A low-temperature denitration catalyst and its preparation method and flue gas denitration method

Abstract

The present invention relates to the technical field of denitration catalyst preparation, and discloses a low-temperature denitration catalyst and a preparation method thereof and a flue gas denitration method. The method comprises the following steps: (1) mixing a main active component, a secondary active component, an auxiliary agent and water to obtain an active impregnation liquid; (2) impregnating the denitration catalyst in the active impregnation liquid, and drying to obtain a low-temperature denitration catalyst. The method uses a denitration catalyst as a carrier material, and adopts an impregnation method to load the main active component, the secondary active component and the auxiliary agent onto the carrier material, which can improve the low-temperature denitration performance of the catalyst and reduce SO 2 Oxidation rate.

Description

Technical Field

[0001] The present invention relates to the technical field of denitration catalyst preparation, and in particular to a low-temperature denitration catalyst and a preparation method thereof, and a flue gas denitration method. Background Art

[0002] Selective catalytic reduction (SCR) denitrification technology is an efficient, reliable and mature flue gas denitrification technology, which is widely used in coal-fired flue gas denitrification systems. Denitrification catalyst is a key component of this technology. Since the implementation of denitrification of coal-fired flue gas in thermal power and non-power industries, millions of tons of denitrification catalysts have been put into use.

[0003] As coal-fired power generation units are gradually shifting from the main power source to the flexible power source, the demand for deep peak load operation is becoming stronger. When the unit is running at low load, the traditional V2O5-WO3 / TiO2 denitrification catalyst is not active at low temperature, resulting in excessive nitrogen oxide emissions, increased ammonia slip, and even failure of environmental protection equipment. The traditional response strategy is to use economizer bypass modification, which is costly and will lead to reduced boiler thermal efficiency. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem of insufficient low-temperature activity of denitration catalysts in the prior art, and to provide a low-temperature denitration catalyst and a preparation method thereof and a flue gas denitration method. The method uses a denitration catalyst as a carrier material and adopts an impregnation method to load the main active components, secondary active components and additives onto the carrier material, thereby improving the low-temperature denitration performance of the catalyst and reducing the SO2 oxidation rate.

[0005] In order to achieve the above object, the present invention provides a method for preparing a low-temperature denitration catalyst, which comprises the following steps:

[0006] (1) mixing the main active component, the secondary active component, the auxiliary agent and water to obtain an active impregnation solution;

[0007] (2) The denitration catalyst is immersed in the active impregnation solution, and then dried to obtain a low-temperature denitration catalyst.

[0008] Preferably, in step (1), the weight ratio of the main active component, the secondary active component and the auxiliary agent is 1:0.1-34:0.05-51, preferably 1:0.1-20:0.1-25, more preferably 1:1-5:0.5-6, wherein the main active component and the secondary active component are calculated as oxides.

[0009] Preferably, in step (2), the solid-liquid ratio of the denitration catalyst impregnated in the active impregnation solution is 1:0.5-4.

[0010] Preferably, in step (1), the main active component is ammonium metavanadate.

[0011] Preferably, in step (1), the secondary active component is a soluble salt of tungsten and / or molybdenum.

[0012] Preferably, the secondary active component is selected from one or more of ammonium metatungstate, ammonium paratungstate and ammonium heptamolybdate.

[0013] Preferably, in step (1), the auxiliary agent is selected from one or more of oxalic acid, sulfuric acid and ethanolamine.

[0014] Preferably, the denitration catalyst contains vanadium pentoxide, tungsten trioxide and titanium dioxide.

[0015] Preferably, based on the total weight of the denitration catalyst, the content of vanadium pentoxide is 3.2-15% by weight, and the content of tungsten trioxide is 3-10% by weight.

[0016] Preferably, step (1) comprises: mixing an auxiliary agent with water to obtain an auxiliary agent aqueous solution, and then mixing the main active component, the secondary active component and the auxiliary agent aqueous solution to obtain an active impregnation solution.

[0017] Preferably, the concentration of the auxiliary agent aqueous solution is 0.05-0.5 g / mL.

[0018] Preferably, the immersion time is 1-60 min.

[0019] A second aspect of the present invention provides a low-temperature denitration catalyst prepared by the method described above.

[0020] A third aspect of the present invention provides a flue gas denitration method, the flue gas denitration method comprising: contacting flue gas with a low-temperature denitration catalyst at 250-400°C;

[0021] Wherein, the low-temperature denitration catalyst is the low-temperature denitration catalyst described above.

[0022] Preferably, the flue gas contains ammonia, nitric oxide, sulfur dioxide, oxygen, water and nitrogen;

[0023] Preferably, the volume ratio of ammonia, nitric oxide, sulfur dioxide, oxygen, water and nitrogen is 1:1:0.5-6:20-100:20-200:600-1560.

[0024] Preferably, the ratio of the low-temperature denitration catalyst to the flue gas is 1 m 3 :(1-2)x10 4 m 3 / h.

[0025] The method of the present invention uses a denitration catalyst as a carrier material and adopts an impregnation method to load the main active component, the side active component and the auxiliary agent onto the carrier material, which can greatly increase the content of active substances on the surface of the denitration catalyst, and the side active component can increase the dispersion of the main active component, thereby improving the low-temperature denitration performance of the catalyst. At the same time, the active substances added on the carrier material will block the surface micropores, resulting in SO2 being unable to enter the surface micropores, thereby reducing the SO2 oxidation rate and reducing the production of the side reaction product SO3, thereby preventing ammonia, water and SO3 in the flue gas from generating ammonium sulfate, covering the active positions on the catalyst surface, and affecting the denitration performance of the catalyst; at the same time, the method has a simple process, does not require high-temperature drying and calcination, has low energy consumption, and has low production cost. The obtained low-temperature denitration catalyst has good low-temperature denitration activity, can meet the deep peak-shaving operation requirements of coal-fired power generation units, has great promotion and application value, and at the same time, the SO2 oxidation rate is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of the method for preparing a low-temperature denitration catalyst according to the present invention. DETAILED DESCRIPTION

[0027] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0028] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0029] A first aspect of the present invention provides a method for preparing a low-temperature denitration catalyst, the method comprising the following steps:

[0030] (1) mixing the main active component, the secondary active component, the auxiliary agent and water to obtain an active impregnation solution;

[0031] (2) The denitration catalyst is immersed in the active impregnation solution, and then dried to obtain a low-temperature denitration catalyst.

[0032] The method of the present invention is to immerse the denitration catalyst in an active impregnation solution containing a main active component, a side active component and an auxiliary agent. The main active component, the side active component and the auxiliary agent are mainly loaded on the denitration catalyst through adsorption. On the one hand, the content of active substances on the surface of the denitration catalyst is increased, and the side active component can improve the dispersion of the main active component, thereby improving the denitration performance of the prepared low-temperature denitration catalyst. On the other hand, the active substances added to the denitration catalyst will block the surface micropores, resulting in SO2 being unable to enter the surface micropores, thereby reducing the SO2 oxidation rate and reducing the generation of side reaction product SO3, thereby preventing ammonia, water and SO3 in the flue gas from generating ammonium sulfate, covering the active positions on the catalyst surface, and affecting the denitration performance of the catalyst.

[0033] In the method of the present invention, the denitration catalyst may be a conventional SCR denitration catalyst in the art; the denitration catalyst may be a commercially available product or a self-made product of the inventor. In a preferred embodiment, the denitration catalyst contains vanadium pentoxide, tungsten trioxide and titanium dioxide (vanadium pentoxide and tungsten trioxide are active components, and titanium dioxide is a carrier). In a more preferred embodiment, based on the total weight of the denitration catalyst, the content of vanadium pentoxide is 0.2-5% by weight, and the content of tungsten trioxide is 3-10% by weight.

[0034] In a preferred embodiment, in order to improve the low-temperature denitration performance of the prepared low-temperature denitration catalyst, in step (1), the main active component is ammonium metavanadate.

[0035] In some embodiments, in step (1), the secondary active component is a soluble salt of tungsten and / or molybdenum. In a preferred embodiment, the secondary active component is selected from one or more of ammonium metatungstate, ammonium paratungstate and ammonium heptamolybdate.

[0036] In the present invention, the auxiliary agent can be a conventional choice in the art, and its main function is to improve the solubility of the main active component. In a preferred embodiment, in step (1), the auxiliary agent is selected from one or more of oxalic acid, sulfuric acid and ethanolamine.

[0037] In some embodiments, in step (1), the weight ratio of the main active component, the secondary active component and the auxiliary agent is 1:0.1-34:0.05-51, preferably 1:0.1-20:0.1-25, wherein the main active component and the secondary active component are calculated as oxides.

[0038] In a more preferred embodiment, in order to ensure that the denitration catalyst is loaded with an appropriate amount of active components and side active components and dispersed relatively evenly, and to further improve the denitration performance of the prepared low-temperature denitration catalyst, in step (1), the weight ratio of the main active component, the side active component and the auxiliary agent is 1:1-5:0.5-6, wherein the main active component and the side active component are calculated as oxides, specifically, for example, can be 1:2.5:1.5, 1:2:3, 1:3:3, 1:1.5:4 or 1:1:1.

[0039] In a preferred embodiment, step (1) specifically comprises: mixing an auxiliary agent with water to obtain an auxiliary agent aqueous solution, and then mixing the main active component, the secondary active component and the auxiliary agent aqueous solution to obtain an active impregnation solution.

[0040] In a more preferred embodiment, the concentration of the aqueous solution of the auxiliary agent is 0.05-0.5 g / mL.

[0041] In the method of the present invention, the denitration catalyst needs to be immersed in the active impregnation liquid. In a preferred embodiment, in step (2), the solid-liquid ratio of the denitration catalyst immersed in the active impregnation liquid is 1:0.5-4.

[0042] In the present invention, the impregnation time is not limited, as long as the main active component, the secondary active component and the auxiliary agent can be loaded on the denitration catalyst. In a specific embodiment, the impregnation time can be 1-60 minutes.

[0043] In the present invention, the denitration catalyst is impregnated by using a frame tool. Specifically, the denitration catalyst is placed in the frame tool. When the frame tool is lowered, the denitration catalyst is immersed in the active impregnation liquid. When the frame tool is lifted, the denitration catalyst is taken out of the impregnation liquid.

[0044] In some embodiments, the drying is performed at room temperature, specifically, the drying temperature is 10-30°C.

[0045] The low-temperature denitration catalyst prepared by the method of the present invention has excellent low-temperature denitration performance and is particularly suitable for denitration at 250-400°C.

[0046] The second aspect of the present invention provides a low-temperature denitration catalyst prepared by the method described above. The low-temperature denitration catalyst comprises a denitration catalyst and a main active component, a secondary active component and an auxiliary agent supported on the denitration catalyst.

[0047] In some embodiments, the denitration catalyst is 80-99 weight % of the low-temperature denitration catalyst.

[0048] In some embodiments, the main active component is 0.2-3.4 weight % of the low-temperature denitration catalyst.

[0049] In some embodiments, the secondary active components account for 0.5-6.8 weight % of the low-temperature denitration catalyst.

[0050] In some embodiments, the auxiliary agent is 0.3-10.2 weight % of the low-temperature denitration catalyst.

[0051] A third aspect of the present invention provides a flue gas denitrification method, which comprises: contacting flue gas with a low-temperature denitrification catalyst at 250-400° C.; wherein the low-temperature denitrification catalyst is the low-temperature denitrification catalyst described above.

[0052] In a specific embodiment, the flue gas contains ammonia, nitric oxide, sulfur dioxide, oxygen, water and nitrogen.

[0053] In a preferred embodiment, the volume ratio of ammonia, nitric oxide, sulfur dioxide, oxygen, water and nitrogen is 1:1:0.5-6:20-100:20-200:600-1560.

[0054] In a more preferred embodiment, the contents of ammonia, nitric oxide, sulfur dioxide, oxygen, water and nitrogen are 500-1000 ppm, 500-1000 ppm, 500-3000 ppm, 2-5 volume %, 2-10 volume % and 60-78 volume %, respectively; wherein ppm is volume percentage.

[0055] In a preferred embodiment, the ratio of the low-temperature denitration catalyst to the flue gas is 1 m 3 :(1-2)x10 6 m 3 / h, that is (1-2)x10 4 m 3 / h flue gas volume corresponds to 1m 3 Low temperature denitrification catalyst.

[0056] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto.

[0057] Example 1

[0058] In this embodiment, the denitration catalyst in step (2) is an SCR denitration catalyst containing 0.2 wt % of vanadium pentoxide and 3 wt % of tungsten trioxide.

[0059] The method for preparing a low-temperature denitration catalyst comprises:

[0060] (1) Preparation of active impregnation solution: 3 g of auxiliary agent oxalic acid was dissolved in deionized water to obtain an auxiliary agent aqueous solution with a concentration of 0.05 g / mL, and then 2 g of the main active component ammonium metavanadate (calculated as vanadium pentoxide) and 5 g of the secondary active component ammonium heptamolybdate (calculated as molybdenum trioxide) were stirred and dissolved in the auxiliary agent aqueous solution at 25° C. to obtain an active impregnation solution;

[0061] (2) Impregnation: The denitration catalyst is immersed in the active impregnation solution at a solid-liquid ratio of 1:0.5, bubbled for 1 min, then taken out and drained (25°C).

[0062] Example 2

[0063] In this embodiment, the denitration catalyst in step (2) is an SCR denitration catalyst containing 1 weight % of vanadium pentoxide and 5 weight % of tungsten trioxide.

[0064] The method for preparing a low-temperature denitration catalyst comprises:

[0065] (1) Preparation of active impregnation solution: 50 g of auxiliary sulfuric acid was dissolved in deionized water to obtain an auxiliary aqueous solution with a concentration of 0.25 g / mL, and then 17 g of the main active component ammonium metavanadate (calculated as vanadium pentoxide), 17 g of the secondary active component ammonium paratungstate (calculated as tungsten trioxide) and 17 g of ammonium heptamolybdate (calculated as molybdenum trioxide) were stirred and dissolved in the auxiliary aqueous solution at 50° C. to obtain an active impregnation solution;

[0066] (2) Impregnation: The denitration catalyst is immersed in the active impregnation solution at a solid-liquid ratio of 1:2, and bubbled for 30 minutes, then taken out and drained (25°C).

[0067] Example 3

[0068] In this embodiment, the denitration catalyst in step (2) is an SCR denitration catalyst containing 5 weight % of vanadium pentoxide and 10 weight % of tungsten trioxide.

[0069] The method for preparing a low-temperature denitration catalyst comprises:

[0070] (1) Preparation of active impregnation solution: 102 g of auxiliary agent ethanolamine was dissolved in deionized water to obtain an auxiliary agent aqueous solution with a concentration of 0.5 g / mL, and then 34 g of the main active component ammonium metavanadate (calculated as vanadium pentoxide), 34 g of the secondary active component ammonium metatungstate (calculated as tungsten trioxide) and 34 g of ammonium heptamolybdate (calculated as molybdenum trioxide) were stirred and dissolved in the auxiliary agent aqueous solution at 96° C. to obtain an active impregnation solution;

[0071] (2) Impregnation: The denitration catalyst is immersed in the active impregnation solution at a solid-liquid ratio of 1:4, and bubbled for 60 minutes, then taken out and drained (25°C).

[0072] Example 4

[0073] The method of Example 2 was followed, except that the amount of ammonium paratungstate and ammonium heptamolybdate was 8.5 g each.

[0074] The method for preparing a low-temperature denitration catalyst comprises:

[0075] (1) Preparation of active impregnation solution: 50 g of auxiliary sulfuric acid was dissolved in deionized water to obtain an auxiliary aqueous solution with a concentration of 0.25 g / mL, and then 17 g of the main active component ammonium metavanadate (calculated as vanadium pentoxide), 8.5 g of the secondary active component ammonium paratungstate (calculated as tungsten trioxide) and 8.5 g of ammonium heptamolybdate (calculated as molybdenum trioxide) were stirred and dissolved in the auxiliary aqueous solution at 50° C. to obtain an active impregnation solution;

[0076] (2) Impregnation: The denitration catalyst is immersed in the active impregnation solution at a solid-liquid ratio of 1:2, and bubbled for 30 minutes, then taken out and drained (25°C).

[0077] Example 5

[0078] The method of Example 2 was followed, except that the secondary active component was 34 g of ammonium paratungstate (calculated as tungsten trioxide).

[0079] The method for preparing a low-temperature denitration catalyst comprises:

[0080] (1) Preparation of active impregnation solution: 50 g of auxiliary sulfuric acid was dissolved in deionized water to obtain an auxiliary aqueous solution with a concentration of 0.25 g / mL, and then 17 g of the main active component ammonium metavanadate (calculated as oxide) and 34 g of the secondary active component ammonium paratungstate (calculated as oxide) were stirred and dissolved in the auxiliary aqueous solution at 50° C. to obtain an active impregnation solution;

[0081] (2) Impregnation: The denitration catalyst is immersed in the active impregnation solution at a solid-liquid ratio of 1:2, and bubbled for 30 minutes, then taken out and drained (25°C).

[0082] Comparative Example 1

[0083] The method of Example 2 is followed, except that the method further includes roasting.

[0084] The method for preparing a low-temperature denitration catalyst comprises:

[0085] (1) Preparation of active impregnation solution: 50 g of auxiliary sulfuric acid was dissolved in deionized water to obtain an auxiliary aqueous solution with a concentration of 0.25 g / mL, and then 17 g of the main active component ammonium metavanadate (calculated as vanadium pentoxide), 17 g of the secondary active component ammonium paratungstate (calculated as tungsten trioxide) and 17 g of ammonium heptamolybdate (calculated as molybdenum trioxide) were stirred and dissolved in the auxiliary aqueous solution at 50° C. to obtain an active impregnation solution;

[0086] (2) Impregnation: The denitration catalyst was immersed in the active impregnation solution at a solid-liquid ratio of 1:2, bubbled for 30 minutes, taken out, drained (25°C), and calcined at 400°C for 5 hours.

[0087] Comparative Example 2

[0088] The method of Example 2 is followed, except that the active impregnation solution does not contain any secondary active components.

[0089] The method for preparing a low-temperature denitration catalyst comprises:

[0090] (1) Preparation of active impregnation solution: 50 g of auxiliary sulfuric acid was dissolved in deionized water to obtain an auxiliary aqueous solution with a concentration of 0.25 g / mL, and then 51 g of the main active component ammonium metavanadate (calculated as vanadium pentoxide) was stirred and dissolved in the auxiliary aqueous solution at 50° C. to obtain an active impregnation solution;

[0091] (2) Impregnation: The denitration catalyst is immersed in the active impregnation solution at a solid-liquid ratio of 1:2, and bubbled for 30 minutes, then taken out and drained (25°C).

[0092] Comparative Example 3

[0093] The method of Example 2 is followed, except that the active impregnation solution does not contain the main active component.

[0094] The method for preparing a low-temperature denitration catalyst comprises:

[0095] (1) Preparation of active impregnation solution: 50 g of auxiliary sulfuric acid was dissolved in deionized water to obtain an auxiliary aqueous solution with a concentration of 0.25 g / mL, and then 25.5 g of ammonium paratungstate (calculated as tungsten trioxide) and 25.5 g of ammonium heptamolybdate (calculated as molybdenum trioxide) as secondary active components were stirred and dissolved in the auxiliary aqueous solution at 50° C. to obtain an active impregnation solution;

[0096] (2) Impregnation: The denitration catalyst is immersed in the active impregnation solution at a solid-liquid ratio of 1:2, and bubbled for 30 minutes, then taken out and drained (25°C).

[0097] Test Example 1

[0098] The content of each component in the products prepared in the test examples and comparative examples was measured, and the contents of the denitration catalyst, the main active component, the secondary active component and the auxiliary agent in the products were calculated (all in weight %). The results are shown in Table 1.

[0099] The specific operations are:

[0100] The products obtained in the embodiments and comparative examples contain a denitration catalyst, a main active component, a secondary active component, and an auxiliary agent, wherein the weight of the denitration catalyst and the auxiliary agent is the weight added during the preparation process, and the weight of the denitration catalyst and the auxiliary agent in the product can be obtained by weighing. The weight of the main active component and the secondary active component is quantitatively detected by an X-ray fluorescence spectrometer, and then the weight of each component is divided by the sum of the weights of the components to obtain the content of each component.

[0101] Table 1

[0102]

[0103]

[0104] Test Example 2

[0105] The denitration catalyst in step (2) of Example 2 (conventional denitration catalyst), the products prepared in the examples and comparative examples were tested for their 280°C activity K value and SO2 / SO3 oxidation rate at 280°C as low-temperature denitration catalysts.

[0106] The test method is: the flue gas containing ammonia, nitric oxide, sulfur dioxide, oxygen, water and nitrogen are contacted with the conventional denitration catalyst, the products prepared in the embodiment and the comparative example at 280°C for denitration reaction, wherein the volume ratio of ammonia, nitric oxide, sulfur dioxide, oxygen, water and nitrogen in the flue gas is 1:1:3:50:100:1000, and the ratio of the low-temperature denitration catalyst to the flue gas is 1m 3 : 1.6x10 4 m 3 / h. The test results are shown in Table 2.

[0107] Table 2

[0108] <![CDATA[280℃ active K value / m·h -1 > <![CDATA[SO2 / SO3 oxidation rate at 280℃]]> Conventional denitrification catalyst 20.33 0.88 Example 1 32.88 0.59 Example 2 35.97 0.38 Example 3 34.67 0.45 Example 4 33.25 0.50 Example 5 32.77 0.52 Comparative Example 1 25.56 1.38 Comparative Example 2 22.39 1.22 Comparative Example 3 15.68 0.86

[0109] It can be seen from Table 2 that the low-temperature denitration catalysts obtained in Examples 1-3 have improved active K values ​​at 280°C compared with conventional denitration catalysts, which are increased by 62%, 77% and 71% respectively, among which the active K value of Example 2 is improved the most, and the low-temperature denitration catalysts obtained in Examples 1-3 all have good low-temperature denitration activity; the low-temperature denitration catalysts obtained in Examples 1-3 have lower SO2 / SO3 oxidation rates at 280°C than conventional denitration catalysts, which are reduced by 33%, 57% and 49% respectively, and the low-temperature denitration catalysts obtained in Examples 1-3 all have good low SO2 / SO3 oxidation rate performance; the active K value of the low-temperature denitration catalyst prepared in the comparative example is lower than that in the example, and the SO2 / SO3 oxidation rate is higher than that in the example, and the low-temperature denitration catalyst prepared in the example has better performance.

[0110] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a low-temperature denitration catalyst, characterized in that: The method consists of the following steps: (1) mixing an auxiliary agent with water to obtain an auxiliary agent aqueous solution, and then mixing a main active component, a secondary active component and the auxiliary agent aqueous solution to obtain an active impregnation solution, wherein the weight ratio of the main active component, the secondary active component and the auxiliary agent is 1:1-5:0.5-6, wherein the main active component and the secondary active component are calculated as oxides, the auxiliary agent is selected from one or more of oxalic acid, sulfuric acid and ethanolamine, the main active component is ammonium metavanadate, and the secondary active component is a soluble salt of tungsten and molybdenum; (2) impregnating a denitration catalyst in the active impregnation solution and drying the solution to obtain a low-temperature denitration catalyst, wherein the denitration catalyst contains vanadium pentoxide, tungsten trioxide and titanium dioxide, wherein the content of the vanadium pentoxide is 0.2-5% by weight and the content of the tungsten trioxide is 3-10% by weight based on the total weight of the denitration catalyst; In step (2), the denitration catalyst is immersed in the active impregnation solution at a solid-liquid ratio of 1:0.5-4; In step (2), no calcination is performed after drying; The concentration of the auxiliary agent aqueous solution is 0.05-0.5 g / mL.

2. The method according to claim 1, characterized in that In step (1), the secondary active components are selected from two or more of ammonium metatungstate, ammonium paratungstate and ammonium heptamolybdate.

3. The method according to claim 1, characterized in that The immersion time is 1-60 min.

4. A low-temperature denitration catalyst prepared by the method according to any one of claims 1 to 3.

5. A flue gas denitrification method, characterized in that: The flue gas denitration method comprises: contacting the flue gas with a low-temperature denitration catalyst at 250-400°C; Wherein, the low-temperature denitration catalyst is the low-temperature denitration catalyst according to claim 4.

6. The method according to claim 5, characterized in that The flue gas contains ammonia, nitric oxide, sulfur dioxide, oxygen, water and nitrogen.

7. The method according to claim 6, characterized in that The volume ratio of ammonia, nitric oxide, sulfur dioxide, oxygen, water and nitrogen is 1:1:0.5-6:20-100:20-200:600-1560.

8. The method according to claim 5 or 6, characterized in that: The ratio of the low-temperature denitration catalyst to the flue gas is 1m 3 : (1-2) x 10 4 m 3 / h.

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