Selective non-catalytic reduction denitration agent and method for preparing the same

Abstract

The present application belongs to the field of denitration agent preparation, and provides a selective non-catalytic reduction denitration agent and a preparation method thereof. First, urea is heat treated to change hydrogen bond strength and intermolecular force in the crystal, and increase thermal motion of urea molecules, so as to cause loose arrangement between molecules, increase exposure of reaction sites, and increase contact area of molecules, thereby increasing reaction rate. A phosphoric acid group is introduced into the urea after heat treatment, and phosphonated urea is formed through chemical reaction, so as to improve adsorption and reaction activity of the urea. This process helps to enhance the combination ability of urea and NOx, thereby improving the denitration efficiency. Appropriate amounts of sodium carbonate, sodium chloride and hydroxyl iron oxide are added to the reaction system, which helps to promote the activity improvement of the denitration agent, and can effectively deal with nitrogen oxide pollution in industrial waste gas.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of denitration agent preparation and relates to a selective non-catalytic reduction denitration agent and a preparation method thereof. BACKGROUND

[0002] With the rapid development of industrialization, nitrogen oxides (NOx) as a major air pollutant has become an important environmental problem of global concern. NOx not only causes acid rain, ozone layer depletion, but also has a serious impact on human health. Therefore, it is particularly important to control the emission of NOx in industrial flue gas. Traditional denitration technologies mainly include selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR). SCR technology reduces NOx to harmless nitrogen and water under the action of a catalyst, has the advantages of high efficiency, wide applicability, etc., but the implementation cost of the technology is high, and the selectivity and durability of the catalyst also limit its application in certain conditions. In addition, SCR usually requires high operating temperature and additional reducing agent, increasing the process complexity and cost. SNCR is another technology widely used in industrial flue gas denitration. SNCR reduces NOx to nitrogen by spraying reducing agents (such as urea or ammonia) into the flue gas at high temperature. However, the traditional SNCR denitration agent has the problem of insufficient denitration efficiency. Therefore, we need to prepare a selective non-catalytic reduction denitration agent. SUMMARY

[0003] In view of the deficiencies in the prior art, the purpose of the present application is to provide a selective non-catalytic reduction denitration agent. By heat treating urea, the crystal structure of urea is changed and its volatile components are removed, increasing the exposure of reaction sites, the contact surface of the molecule is larger, and the reaction rate is improved. In the heat-treated urea, phosphoric acid groups are introduced, which can improve the nucleophilicity of ammonia and promote its reaction with nitrogen oxides, making it more effective in reacting with NOx to meet the needs of actual production.

[0004] To achieve this purpose, the following technical solutions are adopted in the present application:

[0005] In a first aspect, the present application provides a preparation method of a selective non-catalytic reduction denitration agent, wherein the preparation method is as follows:

[0006] Step S1, urea is vacuum dried at a first temperature, the vacuum-dried urea is heated to a second temperature for heat treatment, and after cooling to room temperature, the urea is dissolved in deionized water, stirred uniformly at a first stirring speed, then phosphoric acid ester is added, heated to a third temperature for sufficient reaction, and after cooling to room temperature, phosphonated urea is obtained;

[0007] Step S2, adding melamine to anhydrous ethanol, heating to a fourth temperature, stirring at a second stirring speed until dissolved, adding an amination reagent, heating to a fifth temperature, and cooling to room temperature after sufficient reaction to obtain amination melamine;

[0008] Step S3: mixing phosphorylated urea, amination melamine, formaldehyde solution and deionized water, adding ammonia solution to adjust the pH of the solution to 8.5-9.0, heating to a fourth temperature, heating in a water bath, adding acetic acid solution to adjust the pH of the solution to 4-5, adjusting to a sixth temperature, heating in a water bath, and vacuum drying at the first temperature after the reaction is completed. After drying, grinding and mixing with sodium chloride, sodium carbonate, carbon powder, hydroxymethyl cellulose and ferric oxyhydroxide to obtain a selective non-catalytic reduction denitrifier.

[0009] During heat treatment, the crystal structure of urea may undergo a phase transition, from a stable crystalline phase (α-urea) to β-urea. Heating causes changes in the strength of hydrogen bonds and intermolecular forces in the crystal, thus affecting the crystal structure. At the same time, during heat treatment, the crystal water in urea may be removed, causing its hydration state to change. This process makes urea more hydrophobic and increases its reactivity. Increased temperature increases the thermal motion of urea molecules, leading to a loosening of the molecular arrangement, increased exposure of reaction sites, and a larger molecular contact surface, thereby increasing the reaction rate.

[0010] Urea exists in the form of α-phase crystals at room temperature, forming a regular three-dimensional lattice. This structure is formed by the interaction of hydrogen bonds, ionic bonds and van der Waals forces. β-urea generally has better solubility, which means that a higher urea concentration can be provided in the reaction system, thereby improving the efficiency of the denitrification reaction. Due to its different crystal structure, the intermolecular interactions of β-urea may be weaker, making it easier to release ammonia in chemical reactions, thereby increasing the reaction rate with nitrogen oxides. β-urea may exhibit better thermal stability at high temperatures, which helps to maintain its denitrification performance under high temperature reaction conditions. Compared with α-urea, β-urea has weaker intermolecular hydrogen bonds and poorer thermal stability. When heated or under appropriate conditions, β-urea can decompose more easily, releasing ammonia to react with nitrogen oxides (NOx). The crystal structure of β-urea makes it easier to mix with other components in a solid state, which helps the uniformity of the reaction and reduces side reactions caused by excessive local concentrations.

[0011] Introducing phosphate groups into β-urea can bring multiple benefits. Phosphate groups can form strong hydrogen bonds with nitrogen oxides, forming stable intermediates. This promotes ammonia release and reaction with NOx, improving denitrification efficiency. Phosphate groups serve as active catalyst centers, accelerating the reaction and increasing the rate of denitrification. The introduction of phosphate groups increases the polarity of urea, improving its solubility in water and thereby increasing the effective concentration of urea in the reaction system. Phosphate groups have multiple hydrogen bond donors and acceptors, allowing them to form stable hydrogen bonding interactions with nitrogen oxides. This hydrogen bonding lowers the activation energy of the reaction, accelerating ammonia release and reaction. The introduction of phosphate groups alters the electronic environment of β-urea, making it a stronger reducing agent and enhancing its reactivity with NOx. It also increases the nucleophilicity of ammonia, promoting its reaction with nitrogen oxides. Phosphate groups may form stable intermediates with the generated ammonia and nitrogen oxides. This process makes the reaction pathway more efficient, reduces the occurrence of side reactions, and thus improves overall denitrification efficiency.

[0012] One of the keys to the SNCR reaction is active groups. At low temperatures, insufficient active groups prevent NOx reduction. FeOOH effectively provides active groups, promoting SNCR denitrification. Carbon not only has a high NOx reduction capacity, but also generates CO in an oxygen-deficient environment, which promotes SNCR denitrification. At high temperatures, carbon also reacts with NH3 to produce HCNO, another reducing agent for SNCR denitrification, thereby increasing the NOx reduction capacity.

[0013] As a preferred technical solution of the present invention, in step S1, the feeding amount of the urea is 50-70g, for example, it can be 50g, 52g, 54g, 56g, 58g, 60g, 62g, 64g, 66g, 68g or 70g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0014] In some optional examples, the first temperature is 60-70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] In some optional examples, the vacuum drying time is 3-5h, for example, it can be 3.0h, 3.2h, 3.4h, 3.6h, 3.8h, 4.0h, 4.2h, 4.4h, 4.6h, 4.8h or 5.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] In some optional examples, the second temperature is 110-120°C, for example, it can be 110°C, 111°C, 112°C, 113°C, 114°C, 115°C, 116°C, 117°C, 118°C, 119°C or 120°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] In some optional examples, the heat treatment time is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] In some optional examples, the volume of the deionized water is 100-130 mL, for example, it can be 100 mL, 103 mL, 106 mL, 109 mL, 112 mL, 115 mL, 118 mL, 121 mL, 124 mL, 127 mL or 130 mL, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0019] In some optional examples, the first stirring speed is 300-400 rpm, for example, it can be 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm or 400 rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] In some optional examples, the feeding amount of the phosphate ester is 30-50g, for example, it can be 30g, 32g, 34g, 36g, 38g, 40g, 42g, 44g, 46g, 48g or 50g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] In some optional examples, the third temperature is 100-120°C, for example, it can be 100°C, 102°C, 104°C, 106°C, 108°C, 110°C, 112°C, 114°C, 116°C, 118°C or 120°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] In some optional examples, the reaction time at the third temperature is 4-6h, for example, it can be 4.0h, 4.2h, 4.4h, 4.6h, 4.8h, 5.0h, 5.2h, 5.5h, 5.6h, 5.8h or 6.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] As a preferred technical solution of the present invention, in step S2, the feeding amount of melamine is 1-1.5g, for example, it can be 1.0g, 1.05g, 1.10g, 1.15g, 1.20g, 1.25g, 1.30g, 1.35g, 1.40g, 1.45g or 1.50g, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] In some optional examples, the volume of the anhydrous ethanol is 100-120 mL, for example, it can be 100 mL, 102 mL, 104 mL, 106 mL, 108 mL, 110 mL, 112 mL, 114 mL, 116 mL, 118 mL or 120 mL, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] In some optional examples, the fourth temperature is 70-80°C, for example, it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] In some optional examples, the second stirring speed is 200-300 rpm, for example, it can be 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm or 300 rpm, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0027] In some optional examples, the amount of the amination reagent is 1-2 g, for example, 1.0 g, 1.1 g, 1.2 g, 1.3 g, 1.4 g, 1.5 g, 1.6 g, 1.7 g, 1.8 g, 1.9 g or 2.0 g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] In some optional examples, the fifth temperature is 80-100°C, for example, it can be 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, 94°C, 96°C, 98°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] In some optional examples, the reaction time at the fifth temperature is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] As a preferred technical solution of the present invention, in step S3, the feeding amount of the phosphorylated urea is 10-15g, for example, it can be 10.0g, 10.5g, 11.0g, 11.5g, 12.0g, 12.5g, 13.0g, 13.5g, 14.0g, 14.5g or 15.0g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] In some optional examples, the feeding amount of the amino melamine is 5-10g, for example, it can be 5.0g, 5.5g, 6.0g, 6.5g, 7.0g, 7.5g, 8.0g, 8.5g, 9.0g, 9.5g or 10.0g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] In some optional examples, the feeding amount of the formaldehyde solution is 30-40g, for example, it can be 30g, 31g, 32g, 33g, 34g, 35g, 36g, 37g, 38g, 39g or 40g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In some optional examples, the mass fraction of the formaldehyde solution is 15-20wt.%, for example, it can be 15.0wt.%, 15.5wt.%, 16.0wt.%, 16.5wt.%, 17.0wt.%, 17.5wt.%, 18.0wt.%, 18.5wt.%, 19.0wt.%, 19.5wt.% or 20.0wt.%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0034] In some optional examples, the amount of deionized water added is 20-30 g, for example, 20 g, 21 g, 22 g, 23 g, 24 g, 25 g, 26 g, 27 g, 28 g, 29 g or 30 g, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0035] In some optional examples, the mass fraction of the ammonia solution is 10-15wt.%, for example, it can be 10.0wt.%, 10.5wt.%, 11.0wt.%, 11.5wt.%, 12.0wt.%, 12.5wt.%, 13.0wt.%, 13.5wt.%, 14.0wt.%, 14.5wt.% or 15.0wt.%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0036] In some optional examples, the pH is adjusted to 8.5-9.0 by adding an aqueous ammonia solution, for example, 8.5, 8.6, 8.7, 8.8, 8.9 or 9.0, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] In some optional examples, the water bath heating time at the fourth temperature is 1-2 hours, for example, it can be 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] In some optional examples, the mass fraction of the acetic acid solution is 10-15 wt.%, for example, it can be 10.0 wt.%, 10.5 wt.%, 11.0 wt.%, 11.5 wt.%, 12.0 wt.%, 12.5 wt.%, 13.0 wt.%, 13.5 wt.%, 14.0 wt.%, 14.5 wt.% or 15.0 wt.%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0039] In some optional examples, the acetic acid solution is added to adjust the pH to 4-5, for example, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9 or 5.0, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In some optional examples, the sixth temperature is 50-55°C, for example, it can be 50.0°C, 50.5°C, 51.0°C, 51.5°C, 52.0°C, 52.5°C, 53.0°C, 53.5°C, 54.0°C, 54.5°C or 55.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] In some optional examples, the water bath heating time at the sixth temperature is 1-2 hours, for example, it can be 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] In some optional examples, the vacuum drying time is 8-10h, for example, it can be 8.0h, 8.2h, 8.4h, 8.6h, 8.8h, 9.0h, 9.2h, 9.4h, 9.6h, 9.8h or 10.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In some optional examples, the amount of sodium chloride added is 2-3 g, for example, 2.0 g, 2.1 g, 2.2 g, 2.3 g, 2.4 g, 2.5 g, 2.6 g, 2.7 g, 2.8 g, 2.9 g or 3.0 g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In some optional examples, the amount of sodium carbonate added is 1-2 g, for example, 1.0 g, 1.1 g, 1.2 g, 1.3 g, 1.4 g, 1.5 g, 1.6 g, 1.7 g, 1.8 g, 1.9 g or 2.0 g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] In some optional examples, the amount of carbon powder added is 1-2g, for example, it can be 1.0g, 1.1g, 1.2g, 1.3g, 1.4g, 1.5g, 1.6g, 1.7g, 1.8g, 1.9g or 2.0g, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In some optional examples, the feeding amount of the hydroxymethyl cellulose is 2-3 g, for example, it can be 2.0 g, 2.1 g, 2.2.g, 2.3 g, 2.4 g, 2.5 g, 2.6 g, 2.7 g, 2.8 g, 2.9 g or 3.0 g, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] In some optional examples, the feeding amount of the ferric oxyhydroxide is 2-3 g, for example, it can be 2.0 g, 2.1 g, 2.2.g, 2.3 g, 2.4 g, 2.5 g, 2.6 g, 2.7 g, 2.8 g, 2.9 g or 3.0 g, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] In a second aspect, the present invention provides a selective non-catalytic reduction denitrifier prepared according to the preparation method described in the first aspect.

[0049] Compared with the prior art, the present invention has the following beneficial effects: (1) by subjecting urea to heat treatment, it is transformed from a stable crystalline phase (α-urea) to β-urea, thereby increasing its reaction activity; at the same time, the increase in temperature increases the thermal motion of urea molecules, resulting in a loose arrangement between molecules, increasing the exposure of reaction sites, and increasing the contact surface of the molecules, thereby increasing the reaction rate; (2) the phosphate group can serve as the active center of the catalyst, promoting the reaction and increasing the rate of the denitrification reaction. The introduction of the phosphate group can increase the effective concentration of urea in the reaction system. The phosphate group has multiple hydrogen bond donors and acceptors, and can form stable hydrogen bond interactions with nitrogen oxides, which can reduce the reaction activation energy, thereby accelerating the release and reaction of ammonia, enhancing its reaction activity with NOx, and improving the denitrification efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A flow chart of a method for preparing a selective non-catalytic reduction denitrifier provided in Examples 1-8 of the present invention;

[0051] Figure 2 TEM image of urea after heat treatment in Example 1 of the present invention (scale: 50 nm);

[0052] Figure 3 TEM image of urea after heat treatment in Example 1 of the present invention (scale: 20 nm). DETAILED DESCRIPTION

[0053] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be understood as limiting the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt obvious other technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments described herein.

[0054] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products, and their brands, specifications and manufacturer information are as follows:

[0055] Urea, nitrogen content ≥46%, Hebei Guanghui Industrial Co., Ltd.;

[0056] Diethyl phosphate, purity ≥98%, Shanghai Haohong Biopharmaceutical Technology Co., Ltd.;

[0057] Melamine, purity ≥46%, Jingzhou Yinjie Chemical Co., Ltd.;

[0058] Anhydrous ethanol, purity ≥99%, Xi'an Sanpu Chemical Reagent Co., Ltd.;

[0059] Diethylamine, purity ≥99%, Nantong Runfeng Petrochemical Co., Ltd.;

[0060] Formaldehyde solution, mass fraction 37wt.%, Shandong Haocheng Chemical New Materials Co., Ltd.;

[0061] Ammonia water, mass fraction 27wt.%, Shandong Hengchang Shengcheng Chemical Co., Ltd.;

[0062] Acetic acid, mass fraction 36wt.%, Shandong Xinhe New Materials Co., Ltd.;

[0063] Sodium chloride, purity ≥99%, Tianjin Jinyaoxiangcheng Technology Co., Ltd.;

[0064] Sodium carbonate, purity ≥99%, Langfang Qianyao Technology Co., Ltd.

[0065] Carbon powder, purity ≥99%, Anhui Kerun Nanotechnology Co., Ltd.;

[0066] Hydroxymethyl cellulose, purity ≥99%, Jinjinle (Hunan) Chemical Co., Ltd.;

[0067] Ferric oxyhydroxide, purity ≥99%, Jiangxi Ruiweier Biotechnology Co., Ltd.;

[0068] Other raw materials can be purchased from the market.

[0069] Example 1

[0070] This embodiment provides a method for preparing a selective non-catalytic reduction denitrifier, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0071] Step S1, placing 58g of urea at 62°C for vacuum drying for 3.6h, heating the vacuum-dried urea to 112°C for heat treatment for 2.2h, cooling to room temperature after the heat treatment, dissolving in 110mL of deionized water, stirring at 330rpm, adding 36g of diethyl phosphate, heating to 107°C for full reaction for 4.8h, and cooling to room temperature after the reaction to obtain phosphorylated urea;

[0072] Step S2: add 1.2 g of melamine to 105 mL of anhydrous ethanol, heat to 76° C., stir at 240 rpm until dissolved, add 1.3 g of diethylamine, heat to 90° C., react for 2.4 h, and then cool to room temperature to obtain amino melamine;

[0073] Step S3: 12 g of phosphorylated urea, 6.5 g of amination-modified melamine, 32 g of 16 wt.% formaldehyde solution and 24 g of deionized water are mixed, 13 wt.% ammonia solution is added to adjust the pH of the solution to 8.6, the temperature is raised to 74° C., and heated in a water bath for 1.3 h. Then, 12.5 wt.% acetic acid solution is added to adjust the pH of the solution to 4.3, the temperature is adjusted to 53° C., and heated in a water bath for 1.2 h. After the reaction is completed, the solution is placed in a vacuum dryer at 64° C. for 8.6 h. After drying, the solution is ground and mixed with 2.3 g of sodium chloride, 1.2 g of sodium carbonate, 1.1 g of carbon powder, 2.4 g of hydroxymethyl cellulose and 2.2 g of ferric oxyhydroxide to obtain a selective non-catalytic reduction denitrifier.

[0074] Figure 2 、 Figure 3 This is a TEM image of the heat-treated urea prepared in this example.

[0075] Example 2

[0076] This embodiment provides a method for preparing a selective non-catalytic reduction denitrifier, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0077] Step S1, placing 53g of urea at 65°C for vacuum drying for 3.8h, heating the vacuum-dried urea to 114°C for heat treatment for 2.5h, cooling to room temperature after the heat treatment, dissolving in 116mL of deionized water, stirring at 350rpm, adding 34g of diethyl phosphate, heating to 112°C for full reaction for 4.5h, and cooling to room temperature after the reaction to obtain phosphorylated urea;

[0078] Step S2: add 1.3 g of melamine to 110 mL of anhydrous ethanol, heat to 73° C., stir at 260 rpm until dissolved, add 1.5 g of diethylamine, heat to 93° C., react for 2.6 hours, and then cool to room temperature to obtain amino melamine;

[0079] Step S3: 11 g of phosphorylated urea, 7.5 g of amination-modified melamine, 34 g of a 17.5 wt.% formaldehyde solution, and 22 g of deionized water are mixed, 12 wt.% ammonia solution is added to adjust the pH of the solution to 8.7, the temperature is raised to 76° C., and heated in a water bath for 1.6 h. Then, 13 wt.% acetic acid solution is added to adjust the pH of the solution to 4.5, the temperature is adjusted to 51° C., and heated in a water bath for 1.4 h. After the reaction is completed, the solution is placed in a vacuum dryer at 66° C. for 8.3 h. After drying, the solution is ground and mixed with 2.5 g of sodium chloride, 1.4 g of sodium carbonate, 1.3 g of carbon powder, 2.2 g of hydroxymethyl cellulose, and 2.5 g of ferric oxyhydroxide to obtain a selective non-catalytic reduction denitrifier.

[0080] Example 3

[0081] This embodiment provides a method for preparing a selective non-catalytic reduction denitrifier, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0082] Step S1, placing 60g of urea at 63°C for vacuum drying for 4.2h, heating the vacuum-dried urea to 115°C for heat treatment for 2.4h, cooling to room temperature after the heat treatment, dissolving in 118mL of deionized water, stirring at 320rpm, adding 40g of diethyl phosphate, heating to 110°C for sufficient reaction for 4.7h, and cooling to room temperature after the reaction to obtain phosphorylated urea;

[0083] Step S2: add 1.15 g of melamine to 117 mL of anhydrous ethanol, heat to 72° C., stir at 230 rpm until dissolved, add 1.7 g of diethylamine, heat to 87° C., react for 2.3 h, and then cool to room temperature to obtain amino melamine;

[0084] Step S3: 12.5 g of phosphorylated urea, 5.5 g of aminated melamine, 31 g of a 16.5 wt.% formaldehyde solution, and 25 g of deionized water are mixed, 11.5 wt.% ammonia solution is added to adjust the pH of the solution to 8.6, the temperature is raised to 73° C., and heated in a water bath for 1.5 h. Then, 12.5 wt.% acetic acid solution is added to adjust the pH of the solution to 4.7, the temperature is adjusted to 53° C., and heated in a water bath for 1.6 h. After the reaction is completed, the solution is placed in a vacuum dryer at 63° C. for 8.8 h. After drying, the solution is ground and mixed with 2.2 g of sodium chloride, 1.6 g of sodium carbonate, 1.7 g of carbon powder, 2.8 g of hydroxymethyl cellulose, and 2.6 g of ferric oxyhydroxide to obtain a selective non-catalytic reduction denitrifier.

[0085] Example 4

[0086] This embodiment provides a method for preparing a selective non-catalytic reduction denitrifier, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0087] Step S1, placing 65g of urea at 62°C for vacuum drying for 4.5h, heating the vacuum-dried urea to 117°C for heat treatment for 2.6h, cooling to room temperature after the heat treatment, dissolving in 124mL of deionized water, stirring at 360rpm, adding 43g of diethyl phosphate, heating to 112°C for full reaction for 5.1h, and cooling to room temperature after the reaction to obtain phosphorylated urea;

[0088] Step S2: add 1.35 g of melamine to 108 mL of anhydrous ethanol, heat to 77° C., stir at 260 rpm until dissolved, add 1.4 g of diethylamine, heat to 91° C., react for 2.4 h, and then cool to room temperature to obtain amino melamine;

[0089] Step S3: 13.7 g of phosphorylated urea, 6.4 g of amination-modified melamine, 37 g of 17.8 wt.% formaldehyde solution, and 26.5 g of deionized water are mixed, 13.4 wt.% ammonia solution is added to adjust the pH of the solution to 8.8, the temperature is raised to 77° C., and heated in a water bath for 1.7 h. Then, 13.6 wt.% acetic acid solution is added to adjust the pH of the solution to 4.6, the temperature is adjusted to 54° C., and heated in a water bath for 1.7 h. After the reaction is completed, the solution is placed in a vacuum dryer at 66° C. for 9.2 h. After drying, the solution is ground and mixed with 2.1 g of sodium chloride, 1.3 g of sodium carbonate, 1.5 g of carbon powder, 2.6 g of hydroxymethyl cellulose, and 2.2 g of ferric oxyhydroxide to obtain a selective non-catalytic reduction denitrifier.

[0090] Example 5

[0091] This embodiment provides a method for preparing a selective non-catalytic reduction denitrifier, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0092] Step S1, placing 62g of urea at 67°C for vacuum drying for 3.4h, heating the vacuum-dried urea to 112°C for heat treatment for 2.5h, cooling to room temperature after the heat treatment, dissolving in 114mL of deionized water, stirring at 320rpm, adding 38g of diethyl phosphate, heating to 108°C for full reaction for 5.3h, and cooling to room temperature after the reaction to obtain phosphorylated urea;

[0093] Step S2: 1.27 g of melamine was added to 112 mL of anhydrous ethanol, the temperature was raised to 71° C., and the mixture was stirred at 220 rpm until dissolved. 1.65 g of diethylamine was added, the temperature was raised to 93° C., and the mixture was fully reacted for 2.5 hours, and then cooled to room temperature to obtain amino melamine.

[0094] Step S3: 12.8 g of phosphorylated urea, 7.7 g of aminated melamine, 34 g of an 18.4 wt.% formaldehyde solution, and 23.7 g of deionized water are mixed, 12.4 wt.% ammonia solution is added to adjust the pH of the solution to 8.7, the temperature is raised to 74° C., and heated in a water bath for 1.2 h. Then, 11.6 wt.% acetic acid solution is added to adjust the pH of the solution to 4.2, the temperature is adjusted to 52° C., and heated in a water bath for 1.3 h. After the reaction is completed, the solution is placed in a vacuum dryer at 62° C. for 8.7 h. After drying, the solution is ground and mixed with 2.4 g of sodium chloride, 1.5 g of sodium carbonate, 1.9 g of carbon powder, 2.7 g of hydroxymethyl cellulose, and 2.4 g of ferric oxyhydroxide to obtain a selective non-catalytic reduction denitrifier.

[0095] Example 6

[0096] This embodiment provides a method for preparing a selective non-catalytic reduction denitrifier, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0097] Step S1, placing 58g of urea at 61°C for vacuum drying for 4.6h, heating the vacuum-dried urea to 118°C for heat treatment for 2.7h, cooling to room temperature after the heat treatment, dissolving in 122mL of deionized water, stirring at 380rpm, adding 43g of diethyl phosphate, heating to 113°C for full reaction for 4.8h, and cooling to room temperature after the reaction to obtain phosphorylated urea;

[0098] Step S2: 1.17 g of melamine was added to 109 mL of anhydrous ethanol, the temperature was raised to 74° C., and the mixture was stirred at 270 rpm until dissolved. 1.84 g of diethylamine was added, the temperature was raised to 100° C., and the mixture was fully reacted for 2.6 hours, and then cooled to room temperature to obtain amino melamine.

[0099] Step S3: 14.2 g of phosphorylated urea, 6.9 g of amination-modified melamine, 37 g of 17.6 wt.% formaldehyde solution, and 28.2 g of deionized water are mixed, 11.9 wt.% ammonia solution is added to adjust the pH of the solution to 9.0, the temperature is raised to 76° C., and heated in a water bath for 1.7 h. Then, 14.1 wt.% acetic acid solution is added to adjust the pH of the solution to 4.8, the temperature is adjusted to 54° C., and heated in a water bath for 1.6 h. After the reaction is completed, the solution is placed in a vacuum dryer at 65° C. for 9.3 h. After drying, the solution is ground and mixed with 2.0 g of sodium chloride, 1.3 g of sodium carbonate, 1.6 g of carbon powder, 2.9 g of hydroxymethyl cellulose, and 3.0 g of ferric oxyhydroxide to obtain a selective non-catalytic reduction denitrifier.

[0100] Example 7

[0101] This embodiment provides a method for preparing a selective non-catalytic reduction denitrifier, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0102] Step S1, placing 66g of urea at 68°C for vacuum drying for 3.9h, heating the vacuum-dried urea to 114°C for heat treatment for 2.5h, cooling to room temperature after the heat treatment, dissolving in 112mL of deionized water, stirring at 340rpm, adding 45g of diethyl phosphate, heating to 110°C for full reaction for 5.4h, and cooling to room temperature after the reaction to obtain phosphorylated urea;

[0103] Step S2: add 1.38 g of melamine to 114 mL of anhydrous ethanol, heat to 73° C., stir at 260 rpm until dissolved, add 1.71 g of diethylamine, heat to 92° C., react for 2.2 h, and then cool to room temperature to obtain amino melamine;

[0104] Step S3: 13.2 g of phosphorylated urea, 8.5 g of aminated melamine, 32 g of a 16.7 wt.% formaldehyde solution, and 24.2 g of deionized water are mixed, 12.7 wt.% ammonia solution is added to adjust the pH of the solution to 8.5, the temperature is raised to 74° C., and heated in a water bath for 1.3 h. Then, 12.1 wt.% acetic acid solution is added to adjust the pH of the solution to 4.4, the temperature is adjusted to 53° C., and heated in a water bath for 1.8 h. After the reaction is completed, the solution is placed in a vacuum dryer at 64° C. for 9.1 h. After drying, the solution is ground and mixed with 2.3 g of sodium chloride, 1.5 g of sodium carbonate, 1.7 g of carbon powder, 2.3 g of hydroxymethyl cellulose, and 2.4 g of ferric oxyhydroxide to obtain a selective non-catalytic reduction denitrifier.

[0105] Example 8

[0106] This embodiment provides a method for preparing a selective non-catalytic reduction denitrifier, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0107] Step S1, placing 55g of urea at 62°C for vacuum drying for 4.2h, heating the vacuum-dried urea to 116°C for heat treatment for 2.7h, cooling to room temperature after the heat treatment, dissolving in 120mL of deionized water, stirring at 300rpm, adding 40g of diethyl phosphate, heating to 115°C for full reaction for 5.8h, and cooling to room temperature after the reaction to obtain phosphorylated urea;

[0108] Step S2: add 1.22 g of melamine to 116 mL of anhydrous ethanol, heat to 76° C., stir at 240 rpm until dissolved, add 1.53 g of diethylamine, heat to 95° C., react for 2.7 h, and then cool to room temperature to obtain amino melamine;

[0109] Step S3: 12.6 g of phosphorylated urea, 7.4 g of amination-modified melamine, 38 g of a 17.6 wt.% formaldehyde solution, and 26.1 g of deionized water are mixed, 14.3 wt.% ammonia solution is added to adjust the pH of the solution to 8.8, the temperature is raised to 72° C., and heated in a water bath for 1.7 h. Then, 11.9 wt.% acetic acid solution is added to adjust the pH of the solution to 4.6, the temperature is adjusted to 55° C., and heated in a water bath for 1.5 h. After the reaction is completed, the solution is placed in a vacuum dryer at 69° C. for 9.5 h. After drying, the solution is ground and mixed with 2.4 g of sodium chloride, 1.7 g of sodium carbonate, 1.3 g of carbon powder, 2.6 g of hydroxymethyl cellulose, and 2.5 g of ferric oxyhydroxide to obtain a selective non-catalytic reduction denitrifier.

[0110] Comparative Example 1

[0111] This comparative example provides a selective non-catalytic reduction denitrifier, which differs from Example 1 in that, in step S1, the urea heat treatment temperature is adjusted to 132°C, which is 20°C higher than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0112] Comparative Example 2

[0113] This comparative example provides a selective non-catalytic reduction denitrifier, which differs from Example 1 in that, in step S1, the urea heat treatment temperature is adjusted to 92°C, which is 20°C lower than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0114] Comparative Example 3

[0115] This comparative example provides a selective non-catalytic reduction denitrifier, which differs from Example 1 in that, in step S1, the feeding amount of diethyl phosphate is adjusted to 56 g, which is 20 g more than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0116] Comparative Example 4

[0117] This comparative example provides a selective non-catalytic reduction denitrifier, which differs from Example 1 in that, in step S1, the feeding amount of diethyl phosphate is adjusted to 16 g, which is 20 g less than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0118] The embodiment of the present invention and the comparative example are both at 200Nm 3 / h SNCR denitrification simulation experimental system. By burning diesel in the burner to generate flue gas, the temperature of the flue gas is adjusted by controlling the amount of diesel burned. The device can adjust the flue gas temperature within the range of 900-1100℃. NO is introduced into the device to adjust the NOx concentration level in the flue gas. The inlet NOx concentration is 200mg / Nm3 , the test results are shown in Table 1.

[0119] Table 1 Test results of selective non-catalytic reduction denitrification agents prepared in Examples 1-8 and Comparative Examples 1-4

[0120]

[0121] As can be seen from the data of Example, Comparative Example 1, and Comparative Example 2, the denitration efficiency of Comparative Example 1 and Comparative Example 2 is lower than that of Example 1. This is because, in Comparative Example 1, the heat treatment temperature is too high, which may cause urea to decompose, resulting in a reduction in the effective amount of urea and a decrease in the overall effect of the denitrifier; in Comparative Example 2, the heat treatment temperature is too low, α-urea cannot be converted into β-urea, and urea is not easily decomposed to release ammonia, which reacts with nitrogen oxides, reducing the denitration efficiency.

[0122] It can be seen from the data of Example, Comparative Example 3, and Comparative Example 4 that the denitration efficiency of Comparative Example 3 and Comparative Example 4 is lower than that of Example 1. This is because, in Comparative Example 3, the excess diethyl phosphate reacts not only with the amino groups of urea, but also with its own phosphate groups or other amino groups, resulting in the formation of unnecessary by-products. The formation of by-products occupies the reaction sites and reduces the denitration efficiency. In Comparative Example 4, when the amount of diethyl phosphate is insufficient, the phosphorylation reaction of urea may be incomplete, resulting in the inability of urea to effectively bind to the phosphate groups, thereby reducing the denitration efficiency.

[0123] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a selective non-catalytic reduction denitrifier, characterized in that: The preparation method is: Step S1, placing urea under vacuum drying at a first temperature, heating the vacuum-dried urea to a second temperature for heat treatment, cooling the urea to room temperature after the heat treatment, dissolving the urea in deionized water, stirring the urea, adding a phosphate, heating the urea to a third temperature for sufficient reaction, and cooling the urea to room temperature after the reaction to obtain phosphorylated urea; Step S2, adding melamine to anhydrous ethanol, heating to a fourth temperature, stirring until dissolved, adding an amination reagent, heating to a fifth temperature, and cooling to room temperature after sufficient reaction to obtain amination melamine; Step S3: mixing phosphorylated urea, amination melamine, formaldehyde solution and deionized water, adding ammonia solution to adjust the pH of the solution to 8.5-9.0, heating to a fourth temperature, heating in a water bath, adding acetic acid solution to adjust the pH of the solution to 4-5, adjusting to a sixth temperature, heating in a water bath, and vacuum drying at the first temperature after the reaction is completed. After drying, grinding and mixing with sodium chloride, sodium carbonate, carbon powder, hydroxymethyl cellulose and ferric oxyhydroxide to obtain a selective non-catalytic reduction denitrifier.

2. The method for preparing a selective non-catalytic reduction denitrifier according to claim 1, characterized in that: Step S1, The feeding amount of the urea is 50-70g; The first temperature is 60-70°C; The vacuum drying time is 3-5h; The second temperature is 110-120°C; The heat treatment time is 2-3 hours.

3. The method for preparing a selective non-catalytic reduction denitrifier according to claim 1, characterized in that: Step S1, The volume of the deionized water is 100-130 mL; The phosphate ester is diethyl phosphate, and the feeding amount is 30-50g; The third temperature is 100-120° C.; The reaction time at the third temperature is 4-6 hours.

4. The method for preparing a selective non-catalytic reduction denitrifier according to claim 1, characterized in that: Step S2, The feeding amount of the melamine is 1-1.5g; The volume of the anhydrous ethanol is 100-120 mL; The fourth temperature is 70-80°C.

5. The method for preparing a selective non-catalytic reduction denitrifier according to claim 1, characterized in that: Step S2, The amination reagent is diethylamine, and the dosage is 1-2g; The fifth temperature is 80-100° C.; The reaction time at the fifth temperature is 2-3 hours.

6. The method for preparing a selective non-catalytic reduction denitrifier according to claim 1, characterized in that: Step S3, The feeding amount of the phosphorylated urea is 10-15g; The feeding amount of the amino melamine is 5-10g; The feeding amount of the formaldehyde solution is 30-40 g, and the mass fraction of the formaldehyde solution is 15-20 wt.%; The feeding amount of the deionized water is 20-30g; The mass fraction of the ammonia solution is 10-15 wt.%.

7. The method for preparing a selective non-catalytic reduction denitrifier according to claim 1, characterized in that: Step S3, The fourth temperature is 70-80°C; The water bath heating time of the fourth temperature is 1-2h; The mass fraction of the acetic acid solution is 10-15wt.%; The sixth temperature is 50-55°C; The water bath heating time at the sixth temperature is 1-2 hours.

8. The method for preparing a selective non-catalytic reduction denitrifier according to claim 1, characterized in that: Step S3, The vacuum drying time is 8-10h; The feeding amount of the sodium chloride is 2-3g; The feeding amount of the sodium carbonate is 1-2g.

9. The method for preparing a selective non-catalytic reduction denitrifier according to claim 1, characterized in that: Step S3, The feeding amount of the carbon powder is 1-2g; The feeding amount of the hydroxymethyl cellulose is 2-3g; The feeding amount of the iron oxyhydroxide is 2-3g.

10. A selective non-catalytic reduction denitrifier prepared according to the method for preparing a selective non-catalytic reduction denitrifier according to any one of claims 1 to 9.

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