CN210332238U - Three-section type ammonia denitration system by urea pyrolysis - Google Patents
Three-section type ammonia denitration system by urea pyrolysis Download PDFInfo
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- CN210332238U CN210332238U CN201920255898.5U CN201920255898U CN210332238U CN 210332238 U CN210332238 U CN 210332238U CN 201920255898 U CN201920255898 U CN 201920255898U CN 210332238 U CN210332238 U CN 210332238U
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Abstract
The utility model relates to a syllogic urea pyrolysis system ammonia deNOx systems belongs to the electric power production field. The process for preparing ammonia by urea pyrolysis has high safety performance, but has the problems of high operating cost, easy blockage and the like. The system mainly comprises a raw material bin, a spiral feeder, a solution preparation device, a solution delivery pump, a low-pressure solution preheater, a solution buffer tank, a booster pump, a recirculation valve, a high-pressure solution regulating valve, a flowmeter, a high-pressure solution heater, a pyrolysis reactor, a dilution mixer, a fan and the like. Compared with other methods, the utility model discloses divide into the flow of three-section series connection with urea pyrolysis process, promptly: urea dissolving preheating, high-pressure solution heating and urea solution complete decomposition. The device is in indirect contact with a high-temperature flue gas heat source, so that the device has the technical characteristics of low operating cost, effective avoidance of system blockage and the like.
Description
Technical Field
The utility model relates to a urea pyrolysis system ammonia deNOx systems belongs to the electric power production field.
Background
Over 90% of coal-fired boilers of large power stations select SCR selective catalytic reduction denitration technology for removing NOx in flue gas. Liquid ammonia, ammonia water or urea is generally selected as the denitration reducing agent. Liquid ammonia and ammonia water have toxicity, corrosivity and easy explosiveness, belong to major hazard sources, and bring great potential safety hazards to the actual production process. Compared with the prior art, the urea has the advantages of no toxicity, safe use, convenient storage and transportation and the like, and is gradually and rapidly popularized and applied to SCR denitration projects of a plurality of coal-fired power plants, such as Chinese patent with the application number of 201811380706. X.
At present, most of the processes for preparing ammonia by urea pyrolysis are provided with a heat-insulating decomposition chamber, high-temperature hot flue gas generated by combustion of diesel oil/natural gas or electrically heated high-temperature air is used as a heat source, and the heat source is directly contacted with a urea solution to decompose the urea solution to generate diluted ammonia gas, and then the diluted ammonia gas is sent into a denitration reactor by an ammonia injection grid.
However, this technique has problems such as high running cost and easy clogging of the adiabatic decomposition chamber, which affects the economy and reliability of the production system. For example, for a system using oil or gas as a heat source, the annual average operating cost of 1 unit with 600MW level exceeds 400 ten thousand yuan; the annual average running cost of the unit with the same capacity is about 150 ten thousand yuan by adopting the system of electrically heating air as a heat source. In addition, factors such as low temperature of the heat-insulating decomposition chamber, poor atomization effect of the nozzle, oil-containing and dust-containing smoke or air and the like can cause rapid formation of crystalline deposits in a short period of time, block the heat-insulating decomposition chamber and cause safety production accidents.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to overcome the above-mentioned not enough that exists among the prior art, provide a syllogic urea pyrolysis system ammonia deNOx systems. Compared with the prior urea pyrolysis process system, the method has the technical advantages of low operation cost, effective prevention of formation of crystalline deposits and high operation reliability.
The utility model provides a technical scheme that above-mentioned problem adopted is: the utility model provides a syllogic urea pyrolysis system ammonia deNOx systems, its characterized in that, includes boiler, denitration reactor and air heater, the boiler loops through horizontal flue, turns to room and perpendicular uptake flue and denitration reactor intercommunication, and denitration reactor and air heater intercommunication, high temperature over heater and high temperature re-heater have been arranged in the horizontal flue, turn to room below and have arranged the economizer ash bucket.
The three-section type urea pyrolysis ammonia production denitration system further comprises a raw material bin, a screw feeder, a solution preparation device, a solution delivery pump, a low-pressure solution preheater, a solution buffer tank, a booster pump, a flowmeter, a high-pressure solution heater, a pyrolysis reactor, a dilution mixer and a fan; the raw material bin, the spiral feeder, the solution preparation device and the solution delivery pump are sequentially connected, a solvent control valve is installed on a solvent pipeline of the solution preparation device, the low-pressure solution preheater is arranged in a flue between the denitration reactor and the air preheater, an inlet and an outlet of the low-pressure solution preheater are respectively connected with an outlet of the solution delivery pump and a solution buffer tank, the solution buffer tank is further communicated with an inlet of the booster pump, an outlet pipeline of the booster pump is divided into two paths, one path is communicated with an outlet pipeline of the low-pressure solution preheater through a recirculation valve, the other path is communicated with an inlet pipeline of the high-pressure solution heater through a high-pressure solution regulating valve and a flowmeter in sequence, the high-pressure solution heater is arranged in a horizontal flue, the high-pressure solution heater is positioned in an area between the high-temperature superheater and the high-temperature reheater, an outlet of the high, the pyrolysis reactor is arranged in the steering chamber, an outlet of the pyrolysis reactor and an outlet of the fan are respectively communicated with the dilution mixer, and an outlet of the dilution mixer is communicated with a vertical uptake flue in front of the denitration reactor.
The three-section type ammonia denitration system prepared by urea pyrolysis has the working method that: the urea raw material stored in the raw material bin is sent into the solution preparation device through the screw feeder and is mutually mixed and dissolved with water to generate urea solution, and the mass fraction, namely the water flow, of the urea solution is controlled by the solvent control valve. And then, the urea solution is conveyed into a low-pressure solution preheater through a solution conveying pump for primary temperature rise, so that the urea solution is prevented from being recrystallized. The urea solution after the preliminary temperature rise is conveyed to a solution buffer tank for storage, then is divided into two parts after a pressure head is improved through a booster pump, one part returns to the solution buffer tank again after passing through a recirculation valve, and the other part is sent to a high-pressure solution heater for thorough heating after sequentially passing through a high-pressure solution regulating valve and a flowmeter so as to reach the temperature close to the rapid decomposition of the urea solution.
The flow rate of the pyrolysis urea solution for the denitration system is measured by a flowmeter and is controlled by a high-pressure solution regulating valve. The solution buffer tank provides a stable urea solution source for the booster pump on the one hand, and on the other hand, the solution buffer tank is matched with the recirculation valve and the high-pressure solution regulating valve, so that the urea solution flow entering the high-pressure solution heater can be accurately controlled, and the solution storage and pressure buffer effects are achieved. The urea solution temperature of high pressure solution heater export very approaches its quick decomposition temperature, then is sent into the pyrolysis reactor and heats the intensification, thoroughly carries out the reaction of pyrolysis process, generates ammonia and carbon dioxide, includes following two main reactions:
CO(NH2)2→ HNCO + NH3
HNCO + H2O → CO2+ NH3
the high-pressure solution heater and the pyrolysis reactor are arranged in a mode of being parallel to the flowing direction of the flue gas so as to reduce the temperature of the pipe wall on the high-temperature side. Compared with a high-pressure solution heater, the pyrolysis reactor is arranged in a turning chamber area with relatively low flue gas temperature, so that the temperature of the pipe wall of the pyrolysis reactor is reduced, and the safety of equipment is improved. And the ammonia gas and the carbon dioxide flowing out of the pyrolysis reactor enter a dilution mixer and are mixed with air fed by a fan, so that the concentration of the ammonia gas is reduced to be lower than the lower explosion limit of the ammonia gas on one hand, and the temperature of the ammonia gas is properly reduced on the other hand. The mixed gas of the ammonia gas and the air flowing out of the dilution mixer is sent into a vertical uptake flue in front of the denitration reactor, is mixed with the flue gas subjected to preliminary ash removal by an ash hopper of the coal economizer, and finally enters an inlet of the denitration reactor together for removing NOx.
The utility model provides a system divide into the three-section flow with urea pyrolysis process, promptly: dissolving and preheating urea materials to prepare a low-pressure solution with stable chemical properties, heating the high-pressure solution to a rapid decomposition temperature, and completely decomposing the urea solution to prepare ammonia. Because an adiabatic decomposition chamber in the traditional urea pyrolysis process is omitted, the self flue gas heat of the boiler is used as a power heat source for urea pyrolysis, diesel oil, natural gas or electric energy is not needed, and the initial investment and the operating cost of the system are greatly reduced. In addition, in traditional technology, the mode that urea solution and high temperature flue gas or high temperature air direct contact carry out the pyrolysis is compared, the utility model discloses cut apart the indirect contact process of three series connection with urea pyrolysis process, fundamentally has stopped the formation of crystallization deposit, can effectively avoid the problem of system's jam.
Drawings
Fig. 1 is a schematic structural diagram of a system according to an embodiment of the present invention.
In the figure: 1-boiler, 2-high temperature superheater, 3-high pressure solution heater, 4-high temperature reheater, 5-pyrolysis reactor, 6-dilution mixer, 7-blower, 8-vertical uptake flue, 9-flowmeter, 10-high pressure solution regulating valve, 11-booster pump, 12-recirculation valve, 13-solution buffer tank, 14-denitration reactor, 15-low pressure solution preheater, 16-raw material bin, 17-screw feeder, 18-solution preparation device, 19-solvent control valve, 20-solution delivery pump, 21-air preheater, 22-economizer ash bucket, 23-diversion chamber, 24-horizontal flue.
Detailed Description
The present invention will be described in further detail by way of examples with reference to the accompanying drawings, which are illustrative of the present invention and are not intended to limit the present invention.
Examples are given.
Referring to fig. 1, the three-stage urea pyrolysis ammonia production denitration system in the embodiment includes a boiler 1, a denitration reactor 14 and an air preheater 21, the boiler 1 is communicated with the denitration reactor 14 sequentially through a horizontal flue 24, a turning chamber 23 and a vertical uptake flue 8, the denitration reactor 14 is communicated with the air preheater 21, a high-temperature superheater 2 and a high-temperature reheater 4 are arranged in the horizontal flue 24, and an economizer ash hopper 22 is arranged below the turning chamber 23.
The three-section type urea pyrolysis ammonia production denitration system further comprises a raw material bin 16, a screw feeder 17, a solution preparation device 18, a solution delivery pump 20, a low-pressure solution preheater 15, a solution buffer tank 13, a booster pump 11, a flowmeter 9, a high-pressure solution heater 3, a pyrolysis reactor 5, a dilution mixer 6 and a fan 7; the raw material bin 16, the screw feeder 17, the solution preparation device 18 and the solution delivery pump 20 are sequentially connected, a solvent control valve 19 is installed on a solvent pipeline of the solution preparation device 18, the low-pressure solution preheater 15 is arranged in a flue between the denitration reactor 14 and the air preheater 21, an inlet and an outlet of the low-pressure solution preheater 15 are respectively connected with an outlet of the solution delivery pump 20 and the solution buffer tank 13, the solution buffer tank 13 is further communicated with an inlet of the booster pump 11, an outlet pipeline of the booster pump 11 is divided into two paths, one path is communicated with the outlet pipeline of the low-pressure solution preheater 15 through the recirculation valve 12, the other path is communicated with an inlet pipeline of the high-pressure solution heater 3 through the high-pressure solution regulating valve 10 and the flowmeter 9, the high-pressure solution heater 3 is arranged in the horizontal flue 24, and the high-pressure solution heater 3 is located in an area between the high-temperature superheater 2 and the high, the outlet of the high-pressure solution heater 3 is communicated with the inlet of a pyrolysis reactor 5, the pyrolysis reactor 5 is arranged in a turning chamber 23, the outlet of the pyrolysis reactor 5 and the outlet of a fan 7 are respectively communicated with a dilution mixer 6, and the outlet of the dilution mixer 6 is communicated with a vertical uptake flue 8 in front of a denitration reactor 14.
The working method of the system comprises the following steps: the urea raw material stored in the raw material bin 16 is fed into a solution preparation device 18 through a screw feeder 17, and is mixed and dissolved with water to generate a urea solution with the mass fraction of 50%, and the water flow required by the process is controlled by a solvent control valve 19. Then, the urea solution is sent to the low-pressure solution preheater 15 through the solution delivery pump 20 to be primarily heated to 50 ℃ to prevent the urea solution from being recrystallized. The urea solution after the preliminary temperature rise is conveyed to a solution buffer tank 13 for storage, then the solution pressure is increased to 15kPa through a booster pump 11, the solution is divided into two parts, one part returns to the solution buffer tank 13 after passing through a recirculation valve 12, and the other part is conveyed to a high-pressure solution heater 3 to be thoroughly heated to 130 ℃ after passing through a high-pressure solution regulating valve 10 and a flowmeter 9 in sequence, so as to reach the temperature close to the rapid decomposition of the urea solution.
The flow of the pyrolysed urea solution for the denitration system is measured by a flow meter 9 and controlled by a high pressure solution regulating valve 10. The solution buffer tank 13 provides a stable urea solution source for the booster pump 11, and is matched with the recirculation valve 12 and the high-pressure solution regulating valve 10 to accurately control the flow rate of the urea solution entering the high-pressure solution heater 3, and simultaneously plays roles in solution storage and pressure buffering. The urea solution at the outlet of the high-pressure solution heater 3 enters the pyrolysis reactor 5 to be heated and heated, the reaction in the pyrolysis process is thoroughly carried out, ammonia and carbon dioxide are generated, and the method comprises the following two main reactions:
CO(NH2)2→ HNCO + NH3
HNCO + H2O → CO2+ NH3
the high-pressure solution heater 3 and the pyrolysis reactor 5 are arranged in a mode of being parallel to the flowing direction of the flue gas so as to reduce the temperature of the pipe wall on the high-temperature side. Compared with the high-pressure solution heater 3, the pyrolysis reactor 5 is arranged in the region of the turning chamber 23 with relatively low flue gas temperature, so that the temperature of the pipe wall of the pyrolysis reactor is reduced, and the safety of equipment is improved. The ammonia gas and the carbon dioxide flowing out of the pyrolysis reactor 5 enter a dilution mixer 6 to be mixed with the air fed by a fan 7, so that the concentration of the ammonia gas is reduced to 5%, and the temperature of the mixed gas is reduced to 340 ℃. The mixed gas of the ammonia gas and the air flowing out of the dilution mixer 6 is sent into the vertical uptake flue 8 in front of the denitration reactor 14, is mixed with the flue gas subjected to preliminary ash removal by the economizer ash bucket 22, and finally enters the inlet of the denitration reactor 14 together for removing NOx.
Although the present invention has been described with reference to the above embodiments, it should not be construed as being limited to the scope of the present invention, and any modifications and alterations made by those skilled in the art without departing from the spirit and scope of the present invention should fall within the scope of the present invention.
Claims (3)
1. A three-section type urea pyrolysis ammonia production denitration system comprises a boiler (1), a denitration reactor (14) and an air preheater (21), wherein the boiler (1) is communicated with the denitration reactor (14) sequentially through a horizontal flue (24), a steering chamber (23) and a vertical ascending flue (8), the denitration reactor (14) is communicated with the air preheater (21), a high-temperature superheater (2) and a high-temperature reheater (4) are arranged in the horizontal flue (24), and an economizer ash hopper (22) is arranged below the steering chamber (23); the device is characterized by also comprising a raw material bin (16), a screw feeder (17), a solution preparation device (18), a solution delivery pump (20), a low-pressure solution preheater (15), a solution buffer tank (13), a booster pump (11), a flowmeter (9), a high-pressure solution heater (3), a pyrolysis reactor (5), a dilution mixer (6) and a fan (7); the raw material bin (16), the screw feeder (17), the solution preparation device (18) and the solution delivery pump (20) are sequentially connected, a solvent control valve (19) is installed on a solvent pipeline of the solution preparation device (18), the low-pressure solution preheater (15) is arranged in a flue between the denitration reactor (14) and the air preheater (21), an inlet and an outlet of the low-pressure solution preheater (15) are respectively connected with an outlet of the solution delivery pump (20) and the solution buffer tank (13), the solution buffer tank (13) is also communicated with an inlet of the booster pump (11), an outlet pipeline of the booster pump (11) is divided into two paths, one path is communicated with an outlet pipeline of the low-pressure solution preheater (15) through a recirculation valve (12), and the other path is communicated with an inlet pipeline of the high-pressure solution heater (3) through a high-pressure solution regulating valve (10) and a flow meter (9) in sequence, the outlet of the high-pressure solution heater (3) is communicated with the inlet of the pyrolysis reactor (5), the outlet of the pyrolysis reactor (5) and the outlet of the fan (7) are respectively communicated with the dilution mixer (6), and the outlet of the dilution mixer (6) is communicated with the vertical uptake flue (8) in front of the denitration reactor (14).
2. The system of claim 1, wherein the high-pressure solution heater (3) is arranged in the horizontal flue (24), the high-pressure solution heater (3) is located between the high-temperature superheater (2) and the high-temperature reheater (4), and the pyrolysis reactor (5) is arranged in the diversion chamber (23).
3. The three-stage urea pyrolysis ammonia production denitration system of claim 2, wherein the high-pressure solution heater (3) and the pyrolysis reactor (5) are arranged in a manner of being co-current to a flow direction of flue gas.
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| CN109876626A (en) * | 2019-02-28 | 2019-06-14 | 华电电力科学研究院有限公司 | A kind of three-stage urea pyrolysis ammonia denitrating system and its working method |
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| CN109876626A (en) * | 2019-02-28 | 2019-06-14 | 华电电力科学研究院有限公司 | A kind of three-stage urea pyrolysis ammonia denitrating system and its working method |
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