CN114733331A - Coal-fired flue gas dechlorination system and method - Google Patents
Coal-fired flue gas dechlorination system and method Download PDFInfo
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- CN114733331A CN114733331A CN202210347465.9A CN202210347465A CN114733331A CN 114733331 A CN114733331 A CN 114733331A CN 202210347465 A CN202210347465 A CN 202210347465A CN 114733331 A CN114733331 A CN 114733331A
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- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 88
- 239000003546 flue gas Substances 0.000 title claims abstract description 88
- 238000006298 dechlorination reaction Methods 0.000 title claims abstract description 39
- 238000000034 method Methods 0.000 title claims abstract description 22
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims abstract description 47
- 239000000920 calcium hydroxide Substances 0.000 claims abstract description 47
- 235000011116 calcium hydroxide Nutrition 0.000 claims abstract description 47
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims abstract description 47
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 40
- 230000023556 desulfurization Effects 0.000 claims abstract description 40
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000000428 dust Substances 0.000 claims abstract description 21
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims abstract description 16
- 238000005507 spraying Methods 0.000 claims abstract description 14
- 239000003245 coal Substances 0.000 claims abstract description 7
- 150000003841 chloride salts Chemical class 0.000 claims abstract description 6
- 239000000843 powder Substances 0.000 claims description 39
- 230000007246 mechanism Effects 0.000 claims description 28
- 235000019738 Limestone Nutrition 0.000 claims description 15
- 239000006028 limestone Substances 0.000 claims description 15
- 239000002245 particle Substances 0.000 claims description 13
- 239000007921 spray Substances 0.000 claims description 13
- 230000000382 dechlorinating effect Effects 0.000 claims description 9
- 238000002347 injection Methods 0.000 claims description 7
- 239000007924 injection Substances 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 238000004537 pulping Methods 0.000 claims description 4
- 230000003009 desulfurizing effect Effects 0.000 abstract description 20
- 239000007789 gas Substances 0.000 abstract description 18
- 239000010440 gypsum Substances 0.000 abstract description 9
- 229910052602 gypsum Inorganic materials 0.000 abstract description 9
- 239000002351 wastewater Substances 0.000 abstract description 7
- 238000006243 chemical reaction Methods 0.000 abstract description 6
- 238000005260 corrosion Methods 0.000 abstract description 6
- 230000007797 corrosion Effects 0.000 abstract description 6
- 230000002378 acidificating effect Effects 0.000 abstract description 5
- 238000004065 wastewater treatment Methods 0.000 abstract description 5
- 230000009467 reduction Effects 0.000 abstract description 4
- 230000008569 process Effects 0.000 abstract description 3
- 230000002195 synergetic effect Effects 0.000 abstract description 3
- 238000005070 sampling Methods 0.000 description 9
- 239000003795 chemical substances by application Substances 0.000 description 7
- 239000002002 slurry Substances 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 6
- 229910052801 chlorine Inorganic materials 0.000 description 6
- 239000000460 chlorine Substances 0.000 description 6
- 208000028659 discharge Diseases 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 4
- 239000002253 acid Substances 0.000 description 3
- 150000001804 chlorine Chemical class 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- 239000003463 adsorbent Substances 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000000292 calcium oxide Substances 0.000 description 2
- 235000012255 calcium oxide Nutrition 0.000 description 2
- 239000012159 carrier gas Substances 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 239000002594 sorbent Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- UCUJUFDOQOJLBE-UHFFFAOYSA-N [Cl].[Ca] Chemical compound [Cl].[Ca] UCUJUFDOQOJLBE-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 238000011020 pilot scale process Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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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
- B01D53/68—Halogens or halogen compounds
-
- 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
- B01D53/68—Halogens or halogen compounds
- B01D53/685—Halogens or halogen compounds by treating the gases with solids
-
- 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
- B01D53/80—Semi-solid phase processes, i.e. by using slurries
-
- 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
- B01D53/81—Solid phase processes
- B01D53/83—Solid phase processes with moving reactants
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/003—Arrangements of devices for treating smoke or fumes for supplying chemicals to fumes, e.g. using injection devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/02—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material
- F23J15/022—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material for removing solid particulate material from the gasflow
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/06—Arrangements of devices for treating smoke or fumes of coolers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2251/00—Reactants
- B01D2251/40—Alkaline earth metal or magnesium compounds
- B01D2251/404—Alkaline earth metal or magnesium compounds of calcium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2251/00—Reactants
- B01D2251/60—Inorganic bases or salts
- B01D2251/604—Hydroxides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/20—Halogens or halogen compounds
- B01D2257/204—Inorganic halogen compounds
- B01D2257/2045—Hydrochloric acid
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- 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
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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
- Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
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Abstract
The invention relates to the technical field of dechlorination systems, in particular to a coal-fired flue gas dechlorination system and a method, which comprise the following steps: after the coal-fired flue gas passes through the air preheater and before entering a desulfurization system, spraying slaked lime into the coal-fired flue gas to convert HCl in the flue gas into chloride; preferably, the chloride salts are removed by a dust separator before the flue gas enters the desulfurization system. The invention relates to a coal-fired flue gas dechlorination process using slaked lime as a desulfurizer, wherein coal is sprayed into an air preheater and then into a dedusterIn the flue gas, HCl gas in the flue gas can be removed before entering a desulfurization system. Compared with the existing mode of removing HCl gas through a desulfurizing tower, the method has the advantages that the corrosion of acidic gas to a tail flue and a desulfurizing facility is obviously reduced, the desulfurizing reaction environment is optimized, and the desulfurizing efficiency and the gypsum quality are improved; simultaneously, the synergistic emission reduction of SO is realized2And other acidic gases, and the wastewater treatment capacity is reduced, so that the cost is reduced for the subsequent treatment of the desulfurization wastewater.
Description
Technical Field
The invention relates to the technical field of dechlorination systems, in particular to a coal-fired flue gas dechlorination system and a method.
Background
Fossil fuels such as a large amount of coal and the like are combusted in a thermal power plant, chlorine-containing substances in coal powder exist in flue gas in the form of HCl after being combusted, and the HCl has strong corrosivity and can cause serious influence on the environment and human health when being discharged into the atmosphere.
However, because the content of HCl in the coal-fired flue gas is relatively low, the flue gas treatment of the thermal power plant does not adopt a single dechlorination measure at present, but a wet desulphurization system is used for enriching most of chloride ions in the flue gas in a desulphurization tower. The wet desulphurization mainly takes a limestone-gypsum method as a main raw material, limestone slurry is used as a desulfurizer, the desulphurization efficiency is 90-95 percent, the highest desulphurization efficiency can reach 99 percent, the desulphurization efficiency is stable, the technology is mature and reliable, and the byproduct desulphurization gypsum can be reused, so that the method is a mainstream technical route for flue gas desulphurization of the existing coal-fired power plants.
When the chlorine-containing gas is synergistically removed in the desulfurization process, HCl is dissolved in the desulfurization slurry, so that chloride ions are continuously enriched in the desulfurization slurry after the wet desulfurization facility operates for a period of time, and the chloride ions are mainly CaCl in the desulfurization slurry2When chloride ions in the desulfurization slurry rise, Ca is caused2+The concentration rises. CaCO as desulfurizing agent in this case3The dissolution reaction of (A) is effected, CaCO3(s)+H+Ca2++HCO3-Chemical equilibrium shifts to the left, resulting in a drop in pH, stonesUnreacted CaCO in paste3The content is increased, and the desulfurization efficiency is reduced; meanwhile, the chloride ions influence the normal crystallization and dehydration of the gypsum, so that the quality of the gypsum is reduced. Therefore, normally, the operator will control the concentration of chloride ion in the desulfurization tower to be below 20000ppm, and if the limit is exceeded, the concentration of chloride ion in the desulfurization tower will be reduced by discharging wastewater, replacing fresh slurry, etc., i.e. the total amount of chloride ion entering the desulfurization system through flue gas has a significant positive correlation with the discharge amount of wastewater.
However, the conventional wastewater treatment cost is high, and particularly in a power plant for carrying out wastewater zero-discharge treatment, the treatment process is complex, the cost is high, the treatment cost is 80-200 yuan/t, and great operation pressure is brought to the power plant. The concentration of chloride ions causes the pH value to be reduced, the acidity of the gypsum solution is enhanced, and because metal components or pipelines in the desulfurization system, which are contacted with the slurry, are mostly made of stainless steel, under the condition of low pH, the stainless steel is used for treating Cl-The desulfurization system is more sensitive, equipment corrosion is more easily caused, key equipment such as pipelines, pump bodies and blades are damaged, and the safety of the desulfurization system is seriously influenced.
Therefore, in view of the above problems, it is a technical problem to be solved by those skilled in the art to develop a novel system and method for dechlorinating coal-fired flue gas.
Disclosure of Invention
The first purpose of the invention is to provide a coal-fired flue gas dechlorination method, which can remove most of the chlorine-containing substances in the flue gas before the flue gas enters a desulfurizing tower;
the second purpose of the invention is to provide a coal-fired flue gas dechlorination system, which realizes the high-efficiency removal of chlorine-containing gas in flue gas.
The invention provides a coal-fired flue gas dechlorination method, which comprises the following steps:
after the coal-fired flue gas passes through the air preheater and before entering a desulfurization system, spraying slaked lime into the coal-fired flue gas to convert HCl in the flue gas into chloride; preferably, the chloride salt is removed by a dust remover before the flue gas enters the desulfurization system; preferably, the slaked lime is in a dry powder form.
In order to prevent the semi-dry or liquid dechlorinating agent from being bonded after being sprayed into the flue, the dry slaked lime is preferably selected in the invention.
Preferably, the particle size of the slaked lime is larger than 425 μm.
The particle size of the slaked lime is selected to be larger than 425 micrometers (40 meshes), so that the problem of low dechlorination efficiency caused by agglomeration of the small particle size serving as the dechlorinating agent can be effectively prevented.
Preferably, the temperature of the coal-fired flue gas after the air preheater is 130-150 ℃.
In order to facilitate the chlorine salt to be adsorbed by the dust remover after the reaction, the chlorine salt is in a crystallized granular shape, which is beneficial to the adsorption and discharge of the dust remover, therefore, the tail flue after the air preheater is selected to be sprayed with the dechlorinating agent, and the temperature of the flue gas after passing through the air preheater is controlled to be 130-150 ℃.
The invention also provides a coal-fired flue gas dechlorination system used by the coal-fired flue gas dechlorination method, which comprises a slaked lime supply mechanism, an air preheater, a spraying mechanism and a dust remover, wherein the air preheater and the dust remover are sequentially arranged on a flue along the flowing direction of flue gas; the spraying mechanism is arranged on a tail flue behind the air preheater and is communicated with the slaked lime supply mechanism.
Preferably, in the technical scheme, the slaked lime supply mechanism comprises a limestone slaker, a cyclone separator, a storage bin and a powder feeding fan which are sequentially communicated end to end, wherein a feed port is formed in the side surface of the cyclone separator and is communicated with the limestone slaker; a fine powder outlet and a coarse powder outlet are respectively formed in the top end and the bottom end of the cyclone separator, the fine powder outlet is communicated with an inlet of the limestone digester, the coarse powder outlet is communicated with a storage bin, and the powder feeding fan is communicated with the injection mechanism; preferably, the fine powder outlet is communicated with a desulfurization pulping system.
Preferably, in the technical scheme, the spraying mechanism comprises a plurality of spray guns uniformly distributed on the flue, each spray gun is fixedly arranged in the flue and extends into the flue, and all the spray guns are communicated with the discharge end of the powder feeding fan.
Preferably, the spray gun is provided with one or more nozzles.
Compared with the prior art, the coal-fired flue gas dechlorination method has the following technical effects:
the coal-fired flue gas dechlorination method uses the powdery slaked lime as a desulfurizer, and sprays the slaked lime into the coal-fired flue gas after the air preheater and before the dust remover, so that HCl gas in the flue gas can be removed before entering the desulfurization system. Compared with the existing mode of removing HCl gas through a desulfurizing tower, the method has the advantages that the corrosion of acidic gas to a tail flue and a desulfurizing facility is obviously reduced, the desulfurizing reaction environment is optimized, and the desulfurizing efficiency and the gypsum quality are improved; simultaneously, the synergistic emission reduction of SO is realized2And other acidic gases, and the wastewater treatment capacity is reduced, so that the cost is reduced for the subsequent treatment of the desulfurization wastewater.
Compared with the prior art, the coal-fired flue gas dechlorination system has the following technical effects:
the coal-fired flue gas dechlorination system comprises a slaked lime supply mechanism, an air preheater, a spraying mechanism and a dust remover, wherein slaked lime in the slaked lime supply mechanism reacts with HCl gas in flue gas through the spraying mechanism, and generated chloride salt particles are adsorbed by the dust remover and discharged. The spraying mechanism is arranged on a tail flue behind the air preheater, and chlorine salt which is reacted and fixed by slaked lime and HCl gas can be crystallized into particles at the flue gas temperature, and the chloride salt particles can be further adsorbed and discharged by the dust remover and further used for other purposes. Therefore, the system can remove most of the chlorine-containing substances before entering the desulfurizing tower, and the corrosion of the acid gas to the tail flue and the desulfurizing facility is obviously reduced.
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 view of a coal-fired flue gas dechlorination system of the present invention;
FIG. 2 is a graph illustrating the dechlorination efficiency of slaked lime of different particle sizes according to the present invention;
FIG. 3 is a system diagram of a 6kW CFB coal-fired flue gas injection dechlorination test device of the present invention.
Reference numerals:
1: a dust remover; 2: a limestone digester; 3: a storage bin; 4: a powder feeding fan; 5: a cyclone separator; 6: a coal bunker; 7: a screw feeder; 8: a fluidized bed combustion chamber; 9: a separator; 10: a material returning device; 11: a heat exchanger; 12: a micro screw feeder; 13: an adsorbent bin; 14: an adsorbent carrier gas; 15: a zigzag flue; 16: a first sampling point; 17: a second sampling point; 18: a third sampling point; 19: a fourth sampling point; 20: a fifth sampling point; 21: and a sixth sampling point.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular forms also include the plural forms unless the context clearly dictates otherwise, and further, it is understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the stated features, steps, operations, devices, components, and/or combinations thereof.
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
As shown in figure 1, the invention provides a coal-fired flue gas dechlorination system, which comprises a slaked lime supply mechanism, an air preheater, a spraying mechanism and a dust remover 1, wherein the air preheater and the dust remover 1 are sequentially arranged on a flue along the flowing direction of flue gas; the injection mechanism is arranged on a tail flue behind the air preheater and is communicated with the slaked lime supply mechanism.
The invention provides a coal-fired flue gas desulfurization system, aiming at the problems of worsening of desulfurization environment, reduction of desulfurization efficiency, poor quality of byproduct gypsum, increase of wastewater treatment cost and the like caused by HCl enriched in flue gas of a wet desulfurization facility of a coal-fired power plant at present. Therefore, the system can remove most of the chlorine-containing substances before entering the desulfurizing tower, obviously reduces the corrosion of the acid gas to the tail flue and the desulfurizing facility, obviously improves the desulfurizing environment and correspondingly obviously reduces the amount of the desulfurizing waste water.
On the basis of the technical scheme, the slaked lime supply mechanism further comprises a limestone slaker 2, a storage bin 3 and a powder feeding fan 4 which are sequentially communicated end to end, and the powder feeding fan 4 is communicated with the injection mechanism.
Specifically, the cheap quicklime small blocks are placed in a limestone slaker 2 for slaking to obtain dry slaked lime, the slaked lime is further stored in a storage bin 3 for standby, when the flue gas needs to be dechlorinated, slaked lime powder is conveyed to a spraying mechanism arranged in a rear tail flue of an air preheater by using a powder conveying fan 4, and at the moment, the slaked lime is mixed with the flue gas and is subjected to neutralization reaction with HCl.
The limestone digester 2 is a three-stage limestone digester, is internally provided with slaking water and a stirring device, and can completely digest quicklime after 10-30min to prepare dry slaked lime with the water content of less than 5 percent, wherein the dry slaked lime has different grain sizes and is most widely distributed with the grain size of more than 75 micrometers (200 meshes).
The research shows that: the direct use of the dry slaked lime can not obtain good dechlorination efficiency; therefore, the cyclone separator 5 is specially arranged, the particle size of the slaked lime is controlled to be more than 425 μm (40 meshes), preferably 425-850 μm (20-40 meshes), and at the moment, under the condition of single HCl and equilibrium gas in a laboratory, the dechlorination efficiency can reach 96 percent; when the particle size becomes smaller than 250 μm (60 mesh), the dechlorination efficiency is remarkably reduced to 78%, since fine particles are liable to undergo an agglomeration effect, reducing the utilization rate thereof. Therefore, a cyclone 5 is further provided in the slaked lime feeding mechanism of the present invention, and a feed port is provided at a side of the cyclone 5, the feed port being communicated with the limestone slaker 2; the top end and the bottom end of the cyclone separator 5 are respectively provided with a fine powder outlet and a coarse powder outlet, and the fine powder outlet and the coarse powder outlet can be divided into fine powder and coarse powder by reasonably designing a separation critical value, wherein the fine powder outlet is reversely communicated with the limestone digester 2, and slaked lime Ca (OH) with the particle size of less than 425 mu m (40 meshes)2Re-enter the limestone digester 2 for re-dissolution and drying, and the coarse powder outlet is communicated with the storage bin 3 to be used as a dechlorinating agent for standby so as to ensure higher removal efficiency.
In addition, the fine powder outlet is communicated with a desulfurization pulping system, and slaked lime Ca (OH) with the particle size of less than 425 mu m (40 meshes)2Can also enter a desulfurization pulping system to be used as a desulfurizer.
On the basis of the technical proposal, in order to further improve the slaked lime Ca (OH)2And the spraying mechanism comprises a plurality of spray guns which are uniformly distributed on the flue, each spray gun is fixedly arranged in the flue and extends to the inside of the flue, and all the spray guns are communicated with the discharge end of the powder feeding fan 4. Also, a particular lance may be provided with one or more nozzles. Therefore, under the action of the plurality of spray guns, the slaked lime can form a gridded spray area, and the sufficient mixing with the flue gas is ensured.
The flue gas after the desulfurization reaction enters the dust remover 1 and is then discharged from an ash bucket below the dust remover 1.
A flue gas dechlorination test is carried out on a 6kW circulating fluidized bed coal-fired flue gas jet dechlorination pilot plant by simulating the most preferable coal-fired flue gas desulfurization system, and a system diagram is shown in figure 2. Arranging flue gas sampling points at different positions, and detecting HCl in the flue gas.
In the simulated system, a coal bunker 6, a screw feeder 7, a fluidized bed combustion chamber 8, a separator 9 and a return feeder 10 jointly form a system for supplying flue gas, a heat exchanger 11 is equivalent to an air preheater, a micro screw feeder 12, a sorbent bin 13 and sorbent carrier gas 14 jointly form a slaked lime supply mechanism, and a return flue 15 is opposite to a tail flue behind the air preheater. In the system, 6 sampling points are respectively arranged, and the acquisition value at the sixth sampling point is used for calculating dechlorination efficiency.
Example 1
The temperature of the coal-fired flue gas is adjusted to 150 ℃ by using a heat exchanger 11, slaked lime with the water content of 5 percent and the grain diameter of more than 250 mu m (specifically less than 60 meshes) is sprayed into the coal-fired flue gas before the coal-fired flue gas enters a desulfurization system, HCl in the flue gas is converted into chloride, and the chloride is removed by a dust remover 1 before the flue gas enters the desulfurization system.
Example 2
The temperature of the coal-fired flue gas is adjusted to 130 ℃ by using a heat exchanger 11, slaked lime (dry powder Ca (OH)) with the water content of 5 percent and the grain diameter of more than 425 mu m (specifically 20-40 meshes) is sprayed into the coal-fired flue gas before entering a desulfurization system2Powder) to convert the HCl in the flue gas to chloride salts, which are removed by the dust separator 1 before the flue gas enters the desulfurization system.
Example 3
The temperature of the coal-fired flue gas is adjusted to 140 ℃ by using a heat exchanger 11, slaked lime with the water content of 4 percent and the grain diameter of more than 425 mu m (specifically 20-40 meshes) is sprayed into the coal-fired flue gas before the coal-fired flue gas enters a desulfurization system, HCl in the flue gas is converted into chloride, and the chloride is removed by a dust remover 1 before the flue gas enters the desulfurization system.
Through the experimental result of pilot scale, the calcium-chlorine ratio of the actual coal-fired flue gas is 9Under the working conditions, the slaked lime Ca (OH) in the example 1 is detected2The dechlorination efficiency in the coal-fired flue gas injection dechlorination test was 84.44%, whereas when using a dechlorinating agent in the particle size range of more than 425 μm, the dechlorination efficiency will be more than 90%, as the results of the study in connection with figure 2.
Therefore, the invention uses the powdery dry slaked lime with the grain diameter more than 425 μm as the dechlorinating agent, has wide sources and low price, and has higher dechlorinating efficiency. Compared with the existing mode of removing HCl gas through a desulfurizing tower, the method has the advantages that the corrosion of acidic gas to a tail flue and a desulfurizing facility is obviously reduced, the desulfurizing reaction environment is optimized, and the desulfurizing efficiency and the gypsum quality are improved; simultaneously, the synergistic emission reduction of SO is realized2And other acid gases, and the wastewater treatment capacity is reduced, so that the cost is reduced for the subsequent treatment of the desulfurization wastewater.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. A coal-fired flue gas dechlorination method is characterized by comprising the following steps:
after the coal-fired flue gas passes through the air preheater and before entering a desulfurization system, spraying slaked lime into the coal-fired flue gas to convert HCl in the flue gas into chloride;
preferably, the chloride salt is removed by a dust remover before the flue gas enters the desulfurization system;
preferably, the slaked lime is in a dry powder form.
2. The coal fired flue gas dechlorination method of claim 1 wherein the particle size of the slaked lime is greater than 425 μ ι η.
3. The coal fired flue gas dechlorination method of claim 1, wherein the slaked lime has a water content of less than 5%.
4. The method for dechlorinating the coal-fired flue gas according to claim 1, wherein the temperature of the coal-fired flue gas after the air preheater is 130-150 ℃.
5. The coal-fired flue gas dechlorination system according to any one of claims 1 to 4, comprising a slaked lime supply means, an air preheater, a spraying means, and a dust collector (1),
the air preheater and the dust remover (1) are sequentially arranged on the flue along the flowing direction of the flue gas;
the spraying mechanism is arranged on a tail flue behind the air preheater and is communicated with the slaked lime supply mechanism.
6. The coal-fired flue gas dechlorination system according to claim 5, wherein the slaked lime supply mechanism comprises a limestone slaker (2), a cyclone separator (5) and a powder feeding fan (4) which are sequentially communicated end to end,
a feed inlet is formed in the side surface of the cyclone separator (5), and is communicated with the limestone digester (2);
a fine powder outlet and a coarse powder outlet are respectively formed in the top end and the bottom end of the cyclone separator (5), the fine powder outlet is communicated with the inlet of the limestone digester (2), the coarse powder outlet is communicated with the powder feeding fan (4), and the powder feeding fan (4) is communicated with the injection mechanism;
preferably, the fine powder outlet is communicated with a desulfurization pulping system.
7. The coal-fired flue gas dechlorination system according to claim 6, wherein the slaked lime supply mechanism further comprises a storage bin (3), the coarse powder outlet is communicated with the storage bin (3), and the storage bin (3) is communicated with the powder feeding fan (4).
8. The coal-fired flue gas dechlorination system according to claim 7, wherein the injection mechanism comprises a plurality of spray guns uniformly distributed on the flue, each spray gun is fixedly arranged on the flue and extends into the flue, and all the spray guns are communicated with the discharge end of the powder feeding fan (4).
9. The coal-fired flue gas dechlorination system of claim 8, wherein the lance is provided with one or more nozzles.
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