CN-122006587-A - Flue gas denitration system based on ammonium carbamate

CN122006587ACN 122006587 ACN122006587 ACN 122006587ACN-122006587-A

Abstract

The invention discloses a flue gas denitration system based on ammonium carbamate, which comprises a feeding unit, a pyrolysis unit, a gas transmission unit, a reaction unit and an ammonia control unit, wherein the ammonia control unit is used for cooperatively regulating and controlling the feeding rate of the feeding unit, the pyrolysis working condition of the pyrolysis unit and the ammonia nitrogen molar ratio output by the gas transmission unit according to flue gas parameters at an inlet of the reaction unit. The invention not only overcomes the problems of high safety risk and corrosiveness of the traditional liquid ammonia and ammonia water, but also overcomes the defects of high energy consumption and byproduct blockage of the ammonia preparation by urea, and solves the problems of lagging ammonia control logic of the traditional system by adopting the characteristics of low pyrolysis temperature and no byproducts of the ammonium carbamate, through the feed redundancy design, pyrolysis uniformity optimization and accurate control of the ammonia concentration, thereby realizing the high-efficiency utilization of the ammonia gas and the high-efficiency removal of the nitrogen oxides, remarkably improving the denitration efficiency and the system stability, and simultaneously reducing the operation cost and the equipment maintenance frequency.

Inventors

LI YUZHE
ZHONG LI
ZHANG MAOLONG
ZHANG JIRUI
QIN PENGFEI
LI WEI
LIU LIANBO
LU DAYONG
WANG LIANGLIANG

Assignees

北京华能长江环保科技研究院有限公司
华能巢湖发电有限责任公司

Dates

Publication Date: 20260512
Application Date: 20260226

Claims (10)

1. An ammonium carbamate-based flue gas denitration system, comprising: a feeding unit (1), the feeding unit (1) being used for storing and quantitatively delivering ammonium carbamate powder; the pyrolysis unit (2) is connected with the feeding unit (1) and is used for receiving and pyrolyzing the ammonium carbamate powder to generate a mixed gas of ammonia and carbon dioxide; The gas transmission unit (3), the gas transmission unit (3) is connected with a mixed gas outlet (2012) of the pyrolysis unit (2) and is used for transmitting the mixed gas and adjusting the concentration of ammonia in the mixed gas; The reaction unit (4) is arranged in the flue, and the reaction unit (4) comprises an SCR reactor or an SNCR reactor and is used for enabling ammonia in the mixed gas to react with nitrogen oxides in the flue gas; The ammonia control unit is in signal connection with the feeding unit (1), the pyrolysis unit (2) and the gas transmission unit (3), and is used for cooperatively regulating and controlling the feeding rate of the feeding unit (1), the pyrolysis working condition of the pyrolysis unit (2) and the ammonia nitrogen molar ratio output by the gas transmission unit (3) according to the flue gas parameters of the inlet of the reaction unit (4).
2. The ammonium carbamate based flue gas denitration system according to claim 1, wherein the feeding unit (1) comprises a bin (101), a screw conveyor (102) and an air dryer (103), the bin (101) is used for storing ammonium carbamate powder, a feed inlet (2011) of the screw conveyor (102) is communicated with the bin (101), a discharge outlet of the screw conveyor (102) is communicated with the pyrolysis unit (2), the air dryer (103) is communicated with the bin (101) through a fluidization air pipeline (104) for conveying fluidization air into the bin (101), the air dryer (103) is communicated with a discharge end of the screw conveyor (102) through a sealing air pipeline (105) for providing sealing air, and the air dryer (103) is communicated with a feed inlet (2011) of the pyrolysis unit (2) through a stirring air pipeline (106) for conveying stirring air.
3. The flue gas denitration system based on ammonium carbamate according to claim 2, wherein the dew point of the dry air output by the air cooling dryer (103) is less than or equal to-30 ℃, the pressure is 5kPa to 10kPa, and the granularity of the output material of the screw conveyor (102) is less than or equal to 8mm.
4. The ammonium carbamate based flue gas denitration system according to claim 1, characterized in that the pyrolysis unit (2) comprises a pyrolysis furnace (201), a hot air blower (202), a cyclone separator (203) and a return feeder (204), the pyrolysis furnace (201) having a feed inlet (2011), a mixed gas outlet (2012), a return inlet (2013) and a slag discharge outlet (2014), the hot air blower (202) being connected to the pyrolysis furnace (201) for providing fluidizing hot air, the cyclone separator (203) having a mixed gas inlet (2031), a gas outlet (2032) and a solids outlet (2033), the mixed gas inlet (2031) being in communication with the mixed gas outlet (2012), the gas outlet (2032) being in communication with the gas delivery unit (3), the solids outlet (3) being in communication with the return inlet (2013) of the pyrolysis furnace (201) via the return feeder (204) for returning separated non-pyrolyzed ammonium carbamate powder into the slag discharge furnace (201), the solids outlet (2033) being used for discharging waste material in the pyrolysis furnace (201).
5. The ammonium carbamate based flue gas denitration system according to claim 4, wherein the pyrolysis furnace (201) is a multi-chamber bubbling bed pyrolysis furnace (201), the pyrolysis temperature in the pyrolysis furnace (201) is 200 ℃ to 300 ℃, the pressure in the pyrolysis furnace (201) is 4kPa to 8kPa, and the fluidization velocity of hot air in the pyrolysis furnace (201) is 0.6m/s to 3m/s.
6. The flue gas denitration system based on ammonium carbamate according to claim 4, wherein an air distribution plate (205) and a bell jar type cored pipe hood (206) are arranged in the pyrolysis furnace (201), the air distribution plate (205) divides the interior of the pyrolysis furnace (201) into an upper pyrolysis chamber (207) and a lower air distribution chamber (208), the air heater (202) is communicated with the air distribution chamber (208), and the bell jar type cored pipe hood (206) is arranged on the air distribution plate (205) in a penetrating mode and is used for uniformly guiding hot air in the air distribution chamber (208) into the pyrolysis chamber (207).
7. The flue gas denitration system based on ammonium carbamate according to claim 1, wherein the gas transmission unit (3) comprises a gas transmission pipeline (301), an ammonia spraying gun (302) and a dilution fan (303), an inlet of the gas transmission pipeline (301) is communicated with the pyrolysis unit (2), a heat tracing component is arranged on the outer wall of the gas transmission pipeline (301) to maintain the temperature of the gas transmission pipeline to be 140 ℃ or higher, the ammonia spraying gun (302) is arranged in the flue and communicated with an outlet of the gas transmission pipeline (301), and the dilution fan (303) is arranged on the gas transmission pipeline (301) and is used for introducing clean air to adjust the concentration of ammonia in the gas transmission pipeline (301) to be 5% or lower.
8. The flue gas denitration system based on ammonium carbamate according to claim 7, wherein the gas transmission unit (3) further comprises a three-way valve (304) and an absorption tower (305), the three-way valve (304) is arranged on the gas transmission pipeline (301), the absorption tower (305) is communicated with one outlet of the three-way valve (304), and an absorbent is arranged in the absorption tower (305) and is used for absorbing and treating ammonia in the gas transmission pipeline (301).
9. The ammonium carbamate based flue gas denitration system of claim 1, wherein the ammonia control unit comprises: The flue gas monitoring module is used for monitoring the flue gas flow of the inlet of the reaction unit (4) and the concentration of nitrogen oxides in the flue gas; the ammonia spraying adjusting module (501) is connected with the feeding unit (1) and the gas transmission unit (3) and is used for adjusting the feeding rate of the feeding unit (1) and the ammonia nitrogen molar ratio output by the gas transmission unit (3); the hot air control module (502), hot air control module (502) with pyrolysis unit (2) are connected, are used for adjusting pyrolysis operating mode of pyrolysis unit (2).
10. The flue gas denitration system based on ammonium carbamate according to claim 1, wherein when the reaction unit (4) is an SCR reactor, the ammonia control unit regulates the ammonia nitrogen molar ratio output by the gas transmission unit (3) to be 1.05-1.15, and when the reaction unit (4) is an SNCR reactor, the ammonia control unit regulates the ammonia nitrogen molar ratio output by the gas transmission unit (3) to be 1.2-1.5.

Description

Flue gas denitration system based on ammonium carbamate Technical Field The invention relates to the technical field of flue gas purification, in particular to a flue gas denitration system based on ammonium carbamate. Background In the flue gas denitration technology, SCR and SNCR processes are widely applied, but the process for preparing ammonia by using a reducing agent has obvious defects, the storage and transportation safety risks of liquid ammonia and ammonia water are high, the corrosiveness is strong, the ammonia preparation by using urea needs high-temperature hydrolysis or pyrolysis, the energy consumption is high, biuret and other byproducts are easy to generate, and the equipment is blocked and the ammonia escape exceeds the standard. The ammonium carbamate is taken as an intermediate product in urea production, has the advantages of low pyrolysis temperature, low raw material cost, no byproducts and the like, but the existing system still has the problems of insufficient feeding redundancy, uneven pyrolysis, lack of ammonia concentration control, lag of ammonia control logic and the like, and affects the denitration efficiency and stability. Disclosure of Invention The present invention aims to solve at least one of the technical problems in the related art to some extent. To this end, embodiments of the present invention provide an ammonium carbamate-based flue gas denitration system. The flue gas denitration system based on the ammonium carbamate comprises a feeding unit, a pyrolysis unit, a gas transmission unit, a reaction unit and an ammonia control unit, wherein the feeding unit is used for storing and quantitatively conveying the ammonium carbamate powder, the pyrolysis unit is connected with the feeding unit and used for receiving and pyrolyzing the ammonium carbamate powder to generate mixed gas of ammonia and carbon dioxide, the gas transmission unit is connected with a mixed gas outlet of the pyrolysis unit and used for conveying the mixed gas and adjusting the concentration of the ammonia in the mixed gas, the reaction unit is arranged in a flue and comprises an SCR (selective catalytic reduction) reactor or an SNCR (selective catalytic reduction) reactor and used for enabling the ammonia in the mixed gas to react with nitrogen oxides in the flue gas, and the ammonia control unit is in signal connection with the feeding unit, the pyrolysis unit and the gas transmission unit and used for cooperatively adjusting the feeding rate of the feeding unit, the working condition of the pyrolysis unit and the ammonia nitrogen molar ratio output by the gas transmission unit according to flue gas parameters of an inlet of the reaction unit. In some embodiments, the feeding unit includes a bin, a screw conveyor and an air dryer, the bin is used for storing ammonium carbamate powder, a feed inlet of the screw conveyor is communicated with the bin, a discharge outlet of the screw conveyor is communicated with the pyrolysis unit, the air dryer is communicated with the bin through a fluidization air pipeline and is used for conveying fluidization air into the bin, the air dryer is communicated with a discharge end of the screw conveyor through a sealing air pipeline and is used for providing sealing air, and the air dryer is communicated with a feed inlet of the pyrolysis unit through a stirring air pipeline and is used for conveying stirring air. In some embodiments, the dew point of the dry air output by the air cooling dryer is less than or equal to-30 ℃ and the pressure is 5kPa to 10kPa, and the granularity of the output material of the screw conveyor is less than or equal to 8mm. In some embodiments, the pyrolysis unit comprises a pyrolysis furnace, an air heater, a cyclone separator and a material returning device, wherein the pyrolysis furnace is provided with a feed inlet, a mixed gas outlet, a material returning opening and a slag discharging opening, the air heater is connected with the pyrolysis furnace and used for providing fluidization hot air, the cyclone separator is provided with a mixed gas inlet, a gas outlet and a solid outlet, the mixed gas inlet is communicated with the mixed gas outlet, the gas outlet is communicated with the gas conveying unit, the solid outlet is communicated with the material returning opening of the pyrolysis furnace through the material returning device and used for returning separated non-pyrolyzed ammonium carbamate powder into the pyrolysis furnace, and the slag discharging opening is used for discharging waste materials in the pyrolysis furnace. In some embodiments, the pyrolysis furnace is a multi-chamber bubbling bed pyrolysis furnace, the pyrolysis temperature within the pyrolysis furnace is 200 ℃ to 300 ℃, the pressure within the pyrolysis furnace is 4kPa to 8kPa, and the fluidization velocity of the hot air within the pyrolysis furnace is 0.6m/s to 3m/s. In some embodiments, an air distribution plate and a bell-type cored pipe hood are arranged