Ammonia desulfurization system and process, absorption film of ammonia desulfurization system and preparation method of absorption film

Abstract

The invention discloses an ammonia desulfurization system, an ammonia desulfurization process, an absorption film of the ammonia desulfurization system and a preparation method of the absorption film, and belongs to the technical field of ammonia desulfurization. The ammonia desulfurization system comprises a desulfurization tower, a concentration circulating tank, a crystallization tank, an ammonium sulfate product treatment mechanism and a circulating water tank. According to the ammonia-process desulfurization system, on the basis of membrane absorption and ammonia-process desulfurization, the absorption membrane composed of the first modified layer, the modified polypropylene fiber membrane and the second modified layer is adopted, and the adhesion of the absorption membrane and the modified polypropylene fiber membrane can be improved through the arrangement of the first modified layer and the second modified layer; layering of the absorption film in the use process is avoided, so that the action time of the absorption film in the desulfurization tower is prolonged, long-term efficient desulfurization can be realized, and ammonia escape is reduced.

Description

Technical Field

[0001] The present application relates to an ammonia desulfurization system, process, absorption membrane and preparation method thereof, and belongs to the technical field of 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] Prior art 202411719611.1 discloses an ammonia desulfurization method and its application that significantly reduces ammonia escape. It uses a first filler layer and a hollow absorption membrane in the absorption section of the desulfurization tower to combine membrane absorption and ammonia desulfurization method. In this way, the amount of ammonia water used can be greatly reduced, so ammonia escape can also be reduced from the source. The modified polypropylene fiber membrane used in the hollow absorption membrane is used as the lower layer, and the copolymer of acrylamide, olefin monomer with piperazine group and diethylaminoethyl methacrylate is used as the upper layer, which can promote the hollow absorption membrane to reabsorb the decomposed ammonia gas, reduce ammonia escape, and improve the temperature resistance and durability of the hollow absorption membrane. However, the adhesion of its modified layer to the modified polypropylene fiber membrane is not strong. When used for a long time in the desulfurization tower, there will be a problem of stratification under the impact of gas and the spraying of spray liquid, resulting in gas retention between the separated layers, which will form bubbles. After a long time, the hollow absorption membrane will be broken, and it is difficult to play a long role. Summary of the invention

[0005] In order to solve the above problems, an ammonia desulfurization system is provided. In the ammonia desulfurization system, on the basis of membrane absorption and ammonia desulfurization, an absorption membrane composed of a first modified layer, a modified polypropylene fiber membrane and a second modified layer is adopted. The absorption membrane can improve the adhesion with the modified polypropylene fiber membrane through the arrangement of the first modified layer and the second modified layer, avoid stratification of the absorption membrane during use, thereby increasing the action time of the absorption membrane in the desulfurization tower, and can achieve long-term and efficient desulfurization and reduce ammonia escape.

[0006] According to a first aspect of the present application, an ammonia desulfurization system is provided, comprising a desulfurization tower, a concentration circulation tank, a crystallization tank, an ammonium sulfate product processing mechanism and a circulation water tank; A desulfurization tower, 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, the concentration and cooling section and the absorption section are separated by a first partition, the absorption section and the purification section are separated by a second partition, and the oxidation section and the concentration and cooling section are separated by a third partition; The oxidation section is provided with an air inlet, the side wall of the concentration and cooling section is provided with a flue gas inlet and a liquid discharge port, a first spray mechanism is provided above the concentration and cooling section, the first spray mechanism is connected to a concentration pump, the liquid discharge port is connected to a crystallization tank, and the bottom of the crystallization tank is connected to an ammonium sulfate product processing mechanism through a crystallization pump; A plurality of evenly distributed air lift caps are arranged on the first partition plate, a primary demister, a second spray mechanism, an absorption film and a first packing layer are arranged from top to bottom above the absorption section, the first packing layer is arranged above the air lift cap, the absorption film includes a first modified layer, a modified polypropylene fiber film and a second modified layer from top to bottom, the first modified layer and the second modified layer are prepared from at least acrylamide, an olefin monomer with a piperazine group, diethylaminoethyl methacrylate and modified dopamine, the second spray mechanism is connected to the oxidation section through a circulation pump, and the bottom of the absorption section is connected to the oxidation section through a reflux pipe; The second partition plate is also provided with a plurality of evenly distributed air lift caps. The purification section is provided with a combined demister, a water washing spray mechanism, and a second packing layer in sequence from top to bottom. The second packing layer is arranged above the air lift cap. The water washing spray mechanism is connected to the circulating water tank through a water washing pump. The water washing liquid in the purification section is then returned to the circulating water tank through a water washing reflux pipe.

[0007] Optionally, the thickness of the first modified layer of the absorption film is 15-18 μm, the thickness of the modified polypropylene fiber film is 60-80 μm, and the thickness of the second modified layer is 15-18 μm.

[0008] Optionally, the absorption film has an average pore size of 70-75 nm and a porosity of 60-70%.

[0009] According to a second aspect of the present application, an ammonia desulfurization method is provided, which is carried out using an ammonia desulfurization system as described in any one of the above items, comprising the steps of: (1) The flue gas after dust removal 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 section enters the crystallization tank through the discharge port, and the upper concentrated liquid in the crystallization tank overflows to the concentration circulation tank. The concentration pump then sends the liquid in the concentration circulation tank into the concentration 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, absorption membrane, second spray mechanism and 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 is washed by the water washing spray mechanism to capture ammonium sulfate 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 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.

[0010] According to a third aspect of the present application, a method for preparing an absorption membrane for use with ammonia desulfurization is provided, comprising the steps of: S1: Preparation of modified polypropylene fiber membrane: polypropylene, polyacrylic acid, polyacrylonitrile and nanofiller are blended and extruded to obtain pellets, the pellets are melt-spun to obtain primary fibers, the primary fibers are stretched to form pores and then treated at 100-110° C. for 200 seconds to obtain modified polypropylene fiber membrane; S2: Preparation of the first modified layer: acrylamide, an olefin monomer with a piperazine group, diethylaminoethyl methacrylate and a modified dopamine dispersion are mixed in a solvent, azobisisobutyronitrile and ammonium persulfate are added, and prepolymerization is performed to obtain a first prepolymer liquid, and the first prepolymer liquid is coated on one side of the modified polypropylene fiber membrane, and then irradiated and dried to obtain the first modified layer; S3: Preparation of the second modified layer: acrylamide, an olefin monomer with a piperazine group, diethylaminoethyl methacrylate, and a modified dopamine dispersion are placed in a solvent and mixed, and after adding azobisisobutyronitrile and ammonium persulfate, prepolymerization is performed to obtain a second prepolymer liquid, and the second prepolymer liquid is coated on the other side of the modified polypropylene fiber membrane, followed by irradiation and drying.

[0011] The modified polypropylene fiber membrane of the absorption membrane is used as the middle layer of the absorption membrane. First, it can provide stable support force, and second, it can prolong the residence time of the flue gas entering the absorption membrane, increase the desulfurization amount of the absorption liquid, and then can achieve a higher desulfurization rate on the basis of a lower amount of ammonia water added, which greatly saves the desulfurization cost; the first modified layer and the second 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. The modified polypropylene fiber membrane is blended with polyacrylic acid and polyacrylonitrile, which can promote the reabsorption of decomposed ammonia by the 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 absorption membrane.

[0012] The first modified layer and the second modified layer are arranged above and below the modified polypropylene fiber membrane. Compared with the design of only arranging one modified layer above the modified polypropylene fiber membrane in 202411719611.1, firstly, when the thickness of the modified layer is the same, the original modified layer is designed as two modified layers, which can reduce the thickness of the first modified layer and the second modified layer, thereby shortening the distance between the top surface of the first modified layer and the bottom surface of the second modified layer and the modified polypropylene fiber membrane, increasing the interaction force between the first modified layer and the second modified layer and the modified polypropylene fiber membrane, and thereby improving the adhesion between the layers; secondly, the absorption membrane with a three-layer sandwich design in the present application can achieve three-layer interception and absorption of flue gas, which can further improve the desulfurization rate, reduce ammonia escape, and save the amount of ammonia water.

[0013] In the preparation method of the absorption film, the first modified layer and the second modified layer are bonded to the modified polypropylene fiber film by coating, and the added modified dopamine dispersion can, firstly, improve the adhesion between the first modified layer and the second modified layer, so that during the long-term operation of the desulfurization tower, the three-layer structure of the absorption film will not separate, and the gas will not be retained between the layers, thereby increasing the action time of the absorption film in the desulfurization tower, and can achieve long-term and efficient desulfurization and reduce ammonia escape; secondly, it can synergistically improve the gas throughput of the first modified layer and the second modified layer with diethylaminoethyl methacrylate, and increase the flue gas throughput as much as possible on the basis of ensuring the desulfurization efficiency and reducing ammonia escape, thereby improving the flue gas treatment efficiency.

[0014] Optionally, in terms of weight, in step S1, the polypropylene is 70-80 parts, the polyacrylic acid is 5-10 parts, the polyacrylonitrile is 10-25 parts, and the nanofiller is 4-5 parts.

[0015] Preferably, the nanofiller is selected from at least one of modified nano silicon carbide, modified nano calcium carbonate, modified nano diamond and modified dopamine.

[0016] Optionally, the particle size of the nanofiller is 50-80 nm.

[0017] When the nanofiller is selected from modified dopamine, since the same modified dopamine as that in step S2 and step S3 is added in step S1, the compatibility of the first modified layer and the second modified layer with the modified polypropylene fiber membrane can be increased, thereby further increasing the adhesion of the modified polypropylene fiber membrane to the first modified layer and the second modified layer, thereby extending the service life of the absorption membrane.

[0018] When the nanofiller is selected from modified nano silicon carbide, modified nano calcium carbonate or modified nano diamond, the modified nano silicon carbide, modified nano calcium carbonate or modified nano diamond are all modified with 3-mercaptopropyltrimethoxysilane, and the specific modification method is: Place nano silicon carbide, nano calcium carbonate or nano diamond in an ethanol solution containing 3-mercaptopropyltrimethoxysilane, the weight ratio of nano silicon carbide, modified nano calcium carbonate or modified nano diamond to 3-mercaptopropyltrimethoxysilane is 1: (0.2-0.3), treat at a temperature of 50-70°C for 4-5h, filter and dry.

[0019] Preferably, the concentration of 3-mercaptopropyltrimethoxysilane in the ethanol solution containing 3-mercaptopropyltrimethoxysilane is 20-40 mg / ml.

[0020] The modification method mentioned above modifies nano silicon carbide, nano calcium carbonate or nano diamond to obtain modified nano silicon carbide, modified nano calcium carbonate and modified nano diamond, so that the surface of the nano filler carries 3-mercaptopropyltrimethoxysilane, which has the following advantages: Improving the strength of modified polypropylene fiber membrane: The modified nanofiller has improved dispersibility in the modified polypropylene fiber membrane and increased compatibility with the modified polypropylene fiber membrane. The above two effects can further improve the strength of the absorption membrane, avoid degradation and rupture of the absorption membrane, and extend the service life of the absorption membrane.

[0021] Improving the adhesion between the modified polypropylene fiber membrane and the first modified layer and the second modified layer: The first modified layer and the second modified layer are obtained by coating the first prepolymer liquid and the second prepolymer liquid on the modified polypropylene fiber membrane and drying them respectively. During the drying process, the first prepolymer liquid and the second prepolymer liquid further react to form a cross-linked network. Experimental verification shows that the modification of the nanofiller by 3-mercaptopropyltrimethoxysilane can also increase the adhesion of the modified polypropylene fiber membrane to the first modified layer and the second modified layer; the analysis principle may be: the 3-mercaptopropyltrimethoxysilane carried on the surface of the nanofiller on the surface of the modified polypropylene fiber membrane contains mercapto groups, which can react with the double bonds remaining in the first prepolymer liquid and the second prepolymer liquid, and improve the bonding between the nanofiller on the surface of the modified polypropylene fiber membrane and the first modified layer and the second modified layer, thereby improving the adhesion of the modified polypropylene fiber membrane to the first modified layer and the second modified layer.

[0022] Preferably, the nanofiller is selected from modified silicon carbide and modified dopamine in a weight ratio of 1:1. The above nanofiller can achieve the best adhesion between the first modified layer and the second modified layer and the modified polypropylene fiber membrane, and the absorption membrane will not separate during long-term use. In addition, the above two nanofillers can promote the dispersion of each other, so that the mechanical properties of the modified polypropylene fiber membrane are optimized.

[0023] Optionally, the prepolymerization in step (2) and step (3) is carried out at 50-70°C for 2-3 hours, and the drying is carried out at 30-40°C for 10-15 hours.

[0024] Optionally, in step (2) and step (3), the weight ratio of acrylamide, olefin monomer with piperazine group, diethylaminoethyl methacrylate and modified dopamine dispersion is 1: (0.1-0.15): (0.1-0.2): (0.05-0.08).

[0025] Optionally, the concentration of the modified dopamine dispersion is 10-20 mg / ml.

[0026] In the present application, the first modified layer and the second modified layer use acrylamide as the main body, which can promote the absorption of sulfur dioxide by the modified layer. The olefin monomer with a piperazine group can promote the function of acrylamide and improve the reabsorption rate of decomposed ammonia. However, too many olefin monomers with piperazine groups 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 a piperazine group to increase the reabsorption rate of decomposed ammonia and double reduce ammonia escape.

[0027] The amount of modified dopamine dispersion can coordinate the adhesion of the three-layer interlayer structure of the absorption membrane, the gas throughput of the absorption membrane, the desulfurization efficiency of the absorption membrane and the effect of ammonia escape, so that the above effects can reach the optimal level in coordination. If the amount of modified dopamine dispersion is increased, the content of modified dopamine in the first modified layer and the second modified layer will increase. Although it can further improve the adhesion of the first modified layer and the second modified layer to the modified polypropylene fiber membrane and further reduce the delamination probability of the absorption membrane, it will increase the density of the first modified layer and the second modified layer, increase the resistance of the flue gas, thereby reducing the flue gas treatment efficiency, and also reduce the temperature resistance of the absorption membrane; if the amount of modified dopamine dispersion is reduced, the effect of improving adhesion is not significant, and the production cost is increased, which is not conducive to industrial application.

[0028] Optionally, the preparation method of the modified dopamine is: S10: adding dopamine hydrochloride to sodium borate and sodium bicarbonate and stirring to obtain a dopamine mixed solution; S20: adding acrylic acid to tetrahydrofuran to obtain an acrylic acid solution; S30: adding the acrylic acid solution to the dopamine mixed solution, and adding an alkaline solution to adjust the pH of the reaction solution to ≥ 8, and reacting for more than 12 hours; S40: adding an acidic solution to adjust the pH of the reaction solution until the product precipitates, washing and drying, placing the dried product in a low-temperature plasma generator, ventilating, adjusting the discharge voltage, using radio frequency discharge, and performing plasma treatment to obtain modified dopamine.

[0029] The preparation of the modified dopamine mentioned above allows the modified dopamine to contain double bonds, participate in the reaction, and form a cross-linked network with the remaining substances of the first modified layer and the second modified layer, thereby improving the mechanical properties and temperature resistance of the first modified layer and the second modified layer. In addition, the addition of the modified dopamine can also improve the mechanical properties of the first modified layer and the second modified layer, so even when bubbles appear between the first modified layer or the second modified layer and the modified polypropylene fiber membrane, the rupture of the absorption membrane can be suppressed, and the desulfurization effect on the flue gas can still be maintained.

[0030] According to a fourth aspect of the present application, there is provided an absorption membrane for use in conjunction with ammonia-based desulfurization, which is prepared by the method for preparing an absorption membrane for use in conjunction with ammonia-based desulfurization as described in any one of the above items.

[0031] The beneficial effects of this application include but are not limited to: 1. The ammonia desulfurization system and ammonia desulfurization method of the present application realize efficient desulfurization of flue gas through the synergy of membrane absorption and ammonia desulfurization, and inhibit ammonia escape, and can be operated in a long-term cycle, thereby extending the operation time of the desulfurization system.

[0032] 2. The absorption membrane used in conjunction with ammonia desulfurization in the present application, the arrangement of the first modified layer and the second modified layer can improve the adhesion with the modified polypropylene fiber membrane, and improve the interception and absorption effect of flue gas, further improve the desulfurization rate, reduce ammonia escape, and save the amount of ammonia water.

[0033] 3. The absorbent membrane used in conjunction with ammonia desulfurization of the present application contains modified dopamine in the first modified layer and the second modified layer, which can significantly improve the adhesion with the modified polypropylene fiber membrane, improve the gas throughput, and improve the flue gas treatment efficiency.

[0034] 4. The absorbent membrane used in conjunction with ammonia desulfurization of the present application uses modified nanofillers to prepare modified polypropylene fiber membranes, which can improve the overall mechanical strength of the absorbent membrane, extend its service life, and also improve the adhesion between the three-layer structure of the absorbent membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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: Figure 1 This is a schematic diagram of the structure of the desulfurization system involved in Example 1 of the present application.

[0036] Figure 2 This is a schematic diagram of the structure of the desulfurization tower involved in Example 1 of the present application.

[0037] Figure 3 This is a schematic diagram of the structure of the absorption film involved in Example 1 of the present application.

[0038] List of parts and reference numerals: 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. Absorption membrane; 1271. First modified layer; 1272. Modified polypropylene fiber membrane; 1273. Second modified layer; 13. Concentration Cooling section; 131, flue gas inlet; 132, first spray mechanism; 133, concentration pump; 134, first partition; 14, oxidation section; 141, air inlet; 142, third partition; 20, crystallization tank; 21, crystallization pump; 30, circulating water tank; 40, ammonium sulfide product processing mechanism; 50, air lifting cap; 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

[0039] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0040] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0041] Unless otherwise specified, the methods used in the embodiments of the present application are conventional methods in the prior art.

[0042] Example 1 refer to Figure 1-3This embodiment relates to an ammonia desulfurization system and an ammonia desulfurization method, the ammonia desulfurization system comprises a desulfurization tower 10, a crystallization tank 20, a circulating water tank 30 and an ammonium sulfide 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: 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; 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 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.

[0043] 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.

[0044] The concentration and cooling section 13 and the absorption section 12 are separated by a first partition 134, and a plurality of evenly distributed air lifting caps 50 are arranged on the first partition 134. A primary demister 123, a second spray mechanism 122, an absorption film 127 and a first packing layer 121 are arranged from top to bottom above the absorption section 12. The first packing layer 121 is arranged above the air lifting cap 50. The absorption film includes a first modified layer, a modified polypropylene fiber film and a second modified layer from top to bottom. The first modified layer and the second modified layer are prepared from at least acrylamide, an olefin monomer with a piperazine group, diethylaminoethyl methacrylate and modified dopamine. 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; 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.

[0045] The method of using the desulfurization system is: (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 section enters the crystallization tank 20 through the drain 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 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; (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; (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. (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.

[0046] 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.

[0047] 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 sulfide product processing mechanism 40 and is connected to the crystallization tank 20 through a feed liquid pump 81.

[0048] 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 section for spraying through the concentration pump 133. The liquid treated by the cyclone in the ammonium sulfide 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] As an implementation manner, the number of the first packing layer 121 is one, and the height of the first packing layer 121 is 400-600 mm; the number of the second packing layer 113 is one, and the height of the first packing layer 121 is 400-450 mm.

[0055] 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.

[0056] 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.

[0057] As an implementation manner, the thickness of the first modified layer 1271 of the absorption film 127 is 15-18 μm, the thickness of the modified polypropylene fiber film 1272 is 60-80 μm, and the thickness of the second modified layer 1273 is 15-18 μm.

[0058] As an implementation method, the distance between the absorption film 127 and the first filler layer 121 is 300-350 mm. This distance setting can reserve a retention space for smoke between the absorption film 127 and the first filler layer 121, play a buffering role, avoid damage to the absorption film caused by too much smoke, and can also stabilize the smoke volume when the smoke volume fluctuates, thereby improving the smoke treatment efficiency.

[0059] Example 2 The present embodiment relates to an ammonia desulfurization method carried out by the ammonia desulfurization system of Example 1, wherein the desulfurization system has 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 regular corrugated plate has a thickness of 2 mm and a spacing of 20 mm. The regular corrugated plate is obtained by extrusion molding of polypropylene, and the spacing between the absorption film 127 and the first packing layer is 300 mm.

[0060] The preparation method of modified dopamine in this embodiment refers to Example 1 in patent CN111171213B, which will not be described in detail here.

[0061] The preparation method of the absorption film comprises the steps of: (1) Preparation of modified polypropylene fiber membrane: 70-80 parts of polypropylene, 5-10 parts of polyacrylic acid, 10-25 parts of polyacrylonitrile and 4-5 parts of nanofiller are blended and 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 100-110° C. for 200 seconds to obtain modified polypropylene fiber membrane; (2) Preparation of the first modified layer: acrylamide, an olefin monomer with a piperazine group, diethylaminoethyl methacrylate and a modified dopamine dispersion in a weight ratio of 1: (0.1-0.15): (0.1-0.2): (0.05-0.08) are placed in a solvent and mixed, wherein the concentration of the modified dopamine dispersion is 10-20 mg / ml, azobisisobutyronitrile is added, and prepolymerized at 50-70°C for 2-3 hours to obtain a first prepolymerized liquid, and the first prepolymerized liquid is coated on one side of the modified polypropylene fiber membrane, and then dried at 30-40°C for 10-15 hours to obtain the first prepolymerized liquid; (3) Preparation of the second modified layer: acrylamide, an olefin monomer with a piperazine group, diethylaminoethyl methacrylate, and a modified dopamine dispersion in a weight ratio of 1: (0.1-0.15): (0.1-0.2): (0.05-0.08) are placed in a solvent and mixed. The concentration of the modified dopamine dispersion is 10-20 mg / ml. After adding azobisisobutyronitrile, prepolymerize at 50-70°C for 2-3 hours to obtain a second prepolymer liquid. The second prepolymer liquid is coated on the other side of the modified polypropylene fiber membrane, and then dried at 30-40°C for 10-15 hours.

[0062] According to the above preparation method, absorbent films 1#-8# and comparative absorbent films D1#-D4# were prepared, and the specific differences are as follows: Absorption film 1# (1) Preparation of modified polypropylene fiber membrane: 80 parts of polypropylene, 10 parts of polyacrylic acid, 25 parts of polyacrylonitrile and 5 parts of nano-silicon carbide (particle size of 50 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 100°C for 200 seconds to obtain modified polypropylene fiber membrane. The modified polypropylene fiber membrane had a membrane thickness of 60 μm, an average pore size of 70 nm and a porosity of 70%. (2) Preparation of the first modified layer: acrylamide, 2-vinylpyrazine, diethylaminoethyl methacrylate, and modified dopamine dispersion in a weight ratio of 1:0.15:0.2:0.08 are placed in a solvent and mixed, and the concentration of the modified dopamine dispersion is 20 mg / ml. After adding 0.5 wt% of azobisisobutyronitrile and 0.5 wt% of ammonium persulfate as reactants, prepolymerization is carried out at 70°C for 2 h to obtain a first prepolymer solution, and the first prepolymer solution is coated on one side of the modified polypropylene fiber membrane, and then irradiated under a 150 W ultraviolet lamp for 30 min and dried at 40°C for 10 h to obtain a first modified layer with a thickness of 18 μm; (3) Preparation of the second modified layer: acrylamide, 2-vinylpyrazine, diethylaminoethyl methacrylate and modified dopamine dispersion in a weight ratio of 1:0.15:0.2:0.08 were placed in a solvent and mixed. The concentration of the modified dopamine dispersion was 20 mg / ml. After adding 0.5 wt % of azobisisobutyronitrile and 0.5 wt % of ammonium persulfate as reactants, prepolymerization was carried out at 70°C for 2 h to obtain a second prepolymer liquid. The second prepolymer liquid was coated on the other side of the modified polypropylene fiber membrane. Thereafter, the membrane was irradiated under a 150 W ultraviolet lamp for 30 min and dried at 40°C for 10 h to obtain a second modified layer with a thickness of 18 μm.

[0063] Absorption film 2# (1) Preparation of modified polypropylene fiber membrane: 70 parts of polypropylene, 5 parts of polyacrylic acid, 10 parts of polyacrylonitrile and 4 parts of nanodiamond (particle size 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 membrane. The modified polypropylene fiber membrane had a membrane thickness of 80 μm, an average pore size of 75 nm and a porosity of 60%. (2) Preparation of the first modified layer: acrylamide, 2-vinylpyrazine, diethylaminoethyl methacrylate and modified dopamine dispersion in a weight ratio of 1:0.1:0.1:0.05 are placed in a solvent and mixed, the concentration of the modified dopamine dispersion is 10 mg / ml, 1 wt% of azobisisobutyronitrile is added as a reactant, and prepolymerized at 50°C for 3 h to obtain a first prepolymer liquid, the first prepolymer liquid is coated on one side of the modified polypropylene fiber membrane, and then irradiated under a 150 W ultraviolet lamp for 30 min and dried at 30°C for 15 h to obtain a first modified layer with a thickness of 15 μm; (3) Preparation of the second modified layer: acrylamide, 2-vinylpyrazine, diethylaminoethyl methacrylate and modified dopamine dispersion in a weight ratio of 1:0.1:0.1:0.05 were placed in a solvent and mixed, and the concentration of the modified dopamine dispersion was 10 mg / ml. After adding 1 wt % of azobisisobutyronitrile as a reactant, prepolymerization was carried out at 50°C for 3 h to obtain a second prepolymer liquid. The second prepolymer liquid was coated on the other side of the modified polypropylene fiber membrane, and then irradiated under a 150 W ultraviolet lamp for 30 min and dried at 30°C for 15 h to obtain a second modified layer with a thickness of 15 μm.

[0064] Absorption film 3# The difference between this absorption film and absorption film 1# is that the following compound is used to replace 2-vinylpyrazine, and its specific structural formula is as follows: .

[0065] The preparation method of the compound is: S11: reacting glycidol and 1-tert-butyloxycarbonylpiperazine to obtain a dihydroxy-tert-butyloxycarbonylpiperazine compound; 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: ; The rest is the same as absorption film 1#.

[0066] Absorption film 4# The difference between this absorption film and absorption film 1# is that the weight ratio of acrylamide, 2-vinylpyrazine, diethylaminoethyl methacrylate and modified dopamine dispersion is 1:0.15:0.2:0.02, and the rest is the same as absorption film 1#.

[0067] Absorption film 5# The difference between this absorption film and absorption film 1# is that the weight ratio of acrylamide, 2-vinylpyrazine, diethylaminoethyl methacrylate and modified dopamine dispersion is 1:0.15:0.2:0.1, and the rest is the same as absorption film 1#.

[0068] Absorption film 6# The difference between this absorption film and absorption film 1# is that the concentration of the modified dopamine dispersion is 30 mg / ml, and the rest is the same as absorption film 1#.

[0069] Absorption film 7# The difference between this absorption film and absorption film 1# is that nano silicon carbide is replaced by modified dopamine, and the rest is the same as absorption film 1#.

[0070] Absorption film 8# The difference between this absorption film and absorption film 1# is that nano silicon carbide is replaced by modified dopamine and modified nano silicon carbide in a weight ratio of 1:1. The specific modification method of modified nano silicon carbide is: Place nano-silicon carbide in an ethanol solution containing 3-mercaptopropyltrimethoxysilane, the weight ratio of nano-silicon carbide to 3-mercaptopropyltrimethoxysilane is 1:0.2, the concentration of 3-mercaptopropyltrimethoxysilane in the ethanol solution containing 3-mercaptopropyltrimethoxysilane is 20 mg / ml, treat at 50°C for 5h, filter and dry, and the rest is the same as absorption film 1#.

[0071] Absorption film 9# The difference between this absorption film and absorption film 1# is that the nano silicon carbide is modified nano silicon carbide, and the specific modification method is: Place nano-silicon carbide in an ethanol solution containing 3-mercaptopropyltrimethoxysilane, the weight ratio of nano-silicon carbide to 3-mercaptopropyltrimethoxysilane is 1:0.3, the concentration of modified dopamine in the ethanol solution containing 3-mercaptopropyltrimethoxysilane is 40 mg / ml, treat at 70°C for 4 hours, filter and dry, and the rest is the same as absorption film 1#.

[0072] Comparison of absorption film D1# The difference between this comparative absorption film and absorption film 1# is that dopamine dispersion liquid is used in the preparation of the first modified layer instead of modified dopamine dispersion liquid, and the rest is the same as absorption film 1#.

[0073] Comparative absorption film D2# The difference between this comparative absorption film and absorption film 1# is that the preparation of the second modified layer does not contain modified dopamine dispersion, and the rest is the same as absorption film 1#.

[0074] Comparative absorption film D3# The difference between this comparative absorption film and absorption film 1# is that in the preparation of the first modified layer and the second modified layer, acrylic acid and dopamine in a weight ratio of 1:1 are used to replace the modified dopamine dispersion, and the rest is the same as absorption film 1#.

[0075] Comparison absorption film D4# It is prepared by the preparation method of hollow absorption membrane 1# in patent 202411719611.1.

[0076] Test Example 1 The ammonia desulfurization system of Example 1 was used to carry out flue gas desulfurization operation under the same parameter conditions. The parameter conditions are shown in Table 1. The desulfurization rate and ammonia escape amount in the flue gas discharged from the desulfurization tower outlet were tested under the same ammonia water dosage. The test period was 1 week. The test results are shown in Table 2.

[0077] The ammonia desulfurization system and desulfurization method without an absorption membrane are named the control group. On the basis of the control group, the absorption membrane prepared in Example 2 is added as the experimental group. The amount of ammonia water required when the desulfurization rate of the experimental group and the control group is the same (99%) is counted, and the ammonia water saving rate of each absorption membrane is 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.

[0078] Table 1

[0079] Table 2

[0080] According to the test results in Table 2, the above-mentioned absorption membrane can achieve a desulfurization rate of more than 98%, and the ammonia saving rate can be saved by more than 43.0% compared with the control group, which can significantly reduce the desulfurization cost while ensuring the desulfurization rate. In addition, the amount of ammonia used in this test example is reduced, and the comparison absorption membrane D1# is reduced compared with the test data in the 202411719611.1 patent.

[0081] Test Example 2 The absorption film prepared in Example 2 was placed in flue gas at 60°C for 60 days. The sulfur dioxide content in the flue gas was 5000 mg / Nm 3 During this period, the amount of ammonia used was 2.1m 3 / h, and then immerse the absorption membrane in ammonia water at 130°C for 30 days to observe whether the absorption membrane is stratified, and then perform the test of Test Example 1. After running for one week, check whether the absorption membrane has cracks or ruptures. The presence of ruptures indicates that the adhesion between the layers is weak during the desulfurization process, resulting in gas bubbling in the layers, causing cracks or ruptures. The absorption membrane after the above-mentioned destructive high-temperature treatment is tested to see whether its effect on desulfurization and reduction of ammonia escape is reduced. The test results are shown in Table 3.

[0082] Table 3

[0083] In Table 3 above, due to the stratification of the absorption membrane 4# and the comparison absorption membranes D1#-D4#, they will break during operation and the desulfurization system cannot continue to operate. Therefore, the desulfurization rate and ammonia escape amount cannot be detected normally.

[0084] 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 system, characterized in that: It includes a desulfurization tower, a concentration circulation tank, a crystallization tank, an ammonium sulfate product processing mechanism and a circulating water tank; A desulfurization tower, 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, the concentration and cooling section and the absorption section are separated by a first partition, the absorption section and the purification section are separated by a second partition, and the oxidation section and the concentration and cooling section are separated by a third partition; The oxidation section is provided with an air inlet, the side wall of the concentration and cooling section is provided with a flue gas inlet and a liquid discharge port, a first spray mechanism is provided above the concentration and cooling section, the first spray mechanism is connected to a concentration pump, the liquid discharge port is connected to a crystallization tank, and the bottom of the crystallization tank is connected to an ammonium sulfate product processing mechanism through a crystallization pump; A plurality of evenly distributed air lift caps are arranged on the first partition plate, a primary demister, a second spray mechanism, an absorption film and a first packing layer are arranged from top to bottom above the absorption section, the first packing layer is arranged above the air lift cap, the absorption film includes a first modified layer, a modified polypropylene fiber film and a second modified layer from top to bottom, the first modified layer and the second modified layer are prepared from at least acrylamide, an olefin monomer with a piperazine group, diethylaminoethyl methacrylate and modified dopamine, the second spray mechanism is connected to the oxidation section through a circulation pump, and the bottom of the absorption section is connected to the oxidation section through a reflux pipe; The second partition plate is also provided with a plurality of evenly distributed air lift caps. The purification section is provided with a combined demister, a water washing spray mechanism, and a second packing layer in sequence from top to bottom. The second packing layer is arranged above the air lift cap. The water washing spray mechanism is connected to the circulating water tank through a water washing pump. The water washing liquid in the purification section is then returned to the circulating water tank through a water washing reflux pipe.

2. The ammonia desulfurization system according to claim 1, characterized in that: The thickness of the first modified layer of the absorption film is 15-18 μm, the thickness of the modified polypropylene fiber film is 60-80 μm, and the thickness of the second modified layer is 15-18 μm.

3. An ammonia desulfurization method, characterized in that: The method is carried out using an ammonia desulfurization system as claimed in any one of claims 1 or 2, comprising the steps of: (1) The flue gas after dust removal 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 section enters the crystallization tank through the discharge port, and the upper concentrated liquid in the crystallization tank overflows to the concentration circulation tank. The concentration pump then sends the liquid in the concentration circulation tank into the concentration 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, absorption membrane, second spray mechanism and 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 is washed by the water washing spray mechanism to capture ammonium sulfate 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 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.

4. A method for preparing an absorption membrane for use with ammonia desulfurization, characterized in that: Includes steps: S1: Preparation of modified polypropylene fiber membrane: polypropylene, polyacrylic acid, polyacrylonitrile and nanofiller are blended and extruded to obtain pellets, the pellets are melt-spun to obtain primary fibers, the primary fibers are stretched to form pores and then treated at 100-110° C. for 200 seconds to obtain modified polypropylene fiber membrane; S2: Preparation of the first modified layer: acrylamide, an olefin monomer with a piperazine group, diethylaminoethyl methacrylate and a modified dopamine dispersion are mixed in a solvent, azobisisobutyronitrile and ammonium persulfate are added, and prepolymerization is performed to obtain a first prepolymer liquid, and the first prepolymer liquid is coated on one side of the modified polypropylene fiber membrane, and then irradiated and dried to obtain the first modified layer; S3: Preparation of the second modified layer: acrylamide, an olefin monomer with a piperazine group, diethylaminoethyl methacrylate, and a modified dopamine dispersion are placed in a solvent and mixed, and after adding azobisisobutyronitrile and ammonium persulfate, prepolymerization is performed to obtain a second prepolymer liquid, and the second prepolymer liquid is coated on the other side of the modified polypropylene fiber membrane, followed by irradiation and drying.

5. The method for preparing an absorption membrane for use with ammonia desulfurization according to claim 4, characterized in that: In terms of weight, in step S1, the polypropylene is 70-80 parts, the polyacrylic acid is 5-10 parts, the polyacrylonitrile is 10-25 parts, and the nano filler is 4-5 parts.

6. The method for preparing an absorption membrane for use with ammonia desulfurization according to claim 4, characterized in that: The prepolymerization in step S2 and step S3 is carried out at 50-70° C. for 2-3 hours, and the drying is carried out at 30-40° C. for 10-15 hours.

7. The method for preparing an absorption membrane for use with ammonia desulfurization according to claim 4, characterized in that: The weight ratio of acrylamide, olefin monomer with piperazine group, diethylaminoethyl methacrylate and modified dopamine dispersion in step S2 and step S3 is 1: (0.1-0.15): (0.1-0.2): (0.05-0.08).

8. The method for preparing an absorption membrane for use with ammonia desulfurization according to claim 7, characterized in that: The concentration of the modified dopamine dispersion is 10-20 mg / ml.

9. The method for preparing an absorption membrane for use with ammonia desulfurization according to claim 4, characterized in that: The preparation method of the modified dopamine is: S10: adding dopamine hydrochloride to sodium borate and sodium bicarbonate and stirring to obtain a dopamine mixed solution; S20: adding acrylic acid to tetrahydrofuran to obtain an acrylic acid solution; S30: adding the acrylic acid solution to the dopamine mixed solution, and adding an alkaline solution to adjust the pH of the reaction solution to ≥ 8, and reacting for more than 12 hours; S40: adding an acidic solution to adjust the pH of the reaction solution until the product precipitates, washing and drying, placing the dried product in a low-temperature plasma generator, ventilating, adjusting the discharge voltage, using radio frequency discharge, and performing plasma treatment to obtain modified dopamine.

10. The absorption membrane for use in conjunction with ammonia-based desulfurization prepared by the method for preparing the absorption membrane for use in conjunction with ammonia-based desulfurization as described in any one of claims 4 to 9.

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