Selective non-catalytic reduction denitration agent and preparation method thereof

Abstract

The invention belongs to the field of denitration agent preparation, and provides a selective non-catalytic reduction denitration agent and a preparation method thereof. Firstly, urea is subjected to heating treatment, stable crystal phase alpha-urea is converted into beta-urea, the hydrogen bond strength and intermolecular acting force in crystals are changed due to heating, thermal motion of urea molecules is increased due to temperature rise, intermolecular arrangement is loosened, exposure of reaction sites is increased, the contact surface of the molecules is larger, and the reaction time is shortened; phosphoric acid groups are introduced into the urea subjected to heat treatment, phosphorylated urea is formed through a chemical reaction, the adsorbability and reaction activity of the phosphorylated urea are improved, and the process is beneficial to enhancing the combining capacity of the urea and NOx, so that the denitration efficiency is improved; a proper amount of sodium carbonate, sodium chloride and iron oxyhydroxide are added into a reaction system, so that the activity of the denitration agent is promoted to be improved, and nitrogen oxide pollution in industrial waste gas can be effectively treated.

Description

Technical Field

[0001] The invention belongs to the field of denitrification agent preparation, and relates to a selective non-catalytic reduction denitrification agent and a preparation method thereof. Background Art

[0002] With the rapid development of industrialization, nitrogen oxides (NOx), as a major air pollutant, have become an important environmental issue of global concern. NOx not only causes acid rain and ozone layer depletion, but also has serious impacts on human health. Therefore, it is particularly important to control NOx emissions in industrial flue gas. Traditional denitrification 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, and has the advantages of high efficiency and wide applicability. However, the implementation cost of this technology is high, and the selectivity and durability of the catalyst also limit its application under certain working conditions. In addition, SCR usually requires a higher operating temperature and additional reducing agent, which increases the process complexity and cost. SNCR is another technology widely used in industrial flue gas denitrification. SNCR reduces NOx to nitrogen at high temperature by injecting a reducing agent (such as urea or ammonia) into the flue gas. However, the traditional SNCR reduction denitrifier has the problem of insufficient denitrification efficiency. Therefore, we need to prepare a selective non-catalytic reduction denitrifier. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a selective non-catalytic reduction denitrifier, which changes the crystal structure of urea and removes its volatile components by heat treating urea, thereby increasing the exposure of reaction sites, increasing the contact surface of molecules, and improving the reaction rate; in the heat-treated urea, a phosphate group is introduced, which can increase the nucleophilicity of ammonia and promote its reaction with nitrogen oxides, making it more effective in reacting with NOx, thereby meeting the needs of actual production.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a method for preparing a selective non-catalytic reduction denitrifier, the preparation method comprising:

[0006] Step S1, placing urea under vacuum drying at a first temperature, heating the vacuum-dried urea to a second temperature for heat treatment, cooling to room temperature after the heat treatment, dissolving in deionized water, stirring at a first stirring speed, adding phosphate, heating to a third temperature for sufficient reaction, cooling to room temperature after the reaction, and obtaining phosphorylated urea;

[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, 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 solution pH to 8.5-9.0, heating to a fourth temperature, heating in a water bath, adding acetic acid solution to adjust the solution pH to 4-5, adjusting to a sixth temperature, heating in a water bath, placing under vacuum drying at the first temperature after the reaction is completed, and grinding and mixing with sodium chloride, sodium carbonate, carbon powder, hydroxymethyl cellulose and ferric hydroxide after drying to obtain a selective non-catalytic reduction denitrification agent.

[0009] The crystal structure of urea may undergo a phase change during the heat treatment process, from a stable crystal 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 the heat treatment process, the crystal water in urea may be removed, causing its hydration state to change. This process makes urea more hydrophobic and increases its reactivity. The increase in temperature increases the thermal motion of urea molecules, resulting in loose arrangement of molecules, increased exposure of reaction sites, and a larger contact surface of molecules, 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] The introduction of phosphate groups into β-urea can bring many benefits. The phosphate groups can form strong hydrogen bonds and form stable intermediates with nitrogen oxides, thereby promoting the release of ammonia and the reaction with NOx, and improving the denitrification efficiency. The phosphate group can serve as the active center of the catalyst to promote the reaction and increase the rate of the denitrification reaction. The introduction of phosphate groups can increase the polarity of urea and improve its solubility in water, thereby increasing the effective concentration of urea in the reaction system. The phosphate group has multiple hydrogen bond donors and acceptors, which can form stable hydrogen bond interactions with nitrogen oxides. The formation of this hydrogen bond can reduce the activation energy of the reaction, thereby accelerating the release and reaction of ammonia. The introduction of phosphate groups changes the electronic environment of β-urea, making it a stronger reducing agent and enhancing its reactivity with NOx. It can increase the nucleophilicity of ammonia and promote its reaction with nitrogen oxides. The phosphate group may form a stable intermediate with the ammonia and nitrogen oxides generated by the reaction. This process makes the reaction path more efficient, reduces the occurrence of side reactions, and thus improves the overall denitrification efficiency.

[0012] One of the keys to the SNCR reaction is the active group. At low temperatures, there are not enough active groups, which makes it impossible to reduce NOx. FeOOH can provide active groups well to promote SNCR denitrification. In addition to its own high ability to reduce NOx, carbon can also generate CO in an oxygen-deficient environment to promote SNCR denitrification. At high temperatures, C can also react with NH3 to generate another reductant for SNCR denitrification, HCNO, which increases the NOx reductant.

[0013] As a preferred technical solution of the present invention, in step S1, the feeding amount of 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 instances, 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 the numerical range are also applicable.

[0019] In some optional examples, the first stirring speed is 300-400rpm, for example, it can be 300rpm, 310rpm, 320rpm, 330rpm, 340rpm, 350rpm, 360rpm, 370rpm, 380rpm, 390rpm or 400rpm, 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 instances, 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 unlisted values ​​within the numerical range are also applicable.

[0024] In some optional examples, the volume of 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 instances, 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 the numerical range are also applicable.

[0027] In some optional examples, the amount of the amination agent 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 instances, 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 it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] In some optional examples, the amount of the formaldehyde solution is 30-40g, for example, 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 instances, 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 the 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 the numerical range are also applicable.

[0035] In some optional examples, the mass fraction of the aqueous 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 it is not limited to the listed values, and other unlisted values ​​within the 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 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, 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 10-15wt.%, 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 the numerical range are also applicable.

[0039] In some optional embodiments, 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 instances, 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 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, 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 amount of hydroxymethyl cellulose 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.

[0047] In some optional examples, the feeding amount of the iron oxyhydroxide is 2-3g, for example, it can be 2.0g, 2.1g, 2.2.g, 2.3g, 2.4g, 2.5g, 2.6g, 2.7g, 2.8g, 2.9g or 3.0g, but it is not limited to the listed values, and other unlisted values ​​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 to promote the reaction and increase the rate of the denitration 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, thereby reducing the reaction activation energy, thereby accelerating the release and reaction of ammonia, enhancing its reaction activity with NOx, and improving the denitration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A flow chart of a method for preparing a selective non-catalytic reduction denitrifying agent 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 solution of the present invention is described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limitations on the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments recorded herein, those skilled in the art can also adopt other obvious 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 recorded 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] Iron 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 denitrification agent, such as Figure 1 As shown, the preparation method specifically comprises the following steps:

[0071] Step S1, 58g of urea is placed at 62°C for vacuum drying for 3.6h, the vacuum-dried urea is heated to 112°C for heat treatment for 2.2h, cooled to room temperature after the heat treatment, dissolved in 110mL of deionized water, stirred at 330rpm, then 36g of diethyl phosphate is added, the temperature is raised to 107°C for full reaction for 4.8h, and cooled to room temperature after the reaction to obtain phosphorylated urea;

[0072] Step S2, adding 1.2 g of melamine to 105 mL of anhydrous ethanol, heating to 76° C., stirring at 240 rpm until dissolved, adding 1.3 g of diethylamine, heating to 90° C., reacting for 2.4 h, and then cooling to room temperature to obtain amino melamine;

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

[0074] Figure 2 , Figure 3 This is the 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 denitrification agent, such as Figure 1 As shown, the preparation method specifically comprises the following steps:

[0077] Step S1, 53g of urea is placed at 65°C for vacuum drying for 3.8h, the vacuum-dried urea is heated to 114°C for heat treatment for 2.5h, cooled to room temperature after the heat treatment, dissolved in 116mL of deionized water, stirred at 350rpm, then 34g of diethyl phosphate is added, the temperature is raised to 112°C for sufficient reaction for 4.5h, and cooled to room temperature after the reaction to obtain phosphorylated urea;

[0078] Step S2, adding 1.3 g of melamine to 110 mL of anhydrous ethanol, heating to 73° C., stirring at 260 rpm until dissolved, adding 1.5 g of diethylamine, heating to 93° C., reacting for 2.6 hours, and then cooling to room temperature to obtain amino melamine;

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

[0080] Example 3

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

[0082] Step S1, 60g of urea is placed at 63°C for vacuum drying for 4.2h, the vacuum-dried urea is heated to 115°C for heat treatment for 2.4h, cooled to room temperature after the heat treatment, dissolved in 118mL of deionized water, stirred at 320rpm, then 40g of diethyl phosphate is added, the temperature is raised to 110°C for sufficient reaction for 4.7h, and cooled to room temperature after the reaction to obtain phosphorylated urea;

[0083] Step S2, adding 1.15 g of melamine to 117 mL of anhydrous ethanol, heating to 72° C., stirring at 230 rpm until dissolved, adding 1.7 g of diethylamine, heating to 87° C., reacting for 2.3 h, and then cooling to room temperature to obtain amination melamine;

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

[0085] Example 4

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

[0087] Step S1, 65g of urea is placed at 62°C for vacuum drying for 4.5h, the vacuum-dried urea is heated to 117°C for heat treatment for 2.6h, cooled to room temperature after the heat treatment, dissolved in 124mL of deionized water, stirred at 360rpm, then 43g of diethyl phosphate is added, the temperature is raised to 112°C for full reaction for 5.1h, and cooled to room temperature after the reaction to obtain phosphorylated urea;

[0088] Step S2, adding 1.35 g of melamine to 108 mL of anhydrous ethanol, heating to 77° C., stirring at 260 rpm until dissolved, adding 1.4 g of diethylamine, heating to 91° C., reacting for 2.4 h, and then cooling to room temperature to obtain amino melamine;

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

[0090] Example 5

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

[0092] Step S1, 62g of urea was placed under vacuum drying at 67°C for 3.4h, the vacuum-dried urea was heated to 112°C for heat treatment for 2.5h, cooled to room temperature after the heat treatment, dissolved in 114mL of deionized water, stirred at 320rpm, then 38g of diethyl phosphate was added, the temperature was raised to 108°C for full reaction for 5.3h, and cooled to room temperature after the reaction to obtain phosphorylated urea;

[0093] Step S2, adding 1.27 g of melamine to 112 mL of anhydrous ethanol, heating to 71° C., stirring at 220 rpm until dissolved, adding 1.65 g of diethylamine, heating to 93° C., reacting for 2.5 hours, and then cooling to room temperature to obtain amino melamine;

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

[0095] Example 6

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

[0097] Step S1, 58g of urea is placed at 61°C for vacuum drying for 4.6h, the vacuum-dried urea is heated to 118°C for heat treatment for 2.7h, cooled to room temperature after the heat treatment, dissolved in 122mL of deionized water, stirred at 380rpm, and then 43g of diethyl phosphate is added, the temperature is raised to 113°C for sufficient reaction for 4.8h, and cooled to room temperature after the reaction to obtain phosphorylated urea;

[0098] Step S2, adding 1.17 g of melamine to 109 mL of anhydrous ethanol, heating to 74° C., stirring at 270 rpm until dissolved, adding 1.84 g of diethylamine, heating to 100° C., reacting for 2.6 hours, and then cooling to room temperature to obtain amino melamine;

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

[0100] Example 7

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

[0102] Step S1, 66g of urea was placed at 68°C for vacuum drying for 3.9h, the vacuum-dried urea was heated to 114°C for heat treatment for 2.5h, cooled to room temperature after the heat treatment, dissolved in 112mL of deionized water, stirred at 340rpm, and then 45g of diethyl phosphate was added, the temperature was raised to 110°C for full reaction for 5.4h, and cooled to room temperature after the reaction to obtain phosphorylated urea;

[0103] Step S2, adding 1.38 g of melamine to 114 mL of anhydrous ethanol, heating to 73° C., stirring at 260 rpm until dissolved, adding 1.71 g of diethylamine, heating to 92° C., reacting for 2.2 h, and then cooling to room temperature to obtain amino melamine;

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

[0105] Example 8

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

[0107] Step S1, 55g of urea is placed at 62°C for vacuum drying for 4.2h, the vacuum-dried urea is heated to 116°C for heat treatment for 2.7h, cooled to room temperature after the heat treatment, dissolved in 120mL of deionized water, stirred at 300rpm, then 40g of diethyl phosphate is added, the temperature is raised to 115°C for sufficient reaction for 5.8h, and cooled to room temperature after the reaction to obtain phosphorylated urea;

[0108] Step S2, adding 1.22 g of melamine to 116 mL of anhydrous ethanol, heating to 76° C., stirring at 240 rpm until dissolved, adding 1.53 g of diethylamine, heating to 95° C., reacting for 2.7 h, and then cooling to room temperature to obtain amino melamine;

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

[0110] Comparative Example 1

[0111] This comparative example provides a selective non-catalytic reduction denitrification agent, 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, and 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 denitrification agent, 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, and 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 denitrification agent, which differs from Example 1 in that, in step S1, the feed amount of diethyl phosphate is adjusted to 56 g, which is 20 g more than that in Example 1, and 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 denitrification agent, which differs from Example 1 in that, in step S1, the feed amount of diethyl phosphate is adjusted to 16 g, which is 20 g less than that in Example 1, and the other process parameters and operating conditions are exactly the same as those in Example 1.

[0118] The embodiments of the present invention and the comparative examples are both at 200 Nm 3 / h SNCR denitrification simulation experimental system. By burning diesel in the burner to generate flue gas, the combustion amount of diesel is controlled to adjust the flue gas temperature. The device can make the flue gas temperature adjustable and controllable 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 denitrifiers prepared in Examples 1-8 and Comparative Examples 1-4

[0120]

[0121] It can be seen from the data of the embodiment, comparative example 1 and comparative example 2 that the denitration efficiency of comparative example 1 and comparative example 2 is lower than that of embodiment 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 reducing 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, urea is not easy to decompose to release ammonia to react with nitrogen oxides, and the denitration efficiency is reduced.

[0122] It can be seen from the data of 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, there is an excess of diethyl phosphate, which not only reacts with the amino group of urea, but also may react with its own phosphate group 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 diethyl phosphate is insufficient, the phosphorylation reaction of urea may be incomplete, resulting in the inability of urea to effectively combine with the phosphate group, thereby reducing the denitration efficiency.

[0123] The above description is only a specific implementation mode 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 are 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 to room temperature after the heat treatment, dissolving in deionized water, stirring evenly, adding phosphate, heating to a third temperature for sufficient reaction, cooling to room temperature after the reaction, and obtaining 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, 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 solution pH to 8.5-9.0, heating to a fourth temperature, heating in a water bath, adding acetic acid solution to adjust the solution pH to 4-5, adjusting to a sixth temperature, heating in a water bath, placing under vacuum drying at the first temperature after the reaction is completed, and grinding and mixing with sodium chloride, sodium carbonate, carbon powder, hydroxymethyl cellulose and ferric hydroxide after drying to obtain a selective non-catalytic reduction denitrification agent.

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 2-3h.

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 dosage 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 10-15wt.%.

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

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