A high-temperature resistant polymeric denitrification agent and its preparation method

Abstract

This invention discloses a high-temperature resistant polymeric denitrification agent and its preparation method. The effective components are prepared from the following raw materials: 1-20 parts by weight of a denitrification aid precursor, 1-30 parts by weight of an organic ligand, 10-50 parts by weight of a diisocyanate, 10-40 parts by weight of melamine, and 1-10 parts by weight of an endothermic agent. The polymeric denitrification agent prepared by this method exhibits excellent thermal stability and high denitrification capacity.

Description

Technical Field

[0001] This invention belongs to the field of flue gas denitrification technology, specifically relating to a high-temperature resistant polymeric denitrification agent and its preparation method. Background Technology

[0002] Nitrogen oxides (NOx) are polluting gases produced in various industrial processes such as coal-fired power plants, waste incineration, and cement plants, posing a significant threat to the environment and human health. Flue gas denitrification primarily employs two technologies: Selective Non-Catalytic Reduction (SNCR) and Selective Catalytic Reduction (SCR). While SCR offers high denitrification efficiency, it is not well-suited for industries producing complex flue gas compositions, such as waste incineration.

[0003] SNCR uses ammonia or urea as the denitrification agent, which is relatively inexpensive. However, its denitrification efficiency is not high, and ammonia escape is prone to occur.

[0004] To achieve ultra-clean emissions, a new denitrification process, polymeric denitrification technology (PNCR), has emerged in recent years. However, current polymeric denitrification agents have low denitrification efficiency, decompose rapidly in the combustion furnace, and are prone to ammonia leakage, causing secondary pollution. Alternatively, they may decompose at low temperatures, resulting in ammonia waste. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature resistant polymeric denitrification agent and its preparation method. The polymeric denitrification agent prepared by this method has excellent thermal stability and high denitrification capacity.

[0006] The present invention adopts the following technical solution: a method for preparing a high-temperature resistant polymeric denitrification agent. The high-temperature resistant polymeric denitrification agent is prepared by means of the following raw materials: 1-20 parts by weight of a denitrification aid precursor, 1-30 parts by weight of an organic ligand, 10-50 parts by weight of a diisocyanate, 10-40 parts by weight of melamine, and 1-10 parts by weight of an endothermic agent.

[0007] Furthermore, the precursor of this denitrification aid is one of the nitrates or acetates of iron, cerium, or copper.

[0008] Furthermore, the organic ligand is 2-amino-terephthalic acid.

[0009] Furthermore, the solvent in step one is one or more of DMF, H2O, and C2H5OH.

[0010] Furthermore, the diisocyanate is one or more of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and 4,4-diphenylmethane diisocyanate.

[0011] This invention also discloses a method for preparing the above-mentioned high-temperature resistant polymeric denitrification agent, the method of which is as follows:

[0012] Step 1: Dissolve 1-20 parts by weight of the denitrification aid precursor and 1-30 parts by weight of the organic ligand in a solvent, stir to fully dissolve and mix evenly, then heat at 100-150℃ for 1-20 hours, cool to room temperature, and dry to obtain the denitrification aid.

[0013] Step 2: Add 10-50 parts by weight of diisocyanate to DMF, disperse evenly to obtain diisocyanate solution, and heat the solution to 70-100℃;

[0014] Add 10-40 parts by weight of melamine to DMF to obtain a melamine solution; add 50%-80% by weight of the melamine solution to the heated diisocyanate solution at a feeding rate of 20-50 min, add 1-10 parts by weight of catalyst while stirring, and react at 70-100℃ for 2-4 h; then adjust the temperature to 100-140℃, add the remaining melamine solution at a feeding rate of 20-50 min, react for 2-6 h, add the denitrification aid mentioned in step one, stir and mix thoroughly, and react for another 0.5-2 h to obtain the polymeric denitrification agent;

[0015] Step 3: Pass the polymer denitrification agent from Step 2 through a 30-80 mesh sieve, pour the polymer denitrification agent particles into a fluidized bed for preheating and fluidization treatment, and obtain the fluidized polymer denitrification agent. Spray an endothermic agent onto the surface of the fluidized polymer denitrification agent to form an endothermic layer on the surface of the polymer denitrification agent, and dry it to obtain a high-temperature resistant polymer denitrification agent.

[0016] Further, the process of spraying the heat-absorbing layer is as follows: Take 1-6.5 parts by weight of organic adhesive and 75% anhydrous ethanol to prepare a solution with a mass concentration of 15%-30%. Then take 1-10 parts by weight of heat-absorbing agent, grind and screen 200-300 mesh particles, add them to the solution, disperse them evenly, and then perform atomized spraying through a fluidized bed bottom spraying process to form a heat-absorbing layer on the surface of the polymer denitrification agent.

[0017] Furthermore, the catalyst is triethylamine, triethylenediamine, tetraisobutyl titanate, or dibutyltin dilaurate.

[0018] Furthermore, in step three, the fluidized bed preheating time is 10 minutes, the inlet air temperature is 30-50℃, and the fan frequency is 20-24Hz; during spraying, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10rpm.

[0019] Furthermore, the endothermic agent is one or more of Na2CO3, MgCO3, BaCO3, and CaCO3.

[0020] The beneficial effects of this invention are: 1. In the initial stage of polymerization of the high-temperature resistant polymer denitrifying agent, polymerization is carried out by slowly adding melamine. With the addition of melamine, diisocyanate in the polymerization system begins to react with melamine. Since diisocyanate is in an excess state in the initial stage of polymerization, the three amino groups of melamine can easily participate in the polymerization reaction, and the polymerization reaction is relatively easy. Therefore, the polymerization reaction requires less energy and can be carried out at a lower temperature. As the reaction proceeds gradually, the concentration of diisocyanate in the system decreases, and the reaction becomes more difficult. Therefore, it is necessary to reduce the feeding rate and increase the reaction temperature to increase the degree of polymerization of the system.

[0021] 2. After the primary amino groups on diisocyanate and melamine are polymerized, polyurea groups are generated. On the one hand, the primary amino groups of melamine are protected, preventing them from being released directly at high temperatures. On the other hand, the isocyanate groups are converted into secondary amino groups, which can decompose more active ammonia in the waste incinerator and further increase the denitrification capacity.

[0022] 3. A denitrification aid is prepared by modifying the metal surface with organic ligands. This aid can participate in the polymerization process of the polymeric denitrification agent, promoting its dispersibility and thermal stability. Then, the endothermic agent is combined with the polymeric denitrification agent in a fluidized bed to form granules, facilitating transportation and storage.

[0023] 4. When the high-temperature resistant polymer denitrification agent is put into the waste incinerator for combustion, it will decompose to release reducing carbon atmosphere and NH3. The denitrification aid will produce high-valence metal oxides under the action of O2. The reducing carbon atmosphere can inhibit the oxidation of NH3, and the high-valence metal oxides can react with reducing carbon and NO to promote denitrification.

[0024] 5. After the heat-absorbing agent and denitrifying agent are bonded together to form a heat-absorbing layer through a fluidized bed process, the material is then fed into the waste incinerator. In the area where it is fed, the outer layer of heat-absorbing agent decomposes and absorbs heat, causing a temporary drop in the temperature of the feeding area. The denitrifying agent is then used at a higher temperature. Furthermore, the coating with the heat-absorbing agent allows the denitrifying agent to slowly release ammonia within the furnace. Attached Figure Description

[0025] Figure 1 Thermogravimetric analysis of the high-temperature resistant polymeric denitrification agent prepared in Example 1 with that of Comparative Example 1 and melamine is shown in the figure.

[0026] Figure 2 This is a comparison chart of the high-temperature resistant polymeric denitrification agent prepared in Example 1 and the denitrification agent prepared in Comparative Example 1 and melamine. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0028] This invention discloses a high-temperature resistant polymeric denitrification agent whose effective components are prepared from the following raw materials: 1-20 parts by weight of a denitrification aid precursor, 1-30 parts by weight of an organic ligand, 10-50 parts by weight of a diisocyanate, 10-40 parts by weight of melamine, and 1-10 parts by weight of an endothermic agent.

[0029] The precursors of the above-mentioned denitrification aids are one of the nitrates or acetates of iron, cerium, and copper.

[0030] The organic ligand mentioned above is 2-amino-terephthalic acid.

[0031] The solvent in step one above is one or more of DMF, H2O and C2H5OH.

[0032] The aforementioned diisocyanate is one or more of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and 4,4-diphenylmethane diisocyanate.

[0033] This invention also discloses a method for preparing the above-mentioned high-temperature resistant polymeric denitrification agent, the method of which is as follows:

[0034] Step 1: Dissolve 1-20 parts by weight of the denitrification aid precursor and 1-30 parts by weight of the organic ligand in a solvent, stir to fully dissolve and mix evenly, then heat at 100-150℃ for 1-20 hours, cool to room temperature, and dry to obtain the denitrification aid.

[0035] Step 2: Add 10-50 parts by weight of diisocyanate to DMF, disperse evenly to obtain diisocyanate solution, and heat the solution to 70-100℃;

[0036] Add 10-40 parts by weight of melamine to DMF to obtain a melamine solution; add 50%-80% by weight of the melamine solution to the heated diisocyanate solution at a feeding rate of 20-50 min, add 1-10 parts by weight of catalyst while stirring, and react at 70-100℃ for 2-4 h; then adjust the temperature to 100-140℃, add the remaining melamine solution at a feeding rate of 20-50 min, react for 2-6 h, add the denitrification aid from step one, stir and mix thoroughly, and react for another 0.5-2 h to obtain the polymeric denitrification agent;

[0037] Step 3: Pass the polymer denitrification agent from Step 2 through a 30-80 mesh sieve, pour the polymer denitrification agent particles into a fluidized bed for preheating and fluidization treatment, and obtain the fluidized polymer denitrification agent. Spray an endothermic agent on the surface of the fluidized polymer denitrification agent to form an endothermic layer on the surface of the polymer denitrification agent, and dry it to obtain a high-temperature resistant polymer denitrification agent.

[0038] In step three, the process of spraying the heat-absorbing layer is as follows: Take 1-6.5 parts by weight of organic adhesive and 75% anhydrous ethanol to prepare a solution with a mass concentration of 15%-30%. Then take 1-10 parts by weight of heat-absorbing agent, grind and screen 200-300 mesh particles, add them to the solution, disperse them evenly, and then perform atomized spraying through a fluidized bed bottom spraying process to form a heat-absorbing layer on the surface of the polymer denitrification agent.

[0039] The catalysts mentioned above are triethylamine, triethylenediamine, tetraisobutyl titanate, or dibutyltin dilaurate.

[0040] In step three, the fluidized bed preheating time is 10 min, the inlet air temperature is 30-50℃, and the fan frequency is 20-24 Hz; during spraying, the inlet air temperature is 50-55℃, the fan frequency is 20-24 Hz, the spray pressure is 0.18 MPa, and the peristaltic pump speed is 10 rpm.

[0041] The above-mentioned endothermic agent is one or more of Na2CO3, MgCO3, BaCO3, and CaCO3.

[0042] The high-temperature resistant polymeric denitrification agent prepared by the above-mentioned method comprises the following effective components: 1-20 parts by weight of a denitrification aid precursor, 1-30 parts by weight of an organic ligand, 10-50 parts by weight of a diisocyanate, 10-40 parts by weight of melamine, and 1-10 parts by weight of an endothermic agent.

[0043] The polymeric denitrification agent prepared in this invention decomposes at high temperatures to produce active ammonia during flue gas denitrification in waste incineration. Compared with melamine, because the amino groups on melamine are protected, the active ammonia does not detach in large quantities in a short time, thus greatly improving the denitrification capacity.

[0044] The specific reaction is shown in equation (1):

[0045] CnHmNs+NOx→N2+CO2+H2O (1);

[0046] When the high-temperature resistant polymeric denitrification agent of this invention is added to a waste incinerator, the oxygen content is relatively low, and carbon (C) is usually released in the form of CO and CO2. After high-temperature combustion, metal atoms often detach as high-valence metal oxides, which react with CO released during polymer combustion to increase denitrification capacity. Taking Fe2O3 as an example, Fe2O3 first reacts with CO to produce FeO and CO2, and the FeO produced can react with NO to produce Fe2O3 and N2.

[0047] The specific reactions are shown in equations (2) and (3):

[0048] Fe2O3+CO→FeO+CO2 (2);

[0049] 4FeO + 2NO → 2Fe2O3 + 2N2 (3).

[0050] This invention discloses a high-temperature resistant polymeric denitrification agent. Melamine serves as the core skeleton, with diisocyanate protecting the amino groups of melamine. Metal ions are linked to multiple organic ligands, 2-amino-terephthalic acid, forming a hollow framework structure. This introduces carboxyl and amino groups onto the metal surface, which can react with melamine and diisocyanate, placing Fe, Cu, and Ce metal ions between molecules. During the thermal combustion and decomposition of the denitrification agent, the molecular structure is disrupted. Due to the bonds between the metal ions and melamine and diisocyanate, higher heat absorption is required. Furthermore, the outer endothermic layer requires heat absorption for decomposition, absorbing even more heat to ensure the denitrification agent can operate at higher temperatures. The surface endothermic agent and the bonding bonds slow down the release of amino groups from the denitrification agent, allowing for a more complete reaction with NO and improving the denitrification capacity.

[0051] Fe, Cu, and Ce were modified with 2-amino-terephthalic acid.

[0052] To verify the performance of the high-temperature resistant polymeric denitrification agent in this invention, the following experiments were conducted:

[0053] Example 1

[0054] The preparation method of a high-temperature resistant polymeric denitrification agent in this embodiment is as follows:

[0055] Step 1: First, weigh 20 parts by weight of ferric nitrate and 30 parts by weight of the organic ligand 2-amino-terephthalic acid, dissolve them in 100 parts by weight of C2H5OH, stir for about 60 minutes until fully dissolved and mixed, then heat at 150℃ for 20 hours to obtain the complex ligand. After cooling to room temperature, wash thoroughly, place the washed product in a drying oven and dry to obtain the denitrification aid, then grind for later use. Room temperature refers to 25℃.

[0056] Step 2: First, add 40 parts by weight of hexamethylene diisocyanate to 100 parts by weight of DMF and disperse it evenly to obtain a hexamethylene diisocyanate solution. Then, add it to the reaction vessel, stir and heat to 100°C.

[0057] 20 parts by mass of melamine were added to 450 parts by mass of DMF to uniformly disperse it in the reagent, thus obtaining a melamine solution. 80% by mass of the melamine solution was added to the heated hexamethylene diisocyanate solution at a feeding rate of 50 min. The reaction temperature was 100°C and the stirring rate was 500 r / min. 10 parts by mass of triethylamine were added, and the reaction was allowed to proceed for 4 h. Then, the temperature was adjusted to 120°C, and the remaining melamine solution was added. The reaction was continued for 5.5 h. 6 parts by mass of the denitrification aid from step one were added, and the mixture was stirred and thoroughly mixed. The reaction was allowed to proceed for another 0.5 h. The reaction product was washed with hot water at approximately 80°C, filtered, and dried to obtain a polymeric denitrification agent.

[0058] Step 3: Screen the obtained polymeric denitrification agent (30-80 mesh), then pour it into a fluidized bed for preheating and fluidization treatment. The inlet air temperature is set at 50-55℃, the fan frequency at 20-24Hz, and the feed speed at 15-20 r / min. Then, prepare a 20% solution using 3 parts by weight of starch, 1 part by weight of gum arabic, and 75% ethanol solution. Next, grind and screen 7 parts by weight of Na₂CO₃ (200-300 mesh) and add it to the solution while stirring to ensure uniform dispersion. Then, perform atomized spraying using a fluidized bed bottom spraying process to form a heat-absorbing layer on the surface of the polymeric denitrification agent. After drying, a high-temperature resistant polymeric denitrification agent is obtained. During spraying, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10 rpm.

[0059] Example 2

[0060] The preparation method of a high-temperature resistant polymeric denitrification agent in this embodiment is as follows:

[0061] Step 1: First, weigh 1 part by mass of cerium nitrate and 1 part by mass of the organic ligand 2-amino-terephthalic acid, and dissolve them in 100 parts by mass of DMF. Stir for about 30 minutes until fully dissolved and mixed. Then heat at 100℃ for 1 hour. After cooling to room temperature, the complex ligand is obtained. Wash thoroughly, and then dry the washed product in a drying oven to obtain the denitrification aid. Grind and set aside for later use. Room temperature refers to 25℃.

[0062] Step 2: First, add 10 parts by weight of dicyclohexylmethane diisocyanate to 100 parts by weight of DMF and disperse it evenly to obtain a dicyclohexylmethane diisocyanate solution. Then add it to the reaction vessel, stir and heat to 70°C.

[0063] Ten parts by mass of melamine were added to 450 parts by mass of DMF to uniformly disperse it in the reagent, thus obtaining a melamine solution. 50% by mass of the melamine solution was added to the heated dicyclohexylmethane diisocyanate solution at a feeding rate of 20 min. The reaction temperature was 70°C, and the stirring rate was 200 r / min. One part by mass of triethylenediamine was added, and the reaction was allowed to proceed for 2 h. The temperature was then adjusted to 100°C, and the remaining melamine solution was added, along with two parts by mass of the denitrification aid mentioned in step one. The mixture was stirred and thoroughly mixed, and the reaction continued for another 2 h. The reaction product was washed with hot water at approximately 80°C, filtered, and dried to obtain a polymeric denitrification agent.

[0064] Step 3: Screen the obtained polymeric denitrification agent (30-80 mesh), then pour it into a fluidized bed for preheating and fluidization treatment. The fluidized bed preheating time is 10 minutes, with the inlet air temperature set at 30-50℃ and the fan frequency at 20-24Hz. Then, take 3 parts by weight of starch, 1 part by weight of gum arabic, and 75% ethanol solution to prepare a 20% solution. Next, take 7 parts by weight of Na2CO3, grind and screen it (200-300 mesh), and add it to the above solution while stirring to ensure uniform dispersion. Then, perform atomized spraying using a fluidized bed bottom spraying process. The feed speed is 15-20 r / min, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10 rpm. An endothermic layer is formed on the surface of the polymeric denitrification agent, which is then dried. After drying, a high-temperature resistant polymeric denitrification agent is obtained. During spraying, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10rpm.

[0065] Example 3

[0066] The preparation method of a high-temperature resistant polymeric denitrification agent in this embodiment is as follows:

[0067] Step 1: First, weigh 15 parts by weight of copper nitrate and 15 parts by weight of the organic ligand 2-amino-terephthalic acid, dissolve them in 100 parts by weight of H2O, stir for about 35 minutes until fully dissolved and mixed evenly, then heat at 140℃ for 10 hours. After cooling to room temperature, the complex ligand is obtained. It is then thoroughly washed, and the washed product is dried in a drying oven to obtain the denitrification aid. Finally, it is ground for later use. Room temperature refers to 25℃.

[0068] Step 2: First, add 25 parts by weight of 4,4-diphenylmethane diisocyanate to 100 parts by weight of DMF and disperse it evenly to obtain a 4,4-diphenylmethane diisocyanate solution. Then, add it to the reaction vessel, stir and heat to 80°C.

[0069] 30 parts by weight of melamine were added to 450 parts by weight of DMF and uniformly dispersed in the reagent to obtain a melamine solution. 75% by weight of the melamine solution was added to the heated 4,4-diphenylmethane diisocyanate solution at a feeding rate of 45 min. The reaction temperature was 80°C, and the stirring rate was 400 r / min. 5 parts by weight of tetraisobutyl titanate were added, and the reaction was allowed to proceed for 2.5 h. Then, the temperature was adjusted to 140°C, and the remaining melamine solution was added. The reaction continued for 3 h. Finally, 10 parts by weight of the denitrification aid mentioned in step one were added, and the mixture was stirred and thoroughly mixed. Continue the reaction for 1.5 hours, wash the reaction product with hot water at about 80°C, step three: screen the obtained polymer denitrification agent (30-80 mesh), and then pour it into a fluidized bed for preheating and fluidization treatment, wherein the fluidized bed preheating time is 10 minutes, the inlet air temperature is set to 30-50°C, and the fan frequency is 20-24Hz; then take 3 parts by mass of starch, 1 part by mass of gum arabic, and 75% ethanol solution to prepare a solution with a mass concentration of 20%, then take 7 parts by mass of Na2CO3, grind and screen (200-300 mesh), add it to the above solution while stirring, so that it is evenly dispersed. The polymer denitrifying agent is then atomized and sprayed using a fluidized bed bottom spraying process. The feed speed is 15-20 r / min, the inlet air temperature is 50-55℃, the fan frequency is 20-24 Hz, the spray pressure is 0.18 MPa, and the peristaltic pump speed is 10 rpm. This forms a heat-absorbing layer on the surface of the polymer denitrifying agent, which is then dried. After drying, a high-temperature resistant polymer denitrifying agent is obtained. During spraying, the inlet air temperature is 50-55℃, the fan frequency is 20-24 Hz, the spray pressure is 0.18 MPa, and the peristaltic pump speed is 10 rpm. The agent is then filtered and dried to obtain the polymer denitrifying agent.

[0070] Example 4

[0071] The preparation method of a high-temperature resistant polymeric denitrification agent in this embodiment is as follows:

[0072] Step 1: First, weigh 10 parts by mass of copper acetate and 10 parts by mass of the organic ligand 2-amino-terephthalic acid, and dissolve them in a mixed solvent of 30 parts by mass of H2O and 70 parts by mass of C2H5OH. Stir for about 45 minutes until fully dissolved and mixed evenly. Then heat at 130℃ for 5 hours. After cooling to room temperature, the complex ligand is obtained. Wash thoroughly, and dry the washed product in a drying oven to obtain the denitrification aid. Then grind it for later use. Room temperature refers to 25℃.

[0073] Step 2: First, add 10 parts by weight of hexamethylene diisocyanate and 14 parts by weight of 4,4-diphenylmethane diisocyanate to 100 parts by weight of DMF and disperse them evenly to obtain a solution of hexamethylene diisocyanate and 4,4-diphenylmethane diisocyanate. Then add the solution to the reaction vessel, stir and heat to 75°C.

[0074] 30 parts by mass of melamine were added to 450 parts by mass of DMF to uniformly disperse it in the reagent, thus obtaining a melamine solution. 60% by mass of the melamine solution was added to the heated hexamethylene diisocyanate and 4,4-diphenylmethane diisocyanate solution at a feeding rate of 40 min. The reaction temperature was 75°C, and the stirring rate was 350 r / min. 5 parts by mass of dibutyltin dilaurate were added, and the reaction was allowed to proceed for 2.5 h. Then, the temperature was adjusted to 130°C, and the remaining melamine solution was added. The reaction continued for 3.5 h. 5 parts by mass of the denitrification aid from step one were added, and the mixture was stirred and thoroughly mixed. The reaction continued for 1 h. The reaction product was washed with hot water at approximately 80°C, filtered, and dried to obtain a high-temperature resistant polymeric denitrification agent.

[0075] Step 3: Screen the obtained polymeric denitrification agent (30-80 mesh), then pour it into a fluidized bed for preheating and fluidization treatment. The fluidized bed preheating time is 10 minutes, with the inlet air temperature set at 30-50℃ and the fan frequency at 20-24Hz. Then, take 3 parts by weight of starch, 1 part by weight of gum arabic, and 75% ethanol solution to prepare a 20% solution. Next, take 7 parts by weight of Na2CO3, grind and screen it (200-300 mesh), and add it to the above solution while stirring to ensure uniform dispersion. Then, perform atomized spraying using a fluidized bed bottom spraying process. The feed speed is 15-20 r / min, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10 rpm. An endothermic layer is formed on the surface of the polymeric denitrification agent, which is then dried. After drying, a high-temperature resistant polymeric denitrification agent is obtained. During spraying, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10rpm.

[0076] Example 5

[0077] Step 1: First, weigh 10 parts by mass of cerium acetate and 17 parts by mass of the organic ligand 2-amino-terephthalic acid, and dissolve them in 20 parts by mass of C2H5OH and 80 parts by mass of DMF. Stir for about 35 minutes until fully dissolved and mixed. Then heat at 125℃ for 14 hours. After cooling to room temperature, the complex ligand is obtained. Wash thoroughly, and dry the washed product in a drying oven to obtain the denitrification aid. Then grind it for later use. Room temperature refers to 25℃.

[0078] Step 2: First, add 24 parts by weight of hexamethylene diisocyanate and 26 parts by weight of dicyclohexylmethane diisocyanate to 100 parts by weight of DMF and disperse them evenly to obtain a solution of hexamethylene diisocyanate and dicyclohexylmethane diisocyanate. Then add it to the reaction vessel, stir and heat to 75°C.

[0079] 40 parts by mass of melamine were added to 450 parts by mass of DMF to uniformly disperse it in the reagent, thus obtaining a melamine solution. 66% by mass of the melamine solution was added to the heated hexamethylene diisocyanate and dicyclohexylmethane diisocyanate solution at a feeding rate of 33 min. The reaction temperature was 82℃, and the stirring rate was 450 r / min. 5 parts by mass of dibutyltin dilaurate were added, and the reaction was allowed to proceed for 2.7 h. Then, the temperature was adjusted to 117℃, and the remaining melamine was added. The reaction continued for 3 h. 14 parts by mass of the denitrification aid mentioned in step one were added, and the mixture was stirred and thoroughly mixed. The reaction continued for 1.2 h. The reaction product was washed with hot water at approximately 80℃, filtered, and dried to obtain a polymeric denitrification agent.

[0080] Step 3: Screen the obtained polymeric denitrification agent (30-80 mesh), then pour it into a fluidized bed for preheating and fluidization treatment. The fluidized bed preheating time is 10 minutes, with the inlet air temperature set at 30-50℃ and the fan frequency at 20-24Hz. Then, take 3 parts by weight of starch, 1 part by weight of gum arabic, and 75% ethanol solution to prepare a 20% solution. Next, take 7 parts by weight of Na2CO3, grind and screen it (200-300 mesh), and add it to the above solution while stirring to ensure uniform dispersion. Then, perform atomized spraying using a fluidized bed bottom spraying process. The feed speed is 15-20 r / min, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10 rpm. An endothermic layer is formed on the surface of the polymeric denitrification agent, which is then dried. After drying, a high-temperature resistant polymeric denitrification agent is obtained. During spraying, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10rpm.

[0081] Example 6

[0082] The preparation method of a high-temperature resistant polymeric denitrification agent in this embodiment is as follows:

[0083] Step 1: First, weigh 18 parts by weight of ferric acetate and 12 parts by weight of the organic ligand 2-amino-terephthalic acid, dissolve them in 40 parts by weight of H2O and 60 parts by weight of DMF, stir for about 35 minutes until fully dissolved and mixed evenly, then heat at 120℃ for 14 hours. After cooling to room temperature, the complex ligand is obtained. It is then thoroughly washed, and the washed product is dried in a drying oven to obtain the denitrification aid, which is then ground for later use. Room temperature refers to 25℃.

[0084] Step 2: First, add 10 parts by weight of dicyclohexylmethane diisocyanate and 10 parts by weight of 4,4-diphenylmethane diisocyanate to 100 parts by weight of DMF and disperse them evenly to obtain a solution of dicyclohexylmethane diisocyanate and 4,4-diphenylmethane diisocyanate. Then add the solution to the reaction vessel, stir and heat to 90°C.

[0085] Ten parts by mass of melamine were added to 450 parts by mass of DMF to uniformly disperse it in the reagent, thus obtaining a melamine solution. 70% by mass of the melamine solution was added to a heated solution of dicyclohexylmethane diisocyanate and 4,4-diphenylmethane diisocyanate at a feeding rate of 25 min. The reaction temperature was 90℃, and the stirring rate was 340 r / min. Eight parts by mass of triethylamine were added, and the reaction was allowed to proceed for 2.5 h. The temperature was then adjusted to 120℃, and the remaining melamine solution was added. The reaction continued for 3.5 h. Ten parts by mass of the denitrification aid from step one were added, and the mixture was stirred and thoroughly mixed. The reaction continued for another 0.5 h. The reaction product was washed with hot water at approximately 80℃, filtered, and dried to obtain a high-temperature resistant polymeric denitrification agent.

[0086] Step 3: Screen the obtained polymeric denitrification agent (30-80 mesh), then pour it into a fluidized bed for preheating and fluidization treatment. The fluidized bed preheating time is 10 minutes, with the inlet air temperature set at 30-50℃ and the fan frequency at 20-24Hz. Then, take 3 parts by weight of starch, 1 part by weight of gum arabic, and 75% ethanol solution to prepare a 20% solution. Next, take 7 parts by weight of Na2CO3, grind and screen it (200-300 mesh), and add it to the above solution while stirring to ensure uniform dispersion. Then, perform atomized spraying using a fluidized bed bottom spraying process. The feed speed is 15-20 r / min, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10 rpm. An endothermic layer is formed on the surface of the polymeric denitrification agent, which is then dried. After drying, a high-temperature resistant polymeric denitrification agent is obtained. During spraying, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10rpm.

[0087] Example 7

[0088] The preparation method of a high-temperature resistant polymeric denitrification agent in this embodiment is as follows:

[0089] Step 1: First, weigh 15 parts by mass of cerium nitrate and 25 parts by mass of the organic ligand 2-amino-terephthalic acid, and dissolve them in 30 parts by mass of H2O, 45 parts by mass of DMF, and 25 parts by mass of C2H5OH. Stir for about 40 minutes until fully dissolved and mixed evenly. Then heat at 110℃ for 18 hours. After cooling to room temperature, the complex ligand is obtained. Wash thoroughly, and then dry the washed product in a drying oven to obtain the denitrification aid. Grind and set aside for later use. Room temperature refers to 25℃.

[0090] Step 2: First, add 25 parts by weight of hexamethylene diisocyanate to 100 parts by weight of DMF and disperse it evenly to obtain a 25 parts by weight hexamethylene diisocyanate solution. Then, add it to the reaction vessel, stir and heat to 80°C.

[0091] 25 parts by mass of melamine were added to 450 parts by mass of DMF and uniformly dispersed in the reagent to obtain a melamine solution. 55% by mass of the melamine solution was added to a heated hexamethylene diisocyanate solution at a feeding rate of 30 min. The reaction temperature was 80℃ and the stirring rate was 420 r / min. 10 parts by mass of tetraisobutyl titanate were added, and the reaction was carried out for 3 h. Then, the temperature was adjusted to 125℃, the remaining melamine solution was added, and the reaction was continued for 2 h. 10 parts by mass of the denitrification aid from step one were added, and the mixture was stirred and thoroughly mixed. The reaction was continued for 1.5 h. The reaction product was washed with hot water at about 80℃, filtered, and dried to obtain a polymeric denitrification agent.

[0092] Step 3: Screen the obtained polymeric denitrification agent (30-80 mesh), then pour it into a fluidized bed for preheating and fluidization treatment. The fluidized bed preheating time is 10 minutes, with the inlet air temperature set at 30-50℃ and the fan frequency at 20-24Hz. Then, take 3 parts by weight of starch, 1 part by weight of gum arabic, and 75% ethanol solution to prepare a 20% solution. Next, take 7 parts by weight of Na2CO3, grind and screen it (200-300 mesh), and add it to the above solution while stirring to ensure uniform dispersion. Then, perform atomized spraying using a fluidized bed bottom spraying process. The feed speed is 15-20 r / min, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10 rpm. An endothermic layer is formed on the surface of the polymeric denitrification agent, which is then dried. After drying, a high-temperature resistant polymeric denitrification agent is obtained. During spraying, the inlet air temperature is 50-55℃, the fan frequency is 20-24Hz, the spray pressure is 0.18MPa, and the peristaltic pump speed is 10rpm.

[0093] Comparative Example 1

[0094] Comparative Example 1 is melamine-hexamethylene diisocyanate resin, which is prepared in accordance with Example 1, except that: the denitrification aid prepared in step 1 is not added in step 2, and the surface of the polymer denitrification agent is not coated in step 3.

[0095] The high-temperature resistant polymeric denitrification agent and melamine denitrification agent prepared in the above examples, as well as Comparative Example 1, were evaluated for their denitrification performance in a denitrification performance evaluation device consisting of a fixed-bed reactor and an online analysis device. The concentration of nitrogen oxides in the flue gas was 500 ppm, and the denitrification temperatures were 800℃, 850℃, and 900℃, respectively.

[0096] The test results are shown in Table 1:

[0097] Table 1. Performance test results of high-temperature resistant polymeric denitrification agents and comparative examples.

[0098]

[0099]

[0100] As shown in Table 1, the denitrification capacity is poor when urea or melamine is used directly as a denitrification agent, while the high-temperature resistant polymeric denitrification agent of this invention exhibits excellent denitrification capacity at high temperatures. Examples 1 and Comparative Example 1 demonstrate that adding a denitrification aid and coating the high-temperature resistant polymeric denitrification agent with a heat-absorbing layer effectively increases the denitrification capacity. Within a temperature range of 800-900℃, the denitrification capacity of the high-temperature resistant polymeric denitrification agent of this invention remains stable.

[0101] Thermogravimetric analysis was performed on the high-temperature resistant polymeric denitrifying agent prepared in Example 1, melamine, and Comparative Example 1. Figure 1 As shown, the weight loss temperature (370℃) of the high-temperature resistant polymeric denitrifying agent in Example 1 is significantly increased compared to melamine (300℃), and 17℃ higher than that of Comparative Example 1 (353℃), indicating that the thermal stability of the polymeric denitrifying agent is improved after the action of the denitrifying aid and the heat absorber.

[0102] The denitrification rate is calculated as follows:

[0103] When the same mass of denitrification agent was added, the concentration of nitrogen oxides in the flue gas was 500 ppm, the gas flow rate was 1027 mL / min, and the time interval was 1 s. The calculated denitrification capacities for melamine, melamine-hexamethylene diisocyanate resin, and Example 1 were 1.09 mol / kg, 2.67 mol / kg, and 5.28 mol / kg, respectively. Figure 2 The time for melamine to achieve a denitrification efficiency of over 90% is approximately 58 seconds, the time for melamine-hexamethylene diisocyanate resin to achieve a denitrification efficiency of over 90% is approximately 519 seconds, and the time for Example 1 to achieve a denitrification efficiency of over 90% is approximately 1035 seconds.

Claims

1. A method for preparing a high-temperature resistant polymeric denitrification agent, characterized in that, The preparation method is as follows: Step 1: Dissolve 1-20 parts by weight of the denitrification aid precursor and 1-30 parts by weight of the organic ligand in a solvent, stir to fully dissolve and mix evenly, then heat at 100-150℃ for 1-20 hours, cool to room temperature, and dry to obtain the denitrification aid. Step 2: Add 10-50 parts by weight of diisocyanate to DMF, disperse evenly to obtain diisocyanate solution, and heat the solution to 70-100℃; Add 10-40 parts by weight of melamine to DMF to obtain a melamine solution; add a melamine solution with a mass concentration of 50%-80% to the heated diisocyanate solution at a feeding time of 20-50 minutes, add 1-10 parts by weight of catalyst while stirring, and react at a temperature of 70-100°C for 2-4 hours; then adjust the temperature to 100-140°C, add the remaining melamine solution at a feeding rate of 20-50 minutes, react for 2-6 hours, add the denitrification aid mentioned in step one, stir and mix thoroughly, and react for another 0.5-2 hours to obtain the polymeric denitrification agent; Step 3: Pass the polymer denitrification agent from Step 2 through a 30-80 mesh sieve, pour the polymer denitrification agent particles into a fluidized bed for preheating and fluidization treatment to obtain a fluidized polymer denitrification agent. Spray an endothermic agent onto the surface of the fluidized polymer denitrification agent to form an endothermic layer on the surface of the polymer denitrification agent, and dry it to obtain a high-temperature resistant polymer denitrification agent. The precursor of the denitrification aid is one of the nitrates or acetates of iron, cerium, and copper; the endothermic agent is one or more of Na2CO3, MgCO3, BaCO3, and CaCO3.

2. The method for preparing a high-temperature resistant polymeric denitrification agent according to claim 1, characterized in that, In step three, the process of spraying to form the heat-absorbing layer is as follows: Take 1-6.5 parts by weight of organic adhesive, add 75% ethanol solution to prepare a solution with a mass concentration of 15%-30%, then take 1-10 parts by weight of heat-absorbing agent, grind it through a 200-300 mesh sieve, add it to the solution, disperse it evenly, and then perform atomized spraying through a fluidized bed bottom spraying process to form a heat-absorbing layer on the surface of the polymer denitrification agent.

3. The method for preparing a high-temperature resistant polymeric denitrification agent according to claim 2, characterized in that, The catalyst is triethylamine, triethylenediamine, tetraisobutyl titanate, or dibutyltin dilaurate.

4. The method for preparing a high-temperature resistant polymeric denitrification agent according to claim 3, characterized in that, In step three, the fluidized bed preheating time is 10 min, the inlet air temperature is 30-50℃, and the fan frequency is 20-24 Hz; during spraying, the inlet air temperature is 50-55℃, the fan frequency is 20-24 Hz, the spray pressure is 0.18 MPa, and the peristaltic pump speed is 10 rpm.

5. The method for preparing a high-temperature resistant polymeric denitrification agent according to claim 4, characterized in that, The organic ligand is 2-amino-terephthalic acid.

6. The method for preparing a high-temperature resistant polymeric denitrification agent according to claim 5, characterized in that, The solvent in step one is one or more of DMF, H2O, or C2H5OH.

7. The method for preparing a high-temperature resistant polymeric denitrification agent according to claim 6, characterized in that, The diisocyanate is one or more of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, or 4,4-diphenylmethane diisocyanate.

8. A high-temperature resistant polymeric denitrification agent prepared by the preparation method of a high-temperature resistant polymeric denitrification agent according to any one of claims 1-7.

Images