SCR flue gas denitration system based on ammonium carbamate

Abstract

The invention discloses an ammonium carbamate-based SCR flue gas denitration system, which comprises a storage bin, a conveying unit, a pyrolysis unit, a pressure stabilizing unit, a drying unit, a filtering unit and an SCR denitration unit, and is characterized in that the pyrolysis unit is used for pyrolyzing ammonium carbamate powder to generate mixed gas of ammonia gas and carbon dioxide; the pressure stabilizing unit is used for stabilizing the pressure of the mixed gas and cooling the mixed gas; the filtering unit is used for filtering the drying agent in the mixed gas; and the SCR denitration unit is used for receiving the mixed gas discharged by the filtering unit so as to reduce nitrogen oxide in the flue gas into nitrogen and water. According to the invention, the energy consumption is obviously reduced, the operation cost is reduced, the problem of low stability of ammonium carbamate at normal temperature is solved, and the adverse effects of moisture and dust carried by ammonia gas generated in the processes of dissolving, dehydrating, filtering and the like of ammonium carbamate on the denitration process of a catalyst in the subsequent SCR denitration unit are effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas denitrification, and particularly relates to an SCR flue gas denitrification system based on ammonium carbamate. Background Art

[0002] With the continuous improvement of China's environmental protection awareness, the problem of nitrogen oxide pollution emitted by coal-fired power plants has received wide attention. Nitrogen oxides are an important pollutant in the atmosphere and have a serious impact on human health and the ecological environment. In order to effectively control the nitrogen oxide emissions of coal-fired units, selective catalytic reduction (SCR) flue gas denitrification technology has become the preferred denitrification technology in China's power industry.

[0003] Currently, in SCR flue gas denitrification technology, urea is widely used as a denitrification reducing agent. However, the process of ammonia production from urea requires high-temperature conditions, resulting in high energy consumption costs. In addition, there are a series of problems in the storage, transportation, and dissolution of urea, such as low thermal stability, metal corrosion, and poor adaptability to existing processes.

[0004] In view of these problems, the present invention patent proposes an SCR flue gas denitrification system based on ammonium carbamate. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to some extent.

[0006] To this end, an embodiment of the present invention provides an SCR flue gas denitrification system based on ammonium carbamate.

[0007] The SCR flue gas denitrification system based on ammonium carbamate according to the embodiment of the present invention includes a storage bin, a conveying unit, a pyrolysis unit, a pressure stabilizing unit, a drying unit, a filtering unit, and an SCR denitrification unit. The storage bin is used for storing ammonium carbamate powder; the conveying unit is communicated with the storage bin and is used for conveying the ammonium carbamate powder discharged from the storage bin; the pyrolysis unit is communicated with the conveying unit and is used for pyrolyzing the ammonium carbamate powder conveyed by the conveying unit to generate a mixture of ammonia and carbon dioxide; the pressure stabilizing unit is communicated with the pyrolysis unit and is used for stabilizing the pressure and cooling the mixture discharged from the pyrolysis unit; the drying unit is communicated with the pressure stabilizing unit and is used for drying the mixture of stabilized pressure and cooled discharged from the pressure stabilizing unit; the filtering unit is communicated with the drying unit and is used for filtering the desiccant in the mixture discharged from the drying unit; the SCR denitrification unit is communicated with the filtering unit and is used for receiving the mixture discharged from the filtering unit to reduce nitrogen oxides in the flue gas to nitrogen and water.

[0008] In some embodiments, the storage bin includes a primary bin, a secondary bin, and a feeder. The primary bin is in communication with the secondary bin. The primary bin is configured to convey ammonium carbamate powder into the secondary bin according to the storage height of the secondary bin. The feeder is disposed at the discharge port of the secondary bin and is in communication with the conveying unit. A drying groove for storing a first desiccant is provided on the inner wall of at least one of the primary bin and the secondary bin. The first desiccant is used to dry the ammonium carbamate powder.

[0009] In some embodiments, the conveying unit includes a material conveying pipe and a gas conveying pipe. The first end of the material conveying pipe is in communication with the feeder. The second end of the material conveying pipe is in communication with the pyrolysis unit. The gas conveying pipe is in communication with the material conveying pipe for conveying low-pressure hot air into the material conveying pipe to carry the ammonium carbamate powder in the material conveying pipe into the pyrolysis unit. The temperature of the low-pressure hot air is 80°C - 120°C, and the pressure is 0.05 MPa - 0.2 MPa.

[0010] In some embodiments, the pyrolysis unit includes a pyrolysis tower and a reboiler. The pyrolysis tower has a water inlet and a mixed gas outlet. The reboiler is disposed at the bottom of the pyrolysis tower and is configured to heat the water entering the pyrolysis tower to 100°C - 150°C. The second end of the material conveying pipe extends vertically into the pyrolysis tower from the top of the pyrolysis tower and is located above the hot water. A part of the ammonium carbamate powder is heat-exchanged and pyrolyzed in the space above the hot water in the pyrolysis tower, and another part of the ammonium carbamate powder falls into the hot water at the bottom of the pyrolysis tower and is heat-exchanged and pyrolyzed with the hot water. The mixed gas outlet is used to discharge the mixed gas of ammonia and carbon dioxide generated by pyrolysis.

[0011] In some embodiments, the second end of the material conveying pipe has a flared portion. The cross-sectional area of the flared portion gradually increases in the discharge direction. The flare angle of the flared portion is 80° - 120°.

[0012] In some embodiments, the side wall of the pyrolysis tower has a hot water inlet near the top of the pyrolysis tower and a hot water outlet near the bottom of the pyrolysis tower. The hot water inlet and the hot water outlet are connected by a circulation pump to circulate the hot water at the bottom of the pyrolysis tower between the hot water inlet and the hot water outlet. The hot water entering the pyrolysis tower through the hot water inlet flows down along the inner wall of the pyrolysis tower to the bottom of the pyrolysis tower.

[0013] In some embodiments, the voltage stabilizing unit includes a buffer tank and a steam trap. The buffer tank has a first air inlet, a first air outlet, and a liquid discharge port. The first air inlet is communicated with the mixed gas outlet to stabilize the pressure and cool the mixed gas discharged from the mixed gas outlet to 20°C - 30°C. The steam trap is arranged at the liquid discharge port and is used for discharging the condensed water generated by the cooling of the mixed gas. The first air outlet is communicated with the drying unit to convey the mixed gas with stabilized pressure and reduced temperature to the drying unit.

[0014] In some embodiments, the drying unit includes a drying tower. A plurality of baffle plates are arranged on the inner wall of the drying tower at intervals along its height direction. The baffle plates are arranged obliquely downward. The plurality of baffle plates define a serpentine channel. The drying tower has a second air inlet, a second desiccant inlet communicated with the channel inlet of the serpentine channel, a second air outlet, and a second desiccant outlet communicated with the channel outlet of the serpentine channel. The second air inlet is communicated with the first air outlet, and the second air outlet is communicated with the filtering unit. The second desiccant inlet is used for the second desiccant to enter the drying tower and flow through the serpentine channel simultaneously with the mixed gas to dry the mixed gas.

[0015] In some embodiments, the filtering unit includes multiple layers of filter cartridges arranged in the inner and outer directions. The plurality of filter cartridges include at least one of a film-coated filter cartridge and a polyester filter cartridge.

[0016] In some embodiments, the SCR denitration unit includes a reactor and a plurality of catalyst beds. The plurality of catalyst beds are arranged in the reactor at intervals along the height direction of the reactor. The ratio of the distance between two adjacent catalyst beds to the diameter of the reactor is 5 - 10.

[0017] The SCR flue gas denitration system based on ammonium carbamate according to the embodiments of the present invention uses ammonium carbamate as the main denitration agent component. From a process perspective, it not only solves the problem of low ambient temperature stability of ammonium carbamate, but also effectively reduces the adverse effects of ammonia carrying moisture and dust generated during the processes of dissolution, dehydration, and filtration of ammonium carbamate on the denitration process of the catalyst in the subsequent SCR denitration unit. Compared with ammonia production from urea, the ammonia production efficiency of ammonium carbamate denitration agent by water dissolution is higher than that of ammonia production from urea. After calculation, under full load conditions, the ammonia production efficiency of ammonium carbamate denitration agent is 6.6 - 21.2% higher than that of urea, with an average increase of about 13.9%. The energy consumption for ammonia production from the new denitration agent solution is reduced by 53.8 - 61.6%. Description of the Drawings

[0018] Figure 1 is a schematic flow chart of the SCR flue gas denitration system according to the embodiments of the present invention.

[0019] Figure 2It is a schematic structural diagram of the SCR flue gas denitrification system according to an embodiment of the present invention.

[0020] Reference numerals: 100, SCR flue gas denitrification system based on ammonium carbamate; 1, storage bin; 101, primary bin; 102, secondary bin; 103, feeder; 2, conveying unit; 201, conveying pipe; 2011, flared portion; 202, gas conveying pipe; 3, pyrolysis unit; 301, pyrolysis tower; 3011, water inlet; 3012, mixed gas outlet; 3013, hot water inlet; 302, reboiler; 4, pressure stabilizing unit; 401, buffer tank; 4011, first air inlet; 4012, first air outlet; 4013, liquid discharge port; 402, steam trap; 5, drying unit; 501, drying tower; 502, baffle; 503, serpentine channel; 504, second air inlet; 505, second desiccant inlet; 506, second air outlet; 507, second desiccant outlet; 6, filtering unit; 7, SCR denitrification unit; 701, reactor. Detailed implementation manners

[0021] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as a limitation to the present invention.

[0022] As Figure 1 and Figure 2 shown, the SCR flue gas denitrification system 100 based on ammonium carbamate according to an embodiment of the present invention includes a storage bin 1, a conveying unit 2, a pyrolysis unit 3, a pressure stabilizing unit 4, a drying unit 5, a filtering unit 6 and an SCR denitrification unit 7. The storage bin 1 is used for storing ammonium carbamate powder. The conveying unit 2 is connected to the storage bin 1 and is used for conveying the ammonium carbamate powder discharged from the storage bin 1. The pyrolysis unit 3 is connected to the conveying unit 2 and is used for pyrolyzing the ammonium carbamate powder conveyed by the conveying unit 2 to generate a mixed gas of ammonia and carbon dioxide. The pressure stabilizing unit 4 is connected to the pyrolysis unit 3 and is used for stabilizing the pressure and reducing the temperature of the mixed gas discharged from the pyrolysis unit 3. The drying unit 5 is connected to the pressure stabilizing unit 4 and is used for drying the mixed gas after pressure stabilizing and temperature reducing discharged from the pressure stabilizing unit 4. The filtering unit 6 is connected to the drying unit 5 and is used for filtering the desiccant in the mixed gas discharged from the drying unit 5. The SCR denitrification unit 7 is connected to the filtering unit 6 and is used for receiving the mixed gas discharged from the filtering unit 6 to reduce nitrogen oxides in the flue gas to nitrogen and water.

[0023] When the SCR flue gas denitrification system 100 based on ammonium carbamate according to an embodiment of the present invention is in use, ammonium carbamate is heated and decomposed in the pyrolysis unit 3 to generate a mixed gas of ammonia and carbon dioxide. Since the pyrolysis temperature of ammonium carbamate is relatively low, compared with the ammonia production process using urea, the energy consumption can be significantly reduced and the operation cost can be reduced.

[0024] The generated mixed gas undergoes pressure stabilization and cooling treatment through the pressure stabilization unit 4 to ensure that the mixed gas reaches an appropriate pressure and temperature before entering the SCR denitration unit 7, avoiding damage to the SCR catalyst. The mixed gas undergoes drying treatment in the drying unit 5 to remove the moisture therein to prevent the generation of liquid water during the SCR reaction process, which may affect the denitration efficiency. The filtering unit 6 is used to remove particulate matters such as desiccants from the mixed gas to prevent these particulate matters from entering the SCR denitration unit 7 and affecting the activity and lifespan of the catalyst. The filtered mixed gas is sent into the SCR denitration unit 7, where ammonia as a reducing agent undergoes a chemical reaction with nitrogen oxides in the flue gas under the action of the catalyst to reduce the nitrogen oxides to harmless nitrogen and water.

[0025] Thus, the SCR flue gas denitration system 100 based on ammonium carbamate according to the embodiments of the present invention uses ammonium carbamate as the main denitration agent component. From a process perspective, it not only solves the problem of low ambient temperature stability of ammonium carbamate, but also effectively reduces the adverse effects of the ammonia carrying moisture and dust generated during the processes of dissolution, dehydration, and filtration of ammonium carbamate on the denitration process of the catalyst in the subsequent SCR denitration unit 7. Compared with ammonia production from urea, the ammonia production efficiency of the ammonium carbamate denitration agent by water dissolution is higher than that of ammonia production from urea. Through calculation, under full load conditions, the ammonia production efficiency of the ammonium carbamate denitration agent is increased by 6.6 - 21.2% compared with urea, with an average increase of about 13.9%, and the energy consumption for ammonia production from the new denitration agent solution is reduced by 53.8 - 61.6%.

[0026] In some embodiments, the storage bin 1 includes a primary bin 101, a secondary bin 102, and a feeder 103. The primary bin 101 is communicated with the secondary bin 102. The primary bin 101 is used to convey ammonium carbamate powder into the secondary bin 102 according to the storage height of the secondary bin 102. The feeder 103 is arranged at the discharge port of the secondary bin 102 and is communicated with the conveying unit 2. A drying tank for storing a first desiccant is provided on the inner wall of at least one of the primary bin 101 and the secondary bin 102, and the first desiccant is used to dry the ammonium carbamate powder.

[0027] As Figure 2As shown, the primary bin 101 serves as the main storage area for storing a large amount of ammonium carbamate powder. When the storage height of the ammonium carbamate powder in the secondary bin 102 decreases to a certain extent, the primary bin 101 will automatically convey the powder to the secondary bin 102 to ensure the continuous operation of the denitration system. The feeder 103 is located at the discharge port of the secondary bin 102 and is connected to the conveying unit 2. It is responsible for uniformly and continuously conveying the ammonium carbamate powder from the secondary bin 102 to the pyrolysis unit 3 to ensure the stable progress of the denitration process. A drying tank is provided on the inner wall of the primary bin 101 and / or the secondary bin 102, and a first desiccant is stored in the drying tank. The function of the desiccant is to absorb the moisture in the ammonium carbamate powder, prevent the powder from absorbing moisture and caking during storage, and ensure its fluidity and conveying efficiency. The dried ammonium carbamate powder has a higher pyrolysis efficiency in the pyrolysis unit 3, and the generated ammonia mixture gas has better quality, which is beneficial to more effectively reducing nitrogen oxides in the SCR denitration unit 7.

[0028] In some embodiments, the conveying unit 2 includes a feed pipe 201 and an air supply pipe 202. The first end of the feed pipe 201 is communicated with the feeder 103, the second end of the feed pipe 201 is communicated with the pyrolysis unit 3, and the air supply pipe 202 is communicated with the feed pipe 201 for conveying low-pressure hot air into the feed pipe 201 to carry the ammonium carbamate powder in the feed pipe 201 into the pyrolysis unit 3. The temperature of the low-pressure hot air is 80°C - 120°C, and the pressure is 0.05MPa - 0.2MPa.

[0029] The low-pressure hot air conveyed by the air supply pipe 202 not only carries the ammonium carbamate powder but also provides the necessary heat for the pyrolysis unit 3. The temperature of the low-pressure hot air is controlled at 80°C - 120°C, and the pressure is 0.05MPa - 0.2MPa. Such a temperature and pressure range can ensure that the ammonium carbamate powder is not overheated and decomposed during transportation, and can also be smoothly conveyed to the pyrolysis unit 3.

[0030] Through the carrying action of the low-pressure hot air, the ammonium carbamate powder can be efficiently conveyed through the feed pipe 201 to the pyrolysis unit 3, reducing the loss of materials during transportation. The temperature and pressure of the hot air used during transportation are precisely controlled, which helps to maintain suitable reaction conditions in the pyrolysis unit 3, thus ensuring that the ammonium carbamate powder can be fully pyrolyzed. Since the pressure and temperature of the hot air are relatively low, compared with traditional compressed air transportation, this method can reduce energy consumption.

[0031] In some embodiments, the pyrolysis unit 3 includes a pyrolysis tower 301 and a reboiler 302. The pyrolysis tower 301 has a water inlet 3011 and a mixed gas outlet 3012. The reboiler 302 is provided at the bottom of the pyrolysis tower 301 and is used to heat the water entering the pyrolysis tower 301 to 100°C - 150°C. The second end of the feed pipe 201 extends vertically into the pyrolysis tower 301 from the top of the pyrolysis tower 301 and is located above the hot water. A part of the ammonium carbamate powder is pyrolyzed by heat exchange in the space above the hot water in the pyrolysis tower 301, and another part of the ammonium carbamate powder falls into the hot water at the bottom of the pyrolysis tower 301 and is pyrolyzed by heat exchange with the hot water. The mixed gas outlet 3012 is used to discharge the mixed gas of ammonia and carbon dioxide generated by pyrolysis.

[0032] The pyrolysis tower 301 is the core equipment in the pyrolysis process. The water inlet 3011 is used to inject water into the pyrolysis tower 301, and the mixed gas outlet 3012 is used to discharge the mixed gas of ammonia and carbon dioxide generated by pyrolysis. The reboiler 302 is located at the bottom of the pyrolysis tower 301, and its main function is to heat the water entering the pyrolysis tower 301 to make its temperature reach 100°C - 150°C. This temperature range can promote the pyrolysis reaction of ammonium carbamate. The second end of the feed pipe 201 extends into the tower from the top of the pyrolysis tower 301 and is located above the hot water. Such an arrangement allows the ammonium carbamate powder to be pyrolyzed in two ways in the pyrolysis tower 301. A part of the ammonium carbamate powder is pyrolyzed by indirect heat exchange with hot air in the space above the hot water. Another part of the ammonium carbamate powder falls into the hot water and is pyrolyzed by direct heat exchange with the hot water.

[0033] Through the two ways of indirect heat exchange with hot water and direct heat exchange with hot water in the pyrolysis tower 301, the ammonium carbamate powder can be pyrolyzed under different conditions, which helps to improve the pyrolysis efficiency. The reboiler 302 heats the water to an appropriate temperature, making the pyrolysis process more complete and improving the utilization efficiency of thermal energy at the same time. The setting of the pyrolysis tower 301 makes the pyrolysis process more controllable, and the pyrolysis reaction conditions can be controlled by adjusting the water inflow and the hot water temperature. By controlling the pyrolysis conditions, unnecessary side reactions can be reduced, and the purity of ammonia and carbon dioxide in the mixed gas can be guaranteed. The setting of the pyrolysis tower 301 and the reboiler 302 can improve the utilization efficiency of thermal energy and reduce the energy consumption of the entire denitration system.

[0034] In some embodiments, the second end of the feed pipe 201 has a flared portion 2011, and the cross-sectional area of the flared portion 2011 gradually increases along the discharging direction, wherein the flare angle of the flared portion 2011 is 80° - 120°.

[0035] The flaring angle of the flared portion 2011 is usually designed to be between 80° and 120°. This angle range can provide sufficient space for the ammonium carbamate powder to smoothly flow out of the feed pipe 201 and diffuse in the pyrolysis tower 301, facilitating the increase of the heat exchange area between the ammonium carbamate powder and the hot air in the pyrolysis tower 301, thereby improving the heat exchange efficiency and accelerating pyrolysis.

[0036] In some embodiments, the side wall of the pyrolysis tower 301 has a hot water inlet 3013 near the top of the pyrolysis tower 301 and a hot water outlet (not shown in the figure) near the bottom of the pyrolysis tower 301. The hot water inlet 3013 and the hot water outlet are connected by a circulation pump so that the hot water at the bottom of the pyrolysis tower 301 circulates between the hot water inlet 3013 and the hot water outlet. The hot water entering the pyrolysis tower 301 through the hot water inlet 3013 flows down along the inner wall of the pyrolysis tower 301 to the bottom of the pyrolysis tower 301.

[0037] It can be understood that during the pyrolysis process of the ammonium carbamate powder in the pyrolysis tower 301, it is easy to adsorb and adhere to the inner wall of the pyrolysis tower 301. If not cleaned in time during the pyrolysis process, it may affect the pyrolysis efficiency and the operation of the equipment.

[0038] Therefore, a hot water inlet 3013 and a hot water outlet are provided on the side wall of the pyrolysis tower 301. These two interfaces are connected by a circulation pump to form a hot water circulation system. Hot water enters the pyrolysis tower 301 from the inlet and flows down along the inner wall of the tower to the bottom of the tower. During this process, the hot water contacts the ammonium carbamate powder adhered and adsorbed on the inner wall of the pyrolysis tower 301, transfers heat, and takes away the ammonium carbamate powder accumulated on the inner wall of the tower. Reducing the accumulation of scale and keeping the inner wall of the tower clean is beneficial to the long-term stable operation of the equipment.

[0039] In addition, the hot water circulation system can ensure a more uniform temperature distribution in the pyrolysis tower 301, which helps to improve the pyrolysis efficiency of the ammonium carbamate powder. Through hot water circulation, heat energy can be more effectively utilized, reducing heat energy loss.

[0040] In some embodiments, the pressure stabilizing unit 4 includes a buffer tank 401 and a steam trap 402. The buffer tank 401 has a first air inlet 4011, a first air outlet 4012, and a drain port 4013. The first air inlet 4011 is connected to the mixed gas outlet 3012 to stabilize the pressure and cool the mixed gas discharged from the mixed gas outlet 3012 to 20°C - 30°C. The steam trap 402 is provided at the drain port 4013 for discharging the condensed water generated by cooling the mixed gas. The first air outlet 4012 is connected to the drying unit 5 to convey the mixed gas with stabilized pressure and reduced temperature to the drying unit 5.

[0041] Such as Figure 2As shown, the buffer tank 401 is the core component of the voltage stabilizing unit 4. It has a first air inlet 4011, a first air outlet 4012, and a liquid drain port 4013. The first air inlet 4011 is communicated with the mixed gas outlet 3012 and is used to receive the mixed gas discharged from the pyrolysis unit 3. After the mixed gas enters the buffer tank 401, due to the relatively large volume of the buffer tank 401, it can play a role in stabilizing the pressure, so that the pressure of the mixed gas remains stable. At the same time, the temperature of the mixed gas can be reduced to 20°C - 30°C in the buffer tank 401 through a heat exchange device or natural cooling. A steam trap 402 is provided at the liquid drain port 4013 and is used to discharge the condensed water generated during the temperature reduction of the mixed gas. This can prevent the influence of the condensed water on the subsequent treatment unit and ensure that the mixed gas received by the drying unit 5 is dry. The first air outlet 4012 is communicated with the drying unit 5 and is used to convey the mixed gas after pressure stabilization and temperature reduction to the drying unit 5 for further drying treatment.

[0042] The pressure stabilizing function of the buffer tank 401 helps to ensure the stability of the pressure of the mixed gas during transportation, which is very important for subsequent drying and denitrification treatments. Through the temperature reduction treatment, the temperature of the mixed gas can be reduced, the energy loss of the mixed gas during transportation can be reduced, and it is also beneficial to the subsequent drying treatment. The setting of the steam trap 402 can timely discharge the condensed water, prevent the influence of the condensed water on the drying unit 5 and the SCR denitrification unit 7, and ensure the normal operation of the system. The mixed gas after pressure stabilization and temperature reduction is partially dried when it enters the drying unit 5, which can improve the working efficiency of the drying unit 5 and reduce the consumption of desiccant. Through pressure stabilization and temperature reduction treatments, the quality of the mixed gas can be improved, which helps to more effectively reduce nitrogen oxides in the SCR denitrification unit 7. By reducing the influence of condensed water and optimizing the treatment of the mixed gas, the maintenance frequency of the equipment can be reduced, thereby reducing the maintenance cost.

[0043] In some embodiments, the drying unit 5 includes a drying tower 501. A plurality of baffle plates 502 are arranged on the inner wall of the drying tower 501 at intervals along its height direction. The baffle plates 502 are arranged obliquely downward, and the plurality of baffle plates 502 define a serpentine channel 503. The drying tower 501 has a second air inlet 504 and a second desiccant inlet 505 communicated with the channel inlet of the serpentine channel 503, and a second air outlet 506 and a second desiccant outlet 507 communicated with the channel outlet of the serpentine channel 503. The second air inlet 504 is communicated with the first air outlet 4012, and the second air outlet 506 is communicated with the filtering unit 6. The second desiccant inlet 505 is used for the second desiccant to enter the drying tower 501 and flow through the serpentine channel 503 simultaneously with the mixed gas to dry the mixed gas.

[0044] As Figure 2As shown, through the setting of the serpentine channel 503, the desiccant can be evenly contacted with the mixed gas during the entire drying process, thereby improving the utilization efficiency of the desiccant. The mixed gas and the second desiccant flow in the serpentine channel 503. Through multiple back-and-forth flows, the contact area and time between the mixed gas and the desiccant are increased, thereby improving the drying effect. The moisture content in the dried mixed gas is reduced, which helps to improve the quality of the mixed gas and reduce the impact on the subsequent SCR denitration unit 7.

[0045] In some embodiments, the filtering unit 6 includes multiple filter cartridges arranged in the inner-outer direction, and the multiple filter cartridges include at least one of a membrane filter cartridge and a polyester filter cartridge.

[0046] The membrane filter cartridge has a microporous film of PTFE or other materials and can efficiently filter fine particulate matter. The polyester filter cartridge has excellent filtering performance and chemical corrosion resistance. The mixed gas first passes through the outer layer of filter cartridges to remove larger particulate matter, and then sequentially passes through the inner layer of filter cartridges to further purify the mixed gas, ensuring that the particulate matter content in the finally output mixed gas meets the requirements of the SCR denitration unit 7. The design of the multiple filter cartridges can gradually filter impurities and particulate matter in the mixed gas, improving the filtering efficiency and effect. Since the outer layer of filter cartridges first filters out larger particulate matter, the inner layer of filter cartridges (such as the membrane filter cartridge) bears relatively less pressure and pollution, which helps to extend the service life of the filter cartridges. Through multiple-layer filtering, the quality of the mixed gas can be significantly improved, reducing the pollution of the catalyst in the SCR denitration unit 7 and ensuring its efficient operation. The particulate matter content in the filtered mixed gas is relatively low, which can reduce the blockage and wear of the catalyst in the SCR denitration unit 7, thereby reducing the maintenance cost and downtime. High-quality mixed gas can improve the denitration effect of the SCR denitration unit 7 and reduce nitrogen oxide emissions. Through effective filtering, the stability and reliability of the entire denitration system can be improved.

[0047] In some embodiments, the SCR denitration unit 7 includes a reactor 701 and multiple catalyst beds. The multiple catalyst beds are arranged at intervals in the height direction of the reactor 701 within the reactor 701, and the ratio of the distance between two adjacent catalyst beds to the diameter of the reactor 701 is 5-10.

[0048] The layout of multiple catalyst beds increases the contact area and time between the mixed gas and the catalyst, which helps to improve the reduction efficiency of nitrogen oxides. The design of the catalyst bed spacing optimizes the hydrodynamic conditions inside the reactor 701, enabling the mixed gas to be evenly distributed inside the reactor 701, avoiding gas flow dead zones or excessive turbulence, thereby enhancing the stability of the system and the denitration efficiency. An appropriate catalyst bed spacing helps to reduce the gas flow impact between the catalyst beds and extends the service life of the catalyst. By optimizing the layout of the catalyst beds, the stability of the entire SCR denitration unit 7 can be improved, and system fluctuations caused by uneven gas flow distribution can be reduced. By increasing the nitrogen oxide reduction efficiency and improving the stability of the system, the denitration effect can be further enhanced, and nitrogen oxide emissions can be reduced. By extending the catalyst life and optimizing the system stability, the maintenance frequency and cost can be reduced.

[0049] Optionally, the catalytic denitration reaction temperature in the SCR denitration unit 7 is controlled at 300°C - 400°C.

[0050] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0051] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0052] In the present invention, unless otherwise clearly specified and defined, terms such as "mounted", "connected", "connected to", "fixed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection, an electrical connection, or communicable with each other; it can be directly connected, or indirectly connected through an intermediate medium, and can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply indicates that the horizontal height of the first feature is less than that of the second feature.

[0054] In the present invention, the terms "an embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples.

[0055] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. An SCR flue gas denitrification system based on ammonium carbamate, characterized in that, Comprising: A storage bin for storing ammonium carbamate powder; A conveying unit communicating with the storage bin for conveying the ammonium carbamate powder discharged from the storage bin; A pyrolysis unit communicating with the conveying unit for pyrolyzing the ammonium carbamate powder conveyed by the conveying unit to generate a mixture of ammonia and carbon dioxide; A pressure stabilizing unit communicating with the pyrolysis unit for stabilizing the pressure and cooling the mixture discharged from the pyrolysis unit; A drying unit communicating with the pressure stabilizing unit for drying the mixture after pressure stabilizing and cooling discharged from the pressure stabilizing unit; A filtering unit communicating with the drying unit for filtering the desiccant in the mixture discharged from the drying unit; An SCR denitration unit communicating with the filtering unit for receiving the mixture discharged from the filtering unit to reduce nitrogen oxides in the flue gas to nitrogen and water.

2. The SCR flue gas denitrification system based on ammonium carbamate according to claim 1, wherein, The storage bin includes a primary bin, a secondary bin and a feeder. The primary bin communicates with the secondary bin. The primary bin is used for conveying ammonium carbamate powder into the secondary bin according to the storage height of the secondary bin. The feeder is arranged at the discharge port of the secondary bin and communicates with the conveying unit. A drying groove for storing a first desiccant is provided on the inner wall of at least one of the primary bin and the secondary bin. The first desiccant is used for drying the ammonium carbamate powder.

3. The SCR flue gas denitrification system based on ammonium carbamate according to claim 2, wherein The conveying unit includes a feed pipe and an air pipe. The first end of the feed pipe communicates with the feeder, and the second end of the feed pipe communicates with the pyrolysis unit. The air pipe communicates with the feed pipe for conveying low-pressure hot air into the feed pipe to carry the ammonium carbamate powder in the feed pipe into the pyrolysis unit. The temperature of the low-pressure hot air is 80°C - 120°C, and the pressure is 0.05 MPa - 0.2 MPa.

4. The SCR flue gas denitrification system based on ammonium carbamate according to claim 3, characterized in that, The pyrolysis unit includes a pyrolysis tower and a reboiler. The pyrolysis tower has a water inlet and a mixture gas outlet. The reboiler is arranged at the bottom of the pyrolysis tower for heating the water entering the pyrolysis tower to 100°C - 150°C. The second end of the feed pipe extends vertically into the pyrolysis tower from the top of the pyrolysis tower and is located above the hot water. A part of the ammonium carbamate powder is pyrolyzed by heat exchange in the space above the hot water in the pyrolysis tower, and another part of the ammonium carbamate powder falls into the hot water at the bottom of the pyrolysis tower and is pyrolyzed by heat exchange with the hot water. The mixture gas outlet is used for discharging the mixture of ammonia and carbon dioxide generated by pyrolysis.

5. The SCR flue gas denitrification system based on ammonium carbamate according to claim 4, characterized in that, The second end of the feed pipe has a flared portion, and the cross-sectional area of the flared portion gradually increases along the discharge direction. The flare angle of the flared portion is 80° - 120°.

6. The SCR flue gas denitrification system based on ammonium carbamate according to claim 4, characterized in that, The side wall of the pyrolysis tower is provided with a hot water inlet near the top of the pyrolysis tower and a hot water outlet near the bottom of the pyrolysis tower. The hot water inlet and the hot water outlet are connected through a circulation pump, so that the hot water at the bottom of the pyrolysis tower circulates between the hot water inlet and the hot water outlet. The hot water entering the pyrolysis tower through the hot water inlet flows down along the inner wall of the pyrolysis tower to the bottom of the pyrolysis tower.

7. The SCR flue gas denitrification system based on ammonium carbamate according to claim 4, characterized in that, The pressure stabilizing unit includes a buffer tank and a steam trap. The buffer tank has a first air inlet, a first air outlet and a liquid discharge port. The first air inlet is connected to the mixed gas outlet to stabilize the pressure of the mixed gas discharged from the mixed gas outlet and cool it down to 20°C - 30°C. The steam trap is arranged at the liquid discharge port for discharging the condensed water generated by the cooling of the mixed gas. The first air outlet is connected to the drying unit to convey the mixed gas with stabilized pressure and cooled temperature to the drying unit.

8. The SCR flue gas denitrification system based on ammonium carbamate according to claim 7, characterized in that, The drying unit includes a drying tower. A plurality of baffle plates are arranged on the inner wall of the drying tower at intervals along its height direction. The baffle plates are arranged obliquely downward. The plurality of baffle plates define a serpentine channel. The drying tower has a second air inlet and a second desiccant inlet connected to the channel inlet of the serpentine channel, and a second air outlet and a second desiccant outlet connected to the channel outlet of the serpentine channel. The second air inlet is connected to the first air outlet, and the second air outlet is connected to the filtering unit. The second desiccant inlet is used for the second desiccant to enter the drying tower and flow through the serpentine channel simultaneously with the mixed gas to dry the mixed gas.

9. The SCR flue gas denitrification system based on ammonium carbamate according to claim 4, wherein The filtering unit includes multiple filter cartridges arranged in the inner and outer directions. The plurality of filter cartridges include at least one of a membrane filter cartridge and a polyester filter cartridge.

10. The SCR flue gas denitrification system based on ammonium carbamate according to claim 8, characterized in that, The SCR denitration unit includes a reactor and a plurality of catalyst beds. The plurality of catalyst beds are arranged in the reactor at intervals along the height direction of the reactor. The ratio of the distance between two adjacent catalyst beds to the diameter of the reactor is 5 - 10.

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