CN110624411A - SCR denitration system - Google Patents

SCR denitration system Download PDF

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Publication number
CN110624411A
CN110624411A CN201910842320.4A CN201910842320A CN110624411A CN 110624411 A CN110624411 A CN 110624411A CN 201910842320 A CN201910842320 A CN 201910842320A CN 110624411 A CN110624411 A CN 110624411A
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China
Prior art keywords
ammonia
unit
catalyst layer
nozzle
spraying
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CN201910842320.4A
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Chinese (zh)
Inventor
王云
胡小夫
耿宣
汪洋
高春昱
孙静楠
郝正
王永林
沈宪明
沈建永
王桦
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China Huadian Engineering Group Co Ltd
Huadian Environmental Protection Engineering and Technology Co Ltd
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China Huadian Engineering Group Co Ltd
Huadian Environmental Protection Engineering and Technology Co Ltd
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Priority to CN201910842320.4A priority Critical patent/CN110624411A/en
Publication of CN110624411A publication Critical patent/CN110624411A/en
Pending legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/54—Nitrogen compounds
    • B01D53/56—Nitrogen oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/88—Handling or mounting catalysts
    • B01D53/885—Devices in general for catalytic purification of waste gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/90—Injecting reactants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2062—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0283—Flue gases
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

The invention provides an SCR denitration system. In the SCR denitration system, after flue gas and ammonia sprayed by the first ammonia spraying unit are mixed and flow through the first catalyst layer, unreacted NO still remains in the flue gasxAnd a small amount of NH3At the moment, the second ammonia spraying unit sprays ammonia towards the flue gas, furthermore, the nozzle adopts a plurality of auxiliary nozzles which are arranged around the first nozzle by taking the first nozzle as the center and have included angles of 0-90 ℃ with the first nozzle, and then the distance between the second ammonia spraying unit and the second catalyst layer is ensured to be larger than the distance between the second ammonia spraying unit and the first catalyst layer, so that the unreacted NO flowing out of the first catalyst layer is enabled to flow outxAnd NH3NH injected with the second ammonia injection unit3The second ammonia spraying unit and the second catalyst layer are mixed to form a more uniform ammonia nitrogen mixture, and the mixture is reacted more fully on the second catalyst layer to avoid ammonia escape and NOxThe problem of super row and follow-up air heater jam has improved SCR deNOx systems's denitration efficiency.

Description

SCR denitration system
Technical Field
The invention relates to the field of flue gas denitration, in particular to an SCR denitration system.
Background
The nitrogen oxide can form acid rain and photochemical smog, can destroy the ozone layer and is a main pollutant of the atmosphere, so that the nitrogen oxide is fully treated, and the perfection of the denitration technology has very important significance for protecting the ecological environment. Selective Catalytic Reduction (SCR) technology is the mainstream technology for nitrogen oxide emission control of thermal power plants, and NH is injected into flue gas3The reducing agents react with NOx to form N2So as to realize the removal of nitrogen oxides. Aiming at harsh environmental protection requirements (the emission standard is reduced to 30 mg/Nm)3Or lower), the actual denitration efficiency of the SCR denitration system of some projects needs to be improved to more than 90%.
The SCR denitration system is generally characterized in that guide plates with different shapes are arranged at the horizontal connecting flue of the inlet of the reactor, and a series of rectification grids with the same height are uniformly arranged at the position of a support beam on the first layer of catalyst, so that smoke is enabled to be dischargedThe gas flows through the first layer of catalyst before the gas flows through the first layer of catalyst in order to obtain better flow field distribution. However, during actual operation, the design also does not guarantee a completely uniform velocity field and concentration field for the flue gas, so that unreacted NOx and NH remain3. At the same time, unreacted NOx and NH3The ammonia nitrogen molar ratio is more unevenly distributed when flowing along with the flue gas, so that the residual NOx and NH3Not fully reacted and finally unreacted NOx and NH3Along with the emission of flue gas, the denitration efficiency is reduced, and NO is generatedxThe phenomenon of excessive emission and ammonia escape. And the escaped ammonia can react with sulfur dioxide to generate viscous ammonium sulfate or ammonium bisulfate, so that the air preheater is contaminated, the circulation section of the air preheater is reduced, and the air preheater is blocked. The ash blockage of the air preheater not only obviously reduces the boiler efficiency, but also influences the safe and stable operation of the denitration unit.
Disclosure of Invention
Therefore, the invention aims to solve the technical problems that the actual denitration efficiency of an SCR denitration system is low and NO is not generatedxThe defects of excessive emission, high ammonia escape and blockage of a follow-up air preheater are overcome, and the SCR denitration system is provided.
The technical scheme provided by the invention is as follows:
the invention provides an SCR denitration system, which comprises a main body, wherein the main body comprises a circulation section and a reaction section which are sequentially communicated, and the SCR denitration system also comprises a denitration section,
the first ammonia injection unit is arranged in the circulation section close to the flue gas inlet of the circulation section;
the ammonia injection device comprises a first catalyst layer and a second ammonia injection unit, wherein the second ammonia injection unit is arranged in the reaction section, and the first catalyst layer is arranged between the first ammonia injection unit and the second ammonia injection unit and is positioned in the reaction section;
and the second catalyst layer is arranged in the reaction section and is far away from the first catalyst layer relative to the second ammonia spraying unit, and the distance between the second ammonia spraying unit and the second catalyst layer is larger than the distance between the second ammonia spraying unit and the first catalyst layer.
Further, the distance between the second ammonia spraying unit and the first catalyst layer is 50mm-500 mm;
the first ammonia spraying unit is provided with a first nozzle, the first ammonia spraying unit is provided with a plurality of first auxiliary nozzles which are arranged around the first nozzle by taking the first nozzle as a center, included angles between the first auxiliary nozzles and the first nozzle are 0-90 ℃, and an included angle alpha between the spraying direction of the first nozzle and the axial direction of the circulation section is 0-45 degrees;
the second ammonia spraying unit is provided with a second nozzle, the second ammonia spraying unit is provided with a plurality of first auxiliary nozzles which are arranged around the first nozzle and form included angles with the second nozzle of 0-90 ℃, and the included angle beta between the spraying direction of the second nozzle and the axial direction of the reaction section is 0-45 degrees.
That is to say, the first ammonia injection unit and the second ammonia injection unit keep the original nozzles unchanged, and 1-5 auxiliary nozzles with included angles of 0-90 ℃ are added between the original nozzles by taking the original nozzles as the center.
The reaction section is provided with a first catalyst layer and a second catalyst layer, wherein the first catalyst layer is arranged in the reaction section and is far away from the first catalyst layer relative to the second catalyst layer;
a fourth catalyst layer disposed within the reaction section and disposed distal from the second catalyst layer relative to the third catalyst layer;
further, the reaction device also comprises a third ammonia spraying unit arranged in the reaction section, and the third ammonia spraying unit is arranged between the second catalyst layer and the third catalyst layer.
Further, the distance between the third ammonia injection unit and the third catalyst layer is larger than the distance between the third ammonia injection unit and the second catalyst layer;
the third ammonia spraying unit is provided with a third nozzle, the third ammonia spraying unit is provided with a plurality of first auxiliary nozzles which are arranged around the first nozzle and form included angles of 0-90 ℃ with the third nozzle, and the included angle gamma between the spraying direction of the third nozzle and the axial direction of the reaction section is 0-45 degrees.
Further, still include the unit of mixing evenly, set up in the circulation section, the unit of mixing evenly includes the first unit of mixing evenly and the second unit of mixing evenly, first ammonia unit of spouting set up in between the first unit of mixing evenly and the second unit of mixing evenly.
Further, the distance between the first ammonia spraying unit and the first uniform mixing unit is 50-500 mm;
the distance between the first ammonia spraying unit and the second uniform mixing unit is 50-500 mm.
The ammonia injection device comprises a first ammonia injection unit, a second ammonia injection unit and a third ammonia injection unit, wherein the first ammonia injection unit, the second ammonia injection unit and the third ammonia injection unit are respectively communicated with the ammonia injection device;
and the flow regulating valves are respectively arranged on the reducing agent supply device and the first ammonia injection unit, the reducing agent supply device and the second ammonia injection unit, and the reducing agent supply device and the third ammonia injection unit.
Furthermore, the first ammonia spraying units are any one of a subarea ammonia spraying grid and a mixed ammonia spraying grid, and the number of the first ammonia spraying units is 1-3; the second ammonia spraying units are any one of a subarea ammonia spraying grid and a mixed ammonia spraying grid, and the number of the second ammonia spraying units is 1; the third ammonia spraying units are linear ammonia spraying grids, and the number of the third ammonia spraying units is 1.
The technical scheme of the invention has the following advantages:
1. the SCR denitration system provided by the invention is characterized in that a first ammonia spraying unit is arranged in the flow section, a first catalyst layer and a second catalyst layer are arranged in the reaction section, a second ammonia spraying unit is arranged between the first catalyst layer and the second catalyst layer, and after flue gas and ammonia sprayed by the first ammonia spraying unit are mixed and flow through the first catalyst layer, unreacted NO is generatedxAnd NH3The ammonia injection unit has non-uniform flow field distribution and concentration distribution, and the second ammonia injection unit injects ammonia towards the flue gas to ensure that NO in the flue gasxCan react with NH3Contact with each other, and ensure that the distance between the second ammonia spraying unit and the second catalyst layer is larger than the distance between the second ammonia spraying unit and the second catalyst layerThe distance between the first catalyst layers is such that the unreacted NO flowing out of the first catalyst layersxAnd NH3The ammonia sprayed by the second ammonia spraying unit is mixed between the second ammonia spraying unit and the second catalyst layer to form a more uniform ammonia nitrogen mixture, and the mixture reacts more fully on the second catalyst layer again to avoid ammonia escape and NOxThe problem of super row and follow-up air heater jam has improved SCR deNOx systems's denitration efficiency.
2. The first ammonia spraying unit is provided with a plurality of first auxiliary nozzles which are arranged around the first nozzle by taking the first nozzle as the center and have included angles of 0-90 ℃ with the first nozzle, and the included angle alpha between the spraying direction of the first nozzle and the axial direction of the reaction section is limited to 0-45 DEG, so that NO is favorably prevented from being generatedxAnd NH3The flue gas is uniformly mixed, so that the flue gas has a uniform concentration field, and the removal rate of NOx in the flue gas after the flue gas flows through the first layer of catalyst is improved.
3. According to the SCR denitration system provided by the invention, the second ammonia spraying unit is provided with a plurality of second auxiliary nozzles which surround the second nozzle as the center and have included angles of 0-90 ℃ with the second nozzle, and the distance between the second ammonia spraying unit and the first catalyst layer is optimized, so that the unreacted NO flowing out of the first catalyst layer is ensuredxAnd NH3The ammonia and the ammonia sprayed by the second ammonia spraying unit can be mixed as soon as possible; the mixing effect of the flue gas and the ammonia is further improved by limiting the included angle beta between the spraying direction of the second nozzle and the axial direction of the reaction section to be 0-45 degrees.
4. The SCR denitration system provided by the invention is also provided with a third catalyst layer and a fourth catalyst layer, a third ammonia spraying unit is arranged between the second catalyst layer and the third catalyst layer, and ammonia sprayed by the third ammonia spraying unit enables a nitrogen-ammonia mixture flowing through the third catalyst layer to have a uniform flow field and a uniform concentration field, so that the denitration efficiency of the third catalyst layer is improved, and the denitration efficiency of the SCR denitration system is finally improved. Furthermore, the distance between the third ammonia spraying unit and the third catalyst layer is larger than the distance between the third ammonia spraying unit and the second catalyst layer, so that the unreacted NO flowing out of the second catalyst layerxAnd NH3With tertiary ammonium spraying monomerThe ammonia sprayed by the unit is uniformly mixed between the third ammonia spraying unit and the third catalyst layer to form an ammonia nitrogen mixture, so that the ammonia nitrogen mixture has a more uniform flow field and a more uniform concentration field, and can fully react on the third catalyst layer; furthermore, the included angle gamma between the spraying direction of the second nozzle and the axial direction of the reaction section is 0-45 degrees, so that the mixing effect of the flue gas and the ammonia is further improved.
5. According to the SCR denitration system provided by the invention, the partition ammonia injection grating or the mixed ammonia injection grating is used as the first ammonia injection unit, the aperture of the nozzle is large, and the blocking probability is reduced. And meanwhile, the partition ammonia injection grating or the mixed ammonia injection grating has higher mixing efficiency, so that the denitration efficiency of ammonia-containing flue gas when passing through the first catalyst layer can be improved, the pressure of the second ammonia injection unit is further reduced, the denitration efficiency of the system is improved, the ammonia escape is reduced, and the blockage of the air preheater is avoided.
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, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic structural diagram of an SCR denitration system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the first ammonia injection grid of FIG. 1;
FIG. 3 is a schematic diagram of the second ammonia injection grid of FIG. 1;
FIG. 4 is a schematic diagram of the third ammonia injection grid of FIG. 1;
FIG. 5 is another schematic diagram of the first ammonia injection grid according to the embodiment of the present invention;
FIG. 6 is a schematic view showing another structure of the second ammonia injection grid in the embodiment of the present invention;
reference numerals:
1-a flue gas inlet; 2-a flow-through section; 3-a reaction section; 4-a homogenizing unit; 4-1-a first homogenizing unit; 4-2-a second homogenizing unit; 5-a first ammonia injection grid; 5 a-a first nozzle; 5 b-a first auxiliary nozzle; 6-a second ammonia injection grid; 6 a-a first nozzle; 6 b-a first auxiliary nozzle; 7-a third ammonia injection grid; 8-a rectifying grid; 9-a first catalyst layer; 10-a second catalyst layer; 11-a third catalyst layer; 12-flue gas outlet.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. 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.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The embodiment of the invention provides an SCR denitration system, which comprises a main body and a first ammonia injection unit, wherein the main body comprises a circulation section 2 and a reaction section 3 which are sequentially communicated, the first ammonia injection unit is a first ammonia injection grid 5, and a flue gas inlet 1 close to the circulation section 2 is arranged in the circulation section 2; the ammonia injection device comprises a first catalyst layer 9 and a second ammonia injection unit, wherein the second ammonia injection unit is a second ammonia injection grid 6, the second ammonia injection unit is arranged in the reaction section 3, and the first catalyst layer 9 is arranged between the first ammonia injection unit and the second ammonia injection unit and is positioned in the reaction section 3;
and the second catalyst layer 10 is arranged in the reaction section 3 and is far away from the first catalyst layer 9 relative to the second ammonia spraying unit, and the distance between the second ammonia spraying unit and the second catalyst layer 10 is larger than the distance between the second ammonia spraying unit and the first catalyst layer 9. In this embodiment, the catalysts in the first catalyst layer 9 and the second catalyst layer 10 are denitration catalysts, and the existing denitration catalysts may be specifically adopted, which is not described herein again.
In the SCR denitration system, the first ammonia spraying unit is arranged in the flow section 2, the first catalyst layer 9 and the second catalyst layer 10 are arranged in the reaction section 3, the second ammonia spraying unit is arranged between the first catalyst layer 9 and the second catalyst layer 10, and after flue gas is mixed with ammonia sprayed by the first ammonia spraying unit and flows through the first catalyst layer 9, unreacted NO is generatedxAnd NH3The ammonia injection unit has non-uniform flow field distribution and concentration distribution, and the second ammonia injection unit injects ammonia towards the flue gas to ensure that NO in the flue gasxCan react with NH3Contact with the catalyst layer, and ensure that the distance between the second ammonia spraying unit and the second catalyst layer 10 is larger than the distance between the second ammonia spraying unit and the first catalyst layer 9, so that the unreacted NO flowing out of the first catalyst layer 9xAnd NH3The ammonia sprayed by the second ammonia spraying unit forms a more uniform ammonia nitrogen mixture between the second ammonia spraying unit and the second catalyst layer 10, and the ammonia form a more sufficient reaction again on the second catalyst layer 10, so that ammonia escape and NO are avoidedxSuper-exhaust and subsequent air pre-exhaustThe problem of the blockage of the heat exchanger improves the denitration efficiency of the SCR denitration system. Finally, the denitrated flue gas is discharged from the flue gas outlet 12.
As an alternative embodiment, the distance between the second ammonia injection unit and the first catalyst layer 9 is 50mm-500mm, for example 50mm, which ensures that the unreacted NO flowing out of the first catalyst layerxAnd NH3The ammonia sprayed by the second ammonia spraying unit can be mixed as soon as possible, and the size of the device is reduced on the premise of disturbing the flow field of flue gas.
As shown in fig. 2, the first ammonia spraying unit is provided with a first nozzle, and the included angle alpha between the spraying direction of the first nozzle and the axial direction of the circulation section is 0-45 degrees; as shown in FIG. 3, the second ammonia spraying unit is provided with a second nozzle, and the spraying direction of the second nozzle forms an included angle beta of 0-45 degrees with the axial direction of the reaction section. The mixing effect of the flue gas and the ammonia is further improved by limiting an included angle alpha between the spraying direction of the first nozzle and the axial direction of the flow section and an included angle beta between the spraying direction of the second nozzle and the axial direction of the reaction section. The included angle alpha between the spraying direction of the first nozzle and the axial direction of the reaction section is limited to be 0-45 degrees, so that the uniform mixing of NOx and NH3 is facilitated, the flue gas has a uniform concentration field, and the removal rate of NOx in the flue gas after the flue gas flows through the first layer of catalyst is improved.
On the basis of the above technical solution, the reactor further comprises a third catalyst layer 11, which is arranged in the reaction section 3 and is far away from the first catalyst layer 9 relative to the second catalyst layer 10;
a fourth catalyst layer (not shown) disposed in the reaction section 3 and away from the second catalyst layer 10 relative to the third catalyst layer 11;
as an optional embodiment, the reactor further comprises a third ammonia injection unit disposed in the reaction section 3, and the third ammonia injection unit is disposed between the second catalyst layer 10 and the third catalyst layer 11. The ammonia sprayed by the third ammonia spraying unit enables the nitrogen-ammonia mixture flowing through the third catalyst layer to have uniform flow field and concentration field, so that the denitration efficiency of the third catalyst layer is improved, and the denitration efficiency of the SCR denitration system is finally improved.
In aIn the embodiment, the distance between the third ammonia injection unit and the third catalyst layer 11 is larger than the distance between the third ammonia injection unit and the second catalyst layer 10, so that the unreacted NO flowing out from the second catalyst layer 10xAnd NH3The ammonia injected by the third ammonia injection unit is mixed in a longer area between the third ammonia injection unit and the third catalyst layer 11 to form an ammonia nitrogen mixture, so that the ammonia nitrogen mixture has a more uniform flow field and a more uniform concentration field, and can fully react in the third catalyst layer 11;
as shown in FIG. 4, the included angle gamma between the spraying direction of the second nozzle and the axial direction of the reaction section is 0-45 degrees, and the mixing effect of the flue gas and the ammonia is further improved.
As shown in fig. 1, the ammonia injection device further comprises a mixing unit 4 disposed in the circulation section 2, wherein the mixing unit 4 comprises a first mixing unit 4-1 and a second mixing unit 4-2, and the first ammonia injection unit is disposed between the first mixing unit 4-1 and the second mixing unit 4-2. Preferably, the distance between the first ammonia spraying unit and the first uniform mixing unit 4-1 is 50mm-500 mm; the distance between the first ammonia spraying unit and the second uniform mixing unit 4-2 is 50mm-500 mm. In this embodiment, both the first and second homogenizing units 4-1 and 4-2 can be static mixers.
The ammonia injection device comprises a first ammonia injection unit, a second ammonia injection unit and a third ammonia injection unit, wherein the first ammonia injection unit, the second ammonia injection unit and the third ammonia injection unit are respectively communicated with the ammonia injection device; and the flow regulating valves are respectively arranged on the reducing agent supply device and the first ammonia injection unit, the reducing agent supply device and the second ammonia injection unit, and the reducing agent supply device and the third ammonia injection unit.
Further, the first ammonia spraying unit is any one of a subarea ammonia spraying grid and a mixed ammonia spraying grid, and the number of the linear ammonia spraying grids is 1-3; the second ammonia spraying units are any one of a subarea ammonia spraying grid and a mixed ammonia spraying grid, and the number of the second ammonia spraying units is 1; the third ammonia spraying units are linear ammonia spraying grids, and the number of the third ammonia spraying units is 1.
Furthermore, the first nozzle, the second nozzle and the third nozzle are all rotary atomizing nozzles, the ammonia particles sprayed by the rotary atomizing nozzles are very fine and uniform, and meanwhile, the atomizing range of the atomized ammonia particles is large, so that the rotary atomizing nozzles can be effectively mixed with flue gas, and the nitrogen-ammonia mixture of the corresponding catalyst layer has a uniform flow field and a uniform concentration field.
In one embodiment, the first ammonia injection unit is a partition ammonia injection grid, and the number of the first ammonia injection units is 1; the second ammonia spraying units are partitioned ammonia spraying grids, and the number of the second ammonia spraying units is 1; the third ammonia spraying unit is a linear ammonia spraying grid, and the number of the third ammonia spraying units is 1; in another embodiment, the first ammonia injection unit is a mixed ammonia injection grid, and the number of the first ammonia injection units is 3; the second ammonia spraying units are partitioned ammonia spraying grids, and the number of the second ammonia spraying units is 1; the third ammonia spraying unit is a linear ammonia spraying grid, and the number of the third ammonia spraying units is 1; therefore, the partition ammonia injection grid or the mixed ammonia injection grid is used as the first ammonia injection unit, the aperture of the nozzle is large, and the blocking probability is reduced. And meanwhile, the partition ammonia injection grating or the mixed ammonia injection grating has higher mixing efficiency, so that the denitration efficiency of ammonia-containing flue gas when passing through the first catalyst layer can be improved, the pressure of the second ammonia injection unit is further reduced, the denitration efficiency of the system is improved, the ammonia escape is reduced, and the blockage of the air preheater is avoided.
As shown in fig. 1, the reactor further comprises a rectifying grating 8 disposed between the second uniform mixing unit 4-2 and the first catalyst layer 9 and located in the reaction section 3. The ammonia nitrogen mixture is rectified again by arranging a rectifying grating 8.
As shown in fig. 5, the first ammonia injection unit has a plurality of first auxiliary nozzles 5b arranged around a first nozzle 5a as a center, and the included angles between the first auxiliary nozzles and the first nozzle 5a are 0-90 ℃;
as shown in fig. 6, the second ammonia injection unit has a plurality of second auxiliary nozzles 6b arranged around the second nozzle 6a at an included angle of 0 to 90 degrees with the second nozzle 6 a. That is to say, the first ammonia injection unit and the second ammonia injection unit keep the original nozzles unchanged, and 1-5 auxiliary nozzles with included angles of 0-90 ℃ are added between the original nozzles by taking the original nozzles as the center. This improves the ammonia injection effect.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (9)

1. An SCR denitration system comprises a main body, the main body comprises a circulation section and a reaction section which are sequentially communicated, and the SCR denitration system is characterized by also comprising,
the first ammonia injection unit is arranged in the circulation section close to the flue gas inlet of the circulation section;
the ammonia injection device comprises a first catalyst layer and a second ammonia injection unit, wherein the second ammonia injection unit is arranged in the reaction section, and the first catalyst layer is arranged between the first ammonia injection unit and the second ammonia injection unit and is positioned in the reaction section;
and the second catalyst layer is arranged in the reaction section and is far away from the first catalyst layer relative to the second ammonia spraying unit, and the distance between the second ammonia spraying unit and the second catalyst layer is larger than the distance between the second ammonia spraying unit and the first catalyst layer.
2. The SCR denitration system of claim 1, wherein a distance between the second ammonia injection unit and the first catalyst layer is 50mm-500 mm;
the first ammonia spraying unit is provided with a first nozzle, the first ammonia spraying unit is provided with a plurality of first auxiliary nozzles which are arranged around the first nozzle by taking the first nozzle as a center, included angles between the first auxiliary nozzles and the first nozzle are 0-90 ℃, and an included angle alpha between the spraying direction of the first nozzle and the axial direction of the circulation section is 0-45 degrees;
the second ammonia spraying unit is provided with a second nozzle, the second ammonia spraying unit is provided with a plurality of first auxiliary nozzles which are arranged around the first nozzle and form included angles with the second nozzle of 0-90 ℃, and the included angle beta between the spraying direction of the second nozzle and the axial direction of the reaction section is 0-45 degrees.
3. The SCR denitration system of claim 1 or 2, further comprising,
a third catalyst layer disposed within the reaction section and disposed distal to the first catalyst layer relative to the second catalyst layer;
and the fourth catalyst layer is arranged in the reaction section and is far away from the second catalyst layer relative to the third catalyst layer.
4. The SCR denitration system of claim 3, further comprising a third ammonia injection unit disposed in the reaction section, wherein the third ammonia injection unit is disposed between the second catalyst layer and a third catalyst layer.
5. The SCR denitration system of claim 4, wherein a distance between the third ammonia injection unit and the third catalyst layer is larger than a distance between the third ammonia injection unit and the second catalyst layer;
the third ammonia spraying unit is provided with a third nozzle, the third ammonia spraying unit is provided with a plurality of first auxiliary nozzles which are arranged around the first nozzle and form included angles of 0-90 ℃ with the third nozzle, and the included angle gamma between the spraying direction of the third nozzle and the axial direction of the reaction section is 0-45 degrees.
6. The SCR denitration system of claim 1 or 2, further comprising,
the unit that mixes all, set up in the circulation section, the unit that mixes all includes that first unit and the second unit that mixes all is mixed all, first ammonia unit that spouts set up in first unit and the second unit that mixes all is mixed between the unit.
7. The SCR denitration system of claim 6, wherein the distance between the first ammonia injection unit and the first uniform mixing unit is 50mm-500 mm;
the distance between the first ammonia spraying unit and the second uniform mixing unit is 50-500 mm.
8. The SCR denitration system of claim 4, further comprising,
the reducing agent supply device is respectively communicated with the first ammonia spraying unit, the second ammonia spraying unit and the third ammonia spraying unit so as to provide reducing agents for the first ammonia spraying unit, the second ammonia spraying unit and the third ammonia spraying unit;
and the flow regulating valves are respectively arranged on the reducing agent supply device and the first ammonia injection unit, the reducing agent supply device and the second ammonia injection unit, and the reducing agent supply device and the third ammonia injection unit.
9. The SCR denitration system of claim 8, wherein the first ammonia injection unit is any one of a zoned ammonia injection grid and a mixed ammonia injection grid; the second ammonia spraying unit is any one of a subarea ammonia spraying grid and a mixed ammonia spraying grid; the third ammonia spraying unit is a linear ammonia spraying grid.
CN201910842320.4A 2019-09-06 2019-09-06 SCR denitration system Pending CN110624411A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114570195A (en) * 2022-03-14 2022-06-03 大唐环境产业集团股份有限公司 SCR reactor, catalyst and preparation method thereof
WO2023015889A1 (en) * 2021-08-13 2023-02-16 交通运输部天津水运工程科学研究所 Reductant multi-position layered injection structure for ship denitration

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023015889A1 (en) * 2021-08-13 2023-02-16 交通运输部天津水运工程科学研究所 Reductant multi-position layered injection structure for ship denitration
CN114570195A (en) * 2022-03-14 2022-06-03 大唐环境产业集团股份有限公司 SCR reactor, catalyst and preparation method thereof

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