SCR flue gas denitration system for coal-fired power plant

Abstract

The invention discloses a coal-fired power plant SCR flue gas denitration system which comprises a storage bin, a pyrolysis unit, a pressure stabilizing unit, a drying unit, a filtering unit and an SCR denitration unit, and the pressure stabilizing unit is used for stabilizing and cooling mixed gas discharged by the pyrolysis unit; the drying unit is used for drying the mixed gas discharged by the pressure stabilizing unit; the filtering unit is used for filtering the drying agent in the mixed gas discharged by the drying unit; 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. The method not only solves the problem of low stability of ammonium carbamate at normal temperature from the aspect of process, but also effectively reduces 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. The water-soluble ammonia preparation efficiency of the ammonium carbamate denitration agent is higher than that of urea for ammonia preparation.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas denitration, and particularly to an SCR flue gas denitration system for coal-fired power plants. 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 extensive attention. Nitrogen oxides are an important pollutant in the atmosphere, causing serious impacts 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 denitration technology has become the preferred denitration technology in China's power industry.

[0003] Currently, in SCR flue gas denitration technology, urea is widely used as a denitration reducing agent. However, the urea-to-ammonia process 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 denitration 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 technologies to some extent.

[0006] To this end, an embodiment of the present invention provides an SCR flue gas denitration system for coal-fired power plants.

[0007] The SCR flue gas denitrification system of a coal-fired power plant in an embodiment of the present invention includes a storage bin, 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 pyrolysis unit includes a pyrolysis tower which has a feeding port, a drainage port, a steam inlet, and a mixed gas outlet. The feeding port is communicated with the storage bin. A plurality of pyrolysis tubes extending in the vertical direction are arranged in the pyrolysis tower. The steam inlet is for superheated steam to enter and pass through the pyrolysis tubes together with the ammonium carbamate powder entering from the feeding port and fall to the bottom of the pyrolysis tower. The ammonium carbamate powder and the superheated steam exchange heat in the pyrolysis tubes to generate a 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 drainage port. The pressure stabilizing unit is communicated with the mixed gas outlet and is used for stabilizing the pressure and reducing the temperature of the mixed gas discharged from the pyrolysis unit. The drying unit is communicated with the pressure stabilizing unit and is used for drying the mixed gas with stabilized pressure and reduced temperature discharged from the pressure stabilizing unit. The filtering unit is communicated with the drying unit and is used for filtering the desiccant in the mixed gas discharged from the drying unit. The SCR denitrification unit is communicated with the filtering unit and is used for receiving 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 bin includes a primary bin, a secondary bin, and a feeder. The primary bin is communicated 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 is communicated with the pyrolysis unit. A drying tank for storing a first desiccant is arranged 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.

[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, a plurality of partitions are arranged on the inner wall of the pyrolysis tower 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 also has a hot flue gas inlet communicated with the channel inlet of the first serpentine channel and a hot flue gas outlet communicated with the channel outlet of the first serpentine channel. The hot flue gas inlet is for hot flue gas at a temperature of 150°C - 200°C to enter the first serpentine channel and indirectly exchange heat with the ammonium carbamate powder. The hot flue gas after heat exchange is discharged through the hot flue gas outlet.

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

[0012] In some embodiments, 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 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 first air outlet is communicated with the drying unit to convey the mixed gas after pressure stabilizing and cooling to the drying unit. The steam trap is arranged at the liquid discharge port and is used to discharge the condensed water generated by the cooling of the mixed gas.

[0013] In some embodiments, a plurality of baffle plates arranged at intervals are provided in the buffer tank, and the plurality of baffle plates define a second serpentine channel. The channel inlet of the second serpentine channel is communicated with the first air inlet, and the channel outlet of the second serpentine channel is communicated with the first air outlet.

[0014] In some embodiments, the drying unit includes a drying tower. A plurality of drying layers are arranged at intervals along the height direction of the drying tower. Desiccant particles are provided in each drying layer. The drying tower has a second air inlet and a second air outlet. The second air inlet is communicated with the first air outlet, and the second air outlet is communicated with the filtering unit. The mixed gas entering from the second air inlet is dried by multiple drying layers and then discharged through the second air outlet.

[0015] In some embodiments, the filtering unit includes a filtering tower. The filtering tower has a third air inlet and a third air outlet. The third air inlet is communicated with the second air outlet, and the third air outlet is communicated with the SCR denitration unit. A plurality of filtering layers are arranged at intervals along the height direction of the filtering tower. At least one of a membrane filter cartridge and a polyester filter cartridge is filled in the filtering layer. The mixed gas entering from the third air inlet is filtered by the filtering layer and then discharged through the third air outlet.

[0016] In some embodiments, the SCR denitration unit includes a reactor and a plurality of catalyst beds. The reactor and the plurality of catalyst beds are arranged at intervals along the height direction of the reactor in 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 denitrification system of a coal-fired power plant according to an embodiment of the present invention uses ammonium carbamate as the main denitrification 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 and moisture carried by dust generated during the processes of dissolution, dehydration, and filtration of ammonium carbamate on the denitrification process of the catalyst in the subsequent SCR denitrification unit. Compared with ammonia production from urea, the ammonia production efficiency of the ammonium carbamate denitrification agent in water solution is higher than that of ammonia production from urea. After calculation, under full load conditions, the ammonia production efficiency of the ammonium carbamate denitrification agent is increased by 8.6 - 22.8% compared with urea, with an average increase of about 15.7%, and the energy consumption for ammonia production from the solution of the new denitrification agent is reduced by 52.4 - 62.7%. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0020] REFERENCE SIGNS: 100, SCR flue gas denitrification system of a coal-fired power plant; 1, storage bin; 101, primary bin; 102, secondary bin; 103, feeder; 2, pyrolysis unit; 201, pyrolysis tower; 2011, discharge opening; 2012, drain opening; 2013, steam inlet; 2014, mixed gas outlet; 2015, hot flue gas inlet; 2016, hot flue gas outlet; 202, pyrolysis tube; 203, partition; 204, first serpentine channel; 205, disc distributor; 3, pressure stabilizing unit; 301, buffer tank; 3011, first air inlet; 3012, first air outlet; 3013, liquid discharge port; 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, filtration unit; 501, filtration tower; 5011, third air inlet; 5012, third air outlet; 502, filtration layer; 6, SCR denitrification unit; 601, reactor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0022] As Figure 1 and Figure 2As shown in the figure, the SCR flue gas denitration system 100 of a coal-fired power plant according to an embodiment of the present invention includes a storage bin 1, a pyrolysis unit 2, a pressure stabilization unit 3, a drying unit 4, a filtration unit 5, and an SCR denitration unit 6. The storage bin 1 is used to store ammonium carbamate powder. The pyrolysis unit 2 includes a pyrolysis tower 201 which has a material discharge port 2011, a drainage port 2012, a steam inlet 2013, and a mixed gas outlet 2014. The material discharge port 2011 is communicated with the storage bin 1.

[0023] A plurality of pyrolysis tubes 202 extending in the vertical direction are arranged in the pyrolysis tower 201. The steam inlet 2013 is for superheated steam to enter and pass through the pyrolysis tubes 202 together with the ammonium carbamate powder entering from the material discharge port 2011 and fall to the bottom of the pyrolysis tower 201. The ammonium carbamate powder and the superheated steam exchange heat and pyrolyze in the pyrolysis tubes 202 to generate a mixed gas of ammonia and carbon dioxide. The mixed gas generated by pyrolysis is discharged through the mixed gas outlet 2014, and the condensed water generated by pyrolysis is discharged through the drainage port 2012.

[0024] The pressure stabilization unit 3 is communicated with 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 communicated with the pressure stabilization unit 3 and is used to dry the mixed gas which is pressure-stabilized and temperature-reduced and discharged from the pressure stabilization unit 3. The filtration unit 5 is communicated with the drying unit 4 and is used to filter the desiccant in the mixed gas discharged from the drying unit 4. The SCR denitration unit 6 is communicated with the filtration unit 5 and is used to receive the mixed gas discharged from the filtration unit 5 to reduce nitrogen oxides in the flue gas to nitrogen and water.

[0025] When the SCR flue gas denitration system 100 of a coal-fired power plant according to an embodiment of the present invention is in use, the storage bin 1 is used to store ammonium carbamate powder. This kind of powder can be stored stably at normal temperature, reducing the need for high-temperature storage, thereby reducing energy consumption and storage costs.

[0026] The ammonium carbamate powder enters the pyrolysis tower 201 of the pyrolysis unit 2 from the storage bin 1 through the material discharge port 2011. A plurality of pyrolysis tubes 202 extending vertically are arranged in the pyrolysis tower 201, and these pyrolysis tubes 202 are connected to the bottom of the tower to ensure that the ammonium carbamate powder falls evenly in the pyrolysis tower 201. The superheated steam is introduced into the pyrolysis tubes 202 through the steam inlet 2013 and mixed with the falling ammonium carbamate powder. In the pyrolysis tubes 202, the ammonium carbamate directly exchanges heat with the superheated steam and undergoes a pyrolysis reaction to generate a mixed gas of ammonia and carbon dioxide. The mixed gas generated by pyrolysis is discharged from the mixed gas outlet 2014, while the condensed water is discharged from the drainage port 2012.

[0027] The generated mixed gas undergoes pressure stabilization and cooling treatment through the pressure stabilization unit 3 to ensure that the mixed gas reaches an appropriate pressure and temperature before entering the SCR denitration unit 6, avoiding damage to the SCR catalyst. The mixed gas undergoes drying treatment in the drying unit 4 to remove the moisture therein, preventing the generation of liquid water during the SCR reaction and affecting the denitration efficiency. The filtration unit 5 is used to remove particulate matters such as desiccants in the mixed gas, preventing these particulate matters from entering the SCR denitration unit 6 and affecting the activity and lifespan of the catalyst. The filtered mixed gas is sent into the SCR denitration unit 6, where ammonia gas as a reducing agent undergoes a chemical reaction with nitrogen oxides in the flue gas under the action of the catalyst, reducing the nitrogen oxides to harmless nitrogen gas and water.

[0028] Thus, the SCR flue gas denitration system 100 of the coal-fired power plant in the embodiment 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 moisture and dust carried by ammonia gas generated during the processes of dissolving, dehydrating, and filtering ammonium carbamate on the denitration process of the catalyst in the subsequent SCR denitration unit 6. Compared with ammonia production from urea, the ammonia production efficiency of the ammonium carbamate denitration agent in water solution 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 8.6 - 22.8% compared with urea, with an average increase of about 15.7%, and the energy consumption for ammonia production from the solution of the new denitration agent is reduced by 52.4 - 62.7%.

[0029] 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 pyrolysis unit 2. A drying groove for storing the 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.

[0030] 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 it is responsible for uniformly and continuously conveying the ammonium carbamate powder from the secondary bin 102 to the pyrolysis unit 2 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 role 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 2, and the generated ammonia mixture gas has better quality, which is beneficial to more effectively reducing nitrogen oxides in the SCR denitration unit 6.

[0031] Optionally, the temperature of the superheated steam is 240°C - 320°C, and the pressure is 0.05 MPa - 0.5 MPa.

[0032] Within this temperature range, ammonium carbamate can effectively undergo a pyrolysis reaction to generate ammonia and carbon dioxide. An appropriate temperature can ensure the reaction rate and conversion rate, thereby improving the denitration efficiency of the entire system. The selected temperature range avoids excessive energy consumption. If the temperature is too low, it may lead to incomplete pyrolysis reaction, affecting the denitration effect; while too high a temperature may increase energy consumption, resulting in unnecessary cost waste. This temperature range will not cause excessive thermal stress on the materials of equipment such as the pyrolysis tower 201 and the pyrolysis tube 202, which helps to extend the service life of the equipment.

[0033] The selection of pressure helps to control the phase state of the superheated steam, ensure the full mixing of the steam with the ammonium carbamate powder in the pyrolysis tube 202, and effectively transfer heat. Low pressure helps to reduce the risk of equipment corrosion caused by high temperature and high pressure, thereby reducing the maintenance cost. Within the pressure range of 0.05 MPa - 0.5 MPa, superheated steam can be obtained more economically without high-pressure steam generation equipment, which can reduce the investment cost of the system. Controlling within a lower pressure range also helps to improve the safety performance of the system and reduce the safety risk caused by abnormal pressure.

[0034] By selecting the superheated steam temperature of 240°C - 320°C and the pressure of 0.05 MPa - 0.5 MPa, the present invention not only ensures the pyrolysis efficiency of ammonium carbamate but also takes into account the energy consumption, safety, and economy of the system operation.

[0035] In some embodiments, a plurality of partition plates 203 are provided on the inner wall of the pyrolysis tower 201 at intervals along its height direction. The partition plates 203 have perforations through which the pyrolysis tubes 202 pass, and the plurality of partition plates 203 form a first serpentine channel 204. The pyrolysis tower 201 further has a hot flue gas inlet 2015 communicating with the channel inlet of the first serpentine channel 204 and a hot flue gas outlet 2016 communicating with the channel outlet of the first serpentine channel 204. The hot flue gas inlet 2015 is for hot flue gas at a temperature of 150°C - 200°C to enter the first serpentine channel 204 and indirectly exchange heat with the ammonium carbamate powder, and the heat-exchanged hot flue gas is discharged through the hot flue gas outlet 2016.

[0036] 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, and at the same time improve the thermal efficiency. Through the serpentine flow of the hot flue gas and the setting of the partition plates 203, the heat exchange area is increased, the heat exchange efficiency is improved, and it helps the rapid pyrolysis of ammonium carbamate. Using the waste heat of the hot flue gas for the pyrolysis of ammonium carbamate can reduce the input of additional heat energy and lower the energy consumption of the system. After the temperature of the heat-exchanged flue gas decreases, it enters the flue gas exhaust system of the coal-fired power plant for treatment.

[0037] In some embodiments, a disk distributor 205 is provided in the pyrolysis tower 201 between the feeding port 2011 and the pyrolysis tubes 202. The disk distributor 205 is used to evenly distribute the ammonium carbamate powder entering from the feeding port 2011 to different pyrolysis tubes 202.

[0038] The main function of the disk distributor 205 is to evenly distribute the ammonium carbamate powder entering from the feeding port 2011 into a plurality of pyrolysis tubes 202, ensuring that each pyrolysis tube 202 receives an equal amount of powder, thereby avoiding the situation of some pyrolysis tubes 202 being overloaded or underloaded. Evenly distributing the powder can ensure that the pyrolysis efficiency of each pyrolysis tube 202 remains consistent and improve the operating efficiency of the entire pyrolysis tower 201. Through even distribution, the blockage problem caused by excessive powder in some pyrolysis tubes 202 can be reduced, thereby ensuring the continuity and stability of the pyrolysis process.

[0039] In some embodiments, the pressure stabilizing unit 3 includes a buffer tank 301 and a steam trap 302. The buffer tank 301 has a first air inlet 3011, a first air outlet 3012, and a liquid discharge port 3013. The first air inlet 3011 communicates with the mixed gas outlet 2014 to stabilize the pressure and cool the mixed gas discharged from the mixed gas outlet 2014 to 20°C - 30°C. The first air outlet 3012 communicates with the drying unit 4 to convey the pressure-stabilized and cooled mixed gas to the drying unit 4. The steam trap 302 is provided at the liquid discharge port 3013 for discharging the condensed water generated by the cooling of the mixed gas.

[0040] The buffer tank 301 is the core part of the pressure stabilizing unit 3, and it has a first air inlet 3011 and a first air outlet 3012. The first air inlet 3011 is communicated with the mixed gas outlet 2014 to receive the mixed gas from the pyrolysis unit 2; the first air outlet 3012 then conveys the mixed gas after pressure stabilizing and temperature reducing to the drying unit 4.

[0041] Before the mixed gas in the buffer tank 301 enters the drying unit 4, it needs to be cooled down to 20°C - 30°C. This temperature range is beneficial to the subsequent drying process and helps to reduce the volatilization of ammonia, improving 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 receive the mixed gas stably. The steam trap 302 is arranged at the drain port 3013 of the buffer tank 301 and is used to discharge the condensed water generated during the temperature reduction of the mixed gas. These condensed waters may contain incompletely reacted ammonium carbamate or other impurities, so they need to be discharged regularly. Discharging the condensed water can prevent the impurities in the condensed water from contaminating the subsequent drying process and the SCR denitration unit 6.

[0042] The design of the pressure stabilizing unit 3 ensures that the mixed gas reaches a stable pressure and temperature before entering the drying unit 4, improving the stability and reliability of the system. Through pressure stabilizing and temperature reducing treatment, the mixed gas is more stable when entering the drying unit 4, which is beneficial to the stable operation of the drying unit 4 and the improvement of the drying efficiency. Reducing the temperature of the mixed gas helps to reduce the volatilization of ammonia, improve the safety of the system, and avoid the environmental and safety risks brought by ammonia leakage. Discharging the condensed water through the steam trap 302 can reduce the pollution to the subsequent process and improve the operation efficiency of the whole system.

[0043] In some embodiments, a plurality of baffle plates 303 arranged at intervals are provided in the buffer tank 301, and the plurality of baffle plates 303 define a second serpentine channel 304. The channel inlet of the second serpentine channel 304 is communicated with the first air inlet 3011, and the channel outlet of the second serpentine channel 304 is communicated with the first air outlet 3012.

[0044] As Figure 2 shown, the design of the baffle plate 303 increases the air flow path in the buffer tank 301, forms a serpentine channel, thereby increasing the contact area between the mixed gas and the baffle plate 303 and improving the heat exchange efficiency. Through the serpentine channel, the mixed gas turns multiple times in the buffer tank 301, extending the residence time of the mixed gas in the buffer tank 301 and making the heat exchange between the mixed gas and the inner wall surface of the tank more sufficient. The design of the baffle plate 303 helps to better control the temperature and pressure of the mixed gas and ensure that the mixed gas reaches the predetermined temperature and pressure conditions before entering the drying unit 4.

[0045] In some embodiments, the drying unit 4 includes a drying tower 401. Inside the drying tower 401, a plurality of drying layers 402 are arranged at intervals along its height direction, and desiccant particles are provided in each drying layer 402. The drying tower 401 has a second air inlet 4011 and a second air outlet 4012. The second air inlet 4011 is communicated with the first air outlet 3012, and the second air outlet 4012 is communicated with the filtering unit 5. The mixed gas entering through the second air inlet 4011 is dried by the multi-layer drying layers 402 and then discharged through the second air outlet 4012.

[0046] The second air inlet 4011 is communicated with the first air outlet 3012 of the voltage stabilizing unit 3 to receive the mixed gas from the voltage stabilizing unit 3; the second air outlet 4012 is communicated with the filtering unit 5 to transport the dried mixed gas to the filtering unit 5. After the mixed gas from the voltage stabilizing unit 3 enters the drying tower 401, it will pass through multiple drying layers 402. The desiccant particles in each drying layer 402 will absorb the moisture in the mixed gas, thereby drying the mixed gas.

[0047] Through the design of the multi-layer drying layers 402, the mixed gas is sufficiently dried in the drying tower 401, ensuring the stable operation of the subsequent SCR denitration unit 6. The design of the multi-layer drying layers 402 helps to optimize the drying process, ensuring that the residence time of the mixed gas in the drying tower 401 is long enough to improve the drying effect. By sufficiently drying the mixed gas, the volatilization of ammonia in the denitration unit can be reduced, enhancing the stability of the system.

[0048] In some embodiments, the filtering unit 5 includes a filtering tower 501. The filtering tower 501 has a third air inlet 5011 and a third air outlet 5012. The third air inlet 5011 is communicated with the second air outlet 4012, and the third air outlet 5012 is communicated with the SCR denitration unit 6. Inside the filtering tower 501, a plurality of filtering layers 502 are arranged at intervals along its height direction. At least one of a membrane filter cartridge and a polyester filter cartridge is filled in the filtering layer 502. The mixed gas entering through the third air inlet 5011 is filtered by the filtering layer 502 and then discharged through the third air outlet 5012.

[0049] After the mixed gas from the drying unit 4 enters the filtering tower 501, it will pass through multiple filtering layers 502. The filter cartridges in each filtering layer 502 will filter the desiccant particles and other impurities in the mixed gas to ensure the cleanliness of the mixed gas. The design of the filtering layer 502 can enable the mixed gas to pass through the filter cartridges multiple times in the filtering tower 501, thereby ensuring that the impurities are fully filtered. The membrane filter cartridge and the polyester filter cartridge are key components of the filtering layer 502, and they can effectively filter the desiccant particles and other impurities to ensure the cleanliness of the mixed gas before entering the SCR denitration unit 6.

[0050] In some embodiments, the SCR denitration unit 6 includes a reactor 601 and a plurality of catalyst beds. The reactor 601 and the plurality of catalyst beds are arranged in the reactor 601 at intervals along the height direction of the reactor 601. The ratio of the distance between two adjacent catalyst beds to the diameter of the reactor 601 is 5 - 10.

[0051] The layout of the plurality of 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 spacing between the catalyst beds optimizes the hydrodynamic conditions inside the reactor 601, enabling the mixed gas to be evenly distributed inside the reactor 601, avoiding gas flow dead zones or excessive turbulence, thereby improving the stability of the system and the denitration efficiency. An appropriate spacing between the catalyst beds 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 6 can be improved, and the system fluctuations caused by uneven gas flow distribution can be reduced. By improving the reduction efficiency of nitrogen oxides and 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.

[0052] Optionally, the catalytic denitration reaction temperature in the SCR denitration unit 6 is controlled at 300°C - 400°C.

[0053] 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, 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 thus should not be construed as a limitation of the present invention.

[0054] 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, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0055] In the present invention, unless otherwise clearly defined or limited, terms such as "installed", "connected", "linked", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or communicable with each other; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside 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.

[0056] In the present invention, unless otherwise clearly defined or limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0057] In the present invention, terms such as "one embodiment", "some embodiments", "examples", "specific examples", 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 descriptions 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 a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0058] 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. A selective catalytic reduction (SCR) flue gas denitrification system for coal-fired power plants, characterized in that, Comprising: A storage bin for storing ammonium carbamate powder. A pyrolysis unit, the pyrolysis unit includes a pyrolysis tower, the pyrolysis tower has a feeding port, a drainage port, a steam inlet and a mixed gas outlet, the feeding port is communicated with the storage bin, a plurality of pyrolysis tubes extending in the vertical direction are arranged in the pyrolysis tower, the steam inlet is for superheated steam to enter and pass through the pyrolysis tubes with the ammonium carbamate powder entering from the feeding port to the bottom of the pyrolysis tower, the ammonium carbamate powder and the superheated steam exchange heat and pyrolyze in the pyrolysis tubes to generate a 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 drainage port. A voltage stabilizing unit communicated with the mixed gas outlet for stabilizing the voltage and cooling the mixed gas discharged from the pyrolysis unit. A drying unit communicated with the voltage stabilizing unit for drying the mixed gas after voltage stabilization and cooling discharged from the voltage stabilizing unit. A filtering unit communicated with the drying unit for filtering the desiccant in the mixed gas discharged from the drying unit. An SCR denitration unit communicated with the filtering unit for receiving the mixed gas discharged from the filtering unit to reduce nitrogen oxides in the flue gas to nitrogen and water.

2. The SCR flue gas denitration system of a coal-fired power plant according to claim 1, wherein The storage bin includes a primary bin, a secondary bin and a feeder. The primary bin is communicated 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 is communicated with the pyrolysis unit. A drying tank for storing a first desiccant is arranged on the inner wall of at least one of the primary bin and the secondary bin, and the first desiccant is used for drying ammonium carbamate powder.

3. The SCR flue gas denitration system for coal-fired power plants according to claim 1, wherein The temperature of the superheated steam is 240°C - 320°C, and the pressure is 0.05MPa - 0.5MPa.

4. The SCR flue gas denitration system for coal-fired power plants according to claim 1, characterized in that, A plurality of partitions are arranged on the inner wall of the pyrolysis tower 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 also has a hot flue gas inlet communicated with the channel inlet of the first serpentine channel and a hot flue gas outlet communicated with the channel outlet of the first serpentine channel. The hot flue gas inlet is for hot flue gas at a temperature of 150°C - 200°C to enter the first serpentine channel and indirectly exchange heat with the ammonium carbamate powder, and the hot flue gas after heat exchange is discharged through the hot flue gas outlet.

5. The SCR flue gas denitration system for coal-fired power plants according to claim 1, wherein A disc distributor is arranged in the pyrolysis tower between the feeding port and the pyrolysis tubes, and the disc distributor is used for evenly distributing the ammonium carbamate powder entering from the feeding port to different pyrolysis tubes.

6. The SCR flue gas denitration system for coal-fired power plants according to claim 1, wherein, 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 first air outlet is communicated with the drying unit to convey the mixed gas with stabilized pressure and reduced temperature to the drying unit. 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.

7. The SCR flue gas denitration system for coal-fired power plants according to claim 6, characterized in that, A plurality of baffle plates arranged at intervals are provided in the buffer tank. The plurality of baffle plates define a second serpentine channel. The channel inlet of the second serpentine channel is communicated with the first air inlet, and the channel outlet of the second serpentine channel is communicated with the first air outlet.

8. The SCR flue gas denitration system for coal-fired power plants according to claim 7, wherein The drying unit includes a drying tower. A plurality of drying layers are arranged at intervals along the height direction of the drying tower. Desiccant particles are provided in each drying layer. The drying tower has a second air inlet and a second air outlet. The second air inlet is communicated with the first air outlet, and the second air outlet is communicated with the filtering unit. The mixed gas entering through the second air inlet is discharged through the second air outlet after being dried by multiple drying layers.

9. The SCR flue gas denitration system for a coal-fired power plant according to claim 8, characterized in that The filtering unit includes a filtering tower. The filtering tower has a third air inlet and a third air outlet. The third air inlet is communicated with the second air outlet, and the third air outlet is communicated with the SCR denitration unit. A plurality of filtering layers are arranged at intervals along the height direction of the filtering tower. At least one of a film filter cartridge and a polyester filter cartridge is filled in the filtering layer. The mixed gas entering through the third air inlet is discharged through the third air outlet after being filtered by the filtering layer.

10. The SCR flue gas denitration system for coal-fired power plants according to claim 9, wherein The SCR denitration unit includes a reactor and a plurality of catalyst beds. The reactor and the plurality of catalyst beds are arranged at intervals along the height direction of the reactor in 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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