A method and system for simultaneously desulfurizing, denitrifying and mercury removing based on a modified magnetic catalyst in a photochemical spouted tower

Abstract

The present invention provides a method and system for simultaneously desulfurizing, denitrifying and removing mercury from flue gas based on a photochemical spouted tower modified magnetic catalyst, belonging to the technical field of air pollutant control; in the present invention, a green free radical modified magnetic catalyst is utilized, and through the modified magnetic catalyst, SO2 and NO x and Hg 0 in the flue gas are respectively oxidized into relatively more soluble SO3, NO2 / N2O4 / N2O5 and Hg 2+ , and can be removed by washing through the wet desulfurization system behind the magnetic separator. After deactivation, the magnetic catalyst of the present invention can be activated and regenerated by green free radicals, overcoming the defect of easy deactivation existing in the catalytic removal method. The circulation effect of the external gas circulation bypass and the impact effect of the nozzle greatly improve the modification rate and mass transfer rate of the magnetic catalyst, and at the same time have many advantages such as low initial investment and operation cost, etc. It is a new flue gas purification method and system with broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of combustion flue gas pollutant control, and particularly relates to a method and system for simultaneously desulfurizing, denitrifying and mercury-removing based on a photocatalytic spouted bed modified magnetic catalyst. Background Art

[0002] SO2, NO generated during the combustion process x and atmospheric pollutants such as mercury can cause acid rain, photochemical smog, carcinogenesis, teratogenesis and other hazards, seriously endangering the ecological environment and human health. Therefore, researching and developing economic, environmentally friendly and efficient flue gas desulfurization, denitrification and mercury-removing technologies is one of the important tasks faced by governments and environmental protection technicians in various countries.

[0003] In the past two decades, researchers at home and abroad have developed a large number of flue gas desulfurization, denitrification and mercury-removing technologies. However, due to the limitations of the human understanding process and the gradual progress of science and technology, various existing flue gas desulfurization, denitrification and mercury-removing technologies were only targeted at a single pollutant as the removal target at the beginning of their research and development, and generally could not achieve the simultaneous removal of multiple flue gas pollutants. For example, the currently adopted mainstream flue gas desulfurization and denitrification technologies are mainly the limestone-gypsum wet flue gas desulfurization technology and the ammonia selective catalytic reduction denitrification method. Although these two methods can achieve flue gas desulfurization and denitrification step by step, neither of them can achieve simultaneous removal in a single reactor. The combined and superimposed use of the two processes can achieve simultaneous flue gas desulfurization and denitrification, but at the same time, it also leads to many deficiencies such as a huge and complex whole system, large floor area, high initial investment and operating costs.

[0004] In addition, with the continuous improvement of human environmental protection requirements, the call for mercury emission control in combustion flue gas is getting higher and higher. However, there is currently no economically effective combustion flue gas mercury-removing technology that has been widely commercialized. If a separate flue gas mercury-removing system is added to the tail of the existing desulfurization and denitrification systems, it will inevitably cause a further sharp increase in the initial investment and operating costs of the whole system. At present, there are more than 500,000 small and medium-sized boilers, industrial kilns and waste incinerators in industrial and civil industries in China. When enterprise users of these small and medium-sized combustion devices install desulfurization, denitrification and mercury-removing devices for SO2, NO x and mercury three pollutants at the same time, they will face huge economic pressure, which is not conducive to the large-scale popularization of relevant technologies and policies.

[0005] To sum up, if SO2, NO can be removed in a single reactor xSimultaneous removal of sulfur dioxide, nitrogen oxides and mercury is expected to significantly reduce the complexity and floor area of the system, thereby reducing the initial investment and operating costs of the system and showing good development prospects. Currently, researchers at home and abroad have developed a variety of flue gas simultaneous desulfurization, denitrification and mercury removal technologies, mainly including catalytic method, plasma removal method, adsorption method, complexation absorption method, traditional oxidation method and free radical advanced oxidation method, etc. The plasma removal method has deficiencies such as poor reliability of technical devices and high energy consumption. The adsorption method has disadvantages such as low removal efficiency and the need for intermittent operation of the device. The complexation absorption method has deficiencies such as large regeneration loss of the complexing agent and high energy consumption. The traditional oxidation method has problems such as low oxidation ability, large consumption of oxidants, secondary pollution or high costs (different oxidants often have one or more disadvantages). The currently widely concerned free radical advanced oxidation technology has obtained great development, but there are still technical and economic problems such as large investment, high operating costs and poor technical maturity, and there is still a long way to industrial application, which requires more research efforts from scientific and technological personnel in this field.

[0006] Among various simultaneous removal technologies, the catalytic removal method has comprehensive advantages such as small initial investment, simple process flow, catalyst activation and regeneration, and easy simultaneous removal of multiple pollutants, and is a flue gas simultaneous removal technology with good development prospects. However, the development of traditional catalytic simultaneous desulfurization, denitrification and mercury removal technology has been very slow, and there are mainly three reasons: (1) First, common simultaneous desulfurization, denitrification and mercury removal catalysts will be deactivated or poisoned after removing pollutants, and need to be activated and regenerated in time. However, the currently commonly used activation and regeneration methods of simultaneous desulfurization, denitrification and mercury removal catalysts often have problems such as low activation and regeneration efficiency and inability to activate and regenerate in real time online; (2) Second, the currently commonly used activation and regeneration methods of simultaneous desulfurization, denitrification and mercury removal catalysts have deficiencies such as huge energy consumption and high cost during the activation and regeneration process, which do not conform to the current national energy-saving and low-carbon operation strategy; (3) Third, the currently common catalytic simultaneous desulfurization, denitrification and mercury removal technologies mainly operate in fixed beds and fluidized beds, but the mass transfer rates of the two traditional reactors are very small. A large number of studies and industrial practices have confirmed that the main rate-limiting step in the gas-solid reaction process is the mass transfer process. Therefore, using traditional reactors for catalytic simultaneous desulfurization, denitrification and mercury removal easily leads to disadvantages such as large reactor volume and high operating energy consumption. The above three key problems are the main bottlenecks or obstacles hindering the large-scale industrial application of catalytic simultaneous desulfurization, denitrification and mercury removal technology. Summary of the Invention

[0007] Aiming at the problems of easy deactivation, high energy consumption and low mass transfer rate existing in the existing catalytic removal method, the present invention provides a method and system for simultaneous desulfurization, denitrification and mercury removal based on a photochemical spouted bed modified magnetic catalyst. By using a green free radical modified magnetic catalyst, SO2 and NO in the flue gas are removed through the modified magnetic catalyst. x and Hg0 are respectively oxidized into relatively more soluble SO3, NO2 / N2O4 / N2O5 and Hg 2+ , and can be removed by washing through the wet flue gas desulfurization system behind the magnetic separator. After deactivation, the magnetic catalyst of the present invention can be regenerated by green free radical activation, overcoming the defect of easy deactivation existing in the catalytic removal method. The circulation effect of the air flow external circulation bypass and the impact effect of the nozzle greatly improve the modification rate and mass transfer rate of the magnetic catalyst, and at the same time have many advantages such as low initial investment and operation cost, and it is a new type of flue gas purification method and system with broad application prospects.

[0008] The present invention first provides a system for simultaneously desulfurizing, denitrifying and removing mercury by modifying a magnetic catalyst based on a photochemical spouted bed. The system includes a photochemical spouted bed for catalyst modification and a counter-jet tower for catalytic removal;

[0009] The photochemical spouted bed is internally provided with a plurality of heat pipes and ultraviolet lamps. On the inner wall of the bottom surface, a number of magnetic catalyst injection devices are evenly distributed. At the top, there are provided a magnetic catalyst inlet connected to the magnetic catalyst feeding device, a modified reagent and its carrying gas inlet, and a modified magnetic catalyst outlet connected to the gas-solid impinging mixer; an air flow external circulation bypass is provided outside the photochemical spouted bed. One end of the air flow external circulation bypass is communicated with the top of the photochemical spouted bed, and the other end is communicated with the magnetic catalyst injection device, and a first fan is installed on the air flow external circulation bypass; a first valve is provided at the bottom of the photochemical spouted bed;

[0010] The top of the counter-jet tower is provided with a first outlet communicated with the inlet pipeline of the magnetic separation device. On both side inner walls, a number of symmetrically distributed gas-solid nozzle arrays are respectively provided. The two side gas-solid nozzle arrays are respectively communicated with the gas-solid impinging mixer through pipelines, and a second fan and a third fan are respectively provided on the pipelines; the gas-solid impinging mixer is communicated with the burner through a gas supply pipeline, and a fourth fan and a flue gas temperature regulator are installed on the gas supply pipeline; the magnetic separation device is provided with a magnetic catalyst outlet and a treated flue gas outlet; a second valve is provided at the bottom of the counter-jet tower.

[0011] Furthermore, the ultraviolet lamps in the photochemical spouted bed adopt an equal spacing and staggered arrangement method. The center lines of the ultraviolet lamps are arranged parallel to the central axis of the photochemical spouted bed. The distance between adjacent two ultraviolet lamps is not less than 15 cm, and the included angle formed by adjacent two ultraviolet lamps and the center of the photochemical spouted bed is not less than 20 degrees. The length of the ultraviolet lamp tubes is 20 - 300 cm, and the ultraviolet radiation intensity at the center between every two ultraviolet lamp tubes is not less than 20 μW / cm 2 ; the heat pipes adopt a staggered arrangement and are arranged at intervals with the ultraviolet lamps.

[0012] Further, the cross-section inside the countercurrent tower is circular or rectangular, and a gas-solid nozzle array is provided on one or more cross-sections. The distance between the gas-solid nozzle arrays on adjacent cross-sections is 15 - 100 cm, and the distance between the opposite gas-solid nozzle arrays on both sides of the same cross-section is 50 - 300 cm.

[0013] The present invention also provides a removal method for a system that simultaneously desulfurizes, denitrifies, and removes mercury based on a photocatalytic spouted bed modified magnetic catalyst, including:

[0014] (1) Material selection:

[0015] Select a modifying reagent and a magnetic catalyst. The modifying reagent is either H2O2 alone or a mixture containing H2O2. Calculate the input amounts of the magnetic catalyst and the modifying reagent according to the volume of the photocatalytic spouted bed.

[0016] (2) Modification of the magnetic catalyst:

[0017] Introduce the modifying reagent and the magnetic catalyst into the photocatalytic spouted bed. Use an ultraviolet lamp tube to induce H2O2 in the modifying reagent to generate hydroxyl radicals (·OH). Use the generated hydroxyl radicals (·OH) to attack the surface of the magnetic catalyst, so that active sites are generated on the surface of the magnetic catalyst, and the magnetic catalyst is repeatedly modified multiple times through an external gas circulation bypass. The specific modification process is represented by the following chemical equations (1) - (4):

[0018]

[0019] n·OH + Catalyzer → Catalyzer-active sites (2)

[0020] (3) Catalytic oxidation:

[0021] Introduce the modified magnetic catalyst and the flue gas generated by the burner into the countercurrent tower, and use the active sites on the magnetic catalyst to thermally catalytically oxidize SO2, NO, and / or Hg in the flue gas 0 , so that SO2, NO, and / or Hg 0 are respectively oxidized to SO3, NO2 / N2O4 / N2O5, and / or Hg 2+ , and the specific process can be represented by the following chemical reactions (3) - (5):

[0022] Catalyzer-active sites + SO2 → Catalyzer + SO3 (3)

[0023] Catalyzer-active sites + NO → Catalyzer + NO2 / N2O4 / N2O5 (4)

[0024] Catalyzer-active sites + Hg 0 → Catalyzer + Hg 2+ (5)

[0025] (4) Removal:

[0026] Separate the magnetic catalyst that has lost its catalytic active sites in step (3) from the flue gas containing SO3, NO2 / N2O4 / N2O5, and / or Hg 2+ through a magnetic separator, and the oxidized flue gas directly leads to the subsequent wet flue gas desulfurization system for washing and removal.

[0027] Furthermore, in step (1), the magnetic catalyst includes one or more mixtures of CoFe2O4, MnFe2O4, CuFe2O4, CeFe2O4, Fe2O3, Fe3O4, or magnetic beads in magnetite or coal fly ash; the particle size of the magnetic catalyst is 0.001 - 0.5 μm.

[0028] Furthermore, in step (1), the input amount of the magnetic catalyst = volume of the photochemical spouted bed (m 3 ) × (0.2 - 18 kg); the concentration of the modifying reagent is 0.01 - 3.0 mol / L, and the input amount = volume of the countercurrent tower (m 3 ) × (0.02 - 2 kg).

[0029] Furthermore, in step (2), the ultraviolet light radiation intensity of the ultraviolet lamp tubes in the photochemical spouted bed is 5 - 280 μW / cm 2 , the effective wavelength of the ultraviolet light is 110 - 320 nm; the modifying temperature in the photochemical spouted bed is 50 - 120 °C; the circulation rate of the gas flow in the external circulation bypass is 10 - 500 m 3 / h.

[0030] Furthermore, in step (3), the catalytic oxidation temperature in the countercurrent tower is 60 - 220 °C.

[0031] Furthermore, in step (4), the magnetic catalyst separated from the oxidized flue gas is re-introduced into the magnetic catalyst feeding device through a pipeline, and active sites are regenerated again by repeating step (2).

[0032] The basic principle of the method and system in the present invention:

[0033] (1) Modification: Ultraviolet radiation is used to decompose H2O2 to generate hydroxyl radicals (·OH) with extremely strong oxidizing properties. The generated hydroxyl radicals (·OH) have extremely strong oxidizing properties and can attack the surface of the magnetic catalyst to generate highly active sites with strong oxidizing properties (active sites), thereby obtaining the modified magnetic catalyst. The specific process can be represented by the following chemical reactions (1)-(2):

[0034]

[0035] n·OH + Catalyzer → Catalyzer-active sites (2)

[0036] (2) Removal: The activated and modified magnetic catalyst uses the highly active sites (activesites) with strong oxidizing properties to catalytically oxidize SO2, NO, and Hg in the flue gas 0 , so that SO2, NO, and Hg 0 and other pollutants are respectively oxidized into SO3, NO2 / N2O4 / N2O5, and Hg 2+ and other pollutants with higher solubility. The specific process can be represented by the following chemical reactions (3)-(5):

[0037] Catalyzer-active sites + SO2 → Catalyzer + SO3 (3)

[0038] Catalyzer-active sites + NO → Catalyzer + NO2 / N2O4 / N2O5 (4)

[0039] Catalyzer-active sites + Hg 0 → Catalyzer + Hg 2+ (5)

[0040] The magnetic catalyst that has lost catalytic active sites (active sites) after the reaction can be activated and modified for regeneration through chemical reactions (1)-(2), enabling it to regain the ability of catalytic oxidation and removal, thereby achieving recycling. The SO3, NO2 / N2O4 / N2O5, and Hg 2+ and other pollutants generated by catalytic oxidation have high solubility in water and can be removed by washing through the existing wet desulfurization system at the tail, thereby achieving simultaneous desulfurization, denitrification, and mercury removal economically and efficiently.

[0041] Compared with the existing technology, the beneficial effects of the present invention are as follows:

[0042] In the present invention, the system for simultaneous desulfurization, denitrification, and mercury removal based on a magneto-catalyst modified by a photochemical spouted bed adjusts the distance and radiation intensity of the ultraviolet lamps in the photochemical spouted bed. On the premise of improving the radiation coverage of ultraviolet light and ensuring sufficient fluidization and backflow mixing space for the magneto-catalyst particles, the number of ultraviolet lamps used and the investment cost of the light source are reduced. While controlling the initial investment and operating energy consumption, the activation and modification effect is ensured.

[0043] The present invention can achieve good separation and recovery of the magneto-catalyst, and can be activated and regenerated in real time online. It has a low catalyst consumption cost and greatly reduces the amount of solid waste post-treatment of deactivated reagents. The present invention uses a dry process free radical advanced oxidation technology to oxidize pollutants, which has the advantages of a green and environmentally friendly process and no secondary pollution, and has good technical and economic advantages.

[0044] The method described in the present invention removes SO2, NO x and mercury, and the maximum simultaneous removal efficiencies can reach 100%, 98.5%, and 99.2% respectively. It has extremely high simultaneous removal efficiency, can achieve 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, has extremely significant technical competitive advantages, and has good industrial application prospects.

[0045] The side nozzles in the present invention are symmetrically distributed left and right. The airflows ejected from the nozzles on both sides form a head-on collision, which can greatly improve the gas-solid mass transfer rate. The circulation effect of the external air circulation bypass and the head-on collision effect of the nozzles make the device have extremely strong modification rate and gas-solid mass transfer rate, which is one order of magnitude higher than that of traditional fixed beds and fluidized beds. The phenomenon of caking existing in traditional fixed bed modification and bubbling bed modification can be avoided, and the conditions are mild and controllable, with a wide temperature window.

[0046] The pollutant removal device described in the present invention can be directly externally connected to the existing desulfurization, denitrification, mercury removal, and arsenic removal devices, which can greatly improve the removal efficiency of the original desulfurization, denitrification, mercury removal, and arsenic removal devices, is particularly suitable for the transformation of old units, and has extremely strong process adaptability. In addition. The present invention has many comprehensive advantages such as low initial investment and operating cost, and small reactor volume, and is a flue gas purification method and system with broad industrial application prospects. Description of the Drawings

[0047] Figure 1 is a schematic structural diagram of the system for simultaneous desulfurization, denitrification, and mercury removal based on a magneto-catalyst modified by a photochemical spouted bed.

[0048] Figure 2 is the layout and size diagram of the ultraviolet lamps, heat pipes, and gas-solid nozzles in the photochemical spouted bed.

[0049] Figure 3It is the layout and dimension diagram of the nozzles in the gas-solid nozzle array of the countercurrent tower.

[0050] In the figure, 1 - photochemical spouted bed; 2 - countercurrent tower; 3 - heat pipe; 3-1 - cross-section of heat pipe; 4 - ultraviolet lamp tube; 4-1 - cross-section of ultraviolet lamp tube; 5 - magnetic catalyst injection device; 5-1 - cross-section of magnetic catalyst injection device; 6 - magnetic catalyst feeding device; 7 - magnetic catalyst inlet; 8 - modified reagent and its carried gas inlet; 9 - gas-solid impinging mixer; 10 - outlet of modified magnetic catalyst; 11 - circulation bypass; 12 - first fan; 13 - first valve; 14 - second valve; 15 - magnetic separation device; 16 - first outlet; 17 - gas-solid nozzle array; 17-1 - cross-section of gas-solid nozzle; 18 - burner; 19 - second fan; 20 - third fan; 21 - fourth fan; 22 - flue gas temperature regulator; 23 - magnetic catalyst outlet; 24 - treated flue gas outlet. Specific embodiments

[0051] 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.

[0052] Figure 1 It is a schematic structural diagram of a system for simultaneously desulfurizing, denitrifying and removing mercury from a modified magnetic catalyst based on a photochemical spouted bed, including a photochemical spouted bed 1 for catalyst modification and a countercurrent tower 2 for catalytic removal.

[0053] Inside the photochemical spouted bed 1, there are a plurality of heat pipes 3 and ultraviolet lamp tubes 4. The heat pipes 3 are used to heat the operating temperature required for the activation modification of the magnetic catalyst, and the ultraviolet lamp tubes 4 are used to provide ultraviolet light to induce the modified reagent to generate hydroxyl radicals, thereby modifying the magnetic catalyst to generate high-activity sites. A number of magnetic catalyst injection devices 5 are evenly distributed on the inner wall of the bottom surface, and the bottom nozzles can jet upward to provide sufficient suspension force for the magnetic catalyst. At the top of the photochemical spouted bed 1, there are a magnetic catalyst inlet 7 connected to the magnetic catalyst feeding device 6, a modified reagent and its carried gas inlet 8, and an outlet 10 of the modified magnetic catalyst connected to the gas-solid impinging mixer 9. Outside the photochemical spouted bed 1, there is an external gas flow circulation bypass 11 for circulating the magnetic catalyst to achieve multiple repeated modifications. One end of the gas flow circulation bypass 11 is connected to the top of the photochemical spouted bed 1, and the other end is connected to the magnetic catalyst injection device 5. And a first fan 12 is installed on the gas flow circulation bypass 11. A first valve 13 is provided at the bottom of the photochemical spouted bed 1.

[0054] The bottom of the countercurrent tower 3 is provided with a second valve 14, and the top is provided with a first outlet 16 connected to the inlet pipeline of the magnetic separation device 15. A number of gas-solid nozzle arrays 17 are respectively arranged on the inner walls of both sides to provide a lateral impact force. The opposite-side spraying and collision generate an extremely high mass transfer and diffusion rate, thereby strengthening the catalytic removal reaction process. The gas-solid nozzle arrays 17 on both sides are respectively connected to the gas-solid impact mixer 9 through pipelines, and a second fan 19 and a third fan 20 are respectively arranged on the pipelines on both sides; the gas-solid impact mixer 9 is provided with a gas supply pipeline connected to the burner 18, and a fourth fan 21 and a flue gas temperature regulator 22 are installed on the gas supply pipeline, which are responsible for adjusting the flue gas temperature and transporting the flue gas into the countercurrent tower 2. The magnetic separation device 15 is provided with a magnetic catalyst outlet 23 and a treated flue gas outlet 24.

[0055] Figure 2 It is the layout and dimension diagram of the ultraviolet lamp tube 4, the heat pipe 3 and the magnetic catalyst spraying device 5 in the photochemical spouted bed 1. The ultraviolet lamp tube 4 is sheathed with a wear-resistant and corrosion-resistant quartz sleeve to ensure the use safety and service life of the ultraviolet lamp tube 4. The center line of the ultraviolet lamp tube 4 in the photochemical spouted bed 1 is arranged parallel to the central axis of the photochemical spouted bed 1 to improve the radiation coverage rate of ultraviolet light. Since the ultraviolet light radiation intensity is too small to generate a sufficient concentration of hydroxyl radicals, and too high will lead to a large increase in energy consumption, the optimal range is 5 - 280 μW / cm 2; Ultraviolet light with short wavelengths has high radiation energy, which is beneficial to the decomposition of H2O2 to generate hydroxyl radicals. However, its propagation distance is short, resulting in too large a reactor volume. On the other hand, ultraviolet light with long wavelengths has a long propagation distance, which is beneficial to reducing the reactor volume, but its ability to decompose H2O2 is small, resulting in insufficient unit concentration of hydroxyl radicals generated by the radiolytic decomposition of H2O2 and unable to obtain good modification efficiency. Therefore, the optimal wavelength range is 110nm - 320nm. When multiple ultraviolet lamps 4 need to be arranged, the ultraviolet lamps 4 should be arranged in a staggered pattern to ensure good radiation coverage of the magnetic catalyst. In addition, the length of the ultraviolet lamp 4 has an important impact on the modification time, energy consumption, and reactor height of the magnetic catalyst. The shorter the ultraviolet lamp 4, the lower the operating energy consumption and the reactor height also decreases, which is beneficial to reducing investment and operating costs, but the modification time is shorter, which is not conducive to fully implementing activation modification; conversely, the longer the ultraviolet lamp 4, the higher the initial investment and operating energy consumption, but the more sufficient the modification time and the better the activation modification effect. Therefore, the length of the ultraviolet lamp is between 20 and 300 cm. The heat pipes 3 in the photochemical spouted bed 1 are arranged at intervals with the ultraviolet lamps 4, also in a staggered pattern, to ensure good heat transfer effect. To ensure that the magnetic catalyst particles have sufficient fluidized reverse mixing space while reducing the number of ultraviolet lamps used and the investment cost of the light source, the minimum distance S between the ultraviolet lamps should be no less than 15 cm, and the angle V should be no less than 20 degrees. However, the distance between the ultraviolet lamps should not be too large, because too large a distance between the ultraviolet lamps will result in the ultraviolet radiation intensity between the ultraviolet lamps not meeting the requirements. It is necessary to ensure that the ultraviolet radiation intensity at the center between two ultraviolet lamps is not less than 20 μW / cm 2 。

[0056] Figure 3 is the layout and dimension diagram of the nozzles in the gas-solid nozzle array 17 of the countercurrent tower 2. The cross-section inside the countercurrent tower 2 is circular or rectangular, and a gas-solid nozzle array 17 is provided on one or more cross-sections. The distance between the gas-solid nozzle arrays 17 on different cross-sections is 15 - 100 cm, and the distance between the gas-solid nozzle arrays 17 facing each other on both sides of the same cross-section is 50 - 300 cm.

[0057] The removal method of the system for simultaneously desulfurizing, denitrifying, and removing mercury from magnetic catalysts based on a photochemical spouted bed according to the present invention includes:

[0058] (1) Material selection:

[0059] Select a modification reagent and a magnetic catalyst. The modification reagent is either H2O2 alone or a mixture containing H2O2. Calculate the input amounts of the magnetic catalyst and the modification reagent based on the volume of the photochemical spouted bed. The magnetic catalyst includes one or more mixtures of CoFe2O4, MnFe2O4, CuFe2O4, CeFe2O4, Fe2O3, Fe3O4, or magnetic beads in magnetite or coal fly ash. The particle size of the magnetic catalyst is 0.001 - 0.5 μm.

[0060] The input amount of the magnetic catalyst = volume of the photochemical spouted bed (m 3 ) × (0.2 - 18 kg); the concentration of the modification reagent is 0.01 - 3.0 mol / L, and the input amount = volume of the countercurrent tower (m 3 ) × (0.02 - 2 kg).

[0061] (2) Modification of the magnetic catalyst:

[0062] Preset the ultraviolet light radiation intensity, the effective ultraviolet light wavelength of the ultraviolet lamp 4, the modification temperature in the photochemical spouted bed 1, and the operating temperature in the countercurrent mixing tower 2. The ultraviolet light radiation intensity of the ultraviolet lamp in the photochemical spouted bed is 5 - 280 μW / cm 2 , and the effective ultraviolet light wavelength is 110 - 320 nm; the modification temperature in the photochemical spouted bed is 50 - 120 °C; the circulation rate of the gas flow external circulation bypass is 10 - 500 m 3 / h.

[0063] Subsequently, introduce the modification reagent and the magnetic catalyst into the photochemical spouted bed. Use the ultraviolet lamp to induce H2O2 in the modification reagent to generate hydroxyl radicals (·OH). Use the generated hydroxyl radicals (·OH) to attack the surface of the magnetic catalyst, causing active sites to be generated on the surface of the magnetic catalyst. And perform multiple repeated modifications on the magnetic catalyst through the gas flow external circulation bypass. The specific modification process is represented by the following chemical equations (1) - (4):

[0064]

[0065] n·OH + Catalyzer → Catalyzer - active sites (2)

[0066] (3) Catalytic oxidation:

[0067] Set the catalytic oxidation temperature in the countercurrent tower 2 to 60 - 220 °C. Then introduce the modified magnetic catalyst and the flue gas generated by the burner into the countercurrent tower. Use the active sites on the magnetic catalyst to thermally catalytically oxidize SO2, NO, and / or Hg in the flue gas 0, such that SO2, NO, and / or Hg 0 are respectively oxidized to SO3, NO2 / N2O4 / N2O5, and / or Hg 2+ , and the specific process can be represented by the following chemical reactions (3)-(5):

[0068] Catalyzer-active sites + SO2 → Catalyzer + SO3 (3)

[0069] Catalyzer-active sites + NO → Catalyzer + NO2 / N2O4 / N2O5 (4)

[0070] Catalyzer-active sites + Hg 0 → Catalyzer + Hg 2+ (5)

[0071] (4) Removal:

[0072] The magnetic catalyst that has lost its catalytic active sites in step (3) is separated from the flue gas containing SO3, NO2 / N2O4 / N2O5, and / or Hg 2+ by a magnetic separator, and the oxidized flue gas directly leads to the subsequent wet flue gas desulfurization system for washing and removal. The magnetic catalyst separated from the oxidized flue gas is re-introduced into the magnetic catalyst feeding device through a pipeline, and the active sites are regenerated again by repeating step (2).

[0073] The following are examples of the simultaneous removal efficiency experiments of this device for three pollutants, SO2, NO x and Hg 0 under different test conditions:

[0074] Example 1:

[0075] The activation modification temperature of the photochemical spouted bed is 55 °C, the radiation intensity and wavelength of ultraviolet light are 15 μW / cm 2 and 254 nm respectively, the dosing concentration of the modification reagent H2O2 is 0.1 mol / L, the dosing amount of the modification reagent H2O2 is 80 g per cubic meter of the reactor, the magnetic catalyst is nano-Fe3O4, the magnetic catalyst concentration is 0.5 kg per cubic meter of the reactor, and the operating temperature of the punching machine is 50 °C. The concentrations of SO2, NO x and Hg 0 in the flue gas are 1800 ppm, 350 ppm, and 60 μg / m 3 respectively. The test results on the small experimental system are: SO2, NO x and Hg0 The simultaneous removal efficiencies can reach 56.8%, 45.3% and 49.9% respectively.

[0076] Example 2:

[0077] The activation and modification temperature of the photochemical spouted bed is 55 °C, the radiation intensity and wavelength of ultraviolet light are 35 μW / cm 2 and 254 nm respectively, the dosing concentration of the modification reagent H2O2 is 0.15 mol / L, the dosing amount of the modification reagent H2O2 is 120 g per cubic meter of reactor, the magnetic catalyst is nano-Fe3O4, the magnetic catalyst concentration is 0.5 kg per cubic meter of reactor, and the operating temperature of the countercurrent bed is 50 °C. The concentrations of SO2, NO x and Hg 0 in the flue gas are 1800 ppm, 350 ppm and 60 μg / m 3 respectively. The test results on the small-scale experimental system are as follows: The simultaneous removal efficiencies of SO2, NO x and Hg 0 in the flue gas can reach 69.8%, 54.3% and 59.8% respectively.

[0078] Example 3:

[0079] The activation and modification temperature of the photochemical spouted bed is 55 °C, the radiation intensity and wavelength of ultraviolet light are 55 μW / cm 2 and 254 nm respectively, the dosing concentration of the modification reagent H2O2 is 0.25 mol / L, the dosing amount of the modification reagent H2O2 is 120 g per cubic meter of reactor, the magnetic catalyst is nano-Fe3O4, the magnetic catalyst concentration is 0.5 kg per cubic meter of reactor, and the operating temperature of the countercurrent bed is 50 °C. The concentrations of SO2, NO x and Hg 0 in the flue gas are 1800 ppm, 350 ppm and 60 μg / m 3 respectively. The test results on the small-scale experimental system are as follows: The simultaneous removal efficiencies of SO2, NO x and Hg 0 in the flue gas can reach 78.1%, 65.3% and 76.6% respectively.

[0080] Example 4:

[0081] The activation and modification temperature of the photochemical spouted bed is 55 °C, the radiation intensity and wavelength of ultraviolet light are 75 μW / cm 2and 254 nm, the dosing concentration of the modification reagent H2O2 is 0.35 mol / L, the dosing amount of the modification reagent H2O2 is 160 g per cubic meter of the reactor, the magnetic catalyst is nano-Fe3O4, the magnetic catalyst concentration is 1.0 kg per cubic meter of the reactor, and the operating temperature of the countercurrent bed is 50 °C. SO2, NO x and Hg 0 concentrations are 1800 ppm, 350 ppm, and 60 μg / m 3 . The test results on the small experimental system are as follows: SO2, NO x and Hg 0 simultaneous removal efficiencies can reach 87.1%, 76.7%, and 87.3% respectively.

[0082] Example 5:

[0083] The activation modification temperature of the photochemical spouted bed is 55 °C, the radiation intensity and wavelength of ultraviolet light are 85 μW / cm 2 and 254 nm, the dosing concentration of the modification reagent H2O2 is 0.45 mol / L, the dosing amount of the modification reagent H2O2 is 200 g per cubic meter of the reactor, the magnetic catalyst is nano-Fe3O4, the magnetic catalyst concentration is 1.0 kg per cubic meter of the reactor, and the operating temperature of the countercurrent bed is 50 °C. SO2, NO x and Hg 0 concentrations are 1800 ppm, 350 ppm, and 60 μg / m 3 . The test results on the small experimental system are as follows: SO2, NO x and Hg 0 simultaneous removal efficiencies can reach 96.1%, 87.9%, and 94.9% respectively.

[0084] Example 6:

[0085] The activation modification temperature of the photochemical spouted bed is 55 °C, the radiation intensity and wavelength of ultraviolet light are 95 μW / cm 2 and 254 nm, the dosing concentration of the modification reagent H2O2 is 0.55 mol / L, the dosing amount of the modification reagent H2O2 is 220 g per cubic meter of the reactor, the magnetic catalyst is nano-Fe3O4, the magnetic catalyst concentration is 1.5 kg per cubic meter of the reactor, and the operating temperature of the countercurrent bed is 50 °C. SO2, NO x and Hg 0 concentrations are 1800 ppm, 350 ppm, and 60 μg / m 3 . The test results on the small experimental system are as follows: SO2, NO x and Hg 0The simultaneous removal efficiencies can reach 100%, 98.5% and 99.2% respectively.

[0086] In the method described in the present invention, the removal of SO2, NO x and mercury, the maximum simultaneous removal efficiencies can reach 100%, 98.5% and 99.2% respectively, with extremely high simultaneous removal efficiency, can achieve the simultaneous removal of single or multiple flue gas pollutants, and no waste water or liquid waste is generated, which can well meet the current strict ultra-low emission requirements and has extremely significant technical competitive advantages.

[0087] 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 system for simultaneous desulfurization, denitrification, and mercury removal using a photochemical spouted tower modified magnetic catalyst, characterized in that, The system includes a photochemical spouted bed (1) for catalyst modification and a countercurrent tower (2) for catalytic removal; Inside the photochemical spouted bed (1), there are multiple heat pipes (3) and ultraviolet lamps (4). On the inner wall of the bottom surface, there are several magneto-catalyst spraying devices (5) evenly distributed. At the top, there is a magneto-catalyst inlet (7) connected to a magneto-catalyst feeding device (6), a modified reagent and its carrying gas inlet (8), and a modified magneto-catalyst outlet (10) connected to a gas-solid impinging mixer (9). Outside the photochemical spouted bed (1), there is an external gas flow circulation bypass (11). One end of the external gas flow circulation bypass (11) is connected to the top of the photochemical spouted bed (1), and the other end is connected to the magneto-catalyst spraying device (5). And a first fan (12) is installed on the external gas flow circulation bypass (11). At the bottom of the photochemical spouted bed (1), there is a first valve (13); At the top of the countercurrent tower (2), there is a first outlet (16) connected to the inlet pipeline of a magnetic separation device (15). On both inner walls, there are several symmetrically distributed gas-solid nozzle arrays (17). The two gas-solid nozzle arrays (17) on both sides are respectively connected to the gas-solid impinging mixer (9) through pipelines. On the pipelines, there are a second fan (19) and a third fan (20) respectively. The gas-solid impinging mixer (9) is connected to a burner (18) through a gas supply pipeline. On the gas supply pipeline, there are a fourth fan (21) and a flue gas temperature regulator (22). On the magnetic separation device (15), there are a magneto-catalyst outlet (23) and a treated flue gas outlet (24). At the bottom of the countercurrent tower (2), there is a second valve (14); The modified reagent is pure H2O2 or a mixture containing H2O2.

2. The system for simultaneously desulfurizing, denitrifying and mercury-removing based on a photochemical spouted tower modified magnetic catalyst according to claim 1, wherein, The ultraviolet lamps (4) in the photochemical spouted bed (1) are arranged in an equal pitch and staggered arrangement. The center lines of the ultraviolet lamps (4) are arranged parallel to the central axis of the photochemical spouted bed (1). The distance between adjacent two ultraviolet lamps (4) is not less than 15 cm. The included angle between adjacent two ultraviolet lamps (4) and the center of the photochemical spouted bed (1) is not less than 20 degrees. The length of the ultraviolet lamps (4) is 20 - 300 cm. The ultraviolet radiation intensity at the center between every two ultraviolet lamps (4) is not less than 20 μW / cm2. The heat pipes (3) are arranged in a staggered arrangement and are arranged at intervals with the ultraviolet lamps (4).

3. The system for simultaneously desulfurizing, denitrifying and mercury-removing based on a photochemical spouted tower modified magnetic catalyst according to claim 1, wherein The cross-section inside the countercurrent tower (2) is circular or rectangular. Gas-solid nozzle arrays (17) are provided on one or more cross-sections. The distance between the gas-solid nozzle arrays (17) on adjacent cross-sections is 15 - 100 cm. The distance between the gas-solid nozzle arrays (17) facing each other on both sides of the same cross-section is 50 - 300 cm.

4. A method for simultaneously desulfurizing, denitrifying and mercury removal by using a photochemical spouted bed modified magnetic catalyst, characterized in that, The method is completed based on the system according to any one of claims 1 - 3. The method includes: (1) Material selection: Select a modified reagent and a magneto-catalyst. The modified reagent is pure H2O2 or a mixture containing H2O2. Calculate the input amounts of the magneto-catalyst and the modified reagent according to the volume of the photochemical spouted bed; (2) Magneto-catalyst modification: Introduce the modified reagent and the magnetic catalyst into the photochemical spouted bed (1). Use the ultraviolet lamp tube to induce H2O2 in the modified reagent to generate hydroxyl radicals (·OH). Use the generated hydroxyl radicals (·OH) to attack the surface of the magnetic catalyst, so that active sites are generated on the surface of the magnetic catalyst, and the magnetic catalyst is repeatedly modified multiple times through the external gas circulation bypass; (3) Catalytic oxidation: The modified magnetic catalyst and the flue gas generated by the burner are introduced into the countercurrent tower, and the active sites on the magnetic catalyst are used to thermally catalytically oxidize SO2, NO, and / or Hg in the flue gas 0 , so that SO2, NO, and / or Hg 0 are respectively oxidized to SO3, NO2 / N2O4 / N2O5, and / or Hg 2+ ; (4) Removal: Separate the magnetic catalyst that has lost its catalytic active sites in step (3) from the flue gas containing SO3, NO2 / N2O4 / N2O5, and / or Hg 2+ through a magnetic separator, and directly send the oxidized flue gas to the subsequent wet flue gas desulfurization system for washing and removal.

5. The method for simultaneously desulfurizing, denitrifying and mercury-removing based on a photochemical spouted tower modified magnetic catalyst according to claim 4, characterized in that, In step (1), the magnetic catalyst includes one or more mixtures of CoFe2O4, MnFe2O4, CuFe2O4, CeFe2O4, Fe2O3, Fe3O4, or magnetic beads in magnetite or coal fly ash; the particle size of the magnetic catalyst is 0.001 - 0.5 μm.

6. The method for simultaneously desulfurizing, denitrifying and mercury removing based on a photochemical spouted tower modified magnetic catalyst according to claim 4, characterized in that, In step (1), the input amount of the magnetic catalyst = the volume of the photochemical spouted bed (1) (m 3 ) × (0.2 - 18 kg); the concentration of the modifying reagent is 0.01 - 3.0 mol / L, and the input amount = the volume of the countercurrent tower (m 3 ) × (0.02 - 2 kg).

7. The method for simultaneously desulfurizing, denitrifying and mercury removing based on a photochemical spouted tower modified magnetic catalyst according to claim 4, characterized in that, In step (2), the ultraviolet light radiation intensity of the ultraviolet lamp tubes in the photochemical spouted bed (1) is 5 - 280 μW / cm 2 , and the effective wavelength of the ultraviolet light is 110 - 320 nm.

8. The method for simultaneously desulfurizing, denitrifying and mercury-removing based on a photochemical spouted tower modified magnetic catalyst according to claim 4, characterized in that, In step (2), the modification temperature in the photochemical spouted tower (1) is 50 to 120 °C; the circulation rate of the external gas circulation bypass is 10 to 500 m 3 / h.

9. The method for simultaneously desulfurizing, denitrifying and mercury-removing based on a photochemical spouted tower modified magnetic catalyst according to claim 4, characterized in that In step (3), the catalytic oxidation temperature in the impact tower is 60 - 220 °C.

10. The method for simultaneously desulfurizing, denitrifying and mercury removing based on a photochemical spouted tower modified magnetic catalyst according to claim 4, wherein In step (4), the magnetic catalyst separated from the oxidized flue gas is re-introduced into the magnetic catalyst feeding device through a pipeline, and active sites are regenerated again by repeating step (2).

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