Nitrogen oxide treatment device for boiler tail gas emission

Abstract

The utility model belongs to the technical field of boiler flue gas denitration, and particularly relates to a boiler tail gas emission nitric oxide treatment device which comprises a flue gas channel. The superheater is arranged in the flue gas channel; the economizer is arranged behind the superheater; the flue gas guide plate is arranged behind the coal economizer and is used for uniformly distributing flue gas; the ammonia spraying grid is arranged behind the flue gas guide plate; the catalyst layer is arranged behind the ammonia spraying grid; the ammonia spraying grids are arranged in the flue gas channel, the ammonia spraying grids are uniformly distributed in the flue gas channel, automatic regulating valves are arranged on the ammonia spraying grids, and the detector is used for detecting the content of nitrogen oxides and is electrically connected with the automatic regulating valves. According to the scheme, the problem that the consumption of ammonia gas is too large or too small is solved.

Description

Technical Field

[0001] The utility model belongs to the technical field of boiler flue gas denitrification, and particularly relates to a device for treating nitrogen oxides in boiler tail gas emissions. Background Art

[0002] Nitrogen oxides (NOx) are gases that can cause serious pollution to the atmospheric environment. Common methods for removing nitrogen oxides include selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR). The SNCR method requires a large amount of reducing agent, has a low efficiency of removing NOx, and has a simple system with less initial investment capital; the SCR method requires less reducing agent, has a high efficiency of removing NOx, but has a complex system with higher investment capital and a high cost of the catalyst layer used.

[0003] Currently, an existing system for removing nitrogen oxides from boiler flue gas with the publication number CN202021014U includes a reducing agent solution preparation system located outside the boiler, an SNCR reducing agent solution supply and control device located outside the boiler connected thereto, an SNCR reducing agent solution injector group located at the outlet of the boiler furnace connected to the SNCR reducing agent solution supply and control device through an SNCR reducing agent solution pipeline, and an SCR reactor located in the boiler tail flue; it also includes an SCR reducing agent solution supply and control device and an SCR reducing agent solution injector group, and the SCR reducing agent solution injector group is connected to the SCR reducing agent solution supply and control device through an SCR reducing agent solution pipeline; this solution solves the problems in the prior art that the SCR section of the SNCR / SCR hybrid denitrification process has a low denitrification efficiency, a high reducing agent cost when the SCR section has a high denitrification efficiency, and it is difficult to achieve automatic control of the comprehensive denitrification efficiency.

[0004] However, there is also a problem: if ammonia (NH3) is used as a reducing agent and the dosage is too much and fails to fully react with NOx, it will be emitted into the atmosphere in the form of NH3. Summary of the Utility Model

[0005] The utility model provides a device for treating nitrogen oxides in boiler tail gas emissions to solve the problem of excessive or insufficient ammonia dosage.

[0006] This solution provides a device for treating nitrogen oxides in boiler tail gas emissions, including a flue gas passage; a superheater: the superheater is arranged in the flue gas passage; an economizer: the economizer is arranged behind the superheater; a flue gas deflector: the flue gas deflector is arranged behind the economizer, and the flue gas deflector is used to make the flue gas distribution uniform; an ammonia injection grid: the ammonia injection grid is arranged behind the flue gas deflector; a catalyst layer: the catalyst layer is arranged behind the ammonia injection grid; there are multiple ammonia injection grids, the ammonia injection grids are evenly distributed in the flue gas passage, and automatic regulating valves are arranged on the ammonia injection grids. It also includes a detector: the detector is used to detect the content of nitrogen oxides, and the detector is electrically connected to the automatic regulating valve.

[0007] The principle of this solution is as follows: The flue gas generated by the boiler will enter the flue gas passage. The flue gas will first pass through the superheater, and the waste heat of the flue gas is used to reheat the saturated steam in the superheater to convert it into superheated steam. Compared with saturated steam, superheated steam has a higher temperature and a lower density. Then the flue gas will pass through the economizer, and the waste heat of the flue gas is used again to heat the boiler feed water in the economizer, reducing the amount of fuel required to heat the feed water after entering the boiler, thus saving fuel and improving energy utilization efficiency. Then the flue gas with reduced temperature will pass through the flue gas deflector, making the flue gas evenly distributed in the flue gas passage. After that, the flue gas will come into contact with the detector, and the detector can detect the content of nitrogen oxides in the flue gas. Then, through the controller in the nitrogen oxides content detector, the size of the automatic regulating valve will be adjusted so that when the flue gas passes through the ammonia injection grid, the amount of ammonia sprayed by the ammonia injection grid is appropriate. Finally, the mixed gas undergoes a reaction through the catalyst layer to neutralize the nitrogen oxides in the flue gas, completing the treatment of nitrogen oxides.

[0008] The beneficial effects of this solution are as follows: 1. This solution cools down the flue gas before detection to prevent high-temperature flue gas from damaging the detector. 2. This solution can automatically adjust the amount of ammonia used to prevent excessive use, which may not fully react with NOx and will be discharged into the atmosphere in the form of NH3, causing air pollution.

[0009] Furthermore, the superheater includes a platen superheater, a high-temperature superheater, and a low-temperature superheater, and the platen superheater, high-temperature superheater, and low-temperature superheater are arranged in sequence in the flue gas passage. The staged heating reduces the thermal stress of a single superheater, reduces the risks of high-temperature corrosion and thermal fatigue, and extends the service life of the equipment. Through the staged superheater, the superheat degree of the steam can be precisely controlled to ensure that the steam has stable temperature and pressure before entering the steam turbine, avoiding damage to the steam turbine blades caused by wet steam.

[0010] Further, it also includes an air preheater which is arranged at the end of the flue gas passage. The air preheater recovers the last remaining waste heat from the flue gas being discharged. The flue gas releases part of its heat in the air preheater, causing its temperature to drop, thereby reducing the heat loss due to flue gas discharge and improving the overall thermal efficiency of the boiler.

[0011] Further, it also includes a cleaning mechanism. The cleaning mechanism includes a scraper, a spring, a piston, and a blocking passage. The scraper is provided with a through-hole which is matched with the catalyst layer. The blocking passage is communicated with the flue gas passage. The piston is slidably connected to the blocking passage. The scraper is fixedly connected to the piston. The blocking passage is arranged between the catalyst layer and the ammonia injection grid. One end of the spring is fixedly connected to the piston, and the other end is fixedly connected to the blocking passage.

[0012] There are many catalyst rods in the catalyst layer. During long-term use, a lot of impurities will adhere to the surface, resulting in the catalyst rods being unable to contact the mixed gas and reducing the reaction efficiency. In this solution, when too many impurities adhere to the catalyst rods, the passage space at the catalyst layer will become narrower. At a stable discharge rate, as the passage narrows, the pressure between the catalyst layer and the ammonia injection grid will increase. At this time, the gas will squeeze the piston, causing the piston to move downward. The downward movement of the piston will cause the scraper to move downward, and the downward movement of the scraper will cause the through-hole to scrape the catalyst rods. When the impurities on the catalyst rods are scraped off, the passage space at the catalyst layer returns to normal, and the piston will reset under the action of the spring, and the scraper will also reset. This mechanism can automatically clean the catalyst rods when too many impurities adhere to the catalyst, eliminating the need for shutdown for cleaning and improving the efficiency.

[0013] Further, it also includes a ferromagnetic substance which is fixedly connected to the flue gas passage. The piston is a magnet and is matched with the ferromagnetic substance.

[0014] When no impurities adhere to the catalyst rods, the piston contacts and adsorbs the ferromagnetic substance. The contact and adsorption between the piston and the ferromagnetic substance play a role of storing energy. Only when the set value is reached will the piston separate from the ferromagnetic substance. At this time, the piston will move downward at a relatively fast speed, causing the scraper to move downward at a relatively fast speed, making it easier for the scraper to scrape off the impurities on the catalyst rods. Description of the Drawings

[0015] Figure 1 It is a schematic diagram of a device for treating nitrogen oxides in boiler tail gas emissions.

[0016] Figure 2 It is a structural diagram of the catalyst layer of a device for treating nitrogen oxides in boiler tail gas emissions.

[0017] The figure marks in the specification include: 1. burner; 2. screen superheater; 3. high-temperature superheater; 4. low-temperature superheater; 5. economizer; 6. detector; 7. flue gas channel; 8. flue gas guide plate; 9. air preheater; 10. catalyst layer; 11. automatic regulating valve; 12. ferromagnetic material; 13. piston; 14. scraper; 15. blocking channel; 16. spring. DETAILED DESCRIPTION

[0018] As the country's environmental protection requirements continue to increase, the nitrogen oxide content in the final exhaust gas of the boiler should be less than 50 mg / Nm 3 . For this reason, most of the boilers currently in operation in China have undergone low-nitrogen combustion transformation. The boiler in our factory is a CG-480 / 9.81-M high-temperature, high-pressure pulverized coal boiler. The boiler is a single-drum boiler with natural circulation, centralized downcomers, inverted U-shaped solid slag discharge, four-corner tangential combustion, balanced ventilation, all-steel frame, full suspension structure, ∏-shaped layout, and pulverized coal furnace. The boiler denitrification device adopts selective catalytic reduction (SCR), adopts hot section / high dust content layout, and the high-temperature flue gas enters the denitrification catalyst layer 10 through the AB side flue. The number of catalyst layers 10 is arranged as 2+1. The denitrification reducing agent is heated by liquid ammonia into ammonia gas; ammonia gas is used for reduction. Under the conditions of burning the designed coal type and the verified coal type, the maximum boiler operating condition (BMCR), treating 100% of the flue gas volume, and the NOX concentration at the inlet of the denitrification system is 300mg / wm3, the denitrification efficiency is not less than 80%. After ammonia is sent from the desulfurized liquid ammonia evaporator to the furnace side, it is mixed with the dilution air provided by the dilution fan, and then sent to the catalyst layer 10 for reaction through 8 groups of 40 branch pipes on the upper and lower layers on the AB side. Since there are only 8 groups of manual valves on each of the 40 branch pipes on both sides of AB, and only one nitrogen oxide measurement point is arranged at the SCR outlet under the wide cross-sectional area of ​​the flue, the overall flue has an increase in the overall ammonia injection amount due to measurement limitations and the roughness of the branch pipe to control the ammonia amount. Excessive ammonia injection will eventually cause an increase in the residual ammonia amount at the outlet, excessive local ammonia concentration, excessive ammonia escape, and increase the risk of air preheater blockage, which is not conducive to the long-term safe, stable and efficient operation of the equipment.

[0019] Basically as attached Figure 1 As shown:

[0020] The present invention provides a boiler tail gas emission nitrogen oxide treatment device, comprising a flue gas channel 7, a superheater, an economizer 5, a flue gas guide plate 8, an ammonia injection grid, a catalyst layer 10, an air preheater 9, a detector 6 and a cleaning mechanism.

[0021] The overall structure is described with the intake at the front and the outlet at the rear. The flue gas generated after the combustion of burner 1 will flow into the flue gas passage 7. The superheater is arranged inside the flue gas passage 7; the economizer 5 is arranged behind the superheater; the flue gas deflector 8 is arranged behind the economizer 5, and the flue gas deflector 8 is used to make the flue gas distribution uniform; the ammonia injection grid is arranged behind the flue gas deflector 8; the catalyst layer 10 is arranged behind the ammonia injection grid; there are 4 ammonia injection grids, which are evenly distributed in the flue gas passage 7, and there are 4 automatic regulating valves 11 on the ammonia injection grid. The detector 6 is used to detect the content of nitrogen oxides, and the detector 6 is electrically connected to the automatic regulating valve 11. The air preheater 9 is arranged at the end of the flue gas passage 7. The air preheater 9 conducts the final waste heat recovery on the finally discharged flue gas. The flue gas releases part of its heat in the air preheater, resulting in a decrease in its temperature, thereby reducing the heat loss of flue gas discharge and improving the overall thermal efficiency of the boiler.

[0022] The superheater includes a platen superheater 2, a high-temperature superheater 3, and a low-temperature superheater 4. The platen superheater 2, the high-temperature superheater 3, and the low-temperature superheater 4 are arranged in sequence in the flue gas passage 7. The staged heating reduces the thermal stress of a single superheater, reduces the risks of high-temperature corrosion and thermal fatigue, and prolongs the service life of the equipment. Through the staged superheater, the superheat degree of steam can be precisely controlled to ensure that the steam has stable temperature and pressure before entering the steam turbine, and avoid the damage of wet steam to the steam turbine blades.

[0023] Aiming at the problems that occur in the existing SCR denitration technology during the operation of the boiler, this technology adds a flue gas diversion device inside the original flue to ensure that the flue gas generated by the boiler combustion is evenly distributed before entering the ammonia injection grid; before entering the ammonia injection grid, according to the flue gas distribution, nitrogen oxide inlet measuring points are added to increase the cyclic sampling function. At the same time, all manual valves of the ammonia injection grid are replaced with automatic regulating valves to achieve precise control of the ammonia quantity, and outlet nitrogen oxide measuring points and ammonia slip measuring points are added at the SCR outlet; according to the SCR inlet grid-type ammonia injection grid and ammonia-smoke zoning mixing: based on the results of flow field simulation and optimization, while paying attention to the uneven flow field distribution problems in both the flue width and depth directions for reasonable zoning, the positions of ammonia nozzles are optimized for independent automatic control adjustment; measure the distribution of nitrogen oxide concentrations in different regions, and through the regulating valves of ammonia injection branch pipes in different regions, automatically adjust the ammonia injection quantity in the corresponding regions, so that the flue gas and ammonia injection quantity in different regions are mixed in equal proportion, thereby making the NOX flow field distribution at the denitration outlet more uniform and achieving precise ammonia injection. Increase the service life of the catalyst and the rotary air preheater 9, and then the boiler can also achieve long-term operation, achieving the effect of energy conservation and consumption reduction.

[0024] Basically as shown in the appendix Figure 2 shown:

[0025] The cleaning mechanism includes a scraper 14, a spring 16, a piston 13 and a blocking channel 15. The scraper 14 is provided with a through hole, which is slightly larger than the catalyst rod so that the catalyst rod can pass through the through hole. However, when impurities adhere to the catalyst, the impurities on the catalyst will be scraped off when the catalyst moves through the hole. The blocking channel 15 is connected to the flue gas channel 7. The piston 13 is slidably connected to the blocking channel 15. The scraper 14 is fixedly connected to the piston 13. The blocking channel 15 is arranged between the catalyst layer 10 and the ammonia injection grid. One end of the spring 16 is fixedly connected to the piston 13, and the other end is fixedly connected to the blocking channel 15. It also includes a ferromagnetic substance 12, which is fixedly connected to the flue gas channel 7. The ferromagnetic substance 12 is fixed at the connection between the flue gas channel 7 and the blocking channel 15. The piston 13 is a magnet. The piston 13 contacts the ferromagnetic substance 12 when no impurities adhere to the catalyst rod. When there are no impurities adhering to the catalyst rod, the piston 13 contacts and adsorbs the ferromagnetic material 12, and the contact and adsorption of the piston 13 and the ferromagnetic material 12 play a role of storing force. Only when the set value is reached, the piston 13 will separate from the ferromagnetic material 12. At this time, the piston 13 will move downward at a faster speed, so that the scraper 14 moves downward faster, making it easier for the scraper 14 to scrape off the impurities on the catalyst rod.

[0026] Basically as attached Figure 1 , Figure 2 As shown:

[0027] The principle of this scheme is that the flue gas generated by the boiler will enter the flue gas channel 7, and the flue gas will first pass through the screen superheater 2, the high-temperature superheater 3 and the low-temperature superheater 4, and use the flue gas waste heat to reheat the saturated steam in the superheater to convert it into superheated steam. Compared with saturated steam, superheated steam has a higher temperature and lower density. The graded heating reduces the thermal stress of a single superheater, reduces the risk of high-temperature corrosion and thermal fatigue, and extends the service life of the equipment. Then the flue gas will pass through the economizer 5, and the flue gas waste heat will be used again to heat the boiler feed water in the economizer 5, reducing the amount of fuel required to heat the feed water after entering the boiler, thereby saving fuel and improving energy utilization. Then the flue gas with lowered temperature will pass through the flue gas guide plate 8, so that the flue gas is evenly distributed in the flue gas channel 7, and then the flue gas will contact the detector 6, which can detect the content of nitrogen oxides in the flue gas. Then, the controller in the nitrogen oxide content detector 6 will adjust the size of the automatic regulating valve 11, so that when the flue gas passes through the ammonia spraying grid, the amount of ammonia sprayed by the ammonia spraying grid is appropriate. Finally, the mixed gas reacts through the catalyst layer 10 to neutralize the nitrogen oxides in the flue gas. The air preheater 9 recovers the final waste heat of the flue gas discharged last. The flue gas releases part of the heat in the air preheater, causing its temperature to drop, thereby reducing the heat loss of flue gas and improving the overall thermal efficiency of the boiler. The treatment of nitrogen oxides is completed.

[0028] When too much impurity adheres to the catalyst rod, the passage space at the catalyst layer 10 will become narrower. At a stable displacement, the narrowing of the passage will cause the pressure between the catalyst layer 10 and the ammonia injection grid to increase. At this time, the gas will squeeze the piston 13, causing the piston 13 to move downward. The downward movement of the piston 13 will cause the scraper 14 to move downward, and the downward movement of the scraper 14 will cause the through hole to scrape the catalyst rod. After the impurities on the catalyst rod are scraped off, the passage space at the catalyst layer 10 returns to normal, and the piston 13 will reset under the action of the spring 16, and the scraper 14 will also reset.

[0029] The beneficial effects of this solution are as follows: 1. The flue gas is cooled in this solution before detection to prevent the high-temperature flue gas from damaging the detector 6. 2. This solution can automatically adjust the ammonia dosage to prevent excessive dosage, which may not fully react with NOx and will be discharged into the atmosphere in the form of NH3, causing air pollution. 3. This mechanism can automatically clean the catalyst rod when too much impurity adheres to the catalyst, without the need to stop work for cleaning, improving the efficiency.

[0030] The above are only the embodiments of the present invention. Common knowledge such as specific structures and characteristics known in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can still be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be subject to the content of its claims, and the specific implementation manners and the like described in the specification can be used to interpret the content of the claims.

Claims

1. A boiler tail gas emission nitrogen oxide treatment device, comprising: Smoke channel (7); Superheater: The superheater is arranged in the flue gas channel (7); Economizer (5): The economizer (5) is arranged after the superheater; Flue gas guide plate (8): the flue gas guide plate (8) is arranged behind the economizer (5), and the flue gas guide plate (8) is used to make the flue gas evenly distributed; Ammonia injection grid: the ammonia injection grid is arranged behind the flue gas guide plate (8); Catalyst layer (10): the catalyst layer (10) is arranged behind the ammonia injection grid; It is characterized in that There are a plurality of ammonia injection grids, which are evenly distributed in the flue gas channel (7), and an automatic regulating valve (11) is provided on the ammonia injection grid. Also includes: Detector (6): The detector (6) is used to detect the content of nitrogen oxides, and the detector (6) is electrically connected to the automatic regulating valve (11).

2. A boiler tail gas emission nitrogen oxide treatment device according to claim 1, characterized in that: The superheater comprises a platen superheater (2), a high-temperature superheater (3) and a low-temperature superheater (4); the platen superheater (2), the high-temperature superheater (3) and the low-temperature superheater (4) are arranged in sequence in the flue gas channel (7).

3. The boiler tail gas emission nitrogen oxide treatment device according to claim 1, characterized in that: It also includes an air preheater (9), which is arranged at the end of the flue gas channel (7).

4. A boiler tail gas emission nitrogen oxide treatment device according to claim 1, characterized in that: The invention also comprises a cleaning mechanism, which comprises a scraper (14), a spring (16), a piston (13) and a blocking channel (15); the scraper (14) is provided with a through hole, the through hole cooperates with the catalyst layer (10); the blocking channel (15) is communicated with the flue gas channel (7); the piston (13) is slidably connected to the blocking channel (15); the scraper (14) is fixedly connected to the piston (13); the blocking channel (15) is arranged between the catalyst layer (10) and the ammonia injection grid; one end of the spring (16) is fixedly connected to the piston (13), and the other end is fixedly connected to the blocking channel (15).

5. A boiler tail gas emission nitrogen oxide treatment device according to claim 4, characterized in that: It also includes a ferromagnetic substance (12), the ferromagnetic substance (12) is fixedly connected to the smoke channel (7), and the piston (13) is a magnet, and the piston (13) cooperates with the ferromagnetic substance (12).

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