Flue gas absorption purification device combining photocatalysis and wet ammonia method and use method of flue gas absorption purification device

Abstract

The invention discloses a photocatalysis and wet ammonia process absorption combined flue gas purification device and a use method thereof. The device sequentially comprises a primary amino solution absorption system, a microwave photocatalytic oxidation system, a solution circulation system and a secondary amino solution absorption system from left to right, when the device is used, flue gas from a coal-fired boiler is subjected to SO2 removal through a primary absorption tower and then enters a microwave photocatalytic reactor, an electrodeless lamp is excited by microwaves to generate hydroxyl radicals, and meanwhile, H2O2 and FeSO4 in a liquid phase can also generate hydroxyl or sulfate radical free bodies, so that the oxidation process is accelerated; generated Hg < 2 + > and NO2 are absorbed by a subsequent ammonia water solution with ammonium sulfite, and ammonium nitrate, ammonium sulfate and other products can be obtained. The device has the advantages that the occupied area is small, desulfurization, denitrification and demercuration can be performed simultaneously, and products can be recycled.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas purification, and in particular to a photocatalytic combined with wet ammonia absorption flue gas purification device and a method of using the same. Background Art

[0002] At present, the methods for controlling SO2 emissions in flue gas can be divided into: desulfurization before combustion, desulfurization during combustion and desulfurization after combustion. Conventional flue gas nitrogen oxide removal technologies mainly include non-selective catalytic reduction technology and selective catalytic reduction technology. Non-selective catalytic reduction technology refers to the injection of chemical reducing agents such as ammonia and urea in the furnace to react with nitrogen oxides in the flue gas and convert them into nitrogen and water. The use of this technology can achieve a denitrification efficiency of 80-90% under reasonable layout and temperature range, but at the same time, the disadvantage of this technology is that there is a temperature window for denitrification reaction and ammonia escape. In addition, vanadium-based catalysts not only have high manufacturing costs, but also the active components of the catalyst (vanadium pentoxide) are biologically toxic. These reasons limit the application of SCR denitrification technology in industrial coal-fired boilers. Traditional wet flue gas desulfurization (WFGD) combined with selective catalytic reduction denitrification (NH3-SCR) technology has been widely used in power plant boilers. The difficulty that wet denitrification needs to overcome is to increase the oxidation degree of nitrogen oxides. Currently, there is no technology for mercury removal alone. The existing technical system for mercury emission control mainly relies on dust removal, desulfurization and denitrification processes to achieve coordinated control.

[0003] Advanced oxidation technology is a deep oxidation process, which usually refers to the production of hydroxyl radicals (·OH) with strong oxidizing ability in the reaction system under the reaction conditions of high temperature, high pressure, electricity, sound, light radiation, catalyst, etc., so that large molecular refractory organic matter is oxidized into low-toxic or non-toxic small molecular substances in the presence of catalysts such as Fe 3+ , Fe 2+ , Cu 2+ In the presence of H2O2, ·OH will be produced in the Fenton system, so that Hg 0 It will be removed by OH in the flue gas;

[0004] Microwave heating has long been used in the food and rubber industries, but there is growing interest in its potential use in other industrial processes, such as treating various wastes and processing mineral ores. Based on the traditional wet ammonia desulfurization process, the microwave electrodeless ultraviolet lamp is used to activate the H2O2 / FeSO4 system to oxidize Hg 0 and NO, increasing the generation and effective utilization of free radicals.

[0005] Therefore, in order to solve the above problems, this paper proposes a photocatalytic combined with wet ammonia absorption flue gas purification device and its use method. Summary of the invention

[0006] The purpose of the present invention is to provide a photocatalytic combined wet ammonia absorption flue gas purification device and a method of using the same, so as to solve the problems of low oxidation efficiency and high operating cost in the process of desulfurization, denitrification and demercuration.

[0007] In order to achieve the above technical effects, the present invention is implemented by the following technical solutions: a photocatalytic combined with wet ammonia absorption flue gas purification device, characterized in that it includes, from left to right, a primary amino solution absorption system, a microwave photocatalytic oxidation system, a solution circulation system and a secondary amino solution absorption system;

[0008] The primary amino solution absorption system comprises a liquid storage tank, an inlet and an outlet respectively arranged at the upper and lower ends of the liquid storage tank, a pipe connected to the outlet, a metering pump arranged at the end of the pipe, the output end of the metering pump is connected to the inlet of the amino absorption tower through a two-section pipe, a demister arranged in the amino absorption tower, a compressor installed at one side of the amino absorption tower, and a flue gas discharge pipe connected to the inlet of the compressor;

[0009] The microwave photocatalytic oxidation system comprises a microwave photocatalytic reactor connected to an outlet of an amino absorption tower through a delivery pipe, a hydrogen peroxide storage tank connected to the upper end of the microwave photocatalytic reactor through a connecting pipe, a flow meter arranged in the middle of the connecting pipe, and a microwave switch installed at the side end of the microwave photocatalytic reactor, wherein the microwave switch is electrically connected to the microwave photocatalytic reactor;

[0010] The solution circulation system comprises a second liquid storage tank connected to the waste liquid outlet of the first amino absorption tower through a waste liquid pipe, a second metering pump connected to the outlet of the second liquid storage tank, and a three-way valve pipeline connected to the outlet of the second metering pump, and the remaining two interfaces of the three-way valve pipeline are respectively connected to the inlet of the first amino absorption tower and the inlet of the second amino absorption tower;

[0011] The secondary amino solution absorption system includes a second compressor arranged at the outlet of a microwave photocatalytic reactor, a second amino solution absorption tower connected to the outlet of the second compressor, a third compressor installed at the outlet of the second amino solution absorption tower, a chimney connected to the outlet of the third compressor, a crystallizer connected to the circulation port of the second amino solution absorption tower, a third liquid storage tank fixedly connected to the side end of the crystallizer, and a third metering pump connected to the outlet of the third liquid storage tank and the inlet of the first liquid storage tank.

[0012] Furthermore, the flue gas emission pipe is a tail gas emission pipe of a coal-fired boiler.

[0013] Furthermore, there is aqueous ammonia in both the amino absorption tower 1 and the amino absorption tower 2, and there is also divalent S in the amino absorption tower 2. 2- Solution.

[0014] Furthermore, the microwave photocatalytic reactor comprises a microwave reactor and an electrodeless ultraviolet lamp arranged in the microwave reactor; the electrodeless ultraviolet lamp is excited by microwaves; the radiation power of the electrodeless ultraviolet lamp is 14500 μw / cm 2 , the ultraviolet wavelength is 185-254nm.

[0015] Furthermore, when the microwave photocatalytic reactor is used, a Fenton reagent FeSO4 solution is added in advance; the FeSO4 concentration is 0.01-0.04 mol / L.

[0016] Furthermore, the concentration of hydrogen peroxide in the hydrogen peroxide storage tank is 10-25wt%.

[0017] Furthermore, the second liquid storage tank is pre-stored with an ammonium sulfite solution having a concentration of 0.05-0.15 wt % and a pH value of 5.5-6.5, and the ammonium sulfite solution is used as the absorption liquid.

[0018] Furthermore, during use of the device, the reaction temperature is 40-160°C and the working pressure is 0.1-0.3Mpa.

[0019] Another object of the present invention is to provide a method for using a photocatalytic combined with wet ammonia absorption flue gas purification device, characterized in that it comprises the following steps:

[0020] S1. First, check whether the device is tightly connected. After the inspection, add ammonia water and ammonium sulfite solution to liquid storage tank 1 and liquid storage tank 2 respectively. Liquid storage tank 3 is empty. At the same time, add Fenton reagent FeSO4 solution to the microwave photocatalytic reactor and add hydrogen peroxide to the hydrogen peroxide storage tank to complete the preparation before use.

[0021] S2. When in use, operate the external control box to control the metering pump to move, inject the ammonia water in the liquid storage tank into the amino solution absorption tower, and then connect the air inlet of the compressor to the tail gas pipe of the coal-fired boiler, so that the exhaust gas discharged from the compressor is introduced into the lower part of the amino solution absorption tower, and the SO2 in the flue gas is absorbed by the ammonia solution to produce ammonium sulfite. At the same time, the demister separates the droplets entrained in the exhaust gas into gas and liquid;

[0022] S3. At this time, the ammonia solution with ammonium sulfite enters the second storage tank of the solution circulation system through the drain pipe, and the flue gas with SO2 removed is transported to the microwave photocatalytic reactor of the microwave photocatalytic oxidation system through the delivery pipe. The reactor generates high voltage through an adjustable microwave power supply, which is transmitted to the magnetron through a waveguide and then converted into microwaves. The electrodeless lamp generates ultraviolet radiation through microwave excitation, which excites and decomposes the FeSO4 solution to release hydroxyl free radicals OH with strong oxidizing properties, and oxidizes NO and Hg0 in the flue gas. The hydrogen peroxide storage tank is metered by a flow meter to replenish the required oxidant;

[0023] S4, the flue gas treated by the microwave photocatalytic reactor is transmitted to the second compressor through the pipeline, and the second compressor sends the flue gas from the lower part of the secondary amino solution absorption system. At the same time, the mixed liquid composed of the ammonium sulfite solution in the second liquid storage tank and the ammonia water with ammonium bisulfite discharged from the amino solution absorption tower 1 is extracted by the second metering pump and transported by the three-way valve pipeline into the amino solution absorption tower 1 and the amino solution absorption tower 2, and the divalent S is added to the amino solution absorption tower 2. 2- Solution, which can efficiently absorb high-valent nitrogen oxides, nitrous acid and HgO in flue gas;

[0024] S5, the clean flue gas after absorption is transmitted from the amino solution absorption tower 2 to the chimney 6 and discharged into the atmosphere; during the treatment process of the amino solution absorption tower 2, Hg 2+ The added S 2- The reaction generates insoluble HgS precipitate, and the remaining liquid is concentrated by a crystallizer to obtain commonly used agricultural fertilizers such as ammonium sulfate and ammonium nitrate, which is beneficial to resource utilization. The excess ammonia water after concentration is then transported to liquid storage tank three, and then re-transported to liquid storage tank one under the action of metering pump three for repeated recycling.

[0025] The beneficial effects of the present invention are:

[0026] The present invention is applicable to the operating conditions of most coal-fired power plants in my country and meets the emission standards of pollutants. Compared with the currently common selective oxidation-reduction denitrification technology after desulfurization, the operating cost of this treatment system is lower. In addition to desulfurization and denitrification, mercury in flue gas can also be removed simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0028] Figure 1 It is a schematic diagram of the overall structure of the device of the present invention;

[0029] Figure 2 is a flow chart of the use of the device of the present invention;

[0030] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0031] 1. Compressor 1; 2. Liquid storage tank 1; 3. Amino absorption tower 1; 4. Hydrogen peroxide liquid storage tank; 5. Liquid storage tank 2; 6. Crystallizer; 7. Liquid storage tank 3; 8. Chimney; 9. Compressor 2; 10. Microwave switch; 11. Compressor 3; 12. Amino absorption tower 2; 13. Metering pump 1; 14. Metering pump 2; 15. Metering pump 3; 16. Microwave photocatalytic reactor. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] See also Figure 1 As shown, a photocatalytic combined with wet ammonia absorption flue gas purification device is characterized in that it includes, from left to right, a primary amino solution absorption system, a microwave photocatalytic oxidation system, a solution circulation system and a secondary amino solution absorption system;

[0035] The primary amino solution absorption system comprises a liquid storage tank 2, an inlet and an outlet respectively arranged at the upper and lower ends of the liquid storage tank 2, a pipe section connected to the outlet, a metering pump 13 arranged at the end of the pipe section, the output end of the metering pump 13 is connected to the inlet of the amino absorption tower 3 through a two-section pipe, a demister arranged in the amino absorption tower 3, a compressor 1 installed at the side end of the amino absorption tower 3, and a flue gas discharge pipe connected to the inlet of the compressor 1;

[0036] The microwave photocatalytic oxidation system comprises a microwave photocatalytic reactor 16 connected to the outlet of the amino absorption tower 3 through a delivery pipe, a hydrogen peroxide storage tank 4 connected to the upper end of the microwave photocatalytic reactor 16 through a connecting pipe, a flow meter arranged in the middle of the connecting pipe, and a microwave switch 10 installed at the side end of the microwave photocatalytic reactor 16, wherein the microwave switch 10 is electrically connected to the microwave photocatalytic reactor 16;

[0037] The solution circulation system includes a liquid storage tank 25 connected to the waste liquid outlet of the amino absorption tower 3 through a waste liquid pipe, a metering pump 214 connected to the outlet of the liquid storage tank 25, and a three-way valve pipeline connected to the outlet of the metering pump 214, and the remaining two interfaces of the three-way valve pipeline are respectively connected to the inlet of the amino absorption tower 3 and the inlet of the amino absorption tower 212;

[0038] The secondary amino solution absorption system includes a compressor 29 arranged at the outlet of the microwave photocatalytic reactor, an amino solution absorption tower 212 connected to the outlet of the compressor 29, a compressor 311 installed at the outlet of the amino solution absorption tower 212, a chimney 8 connected to the outlet of the compressor 311, a crystallizer 6 connected to the circulation port of the amino solution absorption tower 212, a liquid storage tank 37 fixedly connected to the side end of the crystallizer 6, and a metering pump 315 connected to the outlet of the liquid storage tank 37 and the inlet of the liquid storage tank 12.

[0039] The flue gas emission pipe is a tail gas emission pipe of a coal-fired boiler.

[0040] There is ammonia water in both the amino absorption tower 1 3 and the amino absorption tower 2 12. There is also divalent S in the amino absorption tower 2 12. 2- Solution.

[0041] The microwave photocatalytic reactor 16 includes a microwave reactor and an electrodeless ultraviolet lamp arranged in the microwave reactor; the electrodeless ultraviolet lamp is excited by microwaves; the radiation power of the electrodeless ultraviolet lamp is 14500 μw / cm 2 , the ultraviolet wavelength is 185-254nm.

[0042] When the microwave photocatalytic reactor 16 is used, a Fenton reagent FeSO4 solution is added in advance; the FeSO4 concentration is 0.01-0.04 mol / L.

[0043] The concentration of hydrogen peroxide in the hydrogen peroxide storage tank 4 is 10-25wt%.

[0044] The liquid storage tank 2 5 is pre-stored with an ammonium sulfite solution having a concentration of 0.05-0.15 wt % and a pH value of 5.5-6.5, and the ammonium sulfite solution is used as an absorption liquid.

[0045] During the use of the device, the reaction temperature is 40-160°C and the working pressure is 0.1-0.3Mpa.

[0046] Example 2

[0047] The hydrogen peroxide storage tank 4 of the present invention is made of stainless steel or polyethylene.

[0048] The liquid storage tank 1 2, liquid storage tank 2 5 and liquid storage tank 3 7 described in the present invention have the same results and all adopt horizontal steel-lined PE storage tanks.

[0049] The compressor 1, compressor 2, 9 and compressor 3, 11 described in the present invention are the same and all adopt air compressors.

[0050] The amino absorption tower 1 3 and the amino absorption tower 2 12 of the present invention have the same structure and are both made of corrosion-resistant glass fiber reinforced plastic.

[0051] Example 3

[0052] This embodiment describes a method for using a photocatalytic combined with wet ammonia absorption flue gas purification device, including the following steps:

[0053] S1. First, check whether the device is tightly connected. After the inspection, add ammonia water and ammonium sulfite solution to the liquid storage tank 1 2 and the liquid storage tank 2 5 respectively. The liquid storage tank 3 7 is an empty tank. At the same time, add Fenton reagent FeSO4 solution to the microwave photocatalytic reactor 16, and add hydrogen peroxide to the hydrogen peroxide storage tank 4 to complete the preparation before use;

[0054] S2. When in use, operate the external control box to control the metering pump 13 to inject the ammonia water in the liquid storage tank 2 into the amino solution absorption tower 3, and then connect the air inlet of the compressor 1 to the exhaust pipe of the coal-fired boiler, so that the exhaust gas discharged from the compressor 1 is introduced into the lower part of the amino solution absorption tower 3, and the SO2 in the flue gas is absorbed by the ammonia solution to produce ammonium sulfite. At the same time, the demister separates the liquid droplets entrained by the discharged gas into gas and liquid.

[0055] S3, at this time, the ammonia solution with ammonium sulfite enters the storage tank 2 5 of the solution circulation system through the drain pipe, and the flue gas with SO2 removed is transported to the microwave photocatalytic reactor 16 of the microwave photocatalytic oxidation system through the delivery pipe. The reactor generates high voltage through an adjustable microwave power supply, which is transmitted to the magnetron through a waveguide and then converted into microwaves. The electrodeless lamp generates ultraviolet radiation through microwave excitation, which excites and decomposes the FeSO4 solution to release hydroxyl free radicals OH with strong oxidizing properties, and oxidizes NO and Hg0 in the flue gas. The hydrogen peroxide storage tank 4 is measured by a flow meter to replenish the required oxidant;

[0056] The reaction mechanism is as follows:

[0057] The possible reaction between NO and Fenton's reagent (FeSO4 solution and H2O2 mixed solution) can be expressed by equations (1)-(4):

[0058] Fe 2+ +H2O2→Fe 3+ +OH - + OH (1)

[0059] ·OH+H2O2→H2O+·O2H (2)

[0060] O2H+Fe 3+ →O2+Fe 2+ + OH (3)

[0061] Fe 2+ +·OH→Fe 3+ +OH - (4)

[0062] The reaction mechanism between NO and OH and H2O2 can be expressed by equations (5)-(8):

[0063]

[0064]

[0065]

[0066] 2NO+3H2O2→2HNO3+2H2O (8)

[0067] When exposed to ultraviolet light, the following reaction occurs (9)

[0068] H2O2+hv→2·OH (9)

[0069] Hg 0 The oxidation reaction by OH and H2O2 can be expressed by equations (10) and (11):

[0070] Hg 0 +2·OH→Hg(OH)2→HgO+H2O (10)

[0071] Hg 0 +H2O2→HgO+H2O (11)

[0072] Hg generated by the reaction 2+ The added S 2+ The reaction generates insoluble HgS precipitate, which is recycled after precipitation separation. The reaction principle is as follows:

[0073] Hg 2+ +S 2- →HgS (12).

[0074] S4, the flue gas treated by the microwave photocatalytic reactor 16 is transmitted to the compressor 29 through the pipeline, and the compressor 29 sends the flue gas from the lower part of the secondary amino solution absorption system. At the same time, the mixed liquid composed of the ammonium sulfite solution in the liquid storage tank 25 and the ammonia water with ammonium bisulfite discharged from the amino solution absorption tower 13 is extracted by the metering pump 214 and transported by the three-way valve pipeline into the amino solution absorption tower 13 and the amino solution absorption tower 212, and the divalent S is added to the amino solution absorption tower 212. 2- solution, removes high-valent nitrogen oxides, nitrous acid, Hg O Highly efficient absorption;

[0075] S5. The clean flue gas after absorption is transmitted from the amino solution absorption tower 2 12 to the chimney 8 and discharged into the atmosphere. During the treatment process of the amino solution absorption tower 2 12, Hg 2+ The added S2- An insoluble HgS precipitate should be generated, and the remaining liquid is concentrated in a crystallizer (a conventional crystallizer is used, which is a conventional device used in the crystallization process to help the crystals grow rapidly and provide the conditions required for crystal nucleation) to obtain commonly used agricultural fertilizers such as ammonium sulfate and ammonium nitrate, which is beneficial to resource utilization. The excess ammonia water after concentration is then transported to a liquid storage tank 3 7, and then re-transported to a liquid storage tank 2 under the action of a metering pump 3 15 for repeated recycling.

Claims

1. A photocatalytic combined with wet ammonia absorption flue gas purification device, characterized in that: From left to right, it includes a primary amino solution absorption system, a microwave photocatalytic oxidation system, a solution circulation system and a secondary amino solution absorption system; The primary amino solution absorption system comprises a liquid storage tank, an inlet and an outlet respectively arranged at the upper and lower ends of the liquid storage tank, a pipe connected to the outlet, a metering pump arranged at the end of the pipe, the output end of the metering pump is connected to the inlet of the amino absorption tower through a two-section pipe, a demister arranged in the amino absorption tower, a compressor installed at one side of the amino absorption tower, and a flue gas discharge pipe connected to the inlet of the compressor; The microwave photocatalytic oxidation system comprises a microwave photocatalytic reactor connected to an outlet of an amino absorption tower through a delivery pipe, a hydrogen peroxide storage tank connected to the upper end of the microwave photocatalytic reactor through a connecting pipe, a flow meter arranged in the middle of the connecting pipe, and a microwave switch installed at the side end of the microwave photocatalytic reactor, wherein the microwave switch is electrically connected to the microwave photocatalytic reactor; The solution circulation system comprises a second liquid storage tank connected to the waste liquid outlet of the first amino absorption tower through a waste liquid pipe, a second metering pump connected to the outlet of the second liquid storage tank, and a three-way valve pipeline connected to the outlet of the second metering pump, and the remaining two interfaces of the three-way valve pipeline are respectively connected to the inlet of the first amino absorption tower and the inlet of the second amino absorption tower; The secondary amino solution absorption system includes a second compressor arranged at the outlet of a microwave photocatalytic reactor, a second amino solution absorption tower connected to the outlet of the second compressor, a third compressor installed at the outlet of the second amino solution absorption tower, a chimney connected to the outlet of the third compressor, a crystallizer connected to the circulation port of the second amino solution absorption tower, a third liquid storage tank fixedly connected to the side end of the crystallizer, and a third metering pump connected to the outlet of the third liquid storage tank and the inlet of the first liquid storage tank.

2. The photocatalytic combined wet ammonia absorption flue gas purification device according to claim 1 is characterized in that: The flue gas emission pipe is a tail gas emission pipe of a coal-fired boiler.

3. The photocatalytic combined wet ammonia absorption flue gas purification device according to claim 1 is characterized in that: There is ammonia water in both the amino absorption tower 1 and the amino absorption tower 2, and there is also divalent S in the amino absorption tower 2. 2- Solution.

4. The photocatalytic combined with wet ammonia absorption flue gas purification device according to claim 1 is characterized in that: The microwave photocatalytic reactor comprises a microwave reactor and an electrodeless ultraviolet lamp arranged in the microwave reactor; the electrodeless ultraviolet lamp is excited by microwaves; the radiation power of the electrodeless ultraviolet lamp is 14500 μw / cm 2 , the ultraviolet wavelength is 185-254nm.

5. The photocatalytic combined with wet ammonia absorption flue gas purification device according to claim 1 is characterized in that: When the microwave photocatalytic reactor is used, a Fenton reagent FeSO4 solution is added in advance; the FeSO4 concentration is 0.01-0.04 mol / L.

6. The photocatalytic combined with wet ammonia absorption flue gas purification device according to claim 1 is characterized in that: The concentration of hydrogen peroxide in the hydrogen peroxide storage tank is 10-25wt%.

7. The photocatalytic combined with wet ammonia absorption flue gas purification device according to claim 1 is characterized in that: The second liquid storage tank is pre-stored with an ammonium sulfite solution with a concentration of 0.05-0.15wt% and a pH value of 5.5-6.5, and the ammonium sulfite solution is used as an absorption liquid.

8. The photocatalytic combined with wet ammonia absorption flue gas purification device according to claim 1 is characterized in that: During the use of the device, the reaction temperature is 40-160°C and the working pressure is 0.1-0.3Mpa.

9. The method for using a photocatalytic combined with wet ammonia absorption flue gas purification device according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. First, check whether the device is tightly connected. After the inspection, add ammonia water and ammonium sulfite solution to liquid storage tank 1 and liquid storage tank 2 respectively. Liquid storage tank 3 is empty. At the same time, add Fenton reagent FeSO4 solution to the microwave photocatalytic reactor and add hydrogen peroxide to the hydrogen peroxide storage tank to complete the preparation before use. S2. When in use, operate the external control box to control the metering pump to start, inject the ammonia water in the liquid storage tank into the amino solution absorption tower, and then connect the air inlet of the compressor to the exhaust pipe of the coal-fired boiler, so that the exhaust gas discharged from the compressor is introduced into the lower part of the amino solution absorption tower, and the SO2 in the flue gas is absorbed by the ammonia solution to produce ammonium sulfite. At the same time, the demister separates the liquid droplets entrained in the exhaust flue gas into gas and liquid; S3. At this time, the ammonia solution with ammonium sulfite enters the second storage tank of the solution circulation system through the drain pipe, and the flue gas with SO2 removed is transported to the microwave photocatalytic reactor of the microwave photocatalytic oxidation system through the delivery pipe. The reactor generates high voltage through an adjustable microwave power supply, which is transmitted to the magnetron through a waveguide and then converted into microwaves. The electrodeless lamp generates ultraviolet radiation through microwave excitation, which excites and decomposes the FeSO4 solution to release hydroxyl free radicals OH with strong oxidizing properties, and oxidizes NO and Hg0 in the flue gas. The hydrogen peroxide storage tank is metered by a flow meter to replenish the required oxidant; S4, the flue gas treated by the microwave photocatalytic reactor is transmitted to the second compressor through the pipeline, and the second compressor sends the flue gas from the lower part of the secondary amino solution absorption system. At the same time, the ammonium sulfite solution in the second liquid storage tank and the mixed liquid consisting of ammonium bisulfite and ammonia water discharged from the amino solution absorption tower 1 are extracted by the second metering pump and transported through the three-way valve pipeline into the amino solution absorption tower 1 and the amino solution absorption tower 2. At the same time, divalent S is added to the amino solution absorption tower 2. 2- Solution, which can efficiently absorb high-valent nitrogen oxides, nitrous acid and HgO in flue gas; S5, the clean flue gas after absorption is transmitted from the amino solution absorption tower 2 to the chimney 6 and discharged into the atmosphere; during the treatment process of the amino solution absorption tower 2, Hg 2+ The added S 2- The reaction generates insoluble HgS precipitate, and the remaining liquid is concentrated in a crystallizer to obtain common agricultural fertilizers such as ammonium sulfate and ammonium nitrate, which is beneficial to resource utilization. The excess ammonia water after concentration is then transported to liquid storage tank three, and then re-transported to liquid storage tank one under the action of metering pump three for repeated recycling.

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