Composite denitration agent and preparation method thereof

Abstract

This invention relates to the field of flue gas denitrification technology, and proposes a composite denitrification agent and its preparation method. The composite denitrification agent comprises the following raw materials in parts by weight: 8-10 parts polyacrylamide, 5-8 parts polyethyleneimine, 40-50 parts ammonium bicarbonate, 8-12 parts catalyst, 2-3 parts dispersant, 1-2 parts emulsifier, 2-3 parts activator, 1-2 parts penetrant, and 1-2 parts corrosion inhibitor. The polyacrylamide is non-ionic, with a weight-average molecular weight of 5 million to 7 million, and the polyethyleneimine has a weight-average molecular weight of 25,000 to 70,000. This technical solution solves the problem of insufficient denitrification efficiency of composite denitrification agents in related technologies.

Description

Technical Field

[0001] This invention relates to the field of flue gas denitrification technology, specifically to a composite denitrification agent and its preparation method. Background Technology

[0002] Nitrogen oxides are one of the main air pollutants produced during the combustion of various fuels. As one of the causes of acid rain, photochemical smog and ozone layer depletion, they have a certain impact on the ecological environment.

[0003] Traditional denitrification processes generally suffer from drawbacks such as high equipment modification costs, long construction periods, and poor adaptability to operating conditions, making them difficult to meet the denitrification needs of small and medium-sized industrial sites. Furthermore, some denitrification agents have insufficient denitrification efficiency. Insufficient denitrification efficiency will result in NOx emission concentrations failing to meet ultra-low emission limits, leading to environmental penalties, production restrictions, and rectification measures for enterprises. Incompletely removed NOx entering the atmosphere will damage air quality. Moreover, insufficient denitrification efficiency will cause unreacted NOx and byproducts to accumulate in flues and boiler equipment, exacerbating corrosion, blockage, and scaling, reducing equipment operating efficiency, increasing maintenance costs and safety hazards, and shortening equipment lifespan.

[0004] Therefore, it is essential to obtain a composite denitrification agent with high denitrification efficiency. Summary of the Invention

[0005] This invention proposes a composite denitrification agent and its preparation method. The denitrification efficiency of the composite denitrification agent can reach more than 95%, reducing the concentration of nitrogen oxide emissions in industrial flue gas and extending the service life of equipment.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a composite denitrification agent comprising the following components in parts by weight: 8-10 parts of polyacrylamide, 5-8 parts of polyethyleneimine, 40-50 parts of ammonium bicarbonate, 8-12 parts of catalyst, 2-3 parts of dispersant, 1-2 parts of emulsifier, 2-3 parts of activator, 1-2 parts of penetrant, and 1-2 parts of corrosion inhibitor. The polyacrylamide is non-ionic, the polyacrylamide has a weight-average molecular weight of 5 million to 7 million, and the polyethyleneimine has a weight-average molecular weight of 25,000 to 70,000.

[0007] In one embodiment, the catalyst comprises the following raw materials in parts by weight: 15-25 parts manganese source, 10-15 parts rare earth source, 30-40 parts aluminum source, 15-20 parts silicon source, 1.5-3 parts calcium source, and 1.5-3 parts magnesium source.

[0008] In one embodiment, the raw materials for the catalyst satisfy the ratio of (weight parts of the manganese source + weight parts of the rare earth source) / weight parts of the aluminum source = 0.85~0.9.

[0009] In one embodiment, the preparation method of the catalyst includes the following steps: dissolving the manganese source, the rare earth source, the aluminum source, the calcium source and the magnesium source in water to obtain a mixed solution; adjusting the pH of the silicon source to 9-10 to obtain a silicon source dispersion; adding the mixed solution and the silicon source dispersion to an ammonium carbonate solution, co-precipitating, and then aging, washing, drying and calcining to obtain the catalyst.

[0010] In one embodiment, the dispersant comprises one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, sodium dodecyl sulfate, and sodium lignosulfonate.

[0011] In one embodiment, the emulsifier includes one or both of sorbitan monooleate and polyoxyethylene sorbitan monooleate.

[0012] In one embodiment, the activator includes one or more of urea, ammonia, ethylenediamine, and sodium bicarbonate.

[0013] In one embodiment, the penetrant comprises one or both of sodium secondary alkyl sulfonate and nonylphenol polyoxyethylene ether.

[0014] In one embodiment, the corrosion inhibitor includes one or more of sodium molybdate, benzotriazole, and sodium silicate.

[0015] Secondly, the present invention provides a method for preparing the above-mentioned composite denitrification agent, comprising the following steps: S1. The polyacrylamide, polyethyleneimine, ammonium bicarbonate, catalyst, dispersant and corrosion inhibitor are added to water in sequence and mixed evenly to obtain base material A; S2. Mix the emulsifier, the activator and the penetrant to obtain base material B; S3. Add the base material B to the base material A, and then cut and spray dry to form the composite denitrification agent.

[0016] To improve the denitrification efficiency of composite denitrification agents, this invention employs a compound of polyacrylamide and polyethyleneimine, specifying that the polyacrylamide is non-ionic with a weight-average molecular weight of 5 million to 7 million and the polyethyleneimine has a weight-average molecular weight of 25,000 to 70,000. This approach offers the following advantages: Non-ionic polyacrylamide, with its weight-average molecular weight of 5 million to 7 million, possesses excellent adsorption and dispersion properties, effectively dispersing the active components uniformly in the system, preventing agglomeration, and significantly increasing the contact area between the active components and nitrogen oxides in industrial flue gas, thus laying the foundation for efficient denitrification. Meanwhile, polyethyleneimine, with a weight-average molecular weight of 25,000 to 70,000, has abundant amino active groups, actively capturing NOx molecules in flue gas and converting them into water-soluble ammonium salts. The synergistic effect of both enhances the adsorption and conversion capacity of the denitrification agent for nitrogen oxides, accelerates the denitrification reaction rate, and thereby improves the denitrification efficiency of the composite denitrification agent. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Currently, the denitrification agents used in the industrial denitrification field have obvious limitations: On the one hand, some denitrification agents use polymeric dispersants with unreasonable molecular weights, which easily lead to the agglomeration of components such as catalysts and active salts, resulting in insufficient contact area between active components and nitrogen oxides in flue gas, and a slow denitrification reaction rate; on the other hand, most denitrification agents lack efficient nitrogen oxide capturing groups, have limited adsorption and conversion capabilities for NOx, and have poor compatibility between components, making it difficult to form a synergistic effect, ultimately leading to low denitrification efficiency, making it impossible to stably control the concentration of nitrogen oxide emissions in industrial flue gas within the ideal range, and may also increase denitrification costs due to excessively rapid consumption of active components. To address the problems of low denitrification efficiency, poor component compatibility, and easy agglomeration of active components in existing denitrification agents, this invention provides a composite denitrification agent and its preparation method. The core of this invention is the compounding of nonionic polyacrylamide (weight average molecular weight 5 million to 7 million) and polyethyleneimine (weight average molecular weight 25,000 to 70,000), combined with ammonium bicarbonate, a catalyst in a specific ratio, and various auxiliary agents. Through reasonable component combination and preparation process, the components work synergistically, ultimately achieving significant improvements in denitrification efficiency, reduction of nitrogen oxide emission concentration in industrial flue gas, reduction of active component loss, and extension of equipment lifespan, while also improving the economy and stability of the denitrification process.

[0019] Specifically, in order to better understand the technical solution of the present invention, it is described in the following parts.

[0020] Part One This invention provides a composite denitrification agent comprising the following raw materials in parts by weight: 8-10 parts polyacrylamide, 5-8 parts polyethyleneimine, 40-50 parts ammonium bicarbonate, 8-12 parts catalyst, 2-3 parts dispersant, 1-2 parts emulsifier, 2-3 parts activator, 1-2 parts penetrant, and 1-2 parts corrosion inhibitor. The polyacrylamide is non-ionic, with a weight-average molecular weight of 5 million to 7 million, and the polyethyleneimine has a weight-average molecular weight of 25,000 to 70,000.

[0021] In this invention, the raw material of the composite denitrification agent includes 8-10 parts of polyacrylamide, for example, 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, etc., and the ionic type of polyacrylamide is non-ionic, rather than anionic, cationic, or amphoteric. The core reason is that non-ionic polyacrylamide has excellent compatibility and dispersion stability, and will not react adversely with other components in the composite denitrification agent. It can form a stable mixed system with each component, ensuring the stability of the denitrification agent's performance. The weight-average molecular weight of polyacrylamide is 5 million to 7 million. This molecular weight range is compatible with the non-ionic structure, which can further optimize its effect in the denitrification agent. The appropriate molecular chain length can form a uniform dispersion system in aqueous solution, avoiding insufficient dispersion due to excessively short molecular chains or excessively long molecular chains, which can easily lead to entanglement, resulting in increased system viscosity and affecting the denitrification rate of the composite denitrification agent.

[0022] In this invention, the raw materials of the composite denitrification agent include 5 to 8 parts of polyethyleneimine, for example, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, etc. The polyethyleneimine in this ratio can also help improve the stability of the denitrification agent, reduce the loss of active components, and, together with the action of the catalyst, further optimize the denitrification reaction rate, ensuring that the composite denitrification agent can play a stable denitrification role for a long time.

[0023] In this invention, the raw materials of the composite denitrification agent include 40-50 parts of ammonium bicarbonate, for example, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, 47 parts, 48 ​​parts, 49 parts, 50 parts, etc. Ammonium bicarbonate has the characteristics of easy decomposition and stable release of ammonia gas. During the denitrification reaction, ammonium bicarbonate can decompose to produce ammonia gas. Ammonia gas, as the core reactant of the denitrification reaction, can undergo a reduction reaction with nitrogen oxides (NOx) in industrial flue gas, converting NOx into pollution-free nitrogen gas and water, thereby achieving the purpose of reducing the concentration of nitrogen oxide emissions in flue gas.

[0024] In some embodiments of the present invention, the catalyst comprises the following raw materials in parts by weight: 15-25 parts of manganese source, 10-15 parts of rare earth source, 30-40 parts of aluminum source, 15-20 parts of silicon source, 1.5-3 parts of calcium source, and 1.5-3 parts of magnesium source.

[0025] In this invention, the raw materials of the catalyst include 15 to 25 parts of manganese source, for example, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 parts, etc. After calcination, the manganese source can form manganese oxide with high catalytic activity. The manganese oxide can act as an active center to effectively adsorb NOx molecules in industrial flue gas, while promoting the reduction reaction of ammonia source and NOx in the denitrification system, reducing the activation energy of the reaction, accelerating the denitrification reaction rate, and thus significantly improving the denitrification efficiency of the composite denitrification agent.

[0026] In this invention, the raw materials for the catalyst include rare earth sources, such as cerium or lanthanum, preferably cerium. The proportion of rare earth sources is 10 to 15 parts, for example, 10, 11, 12, 13, 14, or 15 parts. Both types of rare earth elements have excellent redox properties and electronic regulation capabilities, which are suitable for the preparation process of the catalyst of this invention and the requirements of denitrification reaction. They are also widely available and economical.

[0027] In this invention, the catalyst raw material includes 30-40 parts of aluminum source, for example, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, etc. After dissolution, co-precipitation and calcination, the aluminum source is transformed into an alumina support with high specific surface area, good pore structure and mechanical strength. As the core component of the alumina support, aluminum can provide a stable loading platform for active components such as manganese source and rare earth source, uniformly disperse the active components on the surface and in the pores of the support, effectively avoid the agglomeration of active components, ensure that the active centers are fully exposed, and provide structural guarantee for the efficient denitrification reaction.

[0028] In this invention, the raw materials of the catalyst include 15 to 20 parts of silicon source, for example, 15, 16, 17, 18, 19, 20 parts, etc. The silicon element will work synergistically with the aluminum element to form an alumina support, further increasing the specific surface area and porosity of the catalyst, optimizing the pore structure, facilitating the rapid diffusion of NOx and ammonia sources in industrial flue gas to the active center, and accelerating the denitrification reaction rate.

[0029] In this invention, the raw materials of the catalyst include 1.5 to 3 parts of calcium source, for example, 1.5 parts, 1.8 parts, 2 parts, 2.3 parts, 2.5 parts, 2.8 parts, 3 parts, etc. Calcium can adjust the surface alkalinity of the catalyst and enhance the catalyst's adsorption capacity for acidic gases.

[0030] In this invention, the catalyst raw materials include 1.5 to 3 parts of magnesium source, for example, 1.5 parts, 1.7 parts, 1.8 parts, 2 parts, 2.3 parts, 2.5 parts, 2.6 parts, 2.8 parts, 3 parts, etc. Magnesium can further optimize the surface alkalinity of the catalyst, and in combination with calcium, enhance the catalyst's adsorption and activation capacity for NOx, thereby helping to improve denitrification efficiency.

[0031] In some embodiments of the present invention, the raw materials of the catalyst satisfy the ratio of (weight parts of manganese source + weight parts of rare earth source) / weight parts of aluminum source = 0.85~0.9. The manganese source, as the core active component, forms manganese oxide after calcination, which is the core active center for the denitrification reaction. The rare earth source, as an auxiliary active component, is used to modify the electronic structure of the manganese oxide and enhance the adsorption and activation capacity of the active center. The alumina support formed by the aluminum source is used to load the above two active components. When the proportions of the three components satisfy the above relationship, the catalytic efficiency of the active center can be maximized, improving the denitrification efficiency of the composite denitrification agent.

[0032] In some embodiments of the present invention, the catalyst preparation method includes the following steps: dissolving a manganese source, a rare earth source, an aluminum source, a calcium source, and a magnesium source in water to obtain a mixed solution; adjusting the pH of a silicon source to 9-10 to obtain a silicon source dispersion; adding the mixed solution and the silicon source dispersion to an ammonium carbonate solution; co-precipitating the mixture; and then aging, washing, drying, and calcining to obtain the catalyst.

[0033] In this invention, the manganese source is manganese nitrate, the rare earth source is cerium nitrate, the aluminum source is aluminum nitrate, the calcium source is calcium nitrate, the magnesium source is magnesium nitrate, and the silicon source is silica sol. The mass ratio of the manganese source, rare earth source, aluminum source, calcium source, and magnesium source to water is 1:3~5, preferably 1:4. The silica sol has a particle size of 10~20nm and a solid content of 20wt%~30wt%. The concentration of the ammonium carbonate solution is 10wt%~15wt%. The mass ratio of the mixed solution and the silicon source dispersion to the ammonium carbonate solution is 1:1.2~1.5, preferably 1:1.5. The aging temperature is 40~50℃, the aging time is 8~12h, the calcination temperature is 450~550℃, preferably 500℃, and the holding time is 4~6h, preferably 5h.

[0034] In some embodiments of the present invention, the dispersant includes one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, sodium dodecyl sulfate, and sodium lignosulfonate, preferably fatty alcohol polyoxyethylene ether.

[0035] In this invention, the dispersant can effectively disperse the solid active components in the composite denitrification agent, avoid agglomeration and clumping, and maximize the exposure area of ​​the active components.

[0036] In some embodiments of the present invention, the emulsifier includes one or two of sorbitan monooleate and polyoxyethylene sorbitan monooleate, preferably sorbitan monooleate. As an important auxiliary component in the composite denitrification agent, the core function of the emulsifier is to improve the emulsification stability of the denitrification agent system, solve the compatibility problem between the lipophilic and hydrophilic components in the system, and ensure uniform mixing of all components.

[0037] In some embodiments of the present invention, the activator includes one or more of urea, ammonia, ethylenediamine, and sodium bicarbonate, preferably urea. Urea can slowly decompose to produce ammonia during the denitrification reaction, forming a synergistic effect with the ammonia released from ammonium bicarbonate, ensuring a continuous and stable supply of ammonia, allowing nitrogen oxides to fully react with the ammonia source and improving denitrification efficiency.

[0038] In some embodiments of the present invention, the penetrant includes one or two of sodium secondary alkyl sulfonate and nonylphenol polyoxyethylene ether, preferably fatty alcohol polyoxyethylene ether. Industrial flue gas contains particulate matter such as dust. If the denitrification agent has poor wettability after injection, droplets easily form on the surface of the particulate matter, preventing sufficient diffusion and resulting in insufficient contact between the denitrification agent and nitrogen oxides, thus affecting denitrification efficiency. The penetrant has excellent surface activity, which can significantly reduce the surface tension of the denitrification agent, allowing it to quickly wet the dust particles in the flue gas and the inner wall of the equipment after injection, preventing droplet aggregation, increasing the contact area between the denitrification agent and the flue gas, and ensuring that nitrogen oxides can fully contact the active components and ammonia source in the denitrification agent, thereby improving denitrification efficiency.

[0039] In some embodiments of the present invention, the corrosion inhibitor includes one or more of sodium molybdate, benzotriazole, and sodium silicate, preferably benzotriazole. The addition of the corrosion inhibitor can protect the denitrification equipment, inhibit the corrosion of the equipment by the denitrification agent, extend the service life of the equipment, and at the same time prevent corrosion products from affecting the performance of the denitrification agent.

[0040] Part Two This invention also provides a method for preparing a composite denitrification agent, comprising the following steps: S1. Polyacrylamide, polyethyleneimine, ammonium bicarbonate, catalyst, dispersant and corrosion inhibitor are added to water in sequence and mixed evenly to obtain base material A; S2. Mix the emulsifier, activator and penetrant to obtain base material B; S3. Add base material B to base material A, and then cut and spray dry to form a composite denitrification agent.

[0041] In this invention, the mass ratio of polyacrylamide, polyethyleneimine, ammonium bicarbonate, catalyst, dispersant, and corrosion inhibitor to water is 1:4~6, preferably 1:5; the shear rate is 3000~5000 r / min, preferably 5000 r / min; and the shearing time is 20~30 min, preferably 30 min.

[0042] In the following examples and comparative examples: Polyacrylamide: Nonionic; Fatty alcohol polyoxyethylene ether: model number AEO-9; Sodium secondary alkyl sulfonate: Model number SAS-60.

[0043] In the following examples and comparative examples, the preparation method of the composite denitrification agent is the same, namely: S1. Polyacrylamide, polyethyleneimine, ammonium bicarbonate, catalyst, fatty alcohol polyoxyethylene ether and benzotriazole are added to water in sequence and mixed evenly. The mass ratio of polyacrylamide, polyethyleneimine, ammonium bicarbonate, catalyst, fatty alcohol polyoxyethylene ether and benzotriazole to water is 1:5 to obtain base material A. S2. Mix sorbitan monooleate, urea and sodium secondary alkyl sulfonate to obtain base material B; S3. Add base material B to base material A, shear at 5000 r / min for 30 min, and then spray dry to form a composite denitrification agent; The raw material composition of the composite denitrification agents in Examples 1-5 and Comparative Examples 1-4 is shown in Table 1: Table 1. Raw material composition of the composite denitrification agents in Examples 1-5 and Comparative Examples 1-4

[0044] The weight-average molecular weights of polyacrylamide and polyethyleneimine in the composite denitrification agents of Examples 1-5 and Comparative Examples 1-4 are shown in Table 2: Table 2. Weight-average molecular weights of polyacrylamide and polyethyleneimine in the composite denitrification agents of Examples 1-5 and Comparative Examples 1-4

[0045] The catalysts in the composite denitrification agents of Examples 1-5 and Comparative Examples 1-4 have the same composition and preparation method, as shown in Table 3: Table 3. Composition and preparation method of catalysts in the composite denitrification agents of Examples 1-5 and Comparative Examples 1-4

[0046] The composite denitrification agents prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to performance tests on their denitrification efficiency. The composite denitrification agents were added to the silo, and the furnace temperature was controlled at approximately 700℃. The denitrification agents were then conveyed to the furnace via pneumatic conveying equipment and thoroughly mixed with NOx-containing flue gas before entering the denitrification reaction zone. The mass ratio of NOx to NOx was 1.5:1. After reacting for 1 second at approximately 700℃, the reacted flue gas was extracted and sent to a nitrogen oxide analyzer. The NOx concentration in the flue gas before and after purification was analyzed to obtain the denitrification efficiency. The test results are shown in Table 4. Table 4 Performance test results of Examples 1-5 and Comparative Examples 1-4

[0047] As shown in Table 4, when the polyacrylamide in the raw materials of the composite denitrification agent is non-ionic and has a weight-average molecular weight of 5 million to 7 million, and the polyethyleneimine has a weight-average molecular weight of 25,000 to 70,000, the denitrification efficiency of the composite denitrification agent can be improved.

[0048] The composition of the catalyst in the composite denitrification agents of Examples 2 and 6-11 is shown in Table 5: Table 5. Composition of catalysts in the composite denitrification agents of Examples 2, 6-11

[0049] In Examples 6-11, except for the catalyst composition which differs from that in Example 2, the other components and preparation process are consistent with those in Example 2. The performance test results of the composite denitrification agents in Examples 2, 6-11 are shown in Table 6. Table 6 Performance test results of the composite denitrification agents in Examples 2, 6-11

[0050] As shown in Table 6, when the catalyst composition in the composite denitrification agent is within the specified range and satisfies (weight parts of manganese source + weight parts of rare earth source) / weight parts of aluminum source = 0.85~0.9, the denitrification efficiency of the composite denitrification agent can be further improved.

[0051] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite denitrification agent, characterized in that, The raw materials include the following components by weight: 8-10 parts polyacrylamide, 5-8 parts polyethyleneimine, 40-50 parts ammonium bicarbonate, 8-12 parts catalyst, 2-3 parts dispersant, 1-2 parts emulsifier, 2-3 parts activator, 1-2 parts penetrant, and 1-2 parts corrosion inhibitor. The polyacrylamide is non-ionic, the weight-average molecular weight of the polyacrylamide is 5 million to 7 million, and the weight-average molecular weight of the polyethyleneimine is 25,000 to 70,000.

2. The composite denitrification agent according to claim 1, characterized in that, The catalyst comprises the following raw materials in parts by weight: 15-25 parts manganese source, 10-15 parts rare earth source, 30-40 parts aluminum source, 15-20 parts silicon source, 1.5-3 parts calcium source, and 1.5-3 parts magnesium source.

3. The composite denitrification agent according to claim 2, characterized in that, The raw materials for the catalyst satisfy the following ratio: (weight parts of the manganese source + weight parts of the rare earth source) / weight parts of the aluminum source = 0.85~0.

9.

4. The composite denitrification agent according to claim 2, characterized in that, The preparation method of the catalyst includes the following steps: dissolving the manganese source, the rare earth source, the aluminum source, the calcium source and the magnesium source in water to obtain a mixed solution; adjusting the pH of the silicon source to 9-10 to obtain a silicon source dispersion; adding the mixed solution and the silicon source dispersion to an ammonium carbonate solution, co-precipitating, and then aging, washing, drying and calcining to obtain the catalyst.

5. The composite denitrification agent according to claim 1, characterized in that, The dispersant includes one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, sodium dodecyl sulfate, and sodium lignosulfonate.

6. The composite denitrification agent according to claim 1, characterized in that, The emulsifier includes one or both of sorbitan monooleate and polyoxyethylene sorbitan monooleate.

7. The composite denitrification agent according to claim 1, characterized in that, The activator includes one or more of urea, ammonia, ethylenediamine, and sodium bicarbonate.

8. The composite denitrification agent according to claim 1, characterized in that, The penetrant includes one or both of sodium secondary alkyl sulfonate and nonylphenol polyoxyethylene ether.

9. The composite denitrification agent according to claim 1, characterized in that, The corrosion inhibitor includes one or more of sodium molybdate, benzotriazole, and sodium silicate.

10. A method for preparing a composite denitrification agent, used to prepare the composite denitrification agent according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. The polyacrylamide, polyethyleneimine, ammonium bicarbonate, catalyst, dispersant and corrosion inhibitor are added to water in sequence and mixed evenly to obtain base material A; S2. Mix the emulsifier, the activator and the penetrant to obtain base material B; S3. Add the base material B to the base material A, and then cut and spray dry to form the composite denitrification agent.

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