Gas-liquid mixing components, SO3 removal systems in flue gas, and flue gas desulfurization methods

Abstract

This invention discloses a gas-liquid mixing component. The gas-liquid mixing component is vertically arranged and includes a guide cylinder and a mixing cylinder. The guide cylinder is used to guide gas and liquid into the mixing cylinder in parallel or counter-current flow. The mixing cylinder includes two or more vertically arranged grids, each grid layer comprising several uniformly arranged grid plates with gaps between them, and the gaps between adjacent grid layers are staggered. A bottom plate is provided at the end of the mixing cylinder. The gas-liquid mixing component provided by this invention enhances the radial mixing of flue gas and absorbent liquid, reduces the installation height of the flue gas SO3 removal unit, and improves the flue gas SO3 removal effect.

Description

Technical Field

[0001] This invention belongs to the field of flue gas desulfurization, specifically relating to a gas-liquid mixing component, a flue gas SO3 removal system, and a flue gas desulfurization method. Background Technology

[0002] Large amounts of flue gas containing SO2 and SO3 are generated during production processes in various industries such as power generation, metallurgy, and petrochemicals. Existing data shows that in the power industry, 0.5% to 1.5% of the sulfur in typical coal-fired boilers is oxidized to SO3; under oxygen-enriched regeneration conditions, SO3 accounts for approximately 5% to 10% of the total sulfur oxides in catalytic cracking regeneration flue gas; in the steel industry, SO3 emissions from sintering flue gas account for 1% to 2% of the total sulfur oxide emissions. In SCR denitrification units that commonly use V2O5-based active components, some SO2 is also oxidized to SO3, with a conversion rate of approximately 0.5% to 1.5%, especially when the SCR reactor is operating at low load, where the conversion rate of SO2 to SO3 increases dramatically.

[0003] SO3 is highly corrosive and combines with water vapor in flue gas to form sulfuric acid. At dew point temperatures, this sulfuric acid condenses on the surface of metal components, causing corrosion and perforation in downstream equipment such as waste heat boilers, CO boilers, and air preheaters, and affecting the long-term operation of the unit. SO3 also reacts with escaped ammonia in the SCR denitrification system to form sticky ammonium bisulfate. Large amounts of this ammonium bisulfate deposit in catalyst pores at low temperatures, adhering to fly ash and easily causing pore blockage and reducing catalyst activity. It also enters downstream equipment such as waste heat boilers, CO boilers, and air preheaters with the flue gas and adheres to the surface of heat exchange elements, causing ash accumulation, scaling, blockage, and corrosion. Furthermore, to avoid dew point corrosion from SO3 in the flue gas, boiler exhaust temperatures are generally high, typically above 180°C, resulting in a significant waste of flue gas heat. SO3 emitted from chimneys can also combine with water vapor in the atmosphere to form H2SO4 aerosols. H2SO4 aerosols are precursors to PM2.5 and one of the main culprits of smog. They can be inhaled into the alveoli and deposited in the body, making them difficult to expel, thus posing a great threat to human health.

[0004] When flue gas containing gaseous SO3 passes through a wet flue gas desulfurization system, the flue gas is rapidly cooled below the acid dew point. SO3 rapidly forms submicron-sized H2SO4 aerosols, which are difficult to capture, through homogeneous nucleation and heterogeneous nucleation using particulate matter as condensation nuclei. Generally, larger droplets in the flue gas can be removed by the absorption tower, but it is ineffective against submicron-sized H2SO4 aerosols. The resulting submicron-sized H2SO4 aerosols can only be discharged into the atmosphere through the chimney, creating the "blue smoke" phenomenon at the chimney outlet.

[0005] Patents CN201610596916.7, CN201510298152.9, CN201620429006.5, and CN201510652339.4 all use dry absorbents to remove SO3. These dry absorbents are sodium-based, magnesium-based, or calcium-based. When using dry absorbents for SO3 removal, the smaller the particle size, the higher the SO3 removal efficiency. However, commercially available alkaline powders generally have large particle sizes, making it difficult to meet the particle size requirements for absorbents, thus necessitating grinding. During grinding, the temperature rises sharply, and there is a risk of dust electrostatic explosion. Wet grinding requires the use of dispersants and additives, and temperature control. Continuous grinding can take several hours or even tens of hours, requiring dozens or even hundreds of grinding cycles. The grinding equipment occupies a large area and generates noise pollution. After wet grinding, sieving, dehydration, and drying are also required, making the process cumbersome. Furthermore, dry absorbents are difficult to mix evenly with flue gas when injected into the flue. Patents CN201610265089.3, CN201621053463.5, and CN201610573963.X use wet absorbents to remove SO3 from flue gas, but they lack a mixing mechanism for the flue gas and the injected alkaline solution, requiring a relatively long flue for mixing. Patents CN201610254686.6 and CN201610573963.X employ dual-fluid atomizing spray guns that use air as cooling to prevent blockage and wear of the spray gun barrel due to absorbent evaporation and crystallization caused by high-temperature flue gas, and to prevent excessive deformation from heat during shutdown. However, because air has a relatively small heat capacity, a large amount of air is required to achieve these objectives. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a gas-liquid mixing component, a flue gas SO3 removal system and a flue gas desulfurization method.

[0007] According to a first aspect of the present invention, a gas-liquid mixing component is provided. The gas-liquid mixing component of the present invention is suitable for gas-liquid mixing conditions during semi-dry removal of acidic gases from high-temperature flue gas, and is applicable to a temperature range of 150–800°C.

[0008] A gas-liquid mixing component is arranged vertically, comprising a guide tube and a mixing tube; the guide tube is used to guide gas and liquid into the mixing tube in parallel or countercurrent flow; the mixing tube comprises two or more vertically arranged grids, each grid comprising several uniformly arranged grid plates with gaps between them, and the gaps between adjacent grids are staggered; a bottom plate is provided at the end of the mixing tube.

[0009] Furthermore, the upper edge of the grille is fixed to the upper or lower edge of the guide tube.

[0010] Furthermore, the cross-section of the grid can be circular, square, or other suitable shapes. Let the width of the grid plate be d, the spacing between two adjacent grid layers be (0.5–4)d, preferably (0.5–1.5)d; the gap between the grid plates of each layer is set at an air velocity of (1–20) m / s, preferably (5–10) m / s; the width of the gap between the grid plates is (0.5–4)d, preferably (0.5–1.5)d, and the total opening area is 0.5–1.5 times the cross-sectional area of ​​the mixing cylinder.

[0011] Furthermore, the base plate can be a horizontal plate or a conical plate, preferably a conical plate. The outer edge of the base plate is generally not less than the outer edge of the outermost grid, and the angle α between the conical base plate and the cross-section of the mixing cylinder is not less than the dust repose angle in the flue.

[0012] Furthermore, the mixing cylinder preferably includes three layers of grids, namely an inner annular grid, a middle annular grid, and an outer annular grid, wherein the spacing between two adjacent grid layers is (0.5~1.5)d, and the gap between the grid plates of each grid layer is the same as the grid spacing, which is (0.5~1.5)d.

[0013] Furthermore, let the diameter of the inner annular grid cross-section be D, and the height of the mixing cylinder be 1.0 to 3.0 times the diameter of the mixing cylinder.

[0014] Furthermore, the angle β between the guide tube and the axis of the gas-liquid mixing component is 10–60°, preferably 30–40°. Furthermore, the gas-liquid mixing component is preferably used in a semi-dry flue gas desulfurization system, and is disposed inside a high-temperature flue at 150–800°C, preferably inside a flue at 300–500°C.

[0015] In this invention, the mixing principle of the gas-liquid mixing component is as follows: Flue gas enters the mixing cylinder simultaneously with the atomized absorbent liquid through the guide tube of the gas-liquid mixing component, and flows through the gaps between the inner annular grid plates. Due to the staggered arrangement of the grid plates in each layer of the annular grid, the flow direction of the flue gas and absorbent liquid changes when flowing through the gaps between the inner annular grid plates; that is, it bypasses the middle annular grid plates and passes through the gaps between two adjacent middle annular grid plates. The same phenomenon occurs in the outer annular grid. Simultaneously, during the flow of flue gas / atomized absorbent liquid through the annular grid, a negative pressure is generated on the back of the annular grid plates, thereby accelerating and enhancing the mixing of the flue gas and the atomized absorbent liquid. The reaction between SO3 in the flue gas and the absorbent liquid is itself a rapid reaction between inorganic salts, and this reaction process is mass transfer controlled. Therefore, the mixing process between the flue gas and the atomized absorbent liquid is also the process of removing SO3 from the flue gas.

[0016] According to a second aspect of the present invention, the present invention also provides a flue gas SO3 removal device, including the gas-liquid mixing component described above.

[0017] A flue gas SO3 removal device includes an absorbent tank, an absorbent feed pump, an absorbent circulation pump, a dual-fluid atomizing spray gun, a flue gas / atomized absorbent gas-liquid mixing component, and an atomizing nozzle. The flue gas / atomized absorbent gas-liquid mixing component and the atomizing nozzle are disposed on the internal cross-section of the flue gas duct.

[0018] The dual-fluid atomizing spray gun is disposed inside an outer sleeve, the outer sleeve including a circulating liquid inlet and a circulating liquid outlet;

[0019] The first outlet of the absorbent tank is connected to a dual-fluid atomizing spray gun via a pipeline, an absorbent feed pump, and the absorbent liquid tank.

[0020] The second outlet of the absorbent tank is connected to the circulating liquid inlet of the outer sleeve of the atomizing spray gun via a pipeline and an absorbent circulation pump. The circulating liquid outlet of the outer sleeve is connected to the circulating liquid inlet on the absorbent tank via a pipeline.

[0021] The dual-fluid atomizing spray gun includes several atomizing nozzles, the outlets of which extend into the guide tube of the flue gas / atomizing absorbent mixing component. The atomizing nozzles are coaxially arranged with the guide tube, mixing tube, and grid, extending upward into the guide tube by 0.5D and downward into the mixing tube by 0.5D, so as to ensure that all the atomizing absorbent under the entrainment of flue gas enters the mixing tube.

[0022] Furthermore, the dual-fluid atomizing spray gun is connected to the compressed air pipeline.

[0023] Furthermore, the flue gas SO3 removal device includes a flue sealing plate and several flue gas / atomizing absorbent mixing components embedded in the flue sealing plate, with the flue sealing plate being nearly perpendicular to the flue gas flow direction.

[0024] Furthermore, the flue gas SO3 removal device is installed in the inlet flue of the SCR denitrification reactor, the inlet flue of the air preheater / economizer, the boiler outlet flue, or the inlet flue of the desulfurization reactor in the boiler. The flue is equipped with a flue gas flow measurement device and a sulfur trioxide concentration measurement device.

[0025] Furthermore, a pressure measuring instrument is installed on the inlet absorbent pipe of the dual-fluid atomizing spray gun to monitor the pressure of the sulfur trioxide absorbent entering the spray gun in real time.

[0026] Furthermore, a flow meter and a regulating valve are installed on the compressed air inlet pipe of the dual-fluid atomizing spray gun to regulate and measure the flow rate of compressed air entering the spray gun.

[0027] Furthermore, the absorbent tank also includes inlets for softened water and absorbent powder, both located at the top of the absorbent tank.

[0028] Furthermore, in the absorption tank, the circulating liquid inlet is located 0 to 0.50 m below the liquid surface of the absorption tank.

[0029] Furthermore, the dual-fluid atomizing spray gun and the external sleeve are evenly distributed on the cross-section of the flue and penetrate through the flue. The circulating liquid inlet and the circulating liquid outlet are respectively located at both ends of the external sleeve.

[0030] According to a third aspect of the invention, the invention also provides a desulfurization method in which the flue gas desulfurization device described above is used.

[0031] A flue gas desulfurization method includes the following:

[0032] The absorbent liquid from the first outlet of the absorbent tank is pumped to the dual-fluid atomizing spray gun by the absorbent liquid supply pump. Under the action of compressed air, it is sprayed into the flue gas through the atomizing nozzle of the dual-fluid atomizing spray gun. The absorbent liquid is atomized into micron-sized droplets and enters the mixing cylinder along with the high-temperature flue gas through the gas-liquid mixing component guide tube. In the mixing cylinder, the atomized absorbent liquid droplets and flue gas change from axial flow to radial flow. In the process of passing through the inner annular grid, the middle annular grid and the outer annular grid in turn, the absorbent liquid and flue gas are rapidly mixed and an acid-base neutralization reaction occurs during the mixing process, thereby removing SO3 from the flue gas.

[0033] Furthermore, because the mixing cylinder of the present invention is provided with a conical bottom plate at the end, the angle α between the mixing cylinder and the cross-section of the mixing cylinder is not less than the angle of repose of the dust in the flue, the dust in the flue gas will flow with the flue gas and will not be deposited and block the grid gap.

[0034] Furthermore, the flue gas SO3 removal absorbent is Na2SO3, NaHSO3, Na2CO3 or NaHCO3, or it may be a mixture of several of these absorbents.

[0035] Furthermore, the absorbent is a mixed solution of Na2CO3 / NaHCO3 or a mixed solution of Na2SO3 / NaHSO3.

[0036] Furthermore, the mass concentration of the Na2CO3 / NaHCO3 mixed solution is 5% to 30%, and the mass concentration of the Na2SO3 / NaHSO3 mixed solution is 5% to 25%.

[0037] Furthermore, the amount of absorbent added, calculated as the Na / S molar ratio, is 1:1 to 3:1.

[0038] Taking Na2CO3 as an example, the principle of removing sulfur trioxide from flue gas by the present invention after injecting Na2CO3 solution into the flue gas is as follows:

[0039] SO3 + Na2CO3→Na2SO4 + CO2①

[0040] Because the concentration of SO2 in the flue gas is much higher than that of SO3, Na2CO3 reacts with SO2 in the flue gas:

[0041] SO2 + Na2CO3→Na2SO3 + CO2②

[0042] Na2SO3 continues to react with SO3 in the flue gas:

[0043] SO3 + Na2SO3→Na2SO4 + SO2③

[0044] In this invention, the acid-base neutralization reaction and the mixing process of flue gas / atomizing absorbent occur simultaneously.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. The mixing of flue gas and atomized absorbent in this invention is radial mixing. That is, by setting up mixing components, the radial distance of the flue gas duct is used to achieve uniform mixing of flue gas and atomized absorbent, greatly reducing the installation height of the flue gas SO3 removal unit. When the flue gas SO3 removal unit is installed at the inlet of the flue gas SCR denitrification reactor in the boiler, only the denitrification reactor needs to be modified: the installation and maintenance space above each catalyst layer is appropriately reduced to install the flue gas SO3 removal unit.

[0047] 2. The present invention sets the bottom of the flue gas / atomized absorbent liquid mixing component in a conical shape, which can eliminate the possibility of dust accumulation and blockage of the annular grid. At the same time, a guide tube is set at the inlet of the flue gas / atomized absorbent liquid mixing component, which can minimize the pressure drop of the flue gas deSO3 system.

[0048] 3. Using absorbent liquid instead of cooling air as the cooling medium for the dual-fluid atomizing spray gun prevents high-temperature deformation of the atomizing spray gun and blockage of the spray gun due to crystallization of the absorbent liquid inside the spray gun caused by evaporation. It can make full use of the heat of the flue gas to maintain the temperature of the absorbent liquid tank, prevent the absorbent in the absorbent liquid tank from crystallizing, and also achieve energy saving effect. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the SO3 removal system in flue gas according to the present invention.

[0050] Figure 2 This is a schematic diagram of the SO3 removal device for flue gas of the present invention arranged in the flue.

[0051] Figure 3 This is a schematic diagram of the structure of the flue gas / atomizing absorbent mixing component of the present invention.

[0052] Figure 4 This is a cross-sectional view of the flue gas / atomized absorbent liquid mixing component 1-1 of the present invention.

[0053] The numerical markings correspond to the following components: 1-Absorbent tank, 2-Absorbent feed pump, 3-Absorbent circulation pump, 4-Softened water, 5-Absorbent powder, 6-Compressed air pipeline, 7-Dual-fluid atomizing spray gun, 8-Fluorite, 9-Fluorite / atomized absorbent mixing component, 10-Fluorite sealing plate, 11-Atomizing nozzle, 16-Circulating liquid outlet, 17-Circulating liquid inlet, 18-Absorbent feed outlet, 19-Absorbent powder and softened water inlet; 71-Circulating liquid inlet, 72-Circulating liquid outlet, 73-Outer sleeve, 74-Absorbent; 91-Guide cylinder, 92-Annular sealing plate, 93-Mixing cylinder; 931-Inner annular grid, 932-Middle annular grid, 933-Outer annular grid, 934-Conical bottom plate. Detailed Implementation

[0054] The present invention will now be described in more detail with reference to the accompanying drawings.

[0055] Example 1

[0056] like Figure 2 As shown, a flue gas / atomizing absorbent mixing component is provided in the cross-section of the flue: a flue sealing plate 10 and a flue gas / atomizing absorbent mixing component 9 are provided, wherein the flue gas / atomizing absorbent mixing component 9 is embedded in the flue sealing plate 10 and is arranged perpendicular to the flue gas flow direction. The flue gas / atomizing absorbent mixing component 9 is composed of a guide tube 91, an annular sealing plate 92, and a mixing tube 93. The mixing tube 93 is composed of an inner annular grid 931, a middle annular grid 932, an outer annular grid 933, and a conical bottom plate 934. The three annular grids are arranged coaxially, and their grid plates are staggered. The atomizing nozzle is located on the axis of the annular grid, and its outlet extends into the interior of the guide tube of the flue gas / atomizing absorbent mixing component. Let D be the cross-sectional diameter of the inner annular grid 931, then the atomizing nozzle extends upward into the guide tube by 0.5D and downward into the mixing tube by 0.5D to ensure that all the atomizing absorbent under the entrainment of the flue gas enters the mixing tube. The angle α between the conical base plate 934 and the cross-section should not be less than the dust repose angle inside the flue to prevent dust accumulation.

[0057] Example 2

[0058] This embodiment describes a flue gas desulfurization system. For example... Figure 1 As shown, the SO3 removal system includes an absorbent tank 1, an absorbent feed pump 2, an absorbent circulation pump 3, a dual-fluid atomizing spray gun 7, a flue gas / atomized absorbent mixing component 9, and an atomizing nozzle 11. Figure 1 A schematic diagram of the flue gas desulfurization system of the present invention is provided. Figure 1As shown, the absorbent tank 1 of this invention is provided with a circulating liquid outlet 16, a circulating liquid inlet 17, an absorbent supply outlet 18, and an inlet 19 for the absorbent powder 5 and softened water 4. The cross-section of the flue 8 is provided with uniformly distributed dual-fluid atomizing spray guns 7, on which dual-fluid atomizing nozzles 11 are installed. The dual-fluid atomizing spray guns 7 are disposed inside an outer sleeve 73, which includes a circulating liquid inlet 71 and a circulating liquid outlet 72. The circulating liquid outlet 16 of the absorbent tank 1 is connected to the inlet of the absorbent circulation pump 3, the outlet of the absorbent circulation pump 3 is connected to the circulating liquid inlet 71 of the outer sleeve 73 of the dual-fluid atomizing spray gun 7, and the circulating liquid outlet 72 of the outer sleeve 73 is connected to the circulating liquid inlet 17 of the absorbent tank 1. The circulating liquid outlet 18 of the absorbent tank 1 is connected to the inlet of the absorbent supply pump 2, the outlet of the absorbent supply pump 2 is connected to the absorbent inlet 74 of the dual-fluid atomizing spray gun 7, and the compressed air inlet of the dual-fluid atomizing spray gun 7 is connected to the compressed air pipeline 6.

[0059] Example 3

[0060] This embodiment provides a method for flue gas desulfurization. For example... Figure 1 As shown, softened water 4 and absorbent powder 5 enter the absorbent tank 1 through absorbent tank inlet 19 and dissolve. Then, under the stirring action of the circulating liquid with a higher temperature that returns from the circulating liquid inlet 17 after being heated by flue gas, the mixing and dissolution are accelerated.

[0061] The circulating liquid (absorbent) is delivered from the circulating liquid outlet 16 to the absorbent circulation pump 3, and then to the outer sleeve 73 of the dual-fluid atomizing spray gun 7, which is connected to the circulating liquid inlet 71. This serves as a cooling medium to protect the spray gun. After being heated by flue gas, it returns to the absorbent tank 1 from the absorbent tank 1 through the circulating liquid outlet 72 on the outer sleeve 73 and the circulating liquid inlet 17. During normal operation, the liquid phase temperature in the absorbent tank should be maintained between 25 and 40°C to ensure complete dissolution of the absorbent. Hot water or steam heating can be used if necessary.

[0062] The absorbent liquid is pumped from the first outlet 18 of the absorbent liquid tank 1 (i.e. the absorbent liquid supply outlet) into the dual-fluid atomizing spray gun 7 via the absorbent liquid supply pump 2. Compressed air 6 enters the dual-fluid atomizing spray gun 7 at the same time as the absorbent liquid atomizing air, and the absorbent liquid is atomized and sprayed into the flue 8 through the atomizing nozzle 11.

[0063] The flue gas in the flue 8 passes through the flue gas / atomizing absorbent mixing component 9 and the guide tube 91, and enters the mixing tube 93 simultaneously with the atomizing absorbent. Due to the obstruction of the conical bottom plate 934, the flue gas and atomizing absorbent flow through the inner annular grid 931, the middle annular grid 932 and the outer annular grid 933 in sequence. During this process, the flue gas and atomizing absorbent are vigorously mixed and an acid-base neutralization reaction occurs, and SO3 in the flue gas is removed.

[0064] The flue gas SO3 removal absorbent of the present invention is a solution prepared from Na2SO3, NaHSO3, Na2CO3, NaHCO3, or a mixture of several of these absorbents, with a mass concentration of 5% to 30%, and the amount of absorbent added, in terms of Na / S molar ratio, is 1:1 to 3:1.

Claims

1. A device for the removal of SO3 from flue gas, characterized in that The device comprises an absorption liquid tank, an absorption liquid supply pump, an absorption liquid circulating pump, a double-fluid atomizing spray gun, a flue gas / atomizing absorption liquid mixing member and an atomizing nozzle, the flue gas / atomizing absorption liquid mixing member and the atomizing nozzle are arranged on the internal cross section of the flue, wherein, The flue gas / atomizing absorption liquid mixing member is arranged in vertical direction and comprises a flow guide cylinder and a mixing cylinder, the flow guide cylinder is used for introducing the gas and liquid into the mixing cylinder in parallel flow, the mixing cylinder comprises two or more layers of vertically arranged grids, each layer of the grid comprises a plurality of grid plates which are uniformly arranged and have gaps between each other, the gaps of the adjacent two layers of the grid are arranged in staggered manner, and the end of the mixing cylinder is provided with a bottom plate. The double-fluid atomizing spray gun is arranged in the internal sleeve, and the internal sleeve comprises a circulating liquid inlet and a circulating liquid outlet. The first outlet of the absorption liquid tank is connected with the double-fluid atomizing spray gun through a pipeline and the absorption liquid supply pump, the second outlet of the absorption liquid tank is connected with the circulating liquid inlet of the external sleeve of the atomizing spray gun through a pipeline and the absorption liquid circulating pump, and the circulating liquid outlet of the external sleeve is connected with the circulating liquid inlet of the absorption liquid tank through a pipeline. The double-fluid atomizing spray gun comprises a plurality of atomizing nozzles, the outlets of the atomizing nozzles extend into the flow guide cylinder of the flue gas / atomizing absorption liquid mixing member, and the atomizing nozzles are coaxially arranged with the flow guide cylinder and the mixing cylinder.

2. The flue gas SO3 removal device according to claim 1, characterized in that The upper edge of the grid is fixed to the lower edge of the flow guide cylinder.

3. The flue gas SO3 removal device according to claim 1, characterized by The cross section of the grid is circular or square.

4. The flue gas SO3 removal device according to claim 1, characterized by The grid plate width is d, the distance between the adjacent two layers of the grid is 0.5d-4d, the gap width between the grid plates of each layer of the grid is 0.5d-4d, and the total opening area is 0.5-1.5 times of the cross section area of the mixing cylinder.

5. The flue gas SO3 removal device according to claim 1, characterized by The bottom plate is a horizontal plate or a conical plate.

6. The flue gas SO3 removal device according to claim 5, characterized by The bottom plate is a conical plate, the outer edge of the bottom plate is not less than the outer edge of the outermost layer of the grid, and the included angle α between the conical bottom plate and the cross section of the mixing cylinder is not less than the repose angle of the dust in the flue.

7. The flue gas SO3 removal device according to claim 4, characterized by The mixing cylinder comprises three layers of grids, which are an inner layer of annular grid, an intermediate layer of annular grid and an outer layer of annular grid, and the distance between the adjacent two layers of the grid is 0.5d-1.5d, and the gap between the grid plates of each layer of the grid is the same as the distance between the grids, which is 0.5d-1.5d.

8. The flue gas SO3 removal device according to claim 7, characterized by The diameter D of the cross section of the inner layer of annular grid is 1.0-3.0 times of the height of the mixing cylinder.

9. The flue gas SO3 removal device according to claim 1, characterized by The flue gas SO3 removal device comprises a flue sealing plate and a plurality of flue gas / atomizing absorption liquid mixing members which are inlaid on the flue sealing plate, and the flue sealing plate is nearly perpendicular to the flue gas flow direction.

10. The flue gas SO3 removal device according to claim 1, characterized by The flue gas SO3 removal device is arranged in the SCR denitration reactor inlet flue, the air preheater / economizer inlet flue, the boiler outlet flue or the desulfurization reactor inlet flue in the boiler, and the flue gas flow measuring device and the sulfur trioxide concentration measuring device are arranged in the flue.

11. The flue gas SO3 removal device according to claim 1, characterized by A pressure measuring instrument is arranged on the absorption liquid pipeline of the double-fluid atomizing spray gun inlet to monitor the sulfur trioxide absorption liquid pressure entering the spray gun in real time.

12. The flue gas SO3 removal device according to claim 1, characterized by A flow meter and an adjusting valve are arranged on the compressed air pipeline of the double-fluid atomizing spray gun inlet to adjust and measure the compressed air flow entering the spray gun.

13. The flue gas SO3 removal device according to claim 1, characterized by The double-fluid atomizing lance and the outer sleeve are evenly distributed on the flue cross section and are arranged through the flue, and the circulating liquid inlet and the circulating liquid outlet are arranged at two ends of the outer sleeve.

14. A method of flue gas desulfurization, characterized by, The flue gas SO3 removal device of claim 7 or 8 is applied, and the method comprises the following contents: The first outlet of the absorption liquid tank is connected with the double-fluid atomizing lance through the absorption liquid supply pump, and the absorption liquid is atomized into micron-sized droplets under the action of compressed air and sprayed into the flue gas through the atomizing nozzle of the double-fluid atomizing lance, and then the absorption liquid and the high-temperature flue gas enter the mixing cylinder through the guide cylinder of the flue gas / atomized absorption liquid mixing component; In the mixing cylinder, the atomized absorption liquid droplets and the flue gas change from axial flow to radial flow, and the absorption liquid and the flue gas are rapidly mixed during the process of sequentially passing through the inner ring-shaped grid, the middle ring-shaped grid and the outer ring-shaped grid, and acid-base neutralization reaction occurs during the mixing process, so that SO3 in the flue gas is removed.

15. The flue gas desulfurization method according to claim 14, characterized by, The absorption liquid is Na2SO3 solution, NaHSO3 solution, Na2CO3 solution or NaHCO3 solution, or a mixed solution of several solutions.

16. The flue gas desulfurization method according to claim 15, characterized by, The absorption liquid is Na2CO3 / NaHCO3 mixed solution or Na2SO3 / NaHSO3 mixed solution.

17. The flue gas desulfurization method according to claim 16, characterized by, The mass concentration of the Na2CO3 / NaHCO3 mixed solution is 5% to 30%, and the mass concentration of the Na2SO3 / NaHSO3 mixed solution is 5% to 25%.

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