CN110394056B - Industrial boiler flue gas dehumidification, desulfurization and denitrification system and method - Google Patents
Industrial boiler flue gas dehumidification, desulfurization and denitrification system and method Download PDFInfo
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- CN110394056B CN110394056B CN201910818925.XA CN201910818925A CN110394056B CN 110394056 B CN110394056 B CN 110394056B CN 201910818925 A CN201910818925 A CN 201910818925A CN 110394056 B CN110394056 B CN 110394056B
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- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 95
- 239000003546 flue gas Substances 0.000 title claims abstract description 95
- 238000000034 method Methods 0.000 title claims abstract description 29
- 238000007791 dehumidification Methods 0.000 title claims description 51
- 238000006477 desulfuration reaction Methods 0.000 title claims description 51
- 230000023556 desulfurization Effects 0.000 title claims description 51
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 81
- 239000012528 membrane Substances 0.000 claims abstract description 73
- 239000007788 liquid Substances 0.000 claims abstract description 62
- 238000010521 absorption reaction Methods 0.000 claims abstract description 57
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 45
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 45
- 239000006096 absorbing agent Substances 0.000 claims abstract description 40
- 239000003054 catalyst Substances 0.000 claims abstract description 40
- 239000012510 hollow fiber Substances 0.000 claims abstract description 40
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 31
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims abstract description 26
- 230000003009 desulfurizing effect Effects 0.000 claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 230000008929 regeneration Effects 0.000 claims abstract description 17
- 238000011069 regeneration method Methods 0.000 claims abstract description 17
- 238000005507 spraying Methods 0.000 claims abstract description 11
- 239000000835 fiber Substances 0.000 claims description 21
- 230000001105 regulatory effect Effects 0.000 claims description 16
- -1 vanadium metal oxides Chemical class 0.000 claims description 16
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 14
- 238000003860 storage Methods 0.000 claims description 14
- 229910052684 Cerium Inorganic materials 0.000 claims description 10
- 238000006243 chemical reaction Methods 0.000 claims description 10
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 9
- 230000000694 effects Effects 0.000 claims description 9
- 229910044991 metal oxide Inorganic materials 0.000 claims description 9
- 229910052720 vanadium Inorganic materials 0.000 claims description 9
- 239000004743 Polypropylene Substances 0.000 claims description 7
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 claims description 7
- 229910052921 ammonium sulfate Inorganic materials 0.000 claims description 7
- 235000011130 ammonium sulphate Nutrition 0.000 claims description 7
- 239000002131 composite material Substances 0.000 claims description 7
- 230000002209 hydrophobic effect Effects 0.000 claims description 7
- 229920002465 poly[5-(4-benzoylphenoxy)-2-hydroxybenzenesulfonic acid] polymer Polymers 0.000 claims description 7
- 229920001155 polypropylene Polymers 0.000 claims description 7
- 239000004408 titanium dioxide Substances 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 4
- 230000003647 oxidation Effects 0.000 claims description 4
- 238000007254 oxidation reaction Methods 0.000 claims description 4
- 238000001556 precipitation Methods 0.000 claims description 4
- 238000010790 dilution Methods 0.000 claims description 3
- 239000012895 dilution Substances 0.000 claims description 3
- 239000011148 porous material Substances 0.000 claims description 3
- 238000006277 sulfonation reaction Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims 1
- 238000005516 engineering process Methods 0.000 description 12
- 239000000779 smoke Substances 0.000 description 5
- 239000003337 fertilizer Substances 0.000 description 4
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical compound [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000007599 discharging Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000003245 coal Substances 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 230000003044 adaptive effect Effects 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000019635 sulfation Effects 0.000 description 1
- 238000005670 sulfation reaction Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
Classifications
-
- 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
- B01D53/22—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 by diffusion
-
- 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
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/24—Sulfates of ammonium
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05C—NITROGENOUS FERTILISERS
- C05C3/00—Fertilisers containing other salts of ammonia or ammonia itself, e.g. gas liquor
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
- C05F9/00—Fertilisers from household or town refuse
- C05F9/02—Apparatus for the manufacture
-
- 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
- B01D2255/00—Catalysts
- B01D2255/20—Metals or compounds thereof
- B01D2255/206—Rare earth metals
- B01D2255/2065—Cerium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/20—Metals or compounds thereof
- B01D2255/207—Transition metals
- B01D2255/20707—Titanium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/20—Metals or compounds thereof
- B01D2255/207—Transition metals
- B01D2255/20723—Vanadium
-
- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Environmental & Geological Engineering (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Biomedical Technology (AREA)
- Manufacturing & Machinery (AREA)
- Health & Medical Sciences (AREA)
- Inorganic Chemistry (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Treating Waste Gases (AREA)
Abstract
The invention relates to a system and a method for dehumidifying, desulfurizing and denitrating industrial boiler flue gas, wherein the system comprises a dehumidifying and desulfurizing system, a flue gas heater and a low-temperature denitrating system which are connected in sequence; the dehumidifying and desulfurizing system comprises a dehumidifying and desulfurizing tower, a booster fan and a hollow fiber membrane absorber; the bottom of the dehumidifying desulfurizing tower is provided with a flue gas inlet connected with a booster fan, the top of the dehumidifying desulfurizing tower is provided with a flue gas outlet, and the middle of the dehumidifying desulfurizing tower is provided with a hollow fiber membrane absorber for absorbing sulfur dioxide and water vapor; the input end of the hollow fiber membrane absorber is connected with the absorption liquid supply unit, and the output end is connected with the absorption liquid regeneration unit; the flue gas heater inlet is connected with a flue gas outlet connected with the top of the dehumidifying and desulfurizing tower; the low-temperature denitration system comprises a denitration tower, an ammonia water supply unit and a plurality of low-temperature SCR catalyst units; the flue gas inlet at the bottom of the denitration tower is connected with the outlet of the flue gas heater through an induced draft fan, the ammonia water supply unit is connected with an ammonia spraying grid arranged in a flue of the denitration tower, and a plurality of low-temperature SCR catalyst units are sequentially arranged in the denitration tower.
Description
Technical Field
The invention relates to the technical field of industrial boiler flue gas purification, in particular to a system and a method for dehumidifying, desulfurizing and denitrating industrial boiler flue gas.
Background
In China, the coal-fired industrial boiler is widely applied to various industrial production, and consumes about four hundred million tons of standard coal each year, which accounts for about one fourth of the total national coal consumption, and generates a large amount of pollutants such as sulfur dioxide and nitrogen oxides. Along with the increasing severity of environmental protection, the treatment of industrial boiler flue gas is also more and more strict.
However, the exhaust temperature of the industrial boiler is low, generally only 120-140 ℃, and the means suitable for purifying the industrial boiler smoke is relatively deficient. The low-temperature selective catalytic oxidation reduction SCR flue gas denitration technology is advanced over other flue gas denitration technologies by virtue of the advantages of low temperature, low dust, high denitration efficiency and the like. For the low-temperature SCR denitration technology, the core is a low-temperature SCR catalyst, researches show that the denitration efficiency of the Mn and Ce-based low-temperature SCR catalyst can reach 90 percent at the temperature of 200 ℃, but a water film is formed on the surface of the catalyst under the condition that water vapor exists, the water film can cause resistance to the combination of NOx, NH 3 and catalyst active sites, and SO 2 mainly causes the reduction of the catalyst activity through the sulfation of active components and the deposition of ammonium sulfate. Therefore, on the premise of unchanged flue gas temperature, the contents of water vapor and SO 2 in the flue gas are reduced, and the low-temperature catalyst is ensured to be in the optimal working environment, SO that the method is a key problem to be solved urgently at present.
At present, the common flue gas dehumidification technology mainly comprises a cooling condensation technology, a liquid absorption technology and a membrane separation technology, wherein the two technologies remove water vapor by changing the temperature and the pressure of the flue gas, which is not beneficial to the subsequent low-temperature denitration reaction of the flue gas; although the membrane separation technology can remove water vapor without changing the temperature and pressure of flue gas, desulfurization and denitrification cannot be simultaneously performed, so that the whole process line is longer and the process is complex.
Disclosure of Invention
Aiming at the problem of insufficient water resistance and sulfur resistance of the low-temperature denitration catalyst in the prior art, the invention provides the industrial boiler flue gas dehumidification, desulfurization and denitration system and the industrial boiler flue gas dehumidification, desulfurization and denitration method, which are reasonable in design, simple in process, low in energy consumption, free from harmful substances entering the environment and capable of prolonging the effective service life of the low-temperature SCR catalyst.
The invention is realized by the following technical scheme:
the industrial boiler flue gas dehumidification, desulfurization and denitration system comprises a dehumidification and desulfurization system, a flue gas heater and a low-temperature denitration system which are connected in sequence;
The dehumidification and desulfurization system comprises a dehumidification and desulfurization tower, a booster fan and a hollow fiber membrane absorber; the bottom of the dehumidifying desulfurizing tower is provided with a flue gas inlet connected with a booster fan, the top of the dehumidifying desulfurizing tower is provided with a flue gas outlet, and the middle of the dehumidifying desulfurizing tower is provided with a hollow fiber membrane absorber for absorbing sulfur dioxide and water vapor; the input end of the hollow fiber membrane absorber is connected with the absorption liquid supply unit, and the output end is connected with the absorption liquid regeneration unit;
the flue gas heater inlet is connected with a flue gas outlet connected with the top of the dehumidifying and desulfurizing tower;
the low-temperature denitration system comprises a denitration tower, an ammonia water supply unit and a plurality of low-temperature SCR catalyst units; the flue gas inlet at the bottom of the denitration tower is connected with the outlet of the flue gas heater through an induced draft fan, the ammonia water supply unit is connected with an ammonia spraying grid arranged in a flue of the denitration tower, and a plurality of low-temperature SCR catalyst units are sequentially arranged in the denitration tower.
Preferably, the hollow fiber membrane absorber consists of two hollow fiber membranes connected in series, and the bottom is a hydrophobic polypropylene fiber membrane for removing sulfur dioxide in flue gas; the upper part is a SPEEK/PES hydrophilic composite membrane for removing water vapor in flue gas.
Preferably, the absorption liquid supply unit includes an absorption liquid transfer pump, an input adjusting valve, and an absorption liquid storage tank sequentially connected to an input end of the hollow fiber membrane absorber.
Preferably, the absorption liquid regeneration unit comprises an output regulating valve, a pressure maintaining pump and an absorption liquid regeneration tank which are sequentially connected to the output end of the hollow fiber membrane absorber.
Preferably, the ammonia water supply unit comprises an ammonia water storage tank, an ammonia water metering pump, an ammonia evaporator and an ammonia buffer tank which are sequentially connected, and the output end of the ammonia buffer tank is connected with an ammonia spraying grid.
Preferably, the low-temperature SCR catalyst unit comprises three layers of low-temperature SCR catalyst units sequentially arranged along the flue gas direction.
An industrial boiler flue gas dehumidifying, desulfurizing and denitrating method based on the system of any one of the above steps,
Step 1, flue gas enters a desulfurization and dehumidification tower and is subjected to desulfurization and dehumidification through a hollow fiber membrane absorber; the absorption liquid storage tank is connected with an absorption liquid conveying pump through an input regulating valve, the absorption liquid is conveyed to the tube side of the fiber membrane absorber, the output regulating valve and the pressure maintaining pump regulate the vacuum degree in the tube side of the fiber membrane, and meanwhile, the absorption liquid absorbing sulfur dioxide and water vapor is conveyed to an absorption liquid regeneration tank, and ammonium sulfate is generated in the absorption liquid regeneration tank through oxidation precipitation;
Step 2, the flue gas is discharged from the top of the dehumidifying desulfurization tower after being dehumidified and desulfurized, enters a flue gas heater to be heated to the denitration temperature, and enters the bottom of the denitration tower by an induced draft fan; the supplied ammonia water is sprayed into a flue through an ammonia spraying grid, and is fully mixed with the flue gas entering from the bottom of the denitration tower, and then denitration reaction is sequentially carried out in a plurality of low-temperature SCR catalyst units.
Preferably, in the step 1, the internal circulation absorption liquid of the tube side of the hollow fiber membrane absorber is dilute ammonia water, the mass concentration is 0.5-0.8%, and the vacuum degree in the hollow fiber membrane absorber is maintained at 0.06-0.1 MPa; the speed of the flue gas which is introduced into the dehumidifying desulfurizing tower is 0.1 m/s-0.6 m/s, the temperature is 70-90 ℃, and the gas-liquid ratio is (75-100): 1.
Preferably, in the step 1, the pore diameter of the bottom hydrophobic polypropylene fiber membrane is 0.075-0.82 mu m; the sulfonation degree of the upper SPEEK/PES hydrophilic composite membrane is 40% -60%.
Preferably, in the step 2, ammonia water is conveyed to an ammonia water evaporator through an ammonia water metering pump, ammonia water or liquid ammonia is converted into gaseous NH 3 through the ammonia water evaporator and is output to an ammonia buffer tank from the top of the ammonia water evaporator, and the gaseous NH 3 is mixed with air in the ammonia buffer tank for dilution and then sprayed into a flue through an ammonia spraying grid;
After the ammonia gas and the air are mixed and diluted, the volume ratio of the ammonia gas to the air is 1: (2.5-4); the molar ratio of ammonia to NOx in the low-temperature denitration process is (1-1.25): 1. the denitration adopts titanium dioxide as a carrier, and cerium and vanadium metal oxides as low-temperature SCR catalysts of active components, and the reaction activity temperature is only 100-180 ℃.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention discloses a dehumidification desulfurization and denitrification system for industrial boiler flue gas at low temperature, which combines a membrane removal technology with a low-temperature SCR denitrification technology to form a combined dehumidification desulfurization and denitrification technology. The fiber membrane dehumidification desulfurization method utilizes the difference of gas permeation rates to realize a gas separation process, and because the pressure difference of two sides of the membrane is utilized, smoke components tend to the permeation side in the fiber membrane, and because the surface of the fiber membrane is provided with a corresponding selective layer, the selective separation effect is realized, sulfur dioxide and water vapor can pass through, other components can not pass through, the desulfurization dehumidification process can be realized in one desulfurization tower, and the process has no heat exchange, so the temperature of smoke is not influenced, ammonium sulfate generated in the process can be used as chemical fertilizer to be produced, and part of water vapor in the smoke is recovered to realize the recycling of resources.
Furthermore, the denitration adopts titanium dioxide as a carrier, and cerium, vanadium metal oxide and the like as low-temperature SCR catalysts of active components, wherein the reaction activity temperature is only 100-180 ℃ and is 120-300 ℃ lower than that of the conventional low-temperature SCR catalysts.
The method for dehumidifying, desulfurizing and denitrating the industrial boiler flue gas at low temperature has the advantages of simple process, low energy consumption, no harmful substances entering the environment, capability of prolonging the effective service life of the low-temperature SCR catalyst and the like, and is convenient for popularization and application in industrial boilers.
Drawings
FIG. 1 is a flow chart of a low temperature dehumidification, desulfurization and denitrification process of the invention
In the figure: the device comprises a dehumidifying desulfurizing tower 1, a booster fan 2, a hydrophobic polypropylene fiber membrane 3a, a SPEEK/PES hydrophilic composite membrane 3b, an absorption liquid storage tank 4, an absorption liquid conveying pump 5, a regulating valve 6, a pressure maintaining pump 7, an absorption liquid regenerating tank 8, a flue gas heater 9, an induced draft fan 10, an ammonia water storage tank 11, an ammonia water metering pump 12, an ammonia evaporator 13, an ammonia buffer tank 14 and three layers of low-temperature SCR catalyst units 15a, 15b and 15c.
Detailed Description
The invention will now be described in further detail with reference to specific examples, which are intended to illustrate, but not to limit, the invention.
The invention relates to a dehumidification, desulfurization and denitration system of an industrial boiler, which comprises a dehumidification and desulfurization system and a low-temperature denitration system. The dehumidification and desulfurization system is used for desulfurizing the flue gas and simultaneously dehumidifying, the bottom of the dehumidification and desulfurization tower 1 is provided with an air inlet which is connected with the booster fan 2 through a pipeline, and the flue gas enters the desulfurization and dehumidification tower 1 and is desulfurized and dehumidified firstly through the hollow fiber membrane absorber. The absorption liquid storage tank 4 is connected to an absorption liquid delivery pump 5 through an input regulating valve, delivers the absorption liquid to the inside of the hollow fiber membrane absorber tube side and regulates the vacuum degree in the fiber membrane tube side by an output regulating valve 6 and a pressure maintaining pump 7. The absorption liquid absorbing sulfur dioxide and water vapor is conveyed to an absorption liquid regeneration tank 8, and ammonium sulfate generated by oxidation and precipitation in the absorption liquid regeneration tank 8 can be used as a fertilizer raw material. The flue gas is discharged from the top of the desulfurization and dehumidification tower 1 to enter a flue gas heater 9 after dehumidification and desulfurization, and enters the bottom of the denitration tower from a draught fan 10 after being heated to the denitration temperature. The denitration adopts titanium dioxide as a carrier, and cerium, vanadium metal oxide and the like as active components, and the reaction activity temperature is only 100-180 ℃ which is 120-300 ℃ lower than that of the conventional low-temperature SCR catalyst. The membrane gas absorption method realized by the hollow fiber membrane absorber has compact equipment and higher effective mass transfer surface area and mass transfer rate, so that the fiber membrane dehumidification desulfurization method can realize the desulfurization and dehumidification process in one desulfurization tower without influencing the temperature of flue gas, ammonium sulfate generated in the process can be produced as a chemical fertilizer, the influence of water vapor and sulfur dioxide on the low-temperature SCR catalyst is effectively reduced, and the effective service life of the low-temperature SCR catalyst is prolonged.
Specifically, as shown in fig. 1, the industrial boiler flue gas dehumidifying, desulfurizing and denitrating system comprises a dehumidifying, desulfurizing system and a low-temperature denitrating system;
The dehumidification and desulfurization system is used for desulfurizing the flue gas and simultaneously dehumidifying the flue gas and comprises a dehumidification and desulfurization tower 1, a booster fan 2, a hollow fiber membrane absorber, an output regulating valve 6, a pressure maintaining pump 7, an absorption liquid storage tank 4, an absorption liquid conveying pump 5 and an absorption liquid regeneration tank 8, wherein the output regulating valve 6, the pressure maintaining pump 7, the absorption liquid storage tank 4, the absorption liquid conveying pump 5 and the absorption liquid regeneration tank 8 are arranged corresponding to the hollow fiber membrane absorber. The bottom of the dehumidification and desulfurization tower 1 is provided with an air inlet which is connected with a booster fan 2 through a pipeline, and flue gas enters the desulfurization and dehumidification tower 1 and is subjected to desulfurization and dehumidification through a hollow fiber membrane absorber. The absorption liquid storage tank 4 is connected with the absorption liquid delivery pump 5 through an input regulating valve, the absorption liquid is delivered to the tube side of the fiber membrane absorber, the vacuum degree in the tube side of the fiber membrane is regulated by an output regulating valve 6 and a pressure maintaining pump 7, and the absorption liquid absorbing sulfur dioxide and water vapor is delivered to the absorption liquid regeneration tank 8, and ammonium sulfate generated in the absorption liquid regeneration tank 8 through oxidation precipitation can be used as a fertilizer raw material. The flue gas is discharged from the top of the dehumidification and desulfurization tower 1 after dehumidification and desulfurization, enters a flue gas heater 9 to be heated to the denitration temperature, and enters the bottom of the denitration tower by an induced draft fan 10.
The low-temperature denitration system comprises an ammonia water storage tank 11, an ammonia water metering pump 12, an ammonia evaporator 13, an ammonia buffer tank 14 and three layers of low-temperature SCR catalyst units 15a,15b and 15c, and is used for carrying out low-temperature denitration on flue gas. The bottom of the ammonia water storage tank 11 is connected with an ammonia water metering pump 12, ammonia water is conveyed to an ammonia water evaporator 13 through the ammonia water metering pump 12, ammonia water or liquid ammonia is converted into gaseous NH 3 through the ammonia water evaporator 13 and is output to an ammonia buffer tank 14 from the top of the ammonia water evaporator 13, the ammonia water or the liquid ammonia is mixed with air in the ammonia buffer tank 14 for dilution, then the ammonia water or the liquid ammonia is sprayed into a flue through an ammonia spraying grid and is fully mixed with flue gas, and then denitration reaction is carried out in a low-temperature SCR catalyst unit.
In the scheme of the invention, the hollow fiber membrane absorber consists of two hollow fiber membranes connected in series, and the bottom is a hydrophobic polypropylene fiber membrane 3a for removing sulfur dioxide in flue gas; the upper part is a SPEEK/PES hydrophilic composite membrane 3b for removing water vapor in the flue gas.
In the scheme of the invention, the internal circulating absorption liquid in the tube pass of the hollow fiber membrane absorber is dilute ammonia water, the mass concentration is 0.5-0.8%, the temperature is 70-90 ℃, and the gas-liquid ratio is (75-100): 1.
In the above-described aspect of the present invention, the hollow fiber membrane absorber is internally connected to the pressure maintaining pump 7, and the vacuum degree in the hollow fiber membrane absorber is maintained at 0.06MPa to 0.1MPa.
In the above scheme of the invention, the pore diameter of the bottom hydrophobic polypropylene fiber membrane is 0.075-0.82 μm.
In the above scheme of the invention, the sulfonation degree of the upper SPEEK/PES hydrophilic composite membrane is 40% -60%.
In the scheme of the invention, the smoke temperature in the dehumidification and desulfurization process is 70-90 DEG C
In the scheme of the invention, the speed of the flue gas which is introduced into the dehumidification and desulfurization tower is 0.1 m/s-0.6 m/s.
In the scheme of the invention, the molar ratio of ammonia to NOx in the low-temperature denitration process is controlled to be (1-1.25): 1. After ammonia gas and air are mixed and diluted, the volume ratio of the ammonia gas to the air is controlled at 1: (2.5-4).
In the scheme of the invention, the low-temperature denitration catalyst is a low-temperature SCR catalyst taking anatase type nano titanium dioxide as a carrier and cerium, vanadium metal oxide and the like as active components. The reaction activity temperature is 100-180 ℃, the NOx concentration adaptive range is that the denitration efficiency is more than 80%.
Example 1
1) And conveying the flue gas to a dehumidification and desulfurization tower 1 through a booster fan 2, and carrying out dehumidification and desulfurization treatment on the flue gas through a hollow fiber membrane absorber formed by connecting two hollow fiber membranes in series, wherein the mass concentration of an absorption liquid is 0.5%, the temperature is 70 ℃, the gas-liquid ratio is 75:1, and the vacuum degree in the tube side of the fiber membrane absorber is 0.06MPa.
2) The dehumidified and desulfurized flue gas enters a flue gas heater to be heated to 100 ℃, and then enters a denitration tower through a draught fan.
3) The flue gas with the temperature of 100 ℃ enters a low-temperature denitration tower to be subjected to low-temperature denitration treatment, the low-temperature denitration catalyst is a low-temperature SCR catalyst taking anatase type nano titanium dioxide as a carrier and cerium, vanadium metal oxide and the like as active components, and the molar ratio of ammonia to NOx in the low-temperature denitration process is controlled at 1:1. mixing diluted ammonia gas with air, wherein the volume ratio of the diluted ammonia gas to the air is 1:2.5.
4) And (3) discharging the flue gas subjected to low-temperature denitration from a chimney.
Example 2
1) And the flue gas is conveyed to a dehumidification and desulfurization tower 1 through a booster fan 2, dehumidification and desulfurization treatment are carried out on the flue gas through a hollow fiber membrane absorber formed by connecting two hollow fiber membranes in series, the mass concentration of the absorption liquid is 0.8%, the temperature is 90 ℃, the gas-liquid ratio is 100:1, and the vacuum degree in the tube side of the fiber membrane absorber is 0.1MPa.
2) The dehumidified and desulfurized flue gas enters a flue gas heater to be heated to 140 ℃, and then enters a denitration tower through a draught fan.
3) The flue gas with the temperature of 140 ℃ enters a low-temperature denitration tower to be subjected to low-temperature denitration treatment, the low-temperature denitration catalyst is a low-temperature SCR catalyst which takes anatase type nano titanium dioxide as a carrier and cerium, vanadium metal oxide and the like as active components, and the molar ratio of ammonia to NOx in the low-temperature denitration process is controlled at 1.25:1. mixing diluted ammonia gas with air, wherein the volume ratio of the diluted ammonia gas to the air is 1:4.
4) And (3) discharging the flue gas subjected to low-temperature denitration from a chimney.
Example 3
1) And conveying the flue gas to a dehumidification and desulfurization tower 1 through a booster fan 2, and carrying out dehumidification and desulfurization treatment on the flue gas through a hollow fiber membrane absorber formed by connecting two hollow fiber membranes in series, wherein the mass concentration of an absorption liquid is 0.6%, the temperature is 80 ℃, the gas-liquid ratio is 90:1, and the vacuum degree in the tube side of the fiber membrane absorber is 0.08MPa.
2) The dehumidified and desulfurized flue gas enters a flue gas heater to be heated to 180 ℃, and then enters a denitration tower through a draught fan.
3) The flue gas with the temperature of 140 ℃ enters a low-temperature denitration tower to be subjected to low-temperature denitration treatment, the low-temperature denitration catalyst is a low-temperature SCR catalyst which takes anatase type nano titanium dioxide as a carrier and cerium, vanadium metal oxide and the like as active components, and the molar ratio of ammonia to NOx in the low-temperature denitration process is controlled at 1.2:1. mixing diluted ammonia gas with air, wherein the volume ratio of the diluted ammonia gas to the air is 1:3.
4) And (3) discharging the flue gas subjected to low-temperature denitration from a chimney.
Claims (2)
1. The industrial boiler flue gas dehumidification, desulfurization and denitration system is characterized by comprising a dehumidification and desulfurization system, a flue gas heater (9) and a low-temperature denitration system which are connected in sequence;
The dehumidification and desulfurization system comprises a dehumidification and desulfurization tower (1), a booster fan (2) and a hollow fiber membrane absorber; the bottom of the dehumidification desulfurizing tower (1) is provided with a flue gas inlet connected with a booster fan (2), the top of the dehumidification desulfurizing tower is provided with a flue gas outlet, and the middle of the dehumidification desulfurizing tower is provided with a hollow fiber membrane absorber for absorbing sulfur dioxide and water vapor; the input end of the hollow fiber membrane absorber is connected with the absorption liquid supply unit, and the output end is connected with the absorption liquid regeneration unit;
the inlet of the flue gas heater (9) is connected with a flue gas outlet connected with the top of the dehumidification and desulfurization tower (1);
The low-temperature denitration system comprises a denitration tower, an ammonia water supply unit and a plurality of low-temperature SCR catalyst units; the flue gas inlet at the bottom of the denitration tower is connected with the outlet of a flue gas heater (9) through an induced draft fan (10), the ammonia water supply unit is connected with an ammonia spraying grid arranged in a flue gas inlet of the denitration tower, and a plurality of low-temperature SCR catalyst units are sequentially arranged in the denitration tower; the low-temperature SCR catalyst adopts titanium dioxide as a carrier, cerium and vanadium metal oxides as active components, and the reaction activity temperature is only 100-180 ℃;
The hollow fiber membrane absorber consists of two hollow fiber membranes connected in series, and the bottom is a hydrophobic polypropylene fiber membrane (3 a) for removing sulfur dioxide in the flue gas; the upper part is a SPEEK/PES hydrophilic composite membrane (3 b) for removing water vapor in the flue gas;
the absorption liquid supply unit comprises an absorption liquid delivery pump (5), an input regulating valve and an absorption liquid storage tank (4) which are sequentially connected to the input end of the hollow fiber membrane absorber;
the absorption liquid regeneration unit comprises an output regulating valve (6), a pressure maintaining pump (7) and an absorption liquid regeneration tank (8) which are sequentially connected to the output end of the hollow fiber membrane absorber;
the ammonia water supply unit comprises an ammonia water storage tank (11), an ammonia water metering pump (12), an ammonia water evaporator (13) and an ammonia buffer tank (14) which are sequentially connected, and the output end of the ammonia buffer tank (14) is connected with an ammonia spraying grid;
The low temperature SCR catalyst unit comprises three layers of low temperature SCR catalyst units (15 a,15b,15 c) arranged in sequence in the direction of the flue gas.
2. A method for dehumidifying, desulfurizing and denitrating industrial boiler flue gas, which is characterized by comprising the following steps based on the system of claim 1,
Step 1, flue gas enters a desulfurization and dehumidification tower (1), and is desulfurized and dehumidified through a hollow fiber membrane absorber; the absorption liquid storage tank (4) is connected with the absorption liquid conveying pump (5) through an input regulating valve, the absorption liquid is conveyed to the tube side of the fiber membrane absorber, the vacuum degree in the tube side of the fiber membrane is regulated by an output regulating valve (6) and a pressure maintaining pump (7), and meanwhile, the absorption liquid absorbing sulfur dioxide and water vapor is conveyed to the absorption liquid regeneration tank (8), and ammonium sulfate is generated in the absorption liquid regeneration tank (8) through oxidation precipitation;
Step 2, the flue gas is discharged from the top of the dehumidification and desulfurization tower (1) after dehumidification and desulfurization without heat exchange, enters a flue gas heater (9) for heating to a denitration temperature, and enters the bottom of the denitration tower from an induced draft fan (10); spraying the supplied ammonia water into a flue through an ammonia spraying grid, fully mixing the ammonia water with the flue gas entering from the bottom of the denitration tower, and sequentially carrying out denitration reaction in a plurality of low-temperature SCR catalyst units;
In the step 1, the internal circulation absorption liquid of the tube side of the hollow fiber membrane absorber is dilute ammonia water, the mass concentration is 0.5-0.8%, and the vacuum degree in the hollow fiber membrane absorber is maintained at 0.06-0.1 MPa; the speed of the flue gas which is introduced into the dehumidifying desulfurizing tower is 0.1 m/s-0.6 m/s, the temperature is 70-90 ℃, and the gas-liquid ratio is (75-100): 1;
In the step 1, the pore diameter of the bottom hydrophobic polypropylene fiber membrane is 0.075-0.82 mu m; the sulfonation degree of the upper SPEEK/PES hydrophilic composite membrane is 40-60%;
in the step 2, ammonia water is conveyed to an ammonia water evaporator (13) through an ammonia water metering pump (12), the ammonia water is converted into ammonia gas through the ammonia water evaporator (13), the ammonia gas is output to an ammonia buffer tank (14) from the top of the ammonia water evaporator (13), and the ammonia gas is mixed with air in the ammonia buffer tank (14) for dilution and then is sprayed into a flue through an ammonia spraying grid;
After the ammonia gas and the air are mixed and diluted, the volume ratio of the ammonia gas to the air is 1: (2.5-4); the molar ratio of ammonia to NOx in the low-temperature denitration process is (1-1.25): 1, a step of; the denitration adopts titanium dioxide as a carrier, and cerium and vanadium metal oxides as low-temperature SCR catalysts of active components, and the reaction activity temperature is only 100-180 ℃.
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