WO2016112716A1

WO2016112716A1 - Method for optimizing sncr denitration system of garbage incinerator by adding anionic surfactant

Info

Publication number: WO2016112716A1
Application number: PCT/CN2015/091230
Authority: WO
Inventors: 李茂东; 杨波; 倪进飞; 马括; 薛峰; 王小聪; 张辉
Original assignee: 广州特种承压设备检测研究院
Priority date: 2015-01-13
Filing date: 2015-09-30
Publication date: 2016-07-21
Also published as: CN104645794A

Abstract

A method for optimizing a SNCR denitration system of a garbage incinerator by adding an anionic surfactant comprises adding the anionic surfactant into aqueous ammonia when the aqueous ammonia is diluted during the prior SNCR denitration of a garbage incinerator. The anionic surfactant and the aqueous ammonia solution are mixed and injected into the hearth, and then decomposed at high temperature to form -OH and other active free radicals, which can effectively ensure the efficiency and duration of the reaction between the atomized aqueous ammonia droplet and NOx in flue gas, improve the denitration efficiency of the integral SNCR system and broaden the interval of optimal reaction temperature without negatively influencing the steady combustion in the incinerator.

Description

Method for optimizing waste incinerator SNCR denitration system by adding anionic surfactant

Technical field

The invention relates to a denitration method for a waste incinerator SNCR, in particular to a method for adding an anionic surfactant to optimize a waste incinerator SNCR denitration system.

Background technique

Municipal solid waste incineration will produce pollutants such as nitrogen oxides, which will be adversely affected to the ecosystem if they are directly discharged into the environment without passing through the flue gas purification device. In conventional waste incineration plant operation mostly for processing denitration system installed in the flue gas NO _x in _the selective non-catalytic reduction (SNCR), but the actual operation of the load changing, complex smoke components, optimum reaction temperature fluctuation window The SNCR actual denitration efficiency deviates from the design value and the operating efficiency is low.

In order to solve the problem that the actual operating efficiency of SNCR is low and the optimal reaction temperature range is narrow, it is proposed to add an additive to the SNCR denitration reducing agent (urea or ammonia water) so that the reducing agent maintains a high denitration efficiency over a wide temperature range. to ensure that the reducing agent can be maintained for a longer reaction time and NO _x, _the NO _x concentration to ensure that the flue gas emissions to meet environmental requirements.

Such additives are mainly divided into three major categories: gases, alcohol esters and metal salts. The gas class includes CH ₄ , H ₂ , CO and a mixed gas thereof; the alcohol esters include ethanol, glycerol, methyl acetate and a mixture thereof; the metal salts include sodium hydroxide, sodium chloride, calcium magnesium acetate, Ammonium metavanadate, ammonium molybdate and mixtures thereof with various oxides. However, these additives have different defects in practical application. The use of gas storage has certain risks, and the safety needs to be improved. The effect of alcohol esters alone is not obvious, and the cost performance is not high; the effect of metal salts is obvious, but some Additives can cause different degrees of corrosion (such as NaCl) on boiler water walls and furnaces. Although it has been proposed to mix several additives into a composite synergist, for example, Patent No. CN 103816799A discloses a composite additive prepared by mixing calcium magnesium acetate, iron oxide, titanium oxide, manganese dioxide and cerium oxide; No. CN103768939A discloses a denitration synergist made of ammonium metavanadate, tungsten trioxide, molybdenum trioxide, ammonium molybdate and copper hydroxide. However, the various raw materials of the composite additives increase the difficulty of the technical process and are not conducive to its promotion in the waste incineration power station. The domestic waste incineration industry is developing rapidly and the environmental protection requirements are becoming more and more strict. It is of great practical significance to find a highly efficient SNCR denitration additive and optimize the SNCR denitration process.

Summary of the invention

In order to solve the above problems, in view of the deficiencies of the prior art, the present invention can establish a method for adding an anionic surfactant to optimize a waste incinerator SNCR (selective non-catalytic reduction) denitration system, in the ammonia dilution process In addition, adding a certain amount of anionic surfactant can greatly improve the SNCR denitration efficiency; The optimum reaction temperature range of ammonia water (680～1150°C) is widened, while the traditional method is 810～1030°C, which further promotes the denitration efficiency of SNCR and improves the overall efficiency of the system. The invention method is simple in process and convenient in operation.

It is an object of the present invention to provide a method of optimizing an incinerator SNCR denitration system by adding an anionic surfactant.

The technical solution adopted by the present invention is:

A method for adding an anionic surfactant to optimize a waste incinerator SNCR denitration system is: in the existing waste incinerator SNCR denitration process, when the ammonia water is diluted, an anionic surfactant is added to the ammonia water, and other operations are performed. Same as the existing SNCR denitration operation.

Further, the above anionic surfactant is used in an amount such that it has a final concentration of 0.5 to 2% by weight.

Further, the anionic surfactant is at least one selected from the group consisting of sodium laureth sulfate, sodium linear alkylbenzene sulfonate, and sodium polydithiodipropane sulfonate.

A method for adding an anionic surfactant to optimize a waste incinerator SNCR denitration system comprises the following steps:

1) mixing and diluting the soft water from the ammonia transport module and the soft water from the soft water delivery module in the dilution module;

2) At the same time, the required dose of anionic surfactant is transferred to the dilution module described in step 1) under the control of the calculation module, so that the ammonia water is added with an anionic surfactant during the dilution process; after mixing, an ammonia water mixed solution is obtained;

3) The above ammonia water mixed solution is sent to the furnace and flue gas for denitration reaction under the control of the ammonia injection module by compressed air.

Further, the temperature of the aqueous ammonia mixed solution in the step 2) is 20 to 30 °C.

Further, the ammonia water mass fraction in the aqueous ammonia mixed solution is 15 to 30% by weight.

Further, the anionic surfactant in the above aqueous ammonia mixed solution has an excellent mass fraction of 0.5 to 20% by weight.

Further, the temperature of the compressed air in the step 3) is 10 to 35 °C.

Further, the temperature of the flue gas in the step 3) is 700 to 1100 °C.

The beneficial effects of the invention are:

1) In the present invention, the efficiency of the waste incinerator SNCR denitration system is effectively improved. When the SNCR reducing agent is diluted with ammonia, a certain amount of low-cost anionic surfactant is added, and the configuration process is simple, which overcomes the disadvantages of low efficiency of the existing SNCR denitration technology or complicated and expensive configuration of the reducing agent synergist, and effectively improves the denitration of SNCR ammonia water. Efficiency, widening the optimal reaction temperature range (680~1150 °C), improving the overall efficiency of the system; and not stabilizing the combustion zone of the incinerator Come to the negative impact.

2) In the present invention, an anionic surfactant and an aqueous ammonia solution injected into the furnace, -OH and other active radical decomposition at high temperatures, the reaction efficiency and effective protection of atomized water droplets ammonia time of NO _x in flue gases, to improve The overall SNCR system denitration efficiency and widening the optimal reaction temperature range without negatively affecting the stable combustion of the incinerator. Compared with the existing traditional SNCR denitration composite additive, the method of the invention has simple process, single additive and low price, and is an effective method for improving the efficiency of the SNCR denitration system of the waste incinerator, and has a wide application prospect.

3) The invention uses the anionic surfactant to contain an organic functional group and a metal compound, and has the effect of the currently used SCNR additive such as an alcohol ester and a metal salt. Therefore, an anionic surfactant is selected to have a larger effect than these additives. Advantage. The anionic surface active additive used in the present invention is sodium laureth sulfate CH ₃ (CH ₂ ) ₁₀ CH ₂ (OCH ₂ CH ₂ ) ₃ OSO ₃ Na, hereinafter referred to as SLES; sodium linear alkylbenzene sulfonate CH ₃ (CH ₂ ) ₁₁ C ₆ H ₄ SO ₃ H, abbreviated as LAS; sodium polydithiodipropane sulfonate CH ₃ (CH ₂ ) ₁₀ CH ₂ OSO ₃ Na, abbreviated as SPS. These anionic surfactants have large yields and low prices. Adding to the SNCR reducing agent does not require an initial configuration process, and only needs to be added when the reducing agent is diluted, and the process is simple, so the application prospect is broad.

4) The present invention firstly proposes a method for adding an anionic surfactant to optimize the SNCR denitration system of a waste incinerator; no related reports have been reported before the addition of an anionic surfactant to the SNCR reducing agent to optimize the denitration effect.

detailed description

The present invention will be further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto, and the process parameters not specifically noted may be referred to conventional techniques.

Example 1: Method for optimizing waste incinerator SNCR denitration system by adding anionic surfactant

2) at the same time, the required dose of sodium laurate polyoxyethylene ether sulfate (SLES) is transferred under the control of the calculation module to the dilution module described in step 1) to add anionic surfactant to the aqueous ammonia during the dilution process; After mixing, an ammonia water mixed solution is obtained, the temperature is 28 ° C, the mass fraction of ammonia water in the mixed solution is 18 wt%, and the mass fraction of SLES is 0.5 wt%;

3) The above ammonia water mixed solution is sent to the furnace and the flue gas for denitration reaction under the control of the ammonia injection module by compressed air (temperature is 21 ° C); 6 sets of experiments are respectively set up, so that the garbage is incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results shown in Table 1) each before and after denitration.

Comparative Experiment:

In the comparative experiment, the existing SCNR denitration method is adopted, that is, the anionic surfactant SLES is not added, and other operation methods and condition parameters are the same as in the first embodiment, and six sets of experiments are also set, so that the garbage is incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results shown in Table 1) each before and after denitration.

Table 1 Effect of different SNCR denitration methods on denitrification of waste incineration tobacco

It can be seen from Table 1 that the SNCR denitration method of the waste incinerator optimized by the addition of an anionic surfactant has significantly improved the denitration rate of the flue gas. At 900 ° C, the denitration efficiency reaches 72.4%, and the existing conventional SNCR denitration The method can only reach 58.2%. The temperature at which the denitration efficiency reaches 50% is the optimal reaction temperature range of SNCR ammonia denitration (the same below). After the detection, the optimal reaction temperature range of ammonia denitration in the method of the invention is 710-1100 °C, and the optimal reaction of the existing SNCR denitration method is obtained. The temperature range is 850~1010 °C. It can be seen that the invention can also widen the optimal reaction temperature range, further promote the denitration efficiency of the SNCR and improve the overall efficiency of the system.

Example 2: Method for optimizing waste incinerator SNCR denitration system by adding anionic surfactant

2) at the same time, the required dose of sodium laurate polyoxyethylene ether sulfate (SLES) is transferred under the control of the calculation module to the dilution module described in step 1) to add anionic surfactant to the aqueous ammonia during the dilution process; After mixing, an ammonia water mixed solution is obtained, the temperature is 28 ° C, the mass fraction of ammonia water in the mixed solution is 18 wt%, and the mass fraction of SLES is 1 wt%;

3) The above ammonia water mixed solution is sent to the furnace and the flue gas for denitration reaction under the control of the ammonia injection module by compressed air (temperature is 21 ° C); 6 sets of experiments are respectively set up, so that the garbage is incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results in Table 2) before and after each denitration.

Comparative Experiment:

In the comparative experiment, the existing SCNR denitration method is adopted, that is, the anionic surfactant SLES is not added, and other operation methods and condition parameters are the same as in the second embodiment, and six sets of experiments are also set, so that the garbage is incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results in Table 2) before and after each denitration.

Table 2 Effect of different SNCR denitration methods on denitrification of waste incineration tobacco

It can be seen from Table 2 that after adding an anionic surfactant of 1 wt% mass fraction, the denitration efficiency of the SNCR ammonia water of the invention is obviously improved, and the denitration efficiency reaches 74.8% at 900 °C. After adding 1% by mass of anionic surfactant, the optimal reaction temperature range is extended from 850 to 1010 °C to 705 to 1100 °C, which improves the overall efficiency of the system.

Example 3: Method for optimizing waste incinerator SNCR denitration system by adding anionic surfactant

2) at the same time, the required dose of sodium laurate polyoxyethylene ether sulfate (SLES) is transferred under the control of the calculation module to the dilution module described in step 1) to add anionic surfactant to the aqueous ammonia during the dilution process; After mixing, an ammonia water mixed solution is obtained, the temperature is 28 ° C, the mass fraction of ammonia water in the mixed solution is 18 wt%, and the mass fraction of SLES is 2 wt%;

3) The above ammonia water mixed solution is sent to the furnace and the flue gas for denitration reaction under the control of the ammonia injection module by compressed air (temperature is 21 ° C); 6 sets of experiments are respectively set up, so that the garbage is incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results in Table 3) before and after each denitration.

Comparative Experiment:

In the comparative experiment, the existing SCNR denitration method is adopted, that is, the anionic surfactant SLES is not added, and other operation methods and condition parameters are the same as in the third embodiment, and six sets of experiments are also set, so that the garbage is incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results in Table 3) before and after each denitration.

Table 3 Effect of Different SNCR Denitration Methods on Denitrification of Waste Incineration Smoke

It can be seen from Table 3 that the addition of 2% by mass of anionic surfactant has greatly improved the denitration efficiency of the SNCR ammonia water of the present invention, and the denitration efficiency reached 80.3% at 900 °C. After adding 2wt% mass fraction of anionic surfactant, the optimal reaction temperature range is extended from 850 to 1010 °C to 690-1110 °C, which improves the overall efficiency of the system.

Example 4: Method for optimizing waste incinerator SNCR denitration system by adding anionic surfactant

2) at the same time, the required dose of sodium laurate polyoxyethylene ether sulfate (SLES) is transferred under the control of the calculation module to the dilution module described in step 1) to add anionic surfactant to the aqueous ammonia during the dilution process; After mixing, an ammonia water mixed solution is obtained, the temperature is 25 ° C, the mass fraction of ammonia water in the mixed solution is 25 wt%, and the mass fraction of SLES is 1 wt%;

3) The above ammonia water mixed solution is sent to the furnace and the flue gas for denitration reaction under the control of the ammonia injection module by compressed air (temperature is 21 ° C); 6 sets of experiments are respectively set up, so that the garbage is incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results in Table 4) before and after each denitration.

Comparative Experiment:

In the comparative experiment, the existing SCNR denitration method was adopted, that is, the anionic surfactant SLES was not added, and other operation methods and condition parameters were the same as in Example 4. Six sets of experiments were also set up, so that the garbage was incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results in Table 4) before and after each denitration.

Table 4 Effect of Different SNCR Denitration Methods on Denitrification of Waste Incineration Smoke

It can be seen from Table 4 that the SNCR ammonia denitration efficiency of the present invention is greatly improved after adding an anionic surfactant of 1 wt% mass fraction, and the denitration efficiency reaches 76.5% at 900 °C. After adding 1 wt% mass fraction of anionic surfactant, the optimal reaction temperature range is extended from 825 to 1010 °C to 690-1120 °C, which improves the overall efficiency of the system.

Example 5: Method for optimizing waste incinerator SNCR denitration system by adding anionic surfactant

2) at the same time, the required dose of sodium laurate polyoxyethylene ether sulfate (SLES) is transferred under the control of the calculation module to the dilution module described in step 1) to add anionic surfactant to the aqueous ammonia during the dilution process; After mixing, an ammonia water mixed solution is obtained, the temperature is 25 ° C, the mass fraction of ammonia water in the mixed solution is 25 wt%, and the mass fraction of SLES is 2 wt%;

3) The above ammonia water mixed solution is sent to the furnace and the flue gas for denitration reaction under the control of the ammonia injection module by compressed air (temperature is 21 ° C); 6 sets of experiments are respectively set up, so that the garbage is incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results shown in Table 5) before and after each denitration.

Comparative Experiment:

In the comparative experiment, the existing SCNR denitration method is adopted, that is, the anionic surfactant SLES is not added, and other operation methods and condition parameters are the same as in the case of the fifth embodiment, and six sets of experiments are also set, so that the garbage is incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results shown in Table 5) before and after each denitration.

Table 5 Effect of Different SNCR Denitration Methods on Denitrification of Waste Incineration Smoke

It can be seen from Table 5 that the addition of 2% by mass of anionic surfactant has greatly improved the denitration efficiency of the SNCR ammonia water of the present invention, and the denitration efficiency reached 84.6% at 900 °C. After adding 2% by mass of anionic surfactant, the optimal reaction temperature range is extended from 825 to 1010 ° C to 680 to 1150 ° C, which improves the overall efficiency of the system.

Example 6: Method for optimizing waste incinerator SNCR denitration system by adding anionic surfactant

2) at the same time, the required dose of sodium laurate polyoxyethylene ether sulfate (SLES) is transferred under the control of the calculation module to the dilution module described in step 1) to add anionic surfactant to the aqueous ammonia during the dilution process; After mixing, an ammonia water mixed solution is obtained, the temperature is 25 ° C, the mass fraction of ammonia water in the mixed solution is 30 wt%, and the mass fraction of SLES is 1 wt%;

3) The above ammonia water mixed solution is sent to the furnace and the flue gas for denitration reaction under the control of the ammonia injection module by compressed air (temperature is 21 ° C); 6 sets of experiments are respectively set up, so that the garbage is incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results in Table 6) before and after each denitration.

Comparative Experiment:

In the comparative experiment, the existing SCNR denitration method was adopted, that is, the anionic surfactant SLES was not added, and other operation methods and condition parameters were the same as in Example 6. Six sets of experiments were also set up, so that the garbage was incinerated at different temperatures, so that The generated flue gas temperatures were 600 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, and 1100 ° C, respectively. It was detected by the flue gas analyzer concentration of NO _x in the flue gas (results in Table 6) before and after each denitration.

Table 6 Effect of Different SNCR Denitration Methods on Denitrification of Waste Incineration Smoke

It can be seen from Table 6 that after adding an anionic surfactant of 1 wt% mass fraction, the denitration efficiency of the SNCR ammonia water of the present invention is greatly improved, and the denitration efficiency reaches 81.2% at 900 °C. After adding 2wt% mass fraction of anionic surfactant, the optimal reaction temperature range is extended from 810 to 1030 °C to 680-1130 °C, which improves the overall efficiency of the system.

It can be seen from the above embodiments that the method for adding an anionic surfactant to optimize the waste incinerator SNCR denitration system of the present invention significantly improves the SNCR ammonia denitration efficiency and broadens the optimal reaction temperature range.

Example 7: Method for optimizing waste incinerator SNCR denitration system by adding anionic surfactant

2) at the same time, the required dose of sodium linear alkylbenzene sulfonate (LAS) is transferred under the control of the calculation module to the dilution module described in step 1) to add anionic surfactant to the aqueous ammonia during the dilution process; After mixing, an ammonia water mixed solution is obtained, the temperature is 30 ° C, the mass fraction of ammonia water in the mixed solution is 15 wt%, and the mass fraction of LAS is 2 wt%;

3) The above ammonia water mixed solution is sent to the furnace and the flue gas for denitration reaction under the control of the ammonia injection module by compressed air (temperature: 10 ° C); wherein the flue gas temperature is 900 ° C.

Example 8: Method for optimizing waste incinerator SNCR denitration system by adding anionic surfactant

2) at the same time, the required dose of sodium polydithiodipropane sulfonate (SPS) is transferred under the control of the calculation module to the dilution module described in step 1) to add anionic surfactant to the aqueous ammonia during the dilution process; After mixing, an ammonia water mixed solution is obtained, the temperature is 20 ° C, the mass fraction of ammonia water in the mixed solution is 30 wt%, and the mass fraction of SPS is 0.5 wt%;

3) The above ammonia water mixed solution is sent to the furnace and flue gas for denitration reaction under the control of the ammonia injection module by compressed air (temperature: 35 ° C); wherein the flue gas temperature is 900 ° C.

It will be readily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not used. Any modifications, equivalent substitutions and improvements made within the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims

A method for adding an anionic surfactant to optimize a waste incinerator SNCR denitration system, characterized in that: in the existing waste incinerator SNCR denitration process, an anionic surfactant is added to the ammonia water when the ammonia water is diluted, and other operations are performed. Same as the existing SNCR denitration operation.
The method for optimizing an incinerator SNCR denitration system according to claim 1, wherein the anionic surfactant is used in an amount of from 0.5 to 2% by weight.
The method for optimizing an incinerator SNCR denitration system by adding an anionic surfactant according to claim 1 or 2, wherein the anionic surfactant is selected from the group consisting of sodium laureth sulfate and linear alkane. At least one of sodium benzene sulfonate and sodium polydithiodipropane sulfonate.
A method for adding an anionic surfactant to optimize a waste incinerator SNCR denitration system, comprising: the following steps:

1) mixing and diluting the soft water from the ammonia transport module and the soft water from the soft water delivery module in the dilution module;

2) At the same time, the required dose of anionic surfactant is transferred to the dilution module described in step 1) under the control of the calculation module, so that the ammonia water is added with an anionic surfactant during the dilution process; after mixing, an ammonia water mixed solution is obtained;

3) The above ammonia water mixed solution is sent to the furnace and flue gas for denitration reaction under the control of the ammonia injection module by compressed air.
The method for optimizing an incinerator SNCR denitration system according to claim 4, wherein the temperature of the aqueous ammonia mixed solution in step 2) is 20 to 30 °C.
The method for optimizing an incinerator SNCR denitration system by adding an anionic surfactant according to claim 4 or 5, characterized in that the ammonia water mass fraction in the ammonia water mixed solution is 15 to 30 wt%.
The method for optimizing an incinerator SNCR denitration system by adding an anionic surfactant according to claim 4, wherein the anionic surfactant in the aqueous ammonia mixed solution has an excellent mass fraction of 0.5 to 20% by weight.
A method for optimizing a waste incinerator SNCR denitration system by adding an anionic surfactant according to claim 4 or 7, wherein the anionic surfactant is selected from the group consisting of sodium laureth sulfate and linear alkane. At least one of sodium benzene sulfonate and sodium polydithiodipropane sulfonate.
The method of claim 4, wherein the temperature of the compressed air in the step 3) is 10 to 35 ° C.
A method for optimizing a waste incinerator SNCR denitration system according to claim 4, wherein the temperature of the flue gas in step 3) is 700 to 1100 °C.