Ammonia desulfurization method for significantly reducing ammonia slip and its application

Abstract

The present application discloses an ammonia desulfurization method and its application that significantly reduces ammonia escape, and belongs to the technical field of flue gas ammonia desulfurization. The desulfurization method comprises the following steps: (1) the flue gas enters the concentration and cooling section from the flue gas inlet and is cooled to below 60°C; (2) the flue gas then rises to the absorption section and passes through the first packing layer, the second spray mechanism and the first-stage demister for defog, and then enters the purification section; (3) the flue gas passes through the second packing layer and water washing in the purification section to capture ammonium sulfate and excess ammonia, and then passes through the combined demister for defog, and then enters the chimney to meet the emission standards; (4) compressed air enters the oxidation section to oxidize the absorption liquid refluxed from the absorption section, and the liquid formed after full oxidation is then sent to the absorption section for spraying. This method can significantly reduce the amount of ammonia escape while also improving the absorption efficiency of sulfur dioxide in the flue gas, fundamentally and significantly reducing ammonia escape, and avoiding the occurrence of aerosol phenomenon.

Description

Technical Field

[0001] The present application relates to an ammonia desulfurization method for significantly reducing ammonia slip and its application, belonging to the technical field of flue gas ammonia desulfurization. Background Art

[0002] Ammonia desulfurization is currently the most commonly used flue gas desulfurization method. It has the advantages of high desulfurization efficiency and wide application range. In addition, the ammonium sulfite generated in the desulfurization process reacts chemically with the oxygen in the air in the oxidation section to generate ammonium sulfate, which is then concentrated and crystallized into a solid ammonium sulfate by-product. This by-product can also be used to prepare fertilizers, thereby achieving effective utilization of resources.

[0003] However, the current ammonia-based desulfurization technology has the disadvantages of large ammonia escape and serious aerosol phenomenon, which hinders the promotion and use of ammonia-based desulfurization technology. Researchers have found that ammonia escape is one of the main reasons for the formation of aerosols. Therefore, if the ammonia escape cannot be effectively reduced, the generation of aerosol phenomenon cannot be completely avoided. Therefore, significantly reducing ammonia escape is the key to the successful application of ammonia-based desulfurization technology.

[0004] In order to reduce the amount of ammonia escape, there are currently two main ways. One is through process control, which is generally to increase the oxidation rate of ammonium sulfite, change the ammonia addition point, control the pH value of the absorption liquid and the temperature of the absorption section. However, the above process changes will inevitably affect the amount of sulfur dioxide removed; the second is through the addition of an ammonia escape inhibitor. By adding an ammonia escape inhibitor to the absorption liquid, a protective layer is formed on the surface of the absorption liquid to block the impact of the gas on the absorption liquid, and avoid the decomposition of ammonia water, sulfurous acid and ammonium sulfite in the absorption liquid into ammonia and sulfur dioxide, thereby reducing the amount of ammonia escape. This method forms a protective layer on the surface of the absorption liquid. Although it reduces the decomposition of substances in the absorption liquid into ammonia and sulfur dioxide, it also hinders the absorption of sulfur dioxide in the flue gas by the absorption liquid, and therefore also reduces the amount of sulfur dioxide removed.

[0005] Therefore, the current method of reducing ammonia slip has the problem that the amount of ammonia slip can be reduced to a limited extent and the amount of flue gas desulfurization can be hindered. Summary of the invention

[0006] In order to solve the above problems, an ammonia desulfurization method for significantly reducing ammonia slip is provided. The method can significantly reduce the amount of ammonia slip while improving the absorption efficiency of sulfur dioxide in flue gas, fundamentally and significantly reduce ammonia slip, and avoid the occurrence of aerosol phenomenon.

[0007] According to one aspect of the present application, an ammonia desulfurization method for significantly reducing ammonia escape is provided, and a desulfurization tower for ammonia desulfurization is provided, wherein the desulfurization tower is sequentially divided into a demisting section, a purification section, an absorption section, a concentration and cooling section, and an oxidation section from top to bottom, and a flue gas inlet and a liquid discharge port are provided on the side wall of the concentration and cooling section, comprising the following steps:

[0008] (1) Flue gas enters the concentration and cooling section from the flue gas inlet, and is sprayed and cooled to below 60°C by the first spray mechanism. The concentrated liquid in the concentration and cooling section enters the crystallization tank through the drain port. The upper concentrated liquid in the crystallization tank overflows into the concentration circulation tank. The concentration pump then sends the liquid in the concentration circulation tank into the concentration and cooling section for spraying. When the solid content in the crystallization tank reaches the first threshold, the material at the bottom of the crystallization tank is transported to the ammonium sulfate product processing mechanism;

[0009] (2) The flue gas then rises to the absorption section and passes through the first packing layer, the second spray mechanism and the first-stage demister for defogger before entering the purification section. The liquid in the absorption section re-enters the oxidation section through the reflux pipe;

[0010] (3) In the purification section, the flue gas passes through the second packing layer and water washing to capture the entrained ammonium sulfate solution and excess ammonia. After that, it is defogged by the combined demister in the demisting section and then discharged from the desulfurization tower into the chimney. The water washing liquid in the purification section is then returned to the circulating water tank;

[0011] (4) Compressed air enters the oxidation section to oxidize the absorption liquid returned from the absorption section. The liquid formed after full oxidation is then sent to the absorption section for spraying. When the ammonium sulfate content in the oxidation section reaches the second threshold, a portion of the liquid is sent to the concentration circulation tank.

[0012] Optionally, the concentration and cooling section and the absorption section are separated by a first partition, and a plurality of evenly distributed gas lifting caps are arranged on the first partition;

[0013] The air lift cap comprises a cover plate, an air lift cylinder and a cone cap from top to bottom. The cross-sectional area of ​​the cover plate is larger than the cross-sectional area of ​​the air lift cylinder. The upper part of the side wall of the air lift cylinder is provided with at least four air outlets, and the lower part of the side wall is provided with at least four air inlet holes.

[0014] Optionally, the ratio of the diameter of the cover plate to the diameter of the lift cylinder is (1.1-1.4):1.

[0015] Optionally, a baffle is arranged around the cover plate, the top surface of the baffle is higher than the top surface of the cover plate, and the bottom surface of the baffle is lower than the bottom surface of the cover plate.

[0016] Optionally, the first spray mechanism and the second spray mechanism each include a plurality of circular brackets, each circular bracket of the second spray mechanism is provided with a plurality of three-layer spiral cone nozzles, and the three-layer spiral cone nozzles are evenly distributed in the longitudinal and transverse directions, and each circular bracket of the first spray mechanism is provided with a plurality of volute nozzles, and the volute nozzles are evenly distributed in the longitudinal and transverse directions.

[0017] Optionally, the three-layer spiral cone nozzle and the volute nozzle on the outermost circular bracket are both 700-1200 mm away from the desulfurization tower wall.

[0018] Optionally, there are 1-2 first packing layers, and the height of each first packing layer is 400-600 mm;

[0019] The number of the second packing layer is one and the height is 400-450 mm.

[0020] Optionally, the first filler layer and the second filler layer are both formed by regular corrugated plates arranged in parallel, the regular corrugated plates have a thickness of 1-2 mm and a spacing of 10-30 mm, and the regular corrugated plates are obtained by extrusion molding of a modified polypropylene composite material.

[0021] Optionally, the modified polypropylene composite material includes, by weight, 100-120 parts of modified polypropylene, 5-15 parts of 1-hexadecyl-3-methylimidazole nitrate ionic liquid, 10-20 parts of glass fiber, 5-8 parts of heat stabilizer and 5-8 parts of antioxidant, and the modified polypropylene is obtained by grafting polypropylene with an olefin monomer having a piperazine group.

[0022] The regular corrugated plate made of modified polypropylene composite material can realize the redistribution of flue gas, making the components in the flue gas in each area more uniform and improving the desulfurization consistency; secondly, it can prolong the residence time of flue gas in the first packing layer and the second packing layer, increase the contact time with the absorption liquid and the washing liquid, thereby improving the desulfurization rate.

[0023] The modified polypropylene in the composite material is the main body, which can not only play the above-mentioned role, but also promote the absorption and decomposition of sulfur dioxide by the absorption liquid and the water washing liquid to produce reabsorption of ammonia, thereby improving the desulfurization rate and significantly reducing ammonia escape; the applicant found that the filler layer prepared from modified polypropylene alone can have a good effect in the initial use, but after long-term use, cracks will appear in the regular corrugated plate, and cracks will appear in severe cases. Therefore, with long-term use, the effect of desulfurization and reducing ammonia escape will be significantly reduced. Therefore, adding glass fiber to the composite material to strengthen the modified polypropylene can prevent cracks in the corrugated plate, thereby extending the time for the modified polypropylene to work, so that it can still maintain a high effect of promoting desulfurization and ammonia reabsorption in long-term use; the addition of 1-hexadecyl-3-methylimidazole nitrate ionic liquid can promote the compatibility of glass fiber with the modified polypropylene matrix, thereby improving the dispersion uniformity of glass fiber in the modified polypropylene, further improving the mechanical uniformity of the regular corrugated plate, and extending the time for the regular corrugated plate to work.

[0024] Optionally, the preparation method of the modified polypropylene is:

[0025] S1: 100 parts of polypropylene by weight are placed in a closed reactor, and nitrogen containing 5-8 vol% chlorine is introduced for activation treatment at 80-90°C for 2-3 hours;

[0026] S2: Exclude chlorine, add 10-15 parts of olefin monomers with piperazine groups into the reaction kettle, carry out grafting treatment at 100-120°C for 5 hours, wash and dry to obtain modified polypropylene.

[0027] Optionally, the heat stabilizer is selected from at least one of thioesters, organotins, hindered amines, hindered phenols, diphenyl phosphite or triphenyl phosphite.

[0028] Optionally, the thioester is selected from di(dodecanol) thiodipropionate, di(octadecyl) thiodipropionate, di(tridecanol) thiodipropionate or di(tetradecyl) thiodipropionate;

[0029] The organotin heat stabilizer is selected from tin salts containing mercaptides, tin maleates or tin carboxylates, the tin salt containing mercaptides is di-n-octyltin dimercaptoacetate or dimethyl dimercaptoacetate iso-octyltin, the tin maleate is selected from di-n-butyltin maleate; the tin carboxylate is selected from di-n-butyltin dilaurate or di-n-octyltin dilaurate;

[0030] The hindered amine is selected from naphthylamine, diphenylamine or p-phenylenediamine;

[0031] The hindered phenols are selected from 2,6-tert-butyl-4-methylphenol, bis(3,5-tert-butyl-4-hydroxyphenyl)sulfide or pentaerythritol tetrakis[β-(3,5-tert-butyl-4-hydroxyphenyl)propionate.

[0032] Optionally, the structural formula of the olefin monomer with a piperazine group is:

[0033] ;

[0034] Wherein R1 is selected from H or tert-butyloxycarbonyl, R2 is selected from H and / or alkyl, R3 is selected from (CH2)n, and the value range of n is 1-3.

[0035] Optionally, at least one layer of hollow absorption membrane is further arranged above the first filler layer, and the hollow absorption membrane comprises a modified polypropylene fiber membrane and a modified layer arranged on the olefin fiber membrane;

[0036] The modified polypropylene fiber membrane is composed of 70-80 parts of polypropylene, 5-10 parts of polyacrylic acid, 10-25 parts of polyacrylonitrile and 4-5 parts of nano filler by weight;

[0037] The modified layer is a copolymer of acrylamide, an olefin monomer with a piperazine group and diethylaminoethyl methacrylate.

[0038] The hollow absorption membrane added above the first filler layer combines membrane absorption with ammonia desulfurization methods, which can greatly reduce the use of ammonia water, and thus reduce ammonia escape from the source. The modified polypropylene fiber membrane used in the hollow absorption membrane is used as the lower layer of the hollow absorption membrane. First, it can provide stable support, and second, it can extend the residence time of the flue gas entering the hollow absorption membrane, increase the desulfurization amount of the absorption liquid, and then achieve a higher desulfurization rate based on a lower amount of ammonia water added, greatly saving the desulfurization cost; the modified layer can selectively absorb sulfur dioxide in the flue gas, further improve the desulfurization rate, and can also reabsorb the decomposed ammonia to further reduce ammonia escape.

[0039] The modified polypropylene fiber membrane is a blend of polyacrylic acid and polyacrylonitrile. First, it can promote the reabsorption of decomposed ammonia by the hollow absorption membrane, thereby reducing ammonia escape; second, it can improve the temperature resistance and durability of the modified polypropylene fiber membrane and extend the service life of the hollow absorption membrane. The added nanofiller can improve the mechanical strength and temperature resistance of the hollow absorption membrane, ensuring that the hollow absorption membrane will not degrade or rupture in the absorption section, further improving the service life of the hollow absorption membrane.

[0040] Optionally, the nanofiller is selected from at least one of nano-silicon carbide, nano-calcium carbonate, and nano-diamond.

[0041] Optionally, the particle size of the nanofiller is 50-80 nm.

[0042] Optionally, the modified polypropylene fiber membrane has a thickness of 60-80 μm, an average pore size of 70-75 nm, a porosity of 60-70%, and a thickness of 20-30 μm for the modified layer.

[0043] Optionally, the weight ratio of acrylamide, olefin monomer with piperazine group and diethylaminoethyl methacrylate in the modified layer is 1: (0.1-0.15): (0.1-0.2). Acrylamide, as the main structure of the modified layer, can promote the absorption of sulfur dioxide by the modified layer, and the olefin monomer with piperazine group can promote the function of acrylamide and improve the reabsorption rate of decomposed ammonia. However, too many olefin monomers with piperazine group will increase the density of the modified layer, which is not conducive to the passage of flue gas and reduces the treatment efficiency of flue gas. Therefore, diethylaminoethyl methacrylate is added to overcome this defect. The addition of diethylaminoethyl methacrylate can adjust the gas flux of the modified layer, thereby increasing the amount of flue gas passing through; secondly, it cooperates with the olefin monomer with piperazine group to improve the reabsorption rate of decomposed ammonia and doubly reduce ammonia escape.

[0044] Optionally, the preparation method of the hollow absorption film is:

[0045] S11: Blending polypropylene, polyacrylic acid, polyacrylonitrile and nanofiller, extruding to obtain pellets, melt spinning the pellets to obtain primary fibers, stretching the primary fibers to form pores, and treating at 100-110° C. for 200 seconds to obtain a modified polypropylene fiber membrane;

[0046] S12: acrylamide, an olefin monomer having a piperazine group and diethylaminoethyl methacrylate are placed in a solvent and mixed, azobisisobutyronitrile is added, and prepolymerized at 50-70° C. for 2-3 hours to obtain a prepolymer solution;

[0047] S13: coating the prepolymer solution on a modified polypropylene fiber membrane, and then drying at 30-40° C. for 10-15 hours to form a modified layer, thereby obtaining a hollow absorption membrane.

[0048] According to another aspect of the present application, there is provided application of any of the above-mentioned ammonia desulfurization methods for significantly reducing ammonia slip in flue gas desulfurization.

[0049] The beneficial effects of this application include but are not limited to:

[0050] 1. According to the desulfurization method of the present application, the design of the first packing layer, the second packing layer and the gas lifting cap can realize the redistribution of flue gas and increase the contact area between flue gas and liquid, fundamentally improve the absorption amount and absorption efficiency of sulfur dioxide, and can also reabsorb the decomposed ammonia into the absorption liquid to reduce the ammonia escape amount.

[0051] 2. According to the desulfurization method of the present application, the first packing layer and the second packing layer are arranged by using regular corrugated plates made of modified polypropylene composite materials. Firstly, the strength of the regular corrugated plates can be improved to prevent cracks from being generated during long-term use. Secondly, the absorption liquid can be promoted to absorb sulfur dioxide in the flue gas and reabsorb ammonia, thereby improving the desulfurization rate and reducing the amount of ammonia escape.

[0052] 3. According to the desulfurization method of the present application, the olefin monomer with piperazine group is used to graft-modify polypropylene, so that the side chain of polypropylene has piperazine group. It has been verified that the modified polypropylene with the group can promote the absorption of sulfur dioxide and the reabsorption of ammonia by the absorption liquid when in contact with the absorption liquid, especially at low temperature, it can maintain a high absorption rate of sulfur dioxide and reabsorption rate of ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0054] Figure 1 This is a schematic diagram of the structure of the desulfurization system involved in Example 1 of the present application;

[0055] Figure 2 This is a schematic diagram of the structure of the desulfurization tower involved in Example 1 of the present application;

[0056] Figure 3 This is a schematic structural diagram of the air lifting cap involved in Example 1 of the present application;

[0057] Figure 4 This is a schematic structural diagram of a three-layer spiral cone nozzle involved in Example 1 of the present application;

[0058] Figure 5 This is another structural schematic diagram of the desulfurization tower involved in Example 3 of the present application.

[0059] List of parts and reference numerals:

[0060] 10. Desulfurization tower; 11. Purification section; 111. Combined demister; 112. Water washing spray mechanism; 113. Second packing layer; 114. Water washing pump; 12. Absorption section; 121. First packing layer; 122. Second spray mechanism; 123. Primary demister; 124. Reflux pipe; 125. Second partition; 126. Circulation pump; 127. Hollow absorption membrane; 13. Concentration and cooling section; 131. Flue gas inlet; 132. First spray mechanism; 133. Concentration pump; 134. The first partition; 14, oxidation section; 141, air inlet; 142, third partition; 20, crystallization tank; 21, crystallization pump; 30, circulating water tank; 40, ammonium sulfate product processing mechanism; 50, air lift cap; 51, cover plate; 52, air lift cylinder; 53, cone cap; 54, air outlet; 55, air inlet; 56, baffle; 60, three-layer spiral cone nozzle; 61, volute nozzle; 70, concentration circulation tank; 80, liquid tank; 81, liquid pump; 90, water replenishment mechanism; 91, ammonia replenishment mechanism. DETAILED DESCRIPTION

[0061] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0062] Unless otherwise specified, the raw materials in the examples and comparative examples of the present application were purchased through commercial channels.

[0063] Unless otherwise specified, the methods used in the examples and comparative examples of the present application are conventional methods in the prior art. The heat stabilizer used in the following Examples 2 and 3 is p-phenylenediamine, and the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0064] Example 1

[0065] refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 This embodiment discloses a desulfurization system for ammonia desulfurization, which includes a desulfurization tower 10, a crystallization tank 20, a circulating water tank 30 and an ammonium sulfate product processing mechanism 40. The desulfurization tower 10 is divided into a demisting section, a purification section 11, an absorption section 12, a concentration and cooling section 13 and an oxidation section 14 from top to bottom:

[0066] The oxidation section 14 is provided with an air inlet 141, and the air oxidizes the liquid in the oxidation section 14, and the oxidized liquid is sprayed by the absorption section 12. When the ammonium sulfate content in the oxidation section 14 reaches a second threshold value, a portion of the liquid is sent to the concentration circulation tank 70;

[0067] A flue gas inlet 131 and a liquid discharge port are provided on the side wall of the concentration and cooling section 13. A first spray mechanism 132 is provided above the concentration and cooling section 13. The first spray mechanism 132 is connected to a concentration pump 133. The concentration pump 133 is used to transport the concentrated liquid in the concentration circulation tank 70 to the first spray mechanism 132. The liquid after spraying flows back to the crystallization tank 20 through the liquid discharge port for crystallization. The upper concentrated liquid in the crystallization tank 20 overflows to the concentration circulation tank 70. When the solid content in the crystallization tank 20 is greater than the first threshold value, the material at the bottom of the crystallization tank 20 is transported to the ammonium sulfate product processing mechanism 40 through the crystallization pump 21. The oxidation section and the concentration and cooling section are separated by a third partition 142. The third partition 142 has two types: an inclined partition and a ridge partition. The ridge is further divided into a positive ridge and an inverted ridge. The type of the third partition 142 is determined according to actual needs.

[0068] The oxidation section 14, the concentration and cooling section 13, the absorption section 12, and the purification section 11 of the desulfurization tower are separated into four independent systems by the third partition 142, the first partition 134, and the second partition 125: an oxidation system, a concentration and cooling system, an absorption system, and a purification system.

[0069] The concentration and cooling section 13 and the absorption section 12 are separated by a first partition 134, and a plurality of evenly distributed gas lifting caps 50 are arranged on the first partition 134. A first packing layer 121 is arranged above the gas lifting cap 50. A first-level demister 123 and a second spray mechanism 122 are arranged from top to bottom above the absorption section 12. The second spray mechanism 122 is arranged above the first packing layer 121. The circulation pump 126 transports the liquid in the oxidation section 14 to the second spray mechanism 122 for flue gas absorption, and the liquid at the bottom of the absorption section 12 re-enters the oxidation section 14 through the reflux pipe 124;

[0070] The absorption section 12 and the purification section 11 are separated by a second partition 125, and a plurality of evenly distributed air lifting caps 50 are also provided on the second partition 125. A combined demister 111, a water washing spray mechanism 112, and a second packing layer 113 are sequentially provided in the purification section 11 from top to bottom. The water washing pump 114 transports the water in the circulating water tank 30 to the water washing spray mechanism 112 for flue gas water washing, and the water washing liquid in the purification section 11 flows back to the circulating water tank 30.

[0071] The method of using the desulfurization system is:

[0072] (1) The flue gas after dust removal enters the concentration and cooling section 13 from the flue gas inlet 131, and is sprayed and cooled to below 60°C by the first spray mechanism 132. The concentrated liquid in the concentration and cooling section enters the crystallization tank 20 through the discharge port. The upper concentrated liquid in the crystallization tank 20 overflows to the concentration circulation tank 70. The concentration pump 133 then sends the liquid in the concentration circulation tank into the concentration and cooling section for spraying. When the solid content in the crystallization tank 20 reaches a first threshold value (for example, more than 20%), the material at the bottom of the crystallization tank 20 is transported to the ammonium sulfate product processing mechanism 40;

[0073] (2) The flue gas then rises to the absorption section 12, passes through the first packing layer 121, the second spray mechanism 122 and the primary demister 123 for defog, and then enters the purification section 11. The liquid in the absorption section 12 re-enters the oxidation section 14 through the reflux pipe 124;

[0074] (3) The flue gas passes through the second packing layer 113 and water washing in the purification section 11 to capture ammonium sulfate and excess ammonia. After that, the flue gas is defogged by the combined defogger 111 in the demisting section and then discharged from the desulfurization tower 10 into the chimney. The water washing liquid in the purification section 11 is then returned to the circulating water tank 30.

[0075] (4) Compressed air enters the oxidation section 14 to oxidize the absorption liquid refluxed from the absorption section 12. The liquid formed after sufficient oxidation is then sent to the absorption section 12 for spraying. When the content of ammonium sulfate in the oxidation section 14 reaches a second threshold value (for example, above 95%), a portion of the liquid is sent to the concentration circulation tank 70.

[0076] Specifically, the uniform distribution of the rising air caps 50 on the first partition 134 and the second partition 125 includes both longitudinal uniform distribution and lateral uniform distribution. Those skilled in the art can set them to a suitable arrangement shape according to the needs of installation or production, such as a square arrangement, a polygonal arrangement, etc. The above arrangement does not constitute a limitation to the present application, as long as the flue gas can be evenly distributed so that the flue gas can be evenly contacted with the absorption liquid or the washing liquid.

[0077] As an embodiment, it also includes a concentration circulation tank 70 and a feed liquid tank 80, the concentration circulation tank 70 is connected to the crystallization tank 20, the feed liquid tank 80 is connected to the ammonium sulfate product processing mechanism 40 and is connected to the crystallization tank 20 through a feed liquid pump 81.

[0078] The upper concentrated liquid of the crystallization tank 20 first enters the concentration circulation tank 70, and then the liquid in the concentration circulation tank 70 is sent to the concentration and cooling section for spraying through the concentration pump 133. The liquid treated by the cyclone in the ammonium sulfate product processing mechanism 40 enters the feed liquid tank 80, and the liquid in the feed liquid tank 80 is then transported to the crystallization tank 20 through the feed liquid pump 81 to participate in circulation and crystallization.

[0079] The provision of the concentration circulation tank 70 can improve the component stability of the spray liquid in the concentration cooling section 13, and the provision of the liquid tank 80 and the liquid pump 81 can improve the utilization rate of ammonia in the overall desulfurization system and reduce the flue gas treatment cost.

[0080] As an embodiment, it also includes a water replenishment mechanism 90 and an ammonia replenishment mechanism 91. The inlet of the water replenishment mechanism 90 is arranged above the desulfurization tower 10, and the ammonia water inlet of the ammonia replenishment mechanism 91 is arranged on the pipeline that transports the absorption liquid from the oxidation section 14 to the absorption section 12.

[0081] As an implementation method, refer to Figure 3 The air lift cap 50 includes a cover plate 51, an air lift cylinder 52 and a cone cap 53 from top to bottom. The cross-sectional area of ​​the cover plate 51 is larger than the cross-sectional area of ​​the air lift cylinder 52. The upper part of the side wall of the air lift cylinder 52 is provided with at least four air outlet holes 54, and the lower part of the side wall is provided with at least four air inlet holes 55.

[0082] Under this arrangement, the flue gas enters the air riser 52 from the air inlet 55, stays there for a short time, and then flows out from the air outlet 54. Since the air outlet 54 is arranged on the side wall of the air riser 52, the flue gas flows first horizontally and then upwards. The cover plate 51 is arranged to receive the sprayed absorption liquid. After the absorption liquid is sprayed onto the cover plate 51, it will be splashed again to form an annular water curtain around the air riser 52, thereby increasing the contact area between the flue gas and the absorption liquid, improving the absorption amount and absorption efficiency of sulfur dioxide, and can also reabsorb the decomposed ammonia into the absorption liquid to reduce the amount of ammonia escape.

[0083] As an embodiment, the ratio of the diameter of the cover plate 51 to the diameter of the air cylinder 52 is (1.1-1.4): 1. This setting can control the diameter of the annular water curtain, so that the absorption amount and absorption efficiency of sulfur dioxide are maximized. If the ratio of the diameter of the cover plate 51 to the diameter of the air cylinder 52 is less than 1.1: 1, the diameter of the annular water curtain is too small, the contact area between the flue gas and the absorption liquid is reduced, and the absorption of sulfur dioxide is reduced; if the ratio of the diameter of the cover plate 51 to the diameter of the air cylinder 52 is greater than 1.4: 1, the size of the annular water curtain is too large, and there may be a gap in the annular water curtain at the same absorption liquid spraying speed, causing the flue gas to rise and flow away without contacting the absorption liquid, and also reducing the absorption of sulfur dioxide and a small amount of decomposed ammonia.

[0084] As an embodiment, a baffle 56 is provided around the cover plate 51, the top surface of the baffle 56 is higher than the top surface of the cover plate 51, and the bottom surface of the baffle 56 is lower than the bottom surface of the cover plate 51. The annular baffle 56 can store and buffer the absorption liquid, facilitate the formation of an annular water curtain, and prevent the flue gas from flowing away quickly directly from the top of the air outlet 54, increase the residence time of the flue gas at the air lift cap 50, and thus synergistically improve the absorption of sulfur dioxide in the flue gas.

[0085] As a preferred embodiment, the distance between the top surface of the baffle 56 and the top surface of the cover plate 51 is 5-30 mm, and the distance between the bottom surface of the baffle 56 and the bottom surface of the cover plate 51 is 5-30 mm. This arrangement can not only improve the absorption of sulfur dioxide and partially decomposed ammonia, but also will not reduce the overall flue gas treatment efficiency, thereby improving the reliability of the desulfurization system and desulfurization method.

[0086] As an embodiment, the first spray mechanism 132 and the second spray mechanism 122 both include a plurality of circular brackets, each circular bracket of the second spray mechanism 122 is provided with a plurality of three-layer spiral cone nozzles 60, and the three-layer spiral cone nozzles 60 are evenly distributed in the longitudinal and transverse directions, and each circular bracket of the first spray mechanism 132 is provided with a plurality of volute nozzles 61, and the volute nozzles 61 are also evenly distributed in the longitudinal and transverse directions.

[0087] The three-layer spiral cone nozzle 60 is evenly distributed with the circular bracket to achieve uniform spraying of the liquid in the concentration and cooling section 13 and the absorption section 12, thereby increasing the contact area between the flue gas and the liquid in the two sections and improving the absorption efficiency. The three-layer spiral cone nozzle 60 can spray three layers of liquid film, and the single-layer spray coverage rate reaches 150-200%. The flue gas passes through the three layers of liquid film, which can make the gas and liquid fully contact and cause absorption reaction, greatly improving the absorption efficiency of sulfur dioxide, and can reabsorb part of the decomposed ammonia, further preventing the escape of ammonia.

[0088] As an implementation mode, the distance between the three-layer spiral cone nozzle 60 and the volute nozzle 61 on the outermost circular bracket and the wall of the desulfurization tower 10 is 700-1200 mm. This setting can improve the spray coverage rate, and at the same time, it is convenient for operators to install and repair the three-layer spiral cone nozzle 60 and the volute nozzle 61, and secondly, it reduces the contact area between the spray liquid and the wall of the desulfurization tower 10, reduces the corrosion of the wall of the desulfurization tower 10, and improves the service life and safety of the desulfurization system.

[0089] As an implementation manner, there are 1-2 first packing layers 121, and the height of each first packing layer 121 is 400-600 mm; there is 1 second packing layer 113, and the height is 400-450 mm.

[0090] A first filler layer 121 is provided in the absorption section 12, which can redistribute the flue gas, thereby increasing the contact area and contact uniformity between the absorption liquid and the flue gas in the absorption section 12, improving the absorption amount of sulfur dioxide in the flue gas, and intercepting and reabsorbing the decomposed ammonia, thereby fundamentally reducing ammonia escape.

[0091] A second packing layer 113 is provided in the purification section 11, which can also redistribute the flue gas in the purification section 11, thereby increasing the contact area and uniformity between the flue gas and the water washing liquid, and can intercept the residual ammonia gas again, thereby cooperating with the first packing layer 121 of the absorption section 12 to play a double role in significantly reducing ammonia escape.

[0092] As an implementation mode, the first packing layer 121 and the second packing layer 113 are both formed by regular corrugated plates arranged in parallel, the regular corrugated plates have a thickness of 1-2 mm, a spacing of 10-30 mm, and are obtained by extrusion molding of polypropylene.

[0093] The arrangement of the regular corrugated plates can improve the uniformity of the redistribution of the flue gas, thereby achieving the best contact effect between the flue gas and the absorption liquid or the washing liquid.

[0094] Example 2

[0095] This embodiment relates to an ammonia desulfurization method for significantly reducing ammonia slip using the desulfurization system of Example 1, wherein the ratio of the diameter of the cover plate to the diameter of the lift cylinder in the desulfurization system is 1.2:1, the distance between the top surface of the baffle and the top surface of the cover plate is 25 mm, the distance between the bottom surface of the baffle and the bottom surface of the cover plate is 50 mm, and the distance between the three-layer spiral cone nozzle and the volute nozzle on the outermost circular bracket and the desulfurization tower wall is 1000 mm. There is one first packing layer with a height of 600 mm, and one second packing layer with a height of 400 mm. In the first packing layer and the second packing layer, the thickness of the regular corrugated plate is 2 mm and the spacing is 20 mm. The regular corrugated plate is obtained by extrusion molding of modified polypropylene.

[0096] The modified polypropylene composite material comprises 100-120 parts of modified polypropylene, 5-15 parts of 1-hexadecyl-3-methylimidazole nitrate ionic liquid, 10-20 parts of glass fiber, 5-8 parts of heat stabilizer and 5-8 parts of antioxidant. The modified polypropylene is obtained by grafting and modifying polypropylene with olefin monomers having piperazine groups.

[0097] According to the ratio of the modified polypropylene composite material, different modified polypropylene composite materials were obtained, which were named as materials 1#-6# and comparative materials D1#-D3#. The specific differences are as follows:

[0098] Material 1#

[0099] The invention comprises 100 parts of modified polypropylene, 5 parts of 1-hexadecyl-3-methylimidazole nitrate ionic liquid, 10 parts of glass fiber, 5 parts of heat stabilizer and 5 parts of antioxidant, wherein the modified polypropylene is obtained by grafting and modifying polypropylene with 2-vinylpyrazine, and the preparation method of the modified polypropylene is as follows:

[0100] S1: 100 parts of polypropylene by weight were placed in a closed reactor, and nitrogen containing 5 vol% chlorine was introduced for activation treatment at 80°C for 3 hours;

[0101] S2: Exclude chlorine, add 10 parts of 2-vinylpyrazine into the reaction kettle, carry out grafting treatment at 100°C for 5 hours, wash and dry to obtain modified polypropylene.

[0102] Material 2#

[0103] The invention comprises 120 parts of modified polypropylene, 15 parts of 1-hexadecyl-3-methylimidazole nitrate ionic liquid, 20 parts of glass fiber, 8 parts of heat stabilizer and 8 parts of antioxidant, wherein the modified polypropylene is obtained by grafting and modifying polypropylene with 2-vinylpyrazine, and the preparation method of the modified polypropylene is as follows:

[0104] S1: 100 parts of polypropylene by weight were placed in a closed reactor, and nitrogen containing 8 vol% chlorine was introduced for activation treatment at 90°C for 2 hours;

[0105] S2: Exclude chlorine, add 15 parts of 2-vinylpyrazine into the reactor, carry out grafting treatment at 120°C for 3 hours, wash and dry to obtain modified polypropylene.

[0106] Material 3#

[0107] The difference between this material and material 2# is that the olefin monomer with piperazine group is different, and the rest is the same as material 2#. Its specific structural formula is as follows, R1 is tert-butyloxycarbonyl, R2 is H, and R3 is CH2 (n=1), named as monomer 1:

[0108] .

[0109] The preparation method of the monomer 1 is:

[0110] S11: reacting glycidol and 1-tert-butyloxycarbonylpiperazine to obtain a dihydroxy-tert-butyloxycarbonylpiperazine compound;

[0111] S12: Then, dihydroxy tert-butyloxycarbonyl piperazine compound and acryloyl chloride are reacted at 30° C. for 6 hours in the presence of solvent and catalyst pyridine, and then washed and recrystallized to obtain monomer 1. The preparation formula is as follows:

[0112] .

[0113] Material 4#

[0114] The difference between this material and material 3# is that the olefin monomer with piperazine group is different, and the rest is the same as material 3#. Its specific structural formula is as follows, R1 is H, R2 is H, R3 is CH2 (n=1), and it is named as monomer 2:

[0115] .

[0116] The preparation of the monomer 2 is performed after the preparation of the monomer 1 is completed by performing step S13 to obtain:

[0117] S13: Monomer 1 was added to ethyl acetate, the pH was adjusted to 2.5 in an ice bath, and the mixture was reacted at 30°C for 6 hours. Ammonia water was then added dropwise to adjust the pH to 9. After stirring, the mixture was distilled under reduced pressure, and then extracted and recrystallized to obtain monomer 2. The formula for preparing monomer 2 from monomer 1 is as follows:

[0118] . Material 5#

[0119] The difference between this material and material 4# is that methacryloyl chloride is used in step S12, and R2 of the formed olefin monomer with a piperazine group is an alkyl group, and the rest is the same as material 4#.

[0120] Material 6#

[0121] The difference between this material and material 4# is that pentenoyl chloride is used in step S12, R3 is (CH2)3 (n=3), and the rest is the same as material 4#.

[0122] Comparative material D1#

[0123] The difference between this material and material 2# is that styrene is used to replace 2-vinylpyrazine, and the rest is the same as material 2#.

[0124] Comparative material D2#

[0125] The difference between this material and material 2# is that this material does not contain 1-hexadecyl-3-methylimidazole nitrate ionic liquid, and the rest is the same as material 2#.

[0126] Comparative material D3#

[0127] The difference between this material and material 2# is that this material does not contain glass fiber, and the rest is the same as material 2#.

[0128] Test Example 1

[0129] The regular corrugated plates made of the above materials 1#-6# are installed to form the first packing layer and the second packing layer respectively, and the desulfurization system of Example 1 is used to perform flue gas desulfurization operation under the same parameter conditions. The parameter conditions are shown in Table 1. The desulfurization rate, ammonia escape amount, and outlet dust concentration in the flue gas discharged from the outlet of the desulfurization tower are tested. The test period is 1 week, and the regular corrugated plates made of pure polypropylene material in Example 1 are used as a comparison. The test results are shown in Table 2.

[0130] Table 1 Parameter conditions

[0131]

[0132] Table 2 Desulfurization test results

[0133]

[0134] Test Example 2

[0135] In order to verify the durability of the corrugated plate packing prepared by the above materials, the corrugated plate packing prepared by the above materials was placed in flue gas at a high temperature of 130°C for 60 days. The sulfur dioxide content in the flue gas was 5000 mg / Nm 3, observe whether there are cracks on the appearance of the corrugated plate filler and perform the test of Test Example 1 again to detect whether the effects of the first filler layer and the second filler layer on desulfurization and reduction of ammonia escape after high-temperature treatment are reduced. The test results are shown in Table 3.

[0136] Table 3 Corrugated board test results

[0137]

[0138] Since the flue gas temperature in the normal absorption section is lower than 60°C, this test example is treated at 130°C, which is a violent test of the corrugated plate filler. After 60 days of treatment, the desulfurization rate of the corrugated plate filler did not decrease much, and the ammonia escape amount increased slightly, proving that the corrugated plate filler prepared from the modified polypropylene composite material of the present application can be used for a long time in the desulfurization tower, ensuring that the desulfurization system can operate normally for at least 2 years.

[0139] Example 3

[0140] refer to Figure 5 In this embodiment, based on the material 4# of embodiment 2, a layer of hollow absorption membrane 127 is further arranged 200 mm above the first filler layer, and the hollow absorption membrane 127 includes a modified polypropylene fiber membrane and a modified layer arranged on the olefin fiber membrane;

[0141] The modified polypropylene fiber membrane is composed of 70-80 parts of polypropylene, 5-10 parts of polyacrylic acid, 10-25 parts of polyacrylonitrile and 4-5 parts of nano filler by weight, the particle size of the nano filler is 50-80nm, the nano filler is selected from at least one of nano silicon carbide, nano calcium carbonate and nano diamond, the modified polypropylene fiber membrane has a thickness of 60-80μm, an average pore size of 70-75nm and a porosity of 60-70%;

[0142] The modified layer is a copolymer of acrylamide, an olefin monomer with a piperazine group and diethylaminoethyl methacrylate in a weight ratio of 1: (0.1-0.15): (0.1-0.2), and the film thickness of the modified layer is 20-30 μm.

[0143] The preparation method of the hollow absorption film 127 is:

[0144] S11: Blending polypropylene, polyacrylic acid, polyacrylonitrile and nanofiller, extruding to obtain pellets, melt spinning the pellets to obtain primary fibers, stretching the primary fibers to form pores, and treating at 100-110° C. for 200 seconds to obtain a modified polypropylene fiber membrane;

[0145] S12: acrylamide, an olefin monomer having a piperazine group and diethylaminoethyl methacrylate are placed in a solvent and mixed, azobisisobutyronitrile is added, and prepolymerized at 50-70° C. for 2-3 hours to obtain a prepolymer solution;

[0146] S13: coating the prepolymer solution on a modified polypropylene fiber membrane, and then drying at 30-40° C. for 10-15 hours to obtain a film.

[0147] Hollow absorption films 1#-8# and comparative hollow absorption films D1#-D4# were prepared according to the above preparation method. The specific differences are as follows:

[0148] Hollow absorption film 1#

[0149] S11: 80 parts of polypropylene, 10 parts of polyacrylic acid, 25 parts of polyacrylonitrile and 5 parts of nano silicon carbide (particle size of 50nm) are extruded to obtain pellets, and the pellets are melt-spun to obtain primary fibers. The primary fibers are stretched to form pores and then treated at 100°C for 200s to obtain a modified polypropylene fiber membrane. The modified polypropylene fiber membrane has a thickness of 60, an average pore size of 70nm and a porosity of 70%;

[0150] S12: acrylamide, 2-vinylpyrazine and diethylaminoethyl methacrylate in a weight ratio of 1:0.15:0.2 are mixed in a solvent, 1 wt % of azobisisobutyronitrile is added thereto, and prepolymerized at 70° C. for 2 h to obtain a prepolymer solution;

[0151] S13: coating the prepolymer solution on a modified polypropylene fiber membrane, and then drying at 40° C. for 10 h to form a modified layer, wherein the thickness of the modified layer is 20 μm, thereby obtaining a hollow absorption membrane.

[0152] Hollow absorption film 2#

[0153] S11: 70 parts of polypropylene, 5 parts of polyacrylic acid, 10 parts of polyacrylonitrile and 4 parts of nanodiamond (particle size of 80 nm) were extruded to obtain pellets, and the pellets were melt-spun to obtain primary fibers. The primary fibers were stretched to form pores and then treated at 110°C for 200s to obtain modified polypropylene fiber membranes. The modified polypropylene fiber membranes had a thickness of 80 μm, an average pore size of 75 nm and a porosity of 60%;

[0154] S12: acrylamide, 2-vinylpyrazine and diethylaminoethyl methacrylate in a weight ratio of 1:0.1:0.1 are mixed in a solvent, 1 wt % of azobisisobutyronitrile is added thereto, and prepolymerized at 50° C. for 3 h to obtain a prepolymer solution;

[0155] S13: coating the prepolymer solution on a modified polypropylene fiber membrane, and then drying at 30° C. for 15 hours to form a modified layer, the thickness of the modified layer being 30 μm, to obtain a hollow absorption membrane.

[0156] Hollow absorption film 3#

[0157] The difference between the present hollow absorption membrane and the hollow absorption membrane 1# is that the monomer 1 in the material 3# of Example 2 is used to replace 2-vinylpyrazine, and the rest is the same as the hollow absorption membrane 1#.

[0158] Hollow absorption film 4#

[0159] The difference between the present hollow absorption membrane and the hollow absorption membrane 1# is that the monomer 2 in the material 4# of Example 2 is used to replace 2-vinylpyrazine, and the rest is the same as the hollow absorption membrane 1#.

[0160] Hollow absorption film 5#

[0161] The difference between the present hollow absorption film and the hollow absorption film 1# is that the weight ratio of acrylamide, 2-vinylpyrazine and diethylaminoethyl methacrylate is 1:0.2:0.2, and the rest is the same as the hollow absorption film 1#.

[0162] Hollow absorption film 6#

[0163] The difference between this hollow absorbent film and hollow absorbent film 1# is that the thickness of the modified layer formed in step S13 is 10 μm, and the rest is the same as hollow absorbent film 1#.

[0164] Hollow absorption film 7#

[0165] The difference between this hollow absorbent film and hollow absorbent film 1# is that the thickness of the modified layer formed in step S13 is 40 μm, and the rest is the same as hollow absorbent film 1#.

[0166] Hollow absorption film 8#

[0167] The difference between this hollow absorption membrane and hollow absorption membrane 1# is that the membrane thickness of the modified polypropylene fiber membrane is 50 μm, and the rest is the same as hollow absorption membrane 1#.

[0168] Comparison of hollow absorbent film D1#

[0169] The difference between the comparative hollow absorbent film and the hollow absorbent film 1# is that step S11 does not contain polyacrylic acid, and the rest is the same as the hollow absorbent film 1#.

[0170] Comparison of hollow absorbent film D2#

[0171] The difference between the comparative hollow absorbent membrane and the hollow absorbent membrane 1# is that step S11 does not contain polyacrylonitrile, and the rest is the same as the hollow absorbent membrane 1#.

[0172] Comparison of hollow absorbent film D3#

[0173] The difference between the comparative hollow absorbent film and the hollow absorbent film 1# is that the olefin monomer with a piperazine group is not contained in step S12, and the rest is the same as the hollow absorbent film 1#.

[0174] Comparison of hollow absorbent film D4#

[0175] The difference between the comparative hollow absorbent film and the hollow absorbent film 1# is that diethylaminoethyl methacrylate is not contained in step S12, and the rest is the same as the hollow absorbent film 1#.

[0176] Test Example 3

[0177] The desulfurization system formed by material 4# of Example 2 and the desulfurization method of Test Example 1 were named as the control group. On the basis of the control group, hollow absorption membrane 1# was added and named as the experimental group. The amount of ammonia water required for the experimental group to reach the desulfurization rate of the control group (99.7%) was counted, and the ammonia water saving rate of the hollow absorption membrane 1# was calculated. The calculation formula is: (amount of ammonia water used in the control group - amount of ammonia water used in the experimental group) / amount of ammonia water used in the control group × 100.

[0178] The ammonia saving rate of hollow absorption membrane 1# is 42.8%. The results show that the use of the hollow absorption membrane of the present application can greatly reduce the use of ammonia water while maintaining a high desulfurization rate, and can fundamentally reduce the amount of ammonia produced by decomposition, thereby reducing ammonia escape, saving costs while reducing the burden on the environment. It is suitable for large-scale industrial promotion and use, especially for use in large-scale coal-fired power industries, and can significantly reduce the flue gas treatment costs of enterprises.

[0179] Test Example 4

[0180] The hollow absorption membranes prepared in Example 3 were added to the desulfurization tower respectively, and then tested according to the test method of Test Example 1. However, the amount of ammonia water was reduced by 50% compared with Test Example 1, and the other parameter conditions were the same as those in Table 1. The desulfurization rate, ammonia escape amount, and outlet dust concentration in the flue gas discharged from the outlet of the desulfurization tower were tested. The test period was 1 week, and the test results are shown in Table 4.

[0181] Table 4 Hollow absorption film test results

[0182]

[0183] According to the data in Table 4, the desulfurization method combining membrane absorption and ammonia desulfurization with the addition of hollow absorption membrane can maintain a desulfurization rate of more than 98.9% when the amount of ammonia water is reduced by 50%, thus significantly reducing the cost of flue gas treatment. In addition, due to the reduction in the amount of ammonia water, the amount of ammonia generated during the desulfurization process can be fundamentally reduced, thereby further reducing ammonia escape and reducing the pollution of flue gas to the environment.

[0184] During the test, although the hollow absorption membrane 7# has a high desulfurization rate and reduces the effect of ammonia escape, the modified layer is too thick, which reduces the amount of flue gas passing through the hollow absorption membrane, resulting in the gas pressure in the desulfurization tower being higher than that of other central fiber membrane desulfurization systems. From the perspective of long-term safe operation of the desulfurization tower, the membrane thickness of the modified layer should not exceed 30μm.

[0185] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. An ammonia desulfurization method for significantly reducing ammonia slip, characterized in that: A desulfurization tower for ammonia desulfurization is provided, wherein the desulfurization tower is divided into a demisting section, a purification section, an absorption section, a concentration and cooling section, and an oxidation section from top to bottom, and a flue gas inlet and a liquid discharge port are provided on the side wall of the concentration and cooling section, and the steps are as follows: (1) Flue gas enters the concentration and cooling section from the flue gas inlet, and is sprayed and cooled to below 60°C by the first spray mechanism. The concentrated liquid in the concentration and cooling section enters the crystallization tank through the drain port. The upper concentrated liquid in the crystallization tank overflows into the concentration circulation tank. The concentration pump then sends the liquid in the concentration circulation tank into the concentration and cooling section for spraying. When the solid content in the crystallization tank reaches the first threshold, the material at the bottom of the crystallization tank is transported to the ammonium sulfate product processing mechanism; (2) The flue gas then rises to the absorption section and passes through the first packing layer, the second spray mechanism and the first-stage demister for defogger before entering the purification section. The liquid in the absorption section re-enters the oxidation section through the reflux pipe; (3) In the purification section, the flue gas passes through the second packing layer and water washing to capture the entrained ammonium sulfate solution and excess ammonia. After that, it is defogged by the combined demister in the demisting section and then discharged from the desulfurization tower into the chimney. The water washing liquid in the purification section is then returned to the circulating water tank; (4) Compressed air enters the oxidation section to oxidize the absorption liquid refluxed from the absorption section. The liquid formed after full oxidation is then sent to the absorption section for spraying. When the content of ammonium sulfate in the oxidation section reaches the second threshold, a portion of the liquid is sent to the concentration circulation tank; The first packing layer and the second packing layer are both formed by regularly arranged corrugated plates in parallel, the regularly arranged corrugated plates are obtained by extrusion molding of a modified polypropylene composite material, the modified polypropylene composite material comprises 100-120 parts of modified polypropylene, 5-15 parts of 1-hexadecyl-3-methylimidazole nitrate ionic liquid, 10-20 parts of glass fiber, 5-8 parts of a heat stabilizer and 5-8 parts of an antioxidant, and the modified polypropylene is obtained by grafting and modifying polypropylene with an olefin monomer having a piperazine group.

2. The ammonia desulfurization method for significantly reducing ammonia slip according to claim 1, characterized in that: The concentration and cooling section and the absorption section are separated by a first partition plate, and a plurality of evenly distributed gas lifting caps are arranged on the first partition plate; The air lift cap comprises a cover plate, an air lift cylinder and a cone cap from top to bottom. The cross-sectional area of ​​the cover plate is larger than the cross-sectional area of ​​the air lift cylinder. The upper part of the side wall of the air lift cylinder is provided with at least four air outlets, and the lower part of the side wall is provided with at least four air inlet holes.

3. The ammonia desulfurization method for significantly reducing ammonia slip according to claim 2, characterized in that: The ratio of the diameter of the cover plate to the diameter of the lift cylinder is (1.1-1.4):

1.

4. The ammonia desulfurization method for significantly reducing ammonia slip according to claim 3, characterized in that: A baffle is arranged around the cover plate, the top surface of the baffle is higher than the top surface of the cover plate, and the bottom surface of the baffle is lower than the bottom surface of the cover plate.

5. The ammonia desulfurization method for significantly reducing ammonia slip according to claim 1, characterized in that: The first spray mechanism and the second spray mechanism both include a plurality of circular brackets, each circular bracket of the second spray mechanism is provided with a plurality of three-layer spiral cone nozzles, and the three-layer spiral cone nozzles are evenly distributed in the longitudinal and transverse directions, and each circular bracket of the first spray mechanism is provided with a plurality of volute nozzles, and the volute nozzles are evenly distributed in the longitudinal and transverse directions.

6. The ammonia desulfurization method for significantly reducing ammonia slip according to claim 5, characterized in that: The distance between the three-layer spiral cone nozzle and the volute nozzle on the outermost circular bracket and the desulfurization tower wall is 700-1200mm.

7. The ammonia desulfurization method for significantly reducing ammonia slip according to any one of claims 1 to 6, characterized in that: There are 1 to 2 first packing layers, and the height of each first packing layer is 400 to 600 mm; The number of the second packing layer is one and the height is 400-450 mm.

8. The ammonia desulfurization method for significantly reducing ammonia slip according to claim 7, characterized in that: The regular corrugated plate has a thickness of 1-2 mm and a spacing of 10-30 mm.

9. Use of the ammonia desulfurization method for significantly reducing ammonia slip as described in any one of claims 1 to 8 in flue gas desulfurization.

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