitration device for reducing nitrogen oxides in acidic exhaust gas by adding a reducing agent to acidic exhaust gas containing mercury generated by coal combustion, and in the presence of a catalyst,
  • a desulfurization device that absorbs and removes sulfur oxides in acidic exhaust gas discharged from the device into seawater, and the temperature of the acidic exhaust gas on the inlet side of the denitration device suppresses the generation reaction of mercury oxide in the denitration device, and the desulfurization device
  • the mercury oxide concentration at the inlet side is set to a temperature that is lower than the set value.
  • the concentration of mercury oxide in the acidic exhaust gas introduced into the desulfurization device can be controlled and absorbed by seawater that is the absorption liquid of the desulfurization device.
  • the mercury concentration in the released seawater can be kept below the allowable value. Therefore, it is not necessary to perform wastewater treatment to remove mercury from the discharged seawater.
  • the set value of the mercury oxide concentration at the desulfurizer inlet side is appropriately selected according to the allowable value of the mercury concentration in the discharged seawater.
  • the acidic exhaust gas temperature at the inlet side of the denitration device can be set to a temperature at which the mercury concentration in the discharged seawater discharged from the desulfurization device is lower than the set value. That is, an allowable value of mercury concentration in seawater, which is an absorbing liquid discharged from the desulfurization apparatus or circulated to the desulfurization apparatus, is set so that the mercury concentration in the discharged seawater is less than the allowable value (standard value).
  • the acidic exhaust gas temperature at the inlet side of the denitration device is set so that the mercury concentration in the seawater is detected and the allowable value is satisfied.
  • a mercury adsorption device for adsorbing and removing mercury in the acidic exhaust gas on the downstream side of the desulfurization device. According to this, the mercury concentration in the exhaust gas discharged from the exhaust gas treatment device can be reduced.
  • the acidic exhaust gas temperature at the inlet side of the denitration apparatus can be appropriately set according to the allowable value of the mercury concentration in the discharged seawater, and can be set to be 400 ° C. or higher at 100% load, for example. That is, since the generation reaction of mercury oxide in the denitration apparatus is suppressed at a high temperature, it is preferable to increase the temperature of the acidic exhaust gas on the denitration apparatus inlet side. In this case, if the acidic exhaust gas temperature at the inlet side of the denitration device is excessively increased, the denitration rate may be lowered or the heat resistance temperature of the catalyst or the like may be exceeded. Therefore, it is preferable that the acidic exhaust gas temperature at the inlet side of the denitration apparatus is, for example, 450 ° C. or less.
  • the production reaction of mercury oxide in the denitration apparatus is promoted when the chlorine concentration in the acidic exhaust gas is high, it is preferable to burn the coal after washing it with water to reduce the chlorine content in the coal. According to this, since the chlorine concentration in the acidic exhaust gas introduced into the denitration apparatus can be reduced, the generation reaction of mercury oxide can be suppressed.
  • the concentration of mercury in the discharged seawater can be suppressed to an allowable value or less without using seawater as the absorption liquid of the desulfurization apparatus and providing a special waste water treatment.
  • the exhaust gas treatment apparatus 1 of the present embodiment is connected to, for example, a boiler 3 that burns coal, and exhaust gas discharged from the boiler 3, for example, acidic components such as nitrogen oxides and sulfur oxides In addition, exhaust gas containing mercury and mercury is cleaned.
  • the exhaust gas treatment device 1 is provided with a denitration device 7 for denitrating exhaust gas by a selective catalytic reduction method, for example.
  • the denitration device 7 is configured to add a reducing agent 5 such as ammonia to the exhaust gas to reduce nitrogen oxides in the exhaust gas in the presence of a catalyst.
  • a reducing agent 5 such as ammonia
  • an air preheater 9 that heats combustion air of the boiler 3 with exhaust gas is provided.
  • a dust collector 11 that collects particulate matter such as fly ash in the exhaust gas and removes it from the exhaust gas.
  • the desulfurization device 13 is configured to spray seawater pumped by a pump or the like onto the exhaust gas, for example. Thereby, the sulfur oxide in exhaust gas can be absorbed and removed by seawater.
  • the desulfurization device 13 is provided with a purification device (not shown), which removes sulfur oxides absorbed in seawater and discharges the seawater from which sulfur oxides have been removed to the sea.
  • the desulfurization apparatus 13 can be selected as appropriate, such as a circulation type that discharges seawater that is an absorption liquid after circulation, or a one-through type that discharges seawater that has been used once without circulation.
  • a mercury adsorbing device 15 for adsorbing and removing mercury in the exhaust gas is provided on the outlet side of the desulfurization device 13.
  • the mercury adsorption device 15 is provided with, for example, an adsorption tower 17 filled with activated carbon capable of adsorbing mercury and a regeneration tower 19 that removes the mercury adsorbed on the activated carbon and regenerates the activated carbon.
  • a chimney is provided on the outlet side of the mercury adsorption device 15 so as to discharge the purified exhaust gas into the atmosphere.
  • the exhaust gas temperature at the inlet side of the denitration device 7 is set to a temperature at which the detected value or design value of the mercury oxide concentration at the inlet side of the desulfurization device 13 is equal to or less than the set value.
  • the exhaust gas temperature at the inlet side of the denitration device 7 can be set by appropriately adjusting, for example, the heat transfer area of the economizer in the boiler 3 or the amount of water supplied through the boiler 3. Thereby, the exhaust gas temperature at the inlet side of the denitration device 7 is set to a temperature at which the mercury oxide production reaction in the denitration device 7 is suppressed, for example, 400 ° C. or more.
  • the set value of the mercury oxide concentration is appropriately set according to the standard of the allowable limit of the mercury concentration in the discharged seawater of the desulfurization apparatus 13. That is, the mercury concentration in the effluent seawater correlates with the mercury oxide concentration on the inlet side of the desulfurization device 13, and the mercury oxide concentration on the inlet side of the desulfurization device 13 can be adjusted by the exhaust gas temperature on the inlet side of the denitration device 7.
  • the exhaust gas temperature at the inlet side of the denitration device 7 is set so that the mercury oxide concentration at the inlet side is not more than the set value.
  • Nitrogen oxides in the exhaust gas discharged from the boiler 3 are denitrated by the denitration device 7.
  • the denitrated exhaust gas is introduced into the air preheater 9 and reduced in temperature by heat exchange with the combustion air of the boiler 3.
  • the particulate matter such as ash and unburned carbon in the exhaust gas whose temperature has been reduced is removed from the exhaust gas by the dust collector 11.
  • the exhaust gas discharged from the dust collector 11 is sprayed with seawater by the desulfurization device 13, and the sulfur oxide in the exhaust gas is absorbed into the seawater and desulfurized. Seawater that has absorbed sulfur oxides, for example, is discharged into the sea after being purified to remove sulfur oxides.
  • the exhaust gas discharged from the desulfurization device 13 is introduced into the adsorption tower 17 of the mercury adsorption device 15. Thereby, the metallic mercury in the exhaust gas is adsorbed by the adsorbent such as activated carbon and removed from the exhaust gas.
  • the exhaust gas from which mercury has been removed is, for example, heated by a reheater and then released from the chimney 21 into the atmosphere.
  • the exhaust gas temperature on the inlet side of the denitration device 7 is set to a temperature that suppresses the generation reaction of mercury oxide so that the mercury oxide concentration on the inlet side of the desulfurization device 13 is not more than the set value.
  • the mercury oxide concentration in the seawater that is the absorption liquid of the desulfurization device 13 is detected, and the exhaust gas temperature on the inlet side of the denitration device 7 is reduced so that the generation reaction of mercury oxide is suppressed so that the detected value is lower than the set value.
  • Set to the desired temperature That is, an allowable value of mercury concentration in seawater that is an absorption liquid discharged from the desulfurization apparatus 13 or circulated to the desulfurization apparatus 13 is set, and the mercury concentration in seawater as the absorption liquid is less than the allowable value.
  • the exhaust gas temperature on the inlet side of the denitration device 7 can be set. Thereby, since the mercury concentration in the discharged seawater discharged from the desulfurization apparatus 13 can be set to a set value or less, it is not necessary to provide a treatment facility for removing mercury.
  • the exhaust gas temperature on the inlet side of the denitration device 7 can be set to 400 ° C. or higher at 100% load, for example. preferable. If the exhaust gas temperature at the inlet side of the denitration device 7 is excessively high, there is a risk that the NOx removal rate will decrease and the heat resistance temperature of the catalyst or the like may be exceeded. It is preferable to do.
  • Example 1 is an example in which the denitration rate is set to 90% and the exhaust gas temperature at the inlet side of the denitration device 7 is set to 400 ° C. in the denitration device 7 using titanium oxide as a catalyst.
  • Comparative Example 1 is an example in which the exhaust gas temperature on the inlet side of the denitration device 7 is set to 350 ° C. under the conditions of Example 1.
  • Comparative Example 2 is an example in which the exhaust gas temperature at the inlet side of the denitration device 7 is set to 380 ° C.
  • Table 1 shows the results of actual measurement of the mercury oxide production rate in Example 1 and Comparative Examples 1 and 2. Other measurement conditions are as shown in Table 1.
  • Example 1 in which the exhaust gas temperature at the inlet side of the denitration device 7 was set to 400 ° C. can suppress the generation of about 82% mercury oxide compared with Comparative Example 1 set to 350 ° C., and was set to 380 ° C.
  • Comparative Example 2 it was possible to suppress the generation of about 67% mercury oxide. That is, it can be seen that the mercury oxide production reaction correlates with temperature, and that the mercury oxide production reaction can be suppressed as the temperature increases.
  • the production reaction of mercury oxide can be adjusted by the exhaust gas temperature on the inlet side of the denitration device 7 and the concentration of mercury oxide in the exhaust gas introduced into the desulfurization device 13 can be controlled, so that the mercury oxide absorbed in the seawater of the desulfurization device 13 is reduced.
  • the mercury concentration in the released seawater can be made below the allowable value.
  • Example 2 in which a catalyst obtained by adding tungsten as a co-catalyst to titanium oxide was used as Example 2 for the catalyst of Example 1 in which the inlet side exhaust gas temperature of the denitration apparatus 7 was set to 400 ° C. Moreover, the example which burned after performing the water washing process of the coal of Example 2 was made into Example 3.
  • Table 2 shows the results of actual measurement of the mercury oxide production rate (mercury oxidation rate) in Examples 2 to 4. Other measurement conditions are the same as in Example 1.
  • the production reaction of mercury oxide can be further suppressed as compared with Example 1. That is, the exhaust gas temperature at the inlet side of the denitration device 7 is set to 400 ° C., and the catalyst is formed from titanium oxide to which tungsten (W) is added, whereby the generation reaction of mercury oxide can be further suppressed.
  • mercury mercury reacts with mercury metal to produce mercury oxide, as shown in Example 3, it can be burned after the coal is washed with water to reduce the chlorine content in the coal. According to this, the chlorine content in the exhaust gas discharged from the boiler 3 can be reduced, and the production of mercury oxide can be suppressed. Further, when the required denitration rate is, for example, 80% as shown in Example 4, the production reaction of mercury oxide by the catalyst can be suppressed by reducing the amount of catalyst installed in the denitration device 7.
  • the generation reaction of mercury oxide in the desulfurization apparatus 13 can be suppressed and the concentration of mercury oxide in the exhaust gas introduced into the desulfurization apparatus 13 can be reduced, so that it is absorbed by the seawater of the desulfurization apparatus 13.
  • Mercury oxide can be reduced, and the mercury concentration in the discharged seawater can be reduced below the allowable value.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Biomedical Technology (AREA)
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  • General Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
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  • Materials Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • Treating Waste Gases (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Catalysts (AREA)
  • Solid Fuels And Fuel-Associated Substances (AREA)

Abstract

A denitrification device (7) which adds a reducing agent to acidic exhaust gas which includes mercury, produced by combustion of coal, and reduces nitrogen oxides in the acidic exhaust gas in the presence of a catalyst, and a desulphuration device (13) which removes sulphur oxides in the acidic exhaust gas discharged from the denitrification device (7), by absorption in sea water, are provided/ and by setting the temperature of the acidic exhaust gas on the inlet side of the denitrification device (7) to a temperature such that reactions producing mercury oxides are suppressed in the denitrification device (7) and the concentration of mercury oxides on the inlet side of the desulphuration device (13) is no more than a set value, the mercury concentration in sea water released from the desulphuration device (13) is kept no higher than the permitted value.

Description

排ガス処理装置Exhaust gas treatment equipment

　本発明は、排ガス処理装置に係り、特に、石炭の燃焼により発生した水銀を含む酸性排ガス中の硫黄酸化物を海水に吸収させて除去する技術に関する。 The present invention relates to an exhaust gas treatment apparatus, and more particularly, to a technology for removing sulfur oxides in acidic exhaust gas containing mercury generated by coal combustion by absorbing it into seawater.

　例えば、特許文献１には、石炭の燃焼により発生した窒素酸化物及び硫黄酸化物を含む酸性排ガスを脱硝装置に導入し、触媒存在下でアンモニア等の還元剤により窒素酸化物を還元し、脱硝装置から排出された酸性排ガス中の硫黄酸化物をカルシウム系等の吸収液に吸収させて除去する排ガス処理装置が提案されている。また、同文献には、酸性排ガス中に含まれている水銀は、脱硝装置の触媒により同排ガス中に含まれる塩素等のハロゲンと反応して酸化水銀に変換され、この酸化水銀は脱硫装置の吸収液に吸収されて除去されることが記載されている。そこで、同文献は、脱硝装置における酸化水銀の生成反応を促進させて水銀の除去を行うようにしている。 For example, in Patent Document 1, acidic exhaust gas containing nitrogen oxides and sulfur oxides generated by coal combustion is introduced into a denitration apparatus, and nitrogen oxides are reduced with a reducing agent such as ammonia in the presence of a catalyst, and denitration is performed. There has been proposed an exhaust gas treatment apparatus that removes sulfur oxide in acidic exhaust gas discharged from the apparatus by absorbing it in a calcium-based absorption liquid. In the same document, mercury contained in acidic exhaust gas reacts with halogens such as chlorine contained in the exhaust gas by the catalyst of the denitration device and is converted to mercury oxide. It is described that it is absorbed and removed by the absorbent. Therefore, this document promotes the generation reaction of mercury oxide in the denitration apparatus to remove mercury.

　一方、特許文献２には、海の近くに脱硫装置を建設する場合、脱硫を安価に行うために、脱硫装置の吸収液に海水を利用することが提案されている。同文献は、硫黄酸化物を含む排ガスに海水を噴霧して海水に硫黄酸化物を吸収させた後、海水を炭酸カルシウムで中和処理して海に戻すようにしている。 On the other hand, in Patent Document 2, when a desulfurization apparatus is constructed near the sea, it is proposed to use seawater as an absorbent for the desulfurization apparatus in order to perform desulfurization at a low cost. In this document, seawater is sprayed on exhaust gas containing sulfur oxide to absorb the sulfur oxide in the seawater, and then the seawater is neutralized with calcium carbonate and returned to the sea.

特開２００９－２２６２３８号公報JP 2009-226238 A 特開平８－２０６４４７号公報JP-A-8-206447

　しかしながら、特許文献１の脱硫装置の吸収液に、特許文献２に記載の海水を用いた場合、海水中に酸化水銀が溶け込んでしまうため、海水を放流する際に中和処理するだけでは、有害物質である水銀を除去することができない。そこで、放流する海水から水銀を除去するための排水処理を行わなければならないから、脱硫装置の吸収液として海水を用いる利点がない。 However, when the seawater described in Patent Document 2 is used for the absorption liquid of the desulfurization apparatus of Patent Document 1, mercury oxide dissolves in the seawater. The substance mercury cannot be removed. Therefore, there is no advantage of using seawater as the absorbent of the desulfurization apparatus because wastewater treatment for removing mercury from the seawater to be discharged must be performed.

　本発明が解決しようとする課題は、脱硫装置の吸収液として海水を用い、かつ、格別な排水処理を設けることなく、放流海水中の水銀濃度を許容値以下に抑えることにある。 The problem to be solved by the present invention is to use seawater as the absorbing liquid of the desulfurization apparatus, and to suppress the mercury concentration in the discharged seawater below the allowable value without providing any special waste water treatment.

　上記の課題を解決するため、本発明は、石炭の燃焼により発生した水銀を含む酸性排ガスに、還元剤を添加して触媒存在下で酸性排ガス中の窒素酸化物を還元する脱硝装置と、脱硝装置から排出される酸性排ガス中の硫黄酸化物を海水に吸収させて除去する脱硫装置とを備え、脱硝装置の入口側の酸性排ガス温度は、脱硝装置における酸化水銀の生成反応を抑えて脱硫装置の入口側の酸化水銀濃度が設定値以下になるような温度に設定されることを特徴とする。 In order to solve the above-mentioned problems, the present invention provides a denitration device for reducing nitrogen oxides in acidic exhaust gas by adding a reducing agent to acidic exhaust gas containing mercury generated by coal combustion, and in the presence of a catalyst, A desulfurization device that absorbs and removes sulfur oxides in acidic exhaust gas discharged from the device into seawater, and the temperature of the acidic exhaust gas on the inlet side of the denitration device suppresses the generation reaction of mercury oxide in the denitration device, and the desulfurization device The mercury oxide concentration at the inlet side is set to a temperature that is lower than the set value.

　これによれば、脱硝装置入口側の温度により酸化水銀の生成反応を調節できるから、脱硫装置に導入される酸性排ガスの酸化水銀濃度を制御でき、脱硫装置の吸収液である海水に吸収される酸化水銀を少なくして、放流する海水中の水銀濃度を許容値以下にできる。そのため、放流海水の水銀を除去する排水処理を行う必要がない。なお、脱硫装置入口側の酸化水銀濃度の設定値は、放流海水中の水銀濃度の許容値に応じて適宜選択する。 According to this, since the production reaction of mercury oxide can be adjusted by the temperature at the inlet side of the denitration device, the concentration of mercury oxide in the acidic exhaust gas introduced into the desulfurization device can be controlled and absorbed by seawater that is the absorption liquid of the desulfurization device. By reducing mercury oxide, the mercury concentration in the released seawater can be kept below the allowable value. Therefore, it is not necessary to perform wastewater treatment to remove mercury from the discharged seawater. The set value of the mercury oxide concentration at the desulfurizer inlet side is appropriately selected according to the allowable value of the mercury concentration in the discharged seawater.

　なお、脱硝装置入口側の酸性排ガス温度を、脱硫装置から排出される放流海水中の水銀濃度が設定値以下になるような温度に設定することができる。すなわち、放流海水中の水銀濃度が許容値（規準値）以下になるように、脱硫装置から排出又は脱硫装置に循環される吸収液である海水中の水銀濃度の許容値を設定し、吸収液である海水中の水銀濃度を検出して許容値を満たすように、脱硝装置入口側の酸性排ガス温度を設定する。 The acidic exhaust gas temperature at the inlet side of the denitration device can be set to a temperature at which the mercury concentration in the discharged seawater discharged from the desulfurization device is lower than the set value. That is, an allowable value of mercury concentration in seawater, which is an absorbing liquid discharged from the desulfurization apparatus or circulated to the desulfurization apparatus, is set so that the mercury concentration in the discharged seawater is less than the allowable value (standard value). The acidic exhaust gas temperature at the inlet side of the denitration device is set so that the mercury concentration in the seawater is detected and the allowable value is satisfied.

　また、脱硫装置の後流側に酸性排ガス中の水銀を吸着除去する水銀吸着装置を設けることが好ましい。これによれば、排ガス処理装置から放出される排ガス中の水銀濃度を低減できる。 Further, it is preferable to provide a mercury adsorption device for adsorbing and removing mercury in the acidic exhaust gas on the downstream side of the desulfurization device. According to this, the mercury concentration in the exhaust gas discharged from the exhaust gas treatment device can be reduced.

　なお、脱硝装置入口側の酸性排ガス温度は、放流海水中の水銀濃度の許容値に応じて適宜設定でき、例えば、１００％負荷時において４００℃以上になるように設定できる。すなわち、脱硝装置における酸化水銀の生成反応は、高温なると抑制されるから、脱硝装置入口側の酸性排ガス温度を高温にすることが好ましい。この場合において、脱硝装置入口側の酸性排ガス温度を過度に高くすると、脱硝率の低下や、触媒等の耐熱温度を超えるおそれがある。そのため、脱硝装置入口側の酸性排ガス温度は、例えば、４５０℃以下にすることが好ましい。 In addition, the acidic exhaust gas temperature at the inlet side of the denitration apparatus can be appropriately set according to the allowable value of the mercury concentration in the discharged seawater, and can be set to be 400 ° C. or higher at 100% load, for example. That is, since the generation reaction of mercury oxide in the denitration apparatus is suppressed at a high temperature, it is preferable to increase the temperature of the acidic exhaust gas on the denitration apparatus inlet side. In this case, if the acidic exhaust gas temperature at the inlet side of the denitration device is excessively increased, the denitration rate may be lowered or the heat resistance temperature of the catalyst or the like may be exceeded. Therefore, it is preferable that the acidic exhaust gas temperature at the inlet side of the denitration apparatus is, for example, 450 ° C. or less.

　また、本発明の発明者らは、脱硝装置入口側の酸性排ガス温度を４００℃以上に設定し、かつ、脱硝装置の触媒をタングステンを添加したチタンにより形成することで、脱硝装置における酸化水銀の生成反応を抑制できることを知見した。特に、チタン／タングステン＝６０／１～５０／４０の割合の触媒を用いることで、脱硝装置における酸化水銀の生成反応を一層抑制できる。 In addition, the inventors of the present invention set the acidic exhaust gas temperature on the denitration apparatus inlet side to 400 ° C. or higher, and the catalyst of the denitration apparatus is formed of titanium added with tungsten, so that mercury oxide in the denitration apparatus is formed. It was found that the production reaction can be suppressed. In particular, by using a catalyst having a ratio of titanium / tungsten = 60/1 to 50/40, the generation reaction of mercury oxide in the denitration apparatus can be further suppressed.

　また、脱硝装置における酸化水銀の生成反応は、酸性排ガス中の塩素濃度が高いと促進されるから、石炭を水洗処理して石炭に含まれる塩素分を減らした後に燃焼することが好ましい。これによれば、脱硝装置に導入される酸性排ガス中の塩素濃度を低減でるので、酸化水銀の生成反応を抑制できる。 Also, since the production reaction of mercury oxide in the denitration apparatus is promoted when the chlorine concentration in the acidic exhaust gas is high, it is preferable to burn the coal after washing it with water to reduce the chlorine content in the coal. According to this, since the chlorine concentration in the acidic exhaust gas introduced into the denitration apparatus can be reduced, the generation reaction of mercury oxide can be suppressed.

　本発明によれば、脱硫装置の吸収液として海水を用い、かつ、格別な排水処理を設けることなく、放流海水中の水銀濃度を許容値以下に抑えることができる。 According to the present invention, the concentration of mercury in the discharged seawater can be suppressed to an allowable value or less without using seawater as the absorption liquid of the desulfurization apparatus and providing a special waste water treatment.

本発明の一実施形態の排ガス処理装置のブロック図である。It is a block diagram of the exhaust gas processing apparatus of one embodiment of the present invention.

（実施形態）
　以下、本発明を実施の形態に基づいて説明する。図１に示すように、本実施形態の排ガス処理装置１は、例えば、石炭を燃焼するボイラ３に接続され、ボイラ３から排出された排ガス、例えば、窒素酸化物、硫黄酸化物等の酸性成分及び水銀を含む排ガスを清浄処理するようになっている。 (Embodiment)
Hereinafter, the present invention will be described based on embodiments. As shown in FIG. 1, the exhaust gas treatment apparatus 1 of the present embodiment is connected to, for example, a boiler 3 that burns coal, and exhaust gas discharged from the boiler 3, for example, acidic components such as nitrogen oxides and sulfur oxides In addition, exhaust gas containing mercury and mercury is cleaned.

　排ガス処理装置１には、例えば、選択的接触還元法により排ガスを脱硝する脱硝装置７が設けられている。脱硝装置７は、排ガスに還元剤５、例えば、アンモニアを添加して触媒存在下で排ガス中の窒素酸化物を還元するようになっている。脱硝装置７の出口側には、例えば、ボイラ３の燃焼用空気を排ガスで加熱する空気予熱器９が設けられている。空気予熱器９の出口側には、排ガス中の飛灰等の粉粒体を捕集して排ガスから除去する集塵装置１１が設けられている。集塵装置１１の出口側には、排ガス中の硫黄酸化物を海水に吸収させて除去する湿式の脱硫装置１３が設けられている。 The exhaust gas treatment device 1 is provided with a denitration device 7 for denitrating exhaust gas by a selective catalytic reduction method, for example. The denitration device 7 is configured to add a reducing agent 5 such as ammonia to the exhaust gas to reduce nitrogen oxides in the exhaust gas in the presence of a catalyst. On the outlet side of the denitration device 7, for example, an air preheater 9 that heats combustion air of the boiler 3 with exhaust gas is provided. On the outlet side of the air preheater 9, there is provided a dust collector 11 that collects particulate matter such as fly ash in the exhaust gas and removes it from the exhaust gas. On the outlet side of the dust collector 11, there is provided a wet desulfurizer 13 that absorbs and removes sulfur oxides in the exhaust gas by seawater.

　脱硫装置１３は、例えば、ポンプ等により汲み上げた海水を排ガスに噴霧するようになっている。これにより、排ガス中の硫黄酸化物を海水に吸収させて除去できる。脱硫装置１３には、例えば、図示していない浄化装置が設けられ、海水に吸収させた硫黄酸化物を除去し、硫黄酸化物を除去した海水を海に放流するようになっている。なお、脱硫装置１３は、吸収液である海水を循環使用した後に放流する循環型、又は海水を循環使用せず、一度使用した海水を放流するワンスルー型等、適宜選択できる。 The desulfurization device 13 is configured to spray seawater pumped by a pump or the like onto the exhaust gas, for example. Thereby, the sulfur oxide in exhaust gas can be absorbed and removed by seawater. For example, the desulfurization device 13 is provided with a purification device (not shown), which removes sulfur oxides absorbed in seawater and discharges the seawater from which sulfur oxides have been removed to the sea. In addition, the desulfurization apparatus 13 can be selected as appropriate, such as a circulation type that discharges seawater that is an absorption liquid after circulation, or a one-through type that discharges seawater that has been used once without circulation.

　脱硫装置１３の出口側には、排ガス中の水銀を吸着除去する水銀吸着装置１５が設けられている。水銀吸着装置１５は、例えば、水銀を吸着可能な活性炭が充填される吸着塔１７と、活性炭に吸着した水銀を除去して活性炭を再生する再生塔１９が設けられている。これにより、図１の点線で示すように活性炭を循環使用して排ガスから水銀を除去できるようになっている。水銀吸着装置１５の出口側には、煙突が設けられ、浄化された排ガスを大気中に放出するようになっている。 A mercury adsorbing device 15 for adsorbing and removing mercury in the exhaust gas is provided on the outlet side of the desulfurization device 13. The mercury adsorption device 15 is provided with, for example, an adsorption tower 17 filled with activated carbon capable of adsorbing mercury and a regeneration tower 19 that removes the mercury adsorbed on the activated carbon and regenerates the activated carbon. As a result, as shown by the dotted line in FIG. 1, mercury can be removed from the exhaust gas by circulating and using activated carbon. A chimney is provided on the outlet side of the mercury adsorption device 15 so as to discharge the purified exhaust gas into the atmosphere.

　次に、本実施形態の排ガス処理装置の特徴構成を説明する。脱硝装置７入口側の排ガス温度は、脱硫装置１３入口側の酸化水銀濃度の検出値又は設計値が設定値以下になるような温度に設定される。脱硝装置７入口側の排ガス温度は、例えば、ボイラ３内の節炭器等の伝熱面積又はボイラ３内を通流する給水量を適宜調整することで設定できる。これにより、脱硝装置７の入口側排ガス温度を、脱硝装置７における酸化水銀の生成反応を抑える温度、例えば、４００℃以上に設定する。また、酸化水銀濃度の設定値は、脱硫装置１３の放流海水中の水銀濃度が許容限度の規準に応じて適宜設定する。すなわち、放流海水中の水銀濃度は、脱硫装置１３入口側の酸化水銀濃度に相関し、脱硫装置１３入口側の酸化水銀濃度は、脱硝装置７入口側の排ガス温度により調整できるので、脱硫装置１３入口側の酸化水銀濃度が設定値以下になるように、脱硝装置７入口側の排ガス温度を設定する。 Next, the characteristic configuration of the exhaust gas treatment apparatus of the present embodiment will be described. The exhaust gas temperature at the inlet side of the denitration device 7 is set to a temperature at which the detected value or design value of the mercury oxide concentration at the inlet side of the desulfurization device 13 is equal to or less than the set value. The exhaust gas temperature at the inlet side of the denitration device 7 can be set by appropriately adjusting, for example, the heat transfer area of the economizer in the boiler 3 or the amount of water supplied through the boiler 3. Thereby, the exhaust gas temperature at the inlet side of the denitration device 7 is set to a temperature at which the mercury oxide production reaction in the denitration device 7 is suppressed, for example, 400 ° C. or more. Further, the set value of the mercury oxide concentration is appropriately set according to the standard of the allowable limit of the mercury concentration in the discharged seawater of the desulfurization apparatus 13. That is, the mercury concentration in the effluent seawater correlates with the mercury oxide concentration on the inlet side of the desulfurization device 13, and the mercury oxide concentration on the inlet side of the desulfurization device 13 can be adjusted by the exhaust gas temperature on the inlet side of the denitration device 7. The exhaust gas temperature at the inlet side of the denitration device 7 is set so that the mercury oxide concentration at the inlet side is not more than the set value.

　このように構成される排ガス処理装置１の動作を説明する。ボイラ３から排出された排ガス中の窒素酸化物は、脱硝装置７により脱硝される。脱硝された排ガスは、空気予熱器９に導入され、ボイラ３の燃焼用空気との熱交換により減温される。減温された排ガス中の灰分や未燃炭素等の粉粒体は、集塵装置１１により排ガスから除去される。集塵装置１１から排出された排ガスには、脱硫装置１３により海水が噴霧され、排ガス中の硫黄酸化物を海水に吸収させ脱硫される。硫黄酸化物を吸収した海水は、例えば、硫黄酸化物を除去する浄化処理がされた後、海に放流される。 The operation of the exhaust gas treatment apparatus 1 configured as described above will be described. Nitrogen oxides in the exhaust gas discharged from the boiler 3 are denitrated by the denitration device 7. The denitrated exhaust gas is introduced into the air preheater 9 and reduced in temperature by heat exchange with the combustion air of the boiler 3. The particulate matter such as ash and unburned carbon in the exhaust gas whose temperature has been reduced is removed from the exhaust gas by the dust collector 11. The exhaust gas discharged from the dust collector 11 is sprayed with seawater by the desulfurization device 13, and the sulfur oxide in the exhaust gas is absorbed into the seawater and desulfurized. Seawater that has absorbed sulfur oxides, for example, is discharged into the sea after being purified to remove sulfur oxides.

　脱硫装置１３から排出された排ガスは、水銀吸着装置１５の吸着塔１７に導入される。これにより、排ガス中の金属水銀が活性炭等の吸着材に吸着されて排ガスから除去される。水銀が除去された排ガスは、例えば、再加熱器により加熱された後、煙突２１から大気中に放出される。 The exhaust gas discharged from the desulfurization device 13 is introduced into the adsorption tower 17 of the mercury adsorption device 15. Thereby, the metallic mercury in the exhaust gas is adsorbed by the adsorbent such as activated carbon and removed from the exhaust gas. The exhaust gas from which mercury has been removed is, for example, heated by a reheater and then released from the chimney 21 into the atmosphere.

　次に、本実施形態の特徴作用を説明する。一般に、脱硝装置７の触媒存在下においては、以下の（式１）に示すいわゆる脱硝反応と、（式２）に示す二酸化硫黄の酸化により三酸化硫黄が生成する反応と、（式３）に示す金属水銀の酸化により酸化水銀が生成する反応が生じる。
　４ＮＯ　+　４ＮＨ３　+　Ｏ２　→　４Ｎ２　+　６Ｈ２Ｏ・・・（式１）
　２ＳＯ２　+　 Ｏ２　→　２ＳＯ３・・・（式２）
　２Ｈｇ　+　４ＨＣｌ　+　Ｏ２　→　２ＨｇＣｌ２　+　２Ｈ２Ｏ・・・（式３）
　この（式３）の反応により、水に溶けにくい金属水銀（Ｈｇ）が水に溶けやすい酸化水銀（ＨｇＣｌ２）に変換される。このため、脱硝装置７の後流に配置した脱硫装置１３の吸収液である海水に酸化水銀が溶け込み、脱硫装置１３の放流海水に水銀が混じることになる。そこで、脱硫装置１３の入口側の酸化水銀濃度が設定値以下になるように、脱硝装置７入口側の排ガス温度を、酸化水銀の生成反応を抑える温度に設定する。これより、脱硫装置１３の海水に吸収される酸化水銀を少なくでき、放流する海水中の水銀濃度を許容値以下にできる。その結果、海水から水銀を除去するための処理設備を設ける必要がない。 Next, the characteristic operation of this embodiment will be described. In general, in the presence of a catalyst of the denitration device 7, a so-called denitration reaction shown in the following (Formula 1), a reaction in which sulfur trioxide is generated by oxidation of sulfur dioxide shown in (Formula 2), and (Formula 3) Oxidation of the metal mercury shown causes a reaction to produce mercury oxide.
4NO + 4NH 3 + O 2 → 4N 2 + 6H 2 O (Formula 1)
2SO 2 + O 2 → 2SO 3 (Formula 2)
2Hg + 4HCl + O 2 → 2HgCl 2 + 2H 2 O (formula 3)
By this reaction of (Formula 3), metallic mercury (Hg) that is hardly soluble in water is converted to mercury oxide (HgCl 2 ) that is easily soluble in water. For this reason, mercury oxide is dissolved in seawater that is an absorption liquid of the desulfurization device 13 disposed downstream of the denitration device 7, and mercury is mixed in the discharged seawater of the desulfurization device 13. Therefore, the exhaust gas temperature on the inlet side of the denitration device 7 is set to a temperature that suppresses the generation reaction of mercury oxide so that the mercury oxide concentration on the inlet side of the desulfurization device 13 is not more than the set value. Thereby, the mercury oxide absorbed in the seawater of the desulfurization apparatus 13 can be reduced, and the mercury concentration in the seawater to be discharged can be reduced to an allowable value or less. As a result, there is no need to provide a treatment facility for removing mercury from seawater.

　また、脱硫装置１３の吸収液である海水中の酸化水銀濃度を検出し、この検出値が設定値以下になるように、脱硝装置７入口側の排ガス温度を、酸化水銀の生成反応が抑制される温度に設定する。すなわち、脱硫装置１３から排出され又は脱硫装置１３に循環される吸収液である海水中の水銀濃度の許容値を設定し、吸収液である海水中の水銀濃度が許容値以下になるように、脱硝装置７入口側の排ガス温度を設定することができる。これにより、脱硫装置１３から排出される放流海水中の水銀濃度を設定値以下にできるから、水銀を除去するための処理設備を設ける必要がない。 Further, the mercury oxide concentration in the seawater that is the absorption liquid of the desulfurization device 13 is detected, and the exhaust gas temperature on the inlet side of the denitration device 7 is reduced so that the generation reaction of mercury oxide is suppressed so that the detected value is lower than the set value. Set to the desired temperature. That is, an allowable value of mercury concentration in seawater that is an absorption liquid discharged from the desulfurization apparatus 13 or circulated to the desulfurization apparatus 13 is set, and the mercury concentration in seawater as the absorption liquid is less than the allowable value. The exhaust gas temperature on the inlet side of the denitration device 7 can be set. Thereby, since the mercury concentration in the discharged seawater discharged from the desulfurization apparatus 13 can be set to a set value or less, it is not necessary to provide a treatment facility for removing mercury.

　また、酸化水銀の生成反応は、後述する実施例によれば、高温雰囲気で抑制されるので、脱硝装置７入口側の排ガス温度を、例えば、１００％負荷時において４００℃以上に設定することが好ましい。なお、脱硝装置７入口側の排ガス温度を過度に高くすると、脱硝率の低下や、触媒等の耐熱温度を超えるおそれがあるから、脱硝装置７入口側の排ガス温度は、例えば、４５０℃以下にすることが好ましい。 Further, since the generation reaction of mercury oxide is suppressed in a high-temperature atmosphere according to an example described later, the exhaust gas temperature on the inlet side of the denitration device 7 can be set to 400 ° C. or higher at 100% load, for example. preferable. If the exhaust gas temperature at the inlet side of the denitration device 7 is excessively high, there is a risk that the NOx removal rate will decrease and the heat resistance temperature of the catalyst or the like may be exceeded. It is preferable to do.

　ここで、脱硝装置７入口側の排ガス温度と酸化水銀の生成率（水銀の酸化率）の関係を実施例に基づいて説明する。実施例１は、酸化チタンを触媒とした脱硝装置７において、脱硝率を９０％に設定し、脱硝装置７入口側の排ガス温度を４００℃に設定した例である。比較例１は、実施例１の条件において、脱硝装置７入口側の排ガス温度を３５０℃に設定した例である。比較例２は、脱硝装置７入口側の排ガス温度を３８０℃に設定した例である。これらの実施例１及び比較例１、２において、酸化水銀の生成率を実測した結果を表１に示す。なお、その他の測定条件は、表１に示すとおりである。 Here, the relationship between the exhaust gas temperature on the inlet side of the denitration device 7 and the generation rate of mercury oxide (mercury oxidation rate) will be described based on examples. Example 1 is an example in which the denitration rate is set to 90% and the exhaust gas temperature at the inlet side of the denitration device 7 is set to 400 ° C. in the denitration device 7 using titanium oxide as a catalyst. Comparative Example 1 is an example in which the exhaust gas temperature on the inlet side of the denitration device 7 is set to 350 ° C. under the conditions of Example 1. Comparative Example 2 is an example in which the exhaust gas temperature at the inlet side of the denitration device 7 is set to 380 ° C. Table 1 shows the results of actual measurement of the mercury oxide production rate in Example 1 and Comparative Examples 1 and 2. Other measurement conditions are as shown in Table 1.

Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001

　これによれば、脱硝装置７入口側の排ガス温度を４００℃に設定した実施例１は、３５０℃に設定した比較例１よりも約８２％酸化水銀の生成を抑制でき、３８０℃に設定した比較例２よりも約６７％酸化水銀の生成を抑制できた。すなわち、酸化水銀の生成反応は温度に相関し、温度が高くなると酸化水銀の生成反応を抑制できることがわかる。したがって、脱硝装置７入口側の排ガス温度により酸化水銀の生成反応を調節でき、脱硫装置１３に導入される排ガスの酸化水銀濃度を制御できるから、脱硫装置１３の海水に吸収される酸化水銀を少なくでき、放流する海水中の水銀濃度を許容値以下にできる。 According to this, Example 1 in which the exhaust gas temperature at the inlet side of the denitration device 7 was set to 400 ° C. can suppress the generation of about 82% mercury oxide compared with Comparative Example 1 set to 350 ° C., and was set to 380 ° C. Compared to Comparative Example 2, it was possible to suppress the generation of about 67% mercury oxide. That is, it can be seen that the mercury oxide production reaction correlates with temperature, and that the mercury oxide production reaction can be suppressed as the temperature increases. Therefore, the production reaction of mercury oxide can be adjusted by the exhaust gas temperature on the inlet side of the denitration device 7 and the concentration of mercury oxide in the exhaust gas introduced into the desulfurization device 13 can be controlled, so that the mercury oxide absorbed in the seawater of the desulfurization device 13 is reduced. The mercury concentration in the released seawater can be made below the allowable value.

　次に、脱硝装置７の入口側排ガス温度を４００℃に設定した実施例１の触媒に、酸化チタンに助触媒としてタングステンを添加した触媒を用いた例を実施例２とした。また、実施例２の石炭を水洗処理した後に燃焼した例を実施例３とした。また、実施例３の触媒量を減らして脱硝率を８０％に設定した例を実施例４とした。実施例２～４の酸化水銀の生成率（水銀の酸化率）を実測した結果を、表２に示す。その他の測定条件は、実施例１と同一である。 Next, Example 2 in which a catalyst obtained by adding tungsten as a co-catalyst to titanium oxide was used as Example 2 for the catalyst of Example 1 in which the inlet side exhaust gas temperature of the denitration apparatus 7 was set to 400 ° C. Moreover, the example which burned after performing the water washing process of the coal of Example 2 was made into Example 3. FIG. An example in which the amount of catalyst in Example 3 was reduced and the denitration rate was set to 80% was taken as Example 4. Table 2 shows the results of actual measurement of the mercury oxide production rate (mercury oxidation rate) in Examples 2 to 4. Other measurement conditions are the same as in Example 1.

Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002

　実施例２～４によれば、実施例１と比較して、さらに、酸化水銀の生成反応を抑制できることがわかる。つまり、脱硝装置７入口側の排ガス温度を４００℃に設定し、かつ、タングステン（Ｗ）を添加した酸化チタンにより触媒を形成することで、酸化水銀の生成反応を一層抑制できる。なお、助触媒であるタングステンの割合は、要求される脱硝率や排ガス温度、排ガス量等に応じて適宜選択できる。しかし、添加するタングステン量が少なすぎると、酸化水銀の生成を抑制する効果が低くなり、また、触媒劣化速度が速くなる。一方、タングステンは高価であるから、過剰なタングステンの使用は触媒価格を著しく高くする。したがって、タングステンの添加量は、Ｔｉ／Ｗ＝６０／１～５０／４０の範囲にすることが好ましい。 According to Examples 2 to 4, it can be seen that the production reaction of mercury oxide can be further suppressed as compared with Example 1. That is, the exhaust gas temperature at the inlet side of the denitration device 7 is set to 400 ° C., and the catalyst is formed from titanium oxide to which tungsten (W) is added, whereby the generation reaction of mercury oxide can be further suppressed. The proportion of tungsten as the promoter can be selected as appropriate according to the required denitration rate, exhaust gas temperature, exhaust gas amount, and the like. However, if the amount of tungsten added is too small, the effect of suppressing the generation of mercury oxide is reduced, and the catalyst deterioration rate is increased. On the other hand, since tungsten is expensive, the use of excess tungsten significantly increases the catalyst price. Accordingly, the addition amount of tungsten is preferably in the range of Ti / W = 60/1 to 50/40.

　また、金属水銀と塩化水素が反応して酸化水銀が生成するから、実施例３に示すように、石炭を水洗処理して石炭に含まれる塩素分を少なくした後に燃焼することができる。これによれば、ボイラ３から排出される排ガス中の塩素分を少なくでき、酸化水銀の生成を抑制できる。また、求められる脱硝率が、例えば、実施例４に示すように８０％の場合は、脱硝装置７内に設置する触媒量を減らすことで、触媒による酸化水銀の生成反応を抑制できる。したがって、実施例２～４によっても、脱硫装置１３における酸化水銀の生成反応を抑制でき、脱硫装置１３に導入される排ガス中の酸化水銀濃度を少なくできるから、脱硫装置１３の海水に吸収される酸化水銀を少なくでき、放流する海水中の水銀濃度を許容値以下にできる。 Also, since mercury mercury reacts with mercury metal to produce mercury oxide, as shown in Example 3, it can be burned after the coal is washed with water to reduce the chlorine content in the coal. According to this, the chlorine content in the exhaust gas discharged from the boiler 3 can be reduced, and the production of mercury oxide can be suppressed. Further, when the required denitration rate is, for example, 80% as shown in Example 4, the production reaction of mercury oxide by the catalyst can be suppressed by reducing the amount of catalyst installed in the denitration device 7. Therefore, also in Examples 2 to 4, the generation reaction of mercury oxide in the desulfurization apparatus 13 can be suppressed and the concentration of mercury oxide in the exhaust gas introduced into the desulfurization apparatus 13 can be reduced, so that it is absorbed by the seawater of the desulfurization apparatus 13. Mercury oxide can be reduced, and the mercury concentration in the discharged seawater can be reduced below the allowable value.

　１　排ガス処理装置
　５　還元剤
　７　脱硝装置
　１３　脱硫装置
　１５　水銀吸着装置
 
  1 exhaust gas treatment device 5 reducing agent 7 denitration device 13 desulfurization device 15 mercury adsorption device

Claims (10)

　石炭の燃焼により発生した水銀を含む酸性排ガスに、還元剤を添加して触媒存在下で酸性排ガス中の窒素酸化物を還元する脱硝装置と、該脱硝装置から排出される酸性排ガス中の硫黄酸化物を海水に吸収させて除去する脱硫装置とを備え、
　前記脱硝装置の入口側の酸性排ガス温度は、前記脱硝装置における酸化水銀の生成反応を抑えて前記脱硫装置の入口側の酸化水銀濃度が設定値以下になるような温度に設定されてなる排ガス処理装置。 A denitration device that reduces nitrogen oxides in acidic exhaust gas in the presence of a catalyst by adding a reducing agent to acidic exhaust gas containing mercury generated by coal combustion, and sulfur oxidation in acidic exhaust gas discharged from the denitration device Equipped with desulfurization equipment that absorbs and removes objects in seawater,
The exhaust gas treatment in which the acidic exhaust gas temperature on the inlet side of the denitration apparatus is set to such a temperature that the mercury oxide concentration on the inlet side of the desulfurization apparatus is lower than a set value by suppressing the generation reaction of mercury oxide in the denitration apparatus. apparatus. 　請求項１に記載の排ガス処理装置において、
　前記脱硝装置を通流させる酸性排ガスの温度は、４００℃以上に設定されることを特徴とする排ガス処理装置。 The exhaust gas treatment apparatus according to claim 1,
The exhaust gas treatment apparatus according to claim 1, wherein the temperature of the acidic exhaust gas flowing through the denitration apparatus is set to 400 ° C or higher. 　請求項1に記載の排ガス処理装置において、
　前記脱硫装置から排出される酸性排ガス中の水銀を吸着除去する水銀吸着装置が設けられることを特徴とする排ガス処理装置。 In the exhaust gas treatment apparatus according to claim 1,
An exhaust gas treatment apparatus, comprising a mercury adsorption device for adsorbing and removing mercury in acidic exhaust gas discharged from the desulfurization device. 　請求項１に記載の排ガス処理装置において、
　前記脱硝装置の触媒は、タングステンを添加したチタンにより形成されることを特徴とする排ガス処理装置。 The exhaust gas treatment apparatus according to claim 1,
The exhaust gas treatment apparatus, wherein the catalyst of the denitration apparatus is formed of titanium added with tungsten. 　請求項１に記載の排ガス処理装置において、
　前記石炭は、水洗処理された後に燃焼されることを特徴とする排ガス処理装置。 The exhaust gas treatment apparatus according to claim 1,
The exhaust gas treatment apparatus, wherein the coal is burned after being washed with water. 　請求項１に記載の排ガス処理装置において、
　前記脱硫装置の入口側の酸化水銀濃度に代えて、前記脱硫装置から排出され又は前記脱硫装置に循環される吸収液である海水中の酸化水銀濃度が設定値以下になるような温度に、前記脱硝装置の入口側の酸性排ガス温度は設定されてなる排ガス処理装置。 The exhaust gas treatment apparatus according to claim 1,
Instead of the mercury oxide concentration on the inlet side of the desulfurization device, the temperature is such that the mercury oxide concentration in seawater, which is an absorption liquid discharged from the desulfurization device or circulated to the desulfurization device, becomes a set value or less. An exhaust gas treatment device in which the acidic exhaust gas temperature on the inlet side of the denitration device is set. 　請求項６に記載の排ガス処理装置において、
　前記脱硝装置を通流させる酸性排ガスの温度は、４００℃以上に設定されることを特徴とする排ガス処理装置。 The exhaust gas treatment apparatus according to claim 6,
The exhaust gas treatment apparatus according to claim 1, wherein the temperature of the acidic exhaust gas flowing through the denitration apparatus is set to 400 ° C or higher. 　請求項６に記載の排ガス処理装置において、
　前記脱硫装置から排出される酸性排ガス中の水銀を吸着除去する水銀吸着装置が設けられることを特徴とする排ガス処理装置。 The exhaust gas treatment apparatus according to claim 6,
An exhaust gas treatment apparatus, comprising a mercury adsorption device for adsorbing and removing mercury in acidic exhaust gas discharged from the desulfurization device. 　請求項６に記載の排ガス処理装置において、
　前記脱硝装置の触媒は、タングステンを添加したチタンにより形成されることを特徴とする排ガス処理装置。 The exhaust gas treatment apparatus according to claim 6,
The exhaust gas treatment apparatus, wherein the catalyst of the denitration apparatus is formed of titanium added with tungsten. 　請求項６に記載の排ガス処理装置において、
　前記石炭は、水洗処理された後に燃焼されることを特徴とする排ガス処理装置。 The exhaust gas treatment apparatus according to claim 6,
The exhaust gas treatment apparatus, wherein the coal is burned after being washed with water.
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