Ammonium carbamate-based scr flue gas denitration system

Abstract

The application 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; the pyrolysis unit is used for pyrolyzing ammonium carbamate powder to generate mixed gas of ammonia and carbon dioxide; the pressure stabilizing unit is used for stabilizing pressure 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 from the filtering unit to reduce nitrogen oxides in flue gas into nitrogen and water. The application remarkably reduces energy consumption and operation cost, solves the problem of low normal-temperature stability of ammonium carbamate, and effectively reduces the adverse effect of water and dust carried by ammonia generated in the process of dissolving, dewatering and filtering of ammonium carbamate on the denitration process of the catalyst in the subsequent SCR denitration unit.

Description

Technical Field

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

[0002] As environmental awareness continues to rise in my country, the issue of nitrogen oxide pollution from coal-fired power plants has garnered widespread attention. Nitrogen oxides are a significant atmospheric pollutant, severely impacting human health and the ecological environment. To effectively control nitrogen oxide emissions from coal-fired units, selective catalytic reduction (SCR) flue gas denitrification technology has become the preferred denitrification technology in my country's power industry.

[0003] Currently, urea is widely used as a denitrification reducing agent in SCR flue gas denitrification technology. However, the urea-to-ammonia process requires high temperatures, resulting in high energy costs. Furthermore, urea presents a number of challenges during storage, transportation, and dissolution, including low thermal stability, metal corrosion, and poor adaptability to existing processes.

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

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

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

[0007] The SCR flue gas denitrification system based on ammonium carbamate in an 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, wherein the storage bin is used to store ammonium carbamate powder; the conveying unit is connected to the storage bin and is used to convey the ammonium carbamate powder discharged from the storage bin; the pyrolysis unit is connected to the conveying unit and is used to pyrolyze the ammonium carbamate powder conveyed by the conveying unit to generate a mixed gas of ammonia and carbon dioxide; the pressure stabilizing unit is connected to the pyrolysis unit and is used to stabilize and cool the mixed gas discharged from the pyrolysis unit; the drying unit is connected to the pressure stabilizing unit and is used to dry the pressure-stabilized and cooled mixed gas discharged from the pressure stabilizing unit; the filtering unit is connected to the drying unit and is used to filter the desiccant in the mixed gas discharged from the drying unit; the SCR denitrification unit is connected to the filtering unit and is used to receive the mixed gas discharged from the filtering unit to reduce nitrogen oxides in the flue gas to nitrogen and water.

[0008] In some embodiments, the storage silo includes a primary silo, a secondary silo and a feeder, the primary silo is connected to the secondary silo, the primary silo is used to transport ammonium carbamate powder into the secondary silo according to the storage height of the secondary silo, the feeder is arranged at the discharge port of the secondary silo and is connected to the conveying unit, and a drying trough for storing a first desiccant is provided on the inner wall of at least one of the primary silo and the secondary silo, and the first desiccant is used to dry the ammonium carbamate powder.

[0009] In some embodiments, the conveying unit includes a feed pipe and an air pipe, the first end of the feed pipe is connected to the feeder, the second end of the feed pipe is connected to the pyrolysis unit, and the air pipe is connected to 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, wherein the temperature of the low-pressure hot air is 80°C-120°C and the pressure is 0.05MPa-0.2MPa.

[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 arranged at the bottom of the pyrolysis tower, and is used to heat the water entering the pyrolysis tower to 100°C-150°C, the second end of the feed pipe extends into the pyrolysis tower from the top of the pyrolysis tower in a vertical direction and is located above the hot water, wherein a portion of the ammonium carbamate powder is heat exchanged and pyrolyzed in the space above the hot water in the pyrolysis tower, and the other portion 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, and 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 feeding pipe has a flared portion, and the cross-sectional area of ​​the flared portion gradually increases along the discharge direction, wherein the flaring 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, and the hot water inlet and the hot water outlet are connected by 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, wherein the hot water entering the pyrolysis tower through the hot water inlet flows down to the bottom of the pyrolysis tower through the inner wall of the pyrolysis tower.

[0013] In some embodiments, the pressure stabilizing unit includes a buffer tank and a steam trap, the buffer tank having 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 reduce the temperature to 20°C-30°C, the steam trap is arranged at the liquid discharge port, and is used to discharge condensed water generated by the cooling of the mixed gas, and the first air outlet is connected to the drying unit to transport the stabilized and cooled mixed gas to the drying unit.

[0014] In some embodiments, the drying unit includes a drying tower, and a plurality of baffles are provided on the inner wall of the drying tower at intervals along its height direction. The baffles are arranged obliquely downward, and the plurality of baffles 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 filter unit, wherein 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 filter unit includes a plurality of filter cartridges arranged in an inner-outer direction, and the plurality of filter cartridges include at least one of a membrane filter cartridge and a polyester filter cartridge.

[0016] In some embodiments, the SCR denitration unit includes a reactor and multiple catalyst beds, and the multiple catalyst beds are spaced apart in the reactor 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 ammonium carbamate-based SCR flue gas denitrification system of the present invention uses ammonium carbamate as the primary denitrifier. From a process perspective, this system not only addresses the low room-temperature stability of ammonium carbamate, but also effectively reduces the adverse effects of moisture and dust carried by ammonia generated during the dissolution, dehydration, and filtration processes of ammonium carbamate on the subsequent catalytic denitrification process within the SCR denitrification unit. Compared to ammonia production from urea, the efficiency of ammonia production from a water-soluble ammonium carbamate denitrifier is higher. Calculations show that under full load, the ammonia production efficiency of the ammonium carbamate denitrifier is 6.6-21.2% higher than that of urea, with an average increase of approximately 13.9%. The energy consumption of ammonia production from the new denitrifier solution is reduced by 53.8-61.6%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the process of the SCR flue gas denitrification system according to an embodiment of the present invention.

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

[0020] Reference signs:

[0021] 100, an ammonium carbamate-based SCR flue gas denitration system; 1, a storage bin; 101, a first-stage bin; 102, a second-stage bin; 103, a feeder; 2, a conveying unit; 201, a conveying pipe; 2011, an expanded portion; 202, a gas conveying pipe; 3, a pyrolysis unit; 301, a pyrolysis tower; 3011, a water inlet; 3012, a mixed gas outlet; 3013, a hot water inlet; 302, a reboiler; 4, a pressure stabilizing unit; 401, a buffer tank; 4011, a first gas inlet; 4012, a first gas outlet; 4013, a liquid outlet; 402, a trap valve; 5, a drying unit; 501, a drying tower; 502, a baffle; 503, a serpentine passage; 504, a second gas inlet; 505, a second desiccant inlet; 506, a second gas outlet; 507, a second desiccant outlet; 6, a filtering unit; 7, an SCR denitration unit; 701, a reactor. DETAILED DESCRIPTION

[0022] Embodiments of the present application are described in detail below with reference to the accompanying drawings. The embodiments described below by reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0023] As shown in Figure 1 and Figure 2 , the ammonium carbamate-based SCR flue gas denitration system 100 according to an embodiment of the present application 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 denitration unit 7. The storage bin 1 is used to store ammonium carbamate powder, the conveying unit 2 is in communication with the storage bin 1 and is used to convey the ammonium carbamate powder discharged from the storage bin 1. The pyrolysis unit 3 is in communication with the conveying unit 2 and is used to pyrolyze the ammonium carbamate powder conveyed by the conveying unit 2 to generate mixed gas of ammonia and carbon dioxide. The pressure stabilizing unit 4 is in communication with the pyrolysis unit 3 and is used to stabilize the pressure and reduce the temperature of the mixed gas discharged from the pyrolysis unit 3. The drying unit 5 is in communication with the pressure stabilizing unit 4 and is used to dry the mixed gas stabilized in pressure and reduced in temperature and discharged from the pressure stabilizing unit 4. The filtering unit 6 is in communication with the drying unit 5 and is used to filter the desiccant in the mixed gas discharged from the drying unit 5. The SCR denitration unit 7 is in communication with the filtering unit 6 and is used to receive the mixed gas discharged from the filtering unit 6 to reduce the nitrogen oxides in the flue gas into nitrogen and water.

[0024] During use, the ammonium carbamate-based SCR flue gas denitrification system 100 of the present invention decomposes ammonium carbamate through heating in the pyrolysis unit 3 to produce a mixture of ammonia and carbon dioxide. Because the pyrolysis temperature of ammonium carbamate is relatively low, compared to the urea ammonia production process, energy consumption and operating costs can be significantly reduced.

[0025] The generated mixed gas is subjected to pressure stabilization and temperature reduction treatment in the pressure stabilization unit 4 to ensure that the mixed gas reaches the appropriate pressure and temperature before entering the SCR denitration unit 7 to avoid damage to the SCR catalyst. The mixed gas is dried in the drying unit 5 to remove moisture from it to prevent the generation of liquid water during the SCR reaction process, which would affect the denitration efficiency. The filtration unit 6 is used to remove particulate matter such as desiccant from the mixed gas to prevent these particulate matter from entering the SCR denitration unit 7 and affecting the activity and life of the catalyst. The filtered mixed gas is sent to the SCR denitration unit 7, where the ammonia gas acts as a reducing agent and reacts chemically with the nitrogen oxides in the flue gas under the action of the catalyst, reducing the nitrogen oxides to harmless nitrogen and water.

[0026] Therefore, the ammonium carbamate-based SCR flue gas denitrification system 100 of the present invention, which uses ammonium carbamate as the primary denitrifying agent, not only solves the problem of ammonium carbamate's low room-temperature stability from a process perspective, but also effectively reduces the adverse effects of moisture and dust carried by ammonia generated during the dissolution, dehydration, and filtration processes of ammonium carbamate on the subsequent catalytic denitrification process within the SCR denitrification unit 7. Compared to ammonia production from urea, the efficiency of ammonia production from a water-soluble ammonium carbamate denitrifier is higher. Calculations show that under full load conditions, the ammonia production efficiency of the ammonium carbamate denitrifier is 6.6% to 21.2% higher than that of urea, with an average increase of approximately 13.9%. The energy consumption of ammonia production from the new denitrifying agent solution is reduced by 53.8% to 61.6%.

[0027] In some embodiments, the storage silo 1 includes a primary silo 101, a secondary silo 102, and a feeder 103. The primary silo 101 is connected to the secondary silo 102 and is used to deliver ammonium carbamate powder into the secondary silo 102 according to the storage level of the secondary silo 102. The feeder 103 is located at the discharge port of the secondary silo 102 and is connected to the conveying unit 2. A drying trough for storing a first desiccant is provided on the inner wall of at least one of the primary silo 101 and the secondary silo 102. The first desiccant is used to dry the ammonium carbamate powder.

[0028] like 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 level of the ammonium carbamate powder in the secondary bin 102 decreases to a certain extent, the primary bin 101 will automatically deliver 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, ensuring the stable operation of the denitration process. Dry grooves are provided on the inner walls of the primary bin 101 and / or the secondary bin 102, and a first drying agent is stored in the dry grooves. The role of the drying agent is to absorb the moisture in the ammonium carbamate powder, prevent the powder from absorbing moisture and caking during storage, and ensure its flowability and conveying efficiency. The pyrolysis efficiency of the dried ammonium carbamate powder in the pyrolysis unit 3 is higher, and the generated ammonia gas mixture is of better quality, which is beneficial to more effective reduction of nitrogen oxides in the SCR denitration unit 7.

[0029] In some embodiments, the conveying unit 2 includes a material conveying pipe 201 and a gas conveying pipe 202. The first end of the material conveying pipe 201 communicates with the feeder 103, and the second end of the material conveying pipe 201 communicates with the pyrolysis unit 3. The gas conveying pipe 202 communicates with the material conveying pipe 201 for conveying low-pressure hot air into the material conveying pipe 201 to carry the ammonium carbamate powder in the material conveying pipe 201 into the pyrolysis unit 3. The temperature of the low-pressure hot air is 80-120°C, and the pressure is 0.05-0.2 MPa.

[0030] The low-pressure hot air conveyed by the gas conveying 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 80-120°C, and the pressure is 0.05-0.2 MPa. Such temperature and pressure ranges can ensure that the ammonium carbamate powder is not overheated and decomposed during the conveying process, and can also be smoothly conveyed to the pyrolysis unit 3.

[0031] Through the carrying action of the low-pressure hot air, the ammonium carbamate powder can be efficiently conveyed to the pyrolysis unit 3 through the material conveying pipe 201, reducing the loss of the material during the conveying process. The temperature and pressure of the hot air used during the conveying process are precisely controlled, which helps to maintain suitable reaction conditions in the pyrolysis unit 3, thereby ensuring that the ammonium carbamate powder can be fully pyrolyzed. Since the pressure and temperature of the hot air are relatively low, compared with the traditional compressed air conveying, this method can reduce energy consumption.

[0032] 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 located 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 from the top of the pyrolysis tower 301 into the pyrolysis tower 301 and is located above the hot water. A portion of the ammonium carbamate powder undergoes heat exchange and pyrolysis in the space above the hot water in the pyrolysis tower 301, while another portion of the ammonium carbamate powder falls into the hot water at the bottom of the pyrolysis tower 301 and undergoes heat exchange and pyrolysis with the hot water. The mixed gas outlet 3012 is used to discharge the mixed gas of ammonia and carbon dioxide produced by pyrolysis.

[0033] 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 produced by pyrolysis. The reboiler 302 is located at the bottom of the pyrolysis tower 301. Its main function is to heat the water entering the pyrolysis tower 301 to a temperature of 100°C-150°C. This temperature range promotes the pyrolysis reaction of ammonium carbamate. The second end of the feed pipe 201 extends into the pyrolysis tower 301 from the top, located above the hot water. This arrangement allows the ammonium carbamate powder to be pyrolyzed in two ways within the pyrolysis tower 301. A portion of the ammonium carbamate powder undergoes pyrolysis in the space above the hot water through indirect heat exchange with hot air. The other portion of the ammonium carbamate powder falls into the hot water and undergoes pyrolysis through direct heat exchange with the hot water.

[0034] By using both indirect heat exchange with hot water and direct heat exchange with hot water in the pyrolysis tower 301, ammonium carbamate powder can be pyrolyzed under different conditions, which helps to improve the pyrolysis efficiency. The reboiler 302 heats the water to a suitable temperature, so that the pyrolysis process can be more sufficient, while improving the utilization efficiency of thermal energy. The setting of the pyrolysis tower 301 makes the pyrolysis process more controllable, and the conditions of the pyrolysis reaction can be controlled by adjusting the water inlet 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 denitrification system.

[0035] In some embodiments, the second end of the delivery pipe 201 has a flared portion 2011 , and the cross-sectional area of ​​the flared portion 2011 gradually increases along the discharge direction, wherein the flaring angle of the flared portion 2011 is 80°-120°.

[0036] The flare angle of the flare portion 2011 is generally designed to be between 80° and 120°, which can provide sufficient space for the urea ammonium powder to flow out of the feed pipe 201 and diffuse in the pyrolysis tower 301, so as to increase the heat exchange area between the urea ammonium powder and the hot air in the pyrolysis tower 301, thereby improving the heat exchange efficiency and accelerating the pyrolysis.

[0037] In some embodiments, the side wall of the pyrolysis tower 301 is provided with a hot water inlet 3013 near the top end of the pyrolysis tower 301 and a hot water outlet (not shown in the figure) near the bottom end of the pyrolysis tower 301. The hot water inlet 3013 is in communication with the hot water outlet through a circulating 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.

[0038] It can be understood that the urea ammonium powder is easy to be adsorbed and bonded to the inner wall of the pyrolysis tower 301 during the pyrolysis process in the pyrolysis tower 301. If not cleaned in time, it may affect the pyrolysis efficiency and the operation of the equipment.

[0039] Therefore, the hot water inlet 3013 and the hot water outlet are provided on the side wall of the pyrolysis tower 301, and the two interfaces are connected through a circulating pump to form a hot water circulation system. The hot water enters the pyrolysis tower 301 from the inlet, flows down along the inner wall of the pyrolysis tower 301 to the bottom of the pyrolysis tower 301. In this process, the hot water contacts the urea ammonium powder adsorbed and bonded to the inner wall of the pyrolysis tower 301, transfers heat, and carries away the urea ammonium powder accumulated on the inner wall of the pyrolysis tower 301. The accumulation of scale is reduced, and the inner wall of the pyrolysis tower 301 is kept clean, which is conducive to the long-term stable operation of the equipment.

[0040] In addition, the hot water circulation system can ensure that the temperature distribution in the pyrolysis tower 301 is more uniform, which is helpful to improve the pyrolysis efficiency of the urea ammonium powder. Through the hot water circulation, the heat energy can be more effectively utilized, and the loss of heat energy is reduced.

[0041] In some embodiments, the pressure stabilizing unit 4 includes a buffer tank 401 and a drain valve 402. The buffer tank 401 has a first gas inlet 4011, a first gas outlet 4012, and a liquid discharge port 4013. The first gas inlet 4011 is in communication with the mixed gas outlet 3012 to stabilize and cool the mixed gas discharged from the mixed gas outlet 3012 to 20-30°C. The drain valve 402 is arranged at the liquid discharge port 4013 to discharge the condensed water generated by the cooling of the mixed gas. The first gas outlet 4012 is in communication with the drying unit 5 to convey the mixed gas after pressure stabilization and cooling to the drying unit 5.

[0042] As Figure 2As shown, the buffer tank 401 is the core component of the pressure stabilizing unit 4. It 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 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 in the buffer tank 401 can be reduced to 20°C-30°C through heat exchange equipment or natural cooling. The steam trap 402 is provided at the drain port 4013 to discharge the condensed water generated during the cooling process of the mixed gas. This prevents the condensed water from affecting subsequent processing units and ensures that the mixed gas received by the drying unit 5 is dry. The first air outlet 4012 is connected to the drying unit 5 and is used to transport the mixed gas after pressure stabilization and temperature reduction to the drying unit 5 for further drying treatment.

[0043] The pressure stabilizing effect of the buffer tank 401 helps to ensure the stability of the pressure of the mixed gas during transportation, which is very important for the subsequent drying and denitrification treatment. Through the cooling treatment, the temperature of the mixed gas can be lowered, and the energy loss of the mixed gas during transportation can be reduced, which is also beneficial to the subsequent drying treatment. The setting of the steam trap 402 can remove condensed water in time, prevent the condensed water from affecting the drying unit 5 and the SCR denitrification unit 7, and ensure the normal operation of the system. The mixed gas after the pressure stabilization and temperature reduction treatment 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. The pressure stabilization and temperature reduction treatment can improve the quality of the mixed gas, which helps to more effectively reduce nitrogen oxides in the SCR denitrification unit 7. By reducing the impact of condensed water and optimizing the treatment of the mixed gas, the maintenance frequency of the equipment can be reduced, thereby reducing maintenance costs.

[0044] In some embodiments, the drying unit 5 includes a drying tower 501. The inner wall of the drying tower 501 is provided with a plurality of baffles 502 spaced apart along its height. The baffles 502 are arranged obliquely downward, and the plurality of baffles 502 define a serpentine channel 503. The drying tower 501 has a second air inlet 504 and a second desiccant inlet 505 connected to the channel inlet of the serpentine channel 503, and a second air outlet 506 and a second desiccant outlet 507 connected to the channel outlet of the serpentine channel 503. The second air inlet 504 is connected to the first air outlet 4012, and the second air outlet 506 is connected to the filter unit 6. The second desiccant inlet 505 is used to allow 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.

[0045] like Figure 2As shown, the arrangement of serpentine channel 503 ensures uniform contact between the desiccant and the mixed gas throughout the drying process, thereby improving desiccant utilization efficiency. The mixed gas and secondary desiccant flow through serpentine channel 503, with multiple return flows, increasing the contact area and duration between the mixed gas and the desiccant, thereby enhancing the drying effect. The moisture content of the dried mixed gas is reduced, which helps improve the quality of the mixed gas and minimizes the impact on the subsequent SCR denitration unit 7.

[0046] In some embodiments, the filter unit 6 includes a plurality of filter cartridges arranged in an inner-outer direction, and the plurality of filter cartridges include at least one of a membrane filter cartridge and a polyester filter cartridge.

[0047] Membrane filter cartridges feature a microporous membrane made of PTFE or other materials, effectively filtering tiny particles. Polyester filter cartridges offer excellent filtration performance and chemical resistance. The mixed gas first passes through the outer filter cartridge to remove larger particles. It then passes through the inner filter cartridges, further purifying the mixed gas, ensuring that the particle content of the final output mixed gas meets the requirements of the SCR denitrification unit 7. The multi-layer filter cartridge design progressively removes impurities and particles from the mixed gas, improving filtration efficiency and effectiveness. Because the outer filter cartridge removes larger particles first, the inner filter cartridge (such as the membrane filter cartridge) is subjected to less pressure and contamination, which helps extend its service life. Multi-layer filtration significantly improves the quality of the mixed gas, reduces contamination of the SCR denitrification unit 7 catalyst, and ensures efficient operation. The lower particulate content in the filtered mixed gas reduces clogging and wear of the SCR denitrification unit 7 catalyst, thereby reducing maintenance costs and downtime. High-quality mixed gas enhances the denitrification efficiency of the SCR denitrification unit 7 and reduces nitrogen oxide emissions. Effective filtration enhances the stability and reliability of the entire denitrification system.

[0048] In some embodiments, the SCR denitration unit 7 includes a reactor 701 and multiple catalyst beds, which are spaced apart in the reactor 701 along the height direction of the reactor 701. The ratio of the distance between two adjacent catalyst beds to the diameter of the reactor 701 is 5-10.

[0049] 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 fluid dynamic conditions inside the reactor 701, allowing the mixed gas to be evenly distributed inside the reactor 701, avoiding airflow dead zones or excessive turbulence, thereby improving the stability of the system and the denitrification efficiency. Appropriate catalyst bed spacing helps to reduce the impact of airflow between catalyst beds and extend the service life of the catalyst. By optimizing the layout of the catalyst bed, the stability of the entire SCR denitrification unit 7 can be improved and system fluctuations caused by uneven airflow distribution can be reduced. By improving the nitrogen oxide reduction efficiency and improving the stability of the system, the denitrification effect can be further improved 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.

[0050] Optionally, the catalytic denitration reaction temperature in the SCR denitration unit 7 is controlled at 300°C-400°C.

[0051] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0053] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0054] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0055] In the present invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction 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 can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification, as well as features of different embodiments or examples, unless they are mutually inconsistent.

[0056] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify 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: include: A storage silo, wherein the storage silo is used to store ammonium carbamate powder; a conveying unit, the conveying unit being in communication with the storage bin and being used to convey the ammonium carbamate powder discharged from the storage bin, the conveying unit comprising a conveying pipe and an air pipe, the first end of the conveying pipe being in communication with the storage bin; The pyrolysis unit is connected to the conveying unit and is used to pyrolyze the ammonium carbamate powder conveyed by the conveying unit to generate a mixed gas of ammonia and carbon dioxide. The second end of the feed pipe is connected to the pyrolysis unit. 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 located at the bottom of the pyrolysis tower and is used to heat the water entering the pyrolysis tower to 100°C-150°C. The second end of the feed pipe extends vertically from the top of the pyrolysis tower into the pyrolysis tower and is located above the hot water. A portion of the ammonium carbamate powder in the pyrolysis tower The space above the hot water is heat-exchanged and pyrolyzed, 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 the pyrolysis. 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 by 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, wherein the hot water entering the pyrolysis tower through the inner wall of the pyrolysis tower flows down to the bottom of the pyrolysis tower; a pressure stabilizing unit, the pressure stabilizing unit being in communication with the pyrolysis unit and being used for stabilizing the pressure and reducing the temperature of the mixed gas discharged from the pyrolysis unit; a drying unit, the drying unit being in communication with the pressure stabilizing unit and being used for drying the pressure-stabilized and temperature-reduced mixed gas discharged from the pressure stabilizing unit; a filter unit, the filter unit being in communication with the drying unit and configured to filter the desiccant in the mixed gas discharged from the drying unit; An SCR denitration unit is communicated with the filter unit and is used to receive the mixed gas discharged from the filter unit to reduce nitrogen oxides in the flue gas into nitrogen and water.

2. The SCR flue gas denitrification system based on ammonium carbamate according to claim 1, characterized in that: The storage silo includes a primary silo, a secondary silo and a feeder. The primary silo is connected to the secondary silo. The primary silo is used to transport ammonium carbamate powder into the secondary silo according to the storage height of the secondary silo. The feeder is arranged at the discharge port of the secondary silo and is connected to the conveying unit. A drying trough for storing a first desiccant is provided on the inner wall of at least one of the primary silo and the secondary silo. The first desiccant is used to dry the ammonium carbamate powder.

3. The SCR flue gas denitrification system based on ammonium carbamate according to claim 2, characterized in that: The first end of the feed pipe is connected to the feeder, and the air pipe is connected to 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, wherein the temperature of the low-pressure hot air is 80°C-120°C and the pressure is 0.05MPa-0.2MPa.

4. The SCR flue gas denitrification system based on ammonium carbamate according to claim 1, characterized in that: The second end of the conveying pipe has a flared portion, and the cross-sectional area of ​​the flared portion gradually increases along the discharge direction, wherein the flaring angle of the flared portion is 80°-120°.

5. The SCR flue gas denitrification system based on ammonium carbamate according to claim 1, 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 reduce the temperature to 20°C-30°C. The steam trap is arranged at the liquid discharge port to discharge condensed water generated by the cooling of the mixed gas. The first air outlet is connected to the drying unit to transport the stabilized and cooled mixed gas to the drying unit.

6. The SCR flue gas denitrification system based on ammonium carbamate according to claim 5, characterized in that: The drying unit includes a drying tower, and a plurality of baffles are provided on the inner wall of the drying tower and arranged at intervals along the height direction thereof. The baffles are arranged to be tilted obliquely downward, and the plurality of baffles 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 filter unit, wherein 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.

7. The SCR flue gas denitrification system based on ammonium carbamate according to claim 1, characterized in that: The filter unit includes a plurality of filter cartridges arranged in an inner and outer direction, and the plurality of filter cartridges include at least one of a membrane filter cartridge and a polyester filter cartridge.

8. The SCR flue gas denitrification system based on ammonium carbamate according to claim 6, characterized in that: The SCR denitration unit includes a reactor and multiple catalyst beds. The multiple catalyst beds are spaced apart in the reactor 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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