US20130092062A1 - Combustion system - Google Patents

Combustion system Download PDF

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Publication number
US20130092062A1
US20130092062A1 US13/703,737 US201113703737A US2013092062A1 US 20130092062 A1 US20130092062 A1 US 20130092062A1 US 201113703737 A US201113703737 A US 201113703737A US 2013092062 A1 US2013092062 A1 US 2013092062A1
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United States
Prior art keywords
unit
exhaust gas
combustion
removal device
oxygen
Prior art date
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Abandoned
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US13/703,737
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English (en)
Inventor
Masahiko Matsuda
Hiroshi Suganuma
Takeshi Aruga
Koutaro Fujimura
Takuichiro Daimaru
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Mitsubishi Power Ltd
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Mitsubishi Heavy Industries Ltd
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Publication date
Application filed by Mitsubishi Heavy Industries Ltd filed Critical Mitsubishi Heavy Industries Ltd
Assigned to MITSUBISHI HEAVY INDUSTRIES, LTD. reassignment MITSUBISHI HEAVY INDUSTRIES, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ARUGA, TAKESHI, DAIMARU, TAKUICHIRO, FUJIMURA, KOUTARO, MATSUDA, MASAHIKO, SUGANUMA, HIROSHI
Publication of US20130092062A1 publication Critical patent/US20130092062A1/en
Assigned to MITSUBISHI HITACHI POWER SYSTEMS, LTD. reassignment MITSUBISHI HITACHI POWER SYSTEMS, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MITSUBISHI HEAVY INDUSTRIES, LTD.
Abandoned legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J11/00—Devices for conducting smoke or fumes, e.g. flues 
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C9/00—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber
    • F23C9/08—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber for reducing temperature in combustion chamber, e.g. for protecting walls of combustion chamber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C99/00—Subject-matter not provided for in other groups of this subclass
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L7/00—Supplying non-combustible liquids or gases, other than air, to the fire, e.g. oxygen, steam
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L7/00—Supplying non-combustible liquids or gases, other than air, to the fire, e.g. oxygen, steam
    • F23L7/007—Supplying oxygen or oxygen-enriched air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C2202/00—Fluegas recirculation
    • F23C2202/10—Premixing fluegas with fuel and combustion air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L2900/00—Special arrangements for supplying or treating air or oxidant for combustion; Injecting inert gas, water or steam into the combustion chamber
    • F23L2900/07001—Injecting synthetic air, i.e. a combustion supporting mixture made of pure oxygen and an inert gas, e.g. nitrogen or recycled fumes
    • 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
    • Y02E20/32—Direct CO2 mitigation
    • 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
    • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Definitions

  • the present invention relates to a combustion system, and more particularly relates to removal of nitrogen oxide in exhaust gas.
  • Coal is generally used as fuel in thermal power plants and the like since the resource volume of coal is abundant. However, coal is high in carbon contents in fuel compared with oil and gas. When coal is combusted by an air combustion boiler system, the emission amount of carbon dioxide is increased.
  • the oxygen combustion boiler system 101 includes a coal pulverizer 103 for pulverizing coal, an oxygen combustion boiler 102 for combusting the coal pulverized by the coal pulverizer 103 and discharging exhaust gas, a denitration device 104 for removing nitrogen oxide in the exhaust gas discharged from the oxygen combustion boiler 102 , a dust removal device 105 for removing dust and the like in the exhaust gas, a desulfurization device 106 for removing sulfur oxide in the exhaust gas, and a gas cooler 107 for cooling the exhaust gas to remove moisture in the exhaust gas.
  • Carrier gas is introduced into the coal pulverizer 103 for drying the pulverized coal and conveying the pulverized coal from the coal pulverizer 103 to the oxygen combustion boiler 102 .
  • the carrier gas exhaust gas (hereinafter referred to as “primary recirculation gas”) discharged from the desulfurization device 106 and traveling through the gas cooler 107 is used.
  • the primary recirculation gas is heated by an air heater 108 provided between the denitration device 104 and the dust removal device 105 for drying the coal.
  • the air heater 108 performs heat exchange between high-temperature exhaust gas discharged from the denitration device 104 and low-temperature exhaust gas which has passed the gas cooler 107 , and thereby heats the primary recirculation gas introduced to the coal pulverizer 103 .
  • the oxygen supplied to the burner unit 102 a is adjusted so that the amount of oxygen introduced from the combustion oxygen supply system is not larger than 1.0 times the theoretical combustion oxygen amount of the coal supplied from the coal pulverizer 103 .
  • a remaining amount of the oxygen introduced from the combustion oxygen supply system is supplied to the AA port 102 b . Accordingly, a zone between the burner unit 102 a and the AA port 102 b in the oxygen combustion boiler 102 is in an oxygen-poor state.
  • the zone between the burner unit 102 a and the AA port 102 b is made to have a reducing atmosphere.
  • the fuel charged into the oxygen combustion boiler 102 through the burner unit 102 a combusts and generates exhaust gas.
  • Nitrogen oxide (NOx) contained in the generated exhaust gas is partially reduced when passing the reducing atmosphere present between the burner unit 102 a and the AA port 102 b . This makes it possible to decrease nitrogen oxide within the oxygen combustion boiler 102 .
  • Patent Literature 2 and Patent Literature 3 disclose oxygen combustion boilers for receiving part of exhaust gas introduced as secondary recirculation gas which has passed a denitration device, an air heater, a dust removal device, and a desulfurization device.
  • the concentration of nitrogen oxide treated by the denitration device 104 was high, the consumption of ammonia sprayed to the exhaust gas passing the denitration device 104 increased.
  • a combustion system of the present invention employs the following solutions to solve the foregoing problems.
  • a combustion system includes: a combustion furnace having a burner unit for supplying fuel and combustion oxygen to an inside of the furnace, a reduction zone formed on a downstream side of the burner unit for combusting the fuel, and a combustion oxygen supply port for supplying combustion oxygen so that unburned fuel which has passed the reduction zone completely combusts; and a smoke removal device for removing smoke in the exhaust gas discharged from the combustion furnace, wherein part of exhaust gas diverging from between the combustion furnace and the smoke removal device is introduced to the burner unit, while part of exhaust gas diverging from a downstream side of the smoke removal device is introduced to the combustion oxygen supply port.
  • part of exhaust gas diverging from the downstream side of the smoke removal device is the exhaust gas having the concentration of nitrogen oxide, which is smoke, decreased by the smoke removal device.
  • the exhaust gas having a decreased nitrogen oxide concentration is introduced to the combustion oxygen supply port and is used for promoting complete combustion of the unburned fuel contained in the exhaust gas which has partially been reduced by passing the reducing atmosphere inside the combustion furnace. Therefore, the exhaust gas can be discharged out of the combustion furnace while the concentration of nitrogen oxide contained therein is maintained low.
  • the exhaust gas having a decreased nitrogen oxide concentration is recirculated to the combustion furnace and the smoke removal device, so that increase in the concentration of nitrogen oxide in an outlet of the combustion furnace can be suppressed.
  • the smoke removal device includes: a denitration unit for removing nitrogen oxide in the exhaust gas discharged from the combustion furnace; a heat exchange unit for conducting heat exchange between exhaust gas which has passed the denitration unit and exhaust gas which is introduced to the combustion oxygen supply port; a dust removal unit for removing dust in exhaust gas which has passed the heat exchange unit; a desulfurization unit for removing sulfur oxide in exhaust gas which has passed the dust removal unit; and a cooling unit for cooling exhaust gas which has passed the desulfurization unit, wherein part of exhaust gas diverging from between the desulfurization unit and the cooling unit is introduced to the combustion oxygen supply port.
  • part of the exhaust gas diverging from between the desulfurization unit and the cooling unit is introduced to the combustion oxygen supply port of the combustion furnace.
  • part of exhaust gas diverging from between the dust removal unit and the desulfurization unit is introduced to the combustion oxygen supply port.
  • part of the exhaust gas diverging from between the dust removal unit and the desulfurization unit is introduced to the combustion oxygen supply port. This makes it possible to decrease the flow rate of nitrogen oxide in the exhaust gas introduced to the denitration unit as well as to decrease the flow rate of the exhaust gas introduced to the desulfurization unit and the cooling unit. Therefore, it becomes possible to downsize the denitration unit and to reduce the capacity of the desulfurization unit and the cooling unit.
  • part of exhaust gas diverging from between the denitration unit and the dust removal unit is introduced to the combustion oxygen supply port.
  • part of the exhaust gas diverging from between the denitration unit and the dust removal unit is introduced to the combustion oxygen supply port.
  • This makes it possible to decrease the flow rate of nitrogen oxide in the exhaust gas introduced to the denitration unit as well as to decrease the flow rate of the exhaust gas introduced to the heat exchange unit, the dust removal unit, the desulfurization unit and the cooling unit. Therefore, it becomes possible to downsize the denitration unit and to reduce the capacity of the heat exchange unit, the dust removal unit, the desulfurization unit and the cooling unit.
  • the denitration unit includes: an ammonia supply unit for supplying ammonia into exhaust gas; and a catalyst unit for allowing exhaust gas supplied by the ammonia supply unit to pass therethrough.
  • the exhaust gas having a decreased flow rate of nitrogen oxide is introduced to the denitration unit. Therefore, the amount of ammonia to be supplied can be reduced as compared with the case where the exhaust gas whose flow rate of nitrogen oxide is not decreased.
  • part of exhaust gas diverging from between the combustion furnace and the smoke removal device is resupplied to the inside of the combustion furnace through the burner unit.
  • a zone under reducing atmosphere is formed between the burner unit of the combustion furnace and the combustion oxygen supply port. Consequently, the exhaust gas diverging from between the combustion furnace and the smoke removal device can be reduced in the zone under reducing atmosphere formed in the combustion furnace before being discharged. This makes it possible to decrease the flow rate of the exhaust gas introduced from the combustion furnace to the smoke removal device and to decrease the flow rate of smoke. Therefore, the capacity of the smoke removal device can be reduced.
  • part of exhaust gas diverging from the downstream side of the smoke removal device is the exhaust gas having the concentration of nitrogen oxide, which is smoke, decreased by the smoke removal device.
  • the exhaust gas having a decreased nitrogen oxide concentration is introduced to the combustion oxygen supply port and is used for promoting complete combustion of the unburned fuel contained in the exhaust gas which has partially been reduced by passing the reducing atmosphere inside the combustion furnace. Therefore, the exhaust gas can be discharged out of the combustion furnace while the concentration of nitrogen oxide contained therein is maintained low.
  • the exhaust gas having a decreased nitrogen oxide concentration is recirculated to the combustion furnace and the smoke removal device, so that increase in the concentration of nitrogen oxide in the outlet of the combustion furnace can be suppressed.
  • FIG. 1 is a schematic structure view of a combustion system according to a first embodiment of the present invention.
  • FIG. 2 is a schematic structure view of a combustion system according to a second embodiment of the present invention.
  • FIG. 3 is a schematic structure view of a combustion system according to a third embodiment of the present invention.
  • FIG. 4 is a schematic structure view of a combustion system according to a fourth embodiment of the present invention.
  • FIG. 5 is a schematic structure view of a conventional oxygen combustion boiler system.
  • FIG. 1 is a schematic structure view of a combustion system according to the first embodiment of the present invention.
  • the combustion system 1 includes a coal fired boiler (combustion furnace) 2 , a coal pulverizer 3 for pulverizing coal supplied to the coal fired boiler 2 , and a smoke removal device 9 .
  • the coal fired boiler 2 is an oxygen combustion boiler which can conduct denitration inside the furnace (not shown) by two-stage combustion.
  • the coal fired boiler 2 includes a furnace inside for combusting fuel, a burner unit 2 a , and an additional air port (hereinafter referred to as “AA unit”) 2 b .
  • AA unit additional air port
  • Coal as fuel supplied from the coal pulverizer 3 , oxygen (combustion oxygen) introduced from a combustion oxygen supply system 21 , and later-described secondary recirculation gas for burner unit 22 are introduced to the burner unit 2 a .
  • Remaining part of the oxygen introduced from the combustion oxygen supply system 21 to the burner unit 2 a and later-described secondary recirculation gas for AA unit 23 are introduced to the AA unit (combustion oxygen supply port) 2 b.
  • the coal pulverizer 3 is for pulverizing the coal, which is supplied to the coal fired boiler 2 , into fine powder of a size of several ⁇ m to hundreds of ⁇ m.
  • Part of exhaust gas (hereinafter referred to as “primary recirculation gas”) 24 discharged from the smoke removal device 9 is introduced to the coal pulverizer 3 as high-temperature carrier gas for drying the pulverized coal and conveying the pulverized coal from the coal pulverizer 3 to the coal fired boiler 2 .
  • the smoke removal device 9 includes a denitration device (denitration unit) 4 , a gas heater (heat exchange unit) 8 , a dust removal device (dust removal unit) 5 , a desulfurization device (desulfurization unit) 6 , and a gas cooler (cooling unit) 7 .
  • the denitration device 4 includes an ammonia supply unit (not shown) for spraying ammonia to the exhaust gas, and a catalyst unit (not shown) for allowing the exhaust gas having ammonia sprayed thereto to pass therethrough.
  • the denitration device 4 is for removing nitrogen oxide in the exhaust gas by spraying ammonia to the introduced exhaust gas and for having the exhaust gas pass the catalyst unit.
  • the gas heater 8 is for conducting heat exchange of the high-temperature exhaust gas, which has come from the coal fired boiler 2 and passed the denitration device 4 , with the primary recirculation gas 24 and the secondary recirculation gas for AA unit 23 .
  • the primary recirculation gas 24 reaches a temperature suitable for drying the coal pulverized by the coal pulverizer 3
  • the secondary recirculation gas for AA unit 23 reaches a temperature suitable for being introduced to the inside of the furnace through the AA unit 2 b of the coal fired boiler 2 .
  • the dust removal device 5 is for removing dust in the exhaust gas
  • the desulfurization device 6 is for removing sulfur oxide in the introduced exhaust gas.
  • the gas cooler 7 is for cooling the introduced exhaust gas.
  • the secondary recirculation gas for burner 22 is used as diluents for diluting the oxygen introduced from the combustion oxygen supply system 21 .
  • Oxygen introduced from the combustion oxygen supply system 21 and part of exhaust gas (hereinafter referred to as “secondary recirculation gas for AA unit”) 23 purified by passing the smoke removal device 9 are supplied to the AA unit 2 b of the coal fired boiler 2 .
  • the secondary recirculation gas for AA unit 23 is used as dilution gas for diluting the oxygen introduced from the combustion oxygen supply system 21 .
  • the amount of oxygen supplied from the combustion oxygen supply system 21 to the coal fired boiler 2 through the burner unit 2 a and the AA unit 2 b is set to be 1.15 times the theoretical combustion oxygen amount of the coal supplied to the inside of the furnace through the burner unit 2 a .
  • the amount of oxygen supplied to the inside of the furnace of the coal fired boiler 2 is not larger than 1.0 times the theoretical combustion oxygen amount of the coal supplied to the inside of the furnace through the burner unit 2 a.
  • the amount of oxygen supplied through the AA unit 2 b is up to about 40% of the amount of oxygen introduced from the combustion oxygen supply system 21 to the coal fired boiler 2 .
  • the amount of oxygen charged to the inside of the furnace through the burner unit 2 a is made not larger than 1.0 times the theoretical combustion oxygen amount of coal, and oxygen is also charged to the inside of the furnace through the AA unit 2 b .
  • a zone between the burner unit 2 a and the AA unit 2 b becomes short of oxygen. Due to the shortage of oxygen in the zone between the burner unit 2 a and the AA unit 2 b , the zone between the burner unit 2 a and the AA unit 2 b inside the furnace is put in the state of reducing atmosphere.
  • Nitrogen oxide in the exhaust gas generated by combustion of coal and oxygen charged to the inside of the furnace through the burner unit 2 a is reduced when passing the zone under reducing atmosphere through the burner unit 2 a . Consequently, nitrogen oxide in the exhaust gas generated within the coal fired boiler 2 is removed inside the furnace of the coal fired boiler 2 .
  • the concentration of nitrogen oxide contained in the exhaust gas discharged from the coal fired boiler 2 is decreased by in-furnace NOx removal in the coal fired boiler 2 .
  • the exhaust gas with a decreased nitrogen oxide concentration is introduced to the smoke removal device 9 .
  • the concentration of nitrogen oxide decreases, the amount of exhaust gas introduced from the coal fired boiler 2 to the smoke removal device 9 is decreased.
  • the exhaust gas introduced to the smoke removal device 9 is introduced to the denitration device 4 which constitutes the smoke removal device 9 , where residual nitrogen oxide is removed.
  • the exhaust gas with nitrogen oxide removed is introduced to the air heater 8 .
  • the temperature of the exhaust gas introduced to the air heater 8 is high.
  • the high-temperature exhaust gas is subjected to heat exchange with the secondary recirculation gas for AA unit 23 and the primary recirculation gas 24 .
  • the high-temperature exhaust gas introduced from the denitration device 4 is cooled and then introduced to the dust removal device 5 .
  • the exhaust gas introduced to the dust removal device 5 is subjected to removal of dust and the like before being discharged.
  • the exhaust gas discharged from the dust removal device 5 is introduced to the desulfurization device 6 , where sulfuric compounds are removed.
  • the exhaust gas purified through the denitration device 4 , the dust removal device 5 , and the desulfurization device 6 is mostly composed of carbon dioxide and steam.
  • This purified exhaust gas is introduced to the gas cooler 7 , where the temperature thereof is lowered.
  • the exhaust gas whose temperature is lowered by the gas cooler 7 is discharged from the smoke removal device 9 .
  • Part of the exhaust gas discharged from the smoke removal device 9 is introduced to the air heater 8 as secondary recirculation gas for AA unit 23 , where heat exchange is conducted between the secondary recirculation gas for AA unit 23 and the high-temperature exhaust gas discharged from the denitration device 4 , so that the temperature of the secondary recirculation gas for AA unit 23 increases.
  • the thus-obtained high-temperature secondary recirculation gas for AA unit 23 is then introduced to the AA unit 2 b of the coal fired boiler 2 .
  • Part of the exhaust gas discharged from the smoke removal device 9 is further introduced to the air heater 8 as primary recirculation gas 24 .
  • the primary recirculation gas 24 introduced to the air heater 8 is heated by exchanging heat with the high-temperature exhaust gas discharged from the denitration device 4 .
  • the thus-obtained high-temperature primary recirculation gas 24 is then introduced to the coal pulverizer 3 .
  • the high-temperature primary recirculation gas 24 introduced to the coal pulverizer 3 is used as carrier gas for drying coal and for conveying pulverized coal to the coal fired boiler 3 .
  • the exhaust gas purified by the smoke removal device 9 is mostly introduced to a system such as a carbon dioxide recovery system (not shown) where carbon dioxide in the exhaust gas is recovered.
  • a system such as a carbon dioxide recovery system (not shown) where carbon dioxide in the exhaust gas is recovered.
  • the exhaust gas with carbon dioxide, nitrogen oxide, and sulfur oxide removed therefrom is emitted to the outside of the combustion system 1 .
  • the combustion system according to the present embodiment has following operation effects.
  • the secondary recirculation gas for burner (part of exhaust gas) 22 diverging from between the coal fired boiler (combustion furnace) 2 and the smoke removal device 9 is resupplied to the inside of the furnace (not shown) of the coal fired boiler 2 through the burner unit 2 a . Consequently, the exhaust gas containing high-concentration nitrogen oxide introduced to the smoke removal device 9 is decreased. Therefore, it becomes possible to reduce the load of the denitration device 4 .
  • the reducing atmosphere is formed between the burner unit 2 a and the AA unit (combustion oxygen supply port) 2 b of the coal fired boiler 2 . Consequently, the secondary recirculation gas for burner unit 22 diverging from between the coal fired boiler 2 and the smoke removal device 9 can be reduced in the zone under reducing atmosphere formed in the coal fired boiler 2 and then be discharged. This makes it possible to decrease the flow rate of the exhaust gas introduced from the coal fired boiler 2 to the smoke removal device 9 and to decrease the flow rate of nitrogen oxide in smoke. Therefore, the capacity of the smoke removal device 9 can be reduced.
  • the secondary recirculation gas for AA unit 23 which is part of the exhaust gas discharged from the downstream side of the smoke removal device 9 is the exhaust gas having the concentration of nitrogen oxide decreased by the denitration device 4 .
  • This exhaust gas is introduced to the coal fired boiler 2 through the AA unit 2 b and is used for promoting complete combustion of unburned pulverized coal contained in the exhaust gas which is partially reduced by passing the reducing atmosphere inside the furnace of the coal fired boiler 2 . Therefore, the exhaust gas is discharged out of the furnace of the coal fired boiler 2 while the concentration of nitrogen oxide contained therein is maintained low.
  • the exhaust gas having a decreased nitrogen oxide concentration is recirculated between the coal fired boiler 2 and the smoke removal device 9 , so that increase in the concentration of nitrogen oxide in the outlet of the furnace of the coal fired boiler 2 can be suppressed.
  • the exhaust gas with a decreased flow rate of nitrogen oxide is introduced to the denitration device (denitration unit) 4 , so that the amount of ammonia sprayed from the ammonia supply unit (not shown) to the exhaust gas can be decreased as compared with the case where the exhaust gas whose flow rate of nitrogen oxide is not decreased is introduced to the denitration device 4 . Therefore, it becomes possible to downsize the denitration device 4 .
  • a combustion system of the present embodiment is different from the first embodiment in the point that the secondary recirculation gas for AA unit is introduced from between the desulfurization device and the gas cooler.
  • Other structural members are similar to those of the first embodiment. Therefore, like structural members and flows are designated by like reference signs to omit description.
  • FIG. 2 is a schematic structure view of a combustion system according to the second embodiment of the present invention.
  • Oxygen (combustion oxygen) introduced from a combustion oxygen supply system 21 and part of exhaust gas diverging from between a desulfurization device (desulfurization unit) 6 and a gas cooler (cooling unit) 7 which constitute a smoke removal device 9 are supplied to an AA unit (combustion oxygen supply port) 2 b of a coal fired boiler (combustion furnace) 2 as secondary recirculation gas for AA unit 23 .
  • the combustion system according to the present embodiment has following operation effects.
  • the secondary recirculation gas for AA unit (part of exhaust gas) 23 diverging from between the desulfurization device (desulfurization unit) 6 and the gas cooler (cooling unit) 7 is introduced to the AA unit (combustion oxygen supply port) 2 b of the coal fired boiler (combustion furnace) 2 . Accordingly, the flow rate of the exhaust gas introduced to the gas cooler 7 can be decreased. This makes it possible to reduce the capacity of the gas cooler 7 and to decrease the flow rate of nitrogen oxide in the exhaust gas introduced to the denitration device (denitration unit) 4 for the same reason as that in the first embodiment. As a result, the denitration device 4 can be downsized.
  • a combustion system of the present embodiment is different from the first embodiment in the point that the secondary recirculation gas for AA unit is introduced from between the dust removal device and the desulfurization device.
  • Other structural members are similar to those of the first embodiment. Therefore, like structural members and flows are designated by like reference signs to omit description.
  • FIG. 3 is a schematic structure view of a combustion system according to the third embodiment of the present invention.
  • Oxygen (combustion oxygen) introduced from a combustion oxygen supply system 21 and part of exhaust gas diverging from between a dust removal device (dust removal unit) 5 and a desulfurization device (desulfurization unit) 6 which constitute a smoke removal device 9 are supplied to an AA unit (combustion oxygen supply port) 2 b of a coal fired boiler (combustion furnace) 2 as secondary recirculation gas for AA unit 23 .
  • the combustion system according to the present embodiment has following operation effects.
  • the secondary recirculation gas for AA unit (part of exhaust gas) 23 diverging from between the dust removal device (dust removal unit) 5 and the desulfurization device (desulfurization unit) 6 is introduced to the AA unit (combustion oxygen supply port) 2 b . Accordingly, the flow rate of the exhaust gas introduced to the desulfurization device 6 and a gas cooler 7 can be decreased. This makes it possible to reduce the capacity of the desulfurization device 6 and the gas cooler 7 and to decrease the flow rate of nitrogen oxide in the exhaust gas introduced to the denitration device (denitration unit) 4 for the same reason as that in the first embodiment. As a result, the denitration device 4 can be downsized.
  • a combustion system of the present embodiment is different from the first embodiment in the point that the secondary recirculation gas for AA unit is introduced from between the denitration device and the air heater.
  • Other structural members are similar to those of the first embodiment. Therefore, like structural members and flows are designated by like reference signs to omit description.
  • FIG. 4 is a schematic structure view of a combustion system according to the fourth embodiment of the present invention.
  • Oxygen (combustion oxygen) introduced from a combustion oxygen supply system 21 and part of exhaust gas diverging from between a denitration device (denitration unit) 4 and an air heater (heat exchange unit) 8 which constitute a smoke removal device 9 are supplied to an AA unit (combustion oxygen supply port) 2 b of a coal fired boiler (combustion furnace) 2 as secondary recirculation gas for AA unit 23 .
  • the combustion system according to the present embodiment has following operation effects.
  • the secondary recirculation gas for AA unit (part of exhaust gas) 23 diverging from between the denitration device (denitration unit) 4 and the air heater (heat exchange unit) 8 is introduced to the AA unit (combustion oxygen supply port) 2 b . Accordingly, the flow rate of the exhaust gas introduced to the air heater 8 , the dust removal device (dust removal unit) 5 , the desulfurization device (desulfurization unit) 6 , and the gas cooler (cooling unit) 7 can be decreased.
  • the denitration device 4 can be downsized.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Combustion Of Fluid Fuel (AREA)
  • Chimneys And Flues (AREA)
US13/703,737 2010-06-16 2011-01-17 Combustion system Abandoned US20130092062A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2010137211A JP5535782B2 (ja) 2010-06-16 2010-06-16 燃焼システム
JP2010-137211 2010-06-16
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EP2584257A1 (en) 2013-04-24
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TW201200811A (en) 2012-01-01
AU2011266461A1 (en) 2013-01-10
EP2584257A4 (en) 2015-10-21
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MY167039A (en) 2018-08-02
CA2802411A1 (en) 2011-12-22
WO2011158521A1 (ja) 2011-12-22
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AU2011266461B2 (en) 2014-08-28
CN103003632A (zh) 2013-03-27

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