A SCR flue gas denitrification system for coal-fired power plants

Abstract

The present invention discloses an SCR flue gas denitrification system for a coal-fired power plant, comprising a storage bin, a pyrolysis unit, a pressure stabilizing unit, a drying unit, a filtering unit, and an SCR denitrification unit. The pressure stabilizing unit is used to stabilize and cool the mixed gas discharged from the pyrolysis unit; the drying unit is used to dry the mixed gas discharged from the pressure stabilizing unit; the filtering unit is used to filter the desiccant in the mixed gas discharged from the drying unit; and the SCR denitrification unit is used to receive the mixed gas discharged from the filtering unit to reduce nitrogen oxides in the flue gas to nitrogen and water. From a process perspective, the present invention not only solves the problem of low room temperature stability of ammonium carbamate, but also effectively reduces the adverse effects of moisture and dust carried by ammonia generated by ammonium carbamate during the dissolution, dehydration, and filtration processes on the subsequent catalyst denitrification process in the SCR denitrification unit. Compared with urea ammonia production, the efficiency of water-soluble ammonia production by ammonium carbamate denitrification agent is higher than that of urea ammonia production.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas denitrification, and in particular to an SCR flue gas denitrification system for a coal-fired power plant. 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 provides an SCR flue gas denitrification system for a coal-fired power plant.

[0007] The SCR flue gas denitrification system of a coal-fired power plant according to an embodiment of the present invention includes a storage bin, a pyrolysis unit, a voltage stabilizing unit, a drying unit, a filtering unit and an SCR denitrification unit. The storage bin is used to store ammonium carbamate powder; the pyrolysis unit includes a pyrolysis tower, the pyrolysis tower has a feed port, a drain port, a steam inlet and a mixed gas outlet, the feed port is connected to the storage bin, a plurality of pyrolysis tubes extending in a vertical direction are provided in the pyrolysis tower, the steam inlet is used for superheated steam to enter and the ammonium carbamate powder entering the feed port falls to the bottom of the pyrolysis tower through the pyrolysis tube, and the ammonium carbamate powder and the superheated steam are heat-exchanged and pyrolyzed in the pyrolysis tube to generate The mixed gas of ammonia and carbon dioxide, the mixed gas generated by pyrolysis is discharged through the mixed gas outlet, and the condensed water generated by pyrolysis is discharged through the drain outlet; the pressure stabilizing unit is connected to the mixed gas outlet, and is used to stabilize the pressure 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 the nitrogen oxides in the flue gas into 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 pyrolysis 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 temperature of the superheated steam is 240° C.-320° C., and the pressure is 0.05 MPa-0.5 MPa.

[0010] In some embodiments, the inner wall of the pyrolysis tower is provided with a plurality of partitions arranged at intervals along its height direction, the partitions having perforations for the pyrolysis tubes to pass through, and the plurality of partitions form a first serpentine channel. The pyrolysis tower also has a hot flue gas inlet connected to the channel inlet of the first serpentine channel and a hot flue gas outlet connected to the channel outlet of the first serpentine channel. The hot flue gas inlet is used for hot flue gas with a temperature of 150°C-200°C to enter the first serpentine channel and to perform indirect heat exchange with ammonium carbamate powder. The hot flue gas after heat exchange is discharged through the hot flue gas outlet.

[0011] In some embodiments, a disc distributor is provided in the pyrolysis tower between the feed port and the pyrolysis tubes, and the disc distributor is used to evenly distribute the ammonium carbamate powder entering from the feed port to different pyrolysis tubes.

[0012] 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 cool it down to 20°C-30°C, the first air outlet is connected to the drying unit to transport the stabilized and cooled mixed gas to the drying unit, and the steam trap is arranged at the liquid discharge port for discharging condensed water generated by the cooling of the mixed gas.

[0013] In some embodiments, a plurality of spaced-apart baffles are provided in the buffer tank, and the plurality of baffles define a second serpentine channel, the channel inlet of the second serpentine channel is connected to the first air inlet, and the channel outlet of the second serpentine channel is connected to the first air outlet.

[0014] In some embodiments, the drying unit includes a drying tower, which is provided with a plurality of drying layers arranged at intervals along its height direction, and each drying layer is provided with desiccant particles. The drying tower has a second air inlet and a second air outlet, the second air inlet is connected to the first air outlet, and the second air outlet is connected to the filter unit. The mixed gas entering the second air inlet is dried by multiple layers of the drying layers and then discharged through the second air outlet.

[0015] In some embodiments, the filter unit includes a filter tower, which has a third air inlet and a third air outlet. The third air inlet is connected to the second air outlet, and the third air outlet is connected to the SCR denitrification unit. The filter tower is provided with a plurality of filter layers arranged at intervals along its height. The filter layer is filled with at least one of a membrane filter cartridge and a polyester filter cartridge. The mixed gas entering the third air inlet is filtered by the filter layer and discharged through the third air outlet.

[0016] In some embodiments, the SCR denitrification unit includes a reactor and multiple catalyst beds, the reactor and the multiple catalyst beds are spaced apart in the reactor along the height direction of the reactor, and the ratio of the distance between two adjacent catalyst beds to the diameter of the reactor is 5-10.

[0017] The SCR flue gas denitrification system for coal-fired power plants in the embodiments of the present invention uses ammonium carbamate as the primary denitrifier. From a process perspective, this not only addresses the issue of ammonium carbamate's low room-temperature stability, but also effectively reduces the adverse effects of moisture and dust carried by ammonia generated during the dissolution, dehydration, and filtration processes 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 conditions, the ammonia production efficiency of the ammonium carbamate denitrifier increases by 8.6% to 22.8% compared to urea, with an average increase of approximately 15.7%. The energy consumption of ammonia production from the new denitrifier solution is reduced by 52.4% to 62.7%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic flow chart of an SCR flue gas denitrification system for a coal-fired power plant according to an embodiment of the present invention.

[0019] Figure 2 Schematic diagram of the structure of the SCR flue gas denitrification system of a coal-fired power plant according to an embodiment of the present invention.

[0020] Reference numerals:

[0021] 100. SCR Flue Gas Denitrification System for Coal-fired Power Plants; 1. Storage Silo; 101. Primary Silo; 102. Secondary Silo; 103. Feeder; 2. Pyrolysis Unit; 201. Pyrolysis Tower; 2011. Feeding Port; 2012. Drainage Port; 2013. Steam Inlet; 2014. Mixed Gas Outlet; 2015. Hot Flue Gas Inlet; 2016. Hot Flue Gas Outlet; 202. Pyrolysis Tube; 203. Baffle; 204. First Serpentine Channel; 205. Disc Distributor; 3. Voltage Stabilization Unit; 30 1. Buffer tank; 3011. First air inlet; 3012. First air outlet; 3013. Drain; 302. Steam trap; 303. Baffle; 304. Second serpentine channel; 4. Drying unit; 401. Drying tower; 4011. Second air inlet; 4012. Second air outlet; 402. Drying layer; 5. Filter unit; 501. Filter tower; 5011. Third air inlet; 5012. Third air outlet; 502. Filter layer; 6. SCR denitrification unit; 601. Reactor. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0023] like Figure 1 and Figure 2As shown, the SCR flue gas denitration system 100 of a coal-fired power plant according to an embodiment of the present invention includes a storage silo 1, a pyrolysis unit 2, a voltage stabilization unit 3, a drying unit 4, a filtration unit 5, and an SCR denitration unit 6. The storage silo 1 is used to store ammonium carbamate powder. The pyrolysis unit 2 includes a pyrolysis tower 201, which has a feed port 2011, a drain port 2012, a steam inlet 2013, and a mixed gas outlet 2014. The feed port 2011 is connected to the storage silo 1.

[0024] Pyrolysis tower 201 is equipped with multiple vertically extending pyrolysis tubes 202. Superheated steam enters through steam inlet 2013, allowing ammonium carbamate powder, which enters through discharge port 2011, to fall to the bottom of pyrolysis tower 201 through pyrolysis tubes 202. The ammonium carbamate powder and superheated steam exchange heat within pyrolysis tubes 202, resulting in pyrolysis and decomposition to form a mixture of ammonia and carbon dioxide. The resulting mixture is discharged through mixed gas outlet 2014, and condensed water is discharged through drain port 2012.

[0025] The pressure stabilizing unit 3 is connected to the mixed gas outlet 2014 and is used to stabilize the pressure and reduce the temperature of the mixed gas discharged from the pyrolysis unit 2. The drying unit 4 is connected to the pressure stabilizing unit 3 and is used to dry the stabilized and cooled mixed gas discharged from the pressure stabilizing unit 3. The filtering unit 5 is connected to the drying unit 4 and is used to filter the desiccant in the mixed gas discharged from the drying unit 4. The SCR denitrification unit 6 is connected to the filtering unit 5 and is used to receive the mixed gas discharged from the filtering unit 5 to reduce the nitrogen oxides in the flue gas to nitrogen and water.

[0026] When the SCR flue gas denitrification system 100 of a coal-fired power plant according to an embodiment of the present invention is in use, the storage silo 1 is used to store ammonium carbamate powder. This powder can be stably stored at room temperature, reducing the need for high-temperature storage, thereby reducing energy consumption and storage costs.

[0027] Ammonium carbamate powder enters the pyrolysis tower 201 of the pyrolysis unit 2 from the storage silo 1 through the discharge port 2011. The pyrolysis tower 201 is equipped with multiple vertically extending pyrolysis tubes 202 connected to the bottom of the tower to ensure that the ammonium carbamate powder falls evenly within the pyrolysis tower 201. Superheated steam is introduced into the pyrolysis tubes 202 through the steam inlet 2013 and mixes with the falling ammonium carbamate powder. Within the pyrolysis tubes 202, the ammonium carbamate and the superheated steam undergo direct heat exchange and a pyrolysis reaction occurs, producing a mixed gas of ammonia and carbon dioxide. The mixed gas produced by the pyrolysis is discharged through the mixed gas outlet 2014, while condensed water is discharged through the drain port 2012.

[0028] The resulting mixed gas is pressure-stabilized and cooled by the pressure-stabilizing unit 3 to ensure that it reaches the appropriate pressure and temperature before entering the SCR denitration unit 6, thereby avoiding damage to the SCR catalyst. The mixed gas is dried in the drying unit 4 to remove moisture, thereby preventing the generation of liquid water during the SCR reaction and affecting denitration efficiency. The filtering unit 5 is used to remove particulate matter, such as desiccant, from the mixed gas to prevent these particles from entering the SCR denitration unit 6 and affecting the activity and life of the catalyst. The filtered mixed gas is then fed into the SCR denitration unit 6, where ammonia, acting as a reducing agent, reacts chemically with nitrogen oxides in the flue gas under the action of the catalyst, reducing the nitrogen oxides to harmless nitrogen and water.

[0029] Therefore, the coal-fired power plant SCR flue gas denitrification system 100 of the embodiment of the present invention uses ammonium carbamate as the main denitrifying agent. From a process perspective, this not only solves the problem of ammonium carbamate's low room-temperature stability, but also effectively reduces the adverse effects of ammonia gas produced during the dissolution, dehydration, and filtration of ammonium carbamate, carrying moisture and dust, on the subsequent catalytic denitrification process within the SCR denitrification unit 6. Compared to ammonia production from urea, the efficiency of ammonia production from a water-soluble ammonium carbamate denitrifier is higher than that of ammonia production from urea. Calculations show that under full load conditions, the ammonia production efficiency of the ammonium carbamate denitrifier is 8.6% to 22.8% higher than that of urea, with an average increase of approximately 15.7%. The energy consumption of ammonia production from the new denitrifying agent solution is reduced by 52.4% to 62.7%.

[0030] 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. The primary silo 101 is used to deliver ammonium carbamate powder into the secondary silo 102 according to the storage height of the secondary silo 102. The feeder 103 is located at the discharge port of the secondary silo 102 and is connected to the pyrolysis unit 2. A drying tank 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.

[0031] like Figure 2As shown, the primary silo 101 serves as the main storage area for large quantities of ammonium carbamate powder. When the ammonium carbamate powder storage level in the secondary silo 102 drops to a certain level, the primary silo 101 automatically transfers the powder to the secondary silo 102 to ensure continuous operation of the denitration system. A feeder 103, located at the discharge port of the secondary silo 102, is responsible for evenly and continuously transferring the ammonium carbamate powder from the secondary silo 102 to the pyrolysis unit 2, ensuring a stable denitration process. Drying troughs are provided on the inner walls of the primary silo 101 and / or the secondary silo 102, containing a first desiccant. The desiccant absorbs moisture from the ammonium carbamate powder, preventing it from absorbing moisture and clumping during storage, thereby ensuring its fluidity and transport efficiency. The dried ammonium carbamate powder achieves higher pyrolysis efficiency in the pyrolysis unit 2, resulting in a higher-quality ammonia mixture, which facilitates more effective nitrogen oxide reduction in the SCR denitration unit 6.

[0032] Optionally, the temperature of the superheated steam is 240° C.-320° C., and the pressure is 0.05 MPa-0.5 MPa.

[0033] Within this temperature range, ammonium carbamate can effectively undergo pyrolysis to produce ammonia and carbon dioxide. The appropriate temperature ensures the reaction rate and conversion rate, thereby improving the denitrification efficiency of the entire system. The selected temperature range avoids excessive energy consumption. If the temperature is too low, the pyrolysis reaction may be incomplete, affecting the denitrification effect; while if the temperature is too high, energy consumption may increase, resulting in unnecessary cost. This temperature range does not cause excessive thermal stress on the materials of equipment such as the pyrolysis tower 201 and pyrolysis tube 202, helping to extend the service life of the equipment.

[0034] Selecting the right pressure helps control the phase of the superheated steam, ensuring thorough mixing of the steam with the ammonium carbamate powder in the pyrolysis tube 202 and efficient heat transfer. Low pressure helps reduce the risk of equipment corrosion caused by high temperature and high pressure, thereby lowering maintenance costs. Within the pressure range of 0.05 MPa to 0.5 MPa, superheated steam can be produced economically without the need for high-pressure steam generation equipment, thus reducing system investment costs. Maintaining a lower pressure range also helps improve system safety and mitigate safety risks caused by abnormal pressure.

[0035] By selecting a superheated steam temperature of 240° C.-320° C. and a pressure of 0.05 MPa-0.5 MPa, the present invention ensures the thermal decomposition efficiency of ammonium carbamate while also taking into account the energy consumption, safety and economy of system operation.

[0036] In some embodiments, the inner wall of the pyrolysis tower 201 is provided with a plurality of partitions 203 spaced apart along its height. The partitions 203 have perforations for the pyrolysis tubes 202 to pass through. The plurality of partitions 203 form a first serpentine channel 204. The pyrolysis tower 201 also has a hot flue gas inlet 2015 connected to the channel inlet of the first serpentine channel 204 and a hot flue gas outlet 2016 connected to the channel outlet of the first serpentine channel 204. The hot flue gas inlet 2015 is used to allow hot flue gas at a temperature of 150°C to 200°C to enter the first serpentine channel 204 for indirect heat exchange with ammonium carbamate powder. The hot flue gas after heat exchange is discharged through the hot flue gas outlet 2016.

[0037] When the hot flue gas flows in the first serpentine channel 204, it does not directly contact the ammonium carbamate powder, but transfers heat to the ammonium carbamate through heat exchange. This method can effectively avoid the direct impact of pollutants in the flue gas on the ammonium carbamate powder, while also improving thermal efficiency. The serpentine flow of the hot flue gas and the provision of the partition 203 increase the heat exchange area, improve the heat exchange efficiency, and contribute to the rapid thermal decomposition of ammonium carbamate. Utilizing the waste heat of the hot flue gas for the thermal decomposition of ammonium carbamate can reduce the input of additional heat energy and reduce the energy consumption of the system. After the flue gas temperature is reduced after heat exchange, it enters the flue gas exhaust system of the coal-fired power plant for treatment.

[0038] In some embodiments, a disc distributor 205 is provided in the pyrolysis tower 201 between the feed port 2011 and the pyrolysis tubes 202 . The disc distributor 205 is used to evenly distribute the ammonium carbamate powder entering from the feed port 2011 to different pyrolysis tubes 202 .

[0039] The primary function of the disc distributor 205 is to evenly distribute the ammonium carbamate powder entering from the feed port 2011 to the multiple pyrolysis tubes 202, ensuring that each tube 202 receives an equal amount of powder, thereby preventing overloading or underloading of certain tubes 202. This even distribution of powder ensures consistent pyrolysis efficiency across each tube 202, improving the overall efficiency of the pyrolysis tower 201. This even distribution also reduces clogging of certain tubes 202 due to excessive powder, thereby ensuring a continuous and stable pyrolysis process.

[0040] In some embodiments, the pressure stabilizing unit 3 includes a buffer tank 301 and a drain valve 302. The buffer tank 301 has a first air inlet 3011, a first air outlet 3012, and a liquid drain 3013. The first air inlet 3011 is connected to the mixed gas outlet 2014 to stabilize the pressure of the mixed gas discharged from the mixed gas outlet 2014 and reduce the temperature to 20°C-30°C. The first air outlet 3012 is connected to the drying unit 4 to deliver the stabilized and cooled mixed gas to the drying unit 4. The drain valve 302 is provided at the liquid drain 3013 to discharge condensed water generated by the cooling of the mixed gas.

[0041] The buffer tank 301 is the core of the pressure stabilization unit 3 and has a first air inlet 3011 and a first air outlet 3012. The first air inlet 3011 is connected to the mixed gas outlet 2014 and receives the mixed gas from the pyrolysis unit 2. The first air outlet 3012 delivers the stabilized and cooled mixed gas to the drying unit 4.

[0042] The mixed gas in the buffer tank 301 needs to be cooled to 20°C-30°C before entering the drying unit 4. This temperature range is beneficial to the subsequent drying process and also helps to reduce the volatilization of ammonia and improve the safety of the system. The design and buffering effect of the buffer tank 301 help to stabilize the pressure of the mixed gas and ensure that the drying unit 4 can stably receive the mixed gas. The steam trap 302 is provided at the drain port 3013 of the buffer tank 301 to discharge the condensed water generated by the mixed gas during the cooling process. These condensed waters may contain incompletely reacted ammonium carbamate or other impurities, so they need to be discharged regularly. Removing the condensed water can prevent the impurities in the condensed water from contaminating the subsequent drying process and the SCR denitrification unit 6.

[0043] The design of the pressure stabilizing unit 3 ensures that the mixed gas reaches stable pressure and temperature before entering the drying unit 4, improving the stability and reliability of the system. Through pressure stabilization and temperature reduction, the mixed gas is more stable upon entering the drying unit 4, facilitating stable operation and improving drying efficiency. Lowering the temperature of the mixed gas helps reduce ammonia volatilization, improving system safety and avoiding the environmental and safety risks associated with ammonia leakage. Discharging condensed water through the steam trap 302 reduces contamination to subsequent processes and improves the overall system efficiency.

[0044] In some embodiments, a plurality of spaced-apart baffles 303 are provided in the buffer tank 301, and the plurality of baffles 303 define a second serpentine channel 304, the channel inlet of the second serpentine channel 304 is connected to the first air inlet 3011, and the channel outlet of the second serpentine channel 304 is connected to the first air outlet 3012.

[0045] like Figure 2 As shown, the design of baffles 303 increases the airflow path within buffer tank 301, forming a serpentine passage. This increases the contact area between the mixed gas and baffles 303 and improves heat exchange efficiency. Through this serpentine passage, the mixed gas makes multiple turns within buffer tank 301, extending its residence time within the buffer tank 301 and enabling more efficient heat exchange between the mixed gas and the tank's inner walls. The design of baffles 303 helps better control the temperature and pressure of the mixed gas, ensuring that the mixed gas reaches the desired temperature and pressure conditions before entering the drying unit 4.

[0046] In some embodiments, the drying unit 4 includes a drying tower 401, which is provided with a plurality of drying layers 402 spaced apart along its height. Each drying layer 402 is provided with desiccant particles. The drying tower 401 has a second air inlet 4011 and a second air outlet 4012. The second air inlet 4011 is connected to the first air outlet 3012, and the second air outlet 4012 is connected to the filter unit 5. The mixed air entering the second air inlet 4011 is dried by the multiple drying layers 402 and then discharged through the second air outlet 4012.

[0047] The second air inlet 4011 communicates with the first air outlet 3012 of the pressure stabilizing unit 3, receiving the mixed air from the pressure stabilizing unit 3. The second air outlet 4012 communicates with the filter unit 5, delivering the dried mixed air to the filter unit 5. After the mixed air from the pressure stabilizing unit 3 enters the drying tower 401, it passes through multiple drying layers 402. The desiccant particles in each drying layer 402 absorb moisture from the mixed air, thereby drying the mixed air.

[0048] The multi-layer drying layer 402 design ensures that the mixed gas is fully dried within the drying tower 401, ensuring stable operation of the subsequent SCR denitration unit 6. This multi-layer drying layer 402 design helps optimize the drying process, ensuring that the mixed gas remains within the drying tower 401 for a sufficiently long time, thereby improving the drying effect. By fully drying the mixed gas, ammonia volatilization in the denitration unit is reduced, enhancing system stability.

[0049] In some embodiments, the filtration unit 5 includes a filtration tower 501 having a third air inlet 5011 and a third air outlet 5012. The third air inlet 5011 is connected to the second air outlet 4012, and the third air outlet 5012 is connected to the SCR denitration unit 6. The filtration tower 501 is provided with a plurality of filtration layers 502 arranged at intervals along its height. The filtration layers 502 are filled with at least one of a membrane filter cartridge and a polyester filter cartridge. The mixed gas entering the third air inlet 5011 is filtered by the filtration layers 502 and then discharged through the third air outlet 5012.

[0050] After the mixed gas from the drying unit 4 enters the filter tower 501, it passes through multiple filter layers 502. The filter cartridges within each filter layer 502 filter desiccant particles and other impurities from the mixed gas, ensuring the cleanliness of the mixed gas. The design of the filter layers 502 allows the mixed gas to pass through the filter cartridges multiple times within the filter tower 501, ensuring that impurities are fully filtered. The membrane filter cartridges and polyester filter cartridges are key components of the filter layer 502. They effectively filter desiccant particles and other impurities, ensuring the cleanliness of the mixed gas before entering the SCR denitration unit 6.

[0051] In some embodiments, the SCR denitrification unit 6 includes a reactor 601 and multiple catalyst beds. The reactor 601 and the multiple catalyst beds are spaced apart in the reactor 601 along the height direction of the reactor 601, and the ratio of the distance between two adjacent catalyst beds to the diameter of the reactor 601 is 5-10.

[0052] 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 601, allowing the mixed gas to be evenly distributed inside the reactor 601, 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 6 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.

[0053] Optionally, the catalytic denitration reaction temperature in the SCR denitration unit 6 is controlled at 300°C-400°C.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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. A SCR flue gas denitrification system for a coal-fired power plant, characterized in that: include: A storage silo for storing ammonium carbamate powder, comprising a primary silo, a secondary silo, and a feeder, wherein the primary silo is in communication with the secondary silo, and the primary silo is used to transport the ammonium carbamate powder into the secondary silo according to the storage height of the secondary silo. 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; The pyrolysis unit, the feeder is arranged at the discharge port of the secondary silo and is connected to the pyrolysis unit, the pyrolysis unit includes a pyrolysis tower, the pyrolysis tower has a feed port, a drain port, a steam inlet and a mixed gas outlet, the feed port is connected to the storage silo, a plurality of pyrolysis tubes extending in a vertical direction are provided in the pyrolysis tower, the steam inlet is used for superheated steam to enter and the ammonium carbamate powder entering the feed port falls to the bottom of the pyrolysis tower through the pyrolysis tube, the ammonium carbamate powder and the superheated steam are heat-exchanged and pyrolyzed in the pyrolysis tube to generate a mixed gas of ammonia and carbon dioxide, and the mixed gas generated by the pyrolysis is passed through the mixing The combined gas is discharged through the outlet, and the condensed water generated by pyrolysis is discharged through the drain outlet. The inner wall of the pyrolysis tower is provided with a plurality of partitions arranged at intervals along its height direction. The partitions have perforations for the pyrolysis tubes to pass through. The plurality of partitions form a first serpentine channel. The pyrolysis tower further has a hot flue gas inlet connected to the channel inlet of the first serpentine channel and a hot flue gas outlet connected to the channel outlet of the first serpentine channel. The hot flue gas inlet is used for hot flue gas with a temperature of 150°C-200°C to enter the first serpentine channel and perform indirect heat exchange with ammonium carbamate powder. The hot flue gas after heat exchange is discharged through the hot flue gas outlet; a pressure stabilizing unit, the pressure stabilizing unit being in communication with the mixed gas outlet 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 of a coal-fired power plant according to claim 1, characterized in that: The temperature of the superheated steam is 240° C.-320° C., and the pressure is 0.05 MPa-0.5 MPa.

3. The SCR flue gas denitrification system of a coal-fired power plant according to claim 1, characterized in that: A disc distributor is provided in the pyrolysis tower and is located between the feed port and the pyrolysis tubes. The disc distributor is used to evenly distribute the ammonium carbamate powder entering from the feed port to different pyrolysis tubes.

4. The SCR flue gas denitrification system of a coal-fired power plant 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 first air outlet is connected to the drying unit to transport the stabilized and cooled mixed gas to the drying unit. The steam trap is arranged at the liquid discharge port to discharge condensed water generated by the cooling of the mixed gas.

5. The SCR flue gas denitrification system of a coal-fired power plant according to claim 4, characterized in that: A plurality of spaced-apart baffles are provided in the buffer tank, and the plurality of baffles define a second serpentine channel. The channel inlet of the second serpentine channel is connected to the first air inlet, and the channel outlet of the second serpentine channel is connected to the first air outlet.

6. The SCR flue gas denitrification system of a coal-fired power plant according to claim 5, characterized in that: The drying unit includes a drying tower, which is provided with a plurality of drying layers arranged at intervals along its height direction, and each drying layer is provided with desiccant particles. The drying tower has a second air inlet and a second air outlet, the second air inlet is connected to the first air outlet, and the second air outlet is connected to the filter unit. The mixed air entering the second air inlet is dried by multiple layers of the drying layers and then discharged through the second air outlet.

7. The SCR flue gas denitrification system of a coal-fired power plant according to claim 6, characterized in that: The filter unit includes a filter tower, which has a third air inlet and a third air outlet. The third air inlet is connected to the second air outlet, and the third air outlet is connected to the SCR denitrification unit. The filter tower is provided with a plurality of filter layers arranged at intervals along its height. The filter layer is filled with at least one of a membrane filter cartridge and a polyester filter cartridge. The mixed gas entering the third air inlet is filtered by the filter layer and then discharged through the third air outlet.

8. The SCR flue gas denitrification system of a coal-fired power plant according to claim 7, characterized in that: The SCR denitration unit includes a reactor and multiple catalyst beds. The reactor 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.

Images