Synergistic accelerant applicable to SNCR (selective non-catalytic reduction) denitration and application thereof

Abstract

The invention provides a synergistic accelerant suitable for SNCR (selective non-catalytic reduction) denitration and application of the synergistic accelerant. The synergistic accelerant comprises the following components in parts by weight: 2-80 parts of an activating agent, the activating agent is selected from at least one of sodium glycinate, sodium glutamate, sodium iminodiacetate, sodium aspartate, sodium aminopropionate, sodium aspartate and potassium aspartate; 3-12 parts of a catalyst, wherein the catalyst is selected from soluble heteropolyacid; 1-10 parts of a catalytic promoter; the catalytic promoter is selected from at least one of soluble tungstate and molybdate. A trace amount of synergistic accelerant is added into a common SNCR denitration solution, so that the reaction speed of NOx and reducing agents such as ammonia or urea can be increased, a temperature window of SNCR reaction moves downwards, the application range of the traditional SNCR technology is expanded, the removal efficiency of NOx is improved, and a low-cost and high-efficiency method is provided for pollution abatement of nitric oxide in waste gas.

Description

Technical Field

[0001] The invention relates to the technical field of waste gas denitration, and in particular to a synergistic accelerator suitable for SNCR denitration and application thereof. Background Art

[0002] Nitrogen oxides (NO X ) is a waste gas pollutant composed of a variety of compounds consisting of only two elements, nitrogen and oxygen, including N2O, NO, N2O2, N2O3, NO2, N2O4 and N2O5. Environmental problems such as photochemical smog, haze, acid rain and greenhouse effect in some parts of my country are related to the increase in the content of nitrogen oxides in the atmosphere. In addition, since nitric oxide and nitrogen dioxide are toxic in themselves, cardiovascular and cerebrovascular diseases, asthma and other respiratory diseases in areas with high nitrogen oxide content are also much higher than in other areas. Therefore, efficient control of nitrogen oxide pollution is an inevitable requirement for protecting the ecological environment and ensuring human health. Nitrogen oxides are mainly NO2 and NO. More than 95% of nitrogen oxides in the atmosphere are NO, and more than 90% of nitrogen oxides in flue gas are also NO. Therefore, nitrogen oxide control is mainly to reduce NO pollution.

[0003] The NO concentration in the exhaust gas is low, only a few hundred milligrams per cubic meter. x The concentration standard for ultra-low emissions is less than 50 mg or even 35 mg per cubic meter. Since low-concentration NO has weak reaction ability, is chemically inert, and is difficult to dissolve in water, NO pollution control is technically very difficult. Selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) are the two most widely used methods for nitrogen oxide control. Both use a reducing agent containing amine free radicals (usually urea or ammonia solution) to react with nitrogen oxides to generate nitrogen and water to achieve the purpose of nitrogen oxide emission reduction. SCR technology is the preferred method for flue gas nitrogen oxide control due to its fast reaction speed and high NOx control efficiency, but the method is complex, occupies a large area, and the catalyst is easily poisoned and deactivated, so it requires large investment and high operating costs. Usually, SNCR technology is to inject ammonia solution or urea solution at a position where the boiler furnace or flue temperature is appropriate (ammonia: 850℃~950℃, urea: 950℃~1050℃) to reduce NO or NO2 in the flue gas to N2 and H2O. Since no catalyst is used, the investment and operating costs are low. The problems are slow reaction speed and low nitrogen oxide treatment efficiency, generally only 30%~50%. Increasing the ammonia-nitrogen ratio can improve the nitrogen oxide removal efficiency, but the amount of ammonia escape increases. The escaped ammonia reacts with sulfur trioxide and hydrogen chloride in the flue gas to form ammonium bisulfate and ammonium chloride, which are deposited on the rear heating surface, causing scaling and blockage of the rear heating surface, affecting the life of the equipment and reducing the combustion efficiency in the furnace.

[0004] The flue gas temperature of some industrial furnaces is not high. The conventional SNCR technology has low efficiency in nitrogen oxide control and is difficult to meet the increasingly stringent environmental protection requirements. Due to the large-scale use of solar and wind power generation, large coal-fired power plants that play a peak load role need to operate at low loads, and the flue gas temperature is not high. The use of SNCR technology to control NO x Pollution is also difficult to meet strict environmental standards. When using SCR technology, the catalyst is easily deactivated, the cost is high, and the burden on enterprises is heavy. Therefore, it is urgent to improve the existing selective non-catalytic reduction denitrification technology, reduce costs, improve efficiency, and lower the temperature window, expand the application field of SNCR technology, and provide technical support for green development.

[0005] In order to improve the denitration efficiency of SNCR and broaden the temperature window of SNCR, many scholars have conducted useful explorations. The literature (Chemosphere.2015,122:213-218) proposed that adding Na / K ions to the SNCR denitration solution can promote the reduction of NH3 to NO in the temperature range of 850-1150°C; the literature (Energy Conversion and Management.2011,52(10):3083-3088) reported that adding anionic surfactants or / and 1wt% NaOH mixed additives can improve the efficiency of urea reduction of NO in SNCR at 850°C and move the temperature window of the reaction toward low temperature; the literature (Combustion Science and Technology.2008,(04):333-337) found that the addition of sodium salt can improve the denitration efficiency of SNCR, among which sodium acetate has the most obvious effect. Although the efficiency-enhancing measures proposed in these literatures have achieved some results, the effect is not obvious when the smoke temperature is below 800°C, and the optimal denitration temperature cannot be moved toward low temperature. Some patents report the use of solid denitrifiers to improve the removal effect of nitrogen oxides. Patent CN108187490A proposes a selective non-catalytic reduction denitrifier composed of urea, melamine and / or cyanuric acid, activated wood powder, bentonite, quicklime, iron red and / or manganese dioxide catalyst; Patent CN106621782A uses urea, ammonium carbonate, ammonium bicarbonate, ammonium acetate, etc. as ammonia sources, one or more of polypropylene salt, polyalkyl acrylate, and polyacrylamide as synergists, and adds one or more of stearate, mildew inhibitor, zeolite magnesium oxide and precipitated calcium carbonate to form a denitrifier of selective non-catalytic reduction technology, which is used to reduce nitrogen oxides in flue gas at 800-1050°C. The catalysts, catalytic aids, etc. in these solid denitrifiers contain water-insoluble solid substances or metal salts that will generate water-insoluble hydroxide precipitation in urea and ammonia solutions, so they are not suitable for use in the SNCR denitrification process of urea or ammonia solutions.

[0006] In summary, there is an urgent need to develop a new, efficient and low-cost nitrogen oxide control technology to overcome the high cost of existing SCR technology and the problems of low denitrification efficiency, limited temperature window, ammonia escape, and limited application of solid denitrification agents in SNCR technology, so as to meet increasingly stringent environmental protection requirements. Summary of the invention

[0007] In view of the above-mentioned deficiencies of the prior art, the present invention aims to provide a technology for the efficient treatment of nitrogen oxides in flue gas, especially boiler flue gas and industrial furnace flue gas, so as to overcome the defects of the existing SNCR technology and broaden the application of amino reducing agents and NO x The temperature window of the reaction improves the efficiency of nitrogen oxide removal and reduces the cost of nitrogen oxide treatment in flue gas.

[0008] Amine free radicals released by amino reducing agents (such as urea or ammonia) at high temperatures reduce nitrogen oxides in flue gas to nitrogen and water, and nitrogen oxides oxidize amine functional groups to nitrogen. x The reaction equations are shown in formula (1) and formula (2):

[0009] 4NH3+4NO+O2→4N2+6H2O(1)

[0010] 2NH3+NO+NO2→2N2+3H2O(2)The reaction equations of urea ((NH2)2CO) and NO are shown in equations (3), (4) and (5):

[0011] (NH2)2CO→2NH2+CO(3)

[0012] NH2+NO→N2+H2O(4)

[0013] 2CO+2NO→N2+2CO2(5)

[0014] However, the reaction of amine functional groups with NO and NO2 can only proceed smoothly at a temperature above 850°C. In order to accelerate the redox reaction rate of nitrogen oxides and amine functional groups, broaden the temperature window of the reaction of amine functional groups with nitrogen oxides, enable SNCR to efficiently treat nitrogen oxide pollution in flue gas, and expand the application field of SNCR technology, the concept of the present invention is as follows: develop a synergist, add a trace amount of synergist to the commonly used SNCR denitrification solution, the synergist has a good synergistic denitrification effect on the SNCR denitrification reducing agent, spray the solution containing the synergist and the amino reducing agent into the flue gas, which can effectively broaden the reaction temperature between the amino reducing agent and NO x The temperature window of the reaction can improve the removal efficiency of nitrogen oxides. xThe reaction speed with reducing agents such as ammonia or urea moves the temperature window of SNCR reaction downward, expands the application range of traditional SNCR technology, and improves NO x The removal efficiency is high, providing a low-cost and high-efficiency method for the treatment of nitrogen oxide pollution in exhaust gas.

[0015] In order to achieve the above object, the technical solution of the present invention is as follows:

[0016] The present invention provides a synergistic accelerator suitable for SNCR denitration, comprising the following components in parts by weight:

[0017] 2 to 80 parts of an activator, wherein the activator is selected from at least one of sodium glycine, sodium glutamate, sodium iminodiacetic acid, sodium aspartate, sodium aminopropionate, sodium aspartate and potassium aspartate. ;

[0018] 3 to 12 parts of a catalyst, wherein the catalyst is selected from a soluble heteropoly acid;

[0019] 1 to 10 parts of a catalyst promoter; the catalyst promoter is selected from at least one of a soluble tungstate and a molybdate.

[0020] That is, the weight ratio of the activator, the catalyst and the catalyst promoter in the synergistic promoter is (2-80):(3-12):(1-10), preferably (8-50):(5-10):(2-5).

[0021] As an example, the catalyst is selected from germanomolybdic acid (H4GeMo 12 O 40 ), germanium tungstic acid (H4GeW 12 O 40 ), boromolybdic acid (H5BMo 12 O 40 ), borotungstic acid (H5BW 12 O 40 ), cobalt molybdate (H6CoMo 12 O 40 ), cobalt tungstic acid (H6CoW 12 O 40 ), copper molybdate (H6CuW 12 O 40 ), copper tungstate (H6CuW 12 O 40 ), phosphomolybdic acid (H3PMo 12 O 40 ), phosphotungstic acid (H3PW 12 O 40 ), silicomolybdic acid (H4SiMo 12 O 40 ), silicotungstic acid (H4SiW 12 O 40 ), phosphomolybdic acid (H3+a PMo 12-a V a O 40 , a=1~6 natural numbers), phosphotungstic vanadic acid (H 3+y PW 12-y V y O 40 , y = 1 to 6) and phosphomolybdic acid (H3PMo 12-n W n O 40 , n=at least one of the natural numbers 0 to 12).

[0022] As an example, the promoter is selected from at least one of sodium molybdate, potassium molybdate, sodium tungstate, potassium tungstate, ammonium tungstate and ammonium molybdate.

[0023] The present invention also provides a denitrification liquid suitable for selective non-catalytic removal of nitrogen oxides in flue gas, wherein the mass percentages of the components in the denitrification liquid are: 0.5-50% of amino denitrification reducing agent, 0.002-0.08% of activator, 0.003-0.012% of catalyst, and 0.001-0.01% of catalyst aid; the solvent used in the denitrification liquid is water.

[0024] As an example, the amino denitration reducing agent is selected from at least one of urea and ammonia.

[0025] Preferably, the mass percentage of the activator in the denitration liquid is 0.008-0.05%.

[0026] Preferably, the mass percentage of the catalyst in the denitration liquid is 0.005-0.010%.

[0027] Preferably, the mass percentage of the catalyst aid in the denitration liquid is 0.002-0.005%.

[0028] Preferably, the mass percentage of the amino denitrification reducing agent in the denitrification liquid is 1 to 30%.

[0029] The present invention also provides a method for preparing the above-mentioned denitration liquid, comprising the following steps: preparing an activator, a catalyst, a co-catalyst and an amino denitration reducing agent into an aqueous solution according to mass percentage.

[0030] The present invention also provides an application of the denitrification liquid described above, wherein the denitrification liquid contacts the flue gas in a spraying manner under normal pressure, and removes nitrogen oxides in the flue gas at a reaction temperature of 550 to 900°C; wherein the concentration of nitrogen oxides in the flue gas is 80ppm to 1500ppm, the concentration of SO2 is 0 to 2000ppm, and the concentration of O2 is 0 to 20vol%.

[0031] More specifically, the denitrification liquid is sprayed into the area of ​​the boiler furnace with suitable temperature through the liquid delivery system, reacting with the nitrogen oxides in the flue gas to reduce the nitrogen oxides to nitrogen and water, thereby eliminating nitrogen oxide pollution.

[0032] The denitrification liquid of the present invention is applicable to flue gas with nitrogen oxide concentration of 80ppm-1500ppm, SO2 concentration of 0-2000ppm, and O2 concentration of 0-20vol%.

[0033] The operating pressure is normal pressure, and the optimal range of the reaction temperature is 560-780° C. Within this optimal range, a high denitration rate (>90%) is ensured while effectively reducing energy consumption.

[0034] The present invention adds a trace amount of synergist to the commonly used SNCR denitration solution (including amine-containing solutions such as ammonia water and urea) for selective non-catalytic reduction denitration of boiler and industrial furnace exhaust gas. Compared with the traditional SCR and SNCR denitration processes, it has the following advantages:

[0035] 1. High denitrification efficiency. The composition of the synergistic accelerator can be flexibly adjusted according to the changes in flue gas temperature and dust content. Compared with the traditional SNCR denitrification technology, the denitrification rate is significantly improved and can reach 99%.

[0036] 2. Large temperature range. The traditional SNCR technology can only achieve a high NOx removal efficiency at 850°C, but after using the synergistic promoter of the present invention, a high denitrification rate can still be achieved at 550°C, which broadens the temperature range for the reaction of NOx with reducing agents such as ammonia or urea, moves the appropriate temperature window downward, expands the applicable scope of the SNCR technology, and makes the exhaust gas with a temperature below 600°C have an economical and applicable denitrification technology.

[0037] 3. Simple process. Based on the traditional SNCR technology, adding a small amount of synergist to the ammonia solution or urea solution can achieve high-efficiency denitrification in a wide temperature range. Compared with the SCR method, it has low investment cost, does not use expensive catalysts, and occupies a small area.

[0038] 4. Green process. The added synergist will be completely gasified in the use environment, and will not precipitate powder or dirt. It is non-toxic, non-corrosive, non-explosive, and non-flammable. However, the catalyst used in the SCR method contains highly toxic vanadium pentoxide, which causes problems in the treatment of waste catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a comparison chart of the denitration effects of the synergistic promoters of Example 1 and Comparative Examples 1 to 5 in the present invention. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with the examples, but the contents of the present invention are not limited thereto. Unless otherwise specified, the percentages involved in the examples refer to percentages by mass.

[0041] Example 1

[0042] The denitrification liquid is prepared by adding water to the synergist and urea. The concentration of urea in the denitrification liquid is 10%. The components of the synergist and their concentrations in the denitrification liquid are shown in Table 1. The denitrification liquid evaluation is carried out in a quartz tube reactor with an inner diameter of 5.4 cm and a height of 100 cm. The gas flow rate is 4500 L / h, and the gas inlet composition is NO: 470 ppm, SO2: 1000 ppm, O2: 9.5 vol%, and the rest is nitrogen. The denitrification liquid is sprayed into the reactor at a rate of 1000 mL / h using a peristaltic pump. The gas outlet concentration is analyzed online using a testo340 flue gas analyzer, which automatically samples every two minutes. When the operation reaches stability, the gas outlet NO concentration is measured. The denitrification rate is calculated based on the change in NO concentration, that is, the denitrification rate = (gas inlet NO concentration-gas outlet NO concentration) / gas inlet NO concentration × 100%.

[0043] Comparative Examples 1 to 5 also prepare denitration liquid by adding synergist and urea to water, the concentration of urea in the denitration liquid is 10%, and the components of synergist and their concentrations in the denitration liquid are shown in Table 1. The denitration liquid evaluation device and method are the same as those in Example 1.

[0044] The results of different synergistic promoters in Example 1 and Comparative Examples 1 to 5 on promoting the denitration of reducing agents are shown in Figure 1 .

[0045] Table 1

[0046]

[0047] Example 2

[0048] The SNCR synergist is composed of sodium glycine, cobalt tungstic acid and ammonium molybdate. The synergist, ammonia and water are added together to prepare a denitrification liquid. The concentration of ammonia in the denitrification liquid is 4% (mass), the concentration of the activator sodium glycine is 0.07% (mass), the concentration of the catalyst cobalt tungstic acid is 0.008% (mass), and the concentration of the co-catalyst ammonium molybdate is 0.003% (mass).

[0049] The denitrification liquid evaluation device is the same as that in Example 1, with a reaction temperature of 610°C, a gas flow rate of 4500L / h, and a gas inlet composition of NO: 530ppm, SO2: 1600ppm, O2: 8.7vol%, and the rest being nitrogen. A peristaltic pump is used to spray the denitrification liquid into the reactor at a rate of 1000mL / h. The gas outlet concentration is analyzed online using a testo340 flue gas analyzer, which automatically samples once every two minutes. When the operation reaches stability, the gas outlet NO concentration is: 36-41ppm.

[0050] Example 3

[0051] SNCR synergistic accelerator is composed of sodium glutamate, phosphotungstovanadic acid (H6PW9V3O 40 ) and sodium molybdate, the denitrification liquid is prepared by adding synergist and ammonia water to water, the concentration of ammonia is 4% (mass), the concentration of activator sodium glutamate is 0.05% (mass), the catalyst is phosphotungstovanadic acid (H6PW9V3O 40 ) concentration is 0.009% (mass), and the concentration of the co-catalyst ammonium molybdate is 0.004% (mass).

[0052] The denitrification liquid evaluation device is the same as that in Example 1, with a reaction temperature of 780°C, a gas flow rate of 4500L / h, and a gas inlet composition of NO: 660ppm, SO2: 1500ppm, O2: 6.8vol%, and the rest being nitrogen. A peristaltic pump is used to spray the denitrification liquid into the reactor at a rate of 1000mL / h. The gas outlet concentration is analyzed online using a testo340 flue gas analyzer, which automatically samples once every two minutes. When the operation reaches stability, the gas outlet NO concentration is 5-8ppm.

[0053] Example 4

[0054] The SNCR synergist is composed of sodium aspartate, molybdic acid germanium and sodium tungstate. The synergist, urea and water are added together to prepare a denitrification liquid. The concentration of urea is 10% (mass), the concentration of the activator sodium aspartate is 0.07% (mass), the concentration of the catalyst molybdic acid germanium is 0.006% (mass), and the concentration of the co-catalyst sodium tungstate is 0.006% (mass).

[0055] The denitrification liquid evaluation device is the same as that in Example 1, with a temperature of 680°C, a gas flow rate of 4500L / h, and a gas inlet composition of NO: 590ppm, SO2: 1250ppm, O2: 9.5vol%, and the rest being nitrogen. A peristaltic pump is used to spray the denitrification liquid into the reactor at a rate of 1000mL / h. The gas outlet concentration is analyzed online using a testo340 flue gas analyzer, which automatically samples once every two minutes. When the operation reaches stability, the gas outlet NO concentration is: 27-33ppm.

[0056] Example 5

[0057] The SNCR synergist is composed of sodium aminopropionate, germanotungstic acid and potassium molybdate. The synergist, ammonia and water are added together to prepare a denitrification liquid. The concentration of ammonia is 4.0% (mass), the concentration of the activator sodium aminopropionate is 0.08% (mass), the concentration of the catalyst germanotungstic acid is 0.01% (mass), and the concentration of the co-catalyst sodium molybdate is 0.004% (mass).

[0058] The denitrification liquid evaluation device is the same as that in Example 1, with a temperature of 620°C, a gas flow rate of 4500L / h, and a gas inlet composition of NO: 380ppm, SO2: 1200ppm, O2: 9.2vol%, and the rest being nitrogen. A peristaltic pump is used to spray the denitrification liquid into the reactor at a rate of 1000mL / h. The gas outlet concentration is analyzed online using a testo340 flue gas analyzer, which automatically samples once every two minutes. When the operation reaches stability, the gas outlet NO concentration is: 28-31ppm.

[0059] Example 6

[0060] The SNCR synergist is composed of sodium iminodiacetate, cobalt molybdic acid and sodium tungstate. The synergist, urea and water are added together to prepare a denitration liquid. The concentration of urea in the denitration liquid is 10% (mass), the concentration of the activator sodium iminodiacetate is 0.08% (mass), the concentration of the catalyst cobalt molybdic acid is 0.006% (mass), and the concentration of the co-catalyst sodium tungstate is 0.004% (mass).

[0061] The denitrification liquid was evaluated in a quartz tube reactor with an inner diameter of 5.4 cm and a height of 100 cm. The reaction temperature was 560°C, the gas flow rate was 4500 L / h, and the gas inlet composition was NO: 470 ppm, SO2: 1000 ppm, O2: 9.5 vol%, and the rest was nitrogen. A peristaltic pump was used to spray the denitrification liquid into the reactor at a rate of 1000 mL / h. The gas outlet concentration was analyzed online using a testo340 flue gas analyzer, which automatically sampled every two minutes. When the operation reached stability, the gas outlet concentration was NO: 45-48 ppm.

[0062] Example 7

[0063] The assessment was carried out in a fluidized bed boiler in a power plant with a flue gas volume of 300,000m 3 / h, the flue gas temperature is 600~650℃, and the flue gas composition is analyzed by Gasmet DX4000 flue gas analyzer. x Content 380~420mg / m 3 The average value is 395mg / m 3 , SO2 content 1200mg / m3 About, oxygen content is about 9.8vol%. SNCR synergist is composed of potassium aspartate, molybdic acid germanium and sodium tungstate. The synergist and urea are added with water to prepare denitration liquid. The concentration of urea is 26% (mass), the concentration of activator potassium aspartate is 0.07% (mass), the concentration of catalyst molybdic acid germanium is 0.007% (mass), and the concentration of co-catalyst sodium tungstate is 0.006% (mass). A centrifugal pump is used to spray denitration liquid into the boiler at a rate of 100L / h, so that the nitrogen oxides in the flue gas react with urea to generate water and nitrogen. The outlet concentration of nitrogen oxides is maintained at 26-31mg / m 3 , ammonia content is less than 6mg / m 3 .

[0064] It should be noted that in other embodiments of the present invention, within the range of the steps, components, ratios, and process parameters described in the present invention, other different schemes obtained by specific selection can achieve the technical effects described in the present invention, so the present invention will not list them one by one. For example: when the reducing agent is 0.5%, the activator, catalyst, and catalyst promoter are at their maximum values, and the synergist is 0.102%; when the reducing agent is 50%, the activator, catalyst, and catalyst promoter are at their minimum values, and the synergist is at a minimum of 0.006%; these ratios can achieve the goal of broadening the range of amino reducing agents and NO x The temperature window of the reaction improves the efficiency of nitrogen oxide removal.

[0065] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person skilled in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A synergist suitable for SNCR denitrification, characterized in that: The synergistic accelerator comprises the following components in parts by weight: 2 to 80 parts of an activator, wherein the activator is at least one selected from sodium glycine, sodium glutamate, sodium iminodiacetic acid, sodium aspartate, sodium aminopropionate, sodium aspartate and potassium aspartate; 3 to 12 parts of a catalyst, wherein the catalyst is selected from a soluble heteropoly acid; 1 to 10 parts of a catalyst promoter; the catalyst promoter is selected from at least one of a soluble tungstate and a molybdate.

2. The synergistic accelerator according to claim 1, characterized in that The catalyst is selected from at least one of germanomolybdic acid, germanotungstic acid, boromolybdic acid, borotungstic acid, cobaltmolybdic acid, cobalttungstic acid, coppermolybdic acid, coppertungstic acid, phosphomolybdic acid, phosphotungstic acid, silicomolybdic acid, silicotungstic acid, phosphomolybdic vanadic acid, phosphotungstic vanadic acid and phosphomolybdic tungstic acid.

3. The synergistic accelerator according to claim 1, characterized in that The promoter is selected from at least one of sodium molybdate, potassium molybdate, sodium tungstate, potassium tungstate, ammonium tungstate and ammonium molybdate.

4. The synergistic accelerator according to claim 1, characterized in that The weight ratio of the activator, the catalyst and the catalyst promoter in the synergistic promoter is (8-50):(5-10):(2-5).

5. A denitrification liquid suitable for selective non-catalytic removal of nitrogen oxides from flue gas, characterized in that: The denitrification liquid comprises the synergist and the amino denitrification reducing agent as described in any one of claims 1 to 5; the mass percentages of the components in the denitrification liquid are: 0.5-50% amino denitrification reducing agent, 0.002-0.08% activator, 0.003-0.012% catalyst, and 0.001-0.01% catalyst aid; the solvent used in the denitrification liquid is water.

6. The denitration liquid according to claim 5, characterized in that: The amino denitration reducing agent is selected from at least one of urea and ammonia.

7. The denitration liquid according to claim 5, characterized in that: The mass percentages of the components in the denitration liquid are: 0.5-50% of amino denitration reducing agent, 0.008-0.05% of activator, 0.005-0.010% of catalyst, and 0.002-0.005% of catalyst aid; the solvent used in the denitration liquid is water.

8. The denitration liquid according to claim 6, characterized in that: The mass percentage of the amino denitration reducing agent in the denitration liquid is 1 to 30%.

9. The use of the denitrification liquid according to any one of claims 5 to 8, characterized in that: The denitrification liquid contacts the flue gas in a spraying manner under normal pressure, and removes nitrogen oxides in the flue gas at a reaction temperature of 550-900° C.; wherein the concentration of nitrogen oxides in the flue gas is 80ppm-1500ppm, the concentration of SO2 is 0-2000ppm and the concentration of O2 is 0-20vol%.

10. The use according to claim 9, characterized in that: The reaction temperature is 560-780°C.

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