CN107485988B - SCR denitration method - Google Patents
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- CN107485988B CN107485988B CN201710978973.6A CN201710978973A CN107485988B CN 107485988 B CN107485988 B CN 107485988B CN 201710978973 A CN201710978973 A CN 201710978973A CN 107485988 B CN107485988 B CN 107485988B
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D53/34—Chemical or biological purification of waste gases
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- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
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Abstract
the invention belongs to the field of denitration, and particularly relates to an SCR denitration method which comprises the following steps of a) enabling flue gas to flow through a flue of a boiler, wherein first, second and third hydrogen peroxide solution injection points are sequentially arranged in front of, in the middle of and behind a section of the flue corresponding to a final-stage superheater, the hydrogen peroxide solution injection condition of each hydrogen peroxide solution injection point is controlled according to the temperature of the flue gas flowing through each hydrogen peroxide solution injection point, oxidized flue gas is obtained after the flue gas is sprayed with the hydrogen peroxide solution, b) washing is carried out on the oxidized flue gas through a washing solution to obtain the denitration flue gas, and H 2 O 2, organic sulfoxide or sulfite are added into the washing solution.
Description
Technical Field
The invention belongs to the field of denitration, and particularly relates to an SCR denitration method.
Background
NO x is a main atmospheric pollutant which can cause photochemical pollution with hydrocarbon under the action of strong light, and NO x discharged into the atmosphere is a main cause of acid rain and seriously harms the ecological environment.
the denitration method adopted by a common thermal power plant at present is SCR (selective catalytic reduction) denitration, the emission of NO x exceeds the standard when the flue gas temperature does not reach the SCR input condition during ignition, the total emission of NO x is reduced by increasing the denitration ammonia injection amount after a boiler has the denitration input condition, and the denitration daily average value is ensured to be qualified, when the coal-fired power plant is under low load, a denitration system cannot be put into operation due to the fact that the flue gas temperature at an SCR inlet is lower than the normal working temperature window of a catalyst, and the ultralow emission requirement cannot be met, the most basic condition of using SCR denitration operation is that the flue gas temperature needs to reach the lowest working temperature of the catalyst, even if a low-temperature catalyst is used, a process for increasing the flue gas temperature is needed, the oxidation denitration method does not need to use the catalyst, the strong oxidant is used for activating NO to oxidize NO, so that NO with high valence state NO 2, N7O 5 and the like can be dissolved in water to generate HNO 2 and HNO 3, the low-load HNO 3 can be used in the ignition and denitration stages, the existing oxidation denitration process, after a draught fan is generally, the boiler is added, the energy consumption of the NOx is poorer, the NOx is needed to be adjusted, the energy consumption of the NOx is more than that the NOx absorption of other NOx absorption of the NOx absorption of NaOH is absorbed by the NaOH solution, the NaOH solution is absorbed by the NaOH solution.
Disclosure of Invention
in view of the above, it is an object of the present invention to provide an SCR denitration method having a high denitration efficiency during ignition and low load operation of a boiler.
The invention provides an SCR denitration method, which comprises the following steps:
a) the flue gas flows through the boiler flue; the section of the flue between the final superheater and the upper superheater is internally provided with a first hydrogen peroxide solution injection point, the section of the flue corresponding to the final superheater is internally provided with a second hydrogen peroxide solution injection point, and the section of the flue between the final superheater and the economizer is provided with a third hydrogen peroxide solution injection point;
When the temperature of the flue gas at the first hydrogen peroxide solution injection point is within a preset temperature range, spraying hydrogen peroxide solution to the flue gas at the first hydrogen peroxide solution injection point; when the flue gas temperature of the first hydrogen peroxide solution injection point is out of the preset temperature range, stopping injecting the hydrogen peroxide solution at the first hydrogen peroxide solution injection point;
When the temperature of the flue gas at the second aqueous solution injection point is within a preset temperature range, spraying an aqueous solution of hydrogen peroxide to the flue gas at the second aqueous solution injection point; when the temperature of the flue gas at the second hydrogen peroxide solution injection point is out of the preset temperature range, stopping injecting the hydrogen peroxide solution at the second hydrogen peroxide solution injection point;
When the temperature of the flue gas at the third hydrogen peroxide solution injection point is within the preset temperature range, spraying the hydrogen peroxide solution to the flue gas at the third hydrogen peroxide solution injection point; when the flue gas temperature of the third hydrogen peroxide solution injection point is lower than the preset temperature range, the third hydrogen peroxide solution injection point stops injecting the hydrogen peroxide solution; when the flue gas temperature of the third hydrogen peroxide solution injection point is higher than the preset temperature range, stopping injecting the hydrogen peroxide solution at all hydrogen peroxide solution injection points;
Spraying hydrogen peroxide solution on the flue gas to obtain oxidized flue gas;
b) Washing the oxidized flue gas with a washing liquid to obtain the denitrated flue gas, wherein the washing liquid is added with H 2 O 2, organic sulfoxide or sulfite.
Preferably, the preset temperature ranges of the first, second and third hydrogen peroxide solution injection points are all 400-500 ℃.
Preferably, the second aqueous hydrogen peroxide solution injection point is arranged at the middle position of the section of the flue corresponding to the final stage superheater.
Preferably, along the flowing direction of the flue gas, the distance between the first hydrogen peroxide solution injection point and the starting end of the final-stage superheater is 2-5 m, and the distance between the third hydrogen peroxide solution injection point and the tail end of the final-stage superheater is 1-12 m.
Preferably, the last stage superheater is located below the turn-around chamber of the flue.
Preferably, the concentration of H 2 O 2 in the hydrogen peroxide solution is 20-30 wt%, and the molar ratio of the H 2 O 2 injection amount of each hydrogen peroxide solution injection point to the NO x content in the flue gas when the flue gas flows through the injection point is 2-3.
Preferably, the addition amount of the H 2 O 2, the organic sulfoxide or the sulfite in the washing liquid is more than 0.1 mol/L.
Preferably, the pH value of the washing liquid is 3-6.
Preferably, the washing mode is spraying, and the liquid-gas ratio of the washing liquid to the oxidized flue gas during washing is 3-8L/m 3.
2 2 x 2 2 2 x x x 2 2 xThe method comprises the following steps of a) enabling flue gas to flow through a flue of a boiler, wherein a first hydrogen peroxide solution injection point is arranged in a section of the flue between a last superheater and an upper superheater, a second hydrogen peroxide solution injection point is arranged in a section of the flue corresponding to the last superheater, a third hydrogen peroxide solution injection point is arranged in a section of the flue between the last superheater and an economizer, when the temperature of the flue at the first hydrogen peroxide solution injection point is within a preset temperature range, the hydrogen peroxide solution is injected into the flue gas at the first hydrogen peroxide solution injection point, when the temperature of the flue gas at the first hydrogen peroxide solution injection point is outside the preset temperature range, the hydrogen peroxide solution injection point stops injecting the hydrogen peroxide solution, when the temperature of the flue gas at the second hydrogen peroxide solution injection point is within a preset temperature range, the hydrogen peroxide solution injection point is injected into the flue gas, when the temperature of the flue gas at the second hydrogen peroxide solution injection point is within a low-load temperature range, the hydrogen peroxide solution injection point is stopped, when the temperature of the flue gas at the second hydrogen peroxide solution injection point is within a preset temperature range, the second hydrogen peroxide solution injection point is NO 2, the temperature of the hydrogen peroxide solution injection point, the hydrogen peroxide solution injection point is reached, the temperature of the temperature range, the temperature of the hydrogen peroxide solution injection point, the flue gas is reached, the temperature range, the hydrogen peroxide solution injection point, the temperature of the flue gas is reached, the temperature range is reached, the temperature range reached by the temperature range of the temperature range, the temperature range of the range, the temperature range of the range, the range of the temperature range, the temperature range of the range.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a schematic diagram showing the position of the point of injection of the aqueous hydrogen peroxide solution according to the embodiment of the present invention.
Detailed Description
the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides an SCR denitration method, which comprises the following steps:
a) The flue gas flows through the boiler flue; the section of the flue between the final superheater and the upper superheater is internally provided with a first hydrogen peroxide solution injection point, the section of the flue corresponding to the final superheater is internally provided with a second hydrogen peroxide solution injection point, and the section of the flue between the final superheater and the economizer is provided with a third hydrogen peroxide solution injection point;
When the temperature of the flue gas at the first hydrogen peroxide solution injection point is within a preset temperature range, spraying hydrogen peroxide solution to the flue gas at the first hydrogen peroxide solution injection point; when the flue gas temperature of the first hydrogen peroxide solution injection point is out of the preset temperature range, stopping injecting the hydrogen peroxide solution at the first hydrogen peroxide solution injection point;
When the temperature of the flue gas at the second aqueous solution injection point is within a preset temperature range, spraying an aqueous solution of hydrogen peroxide to the flue gas at the second aqueous solution injection point; when the temperature of the flue gas at the second hydrogen peroxide solution injection point is out of the preset temperature range, stopping injecting the hydrogen peroxide solution at the second hydrogen peroxide solution injection point;
When the temperature of the flue gas at the third hydrogen peroxide solution injection point is within the preset temperature range, spraying the hydrogen peroxide solution to the flue gas at the third hydrogen peroxide solution injection point; when the flue gas temperature of the third hydrogen peroxide solution injection point is lower than the preset temperature range, the third hydrogen peroxide solution injection point stops injecting the hydrogen peroxide solution; when the flue gas temperature of the third hydrogen peroxide solution injection point is higher than the preset temperature range, stopping injecting the hydrogen peroxide solution at all hydrogen peroxide solution injection points;
Spraying hydrogen peroxide solution on the flue gas to obtain oxidized flue gas;
b) Washing the oxidized flue gas with a washing liquid to obtain the denitrated flue gas, wherein the washing liquid is added with H 2 O 2, organic sulfoxide or sulfite.
In the invention, firstly, a hydrogen peroxide solution injection point is arranged on a boiler flue. The boiler flue is sequentially provided with a plurality of stages of superheaters along the flowing direction of flue gas, and the downstream of the last stage of superheater is also provided with an economizer. In one embodiment provided by the invention, the boiler flue is provided with a diversion chamber, and the final stage superheater is positioned below the diversion chamber of the flue, namely on the vertical flue. In one embodiment provided by the invention, along the flue gas flowing direction, the flue length corresponding to the last stage superheater section is 8-15 m, and specifically may be 10m, 11m, 12m, 13m or 14 m. In the present invention, the first aqueous hydrogen peroxide solution injection point is located in a section of the flue between the corresponding last-stage superheater and the preceding-stage superheater. In one embodiment of the invention, the distance between the first aqueous solution of hydrogen peroxide spraying point and the beginning end of the last stage of superheater is 2-5 m, and specifically may be 2m, 2.5m, 3m, 3.5m, 4m, 4.5m or 5 m. In the present invention, the second aqueous hydrogen peroxide solution injection point is located in a section of the flue corresponding to the final stage superheater. In one embodiment provided by the invention, the second aqueous hydrogen peroxide solution injection point is arranged at the middle position of the section of the flue corresponding to the final stage superheater. In the present invention, the third aqueous hydrogen peroxide solution injection point is located in a section of the flue corresponding to between the final stage superheater and the economizer. In one embodiment provided by the invention, the distance between the third hydrogen peroxide solution injection point and the end of the final-stage superheater is 1-12 m, and specifically may be 1m, 2m, 3m, 4m, 5m, 6m, 7m, 8m, 9m, 10m, 11m or 12 m. In the invention, each hydrogen peroxide solution injection point is provided with a plurality of spray guns. In one embodiment provided by the invention, each spray gun is provided with an automatic telescopic device which can automatically enter or exit from a working state according to signals, and each group of spray guns is also provided with a flow regulating valve for regulating the injection quantity. In the invention, each hydrogen peroxide solution injection point is also provided with a temperature measuring device for monitoring the temperature of the flue gas.
in the invention, when the flue gas flows through the three hydrogen peroxide solution injection points, whether the hydrogen peroxide solution is injected into the flue gas is regulated and controlled according to the temperature of the flue gas at the injection points, and the specific control strategy comprises the following steps:
When the temperature of the flue gas at the first hydrogen peroxide solution injection point is within a preset temperature range, spraying hydrogen peroxide solution to the flue gas at the first hydrogen peroxide solution injection point; and when the flue gas temperature of the first hydrogen peroxide solution injection point is out of the preset temperature range, stopping injecting the hydrogen peroxide solution at the first hydrogen peroxide solution injection point. Wherein the preset temperature range is preferably 400-500 ℃.
When the temperature of the flue gas at the second aqueous solution injection point is within a preset temperature range, spraying an aqueous solution of hydrogen peroxide to the flue gas at the second aqueous solution injection point; and when the temperature of the flue gas at the second aqueous solution injection point is out of the preset temperature range, stopping injecting the aqueous solution by the second aqueous solution injection point. Wherein the preset temperature range is preferably 400-500 ℃.
when the temperature of the flue gas at the third hydrogen peroxide solution injection point is within the preset temperature range, spraying the hydrogen peroxide solution to the flue gas at the third hydrogen peroxide solution injection point; when the flue gas temperature of the third hydrogen peroxide solution injection point is lower than the preset temperature range, the third hydrogen peroxide solution injection point stops injecting the hydrogen peroxide solution; when the flue gas temperature of the third hydrogen peroxide solution injection point is higher than the preset temperature range, all hydrogen peroxide solution injection points stop injecting the hydrogen peroxide solution, at the moment, the flue gas temperature is higher, the temperature requirement of SCR (selective catalytic reduction) denitration is completely met, and the SCR is used for denitration. Wherein the preset temperature range is preferably 400-500 ℃.
x x 2 2 2 2 2 2 x 2 2 2 2 2 2 2 2 3 2 x 3 3 3 3 x 3 3 3 3 2 2 2 2 x xIn the invention, after the flue gas is sprayed with hydrogen peroxide solution, hydrogen peroxide solution is cracked and reacts with NO in the flue gas to obtain oxidized flue gas containing high-valence soluble NO, wherein the cracking reaction formula of the hydrogen peroxide solution is H O → 2OH, H O + OH → HO + H O, and the reaction formula is NO + HO → NO + OH, NO + H O → NO + H O, 2NO +3H O → 2HNO +2H O, the flow rate of the flue gas in a flue and the concentration of NO in the flue gas are not particularly limited, in one embodiment provided by the invention, the flow rate of the flue gas is 50-300 Nm/s, specifically 95.7 Nm/s, 202.3 Nm/s or 2H O, in one embodiment provided by the invention, the concentration of NO in the flue gas is 200-500 mg/Nm, specifically 280, 400Nm or 480, in the invention, the concentration of H O in the hydrogen peroxide solution is preferably 20-30 wt%, specifically 20-21% by weight, and the injection ratio of the H2 to 27% by weight of the flue gas is preferably 27%, and the injection ratio of the hydrogen peroxide solution is more than 27% by weight.
In the invention, the spraying condition of the hydrogen peroxide solution is controlled by a controller, a PLC (programmable logic controller) of a main stream inlet of the power industry can be selected, the controller obtains the flow rate of smoke, NO x concentration, temperature and the like through communication or hard wiring, wherein, a plurality of measuring points need to establish bidirectional communication connection with a DCS (distributed control system) of a power station, the connection is based on a serial port MODUBUS or TCPMODBUS protocol.
The denitration flue gas is obtained by washing oxidized flue gas containing high-valence soluble NO x with washing liquid after the flue gas is oxidized, wherein the washing liquid is added with H 2 O 2, organic sulfoxide or sulfite, the organic sulfoxide preferably comprises one or more of thionyl chloride, dimethyl sulfoxide and diphenyl sulfoxide, the sulfite preferably comprises sodium sulfite and/or potassium sulfite, the addition amount of H 2 O 2, the organic sulfoxide or sulfite in the washing liquid is preferably not less than 0.06mol/L, more preferably 0.06mol/L to 0.12mol/L, and most preferably 0.1 mol/L.
The method is based on temperature data, and in the starting process or the low-load operation process of the boiler, the hydrogen peroxide solution is sprayed in a subarea real-time control mode according to the optimal temperature interval of the hydrogen peroxide solution for oxidizing NO x in the flue gas, the H 2 O 2 in the hydrogen peroxide solution is excited by the high temperature of the flue gas to generate strong oxidizing groups such as OH, HO 2 and the like, so that NO x in the flue gas is quickly oxidized to generate high-valence soluble NOx, then the high-valence soluble NO x is absorbed by the washing liquid through washing of the washing liquid, and the high-valence soluble NO x is inhibited from being reduced into NO again through adding organic sulfoxide, sulfite or H 2 O 2 in the washing liquid, so that the method provided by the invention keeps higher denitration efficiency.
for the sake of clarity, the following examples are given in detail.
Example 1
Referring to fig. 1, a hydrogen peroxide solution injection point is set, and fig. 1 is a schematic diagram of a setting position of the hydrogen peroxide solution injection point according to an embodiment of the present invention. In fig. 1, 1 is a first aqueous hydrogen peroxide solution injection point, 2 is a second aqueous hydrogen peroxide solution injection point, 3 is a third aqueous hydrogen peroxide solution injection point, 4 is a final-stage superheater, 5 is an economizer, 6 is a turn chamber, and 7 is an SCR denitration reactor.
In the present embodiment, the last stage superheater 4 is disposed below the boiler turn chamber 6. The cross section size of the superheater flue in the direction vertical to the flue gas flow is 10 multiplied by 20m, the first hydrogen peroxide solution injection point is 2.5m before the starting end of the last-stage superheater, the second hydrogen peroxide solution injection point is in the middle of the last-stage superheater, and the third hydrogen peroxide solution injection point is 12m behind the starting end of the last-stage superheater (2 m behind the tail end of the superheater).
The specific denitration process comprises the following steps:
3 x 3 2 2during ignition and low load operation of the boiler, when the temperature of flue gas at a first aqueous solution injection point 1 reaches 400 ℃, a spray gun at the first aqueous solution injection point 1 is thrown in to inject an aqueous solution of dioxygen, when the temperature of flue gas at a second aqueous solution injection point 2 reaches 400 ℃, a spray gun at the second aqueous solution injection point 2 is thrown in to inject an aqueous solution of dioxygen, if the temperature of flue gas at the first aqueous solution injection point 1 exceeds 500 ℃, the spray gun at the first aqueous solution injection point 1 is withdrawn, if the temperature of flue gas at the first aqueous solution injection point 1 does not exceed 500 ℃, the spray gun at the first aqueous solution injection point 1 is continued to inject the aqueous solution of dioxygen, when the temperature of flue gas at a third aqueous solution injection point 3 reaches 400 ℃, a spray gun at a third aqueous solution injection point 3 is thrown in to inject the aqueous solution of dioxygen, if the temperature of flue gas at the second aqueous solution injection point 2 exceeds 500 ℃, the spray gun at the second aqueous solution injection point 2 injects the aqueous solution, if the temperature of flue gas at the second aqueous solution injection point 2 exceeds 500 ℃, the spray gun at the second aqueous solution injection point 2 is not injected, the spray gun is not injected, the flue gas injection point 2, the flue gas injection point injection temperature of the NOx injection point 2 is not higher than 3627% NOx injection temperature of the NOx injection point, if the flue gas injection of the NOx injection point 2, the NOx injection of the NOx injection point injection system is not injected, the NOx injection point, the NOx injection of the NOx injection system is not injected, the NOx injection point injection system, the NOx injection point injection temperature of the NOx injection point is not injected, the NOx injection.
Spraying hydrogen peroxide solution on a spraying point to oxidize the flue gas, and then washing the flue gas by using washing liquid in a countercurrent spray tower, wherein the tower diameter of the spray tower is 13.7m, the flue gas amount is 269.8Nm 3/s, the tower temperature is 40-55 ℃, the washing liquid is calcium hydroxide slurry, the pH is controlled to be 3-6, sodium sulfite is added into the washing liquid, the addition amount is about 0.1mol/L, the residence time of the flue gas in the tower is about 6s, the spraying amount of the washing liquid is about 1350L/s, the denitrated flue gas is obtained at an air outlet of the spray tower, and the NO x content of the denitrated flue gas is monitored, so that the NO x concentration is about 90mg/Nm 3.
Therefore, the denitration method provided by the embodiment can ensure that the seed boiler has a better denitration effect during ignition and low-load operation.
Example 2
With reference to the arrangement shown in fig. 1, the point of injection of the hydrogen peroxide solution is arranged, in this embodiment, with the last superheater stage 4 arranged below the boiler turn-around chamber 6. The cross-sectional dimension of the superheater flue in the direction vertical to the flue gas flow is 5.8 multiplied by 12.6m, the first aqueous hydrogen peroxide solution injection point is 2m before the starting end of the last-stage superheater, the second aqueous hydrogen peroxide solution injection point is in the middle of the last-stage superheater, and the third aqueous hydrogen peroxide solution injection point is 11m after the starting end of the last-stage superheater (1 m after the tail end of the superheater).
The specific denitration process comprises the following steps:
3 x 3 2 2During ignition and low load operation of the boiler, when the temperature of flue gas at a first aqueous solution injection point 1 reaches 400 ℃, a spray gun at the first aqueous solution injection point 1 is thrown in to inject an aqueous solution of dioxygen, when the temperature of flue gas at a second aqueous solution injection point 2 reaches 400 ℃, a spray gun at the second aqueous solution injection point 2 is thrown in to inject an aqueous solution of dioxygen, if the temperature of flue gas at the first aqueous solution injection point 1 exceeds 500 ℃, the spray gun at the first aqueous solution injection point 1 is withdrawn, if the temperature of flue gas at the first aqueous solution injection point 1 does not exceed 500 ℃, the spray gun at the first aqueous solution injection point 1 is continued to inject the aqueous solution of dioxygen, when the temperature of flue gas at a third aqueous solution injection point 3 reaches 400 ℃, the spray gun at the third aqueous solution injection point 3 is thrown in to inject the aqueous solution of dioxygen, if the temperature of flue gas at the second aqueous solution injection point 2 exceeds 500 ℃, the spray gun at the second aqueous solution injection point 2 injects the aqueous solution injection point 2, if the temperature of flue gas at the second aqueous solution injection point 2 exceeds 500 ℃, the spray gun injection point 2 is not, the spray gun is continued to inject the aqueous solution injection point injection of the NOx injection system, if the flue gas injection temperature of the NOx injection point 2 exceeds 367/19% NOx injection point, the flue gas injection of the NOx injection point, the NOx injection point injection of the NOx injection point, the NOx injection system is not injected by the NOx injection point 2, the NOx injection point, the NOx injection system is not injected at 367/19% NOx injection point, the NOx injection point is not injected by the NOx injection point, the NOx injection.
The flue gas is oxidized by spraying a hydrogen peroxide solution on a spraying point, and then washing liquid is washed in a countercurrent spray tower, the tower diameter of the spray tower is 8.8m, the flue gas amount is 95.7Nm 3/s, the tower temperature is 40-55 ℃, the washing liquid is calcium hydroxide slurry, the pH is controlled to be 3-6, sodium sulfite is added into the washing liquid, the addition amount is about 0.1mol/L, the residence time of the flue gas in the tower is about 5.2s, the spraying amount of the washing liquid is about 620L/s, the denitrated flue gas is obtained at a top gas outlet of the spray tower, the NO x content of the denitrated flue gas is monitored, and the result is that the NO x concentration is about 78mg/Nm 3.
example 3
With reference to the arrangement shown in fig. 1, the point of injection of the hydrogen peroxide solution is arranged, in this embodiment, with the last superheater stage 4 arranged below the boiler turn-around chamber 6. The cross section size of the superheater flue in the direction vertical to the flue gas flow is 10 multiplied by 14m, the first hydrogen peroxide solution injection point is 3.5m before the starting end of the last-stage superheater, the second hydrogen peroxide solution injection point is in the middle of the last-stage superheater, and the third hydrogen peroxide solution injection point is 12m behind the starting end of the last-stage superheater (1 m behind the tail end of the superheater).
The specific denitration process comprises the following steps:
3 x 3 2 2During ignition and low load operation of the boiler, when the temperature of flue gas at a first aqueous solution injection point 1 reaches 400 ℃, a spray gun at the first aqueous solution injection point 1 is thrown in to inject an aqueous solution of dioxygen, when the temperature of flue gas at a second aqueous solution injection point 2 reaches 400 ℃, a spray gun at the second aqueous solution injection point 2 is thrown in to inject an aqueous solution of dioxygen, if the temperature of flue gas at the first aqueous solution injection point 1 exceeds 500 ℃, the spray gun at the first aqueous solution injection point 1 is withdrawn, if the temperature of flue gas at the first aqueous solution injection point 1 does not exceed 500 ℃, the spray gun at the first aqueous solution injection point 1 is continued to inject the aqueous solution of dioxygen, when the temperature of flue gas at a third aqueous solution injection point 3 reaches 400 ℃, a spray gun at a third aqueous solution injection point 3 is thrown in to inject the aqueous solution of dioxygen, if the temperature of flue gas at the second aqueous solution injection point 2 exceeds 500 ℃, the spray gun at the second aqueous solution injection point 2 injects the aqueous solution, if the temperature of flue gas at the second aqueous solution injection point 2 exceeds 500 ℃ and the spray gun at the second aqueous solution injection point 2, the spray gun injection point 2 is not injected, the flue gas injection point 2, the injection point 2 is not injected with a denitration system injection temperature of NOx injection point 3632, if the flue gas injection temperature of the NOx injection point 2 is not higher than the NOx injection point 2, the NOx injection temperature of the NOx injection point 2 injection point is not injected, the NOx injection point injection temperature of the NOx injection point 2, the NOx injection point is not injected, the NOx injection temperature of the NOx injection point is not higher than the NOx injection point 3632-NOx injection point.
Spraying hydrogen peroxide solution on a spraying point to oxidize the flue gas, and then washing with washing liquid in a counter-current spray tower, wherein the diameter of the spray tower is 13m, the flue gas amount is 202.3Nm 3/s, the tower temperature is 40-55 ℃, the washing liquid is calcium hydroxide slurry, the pH is controlled to be 3-6, sodium sulfite is added into the washing liquid, the addition amount is about 0.1mol/L, the residence time of the flue gas in the tower is about 5.5s, the spraying amount of the washing liquid is about 1012L/s, the denitrated flue gas is obtained at an air outlet of the spray tower, and the NO x content of the denitrated flue gas is monitored, so that the NO x concentration is about 88mg/Nm 3.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (8)
1. An SCR denitration method comprises the following steps:
a) the flue gas flows through the boiler flue; the section of the flue between the final superheater and the upper superheater is internally provided with a first hydrogen peroxide solution injection point, the section of the flue corresponding to the final superheater is internally provided with a second hydrogen peroxide solution injection point, and the section of the flue between the final superheater and the economizer is provided with a third hydrogen peroxide solution injection point;
when the temperature of the flue gas at the first hydrogen peroxide solution injection point is within a preset temperature range, spraying hydrogen peroxide solution to the flue gas at the first hydrogen peroxide solution injection point; when the flue gas temperature of the first hydrogen peroxide solution injection point is out of the preset temperature range, stopping injecting the hydrogen peroxide solution at the first hydrogen peroxide solution injection point;
When the temperature of the flue gas at the second aqueous solution injection point is within a preset temperature range, spraying an aqueous solution of hydrogen peroxide to the flue gas at the second aqueous solution injection point; when the temperature of the flue gas at the second hydrogen peroxide solution injection point is out of the preset temperature range, stopping injecting the hydrogen peroxide solution at the second hydrogen peroxide solution injection point;
when the temperature of the flue gas at the third hydrogen peroxide solution injection point is within the preset temperature range, spraying the hydrogen peroxide solution to the flue gas at the third hydrogen peroxide solution injection point; when the flue gas temperature of the third hydrogen peroxide solution injection point is lower than the preset temperature range, the third hydrogen peroxide solution injection point stops injecting the hydrogen peroxide solution; when the flue gas temperature of the third hydrogen peroxide solution injection point is higher than the preset temperature range, stopping injecting the hydrogen peroxide solution at all hydrogen peroxide solution injection points;
spraying hydrogen peroxide solution on the flue gas to obtain oxidized flue gas;
b) Washing the oxidized flue gas by using a washing solution to obtain denitrated flue gas, wherein H 2 O 2, organic sulfoxide or sulfite are added into the washing solution;
In the step a), the preset temperature ranges of the first hydrogen peroxide solution injection point, the second hydrogen peroxide solution injection point and the third hydrogen peroxide solution injection point are all 400-500 ℃;
in the step a), when the temperature of the flue gas at the injection point of the third hydrogen peroxide solution is higher than the preset temperature range, the flue gas is denitrated by using SCR.
2. The method of claim 1, wherein the second aqueous hydrogen peroxide solution injection point is located in the middle of the section of the flue corresponding to the last stage superheater.
3. The method according to claim 1, wherein the distance between the first aqueous hydrogen peroxide solution injection point and the beginning end of the final-stage superheater is 2-5 m, and the distance between the third aqueous hydrogen peroxide solution injection point and the end of the final-stage superheater is 1-12 m along the flow direction of flue gas.
4. The method of claim 1, wherein the last stage superheater is located below a turn-around chamber of the flue.
5. The method according to claim 1, wherein the concentration of H 2 O 2 in the hydrogen peroxide solution is 20-30 wt%, and the molar ratio of the H 2 O 2 injection amount of each hydrogen peroxide solution injection point to the NO x content in the flue gas when the flue gas flows through the injection point is 2-3.
6. the method according to claim 1, wherein the H 2 O 2, the organic sulfoxide or sulfite is added in an amount of 0.06mol/L or more in the washing solution.
7. The method according to claim 1, wherein the pH of the washing solution is 3 to 6.
8. The method according to claim 1, wherein the washing mode is spraying, and the liquid-gas ratio of the washing liquid to the oxidation flue gas in the washing process is 3-8L/m 3.
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