A flue gas purification system and method based on modified biochar-activated persulfate

Abstract

The present invention provides a flue gas purification system and method based on modified biochar activating persulfate. In the present invention, first, a microwave spray floating multi-zone modification bed is used to activate the modified biochar, and then the modified biochar is used in a pump spray counter-attacking bubble bed to induce free radicals / active components to remove SO2, NO x and Hg 0 in the flue gas by simultaneous oxidation removal, with a very high simultaneous removal efficiency of multiple pollutants. The present invention proposes to use biomass straw to prepare modified biochar to replace traditional metal oxides to activate free radicals to remove flue gas pollutants, which can effectively overcome the deficiencies of metal oxides such as easy decomposition and inactivation in acidic solutions and leakage of metal ions. At the same time, it also has the advantages of wide sources of biochar raw materials and easy treatment of deactivated catalysts, and is a new type of flue gas purification method and system with broad application prospects.

Description

Technical Field

[0001] The invention belongs to the field of combustion flue gas pollutant control, and particularly relates to a method and a system for simultaneously desulfurizing, denitrifying and removing mercury by activating persulfate with modified biochar based on a microwave spray floating multi-zone modification bed. Background Technique

[0002] Atmospheric pollutants such as SO2, NO x and Hg emitted from fossil fuel combustion can cause serious hazards such as acid rain, photochemical smog, carcinogenesis and teratogenesis. Therefore, it is of great scientific significance and industrial value to research and develop environmentally friendly, economical and efficient combustion flue gas desulfurization, denitrification and mercury removal technologies and processes.

[0003] In the past three decades, scientific and technical personnel and engineers at home and abroad have successively developed various combustion flue gas desulfurization, denitrification and mercury removal technologies and processes. However, due to the limitations and timeliness of technological development, most of the existing combustion flue gas desulfurization, denitrification and mercury removal technologies and processes were only targeted at removing a certain pollutant at the beginning of research and development (for example, only SO2, NO x or Hg 0 among them), and it is difficult to achieve simultaneous removal of multiple pollutants. For example, the mainstream flue gas desulfurization and denitrification technologies currently used in power plants and boilers at home and abroad are the calcium-based wet flue gas desulfurization process and the ammonia-based selective catalytic reduction denitrification method (i.e., SCR denitrification process), respectively. Although these two methods can achieve staged desulfurization and denitrification, they cannot achieve simultaneous removal of two pollutants in a single reactor, let alone removal of heavy metal mercury in coal-fired flue gas. Therefore, if further removal of mercury in coal-fired flue gas is to be achieved, coal-fired flue gas mercury removal technologies and devices need to be further installed on this basis. However, although the combined use of the three processes can achieve simultaneous desulfurization, denitrification and mercury removal of flue gas, it will also lead to many deficiencies such as the entire removal system being huge and complex, occupying a large area, and having high initial investment and operating costs of the system. At present, there are more than 500,000 medium and small-sized coal-fired boilers, industrial kilns and waste incinerators in industrial and civil industries in China. If enterprise users of these medium and small-sized combustion facilities install desulfurization, denitrification and mercury removal devices and processes for SO2, NO x and mercury at the same time, they will face extremely huge economic pressure and consume a great deal of energy, which is not conducive to the large-scale popularization and implementation of relevant removal technologies and policies.

[0004] To sum up, if SO2, NO xSimultaneous removal of sulfur, nitrogen oxides, and mercury is expected to significantly reduce the complexity and operating costs of the system and has good market application prospects. Currently, flue gas simultaneous desulfurization, denitrification, and demercuration technologies that have been developed mainly include catalysis, adsorption, plasma removal, complexation absorption, traditional oxidation, and advanced oxidation with free radicals. The plasma method has defects such as poor reliability and high operating energy consumption. The adsorption method has defects such as low removal efficiency (especially the removal efficiency of the key component NO is very low) and the reactor needs to operate intermittently. The complexation method (using complex iron and cobalt ammonia solution absorption) has disadvantages such as large regeneration loss of complexing agents and high regeneration energy consumption. The traditional oxidation method has problems such as high reagent prices (such as sodium chlorite and potassium permanganate, etc.), low oxidation ability (such as hydrogen peroxide and persulfate, etc.), large consumption of oxidants (easy to decompose by itself), and secondary pollution (such as the products of potassium permanganate and chlorite are difficult to treat). The advanced oxidation technology with free radicals, which has received wide attention currently, has achieved great development, but there are still technical and economic problems such as large investment, high operating costs, and poor technical maturity. Therefore, these technologies are still far from industrial application and still require more research and efforts from scientific and technological personnel in this field.

[0005] Among various common simultaneous removal technologies, the advanced oxidation with free radicals for simultaneous removal has comprehensive technical advantages such as strong oxidation ability and green and environmental protection process, and it is a flue gas simultaneous removal technology process with good development prospects. However, the development of existing advanced oxidation with free radicals for simultaneous removal technologies is relatively slow, and the main problems can be summarized as the following aspects: (I) The photochemical activation removal technology, microwave activation removal technology, and electrochemical activation removal technology have deficiencies such as complex devices, large initial investment, and high operating energy consumption; (II) The transition metal ion activation removal technology has problems such as difficult separation and recovery of transition metal ions and secondary pollution; (III) The thermal activation removal technology has problems such as low free radical activation efficiency and low pollutant removal efficiency; (IV) The transition metal oxide activation removal technology has problems such as easy decomposition and inactivation of metal oxides in acidic solutions. The above 4 key problems are the main bottlenecks or obstacles hindering the large-scale industrial application of the advanced oxidation with free radicals for simultaneous desulfurization, denitrification, and demercuration technologies. In addition, a large number of scientific researches and industrial practices have confirmed that the main rate control step of the gas-liquid-solid three-phase reaction process is the mass transfer process. Therefore, using traditional reactors for simultaneous desulfurization, denitrification, and demercuration easily leads to deficiencies such as large reactor volume and high operating energy consumption, and it is necessary to further research and develop efficient multiphase reactors that can achieve good mixing and enhanced mass transfer. Summary of the Invention

[0006] In view of the above series of technical problems and bottlenecks, the present invention provides a system and method for simultaneously desulfurizing, denitrifying and mercury-removing by activating persulfate with modified biochar based on a microwave spray floating multi-zone modification bed. In the present invention, first, the microwave spray floating multi-zone modification bed is used to activate and modify biochar, and then the modified biochar is used to induce free radicals in the pump spray counter-attacking bubble bed to oxidize SO2, NO x and Hg 0 in the flue gas into H2SO4, HNO3 and Hg 2+ simultaneously. The generated H2SO4, HNO3 and Hg 2+ can be comprehensively and resourcefully utilized through multi-stage separation, and there is no secondary pollution in the removal process.

[0007] Basic principles of the method and system in the present invention:

[0008] (1) Biochar modification process: First, microwave is used in combination with water vapor to activate biochar to expand the pores of biochar and increase the specific surface area. Then, microwave and H2S / O2 are used to modify biochar synergistically, aiming to generate sulfur (S)- and oxygen (O)-containing active sites on the surface of biochar; finally, microwave and NH4Cl are used to modify biochar synergistically, aiming to generate nitrogen (N)- and chlorine (Cl)-containing active sites on the surface of biochar. The above multi-step modification process can be represented by the following equations (1)-(3):

[0009]

[0010] (2) Process of modified biochar activating persulfate to generate free radicals and active components: Modified biochar is used to activate persulfate (S2O8 2- ) in the pump spray counter-attacking bubble bed 11 to generate highly oxidizing free radicals / active components (such as SO4 - ·, ·OH, ·O2 - , Cl· and O2 1 ), and the specific process can be represented by the following chemical reaction (4):

[0011] Biochar-O, S, N, Cl+S2O8 2- →SO4 - ·+·OH+O2 1 +·O2 - +Cl· (4)

[0012] (3) Pollutant removal process: Highly active free radicals / active components (such as SO4 - ·, ·OH, ·O2 - , Cl· and O2 1 ) are used to oxidize / attack SO2, NO x and Hg 0 in the flue gas, and SO2, NOx and Hg 0 are respectively oxidized to H2SO4, HNO3 and Hg 2 + , thus realizing the simultaneous removal of multiple pollutants. The specific process can be represented by the following chemical reactions (5)-(7):

[0013] SO4 - · + ·OH + O2 1 + ·O2 - + SO2 + H2O → H2SO4 (5)

[0014] SO4 - · + ·OH + O2 1 + ·O2 - + NO x + H2O → HNO3 (6)

[0015] SO4 - · + ·OH + O2 1 + ·O2 - + Cl· + Hg 0 + H2O → Hg 2+ (7)

[0016] The biochar that has lost its activity after the reaction can be returned to the microwave floating multi-zone modification bed 3, and new activation modification regeneration can be achieved through the activation modification process such as equations (1)-(3), enabling it to regain the ability of new activated free radicals, thereby realizing the recycling of the catalyst. And the generated H2SO4, HNO3 and Hg 2+ can be comprehensively resource-utilized through the multi-stage comprehensive resource-utilization system at the tail, and there is no secondary pollution in the whole removal process.

[0017] Based on the above principle, the present invention designs a flue gas purification system based on modified biochar-activated persulfate. The system includes a microwave floating multi-zone modification bed 3 for biochar modification and a pump spray counter-attack bubble bed 11 for inducing free radical desulfurization, denitrification and mercury removal; the biochar is modified by using microwave and H2S / O2 synergistically and by using microwave and NH4Cl synergistically, and the obtained modified biochar is injected into the pump spray counter-attack bubble bed 11.

[0018] The microwave spray floating multi-zone modification bed 3 is provided with three different zones, which are, from bottom to top, a microwave activation zone A1, an H2S modification zone A2, and an ammonium chloride modification zone A3. The microwave activation zone A1 is longitudinally provided with a plurality of partitions perpendicular to the bottom of the reactor, namely, microwave activation zone partitions 9. A plurality of microwave emitters 4 are provided on the inner side wall surface of the microwave spray floating multi-zone modification bed 3 and on the microwave activation zone partitions 9. One set of H2S gas distribution device 7 and one set of ammonium chloride solution atomization device 8 are provided at the upper part of the microwave spray floating multi-zone modification bed 3. The H2S gas distribution device 7 and the ammonium chloride solution atomization device are respectively connected to an H2S storage tower 5 and an ammonium chloride storage tower 6. A set of gas-solid nozzle array for injecting biochar is provided at the bottom of the microwave spray floating multi-zone modification bed 3. The gas-solid nozzle array at the bottom of the microwave spray floating multi-zone modification bed 3 is connected to a gas-solid mixer 1, and the top of the microwave spray floating multi-zone modification bed 3 is connected to a pressurization device 10. The bottom of the microwave spray floating multi-zone modification bed 3 is provided with a microwave spray floating multi-zone modification bed biochar inlet d, and the top is provided with a microwave spray floating multi-zone modification bed outlet e. Further, the microwave spray floating multi-zone modification bed biochar inlet d is connected to the gas-solid mixer 1, and the microwave spray floating multi-zone modification bed outlet e is connected to the pressurization device 10.

[0019] The pump spray impact bubble bed 11 is internally provided with a gas-liquid separation device 13, a bubbling device 14, and a pump spray impact device 12. The bottom of the pump spray impact bubble bed 11 is provided with a pump spray impact bubble bed flue gas inlet q. The flue gas to be purified enters the pump spray impact bubble bed 11 through the pump spray impact bubble bed flue gas inlet q. The top of the pump spray impact bubble bed 11 is provided with a pump spray impact bubble bed flue gas outlet h. The purified flue gas is discharged through the pump spray impact bubble bed flue gas outlet h.

[0020] The pump spray impact bubble bed 11 is provided with a reaction solution discharge port i and a pump spray impact bubble bed solution inlet p on the side, and a pump spray impact bubble bed modified biochar inlet g at the left bottom. It is connected to the pressurization device outlet f of the pressurization device 10 through a pipeline, and a fan 20 for transporting the modified biochar is provided on this connection pipeline.

[0021] A circulating system composed of a liquid-solid separation device 15 and a persulfate solution tower 16 is provided on the side of the pump spray impact bubble bed 11, and is respectively connected to the reaction solution discharge port i and the pump spray impact bubble bed solution inlet p through pipelines. A solution pump one 17, a solution pump two 18, and a solution pump three 19 for transporting the solution are provided on the pipelines.

[0022] The liquid-solid separation device 15 is connected to the reaction solution discharge port i through a pipeline. The liquid-solid separation device 15 is connected to the gas-solid mixer biochar inlet b of the gas-solid mixer 1 through the liquid-solid separation device waste biochar discharge port k, and the recycling of biochar can be realized.

[0023] Further, a plurality of microwave emitters 4 are arranged on the wall surfaces on both the left and right sides of the microwave spray floating multi-zone modification bed 3 and on both the front and back sides of the microwave activation zone partition 9, and the microwave emitters are arranged in a staggered pattern. The lateral spacing and longitudinal spacing L0 between each pair of microwave emitters 4 are both between 5 cm and 50 cm, and the lateral and longitudinal spacings are equal. The nozzles in the gas-solid nozzle array at the bottom of the microwave spray floating multi-zone modification bed 3 are arranged in a staggered pattern, and the longitudinal and lateral spacings M0 are kept the same.

[0024] Further, the microwave activation zone A1 is divided into a plurality of sub-activation zones by a plurality of microwave activation zone partitions 9, and the spacing L1 between each pair of sub-activation zones is the same. The optimized distance of L1 needs to be kept between 10 cm and 60 cm. The height H1 of the microwave activation zone A1 is between 80 cm and 500 cm, the height H2 of the H2S modification zone A2 is between 30 cm and 150 cm, and the height H3 of the ammonium chloride modification zone A3 is between 30 cm and 200 cm.

[0025] Further, the microwave radiation power density inside the microwave activation zone (A1) needs to be kept between 1000 W / m 3 ~5000 W / m 3 The microwave activation power inside the H2S modification zone (A2) needs to be kept between 200 W / m 3 ~1000 W / m 3 The microwave activation power inside the ammonium chloride modification zone (A3) needs to be kept between 200 W / m 3 ~1000 W / m 3 between.

[0026] Further, pump spray impact breakage devices 12 are provided on the inner walls on all four sides of the pump spray impact breakage bed 11, and the pump spray impact breakage devices 12 are arranged in a staggered pattern, and the lateral and longitudinal spacings are kept equal. The pump spray impact breakage devices 12 arranged on the opposite (e.g., left and right or front and back) side walls are all on the same horizontal line to ensure that opposite impact breakage of bubbles can be achieved, thereby strengthening mixing and mass transfer. The longitudinal and lateral intervals K1 between each pair of pump spray impact breakage devices 12 need to be kept between 50 cm and 120 cm, and the horizontal distance L2 between the nozzles of each pair of oppositely arranged pump spray impact breakage devices (12) needs to be kept between 80 cm and 500 cm.

[0027] Further, the H2O concentration at the water vapor inlet of the gas-solid mixer needs to be kept between 2% and 15%. The H2S concentration ejected by the H2S gas distribution device 7 needs to be kept between 20 ppm and 200 ppm, and the concentration of the ammonium chloride solution ejected by the ammonium chloride solution atomization device 8 needs to be kept between 0.01 mol / L and 1.0 mol / L.

[0028] Furthermore, the optimized persulfate concentration range for the simultaneous desulfurization, denitrification, and mercury removal inside the bubble bed 11 by pump spraying is 0.02 mol / L to 3.0 mol / L, the optimized solution pH is 0.1 to 7.5, the optimized reaction temperature is 30°C to 80°C, and the optimized dosage of modified biochar is 20 mg / L to 800 mg / L.

[0029] Furthermore, the optimized initial concentration ranges of flue gas pollutants SO2, NO x and Hg 0 are 100 - 2000 ppm, 300 - 1500 ppm, and 50 μg / m 3 - 500 μg / m 3 respectively. The optimized particle size of the modified biochar is 0.001 μm to 0.5 μm.

[0030] For the system of simultaneous desulfurization, denitrification, and mercury removal by activating persulfate with modified biochar in the microwave spray floating multi - zone modification bed, the operation processes of the biochar modification and pollutant removal systems are as follows:

[0031] I. Air enters the gas - solid mixer 1 from the air inlet a of the gas - solid mixer, biochar enters the gas - solid mixer 1 from the biochar inlet b of the gas - solid mixer, and water vapor enters the gas - solid mixer 1 from the water vapor inlet c of the gas - solid mixer. After the three substances are well - mixed in the gas - solid mixer 1, they enter the microwave spray floating multi - zone modification bed 3 through the biochar inlet d of the microwave spray floating multi - zone modification bed. In the microwave activation zone A1, through the synergistic activation of microwave and water vapor, the biochar can achieve rapid pore expansion and an increase in specific surface area. The biochar that has been fully circulated and activated in the microwave activation zone A1 then continues to enter the H2S modification zone A2, where it is synergistically modified by microwave and H2S to load the active sulfur S component. The biochar modified in the H2S modification zone A2 then continues to enter the ammonium chloride modification zone A3, where it is synergistically modified by microwave and ammonium chloride to load the active nitrogen (N) and active chlorine (Cl) components.

[0032] II. The biochar modified in the microwave spray floating multi - zone modification bed 3 enters the pressurization device 10 through the outlet e of the microwave spray floating multi - zone modification bed for pressurization, and then is transported through the pipeline from the outlet f of the pressurization device 10 to the pump - spray counter - impact bubble bed 11 for radical activation and pollutant removal reactions. The modified biochar enters the persulfate solution reaction zone in the pump - spray counter - impact bubble bed 11 through the modified biochar inlet g of the pump - spray counter - impact bubble bed for radical activation and pollutant oxidation and removal reactions. During the radical activation and pollutant removal reactions, the pump - spray counter - impact device 12 starts the counter - spray mode, which can achieve efficient gas - liquid - solid mixing and enhance the non - homogeneous mass transfer efficiency.

[0033] III. Flue gas from a coal-fired boiler enters the pump-spray counter-attacking bubbling bed 11 through the flue gas inlet q of the pump-spray counter-attacking bubbling bed, and after bubbling through the bubbling device 14, it enters the reaction zone and mixes with the persulfate solution. In the persulfate solution in the reaction zone, free radicals induced by the activation of persulfate by modified biochar (such as SO4 - ·, ·OH, ·O2 - and O2 1 ) react with SO2, NO x and Hg 0 in the flue gas, and oxidize SO2, NO x and Hg 0 into H2SO4, HNO3 and Hg 2+ respectively, thus realizing the simultaneous removal of multiple pollutants. After the cleaned flue gas is separated from the solution by the gas-liquid separation device 13, it is sent from the flue gas outlet h of the pump-spray counter-attacking bubbling bed to the chimney at the tail and discharged into the atmosphere. The reaction waste solution can be discharged by the solution pump 17 into the liquid-solid separation device 15 to separate the solution and biochar. The separated waste biochar can be sent from the waste biochar discharge port k of the liquid-solid separation device back to the microwave spray floating multi-zone modification bed 3 through the biochar inlet b of the gas-solid mixer for re-activation and modification. The separated solution passes through the solution circulation outlet 1 of the liquid-solid separation device and is discharged by the solution pump 18 into the persulfate solution tower 16. Then, after replenishing new persulfate solution, it is sent back into the pump-spray counter-attacking bubbling bed 11 through the outlet o of the persulfate solution tower to participate in the removal reaction. The newly replenished persulfate solution is sent into the persulfate solution tower 16 through the new liquid inlet (n of the persulfate solution tower. After multiple cycles, the saturated waste solution containing H2SO4, HNO3 and Hg 2+ is discharged through the waste liquid discharge port j of the liquid-solid separation device and sent to the multi-stage comprehensive resource utilization system at the tail.

[0034] IV. The multi-stage comprehensive resource utilization system includes a mercury separation device, an ammonia neutralizing acid device, and a flue gas waste heat evaporation crystallization fertilizer preparation device. In the mercury separation device, Hg 2+ can be separated and recovered by reacting with the addition of divalent sulfur ions to produce mercury sulfide precipitation. In the ammonia neutralizing acid device, H2SO4 and HNO3 can react with the addition of ammonia to produce ammonium sulfate and ammonium nitrate. In the flue gas waste heat evaporation crystallization fertilizer preparation device, agricultural fertilizers are prepared after the waste heat evaporation crystallization of the coal-fired boiler flue gas. Therefore, the entire removal process not only has no secondary pollution, but also can obtain important resources such as mercury and agricultural fertilizers, and has good development and application prospects.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) In the existing technologies for removing multiple pollutants from flue gas by advanced oxidation with free radicals in this field, there are generally various technical problems. For example, in high-energy free radical activation and removal technologies such as ultraviolet light, microwave, electrochemistry, and ultrasonic waves, there are deficiencies such as complex devices, high initial investment, and high operating energy consumption. In the transition metal ion activation and removal technology, there are problems such as difficult recovery of metal ions and secondary pollution. In the thermal activation and removal technology, there are difficulties such as low free radical yield and low pollutant removal efficiency. The transition metal oxide activation and removal technology has advantages such as simple process and low device requirements, and the metal oxide catalyst can be recycled. However, common transition metal oxide catalysts mainly include iron oxide, copper oxide, manganese oxide, cobalt oxide, cerium oxide, and various mixed metal oxides mentioned above. However, these transition metal oxides are all basic oxides and are easily corroded and decomposed in acidic solutions (the oxidation removal products of this process are sulfuric acid and nitric acid), and then deactivate due to poisoning, resulting in a very high application cost. The use of biomass straw to prepare modified biochar to replace traditional transition metal oxides for activating free radicals to remove flue gas pollutants proposed in the present invention can effectively overcome the deficiencies such as easy decomposition and inactivation of metal oxides in acidic solutions and metal ion leakage. At the same time, it also has advantages such as wide sources of biochar raw materials and easy treatment of deactivated catalysts, and has good technical and economic advantages.

[0037] (2) The existing adsorbent modification technologies and processes usually have complex modification processes and devices, resulting in too long process flows and complex devices, and then huge initial investment and operating costs. Therefore, developing energy-saving and low-carbon modification technologies and processes with low energy consumption, low cost, and short process flows is an important research topic and development direction in this field. The microwave spray floating multi-zone modification bed developed in the present invention can achieve multi-stage activation and modification in one reactor, and has outstanding advantages such as simple modification device and short process flow, and has good development prospects.

[0038] (3) The oxidation of SO2, NO x and Hg 0 in flue gas induced by solid catalyst activation of persulfate to generate free radicals is a gas-liquid-solid three-phase reaction process. In the complex heterogeneous reaction process, the oxidation rate of free radicals is often extremely fast. Therefore, the multi-phase mass transfer process is usually the rate-limiting step of the entire removal process. How to simply and efficiently strengthen the mass transfer process is the key to achieving high-efficiency pollutant removal. However, the mass transfer efficiency of common bubble column reactors and spray tower reactors in this field is relatively low and cannot meet the requirements of industrial applications. The pump spray counter-jet bubble bed developed in the present invention has extremely high enhanced mixing and mass transfer performance, can greatly promote the heterogeneous removal process, and then achieve higher pollutant removal efficiency (the removal efficiency of all three pollutants can reach up to 100%).

[0039] In summary, the modified and removal system developed by the present invention has outstanding comprehensive advantages such as simple and compact structure, short process flow, high mass transfer efficiency, high simultaneous removal efficiency of pollutants, and green and environmental protection in the process. It is a new type of flue gas purification method and system with broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic structural diagram of a system for simultaneously desulfurizing, denitrifying, and removing mercury by activating persulfate with modified biochar in a microwave spray floating multi-zone modification bed.

[0041] Figure 2 It is a schematic diagram of the layout and dimensions of microwave emitters on the side wall surface and the partition board.

[0042] Figure 3 It is a schematic diagram of the layout and dimensions of the gas-solid nozzle array at the bottom of the microwave spray floating multi-zone modification bed.

[0043] Figure 4 It is a schematic diagram of the layout and dimensions of the pump spray impact device on the side of the pump spray impact bubble-breaking bed.

[0044] Figure 5 It is a schematic structural diagram of the pump spray impact device.

[0045] Reference numerals: 1. Gas-solid mixer; 2. Gas-solid nozzle array; 3. Microwave spray floating multi-zone modification bed; 3-1 Wall surface of the microwave spray floating multi-zone modification bed; 3-2 Bottom wall surface of the microwave spray floating multi-zone modification bed; 4. Microwave emitter; 5. H2S storage tower; 6. Ammonium chloride storage tower; 7. H2S gas distribution device; 8. Ammonium chloride solution atomization device; 9. Microwave activation zone partition; 10. Booster device; 11. Pump spray impact bubble-breaking bed; 11-1 Wall surface of the pump spray impact bubble-breaking bed; 12. Pump spray impact device; 12-1 Solution upper and lower inlets of the pump spray impact device; 12-2 Accelerating tube of the pump spray impact device; 12-3 High-speed jet nozzle of the pump spray impact device; 12-4 Installation and fixing base of the pump spray impact device; 13. Gas-liquid separation device; 14. Bubbling device; 15. Liquid-solid separation device; 16. Persulfate solution tower; 17. Solution pump 1; 18. Solution pump 2; 19. Solution pump 3; 20. Fan; a. Air inlet of the gas-solid mixer; b. Biochar inlet of the gas-solid mixer; c. Steam inlet of the gas-solid mixer; d. Biochar inlet of the microwave spray floating multi-zone modification bed; e. Outlet of the microwave spray floating multi-zone modification bed; f. Outlet of the booster device; g. Modified biochar inlet of the pump spray impact bubble-breaking bed; h. Flue gas outlet of the pump spray impact bubble-breaking bed; i. Reaction solution discharge port; j. Waste liquid discharge port of the liquid-solid separation device; k. Waste biochar discharge port of the liquid-solid separation device; l. Solution circulation outlet of the liquid-solid separation device; m. Circulating liquid inlet of the persulfate solution tower; n. Supplementary fresh liquid inlet of the persulfate solution tower; o. Outlet of the persulfate solution tower; p. Solution inlet of the pump spray impact bubble-breaking bed; q. Flue gas inlet of the pump spray impact bubble-breaking bed Detailed implementation manners

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0047] As Figure 1 shown, a system for simultaneously desulfurizing, denitrifying and mercury-removing by activating persulfate with modified biochar based on a microwave spray floating multi-zone modification bed includes a microwave spray floating multi-zone modification bed 3 for biochar modification and a pump spray impact bubble-breaking bed 11 for inducing free radicals for desulfurization, denitrification and mercury-removing; the biochar is modified by using microwave and H2S / O2 and by using microwave and NH4Cl, and the obtained modified biochar is injected into the pump spray impact bubble-breaking bed 11.

[0048] The microwave spray floating multi-zone modification bed 3 is provided with three different zones, which are the microwave activation zone A1, the H2S modification zone A2, and the ammonium chloride modification zone A3 from bottom to top. The microwave activation zone A1 is longitudinally provided with a plurality of partitions perpendicular to the bottom of the reactor, namely the microwave activation zone partitions 9. A plurality of microwave emitters 4 are provided on the inner side wall surface of the microwave spray floating multi-zone modification bed 3 and the microwave activation zone partitions 9. One set of H2S gas distribution device 7 and one set of ammonium chloride solution atomization device 8 are provided on the upper part of the microwave spray floating multi-zone modification bed 3. The H2S gas distribution device 7 and the ammonium chloride solution atomization device are respectively connected to the H2S storage tower 5 and the ammonium chloride storage tower 6.

[0049] A set of gas-solid nozzle array 2 for spraying biochar is provided at the bottom of the microwave spray floating multi-zone modification bed 3. The gas-solid nozzle array at the bottom of the microwave spray floating multi-zone modification bed 3 is connected to the gas-solid mixer 1, and the top of the microwave spray floating multi-zone modification bed 3 is connected to the pressurizing device 10; the bottom of the microwave spray floating multi-zone modification bed 3 is provided with a biochar inlet d of the microwave spray floating multi-zone modification bed and the top is provided with a biochar outlet e of the microwave spray floating multi-zone modification bed. Further, the biochar inlet d of the microwave spray floating multi-zone modification bed is connected to the gas-solid mixer 1, and the biochar outlet e of the microwave spray floating multi-zone modification bed is connected to the pressurizing device 10.

[0050] The pump spray impact bubble bed 11 is internally provided with a gas-liquid separation device 13, a bubbling device 14, and a pump spray impact device 12; the bottom of the pump spray impact bubble bed 11 is provided with a flue gas inlet q of the pump spray impact bubble bed. The flue gas to be purified enters the pump spray impact bubble bed 11 from the flue gas inlet q of the pump spray impact bubble bed. The top of the pump spray impact bubble bed 11 is provided with a flue gas outlet h of the pump spray impact bubble bed. The purified flue gas is discharged through the flue gas outlet h of the pump spray impact bubble bed.

[0051] The pump spray impact bubble bed 11 is provided with a reaction solution discharge port i and a pump spray impact bubble bed solution inlet p on the side. The left bottom is provided with a modified biochar inlet g of the pump spray impact bubble bed, and is connected to the pressurizing device outlet f of the pressurizing device 10 through a pipeline, and a fan 20 for transporting the modified biochar is provided on the connecting pipeline.

[0052] A circulation system composed of a liquid-solid separation device 15 and a persulfate solution tower 16 is provided on the side of the pump spray impact bubble bed 11, and is respectively connected to the reaction solution discharge port i and the pump spray impact bubble bed solution inlet p through pipelines, and solution pumps one 17, two 18, and three 19 for transporting the solution are provided on the pipelines.

[0053] The persulfate solution tower 16 is provided with a persulfate solution tower circulating liquid inlet m, a persulfate solution tower fresh liquid supplement inlet n, and a persulfate solution tower outlet o; the persulfate solution tower outlet o is connected to the pump spray counter-breaking bubble bed solution inlet p, and fresh liquid is supplemented to the persulfate solution tower 16 through the persulfate solution tower fresh liquid supplement inlet n; the persulfate solution tower circulating liquid inlet m is connected to the liquid-solid separation device solution circulation outlet 1 of the liquid-solid separation device 15.

[0054] The liquid-solid separation device 15 is connected to the reaction solution discharge port i through a pipeline. The liquid-solid separation device 15 is connected to the gas-solid mixer biochar inlet b of the gas-solid mixer 1 through the liquid-solid separation device waste biochar discharge port k, enabling the recycling of biochar; the liquid-solid separation device 15 is also provided with a liquid-solid separation device waste liquid discharge port j to discharge the waste liquid.

[0055] As Figure 2 and Figure 3 shown, multiple microwave emitters 4 are arranged on the wall surfaces on both the left and right sides of the microwave spray floating multi-zone modification bed 3 and on both the front and back sides of the microwave activation zone partition 9, and the microwave emitters are arranged in a flush arrangement. The horizontal spacing and vertical spacing L0 between each pair of microwave emitters 4 are both in the range of 5 cm to 50 cm, and the horizontal and vertical spacings are equal. The nozzles in the gas-solid nozzle array at the bottom of the microwave spray floating multi-zone modification bed 3 are arranged in a flush arrangement, and the longitudinal and horizontal spacings M0 are the same.

[0056] As Figure 1 shown, the microwave activation zone A1 is divided into multiple sub-activation zones by multiple microwave activation zone partitions 9, and the spacing L1 between each sub-activation zone is the same. The optimized distance of L1 needs to be maintained in the range of 10 cm to 60 cm. The height H1 of the microwave activation zone A1 is in the range of 80 cm to 500 cm, the height H2 of the H2S modification zone A2 is in the range of 30 cm to 150 cm, and the height H3 of the ammonium chloride modification zone A3 is in the range of 30 cm to 200 cm.

[0057] The microwave radiation power density inside the microwave activation zone A1 needs to be maintained between 1000 W / m 3 and 5000 W / m 3 ; the microwave activation power inside the H2S modification zone A2 needs to be maintained between 200 W / m 3 and 1000 W / m 3 ; the microwave activation power inside the ammonium chloride modification zone A3 needs to be maintained between 200 W / m 3 and 1000 W / m 3 .

[0058] As Figure 4As shown in the figure, pump jet impact devices 12 are provided on the inner walls on all four sides of the bubble-breaking bed 11. The pump jet impact devices 12 are arranged in a staggered pattern, and the horizontal and vertical spacings are equal. The pump jet impact devices 12 arranged on the opposite (e.g., left and right or front and back) side walls are all on the same horizontal line to ensure that the bubbles can be broken by opposite impacts, thereby enhancing mixing and mass transfer. The longitudinal and horizontal intervals K1 between each pair of pump jet impact devices 12 need to be maintained between 50 cm and 120 cm, while the horizontal distance L2 between the nozzles of each pair of oppositely arranged pump jet impact devices 12 needs to be maintained between 80 cm and 500 cm.

[0059] As Figure 5 shown in the figure, the pump jet impact device 12 includes the upper and lower solution inlets 12-1 of the pump jet impact device, the acceleration tube 12-2 of the pump jet impact device, the high-speed jet nozzle 12-3 of the pump jet impact device, and the installation and fixing base 12-4 of the pump jet impact device. There are two upper and lower solution inlets 12-1 of the pump jet impact device, which are relatively installed on the installation and fixing base 12-4 of the pump jet impact device.

[0060] The concentration of H2O at the water vapor inlet of the gas-solid mixer needs to be maintained between 2% and 15%. The concentration of H2S ejected by the H2S gas distribution device 7 needs to be maintained between 20 ppm and 200 ppm, while the concentration of the ammonium chloride solution ejected by the ammonium chloride solution atomization device 8 needs to be maintained between 0.01 mol / L and 1.0 mol / L. Further, the optimized persulfate concentration range for simultaneous desulfurization, denitrification, and mercury removal inside the pump jet bubble-breaking bed 11 is 0.02 mol / L to 3.0 mol / L, the optimized solution pH is 0.1 to 7.5, the optimized reaction temperature is 30°C to 80°C, and the optimized dosage of modified biochar is 20 mg / L to 800 mg / L.

[0061] The flue gas pollutants SO2, NO x and Hg 0 The optimized initial concentration ranges are 100 - 2000 ppm, 300 - 1500 ppm, and 50 μg / m 3 to 500 μg / m 3 . The optimized particle size of the modified biochar is 0.001 μm to 0.5 μm.

[0062] Based on the microwave spray floating multi-zone modified bed modified biochar activated persulfate simultaneous desulfurization, denitrification, and mercury removal system, the operation process of the biochar modification and pollutant removal system is as follows:

[0063] I. Air enters the gas-solid mixer 1 from the air inlet a of the gas-solid mixer, biochar enters the gas-solid mixer 1 from the biochar inlet b of the gas-solid mixer, and water vapor enters the gas-solid mixer 1 from the water vapor inlet c of the gas-solid mixer. After the three substances are well mixed in the gas-solid mixer 1, they enter the microwave spray floating multi-zone modification bed 3 through the biochar inlet d of the microwave spray floating multi-zone modification bed. In the microwave activation zone A1, through the synergistic activation of microwave and water vapor, the biochar can achieve rapid pore expansion and increase in specific surface area. The biochar after sufficient cyclic activation in the microwave activation zone A1 continues to enter the H2S modification zone A2, where it is synergistically modified by microwave and H2S to load the active sulfur S component. The biochar after modification in the H2S modification zone A2 continues to enter the ammonium chloride modification zone A3, where it is synergistically modified by microwave and ammonium chloride to load the active nitrogen (N) and active chlorine (Cl) components.

[0064] II. The biochar modified in the microwave spray floating multi-zone modification bed 3 enters the pressurization device 10 through the outlet e of the microwave spray floating multi-zone modification bed for pressurization, and then is transported through a pipeline from the outlet f of the pressurization device 10 to the pump spray counter-jet bubble bed 11 for radical activation and pollutant removal reactions. The modified biochar enters the persulfate solution reaction zone in the pump spray counter-jet bubble bed 11 through the modified biochar inlet g of the pump spray counter-jet bubble bed for radical activation and pollutant oxidation and removal reactions. During the radical activation and pollutant removal reactions, the pump spray counter-jet device 12 starts the counter-jet mode, which can achieve efficient mixing of gas, liquid and solid, and enhance the mass transfer efficiency of heterogeneous phase.

[0065] III. The flue gas from the coal-fired boiler enters the pump spray counter-jet bubble bed 11 from the flue gas inlet q of the pump spray counter-jet bubble bed, and after bubbling through the bubbling device 14, it enters the reaction zone to be mixed with the persulfate solution. In the persulfate solution in the reaction zone, the radicals (such as SO4 - ·, ·OH, ·O2 - and O2 1 ) activated by the modified biochar react with SO2, NO x and Hg 0 in the flue gas to occur oxidation reactions, and SO2, NO x and Hg 0 are respectively oxidized to H2SO4, HNO3 and Hg 2+, thereby achieving the simultaneous removal of multiple pollutants. After the cleaned flue gas is separated from the solution by the gas-liquid separator 13, it is sent into the chimney at the tail from the outlet h of the pump spray counter-attacking bubbling bed flue gas and discharged into the atmosphere. The reaction waste solution can be discharged by the solution pump 17 into the liquid-solid separator 15 to separate the solution and biochar. The separated waste biochar can be re-fed into the microwave spray floating multi-zone modification bed 3 from the waste biochar discharge port k of the liquid-solid separator through the biochar inlet b of the gas-solid mixer for re-activation and modification. The separated solution passes through the solution circulation outlet 1 of the liquid-solid separator and is discharged into the persulfate solution tower 16 by the solution pump 18. Then, after replenishing new persulfate solution, it is re-fed into the pump spray counter-attacking bubbling bed 11 through the outlet o of the persulfate solution tower to participate in the removal reaction. The newly replenished persulfate solution is fed into the persulfate solution tower 16 through the new liquid inlet n for replenishing the persulfate solution tower. After multiple cycles, the saturated waste solution containing H2SO4, HNO3, and Hg 2+ is discharged through the waste liquid discharge port j of the liquid-solid separator and sent to the multi-stage comprehensive resource utilization system at the tail.

[0066] IV. The multi-stage comprehensive resource utilization system includes a mercury separation device, an ammonia neutralizing acid device, and a flue gas waste heat evaporation crystallization fertilizer preparation device. In the mercury separation device, Hg 2+ can be separated and recovered by adding divalent sulfur ions to produce mercury sulfide precipitation. In the ammonia neutralizing acid device, H2SO4 and HNO3 can react with ammonia to produce ammonium sulfate and ammonium nitrate. In the flue gas waste heat evaporation crystallization fertilizer preparation device, agricultural fertilizers are prepared after evaporation crystallization using the waste heat of the coal-fired boiler flue gas. Therefore, the entire removal process not only has no secondary pollution but also can obtain important resources such as mercury and agricultural fertilizers, showing good development and application prospects.

[0067] The following are examples of the simultaneous removal of three pollutants, SO2, NO x and Hg 0 by this device under different conditions:

[0068] Example 1:

[0069] The H2O concentration at the water vapor inlet of the gas-solid mixer is 3%, the microwave radiation power density in the microwave activation zone (A1) of the microwave spray floating multi-zone modification bed is 1000 W / m 3 , the microwave radiation power density in the H2S modification zone (A2) is 200 W / m 3 , and the microwave radiation power density in the ammonium chloride modification zone (A3) is 200 W / m 3, the H2S concentration is 20 ppm, the concentration of ammonium chloride solution is 0.01 mol / L, the dosing concentration of ammonium persulfate in the pump-sprayed bursting bubble bed is 0.05 mol / L, the solution pH is 2.1, the reaction temperature is 65 °C, the dosing amount of modified wheat straw biochar is 100 mg / L, and the particle size of the modified biochar is 0.03 μm to 0.1 μm. The SO2 and NO in the flue gas x and Hg 0 concentrations are 1800 ppm, 300 ppm and 50 μg / m 3 .

[0070] The preliminary results of numerical simulation and laboratory-scale experiments are as follows: The simultaneous removal efficiencies of SO2, NO x and Hg 0 in the flue gas can reach 88.9%, 48.7% and 59.2% respectively.

[0071] Example 2:

[0072] The H2O concentration at the water vapor inlet of the gas-solid mixer is 3%, the microwave radiation power density in the microwave activation zone (A1) of the microwave spray floating multi-zone modification bed is 1500 W / m 3 , the microwave radiation power density in the H2S modification zone (A2) is 250 W / m 3 , the microwave radiation power density in the ammonium chloride modification zone (A3) is 250 W / m 3 , the H2S concentration is 20 ppm, the concentration of ammonium chloride solution is 0.01 mol / L, the dosing concentration of ammonium persulfate in the pump-sprayed bursting bubble bed is 0.05 mol / L, the solution pH is 2.1, the reaction temperature is 65 °C, the dosing amount of modified wheat straw biochar is 100 mg / L, and the particle size of the modified biochar is 0.03 μm to 0.1 μm. The SO2 and NO in the flue gas x and Hg 0 concentrations are 1800 ppm, 300 ppm and 50 μg / m 3 .

[0073] The preliminary results of numerical simulation and laboratory-scale experiments are as follows: The simultaneous removal efficiencies of SO2, NO x and Hg 0 in the flue gas can reach 98.7%, 55.9% and 69.1% respectively.

[0074] Example 3:

[0075] The H2O concentration at the water vapor inlet of the gas-solid mixer is 3%, the microwave radiation power density in the microwave activation zone (A1) of the microwave spray floating multi-zone modification bed is 2000 W / m 3 , the microwave radiation power density in the H2S modification zone (A2) is 300 W / m 3, the microwave radiation power density in the ammonium chloride modification zone (A3) is 250 W / m 3 , the H2S concentration is 20 ppm, the concentration of the ammonium chloride solution is 0.01 mol / L, the dosing concentration of ammonium persulfate in the pump-sprayed bursting bubble bed is 0.05 mol / L, the solution pH is 2.1, the reaction temperature is 65 °C, the dosing amount of modified wheat straw biochar is 100 mg / L, and the particle size of the modified biochar is 0.03 μm to 0.1 μm. The SO2, NO x in the flue gas and Hg 0 concentrations are 1800 ppm, 300 ppm, and 50 μg / m 3 .

[0076] The preliminary results of numerical simulation and laboratory-scale experiments are as follows: The simultaneous removal efficiencies of SO2, NO x in the flue gas and Hg 0 can reach 100%, 66.1%, and 75.9% respectively.

[0077] Example 4:

[0078] The H2O concentration at the water vapor inlet of the gas-solid mixer is 3%, and the microwave radiation power density in the microwave activation zone (A1) of the microwave spray floating multi-zone modification bed is 2000 W / m 3 , the microwave radiation power density in the H2S modification zone (A2) is 300 W / m 3 , the microwave radiation power density in the ammonium chloride modification zone (A3) is 250 W / m 3 , the H2S concentration is 80 ppm, the concentration of the ammonium chloride solution is 0.02 mol / L, the dosing concentration of ammonium persulfate in the pump-sprayed bursting bubble bed is 0.05 mol / L, the solution pH is 2.1, the reaction temperature is 65 °C, the dosing amount of modified wheat straw biochar is 100 mg / L, and the particle size of the modified biochar is 0.03 μm to 0.1 μm. The SO2, NO x in the flue gas and Hg 0 concentrations are 1800 ppm, 300 ppm, and 50 μg / m 3 .

[0079] The preliminary results of numerical simulation and laboratory-scale experiments are as follows: The simultaneous removal efficiencies of SO2, NO x in the flue gas and Hg 0 can reach 100%, 77.2%, and 85.4% respectively.

[0080] Example 5:

[0081] The H2O concentration at the water vapor inlet of the gas-solid mixer is 3%, and the microwave radiation power density in the microwave activation zone (A1) of the microwave spray floating multi-zone modification bed is 2000 W / m 3, the microwave radiation power density in the H2S modification zone (A2) is 300 W / m 3 , the microwave radiation power density in the ammonium chloride modification zone (A3) is 250 W / m 3 , the H2S concentration is 80 ppm, the concentration of the ammonium chloride solution is 0.02 mol / L, the dosing concentration of ammonium persulfate in the pump spray bubble-breaking bed is 0.1 mol / L, the solution pH is 2.1, the reaction temperature is 65 °C, the dosing amount of modified wheat straw biochar is 100 mg / L, and the particle size of the modified biochar is 0.03 μm to 0.1 μm. The SO2, NO x in the flue gas and Hg 0 concentrations are 1800 ppm, 300 ppm and 50 μg / m 3 .

[0082] The preliminary results of numerical simulation and laboratory-scale experiments are as follows: The simultaneous removal efficiencies of SO2, NO x in the flue gas and Hg 0 can reach 100%, 85.2% and 92.5% respectively.

[0083] Example 6:

[0084] The H2O concentration at the water vapor inlet of the gas-solid mixer is 3%, and the microwave radiation power density in the microwave activation zone (A1) of the microwave spray-fluidized multi-zone modification bed is 2000 W / m 3 , the microwave radiation power density in the H2S modification zone (A2) is 300 W / m 3 , the microwave radiation power density in the ammonium chloride modification zone (A3) is 250 W / m 3 , the H2S concentration is 80 ppm, the concentration of the ammonium chloride solution is 0.02 mol / L, the dosing concentration of ammonium persulfate in the pump spray bubble-breaking bed is 0.2 mol / L, the solution pH is 2.1, the reaction temperature is 65 °C, the dosing amount of modified wheat straw biochar is 200 mg / L, and the particle size of the modified biochar is 0.03 μm to 0.1 μm. The SO2, NO x in the flue gas and Hg 0 concentrations are 1800 ppm, 300 ppm and 50 μg / m 3 .

[0085] The preliminary results of numerical simulation and laboratory-scale experiments are as follows: The simultaneous removal efficiencies of SO2, NO x in the flue gas and Hg 0 can reach 100%, 93.3% and 98.7% respectively.

[0086] Example 7:

[0087] The H2O concentration at the water vapor inlet of the gas-solid mixer is 3%, and the microwave radiation power density in the microwave activation zone (A1) of the microwave spray floating multi-zone modification bed is 2000 W / m 3 , and the microwave radiation power density in the H2S modification zone (A2) is 300 W / m 3 , and the microwave radiation power density in the ammonium chloride modification zone (A3) is 250 W / m 3 , the H2S concentration is 80 ppm, the concentration of the ammonium chloride solution is 0.02 mol / L, the dosing concentration of ammonium persulfate in the pump spray impact bubble bed is 0.3 mol / L, the solution pH is 2.1, the reaction temperature is 65 °C, the dosing amount of the modified wheat straw biochar is 300 mg / L, and the particle size of the modified biochar is 0.03 μm to 0.1 μm. The SO2, NO x and Hg 0 concentrations in the flue gas are 1800 ppm, 300 ppm and 50 μg / m 3 .

[0088] The preliminary results of numerical simulation and laboratory-scale tests are as follows: The simultaneous removal efficiencies of SO2, NO x and Hg 0 in the flue gas can reach 100%, 98.9% and 99.8% respectively.

[0089] Example 8:

[0090] The H2O concentration at the water vapor inlet of the gas-solid mixer is 3%, and the microwave radiation power density in the microwave activation zone (A1) of the microwave spray floating multi-zone modification bed is 2000 W / m 3 , and the microwave radiation power density in the H2S modification zone (A2) is 300 W / m 3 , and the microwave radiation power density in the ammonium chloride modification zone (A3) is 250 W / m 3 , the H2S concentration is 80 ppm, the concentration of the ammonium chloride solution is 0.02 mol / L, the dosing concentration of ammonium persulfate in the pump spray impact bubble bed is 0.4 mol / L, the solution pH is 2.1, the reaction temperature is 70 °C, the dosing amount of the modified wheat straw biochar is 300 mg / L, and the particle size of the modified biochar is 0.03 μm to 0.1 μm. The SO2, NO x and Hg 0 concentrations in the flue gas are 1800 ppm, 300 ppm and 50 μg / m 3 .

[0091] The preliminary results of numerical simulation and laboratory-scale tests are as follows: The simultaneous removal efficiencies of SO2, NO x and Hg 0 in the flue gas can reach 100%, 100% and 100% respectively.

[0092] The method for removing SO2, NO x and Hg 0 in the present invention can reach the maximum simultaneous removal efficiency of 100%, 100% and 100% respectively, with extremely high simultaneous removal efficiency of multiple pollutants. It can realize the simultaneous removal of single or multiple flue gas pollutants, and no waste water or liquid is generated, which can well meet the current strict ultra-low emission requirements and has extremely significant technical competitive advantages.

[0093] The described embodiments are the preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Without departing from the essence of the present invention, any obvious improvements, substitutions or modifications that those skilled in the art can make all fall within the protection scope of the present invention.

Claims

1. A flue gas purification system based on modified biochar-activated persulfate, characterized in that, The system includes a microwave spray floating multi-zone modification bed (3) and a pump spray counter-attacking bubble-breaking bed (11); Inside the microwave spray floating multi-zone modification bed (3), from bottom to top, it is divided into a microwave activation zone (A1), an H2S modification zone (A2), and an ammonium chloride modification zone (A3); in the microwave activation zone (A1), there are multiple microwave activation zone partition plates (9), and the microwave activation zone partition plates (9) are longitudinally arranged and perpendicular to the bottom of the microwave spray floating multi-zone modification bed (3); On the inner side wall surface of the microwave spray floating multi-zone modification bed (3) and the microwave activation zone partition plates (9), there are multiple microwave emitters (4); the H2S modification zone (A2) is provided with an H2S gas distribution device (7), and the ammonium chloride modification zone (A3) is provided with an ammonium chloride solution atomization device (8); the H2S gas distribution device (7) and the ammonium chloride solution atomization device (8) are respectively connected to an H2S storage tower (5) and an ammonium chloride storage tower (6); at the bottom of the microwave spray floating multi-zone modification bed (3), there is an air-solid nozzle array (2) for spraying biochar; the bottom of the microwave spray floating multi-zone modification bed (3) is connected to an air-solid mixer (1) through a microwave spray floating multi-zone modification bed biochar inlet (d), and the microwave spray floating multi-zone modification bed (3) is connected to a pump spray counter-attacking bubble-breaking bed modified biochar inlet (g) at the left bottom of the pump spray counter-attacking bubble-breaking bed (11) through a top microwave spray floating multi-zone modification bed outlet (e); At the bottom of the pump spray counter-attacking bubble-breaking bed (11), there is a pump spray counter-attacking bubble-breaking bed flue gas inlet (q), at the top there is a pump spray counter-attacking bubble-breaking bed flue gas outlet (h), on the side there are a reaction solution discharge port (i) and a pump spray counter-attacking bubble-breaking bed solution inlet (p); at the top inside the pump spray counter-attacking bubble-breaking bed (11), there is a gas-liquid separation device (13), at the bottom there is a bubbling device (14), and on the side wall there is a pump spray counter-attacking device (12); On the side of the pump spray counter-attacking bubble-breaking bed (11), there is a circulating system constructed by a liquid-solid separation device (15) and a persulfate solution tower (16); the liquid-solid separation device (15) and the persulfate solution tower (16) are respectively connected to the reaction solution discharge port (i) and the pump spray counter-attacking bubble-breaking bed solution inlet (p) through pipelines; on the pipeline between the liquid-solid separation device (15) and the reaction solution discharge port (i), there is a solution pump one (17), on the pipeline between the liquid-solid separation device (15) and the persulfate solution tower (16), there is a solution pump two (18), and on the pipeline between the persulfate solution tower (16) and the pump spray counter-attacking bubble-breaking bed solution inlet (p), there is a solution pump three (19); The microwave spray floating multi-zone modification bed outlet (e) is connected to a booster device (10), the booster device outlet (f) is connected to a connecting pipeline, and on the connecting pipeline, there is a fan (20) for transporting modified biochar.

2. The flue gas purification system based on modified biochar-activated persulfate according to claim 1, characterized in that, The microwave emitters (4) are arranged in a staggered pattern, and the horizontal spacing and vertical spacing L0 between two adjacent microwave emitters (4) are equal, and both the horizontal spacing and vertical spacing L0 are between 5 cm and 50 cm; the nozzles in the air-solid nozzle array are arranged in a staggered pattern, and the vertical spacing and horizontal spacing M0 are equal.

3. The flue gas purification system based on modified biochar-activated persulfate according to claim 1, wherein The height H1 of the microwave activation zone (A1) is between 80 cm and 500 cm, the height H2 of the H2S modification zone (A2) is between 30 cm and 150 cm, and the height H3 of the ammonium chloride modification zone (A3) is between 30 cm and 200 cm; the microwave activation zone (A1) is separated into multiple sub-activation zones by multiple microwave activation zone partitions (9), and the spacing L1 between each sub-activation zone is the same, and the distance of L1 is maintained between 10 cm and 60 cm.

4. A flue gas purification system based on modified biochar-activated persulfate according to claim 1, characterized in that, The pump jet impact devices (12) are arranged in a staggered pattern, and the lateral spacing and longitudinal spacing are equal; the pump jet impact devices (12) arranged opposite each other on the two side walls of the pump jet impact bubble column (11) are on the same horizontal line; the longitudinal spacing and lateral spacing K1 between every two pump jet impact devices (12) are both maintained between 50 cm and 120 cm, and the horizontal distance L2 between the nozzles of the pump jet impact devices (12) arranged oppositely is maintained between 80 cm and 500 cm.

5. A flue gas purification system based on modified biochar-activated persulfate according to claim 1, characterized in that, The microwave radiation power density inside the microwave activation zone (A1) is maintained between 1000 W / m 3 and 5000 W / m 3 . The microwave activation power inside the H2S modification zone (A2) is maintained between 200 W / m 3 and 1000 W / m 3 . The microwave activation power inside the ammonium chloride modification zone (A3) is maintained between 200 W / m 3 and 1000 W / m 3 .

6. The flue gas purification system based on modified biochar-activated persulfate according to claim 1, characterized in that, The H2O concentration at the water vapor inlet of the gas-solid mixer is maintained between 2% and 15%, the H2S concentration ejected by the H2S gas distribution device (7) is maintained between 20 ppm and 200 ppm, and the concentration of the ammonium chloride solution ejected by the ammonium chloride solution atomization device (8) is maintained between 0.01 mol / L and 1.0 mol / L.

7. A flue gas purification system based on modified biochar-activated persulfate according to claim 1, characterized in that, The concentration range of persulfate inside the pump-jet impact-breaking bubble column (11) is 0.02 mol / L to 3.0 mol / L, the solution pH is 0.1 to 7.5, the reaction temperature is 30 °C to 80 °C, and the dosage of modified biochar is 20 mg / L to 800 mg / L; the initial concentration ranges of flue gas pollutants SO2, NO x and Hg 0 are 100 to 2000 ppm, 300 to 1500 ppm and 50 μg / m 3 to 500 μg / m 3 respectively; the optimized particle size of the modified biochar is 0.001 μm to 0.5 μm.

8. A method for a flue gas purification system based on modified biochar-activated persulfate according to any one of claims 1-7, characterized in that: The operation of the biochar modification and pollutant removal system is as follows: I. Air enters the gas-solid mixer (1) from the air inlet (a) of the gas-solid mixer, biochar enters the gas-solid mixer (1) from the biochar inlet (b) of the gas-solid mixer, and water vapor enters the gas-solid mixer (1) from the water vapor inlet (c) of the gas-solid mixer; the three substances are mixed in the gas-solid mixer (1) and then enter the microwave spray floating multi-zone modification bed (3) through the biochar inlet (d) of the microwave spray floating multi-zone modification bed; the biochar realizes rapid pore expansion and increases the specific surface area through the synergistic activation of microwave and water vapor in the microwave activation zone (A1); the biochar that has been fully circulated and activated in the microwave activation zone (A1) continues to enter the H2S modification zone (A2) to be synergistically modified by microwave and H2S to load the active sulfur (S) component; the biochar that has been modified in the H2S modification zone (A2) continues to enter the ammonium chloride modification zone (A3), and is synergistically modified by microwave and ammonium chloride to load the active nitrogen (N) and active chlorine (Cl) components; II. The biochar modified in the microwave spray floating multi-zone modification bed (3) enters the pressurization device (10) through the outlet (e) of the microwave spray floating multi-zone modification bed for pressurization, and then is transported through a pipeline from the outlet (f) of the pressurization device to the pump jet impact bubble column (11) for radical activation and pollutant removal reaction; the modified biochar enters the persulfate solution reaction zone in the pump jet impact bubble column (11) through the modified biochar inlet (g) of the pump jet impact bubble column for radical activation and pollutant oxidative removal reaction; during the radical activation and pollutant removal reaction, the pump jet impact devices (12) start the counter-jet mode to achieve efficient mixing of gas, liquid and solid; III. Flue gas from a coal-fired boiler enters the pump-jet counter-attacking bubbling bed (11) from the pump-jet counter-attacking bubbling bed flue gas inlet (q), and after bubbling through the bubbling device (14), enters the reaction zone to be mixed with the persulfate solution; in the persulfate solution in the reaction zone, free radicals / active components induced by the activation of modified biochar on persulfate react with SO2, NO x and Hg 0 to undergo oxidation reactions, oxidizing SO2, NO x and Hg 0 into H2SO4, HNO3 and Hg 2+ respectively. After the separated clean flue gas removes the solution through the gas-liquid separation device (13), it is sent from the pump-jet counter-attacking bubbling bed flue gas outlet (h) to the chimney at the tail and discharged into the atmosphere; the reaction waste solution is discharged by the solution pump one (17) into the liquid-solid separation device (15) to separate the solution and biochar; the separated waste biochar can be sent from the waste biochar discharge port (k) of the liquid-solid separation device back to the microwave spray floating multi-zone modification bed (3) through the biochar inlet (b) of the gas-solid mixer for re-activation and modification; the separated solution passes through the solution circulation outlet (l) of the liquid-solid separation device, is discharged by the solution pump two (18) into the persulfate solution tower (16), and then after supplementing with fresh persulfate solution, it is re-sent into the pump-jet counter-attacking bubbling bed (11) through the persulfate solution tower outlet (o) to participate in the removal reaction; the newly supplemented persulfate solution is sent into the persulfate solution tower (16) through the fresh liquid inlet (n) of the persulfate solution tower. After multiple cycles, the saturated waste solution containing H2SO4, HNO3 and Hg 2+ is discharged through the waste liquid discharge port (j) of the liquid-solid separation device and sent to the multi-stage comprehensive resource utilization system at the tail; IV. The multi-stage comprehensive resource utilization system includes a mercury separation device, an ammonia neutralization acid device, and a flue gas waste heat evaporation crystallization device for preparing fertilizers. In the mercury separation device, Hg 2+ can be separated and recovered by adding divalent sulfide ions to react to produce mercury sulfide precipitation. In the ammonia neutralization acid device, H2SO4 and HNO3 can react with ammonia to produce ammonium sulfate and ammonium nitrate. In the flue gas waste heat evaporation crystallization device for preparing fertilizers, agricultural fertilizers are prepared after evaporation crystallization using the waste heat of the coal-fired boiler flue gas.

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