CN111545049A

CN111545049A - SNCR (Selective non catalytic reduction) denitration system and method for removing escaping ammonia in SNCR denitration process

Info

Publication number: CN111545049A
Application number: CN202010357635.2A
Authority: CN
Inventors: 余剑
Original assignee: Nanjing Chibo Environmental Protection Technology Co ltd
Current assignee: Nanjing Chibo Environmental Protection Technology Co ltd
Priority date: 2020-04-29
Filing date: 2020-04-29
Publication date: 2020-08-18

Abstract

The invention discloses a method for eliminating escaping ammonia in an SNCR (selective non-catalytic reduction) denitration system, wherein the ammonia oxidation degradation system comprises an SNCR denitration system, a micro ammonia removal system and an ammonia conversion catalyst supply device, wherein the SNCR denitration system consists of a deamination reaction area, a coal economizer, an air preheater, a desulfurizing tower and a chimney; wherein the pneumatic mixing device is respectively connected with the ammonia conversion catalyst supply device and the gas outlet flue of the deamination reaction area; the ammonia conversion catalyst supply device is connected with the air outlet flue of the boiler economizer and the dust remover through a pneumatic conveying device. The method comprises the following steps: the flue gas generated in the denitration reaction zone of the SNCR denitration system is pneumatically mixed with an ammonia conversion catalyst at the temperature of 700 ℃ for ammonia to generate catalytic oxidation reaction, so that the flue gas with ammonia removed is obtained. The system and the method can eliminate the escape of ammonia in the flue gas, can further reduce the concentration of NO in the flue gas, avoid secondary pollution to the environment, are important supplements for the traditional SNCR process, have low equipment investment and have important application value.

Description

SNCR (Selective non catalytic reduction) denitration system and method for removing escaping ammonia in SNCR denitration process

Technical Field

The invention belongs to the technical field of environmental protection, and particularly relates to an SNCR (selective non-catalytic reduction) denitration system and a method for removing escaped ammonia in an SNCR denitration process.

Background

Aiming at China with a large amount of cement and garbage incineration, hazardous waste incineration and small and medium-sized industrial combustion furnaces and kilns, ammonia selective reduction (selective non-catalytic reduction (SNCR) and Selective Catalytic Reduction (SCR)) is mainly adopted to remove nitrogen oxides in flue gas, and the chemical reaction formula is as follows:

4NH₃+4NO+O₂=4N₂+6H₂O；

wherein, the SNCR process usually carries out reaction at about 900 ℃, and because no catalyst exists, the reaction rate is slow, and the NOx conversion rate is relatively low; the SCR reaction is usually carried out in the presence of a catalyst at 200-500 deg.C for selective catalytic reduction. In general, in order to achieve a high denitration rate in the flue gas, excessive ammonia is added into the flue gas, and the ammonia cannot escape. In particular, for SNCR processes, the ammonia-to-nitrogen ratio is typically between 1.2 and 2.0 due to poor reactivity, and the resulting ammonia slip is large. Too large ammonia injection amount not only causes the increase of denitration cost, but also causes secondary pollution due to ammonia escape.

Therefore, the method and the device for removing the trace ammonia escaping from the flue gas have a good application prospect. The research on the removal technology of trace ammonia is relatively less, for example, the coking gas is used for removing the ammonia in the gas in a spraying mode; removing ammonia in the biological fermentation waste gas by a biological filtration method; acid spraying deamination of tail gas in phosphate fertilizer industry and the like. CN101569834A mentions that conventional SCR and SNCR processes are improved by using ammonia decomposition catalyst, which mainly comprises NOx reduction system and ammonia reduction system, and high denitration rate is achieved by adding excessive NH3 at the front end, while downstream auxiliary ammonia decomposition system decomposes the remaining ammonia to achieve high denitration rate without increasing corresponding ammonia slip. CN106457142A discloses a method for flue gas de-oxidation, wherein flue gas generated in a rotary kiln for sintering cement clinker is directed into a calcination zone for deacidification of raw meal, an aqueous ammonia solution, ammonia or ammonia-releasing substances are injected into the calcination zone, for the denitrification of oxidic compounds in flue gases by means of a selective non-catalytic reduction process and for the guidance of a flue gas stream together with the ammonia slip produced in the denitrification oxidic compounds through a heat exchanger and at least one dust removal device, from which heat exchanger the flue gas stream is guided through a heat exchanger exhaust line over a catalyst, which is used for degrading excess ammonia with residual nitrogen oxides contained in the flue gas over a catalyst according to a selective catalytic reduction method, wherein the catalyst is arranged in a reactor arranged in the exhaust gas line of the heat exchanger and in an amount which corresponds only to the size required for the degradation of ammonia on a respective predetermined scale. The technologies are all based on removing ammonia in gas under low temperature conditions, and independent systems are required to be established, so that the removal of trace ammonia with ppm content is difficult to realize due to small treatment capacity, and ammonia escape in the SNCR process is not removed.

Disclosure of Invention

In order to solve the problems, the invention provides an SNCR (selective non-catalytic reduction) denitration system and a method for removing escaped ammonia in an SNCR denitration process, wherein the system and the method perform a secondary catalytic conversion process on ammonia which does not participate in the reaction in the conventional SNCR process, so that the escaped ammonia in flue gas can be eliminated, the concentration of NO in the flue gas can be further reduced, the secondary pollution to the environment is avoided, the system and the method are very important technical supplement and improvement for the conventional SNCR process, and have important application value.

In order to achieve the technical purpose and achieve the technical effect, the invention is realized by the following technical scheme:

an SNCR (selective non-catalytic reduction) denitration system comprises a deamination reaction area, an economizer, an air preheater, a desulfurizing tower, a chimney and an ammonia conversion catalyst supply device, and is characterized by further comprising a pneumatic mixing device or a pneumatic conveying device; when the ammonia conversion device comprises the pneumatic mixing device, the pneumatic mixing device is respectively connected with the ammonia conversion catalyst supply device and the gas outlet flue of the deamination reaction area; when the device comprises a pneumatic conveying device, the ammonia conversion catalyst supply device is connected with the air outlet flue of the boiler economizer through the pneumatic conveying device.

Further, the SNCR denitration system also comprises a dust remover.

Furthermore, the air inlet of the dust remover is connected with the air outlet of the pneumatic mixing device, and the dust outlet of the dust remover is connected with the feed inlet of the ammonia conversion catalyst supply device.

Further, the pneumatic conveying device is arranged between the boiler economizer and the dust remover, an air inlet of the dust remover is connected with an air outlet flue of the denitration reactor, and a dust outlet of the dust remover is connected with a feed inlet of the ammonia conversion catalyst supply device.

The invention also provides a method for removing escaping ammonia in the SNCR denitration process, which comprises the steps of pneumatically mixing the flue gas generated by SNCR denitration with an ammonia conversion catalyst at the temperature of 700 ℃ and reacting ammonia with catalytic oxidation to obtain the flue gas with ammonia removed.

Further, the ammonia conversion catalyst comprises a combination of any one or more of cobalt oxide, iron oxide, nickel oxide and manganese oxide, and the support is selected from a combination of any one or more of titanium oxide, silicon oxide and aluminum oxide.

Further, the ammonia conversion catalyst is any one or combination of more of an iron-aluminum oxide catalyst, an iron-titanium-aluminum-silicon oxide catalyst and a catalyst obtained by treating inorganic solid waste containing the active component and a carrier.

Further, the non-polar solid waste is selected from any one or combination of more of red mud, blast furnace slag, various tailings and waste catalysts; the catalyst obtained by treating the inorganic solid waste containing the active component and the carrier is selected from any one or combination of more of an iron-based denitration catalyst prepared from red mud, a waste vanadium-tungsten-titanium denitration catalyst and a catalyst prepared from titanium-containing blast furnace slag.

Further, the ammonia conversion catalyst is in the form of powder or granules.

Further, the particle size of the ammonia conversion catalyst is 1 to 100 μm when the ammonia conversion catalyst is in the form of powder, and 1 to 3mm when the ammonia conversion catalyst is in the form of particles; the amount of the ammonia conversion catalyst added is 0.01-10kg per standard square of flue gas.

Further, the flue gas and the ammonia conversion catalyst are pneumatically mixed through a pneumatic conveying device; spraying an ammonia conversion catalyst into an air outlet flue of the denitration reactor by using a pneumatic conveying device; the pneumatic conveying device is selected from an air compressor; the contact time of the ammonia conversion catalyst with the flue gas generated by the denitration reactor is more than 0.01 s.

Further, the flue gas and the ammonia conversion catalyst are pneumatically mixed by a pneumatic mixing device; introducing flue gas generated by a denitration reactor into a pneumatic mixing device containing an ammonia conversion catalyst; the pneumatic mixing device is selected from an ebullated bed; the contact time of the ammonia conversion catalyst with the flue gas generated by the denitration reactor is more than 0.01 s.

Further, collecting the ammonia conversion catalyst in the ammonia-removed flue gas for recycling; the ammonia conversion catalyst is recycled for 3-10 times; the ammonia conversion catalyst consists of a fresh ammonia conversion catalyst and a collected ammonia conversion catalyst in a mass ratio of 1:10 to 1: 20.

Further, ammonia conversion catalyst powder with the particle size of 1-100 mu m is sprayed into an air outlet flue of a denitration reactor of the SNCR denitration system by a pneumatic conveying device and is mixed with flue gas at the temperature of 300-700 ℃; or the flue gas generated by the denitration reactor of the SNCR denitration system is introduced into a pneumatic mixing device which is provided with an ammonia conversion catalyst with the particle size of 1-100 mu m and the temperature of 300-700 ℃; after the ammonia conversion catalyst is mixed with the flue gas, ammonia is subjected to catalytic oxidation reaction to obtain the flue gas with ammonia removed, the adding amount of the ammonia conversion catalyst is 0.001-1kg/Nm in the flue gas through carrying out the year by year, and the retention time is more than 0.01 s; collecting the ammonia conversion catalyst in the ammonia-removed flue gas, and mixing the ammonia conversion catalyst with a fresh ammonia conversion catalyst according to the mass ratio of 10-20:1 to obtain the ammonia conversion catalyst.

The invention has the following beneficial effects:

1. the SNCR denitration system provided by the invention has a simple structure, does not change the structure of the conventional SNCR denitration system, and has low equipment investment;

2. the method for removing the escaped ammonia in the SNCR denitration process has good mixing effect of the ammonia conversion catalyst and the flue gas, has obvious effect of removing the escaped ammonia, solves the problem of ammonia escape of the conventional SNCR denitration system and avoids secondary pollution to the environment, and the escaped ammonia amount in the treated flue gas is less than 3 ppm;

3. the method for removing the escaped ammonia in the SNCR denitration process can adsorb heavy metals in flue gas, particularly heavy metals in waste incineration, and degrade dioxin;

4. the ammonia conversion catalyst used by the method for removing the escaped ammonia in the SNCR denitration process has large specific surface area, can be recycled and has low cost;

5. the SNCR denitration system and the method for removing the escaped ammonia in the SNCR denitration process provided by the invention are very important technical supplement and improvement for the conventional SNCR process, and have important application values.

Drawings

FIG. 1 is a schematic diagram of the structure of an SNCR denitration system;

FIG. 2 is a schematic diagram of the SNCR denitration system when a pneumatic mixing device is selected;

FIG. 3 is a schematic diagram of the SNCR denitration system when a pneumatic conveying device is selected;

the method comprises the following steps of 1-a denitration reactor, 2-an economizer, 3-an air preheater, 4-a desulfurizing tower, 5-a chimney, 6-a deduster, 7-a catalyst supply device, 8-a pneumatic mixing device and 9-a pneumatic conveying device.

Detailed Description

The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

Preferred embodiments of the present invention will be described in detail below with reference to fig. 1-3, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, and the scope of the present invention can be more clearly and clearly defined.

Example 1

An SNCR denitration system, as shown in fig. 1, includes a denitration reaction region 1, an economizer 2, an air preheater 3, a dust remover 6, a desulfurization tower 4, and a chimney 5, and the connection manner between the denitration reactor, the economizer 2, the air preheater 3, the dust remover 6, the desulfurization tower 4, and the chimney 5 is well known to those skilled in the art and is not described herein again.

The SNCR denitration system also comprises a pneumatic conveying device 9 and an ammonia conversion catalyst supply device 7.

The ammonia conversion catalyst supply device 7 is connected with the air outlet flue of the denitration reactor through a pneumatic conveying device 9, and the pneumatic conveying device 9 is arranged between the economizer 2 and the denitration reactor.

The dust outlet of the dust remover 6 is connected with the feed inlet of an ammonia conversion catalyst supply device 7.

The pneumatic conveying device 9 comprises an air compressor.

The ammonia conversion feed device comprises a screw conveyor.

Example 2

An SNCR (selective non-catalytic reduction) denitration system comprises a denitration reaction zone 1, an economizer 2, an air preheater 3, a dust remover 6, a desulfurization tower 4 and a chimney 5, wherein the connection mode among the economizer 2, the air preheater 3, the dust remover 6, the desulfurization tower 4 and the chimney 5 is known by the technical personnel in the field and is not described herein;

the SNCR denitration system also comprises a pneumatic mixing device 8 and an ammonia conversion catalyst supply device 7;

the pneumatic mixing device 8 is respectively connected with the ammonia conversion catalyst supply device 7 and the gas outlet flue of the denitration reactor, and the pneumatic mixing device 8 is arranged between the denitration reactor and the economizer 2;

the air inlet of the dust remover 6 is connected with the air outlet of the pneumatic mixing device 8, and the dust outlet of the dust remover 6 is connected with the feed inlet of the ammonia conversion catalyst supply device 7;

the pneumatic mixing device 8 comprises an ebullated bed.

The ammonia conversion feed device comprises a screw conveyor.

Example 3

Carrying out flash evaporation with the SNCR denitration system of example 1, wherein the flue gas amount is 5 ten thousand Nm/h, carrying iron-based catalyst powder into a flue by using compressed air at a temperature interval of 700 ℃ before an economizer 2, mixing with the flue gas, carrying 0.1kg/Nm (5kg/h) of new catalyst, carrying 100kg/h of circulating catalyst, and reducing the concentration of NOx in the flue gas from 100mg/Nm to 60mg/Nm by flash evaporation; and (4) carrying out heavy harvest after the outlet ammonia concentration is reduced from 50mg/Nm to 5mg/Nm, so that the ammonia escape amount is less than 3ppm, and the discharged flue gas reaches the latest European standard.

Example 4

The SNCR denitration system in the embodiment 1 is used for treating flue gas of a cement kiln, the flue gas amount is 25 ten thousand Nm/h, denitration is carried out on the flue gas by adopting the SNCR method at the present stage, the initial ammonia-nitrogen ratio is 1.2, and the concentration of NOx at a flue gas outlet is 320mg/Nm in a dry year. Before the five-stage cyclone, 500kg/h of catalyst powder was added at a temperature of 600 ℃. Carrying out heavy year according to reduction of the concentration of NOx in the flue gas from 320mg/Nm to 250 mg/Nm; and (4) carrying out heavy harvest from 100mg/Nm to 5mg/Nm to ensure that the escape amount of ammonia is less than 3ppm, thereby realizing efficient utilization and low escape of ammonia.

Example 5

When the SNCR denitration system in embodiment 1 is used for treating flue gas which is dangerous solid waste, the flue gas amount is 10 ten thousand Nm/h, denitration is carried out on the flue gas by adopting the SNCR method at the present stage, the initial ammonia-nitrogen ratio is 1.5, and the concentration of NOx at a flue gas outlet is 150mg/Nm in thin year. After ammonia spraying, 500kg/h of iron-based catalyst powder prepared from red mud is added at the temperature of 400 ℃. Carrying out heavy year on the NOx concentration in the flue gas, wherein the NOx concentration is reduced from 150mg/Nm to 100 mg/Nm; and (4) carrying out heavy harvest from 100mg/Nm to 5mg/Nm to ensure that the escape amount of ammonia is less than 3ppm, thereby realizing efficient utilization and low escape of ammonia.

Example 6

The SNCR denitration system in the embodiment 1 is used for treating flue gas in medium and small industrial combustion furnace kiln flue gas with the flue gas amount of 1 ten thousand Nm/h, and at the present stage, the SNCR method is used for denitration of the flue gas, the initial ammonia-nitrogen ratio is 1.5, and the NOx concentration at the flue gas outlet is 150 mg/Nm. After ammonia spraying, 500kg/h of iron-based catalyst powder prepared from red mud is added at the temperature of 300 ℃. Carrying out heavy year on the NOx concentration in the flue gas, wherein the NOx concentration is reduced from 150mg/Nm to 100 mg/Nm; and (4) carrying out heavy harvest from 100mg/Nm to 5mg/Nm to ensure that the escape amount of ammonia is less than 3ppm, thereby realizing efficient utilization and low escape of ammonia.

Example 7

Performing labor-intensive research (SNCR) denitration system according to example 2 on the flue gas, wherein the amount of the flue gas is 5 ten thousand Nm/h, carrying iron-based catalyst powder into the flue gas by using compressed air at a temperature interval of 700 ℃ to mix with the flue gas before an economizer 2, the addition amount of new catalyst is 0.1 kg/Nm/year (5kg/h), the addition amount of circulating catalyst is 100kg/h, and the concentration of NOx in the flue gas is reduced from 100 mg/Nm/year to 60 mg/Nm/year; and (4) carrying out heavy harvest after the outlet ammonia concentration is reduced from 50mg/Nm to 5mg/Nm, so that the ammonia escape amount is less than 3ppm, and the discharged flue gas reaches the latest European standard.

Example 8

The SNCR denitration system in embodiment 2 is used for treating flue gas of a cement kiln with a flue gas amount of 25 ten thousand Nm/h, and at the present stage, an SNCR method is adopted for denitration of the flue gas, the initial ammonia-nitrogen ratio is 1.2, and the NOx concentration at the flue gas outlet is 320mg/Nm in a high-speed rice plantation method. Before the five-stage cyclone, 500kg/h of catalyst powder was added at a temperature of 600 ℃. Carrying out heavy year according to reduction of the concentration of NOx in the flue gas from 320mg/Nm to 250 mg/Nm; and (4) carrying out heavy harvest from 100mg/Nm to 5mg/Nm to ensure that the escape amount of ammonia is less than 3ppm, thereby realizing efficient utilization and low escape of ammonia.

Example 9

When the SNCR denitration system in embodiment 2 is used for treating flue gas which is dangerous solid waste, the flue gas amount is 10 ten thousand Nm/h, denitration is carried out on the flue gas by adopting the SNCR method at the present stage, the initial ammonia-nitrogen ratio is 1.5, and the concentration of NOx at a flue gas outlet is 150mg/Nm in thin year. After ammonia spraying, 500kg/h of iron-based catalyst powder prepared from red mud is added at the temperature of 400 ℃. Carrying out heavy year on the NOx concentration in the flue gas, wherein the NOx concentration is reduced from 150mg/Nm to 100 mg/Nm; and (4) carrying out heavy harvest from 100mg/Nm to 5mg/Nm to ensure that the escape amount of ammonia is less than 3ppm, thereby realizing efficient utilization and low escape of ammonia.

Example 10

The SNCR denitration system in the embodiment 2 is used for treating flue gas in middle and small industrial combustion furnace and kiln flue gas with a flue gas amount of 12 ten thousand Nm/h, and at the present stage, an SNCR method is adopted for denitration of the flue gas, the initial ammonia-nitrogen ratio is 1.5, and the concentration of NOx at a flue gas outlet is 150 mg/Nm. After ammonia spraying, 500kg/h of iron-based catalyst powder prepared from red mud is added at the temperature of 300 ℃. Carrying out heavy year on the NOx concentration in the flue gas, wherein the NOx concentration is reduced from 150mg/Nm to 100 mg/Nm; and (4) carrying out heavy harvest from 100mg/Nm to 5mg/Nm to ensure that the escape amount of ammonia is less than 3ppm, thereby realizing efficient utilization and low escape of ammonia.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. An SNCR (selective non-catalytic reduction) denitration system comprises a deamination reaction zone (1), an economizer (2), an air preheater (3), a desulfurizing tower (4), a chimney (5) and an ammonia conversion catalyst supply device (7), and is characterized by further comprising a pneumatic mixing device (8) or a pneumatic conveying device (9); when the SNCR denitration system comprises a pneumatic mixing device (8), the pneumatic mixing device (8) is respectively connected with an ammonia conversion catalyst supply device (7) and an air outlet flue of the deamination reaction zone (1); when the SNCR denitration system comprises a pneumatic conveying device (9), the ammonia conversion catalyst supply device (7) is connected with an air outlet flue of the boiler economizer (2) through the pneumatic conveying device (9).

2. An SNCR denitration system according to claim 1, further comprising a dust remover (6).

3. The SNCR denitration system according to claim 2, wherein the gas inlet of the dust remover (6) is connected with the gas outlet of the pneumatic mixing device (8), and the dust outlet of the dust remover (6) is connected with the feed inlet of the ammonia conversion catalyst supply device (7).

4. The SNCR denitration system according to claim 2, wherein the pneumatic conveying device (9) is arranged between the boiler economizer (2) and the dust remover (6), the air inlet of the dust remover (6) is connected with the air outlet flue of the denitration reactor, and the dust outlet of the dust remover is connected with the inlet of the ammonia conversion catalyst supply device (7).

5. A method for removing escaped ammonia in an SNCR denitration process is characterized by comprising the steps of pneumatically mixing flue gas generated by SNCR denitration with an ammonia conversion catalyst at the temperature of 700 ℃ and 300 ℃, and carrying out catalytic oxidation reaction on ammonia to obtain the flue gas with ammonia removed.

6. The method for removing ammonia slip in an SNCR denitration process as claimed in claim 5, wherein said ammonia conversion catalyst comprises any one or combination of cobalt oxide, iron oxide, nickel oxide and manganese oxide, and said support is selected from any one or combination of titanium oxide, silicon oxide and aluminum oxide.

7. The method for removing ammonia slip in SNCR denitration process of claim 5, wherein the ammonia conversion catalyst is any one or more of iron-aluminum oxide catalyst, iron-titanium-silicon-aluminum oxide catalyst and catalyst obtained by treating inorganic solid waste containing the active component and carrier.

8. The method for removing ammonia escaping from an SNCR denitration process as claimed in claim 7, wherein the non-polar solid waste is selected from any one or more of red mud, blast furnace slag, various tailings and waste catalysts; the catalyst obtained by treating the inorganic solid waste containing the active component and the carrier is selected from any one or combination of more of an iron-based denitration catalyst prepared from red mud, a waste vanadium-tungsten-titanium denitration catalyst and a catalyst prepared from titanium-containing blast furnace slag.

9. The method for removing ammonia slip in an SNCR denitration process of claim 5, wherein the ammonia conversion catalyst is in the form of powder or particles.

10. The method for removing ammonia slip in an SNCR denitration process according to claim 9, wherein the particle size of the ammonia conversion catalyst is 1 to 100 μm when the ammonia conversion catalyst is in a powder form, and is 1 to 3mm when the ammonia conversion catalyst is in a particle form; the amount of the ammonia conversion catalyst added is 0.01-10kg per standard square of flue gas.

11. The method for removing ammonia escaped from SNCR denitration process according to any one of claims 5 to 10, wherein the flue gas and the ammonia conversion catalyst are pneumatically mixed by a pneumatic conveying device (9); spraying an ammonia conversion catalyst into an air outlet flue of the denitration reactor by using a pneumatic conveying device (9); the pneumatic conveying device (9) is selected from an air compressor; the contact time of the ammonia conversion catalyst with the flue gas generated by the denitration reactor is more than 0.01 s.

12. The method for removing ammonia escaped from SNCR denitration process according to any one of claims 5 to 10, wherein the flue gas and the ammonia conversion catalyst are pneumatically mixed by a pneumatic mixing device (8); introducing flue gas generated by a denitration reactor into a pneumatic mixing device (8) in which an ammonia conversion catalyst is placed; the pneumatic mixing device (8) is selected from an ebullated bed; the contact time of the ammonia conversion catalyst with the flue gas generated by the denitration reactor is more than 0.01 s.

13. The method for removing ammonia slip in the SNCR denitration process according to any one of claims 5 to 10, wherein the ammonia conversion catalyst in the ammonia-removed flue gas is collected for recycling; the ammonia conversion catalyst is recycled for 3-10 times; the ammonia conversion catalyst consists of a fresh ammonia conversion catalyst and a collected ammonia conversion catalyst in a mass ratio of 1:10 to 1: 20.

14. The method for removing ammonia slip in the SNCR denitration process according to any one of claims 5 to 10, wherein the method comprises:

spraying ammonia conversion catalyst powder with the particle size of 1-100 mu m into an air outlet flue of a denitration reactor of an SNCR (selective non catalytic reduction) denitration system by adopting a pneumatic conveying device (9), and mixing the ammonia conversion catalyst powder with flue gas at the temperature of 300-; or the flue gas generated by the denitration reactor of the SNCR denitration system is introduced into a pneumatic mixing device (8) which is provided with an ammonia conversion catalyst with the particle size of 1-100 mu m and the temperature of 300-700 ℃; after the ammonia conversion catalyst is mixed with the flue gas, ammonia is subjected to catalytic oxidation reaction to obtain the flue gas with ammonia removed, the adding amount of the ammonia conversion catalyst is 0.001-1kg/Nm in the flue gas through carrying out the year by year, and the retention time is more than 0.01 s; collecting the ammonia conversion catalyst in the ammonia-removed flue gas, and mixing the ammonia conversion catalyst with a fresh ammonia conversion catalyst according to the mass ratio of 10-20:1 to obtain the ammonia conversion catalyst.