A flue gas treatment system and method for breaking the side wall effect in a tower to improve the removal efficiency of pollutants

Abstract

The application discloses a flue gas treatment system and method for breaking tower inner side wall effect and improving pollutant removal efficiency, which is arranged on a desulfurization tower and connected with the desulfurization tower. The flue gas treatment system comprises a material circulation system and a removal system. The material circulation system comprises a side wall breaking ring, a turbulence recirculation device, a material backflow device, a plug door and a material backflow hopper. The side wall breaking ring, the turbulence recirculation device, the material backflow device and the material backflow hopper simultaneously serve as gas-solid enhanced mass transfer devices, increase the contact opportunity of dust in flue gas and desulfurizing agent, prolong the residence time of the desulfurizing agent in the desulfurization tower, reduce the dust concentration entering a bag-type dust collector, and are higher in desulfurization efficiency and dust removal efficiency than a CFB desulfurization process, and are high in desulfurizing agent utilization rate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of flue gas treatment, and more particularly, to a flue gas treatment system and method for breaking the edge effect in the tower to improve the removal efficiency of pollutants. BACKGROUND

[0002] After the "ultra-low emission" transformation, the flue gas pollutant emission reduction effect of coal-fired power plants is remarkable, setting an example for other non-electricity industries to implement "ultra-low emission" flue gas treatment. For example, in the coking field, the standards for ultra-low emission have been gradually implemented. In particular, some provinces and cities, such as Hebei Province, Shandong Province, Jiangsu Province, etc., have introduced corresponding local standards, and some indicators are higher than the national standards or European Union standards, requiring to meet the standards for ultra-low emission. In particular, Hebei Province is a major coking province, with coke production ranking second in the country, and the coking capacity in the province exceeds 100 million tons. In order to improve the regional environmental quality and respond to the call of the state to govern air pollution, in April 2018, Hebei issued the "Coke Chemical Industry Air Pollutant Emission Standard (Draft for Comments)", which will be implemented from October 1, 2019. In the Hebei Provincial Standard, the emission limits of particulate matter, SO2, and NOx from coke oven chimneys are set at 10 mg / m3, 15 mg / m3, and 100 mg / m3, respectively, and the SO2 emission index is more stringent than the current ultra-low emission limit value of SO2≤35 mg / m3 for coal-fired power plants.

[0003] At present, the process route for flue gas treatment in the coking industry mainly includes: SDS + dust removal + SCR; SCR denitration + waste heat recovery + dry desulfurization + dust removal (pre-denitration); low-temperature SCR denitration + ammonia desulfurization + flue gas reheating; SDA desulfurization + SCR denitration technology, etc. Among them, the process route of SDS + dust removal + SCR is more commonly used.

[0004] However, there are problems in the dry desulfurization of coke oven flue gas:

[0005] 1. Low utilization rate of desulfurizer, high price of desulfurizer, and high operating cost. The desulfurizer uses NaHCO3 to generate Na2SO4, which is dissolved in water. The storage area needs to be waterproof and needs to be disposed of harmlessly;

[0006] 2. The dust concentration in the desulfurized flue gas is high, and it needs to be filtered by high-concentration dust and high-temperature-resistant membrane bag, which requires high performance indicators of the filter bag;

[0007] 3. The quality of domestic desulfurizer and grinding equipment is not up to standard, the fineness of grinding is unstable, and the heat generated during grinding causes equipment blockage, which affects the normal and stable operation of desulfurization.

[0008] Therefore, the application discloses a novel reactor for treating coke oven flue gas, and a dry desulfurization and denitrification process, so as to provide a flue gas desulfurization and denitrification dust removal integrated system which is free of wastewater generation, has dry flowability of powder desulfurization byproducts, low overall investment cost and low system energy consumption, and uses high-performance Ca(OH)2 as a desulfurizer. SUMMARY

[0009] In view of the above defects or improvement needs of the prior art, the application provides a flue gas treatment system for breaking the edge effect in a tower and improving the pollutant removal efficiency, which breaks the edge effect in the tower, enhances recirculation, improves the utilization rate of a desulfurizer, reduces the dust concentration at the inlet of a dust remover to improve the dust removal efficiency, and removes denitrification, deacidification, dust removal, heavy metal removal and dioxin from coking flue gas, coal-fired boiler flue gas, pellet flue gas and solid waste treatment flue gas. The system is free of a reheating system, white smoke plume, catalyst consumption, has low overall investment cost and low system energy consumption.

[0010] In order to achieve the above-mentioned purpose, according to the first aspect of the application, a flue gas treatment system for breaking the edge effect in a tower and improving the pollutant removal efficiency is provided.

[0011] The flue gas treatment system is arranged on the desulfurization tower and connected with the desulfurization tower.

[0012] The flue gas treatment system comprises a material circulation system and a removal system.

[0013] The material circulation system comprises an edge breaking ring, a turbulence recirculation device, a material backflow device, a plug door and a material backflow hopper.

[0014] The edge breaking ring is arranged in a reaction section of the desulfurization tower, the turbulence recirculation device is arranged at the top of the desulfurization tower, the material backflow device is arranged at the flue gas outlet at the top of the desulfurization tower, flue gas flowing out of the top of the desulfurization tower enters the material backflow device and the material backflow hopper, and the material backflow device is provided with the plug door at the inlet, connected with a diffusion and sedimentation section and a reaction and sedimentation cylinder, and the plug door at the outlet can be closed or opened according to needs.

[0015] The removal system reserves and supplies a flue gas heavy metal and dioxin removal agent and a desulfurizer, and comprises an activated carbon storage bin and a pneumatic conveying device.

[0016] Further, the removal system comprises a desulfurizer storage bin, a first rotary feeding valve, a flue gas heavy metal and dioxin removal agent storage bin, a second rotary feeding valve, a denitrification agent storage tank and a denitrification agent conveying pump.

[0017] The desulfurizer storage bin is connected with the desulfurization tower through the first rotary feeding valve at the bottom of the bin, the flue gas heavy metal and dioxin removal agent storage bin is connected with the desulfurization tower through the rotary feeding valve at the bottom of the bin, and the denitrification agent storage tank is connected with a pipeline between the material backflow device and the dust remover through the denitrification agent conveying pump.

[0018] Further, the material return hopper bottom is provided with a third rotary feeder valve, and is connected with the dust collector bottom material return device through the rotary feeder valve; the material return device is connected with the desulfurization tower through a flow regulating valve, and a fourth rotary feeder valve at the lower part of the material return device is connected with the desulfurization byproduct bin;

[0019] The desulfurization tower is provided with one or more outlets according to the flue gas treatment capacity of the desulfurization tower, the size of the flue gas outlet, and the flue gas flow rate, each outlet is provided with a plug-in door, and a material return device is further connected; the outlet of the material return device is connected with the dust collector, and the dust collector is connected with the chimney; when a fault occurs in any unit of the dust collector, the plug-in door on the corresponding material return device can be closed to realize online maintenance of the bag-type dust collector.

[0020] Further, the edge wall breaking ring is a one-stage or multi-stage arc plate, and a row of "V"-shaped, inverted triangular, uniformly distributed hole-shaped or rectangular openings, etc. are arranged on the outer edge of the arc plate and are perpendicular to the arc plate; the edge wall breaking ring adopts a carbon steel structure, the thickness of the carbon steel is 10-20 mm, and the width range is 500-800 mm. The edge wall breaking ring is arranged from the connection between the conical section and the straight section of the desulfurization tower, the included angle between the edge wall breaking ring and the horizontal plane is about 30 degrees, and the connection between the edge wall breaking ring and the desulfurization tower is by welding, the welding mode is full welding on both sides, and the edge wall breaking ring rises spirally along the straight section of the desulfurization tower (80) and is connected with the turbulence recirculation device (82) at the top of the tower. The edge wall breaking ring flue gas rectifier grid can be arranged in different shapes according to different working conditions or different requirements of the actual project on the flue gas flow field, such as the inverted triangular opening, the top angle of the inverted triangle is 250, the height is 200 mm, and the inverted triangular openings are uniformly arranged on the side of the edge wall breaking ring away from the desulfurization tower wall. The uniformly distributed hole-shaped rectifier grid is provided with a certain number of openings, and the diameter size, arrangement mode and opening rate of the openings can be adjusted.

[0021] The number of the edge wall breaking rings can be one stage or multiple stages according to the size of the desulfurization tower.

[0022] Further, a blind area with a certain height is arranged at the outlet of the desulfurization tower and at the top, the turbulence recirculation device is arranged in the blind area, is fixed at the top of the desulfurization tower, and has a spiral rotating tubular structure to hinder the flow of flue gas; under the action of the turbulence recirculation device at the top, the upward flue gas carries dust and desulfurizing agent to rotate and descend at the top of the desulfurization tower, thereby increasing the residence time of the desulfurizing agent in the desulfurization tower and improving the utilization rate of the desulfurizing agent.

[0023] Further, the material return device and the material return hopper are connected with the dust collector.

[0024] The material backflow device is connected with the desulfurization tower, and the material backflow device is provided with at least one stage, and multiple stages can be provided according to the size of the flue gas. The material backflow device is provided with a rectangular or square flue at each inlet, and a flue gas baffle door is arranged on the regular-shaped flue. The baffle door is controlled to be opened or closed by using a pneumatic or electric actuator. The transmission mechanism of the actuator is vertically upward, and maintenance can be performed on the top platform of the desulfurization tower. After the material backflow device passes through the regular-shaped flue, the bottom plate of the flue is inclined to the diffusion settling section with an angle greater than 60 degrees, and the dust deposited on the bottom plate can slide into the material backflow hopper due to the sufficient inclination angle. The diffusion settling section has two effects: one is to reduce the flow rate of the flue gas, so that the flow rate of the flue gas carrying dust particles is reduced, and the initial conditions for natural settling are created; the other is to increase the contact time of the flue gas and the dust and desulfurizing agent mixture, and further reaction in the material backflow device to remove acidic pollutants. The diffusion settling section of the material backflow device is irregularly rectangular, and the back is connected with a cylindrical reaction settling cylinder. The dust passing through the diffusion settling and reaction settling enters the conical material backflow hopper, and a circular or square material conveying interface is arranged at the bottom of the backflow hopper.

[0025] Further, the heavy metal and dioxin removal agent storage bin is connected with the dust collector through a No. 2 rotary feeding valve at the bottom of the bin; the No. 3 rotary feeding valve at the bottom of the material backflow hopper is connected with a backflow device at the bottom of the dust collector; a flow regulating valve of the backflow device is connected with the desulfurization tower; and a rotary feeding valve of the backflow device is connected with a desulfurization byproduct bin.

[0026] Further, the material backflow system further comprises a recirculation valve and a recirculation air chute; the recirculation valve is arranged on a pipeline connected with the bottom of the dust collector and the desulfurization tower; the chute is arranged in a pipeline connected with the recirculation valve and the bottom of the desulfurization tower, and the recirculation chute returns the material in the dust collector to the absorption tower; the recirculation valve controls the flow of the material returned to the absorption tower by the recirculation chute;

[0027] The flue gas treatment system further comprises a dust collector system, and the dust collector system is provided with a bag dust collector or a ceramic tube dust collector.

[0028] The desulfurizing agent is Ca(OH)2 desulfurizing agent.

[0029] According to another aspect of the present application, a flue gas treatment method for breaking the edge effect in the tower and improving the removal efficiency of pollutants is provided, which is realized by using the flue gas treatment system for breaking the edge effect in the tower and improving the removal efficiency of pollutants according to any one of the above.

[0030] S100: The flue gas of the flue gas treatment system is drawn from the coke oven or the boiler or the pellet, the flue gas enters the desulfurization tower from the bottom, flows out from the side of the top of the tower and enters the material backflow device; the pollutants in the flue gas are removed by reaction in the desulfurization tower and the material backflow device, and the particulate matters in the flue gas are removed by entering the dust collector; after the removal of the pollutants and the particulate matters, the flue gas is discharged into the atmosphere through the chimney;

[0031] S200: The material of the material circulation system, including the mixture of dust, desulfurizer, desulfurization by-products and the like, is carried into the desulfurization tower from the flue gas drawn from the coke oven or the boiler or the pellet, the desulfurizer enters the desulfurization tower, and the flue gas heavy metal and dioxin removal agent are added into the material backflow device; the flue gas system carries part of the mixture to deposit in the material backflow hopper, and the other part is collected in the dust collector; the mixture collected through the material backflow hopper and the dust collector is returned to the absorption tower through the back material device for the next circulation backflow;

[0032] S300: The excess material that needs to be discharged in the material circulation system, part of which is discharged to the desulfurization by-product bin through the bottom of the desulfurization tower, and the other part is discharged to the desulfurization by-product bin through the No. 4 rotary feeding valve at the lower part of the back material device.

[0033] Further, the dust collector is in communication with the denitration agent storage tank, the denitration agent in the denitration agent storage tank is NaClO2, and the denitration agent is introduced into the dust collector through the pipeline.

[0034] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0035] 1. The edge wall breaking ring, the turbulence recirculation device, the material backflow device and the material backflow hopper of the present application simultaneously serve as gas-solid enhanced mass transfer devices, increase the contact opportunity of the dust in the flue gas and the desulfurizer, prolong the residence time of the desulfurizer in the desulfurization tower, reduce the dust concentration entering the bag-type dust collector, and have higher desulfurization efficiency and dust removal efficiency than the CFB desulfurization process, and have high utilization rate of the desulfurizer.

[0036] 2. The application sets material backflow device, dust in flue gas is settled by natural sedimentation to material backflow hopper before entering dust remover, reduces the content of dust in flue gas, reduces the operation load of dust remover, and the dust removal efficiency of dust remover is higher. Heavy metal, dioxin removal agent and denitration agent are arranged between material backflow device and dust remover inlet. Compared with the configuration without material backflow device, the dust concentration entering the bag is lower due to the natural sedimentation of dust through the material backflow device, the wrapping of heavy metal, dioxin removal agent and denitration agent by dust is reduced, the effective use rate of heavy metal, dioxin removal agent and denitration agent is higher, the removal efficiency of heavy metal and dioxin is higher, and the use amount of heavy metal, dioxin removal agent and denitration agent is smaller, so that the operation cost is reduced. Compared with the CFB desulfurization tower, the material backflow device of the application has two functions. One is to backflow desulfurizer and increase the use efficiency of desulfurizer. The system resistance increase can be ignored without adjusting the bed layer differential pressure of desulfurization tower. The other is to make the dust carried in flue gas freely settle.

[0037] 3. The reaction process of the application has no temperature drop, the desulfurization product is neutral substance, belongs to general solid waste, and is beneficial to resource utilization. The matching desulfurizer feeding system is fully closed conveying, and there is no dust emission on site.

[0038] 4. Compared with the CFB desulfurization tower, the application reduces the elevation of the desulfurization tower outlet through the material backflow device, the elevation of the dust remover connected with the desulfurization tower is correspondingly reduced, and the support of the dust remover is correspondingly reduced, so that the one-time investment cost is reduced.

[0039] 5. The application breaks the problems of uneven flow field in the traditional dry desulfurization tower, uneven contact between flue gas and desulfurizer, insufficient reaction, and low utilization rate of desulfurizer. The dry desulfurization tower is used for desulfurization, the desulfurizer backflow device is arranged at the outlet of the dry desulfurization tower, the desulfurizer which has not completed the reaction is returned to the desulfurization tower for repeated use, so that the utilization rate of desulfurizer is improved on the one hand, and the dust load entering the dust remover is reduced on the other hand, the working load of the dust remover is reduced, and the dust emission standard is beneficial to the dust emission standard. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 It is a kind of flue gas treatment system for breaking tower wall effect and improving pollutant removal efficiency of the embodiment of the application;

[0041] Figure 2 It is a kind of desulfurization tower structure diagram of the flue gas treatment system for breaking tower wall effect and improving pollutant removal efficiency of the embodiment of the application;

[0042] Figure 3 It is a kind of desulfurization tower and dust remover connection mode diagram of the flue gas treatment system for breaking tower wall effect and improving pollutant removal efficiency of the embodiment of the application.

[0043] In all the drawings, the same reference signs denote the same technical features, specifically: 10 - coke oven or boiler or pellet, 20 - desulfurizer storage bin, 21 - first rotary feeder valve, 30 - heavy metal-dioxin removal agent storage bin, 31 - second rotary feeder valve, 40 - denitration agent storage tank, 41 - denitration agent delivery pump, 60 - third rotary feeder valve, 70 - flow regulating valve, 71 - fourth rotary feeder valve, 72 - backflow device, 75 - desulfurization byproduct bin, 80 - desulfurization tower, 81 - side wall breaking ring, 82 - turbulence recirculation device, 83 - material backflow device, 84 - plug door, 85 - material backflow hopper, 86 - diffusion settling section, 87 - reaction settling section, 90 - dust collector, 95 - chimney. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0045] Please refer to Figure 1 and Figure 2 A flue gas treatment system for breaking the side wall effect in a tower to improve the removal efficiency of pollutants:

[0046] The flue gas treatment system is arranged on and connected to the desulfurization tower 80.

[0047] The flue gas treatment system comprises a material circulation system and a removal system.

[0048] The material circulation system comprises a side wall breaking ring 81, a turbulence recirculation device 82, a material backflow device 83, a plug door 84 and a material backflow hopper 85.

[0049] The side wall breaking ring 81 is arranged in the reaction section of the desulfurization tower 80, the turbulence recirculation device 82 is arranged at the top of the desulfurization tower 80, the material backflow device 83 is arranged at the flue gas outlet at the top of the desulfurization tower 80, and the flue gas flowing out of the top of the desulfurization tower 80 enters the material backflow device 83 and the material backflow hopper 85; the plug door 84 is arranged at the inlet of the material backflow device 83, and connects the diffusion settling section 86 and the reaction settling section 87, and the plug door at the outlet can be closed or opened according to the need.

[0050] The removal system stores and supplies heavy metal-dioxin removal agent and desulfurization agent, and comprises an activated carbon storage bin and a pneumatic conveying device.

[0051] The removal system comprises a desulfurizer storage bin 20, a first rotary feeder valve 21, a flue gas heavy metal and dioxin removal agent storage bin 30, a second rotary feeder valve 31, a denitration agent storage tank 40 and a denitration agent delivery pump 41.

[0052] The desulfurizer storage bin 20 is connected to the desulfurization tower 80 through the first rotary feeder valve 21 at the bottom of the bin, the flue gas heavy metal and dioxin removal agent storage bin 30 is connected to the desulfurization tower 80 through the rotary feeder valve 31 at the bottom of the bin, and the denitration agent storage tank 40 is connected to the pipeline between the material backflow device 83 and the dust collector 90 through the denitration agent delivery pump 41.

[0053] The bottom of the material backflow hopper 85 is provided with a third rotary feeder valve 60, and the third rotary feeder valve 60 is connected to the back material device 72 at the bottom of the dust collector 90; the back material device 72 is connected to the desulfurization tower 80 through the flow regulating valve 70, and the fourth rotary feeder valve 71 at the lower part of the back material device 72 is connected to the desulfurization byproduct bin 75.

[0054] Please refer to Figure 3 The desulfurization tower 80 is provided with one or more outlets according to the flue gas treatment capacity of the desulfurization tower, the size of the flue gas outlet, and the flue gas flow rate, each outlet is provided with a plug-in door 84, and then connected to the material backflow device 83; the outlet of the material backflow device 83 is connected to the dust collector 90, and the dust collector 90 is connected to the chimney 95; when any unit of the dust collector 90 fails, the plug-in door 84 on the corresponding material backflow device 83 can be closed to realize online maintenance of the bag-type dust collector.

[0055] The side wall breaking ring 81 is a first-stage or multi-stage arc plate, and a row of "V"-shaped, inverted triangular, uniformly distributed hole-shaped or rectangular openings, etc. are arranged on the outer edge of the arc plate and are perpendicular to the arc plate; the side wall breaking ring is made of carbon steel, the thickness of the carbon steel is 10-20 mm, and the width range is 500-800 mm. The side wall breaking ring is arranged from the connection between the conical section and the straight section of the desulfurization tower, the included angle between the side wall breaking ring and the horizontal plane is about 30 degrees, and the connection between the side wall breaking ring and the desulfurization tower is by welding, the welding method is full welding on both sides, and the side wall breaking ring rises spirally along the straight section of the desulfurization tower 80 and is connected to the turbulence recirculation device 82 at the top of the tower. The setting of the side wall breaking ring flue gas rectifier grid can correspondingly set different shapes according to different working conditions or different requirements of the actual project on the flue gas flow field, such as: the opening of the inverted triangular shape, the top angle of the inverted triangle is 250, the height is 200 mm, and the openings of the inverted triangular shape are uniformly arranged away from the side wall of the desulfurization tower. The uniformly distributed hole-shaped rectifier grid is provided with a certain number of openings, and the diameter size of the openings, the arrangement method of the openings and the opening rate can be adjusted.

[0056] The number of the side wall breaking ring 81 can be one stage or multiple stages according to the diameter of the desulfurization tower 80.

[0057] The outlet of the desulfurization tower 80 is connected with a blind area with a certain height at the top, the turbulence recirculation device 82 is arranged in the blind area and fixed at the top of the desulfurization tower 80, and is in a spiral rotating tubular structure to hinder the flow of flue gas; under the action of the turbulence recirculation device 82 at the top, the upward flowing flue gas carries dust and desulfurizing agent to swirl and descend at the top of the desulfurization tower 80, thereby increasing the residence time of the desulfurizing agent in the desulfurization tower 80 and improving the utilization rate of the desulfurizing agent.

[0058] The material recirculation device 83 and the material recirculation hopper 85 are connected with the dust collector 90.

[0059] The material recirculation device 83 is connected with the desulfurization tower 80, and the material recirculation device 83 is provided with at least one stage, and multiple stages can be provided according to the size of flue gas. Each inlet of the material recirculation device 83 has a section of rectangular or square flue, and a flue gas plug door is arranged on the regular-shaped flue. The plug door 84 is controlled to be opened or closed by using a pneumatic or electric actuator. The transmission mechanism of the actuator is vertically upward, and maintenance can be performed on the top platform of the desulfurization tower 80. After the material recirculation device 83 passes through a section of regular-shaped flue, the bottom plate of the flue is inclined to a diffusion settling section 86 with an angle greater than 60 degrees to the vertical direction, and the dust deposited on the bottom plate can slide to the material recirculation hopper 85 due to the sufficient inclination angle. The diffusion settling section 86 has two effects. One is to reduce the flow rate of flue gas, so that the flow rate of flue gas carrying dust particles is reduced, and the initial condition for natural settling is created. The other is to increase the contact time of flue gas, dust and desulfurizing agent mixture, and further reaction in the material recirculation device 83 to remove acidic pollutants. The diffusion settling section 86 of the material recirculation device 83 is irregularly rectangular in shape, and is connected with a cylindrical reaction settling cylinder 87 at the back. The dust after diffusion settling and reaction settling enters the conical material recirculation hopper 85, and a circular or square material conveying interface is arranged at the bottom of the recirculation hopper.

[0060] The heavy metal and dioxin removal agent storage bin 30 is connected with the dust collector 90 through the second rotary feeding valve 31 at the bottom; the third rotary feeding valve 60 at the bottom of the material recirculation hopper 85 is connected with the material return device 72 at the bottom of the dust collector 90; the flow regulating valve 70 of the material return device 72 is connected with the desulfurization tower 80; and the rotary feeding valve 71 of the material return device 72 is connected with the desulfurization byproduct bin 75.

[0061] The material recirculation system further comprises a recirculation valve 70 and a recirculation air chute. The recirculation valve 70 is arranged on a pipeline connected between the dust collector 90 and the bottom of the desulfurization tower, and the chute is arranged in a pipeline connected between the recirculation valve 70 and the bottom of the desulfurization tower. The recirculation chute returns the material in the dust collector to the absorption tower. The recirculation valve controls the flow of the material returned to the absorption tower by the recirculation chute.

[0062] The flue gas treatment system further comprises a dust remover system, which is provided with a bag dust remover or a ceramic tube dust remover.

[0063] The desulfurizer is a Ca(OH)2 desulfurizer.

[0064] A flue gas treatment method for breaking the edge effect in a tower and improving the removal efficiency of pollutants, which is implemented by using the flue gas treatment system for breaking the edge effect in a tower and improving the removal efficiency of pollutants according to any one of the above.

[0065] S100: The flue gas of the flue gas treatment system is drawn from a coke oven or a boiler or a pellet 10, the flue gas enters a desulfurization tower 80 from the bottom, flows out from the side of the top of the tower and enters a material backflow device 83; the pollutants in the flue gas react and are removed in the desulfurization tower 80 and the material backflow device 83, and the particulate matters in the flue gas are removed in a dust remover 90; after the removal of the pollutants and the particulate matters, the flue gas is discharged into the atmosphere through a chimney 95.

[0066] S200: The mixed material of the material circulation system, including dust, desulfurizer, desulfurization by-products and the like, is carried into the desulfurization tower 80 from the flue gas drawn from the coke oven or the boiler or the pellet 10, the desulfurizer enters the desulfurization tower 80, and the flue gas heavy metal and dioxin removal agent are added into the material backflow device 83; the mixed material carried by the flue gas system is deposited in a material backflow hopper 85, and the other part is collected in the dust remover 90; the mixed material collected through the material backflow hopper 85 and the dust remover 90 is returned to the absorption tower 80 through a back material device 72 for the next circulation backflow.

[0067] S300: The excess material needed to be discharged in the material circulation system, a part of which is discharged to a desulfurization by-product bin 75 through the bottom of the desulfurization tower 80, and the other part is discharged to the desulfurization by-product bin 75 through the lower No. 4 rotary feeding valve 71 of the back material device 72.

[0068] In addition, the dust remover 90 is communicated with a denitration agent storage tank 40, the denitration agent in the denitration agent storage tank 40 is NaClO2, and the denitration agent is introduced into the dust remover 90 through a pipeline.

[0069] The application adopts high-performance Ca(OH)2 desulfurizer to replace NaHCO3 in the coking industry and conventional CaO or Ca(OH)2 used in the conventional semi-dry desulfurization method. The BET specific surface area of the high-performance Ca(OH)2 is greater than 40 m2 / g, and the particle size distribution (325 mesh screening rate) is greater than 85%.

[0070] The reaction mechanism of NaHCO3 is as follows:

[0071] Sodium bicarbonate superfine powder is decomposed into high-activity Na2CO3 and CO2 under the action of flue gas at 150°C (may be floating not more than 220°C). The active Na2CO3 fully contacts with SO2 and other acidic media in the flue gas and reacts to generate Na2SO4. The desulfurization powder product after reaction enters the bag filter with the airflow and is removed, and is discharged from the lower part of the dust collector. The by-products are stored.

[0072] The minimum temperature of flue gas is required to be > 140°, the minimum contact time of baking soda with flue gas is 2 seconds, and the particle size requirement is 90% < 35 μm (remove HCl) and 90% < 20 μm (remove SO x ).

[0073] 2NaHCO3 > 140° Na2CO3 + CO2↑ + H2O

[0074] Reaction mechanism

[0075] Na2CO3 + SO2 + 1 / 2O3 = Na2SO4 + CO2↑

[0076] Na2CO3 + SO3 = Na2SO4 + CO2↑

[0077] Na2CO3 + 2HCl = 2NaCl + CO2↑ + H2O

[0078] Na2CO3 + 2HF = 2NaF + CO2↑ + H2O

[0079] 2NaHCO3 + SO2 = Na2SO3 + 2CO2↑ + H2O

[0080] Sodium-based dry desulfurization utilizes the mixing and contact of desulfurizer superfine powder with flue gas, and under the action of catalyst and promoter, the desulfurizer reacts quickly with SO2 in the flue gas. The desulfurizer superfine powder will continue to react with SO2 in the flue gas in the reactor, flue and bag filter, and the reaction is quick and sufficient, and the by-product sodium sulfate can be produced within 2 seconds.

[0081] The waste produced by sodium-based dry desulfurization is sodium sulfate, sodium sulfite, sodium carbonate and the like, which is hazardous waste and difficult to handle. It needs to be disposed by a professional hazardous waste company.

[0082] High-performance Ca(OH)2 desulfurizer:

[0083] Calcium-based high-efficiency desulfurizer is a desulfurizer (20-25 μm, main component calcium hydroxide) that is activated by heat in the pipeline, and the specific surface area increases rapidly. The desulfurizer fully contacts with coke oven flue gas, and physical and chemical reactions occur. The SO2 and other acidic substances in the flue gas are absorbed and purified, and the clean flue gas is discharged into the atmosphere by the booster fan through the outlet flue to the original chimney.

[0084] The chemical principle is that Ca(OH)2powder and SO2and almost all SO3, HCl, HF, etc. in the flue gas react on the surface of Ca(OH)2particles. In the reflux flue gas circulating fluidized bed, Ca(OH)2powder, flue gas and water sprayed are fully mixed in the fluidized state, and high-efficiency desulfurization is achieved through multiple recirculation of Ca(OH)2powder. The following reaction formulas describe the chemical reactions of the reactions.

[0085] Ca(OH)2+ SO2= CaSO3+ H2O

[0086] Ca(OH)2+ SO3= CaSO4+ H2O

[0087] CaSO3+ ½O2= CaSO4

[0088] Ca(OH)2+ CO2= CaCO3+ H2O

[0089] Ca(OH)2+ 2HCl = CaCl2+ 2H2O

[0090] Ca(OH)2+ 2HF = CaF2+ 2H2O

[0091] The desulfurization product of the calcium-based high-efficiency desulfurizer is calcium sulfite or calcium sulfate, which belongs to the third type of solid waste and is easy to bury. The desulfurization waste slag can be used as raw material for resource utilization by cement plants, building materials, bricks, etc. The waste gas is discharged in line with the standard, and the amount of solid waste is greatly reduced.

[0092] Table 1 Comparison of parameters of high-performance Ca(OH)2desulfurizer and ordinary Ca(OH)2

[0093]

[0094]

[0095] The fields of application of high-performance Ca(OH)2include coking industry, ceramic building materials, steel industry, garbage power plant, glass industry, biomass fuel boiler, etc.

[0096] Example 1:

[0097] Please refer to Figure 1A flue gas treatment system for breaking the side wall effect in the tower and improving the removal efficiency of pollutants is provided. Flue gas from a coke oven, a boiler, a pellet or a solid waste treatment system 10 enters a desulfurization tower 80. The desulfurization tower is provided with a tower flue gas side wall breaking ring 81 from the inlet to the outlet along the flue gas flow direction, a flue gas disturbance recirculation device 82 at the top of the desulfurization tower, a vertically downward material backflow device 83 at the flue gas outlet of the top of the desulfurization tower, and a material backflow hopper 85 below the material backflow device. The material backflow device 83 is provided with a plug door 84, a diffusion settling section 86 and a reaction settling cylinder 87 from the inlet to the outlet. The desulfurization tower 80 is connected to a dust collector 90, which is also a reactor for removing nitrogen oxides, heavy metals and dioxins. The flue gas after denitrification, heavy metal removal and dioxin removal is discharged from a chimney 95.

[0098] The desulfurizer is delivered to the desulfurization tower 80 by the desulfurizer storage bin 20 and the bottom rotary feeder valve 21. The desulfurizer is connected between the desulfurization tower side wall breaking ring and the bottom gas inlet cone section, which avoids the high-speed flue gas in the desulfurization tower due to the side wall effect from carrying the desulfurizer out of the desulfurization tower, resulting in a decrease in the use efficiency of the desulfurizer. A heavy metal and dioxin removal agent inlet is provided between the material backflow device and the dust collector inlet, and is connected to the heavy metal and dioxin removal agent storage bin 30 and the bottom rotary feeder valve 31. A denitration agent inlet is provided between the material backflow device and the dust collector inlet, and is connected to the denitration agent storage tank 40 and the denitration agent delivery pump 41.

[0099] A rotary feeder valve 60 is provided at the bottom of the material backflow hopper 85, a back feeding device 72 is provided at the bottom of the dust collector 90 and a flow regulating valve 70 is installed, the rotary feeder valve 60 at the bottom of the material backflow hopper 85 is connected to the back feeding device 72 at the bottom of the dust collector 90. The back feeding device 70 is connected to the desulfurization tower 80, and a rotary feeder valve 71 is provided at the lower part of the back feeding device and is connected to the desulfurization byproduct bin 75.

[0100] The desulfurization tower 80 is provided with a side wall breaking ring 81, which is provided with one or more stages and is located in the cylindrical section after the cone section of the desulfurization tower, which is also a high-speed airflow area around the tower wall. The desulfurization tower 80 is provided with a tower top disturbance recirculation device 82, and the flue gas outlet and the top of the desulfurization tower form a space for flue gas recirculation and re-turn. The flue gas carrying dust and incompletely reacted desulfurizer rises to the top of the tower, changes the flue gas flow direction after the tower top disturbance recirculation device 82, increases the residence time of the flue gas and the absorbent in the tower, enhances the mass transfer reaction between the flue gas and the absorbent, improves the desulfurization efficiency, and improves the utilization rate of the desulfurizer.

[0101] The material recirculation device 83 is provided with a material backflow hopper 85. The material recirculation device 83 can be provided with one or more, and the number of the dust removal units of the dust remover 90 is matched with the number of the material recirculation devices 83. A plug door 84 is arranged at the inlet of each material recirculation device 83. The flue gas enters the diffusion settling section 86 after passing through the plug door 84. The dust and the desulfurizing agent which is not completely reacted under the action of gravity enter the reaction settling cylinder 87. The pollutant desulfurization reaction continues, and the dust and other large particles enter the material backflow hopper 85 under the action of gravity.

[0102] Example 2:

[0103] In this embodiment, the heavy metal and dioxin removal agent storage bin 30 and the bottom rotary feeding valve 31 are connected between the flue gas outlet of the desulfurizing tower and the dust remover through a pipeline, and the connection point is after the material backflow device 83.

[0104] Example 3:

[0105] In this embodiment, the denitration agent in the denitration agent storage tank 40 is NaClO2 oxidation denitration, and the dust remover 90 is a bag dust remover.

[0106] Example 4:

[0107] In this embodiment, the denitration agent in the denitration agent storage tank 40 is ammonia water denitration, and the dust remover 90 is a filter carrier combined with a catalyst. The dust remover 90 can be a ceramic fiber filter tube.

[0108] Example 5:

[0109] In this embodiment, the desulfurizing agent in the desulfurizing agent storage bin 20 is sodium bicarbonate instead of high-performance calcium hydroxide, and a grinding system is matched.

[0110] Example 6:

[0111] In this embodiment, the material backflow device 83 of the desulfurizing tower 80 is provided with one or more according to the size of the flue gas. The outlet of each material backflow device 83 is connected to the inlet of a dust remover unit. When any unit of the dust remover fails, the plug door 84 on the corresponding material backflow device 83 can be closed to realize online maintenance of the bag dust remover.

[0112] Example 7:

[0113] In this embodiment, the material backflow device 83 passes through the diffusion settling section 86 and the reaction settling cylinder 87, and is matched with a flow guide device to enter the dust remover 90.

[0114] The present application can use high-performance calcium hydroxide instead of sodium bicarbonate as a desulfurizer, and can also use sodium bicarbonate as a desulfurizer. The edge wall breaking ring 81 of the desulfurization tower 80, the tower top disturbance recirculation device 82, and the material backflow device 83 form a set of smoke gas treatment system for breaking the edge wall effect in the desulfurization tower, enhancing recirculation, and improving the desulfurization and dust removal efficiency.

[0115] For a cylindrical desulfurization tower, the "edge wall effect" caused by the bottom entering flue gas leads to local flue gas flow too fast, forming a situation of more flue gas around and less flue gas in the center. The airflow in the whole tower is uneven, the flow field is disorderly, the contact strength and uniformity of the desulfurizer and flue gas in different areas are different, which affects the desulfurization efficiency and the utilization rate of the desulfurizer.

[0116] The flue gas from the coke oven or pellet or boiler enters the inlet of the desulfurization tower 80, is accelerated through the reduced diameter pipe and enters the cylindrical section after the tapered expansion. The desulfurizer in the desulfurizer storage bin 20 is connected between the cylindrical section and the tapered section. The edge wall breaking ring 81 changes the flow direction of the flue gas and the desulfurizer carried by the flue gas, disturbs the tower wall flue gas flow, and makes the desulfurizer contact with the flue gas more uniformly. The flue gas flows to the top of the desulfurization tower through the tower top disturbance recirculation device 82, making the flue gas backflow, intensifying the mixing, contacting and mass transfer of the flue gas and the desulfurizer. After the flue gas flows out of the top of the desulfurization tower, it enters the material backflow device 83 for further rectification, mixing and mass transfer reaction. A part of the desulfurizer and dust that has not reacted enters the material backflow hopper 85 by free settling and returns to the back material device 72 through the bottom rotary feeding valve 60 for reutilization. Another part of the fine particles enters the dust collector 90 with the flue gas.

[0117] After the sedimentation of the material backflow device 83, the dust concentration is greatly reduced, and the dust load entering the dust collector 90 is correspondingly reduced. The desulfurizer in the heavy metal and dioxin removal agent storage bin 30 and the denitration agent in the denitration agent storage tank 40 are connected at the position entering the dust collector. The denitration, heavy metal removal, dioxin removal and dust removal are carried out in the dust collector 90, and the purified flue gas is discharged from the chimney 95. The dust concentration at the bag outlet is less than 5mg / Nm 3 .

[0118] The materials collected by the material backflow hopper 85 and the dust collector 90 flow back to the desulfurization tower 80 through the back material device 72, and then flow to the desulfurization byproduct bin 75 through the rotary feeding valve 71.

[0119] The edge wall breaking ring 81, the disturbance recirculation device 82, the material backflow device 83 and the material backflow hopper 85 of the present application simultaneously serve as gas and solid mass transfer strengthening devices, increase the contact opportunity of dust in flue gas and desulfurizer, prolong the residence time of desulfurizer in the desulfurization tower, and reduce the dust concentration entering the bag dust collector. The desulfurization efficiency and dust removal efficiency are higher than that of the CFB desulfurization process, and the utilization rate of the desulfurizer is high.

[0120] The current CFB desulfurization system has the following problems: the reaction time of desulfurizer and flue gas is short, the residence time of desulfurizer in the desulfurization tower is short, the Ca / S value is high at 1.3-1.6, which leads to the increase of the consumption of desulfurizer and the decrease of the utilization rate of desulfurizer, the dust concentration at the outlet of the desulfurization tower, i.e. the inlet of the bag filter, is as high as 800-1000 g / Nm3, which leads to the high inlet load of the bag filter, the high requirement for the filter bag material of the bag filter, the low design requirement for the gas cloth ratio, the increase of the engineering cost, the flue gas flow edge wall phenomenon is common in the desulfurization tower, the contact between the flue gas and the absorbent is not sufficient and uniform, the desulfurization efficiency is affected, the utilization rate of desulfurizer is reduced, and the operation cost of the desulfurization system is increased; the desulfurization efficiency is not suitable for the current domestic ultra-low emission of air pollutants.

[0121] Compared with the current CFB desulfurization process with a residence time of 3-5 s, the residence reaction time of flue gas in the whole desulfurization tower is increased to 10-15 s, and the reaction time is increased by 3-5 times.

[0122] The Ca / S value is reduced to 1.1-1.3 from 1.3-1.6 of the current CFB, the consumption of desulfurizer is reduced, and the utilization rate of desulfurizer is increased.

[0123] After two parts of sedimentation through the material reflux device 83, one part is the inlet diffusion sedimentation section 86 of the material reflux device, the flue gas flow area is increased, the flue gas flow rate is slowed down, the initial conditions for natural sedimentation of the material are met, the sedimentation rate and efficiency of the material are increased; the other part is the reaction sedimentation section 87, the diffusion sedimentation section 86 is used for nucleating the dust, and the dust enters the vertically arranged reaction sedimentation section, the two gravity sedimentation sections play a pre-sedimentation role on the dust carried by the flue gas at the outlet of the desulfurization tower. The pre-sedimentation dust removal efficiency is 30-50%, the dust concentration at the inlet of the bag filter is reduced to 400-700 g / Nm3 after two-stage natural sedimentation, and the dust concentration at the outlet of the dust remover can be less than 5 mg / Nm 3 .

[0124] The whole desulfurization efficiency is more than 99.0%, and the sulfur dioxide emission concentration at the outlet of the desulfurization tower can be less than 10 mg / Nm 3 .

[0125] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts of each embodiment can be referred to each other.

[0126] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A flue gas treatment system for breaking the side wall effect in a tower to improve the removal efficiency of pollutants, characterized in that: the flue gas treatment system is arranged on a desulfurization tower (80) and connected with the desulfurization tower (80); the flue gas treatment system comprises a material circulation system and a removal system; the material circulation system comprises a side wall breaking ring (81), a turbulence recirculation device (82), a material backflow device (83), a plug door (84) and a material backflow hopper (85); the side wall breaking ring (81) is arranged in a reaction section of the desulfurization tower (80), the turbulence recirculation device (82) is arranged at the top of the desulfurization tower (80), the material backflow device (83) is arranged at the flue gas outlet at the top of the desulfurization tower (80), the flue gas flowing out of the top of the desulfurization tower (80) enters the material backflow device (83) and the material backflow hopper (85); the inlet of the material backflow device (83) is provided with the plug door (84) connected with a diffusion settling section (86) and a reaction settling cylinder (87), and the plug door at the outlet can be closed or opened according to needs; the side wall breaking ring (81) is a one-stage or multi-stage arc-shaped plate, and a row of "V-shaped", inverted triangular, uniformly distributed hole-shaped or rectangular opening structures perpendicular to the arc-shaped plate are arranged on the outer edge of the arc-shaped plate; the side wall breaking ring is arranged from the connection between the conical section and the straight section of the desulfurization tower, and the side wall breaking ring spirally rises along the straight section of the desulfurization tower (80) and is connected with the turbulence recirculation device (82) at the top of the tower; the flue gas outlet of the desulfurization tower (80) is provided with a blind area with a certain height at the top, the turbulence recirculation device (82) is arranged in the blind area and fixed at the top of the desulfurization tower (80) in a spiral rotating tubular structure to hinder the flow of flue gas; under the action of the turbulence recirculation device (82) at the top, the upward flowing flue gas carries dust and desulfurizing agent to rotate and descend at the top of the desulfurization tower (80); the removal system reserves and supplies flue gas heavy metal, dioxin removal agent and desulfurizing agent, and comprises an activated carbon storage bin and a pneumatic conveying device; the material backflow device (83) and the material backflow hopper (85) are connected with a dust collector (90), the material backflow device (83) is connected with the desulfurization tower (80), and at least one stage of the material backflow device (83) is arranged, and multiple stages can be arranged according to the size of flue gas; each inlet of the material backflow device (83) has a section of rectangular or square flue, a flue plug door is arranged on the regular-shaped flue, the flue plug door (84) is controlled to be opened or closed by using a pneumatic or electric actuator, the transmission mechanism of the actuator is vertically upward, and maintenance is carried out on the top platform of the desulfurization tower (80); after the material backflow device (83) passes through the section of regular-shaped flue, the bottom plate of the flue is inclined to the diffusion settling section (86) at an angle greater than 60 degrees, and the dust deposited on the bottom plate can slide to the material backflow hopper (85) due to the sufficient inclination angle; the diffusion settling section (86) of the material backflow device (83) has an irregular rectangular shape, and is connected with a cylindrical reaction settling cylinder (87) at the back; the dust after diffusion settling and reaction settling enters the conical material backflow hopper (85), and a circular or square material conveying interface is arranged at the bottom of the material backflow hopper (85). ​ ​ ​ ​ 2. The flue gas treatment system for breaking the side wall effect in the tower and improving the removal efficiency of pollutants according to claim 1, characterized in that: The removal system comprises a desulfurizing agent storage bin (20), a first rotary feeder valve (21), a flue gas heavy metal and dioxin removal agent storage bin (30), a second rotary feeder valve (31), a denitration agent storage tank (40), and a denitration agent delivery pump (41); The desulfurizing agent storage bin (20) is connected to the desulfurizing tower (80) through the first rotary feeder valve (21) at the bottom of the bin, the flue gas heavy metal and dioxin removal agent storage bin (30) is connected to the desulfurizing tower (80) through the second rotary feeder valve (31) at the bottom of the bin, and the denitration agent storage tank (40) is connected to the pipeline between the material backflow device (83) and the dust collector (90) through the denitration agent delivery pump (41).

3. The flue gas treatment system for breaking the side wall effect in the tower and improving the removal efficiency of pollutants according to claim 2, characterized in that: The bottom of the material backflow hopper (85) is provided with a third rotary feeder valve (60), and the third rotary feeder valve (60) is connected to the back material device (72) at the bottom of the dust collector (90); the back material device (72) is connected to the desulfurizing tower (80) through the flow regulating valve (70), and the fourth rotary feeder valve (71) at the lower part of the back material device (72) is connected to the desulfurizing byproduct bin (75). The desulfurizing tower (80) is provided with one or more outlets according to the flue gas treatment capacity of the desulfurizing tower, the size of the flue gas outlet, and the flue gas flow rate, each outlet is provided with a plug door (84), and then connected to the material backflow device (83); the outlet of the material backflow device (83) is connected to the dust collector (90), and the dust collector (90) is connected to the chimney (95); when any unit of the dust collector (90) fails, the plug door (84) on the corresponding material backflow device (83) can be closed to realize online maintenance of the dust collector (90).

4. The flue gas treatment system of claim 1, wherein: The side wall breaking ring adopts a carbon steel structure, the thickness of the carbon steel is 10-20 mm, the width range is 500-800 mm, the included angle between the side wall breaking ring and the horizontal plane is about 30 degrees, and the connection between the side wall breaking ring and the desulfurizing tower is welding, the welding method is full welding on both sides, the side wall breaking ring is provided with a flue gas rectifying grid, different shapes are set according to different working conditions or different requirements of actual projects on the flue gas flow field; The number of the side wall breaking rings (81) can be set to one level or multiple levels according to the diameter of the desulfurizing tower (80).

5. The flue gas treatment system for breaking the side wall effect in the tower and improving the removal efficiency of pollutants according to claim 1, characterized in that: The heavy metal and dioxin removal agent storage bin (30) is connected to the dust collector (90) through the second rotary feeder valve (31) at the bottom of the bin; the third rotary feeder valve (60) at the bottom of the material backflow hopper (85) is connected to the back material device (72) at the bottom of the dust collector (90); the back material device (72) is connected to the desulfurizing tower (80) through the flow regulating valve (70), and the fourth rotary feeder valve (71) at the lower part of the back material device (72) is connected to the desulfurizing byproduct bin (75).

6. The flue gas treatment system for breaking the edge effect in the tower and improving the removal efficiency of pollutants according to claim 5, characterized in that: The material reflux system further comprises a recirculation valve and a recirculation air chute; the recirculation valve is arranged on a pipeline connected to the bottom of the desulfurization tower and the dust collector (90), and the chute is arranged in a pipeline connected to the recirculation valve and the bottom of the desulfurization tower; The flue gas treatment system further comprises a dust collector system, and the dust collector system is provided with a bag-type dust collector or a ceramic tube dust collector; The desulfurizer is a Ca(OH)2 desulfurizer.

7. A flue gas treatment method for breaking the side wall effect in a tower to improve the removal efficiency of pollutants, characterized in that, The application of the flue gas treatment system for breaking the edge effect in the tower and improving the removal efficiency of pollutants according to any one of claims 1-6 comprises: S100: The flue gas of the flue gas treatment system is introduced from a coke oven or a boiler or a pellet (10), the flue gas enters the desulfurization tower (80) from the bottom, and flows out from the side of the top of the tower into the material reflux device (83); the pollutants in the flue gas are removed by reaction in the desulfurization tower (80) and the material reflux device (83), and the particulate matters in the flue gas are removed in the dust collector (90); after the removal of the pollutants and the particulate matters, the flue gas is discharged into the atmosphere through the chimney (95); S200: The dust carried by the flue gas introduced from the coke oven or the boiler or the pellet (10) enters the desulfurization tower (80), the desulfurizer enters the desulfurization tower (80), and the flue gas heavy metal and dioxin removal agent are added to the material reflux device (83); the flue gas system carries a part of the mixed material to deposit in the material reflux hopper (85), and another part of the mixed material is collected in the dust collector (90); the mixed material collected through the material reflux hopper (85) and the dust collector (90) is returned to the absorption tower through the material return device (72) for the next circulation reflux; S300: The excess material that needs to be discharged in the material circulation system is discharged to the desulfurization by-product bin (75) through the bottom of the desulfurization tower (80), and a part of the excess material is discharged to the desulfurization by-product bin (75) through the fourth rotating feeding valve (71) at the lower part of the material return device (72).

8. The flue gas treatment method of breaking the side wall effect in tower to improve the removal efficiency of pollutants according to claim 7, characterized in that: The dust collector (90) is connected to the denitration agent tank (40), the denitration agent in the denitration agent tank (40) is NaClO2, and the denitration agent is introduced into the dust collector (90) through a pipeline.

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