CN117815868A - Recycling recovery process for fluorine component in fluorobenzene production tail gas - Google Patents
Recycling recovery process for fluorine component in fluorobenzene production tail gas Download PDFInfo
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- CN117815868A CN117815868A CN202311529146.0A CN202311529146A CN117815868A CN 117815868 A CN117815868 A CN 117815868A CN 202311529146 A CN202311529146 A CN 202311529146A CN 117815868 A CN117815868 A CN 117815868A
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- PYLWMHQQBFSUBP-UHFFFAOYSA-N monofluorobenzene Chemical compound FC1=CC=CC=C1 PYLWMHQQBFSUBP-UHFFFAOYSA-N 0.000 title claims abstract description 52
- 229910052731 fluorine Inorganic materials 0.000 title claims abstract description 38
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 title claims abstract description 33
- 239000011737 fluorine Substances 0.000 title claims abstract description 33
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 28
- 238000004064 recycling Methods 0.000 title claims abstract description 23
- 238000011084 recovery Methods 0.000 title claims abstract description 20
- 239000007789 gas Substances 0.000 claims abstract description 221
- 238000005406 washing Methods 0.000 claims abstract description 172
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 126
- 238000001816 cooling Methods 0.000 claims abstract description 79
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 49
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 43
- 238000000034 method Methods 0.000 claims abstract description 41
- 230000008569 process Effects 0.000 claims abstract description 35
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 claims abstract description 28
- 229910000040 hydrogen fluoride Inorganic materials 0.000 claims abstract description 25
- 238000009833 condensation Methods 0.000 claims abstract description 17
- 230000005494 condensation Effects 0.000 claims abstract description 17
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 15
- 235000013024 sodium fluoride Nutrition 0.000 claims abstract description 14
- 239000011775 sodium fluoride Substances 0.000 claims abstract description 14
- 238000001179 sorption measurement Methods 0.000 claims description 71
- 239000007788 liquid Substances 0.000 claims description 60
- 239000007921 spray Substances 0.000 claims description 43
- 239000003513 alkali Substances 0.000 claims description 41
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 32
- 238000003795 desorption Methods 0.000 claims description 27
- 239000011347 resin Substances 0.000 claims description 27
- 229920005989 resin Polymers 0.000 claims description 27
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 23
- 239000003507 refrigerant Substances 0.000 claims description 23
- 238000010257 thawing Methods 0.000 claims description 22
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 17
- 229910021529 ammonia Inorganic materials 0.000 claims description 16
- 238000000746 purification Methods 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 9
- 239000008367 deionised water Substances 0.000 claims description 7
- 229910021641 deionized water Inorganic materials 0.000 claims description 7
- 238000005507 spraying Methods 0.000 claims description 5
- 238000011144 upstream manufacturing Methods 0.000 claims description 4
- 238000007791 dehumidification Methods 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 3
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims 3
- 230000007613 environmental effect Effects 0.000 abstract description 3
- 238000006243 chemical reaction Methods 0.000 description 19
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 17
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 description 13
- 239000010410 layer Substances 0.000 description 12
- 238000010521 absorption reaction Methods 0.000 description 11
- 230000000694 effects Effects 0.000 description 10
- 230000001976 improved effect Effects 0.000 description 9
- 239000000047 product Substances 0.000 description 9
- 230000002829 reductive effect Effects 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- 229910002089 NOx Inorganic materials 0.000 description 6
- 239000007791 liquid phase Substances 0.000 description 6
- 239000003344 environmental pollutant Substances 0.000 description 5
- 125000001153 fluoro group Chemical group F* 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
- 238000002844 melting Methods 0.000 description 5
- 230000008018 melting Effects 0.000 description 5
- 231100000719 pollutant Toxicity 0.000 description 5
- 230000001105 regulatory effect Effects 0.000 description 5
- 238000007086 side reaction Methods 0.000 description 5
- 239000002351 wastewater Substances 0.000 description 5
- 238000009835 boiling Methods 0.000 description 4
- 239000012267 brine Substances 0.000 description 4
- 238000005796 dehydrofluorination reaction Methods 0.000 description 4
- 238000012544 monitoring process Methods 0.000 description 4
- 238000010992 reflux Methods 0.000 description 4
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 239000000945 filler Substances 0.000 description 3
- 230000000670 limiting effect Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000000197 pyrolysis Methods 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000018044 dehydration Effects 0.000 description 2
- 238000006297 dehydration reaction Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- -1 fluoro compound Chemical class 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 230000036961 partial effect Effects 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Chemical compound [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 230000001502 supplementing effect Effects 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- 239000012855 volatile organic compound Substances 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 206010024769 Local reaction Diseases 0.000 description 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-N Nitrous acid Chemical compound ON=O IOVCWXUNBOPUCH-UHFFFAOYSA-N 0.000 description 1
- 206010047700 Vomiting Diseases 0.000 description 1
- PZUUTJLAUKMLTH-UHFFFAOYSA-N [F].C1=CC=CC=C1 Chemical compound [F].C1=CC=CC=C1 PZUUTJLAUKMLTH-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 231100000570 acute poisoning Toxicity 0.000 description 1
- FMKDDEABMQRAKW-UHFFFAOYSA-N aniline;hydrofluoride Chemical compound F.NC1=CC=CC=C1 FMKDDEABMQRAKW-UHFFFAOYSA-N 0.000 description 1
- 231100000739 chronic poisoning Toxicity 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 230000015271 coagulation Effects 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000012954 diazonium Substances 0.000 description 1
- 238000006193 diazotization reaction Methods 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-O diazynium Chemical compound [NH+]#N IJGRMHOSHXDMSA-UHFFFAOYSA-O 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 208000002173 dizziness Diseases 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000003546 flue gas Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000003116 impacting effect Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000000752 ionisation method Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 150000004812 organic fluorine compounds Chemical class 0.000 description 1
- 239000012044 organic layer Substances 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000011833 salt mixture Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 235000010288 sodium nitrite Nutrition 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 208000024891 symptom Diseases 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
- 239000002918 waste heat Substances 0.000 description 1
- 238000004065 wastewater treatment Methods 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
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/77—Liquid phase processes
- B01D53/78—Liquid phase processes with gas-liquid contact
-
- 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
- B01D53/002—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 condensation
-
- 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
- B01D53/02—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 adsorption, e.g. preparative gas chromatography
- B01D53/04—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 adsorption, e.g. preparative gas chromatography with stationary adsorbents
-
- 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
- B01D53/14—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 absorption
- B01D53/1406—Multiple stage absorption
-
- 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
- B01D53/14—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 absorption
- B01D53/18—Absorbing units; Liquid distributors therefor
-
- 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
- B01D53/30—Controlling by gas-analysis apparatus
-
- 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
- B01D53/343—Heat recovery
-
- 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
- B01D53/74—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
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/20—Nitrogen oxides; Oxyacids of nitrogen; Salts thereof
- C01B21/36—Nitrogen dioxide (NO2, N2O4)
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B7/00—Halogens; Halogen acids
- C01B7/19—Fluorine; Hydrogen fluoride
- C01B7/191—Hydrogen fluoride
- C01B7/195—Separation; Purification
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2256/00—Main component in the product gas stream after treatment
- B01D2256/26—Halogens or halogen compounds
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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
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/30—Capture or disposal of greenhouse gases of perfluorocarbons [PFC], hydrofluorocarbons [HFC] or sulfur hexafluoride [SF6]
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Environmental & Geological Engineering (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Inorganic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a recycling recovery process of fluorine components in fluorobenzene production tail gas, which comprises synthesis tail gas generated in the fluorobenzene synthesis process, wherein the synthesis tail gas is subjected to deep cooling condensation by a deep cooling unit to form hydrogen fluoride with more than 70 weight percent, and then the hydrogen fluoride is subjected to deep cooling to form deep cooling tail gas which enters a washing unit to deeply recover HF components in the deep cooling tail gas, so that hydrofluoric acid products with more than 45 weight percent of F components are generated; in the washing unit, the deep cooling tail gas is sequentially subjected to water washing by a multi-stage water washing tower and alkaline washing by a first-stage alkaline washing tower to further absorb residual hydrogen fluoride components in the deep cooling tail gas, the alkaline washing period of the first-stage alkaline washing tower is set, or the concentration limit value of sodium fluoride in alkaline liquor sprayed in the first-stage alkaline washing tower is set, and a 1 st-stage water washing tower and the first-stage alkaline washing tower in the multi-stage water washing tower are periodically switched and alternately used. The method has the advantages of simple process, cleanness, environmental protection, stability, high efficiency, controllable components, high recovery rate of fluorine element and long service life of equipment.
Description
Technical Field
The invention belongs to the field of chemical tail gas treatment, relates to the treatment of tail gas pollutants generated in the production process of organofluorine chemical industry, and in particular relates to a recycling recovery process of fluorine components in fluorobenzene production tail gas.
Background
Fluorobenzene is an important chemical intermediate and has wide application in the industries of medicines, dyes and the like. The fluorine benzene production has higher profit, but a large amount of fluorine-containing wastewater, waste gas and waste residue pollutants are generated in the production process besides a large amount of concentrated waste HF. HF has great harm to human health, and long-term inhalation of HF with low concentration may cause chronic poisoning, emesis, dizziness and other symptoms, when HF concentration is greater than 30 μg/m 3 Acute poisoning can be caused. To date, there is no efficient, low cost method to solve the HF contamination problem of fluorobenzene production. In order to recover HF in the exhaust gas, lv Zhimin et al [ Lv Zhimin, zhang Yuqing, tang An et al, fluorobenzene clean production process, chemical world, 2002.12 ] studied a water washing recovery process, and a three-stage water circulation method is adopted to absorb HF in the exhaust gas, and a coagulation sedimentation and activated carbon adsorption method is adopted to treat fluorine-containing wastewater, so that although part of HF can be recovered, the recovery process route is long, wastewater pollutants exist, and a certain amount of HF pollution components are also contained in the treated exhaust gas. In order to reduce HF pollution components in the discharged tail gas as much as possible, research and application of alkali liquor absorption are also available, but because of lower solubility of sodium fluoride, system scaling and blockage seriously affect normal operation of the system, and a large amount of fluorine-containing wastewater is generated.
With the development of the fluoride industry, the problem of HF pollution is more and more prominent, and the development of the fluoride industry is severely restricted by the problem of HF pollution.
The invention aims at the problems and develops a recycling recovery process for the fluorine component in the fluorobenzene production tail gas.
Disclosure of Invention
The invention aims to solve the technical problems and provide the recycling recovery process for the fluorine component in the fluorobenzene production tail gas, which has the advantages of simple process, cleanness, environmental protection, stability, high efficiency, controllable components, high recovery rate of fluorine element, low operation cost and long service life of equipment.
The method comprises the steps of synthesizing tail gas generated in the fluorobenzene synthesizing process, and is characterized in that the synthesized tail gas is subjected to deep cooling by a deep cooling unit to form deep cooling tail gas after more than 70 weight percent of hydrogen fluoride is condensed, and the deep cooling tail gas enters a washing unit to deeply recover HF components in the deep cooling tail gas, so that hydrofluoric acid products containing more than 45 weight percent of F components are generated;
in the washing unit, the deep cooling tail gas is sequentially subjected to water washing by a multi-stage water washing tower and alkaline washing by a first-stage alkaline washing tower to further absorb residual hydrogen fluoride components in the deep cooling tail gas, the alkaline washing period of the first-stage alkaline washing tower is set, or the concentration limit value of sodium fluoride in alkaline liquor sprayed in the first-stage alkaline washing tower is set, and a 1 st-stage water washing tower and the first-stage alkaline washing tower in the multi-stage water washing tower are periodically switched and alternately used.
The washing unit comprises at least 4-stage water washing towers, a first-stage alkaline washing tower and a water washing demisting tower which are connected in series, and the condensed cryogenic tail gas is sequentially subjected to water washing by the 4-stage water washing towers, alkaline washing by the first-stage alkaline washing tower and demisting by the water washing demisting tower.
Two circulating liquid tanks are correspondingly arranged at the bottoms of a 1 st stage water washing tower and a first stage alkaline washing tower in the 4-stage water washing tower, one circulating liquid tank is a circulating spray water tank, when the 1 st stage water washing tower of the 4-stage water washing tower works, circulating spray liquid is collected by the circulating spray water tank and then returned to the tower, and when the first stage alkaline washing tower works, circulating spray liquid is collected by the circulating alkaline liquid tank and then returned to the tower; and the bottom of the circulating alkali liquid tank is led out to obtain hydrofluoric acid products with more than 45 weight percent of F-containing components.
Monitoring the concentration of sodium fluoride in a circulating alkali liquid tank of a tower used as a primary alkali washing tower, when the concentration exceeds 3wt%, directly switching and introducing the deep cooling tail gas entering a washing unit into the tower, simultaneously switching the circulating liquid tank of the tower, introducing circulating spray water in a circulating spray water tank into the tower for circulating spray, namely switching the alkali washing function of the tower into a 1 st-stage water washing function;
meanwhile, the original 1 st-stage water washing tower is switched into a first-stage alkaline washing tower, tail gas from the 4 th-stage water washing tower in the 4-stage water washing tower is introduced into the tower, meanwhile, a circulating liquid tank of the tower is switched, and circulating alkali liquor in the circulating alkali liquid tank is introduced into the tower for circulating spraying.
When the circulating alkali liquor is used as the 1 st-stage washing tower, circulating alkali liquor is continuously and evenly discharged from the corresponding circulating alkali liquor tank to enter the corresponding circulating spraying water tank, and when the discharge amount reaches 50-60% of the total circulating alkali liquor amount by volume, the discharging is stopped, and then fresh sodium hydroxide solution is supplemented into the circulating alkali liquor tank to reach the original liquid level.
And uniformly and continuously supplementing deionized water to the water washing demisting tower, and reversely and sequentially feeding part of washing water discharged from the bottom of the tower into the multi-stage water washing tower.
The washing tail gas after HF removal from the washing unit sequentially enters an adsorption unit for removing fluorobenzene and a denitration unit for denitration and purification and is discharged;
wherein the adsorption unit comprises at least 2 resin adsorption towers, one adsorption tower and one desorption tower are alternately performed; and (3) introducing 10-20% by volume of adsorption tail gas from the other resin adsorption tower into the resin adsorption tower after the desorption is completed, cooling the resin adsorption layer to a set temperature, and then entering a subsequent denitration unit together with the residual adsorption tail gas.
The desorption tail gas led out by the adsorption unit is condensed by a condensing device and is separated into two streams after being subjected to heat exchange by a purified tail gas heat exchanger, one stream is reused as defrosting gas of the cryogenic unit, and the other stream is sent into the synthesis reaction kettle to regulate the temperature of kettle liquid.
The denitration unit comprises a denitration heat exchanger, a tail gas heater, an ammonia adding device, a pipeline mixer and an SCR denitration reactor; the adsorption tail gas from the adsorption unit is subjected to heat exchange and temperature rise through a denitration heat exchanger and purified tail gas, then is added to be more than 170 ℃ through a tail gas heater, is subjected to ammonia addition through an ammonia adding device, finally is uniformly mixed through a mixer, then enters an SCR denitration reactor for denitration and purification, and the obtained purified tail gas is sent to the denitration heat exchanger for heat exchange with the adsorption tail gas.
The purified tail gas from the denitration heat exchanger is divided into two parts, one part of the purified tail gas is directly mixed with the adsorption tail gas after the temperature of the denitration heat exchanger is raised, the tail gas is participated in the tail gas circulation, the concentration of nitrogen oxides in the tail gas entering the SCR denitration reactor is diluted, and the other part of the purified tail gas is discharged outside through a chimney after the heat exchange, the temperature reduction and the dehumidification of the purified tail gas and the desorption tail gas.
The deep cooling unit consists of a plurality of deep cooling heat exchangers arranged on a kettle cover of the synthesis reaction kettle, the plurality of deep cooling heat exchangers alternately perform condensation and defrosting processes, and synthesis tail gas generated by the synthesis reaction kettle enters the deep cooling heat exchangers at the condensation stage from the bottom of the deep cooling heat exchangers to be condensed.
The cryogenic heat exchanger is provided with a plurality of reinforced cooling sections, and each reinforced cooling section adopts a refrigerant circulating pump to return downstream refrigerant to the upstream.
The plurality of cryogenic units correspond to one set of washing unit, adsorption unit and denitration unit.
The cryogenic tail gas from the cryogenic unit is divided into two parts, one part enters the washing unit, and the other part returns to the synthesis reaction kettle to adjust the kettle liquid temperature and stir the kettle liquid.
Aiming at the problems of complex pollution components, high pollutant concentration, high cost and great resource waste when purifying treatment is carried out on the synthetic tail gas. The invention breaks through the traditional treatment concept and provides a technical scheme for directly recycling the deep cooling condensation, the synthetic tail gas is cooled to below-50 ℃ by a low-temperature refrigerant at-70 ℃, nitrogen dioxide, organic fluoro compounds, hydrogen fluoride and the like are recovered, the synthetic tail gas returns to the production process to participate in the synthetic reaction again, the recycling utilization is realized, the synthetic tail gas is deeply cooled to below-50 ℃, the nitrogen dioxide is almost fully condensed, more than 70wt% of hydrogen fluoride is also condensed, and more than 90wt% of organic fluoro compounds are also condensed. The timely on-site recycling of the pollution components is realized through deep cooling, the utilization efficiency is high, and the utilization cost is low. The condensed pollutant components are from raw materials, reaction products or side reaction products required in the synthesis process of the organic fluoro compound, and the components are condensed and returned to the reaction system, so that the side reaction can be effectively inhibited, and the conversion rate of the reactants is improved. In addition, the invention creatively arranges the cryogenic unit at the top of the synthesis reaction kettle directly, and has the following advantages:
1) The synthetic tail gas generated by the reaction in the synthetic reaction kettle directly rises to pass through the kettle top and enter the deep cooling reactor, so that the energy consumption of the arrangement and the transportation of the pipeline is reduced;
2) After most of nitrogen dioxide in the deep cooling process of the synthesis tail gas is condensed, the nitrogen dioxide directly falls into the synthesis reaction kettle from the bottom of the deep cooling reactor, so that the concentration of nitrogen dioxide in kettle liquid is increased, the occurrence of side reaction < 2HNO 2- > NO+NO2+water > is inhibited, and the utilization rate of HNO2 is improved;
3) After dehydration, the deep cooling tail gas from the deep cooling unit contains HF, NO and a small amount of NO2 and fluorobenzene with higher concentration, and part of the dehydrated tail gas is separated out and returned to the synthesis reaction kettle, so that the dehydrated tail gas and the synthesis tail gas in the kettle can enter the deep cooling heat exchanger for condensation and recovery of HF, NO2 and fluorobenzene, and the purposes of stirring and humidity adjustment in the kettle can be achieved.
Because the fluorobenzene synthesis tail gas contains a large amount of fluorobenzene, nitrogen oxides, a small amount of VOCs and other pollution components besides HF components, in order to remove or recycle the pollution components and obtain an anhydrous HF product from a source, according to the physical properties and characteristics of the components, the invention creatively proposes a refrigerant internal circulation scheme of a cryogenic heat exchanger on the basis of cryogenic tail gas, and a reinforced cooling section is formed in the cryogenic heat exchanger. Different cooling effects are obtained by adjusting the circulation quantity, so that the condensation rates of different pollution components are realized, and the condensation interception effect of the pollution components of the synthetic tail gas is improved.
Of these contaminants, nitrogen dioxide has a melting point of-11 ℃ and a boiling point of 21 ℃; nitric oxide has a melting point of-163.6 ℃ and a boiling point of-151 ℃; fluorobenzene has a melting point of-42 ℃, a boiling point of 85 ℃, an HF melting point of 8-3 ℃ and a boiling point of 19.54 ℃. When the tail gas is deeply cooled to-50 ℃, nitrogen dioxide and fluorobenzene are basically fully condensed, and more than 70% of HF is also condensed. During the condensation process, nitrogen dioxide and fluorobenzene can appear in the cryogenic heat exchanger to form frost and block the tail gas circulation channel. In order to alleviate the problem of frosting and blockage, the invention is improved as follows:
(1) The tail gas enters a cryogenic heat exchanger to exchange heat with the refrigerant reversely, and the refrigerant is subjected to backflow forced circulation in the cryogenic heat exchanger to form reinforced cooling sections respectively corresponding to hydrogen fluoride, fluorobenzene and nitrogen dioxide. The refrigerant circulation pump is arranged to enable the refrigerant with the higher temperature at the downstream to flow back to the upstream, so that a condensation section with smaller temperature difference corresponding to the melting point temperature of the pollution component is formed, the pollution component is guaranteed to be fully condensed, and solidification and blockage are avoided.
(2) And the high-temperature desorption tail gas desorbed by the resin adsorption unit is used as a defrosting heat source by using the high-temperature gas in the tail gas purification system for circulating defrosting, so that fluorobenzene in the desorption tail gas is recovered, and the efficient defrosting is realized.
The effect of such improvement is as follows:
(1) And the pollution components are condensed and recovered step by step, the frosting and blockage in the cryogenic process are slowed down, and the running stability of the system is improved.
(2) The refrigerant is subjected to backflow forced circulation, the cold quantity of the refrigerant is fully utilized, the temperature of the refrigerant of the cryogenic heat exchanger is increased, heat exchange is performed with cryogenic tail gas with lower temperature (-50 ℃) after cryogenic, and the cold quantity utilization efficiency of the refrigerant is improved.
(3) And fully recovering frosting cold energy.
(4) And an external defrosting medium is not required to be introduced, so that efficient defrosting is achieved.
In order to efficiently recycle HF components in the tail gas, the scaling and blocking problems existing in the absorption process of sodium hydroxide solution are eliminated, and a primary water washing tower and a primary alkaline washing tower are periodically switched in a washing unit for alternate use. By setting the period of the alkaline washing stage of the alkaline washing tower, the functions of the alkaline washing tower and the 1-level water washing tower are periodically switched, namely the functions of alkaline washing and water washing are switched, and the improved effect is as follows:
(1) Thoroughly eliminating the scaling and blocking problems. Because the solubility of sodium fluoride in water is only 3.85 percent (10 ℃), the sodium fluoride is easy to adhere to the surfaces of the filler and the contact surfaces of the pump impeller, the inner wall of the absorption tower and the like, and forms a scale layer to block equipment. Through switching, original circulating alkali liquor is changed into circulating spray water, original low-concentration hydrogen fluoride tail gas is changed into high-concentration hydrogen fluoride tail gas, along with the circulating spray of the circulating spray water, the concentration of hydrogen fluoride is higher and higher, the pH value of absorption liquid is lower, and sodium fluoride scale layers which are originally adhered on the surfaces of packing and contact surfaces such as pump impellers, inner walls of absorption towers and the like are dissolved into hydrogen fluoride aqueous solution, so that online descaling is realized, and external descaling agents are not required to be introduced.
(2) Obtain HF product with high concentration and raise the recovery rate of fluorine element. Because the HF in the tail gas is lower and lower along with the 1-level to 4-level water washing in the process of washing and absorbing the HF in the tail gas, the water washing and absorbing efficiency is lower and lower. The ionization process of HF in dilute solution can be expressed as hf+h 2 O→H 3 O + +F - Due to F - Is a strong proton acceptor, and H 3 O + Is a strong proton donor, H 3 O + And F is equal to - Generating more stable ion pairs through hydrogen bond combination: the ion pair is difficult to ionize, HF shows weak acidity in a dilute solution, and the gas-liquid phase equilibrium concentration of HF exists in the absorption process, so that a certain amount of HF residues exist in the tail gas, HF components in the tail gas can be thoroughly absorbed through alkaline washing, and then the functions of absorption equipment are realizedThe conversion scheme further dissolves and recovers fluorine element in the scale layer.
Further, the deionized water amount supplemented to the water washing demisting tower is controlled according to the concentration of HF in the tail gas entering the washing unit, so that the washing liquid amount sequentially discharged from the water washing demisting tower to the multi-stage water washing tower is controlled, the concentration of the finally-entering washing liquid absorbing the HF in the tail gas of the first-stage water washing tower is ensured to reach more than 40%, and the liquid phase amount balance of the system is ensured.
When the amount of the deionized water supplied to the water washing demisting tower is excessive, the amount of liquid phase discharged by the washing unit is increased, the content of HF in the discharged liquid phase product is lower, and the adding amount of the deionized water is reduced; if the amount of the supplemented deionized water is too low, the dehydrofluorination effect of the previous water scrubber is affected, and the load of the alkaline scrubber for dehydrofluorination is increased.
Furthermore, when the function of the absorption equipment is converted, two circulating liquid tanks are arranged corresponding to the primary water washing tower and the alkaline washing tower, one circulating alkali liquid tank and the other circulating spraying water tank. When the circulating spray liquid is used as a 1-level water washing tower, the circulating spray liquid returns to the circulating spray water tank; when the circulating spray liquid is used as an alkaline washing tower, the circulating spray liquid returns to the circulating alkaline liquid tank. When water washing is carried out, the circulating alkali liquor in the alkali washing stage is continuously and evenly discharged into a circulating spray water tank which is in use, the discharge is stopped when the discharge amount reaches 50-60% of the total circulating alkali liquor amount by volume percent, and then fresh sodium hydroxide solution is supplemented into the circulating alkali liquor tank to the original liquid level. The improvement effect is as follows:
(1) The full recovery of the fluorine component of the system can be ensured, and the fluorine component is discharged outside.
(2) The fluorine-containing wastewater is not generated, the wastewater treatment investment and the operation cost are saved, and the treatment process of the fluorine component in the tail gas is greatly simplified.
Furthermore, the invention provides two improvements for innovatively recovering the resin adsorption unit in the limit of the p-fluorobenzene:
(1) And (5) cooling the adsorption tail gas in a circulating way. And (3) refluxing 10-20% by volume of the washing tail gas from the other resin adsorption tower into the cooled resin adsorption layer in the resin adsorption tower after the desorption is completed, and mixing the washing tail gas subjected to heat exchange and temperature rise of the resin layer with the residual 80-90% by volume of the adsorption tail gas to enter a subsequent denitration unit. The resin adsorption layer after desorption is cooled, so that the lower the temperature is, the more favorable the adsorption is for the adsorption, and the phenomenon that the washing tail gas is heated when entering in the early stage of adsorption due to the higher temperature of the resin adsorption layer is avoided, and the tail gas flow rate is high, the adsorption time is short and the p-fluorobenzene adsorption rate is reduced is considered; the adoption of partial adsorption tail gas reflux cooling considers that the resin is cooled at a lower cooling speed, so that the influence of rapid cooling on the service life of the resin is avoided.
(2) Condensing and dehydrating the desorption tail gas (the main components are fluorobenzene and nitrogen oxides) after resin desorption, then carrying out heat exchange with the purified tail gas after SCR denitration by a tail gas heat exchanger, heating, and then returning to a synthesis reaction kettle for stirring and temperature adjustment.
The effect of such improvement is as follows:
(1) Fully utilizes the cold source and the heat source of the medium in the system. The resin adsorption tower after the desorption is cooled by the reflux of the adsorption tail gas, so that the cold quantity of the adsorption tail gas with lower temperature is recovered; the heat exchange between the desorption tail gas and the purified tail gas after SCR denitration is carried out, so that the enthalpy of the purified tail gas with higher temperature is recovered; and the desorption tail gas after heat exchange and temperature rising enters a kettle for stirring, so that the enthalpy required by heating and pyrolysis of the synthetic reaction kettle liquid is saved.
(2) And the pollution components such as fluorobenzene, nitrogen oxides and the like contained in the desorption tail gas are fully recycled.
Furthermore, the invention creatively provides a technical scheme of purifying tail gas circulation when SCR denitration treatment is carried out on the adsorption tail gas after resin adsorption, namely the purification tail gas from a denitration heat exchanger is divided into two parts, one part is directly mixed with the adsorption tail gas after temperature rise to participate in the tail gas circulation, and the other part is discharged outside through a chimney after heat exchange, cooling and dehydration of the purification tail gas heat exchanger and the desorption tail gas. The technical scheme has the following effects:
(1) From the aspect of system operation stability, through the circulation of purified tail gas, the fluctuation range of the NOx content in the adsorption tail gas entering the SCR denitration reactor is reduced, the impact of the concentration fluctuation of NOx in the inlet gas on the catalyst is slowed down, and the stability of the SCR denitration reaction process is facilitated.
(2) Through the cyclic dilution effect of the purified tail gas, the fluctuation range of the temperature of the adsorbed tail gas entering the reactor can be reduced, and the running stability of the system is further improved. The improvement of the system operation stability can effectively reduce the system operation cost and prolong the service life of the catalyst.
(3) Through the on-line monitoring to NOx concentration in the purified tail gas, adjust the ammonia volume of spouting into in the absorption tail gas, the circulation of purified tail gas has also controlled the fluctuation of ammonia content in the tail gas that gets into SCR denitration reactor, is favorable to the stability of SCR denitration reaction process, improves the denitration effect, reduces ammonia escape simultaneously.
(4) And heat exchange is carried out on the purified tail gas of each row and the desorption tail gas with lower temperature, so that partial moisture in the purified tail gas is condensed, ammonia components in the flue gas are absorbed in the condensation process, and ammonia escape is reduced.
(5) Through the circulation of the purified tail gas, the concentration of nitrogen oxides is diluted, and the phenomenon that the catalyst is damaged due to severe local reaction in the reactor is avoided.
The invention can realize the full recovery of fluorobenzene and fluorine components of the synthetic tail gas, fully recover waste heat and residual cold, and has relatively simple process route, environmental friendliness and low equipment investment and operation cost.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Wherein: the synthesis reaction kettle HC1, the refrigerant circulating pump HC2, the cryogenic heat exchanger HC3, the kettle cover HC7 and the purified tail gas heat exchanger HC15;
a washing induced draft fan XD1, a primary alkaline washing tower XD2A, a primary water washing tower XD2B, a secondary water washing tower XD3, a tertiary water washing tower XD4, a quaternary water washing tower XD5, a water washing demisting tower XD6, a tower lower storage tank XD8, a water washing circulating pump XD11, an alkali discharging pump XD12, a circulating alkali lye tank XD20 and a circulating spray water tank XD21;
the device comprises a resin adsorption tower SX1, a reflux cooling fan SX3, a spray cooling tower SX4, an analysis tail gas condenser SX5, a gas-liquid separator SX7, an oil-water separation tank SX11 and a fluorobenzene product tank SX12;
denitration heat exchanger XT3, circulating fan XT4, tail gas circulation regulating valve XT5, tail gas heater XT8, pipeline mixer XT10, ammonia adding device XT11, SCR denitration reactor XT9,
Detailed Description
The process of the invention is further explained below with reference to the accompanying drawings:
taking fluorobenzene production for an enterprise as an example, a production line comprises 60 synthesis reaction kettles HC1, and fluorobenzene is produced 4000 tons per year.
And producing each synthesis reaction kettle HC1 in a gap. The main technological process of fluorobenzene synthesis comprises the reaction steps of salifying, diazotizing, pyrolyzing and the like, and all the reaction processes are completed in a synthesis reaction kettle HC 1.
(1) Salt formation
The low-temperature hydrofluoric acid liquid (-15 ℃) is metered and placed into a synthesis reaction kettle HC1, the synthesis reaction kettle HC1 is cooled by frozen brine continuously, the temperature of the synthesis reaction kettle HC1 is reduced to 4-6 ℃, aniline is slowly dripped into the synthesis reaction kettle HC1 under stirring, the temperature is kept between 5-8 ℃ during dripping, the reaction process is hydrofluoric acid excessive reaction, the pressure is slightly negative, the amount of the frozen brine is regulated after dripping is finished, the reaction is finished after the heat preservation is carried out at about 6 ℃ for 30 minutes, and the reaction time is 6 hours, so that the aniline hydrofluoric acid salt mixture is obtained.
(2) Diazotisation
And (3) reducing the temperature of circulating frozen brine of the synthesis reaction kettle HC1, reducing the temperature to 0-minus 2 ℃, slowly adding sodium nitrite solid under stirring, controlling the feeding temperature to 0-5 ℃, keeping the temperature for 30 minutes after the feeding is finished, and reacting for 10 hours to obtain the diazonium solution.
Side reactions exist during the diazotization reaction: 2HNO2→NO+NO2+ water.
(3) Pyrolysis of
The temperature of the frozen brine is regulated, the kettle liquid in the synthesis reaction kettle HC1 is slowly heated (5-15 ℃, 15-25 ℃ and 25-38 ℃) in stages under stirring, the temperature is raised to about 1.2 ℃ per hour until the temperature is raised to 38 ℃, the pressure is slightly negative, the thermal decomposition is carried out, and the pyrolysis time is 32h. After the reaction is finished, placing materials in the kettle into a standing tank for layering, wherein an organic layer is a fluorobenzene mixture; the inorganic layer contains hydrofluoric acid, sodium fluoride, etc.
In different reaction stages, the reaction temperature is different and needs to be adjusted according to the reaction period.
Referring to fig. 1, the structure of the fluorobenzene synthesis tail gas cryogenic unit and the cryogenic process are as follows:
1. the deep cooling part is composed of at least 3 shell-and-tube type deep cooling heat exchangers HC3 arranged on a kettle cover HC7 of the synthesis reaction kettle, a tube side air inlet of one end of each deep cooling heat exchanger HC3 is directly connected to the kettle cover HC7 and communicated with the synthesis reaction kettle HC, and a tube side air outlet of the other end of each deep cooling heat exchanger HC is connected to an inlet of an induced draft fan through a pipeline.
2. The cryogenic heat exchangers HC3 are used in parallel, at least one of them is defrosted in the normal operation process, and the rest of them are used in cryogenic operation. Under the suction action of a kettle pressure and a draught fan, the synthetic tail gas enters a tube pass of a cryogenic heat exchanger HC3, exchanges heat with a low-temperature refrigerant with the temperature of minus 70 ℃ introduced into a shell pass, and forms cryogenic tail gas with the temperature of minus 50 ℃ to enter a subsequent purification unit;
3. setting a limiting value of the temperature of a cryogenic tail gas outlet of the cryogenic heat exchanger HC3 at-50-55 ℃, setting a limiting value of the pressure difference between a tail gas inlet and a tail gas outlet, and regulating and controlling the working mode of the cryogenic heat exchanger HC3 by monitoring the temperature and the pressure difference in real time. When the temperature of the outlet cryogenic tail gas is lower than-55 ℃, stopping introducing low-temperature refrigerant at-70 ℃ into the cryogenic heat exchanger HC3, enabling the cryogenic heat exchanger HC3 to enter a defrosting mode, and automatically defrosting by generating synthetic tail gas with higher temperature in the kettle. In the defrosting stage, stopping introducing low-temperature refrigerant at-70 ℃ into the cryogenic heat exchanger HC 3;
4. the control of the 'deep cooling-defrosting' working mode of the deep cooling heat exchanger HC3 can also adopt a timing mode, namely the time ratio of deep cooling and defrosting in one period of setting the 'deep cooling-defrosting' of the deep cooling heat exchanger HC3, and the 'deep cooling' and the 'defrosting' of the deep cooling heat exchanger HC3 are staggered and used alternately;
5. the "defrost" of the cryogenic heat exchanger HC3 may also take the desorbed tail gas from the adsorption unit. And switching the desorption tail gas originally entering the synthesis reaction kettle HC1 to the outlet of the cryogenic heat exchanger HC3 needing defrosting, closing the outlet valve of the cryogenic heat exchanger HC3, defrosting by means of enthalpy of the desorption tail gas, and impacting the frost block by means of pressure of the desorption tail gas.
Although the amount and the composition of the tail gas discharged by each synthesis reaction kettle HC1 in different synthesis reaction stages are different, the quantity of the synthesis reaction kettles HC1 is large, and the flow and the composition of the discharged cryogenic tail gas are basically stable.
The amount of the synthesized tail gas discharged when the cryogenic condensation is not carried out is 1000-2000 Nm3/h, and the tail gas mainly comprises the following components: HF: 160-170 g/Nm3; fluorobenzene: 2000-3000 mg/Nm3; NOx: 12000-20000 mg/Nm3; a minor amount of VOCs component; the balance being nitrogen.
One set of washing unit, adsorption unit and denitration unit corresponds to a plurality of sets of synthesis reaction kettles HC1 and cryogenic units.
Referring to the attached figure 1, synthetic tail gas generated by the reaction in the synthesis reaction kettle HC1 rises to pass through a kettle cover HC7 at the top of the synthesis reaction kettle HC1 and directly enters a cryogenic heat exchanger HC3 of a cryogenic unit to be indirectly cooled to between-50 ℃ and-55 ℃ by a low-temperature refrigerant at-70 ℃, the cryogenic tail gas formed by deep cooling and condensing more than 99.99% of fluorobenzene, nitrogen dioxide and more than 70% of hydrogen fluoride is divided into two strands, and one strand enters a washing unit to further recover residual hydrogen fluoride components in the cryogenic tail gas and then sequentially enters a washing unit to be subjected to dehydrofluorination, an adsorption unit to be subjected to dehydrofluorination, a denitration unit to be subjected to denitration and purification and then discharged; the other strand is sent into a synthesis reaction kettle HC1 to adjust the temperature in the kettle, stir the kettle liquid and recycle the hydrogen fluoride component.
The condensation-defrosting process of the cryogenic heat exchanger HC3 can also be controlled by setting upper and lower limiting values of the tail gas pressure at the outlet of the cryogenic heat exchanger HC 3; when the tail gas pressure at the outlet of the cryogenic heat exchanger HC3 is lower than a lower limit value, cutting off the refrigerant, and enabling the cryogenic heat exchanger to enter a defrosting stage; when the exhaust gas pressure at the outlet of the cryogenic heat exchanger HC3 is higher than the upper limit value, refrigerant is introduced, and the cryogenic heat exchanger HC3 enters a cryogenic working stage, and the above steps are alternately performed.
The cryogenic heat exchanger HC3 is provided with three reinforced cooling sections, and each reinforced cooling section adopts a refrigerant circulating pump HC2 to return downstream refrigerant to the upstream. The synthesized tail gas is reversely contacted with condensation, condensed hydrogen fluoride, organic fluoro-compound and nitrogen dioxide component are respectively intensified in three-stage intensified cooling sections, the condensation interception effect of the polluted component of the synthesized tail gas is improved, and nitrogen dioxide is contained in the generated cryogenic heat exchanger HC3The condensate liquid of (2) directly falls through the kettle cover HC7 to enter the synthesis reaction kettle HC1, and directly falls into the synthesis reaction kettle HC1 from the bottom of the deep cooling reactor HC3, thereby increasing the nitrogen dioxide concentration in the kettle liquid and inhibiting the side reaction (2 HNO) 2 →NO+NO 2 The occurrence of +Water improves HNO 2 Is used for the utilization of the system.
With continued reference to fig. 1, in this embodiment, the washing unit includes four-stage water washing towers XD2B, XD, XD4, XD5, first-stage alkaline washing tower XD2A and water washing demister XD6 connected in series, the most organic fluoro compounds are recovered by condensation, the cryogenic tail gas after hydrogen fluoride is washed by a washing induced draft fan XD1, and then enters the adsorption unit to remove the organic fluoro compounds after removing 99.99% of hydrogen fluoride by four-stage water washing towers XD2B, XD, XD4, XD5 water washing, first-stage alkaline washing tower XD2A alkaline washing and water washing demister XD 6.
Here, the first-stage water scrubber XD2B and the first-stage alkaline scrubber XD2A in the multistage water scrubber can be alternately switched to operate by controlling the pipeline and the valve, i.e., the first-stage water scrubber XD2B can be switched to the first-stage alkaline scrubber, and the first-stage alkaline scrubber XD2A can be switched to the water scrubber. The bottoms of the first-stage water washing tower XD2B and the first-stage alkaline washing tower XD2A are respectively provided with two circulating liquid tanks, one circulating liquid tank XD20 and the other circulating spray water tank XD21, when the first-stage water washing tower works, circulating spray liquid is collected by the corresponding circulating spray water tank XD21 and then returned into the tower, when the first-stage alkaline washing tower works, circulating spray liquid is collected by the circulating liquid tank XD21 and then returned into the tower, and the control can be completed through corresponding pipeline connection and valve switching, so that the prior art is not described in detail.
The specific preferred method is as follows: monitoring the concentration of sodium fluoride in a circulating alkali liquid tank of a tower serving as a first-stage alkaline washing tower XD2A, when the concentration exceeds 3%wt, directly switching and introducing the cryogenic tail gas entering the original first-stage alkaline washing tower into the tower, simultaneously switching the circulating liquid tank of the tower, introducing circulating spray water in a circulating spray water tank XD21 into the tower for circulating spray, and switching the tower to serve as the first-stage water washing tower;
and simultaneously, switching the original primary water washing tower into a primary alkaline washing tower, introducing tail gas from the final primary water washing tower into the tower, simultaneously switching a circulating liquid tank of the tower, and introducing circulating alkali liquor spray in the circulating alkali liquor tank XD20 into the tower for circulating spray. Because the solubility of sodium fluoride in water is only 3.85 percent (10 ℃), the sodium fluoride is easy to adhere to the surfaces of the filler and the contact surfaces of the pump impeller, the inner wall of the absorption tower and the like, and forms a scale layer to block equipment. Through switching, original circulating alkali liquor is changed into circulating spray water, original low-concentration hydrogen fluoride tail gas is changed into high-concentration hydrogen fluoride tail gas, along with circulating spray of the circulating spray water, the concentration of hydrogen fluoride is higher and higher, and sodium fluoride scale layers which are adhered on the surfaces of a filler, a pump impeller, the inner wall of an absorption tower and other contact surfaces are dissolved into a hydrogen fluoride aqueous solution, so that online descaling is realized, no external descaling agent is required to be introduced, and meanwhile, the full recovery and zero discharge of fluorine components of a system are ensured.
When the circulating alkali liquor is used as a primary water washing tower, circulating alkali liquor is continuously and evenly discharged from a corresponding circulating alkali liquor tank XD20, enters a corresponding circulating spray water tank XD21 through an alkali discharge pump XD1, and is stopped when the discharge amount reaches 50-60% by volume of the total circulating alkali liquor, and then fresh sodium hydroxide solution is supplemented into the circulating alkali liquor tank XD21 to the original liquid level. And uniformly and continuously supplementing deionized water to the water washing demisting tower XD6, and enabling part of washing water discharged from the bottom of the tower to reversely enter the multistage water washing tower in sequence to be used as circulating spraying water.
The external washing liquid phase inlet pipe of the washing unit is respectively connected with a circulating alkali liquid tank XD20 of the primary alkaline washing tower and a tower lower storage tank of a water washing demisting tower XD6, the circulating spray water tank XD21 of the primary alkaline washing tower XD2B and the primary alkaline washing tower XD2A are provided with an external liquid discharge phase outlet pipe, and the external liquid discharge phase inlet pipe is used as the primary water washing tower XD2B for leading out hydrofluoric acid products with HF concentration of more than 40 wt%.
Referring to fig. 1, the adsorption unit includes at least two resin adsorption towers SX1, one adsorption tower and one desorption tower, which are alternately performed; and desorbing the resin adsorption tower by using superheated steam, introducing 10-20wt% of adsorption tail gas from another resin adsorption tower into the desorbed resin adsorption tower, cooling the resin adsorption layer to a set temperature, and then entering a subsequent denitration unit together with the rest of adsorption tail gas. The desorption tail gas led out by the adsorption unit is cooled to minus 5 ℃ to 0 ℃ through a condensing device, and is dehydrated, and then is indirectly exchanged with purified tail gas through a purified tail gas heat exchanger HC15 and is divided into two parts, one part is used as defrosting gas of the cryogenic unit to be returned to a defrosting gas pipeline of the cryogenic unit, and the other part is returned to the bottom of the synthesis reaction kettle HC1 to regulate the temperature in the kettle.
The condensing device comprises a gas-liquid separator SX7, a spray cooling tower SX7 and a resolved tail gas condenser SX5 which are sequentially connected, and desorption tail gas is condensed by the gas-liquid separator SX7, the spray cooling tower SX7 and the resolved tail gas condenser SX5 in sequence and then is sent to a purified tail gas heat exchanger SX13; and liquid phases (or condensate) led out by the gas-liquid separator SX7, the spray cooling tower SX7 and the analysis tail gas condenser SX5 enter an oil-water separation tank SX11 to be separated and recovered, and fluorobenzene is sent into a fluorobenzene product tank SX12 to obtain fluorobenzene products.
Referring to fig. 1, the denitration unit includes a denitration heat exchanger XT3, a tail gas heater XT8 ammonia device XT11, a pipe mixer XT10, an ammonia adding device XT11, and an SCR denitration reactor XT9; the adsorption tail gas from the adsorption unit is subjected to heat exchange with purified tail gas through a denitration heat exchanger XT3 and then is added to more than 170 ℃ through a tail gas heater XT8, ammonia is added through an ammonia adding device XT11 and then enters an SCR denitration reactor XT9 for denitration purification, the obtained purified tail gas is divided into two parts, one part of the purified tail gas is directly mixed with the adsorption tail gas heated by the denitration heat exchanger XT3 through a circulating ring fan XT4 and a tail gas circulating regulating valve XT4 valve and then is sent into the tail gas heater XT8 to participate in tail gas circulation, the concentration of nitrogen oxides in the tail gas entering the SCR denitration reactor is diluted, and the other part of the purified tail gas is subjected to heat exchange, cooling and dehumidification through the circulating ring fan XT4, the purified tail gas heat exchanger HC15 and the desorption tail gas and then is discharged through a chimney.
After purification treatment, the recovery rate of HF is more than 99.99%; the recovery rate of the organic fluoro compound is more than 99.9%; the NOx removal rate is more than 99.95 percent, and the outlet NOx is lower than 100mg/Nm 3 。
After the purification treatment, about 2000 tons of HF and about 20 tons of organic fluoro compounds are recovered annually.
Claims (14)
1. A recycling recovery process of fluorine components in fluorobenzene production tail gas comprises synthesis tail gas generated in a fluorobenzene synthesis process, and is characterized in that the synthesis tail gas is subjected to deep cooling condensation by a deep cooling unit to form hydrogen fluoride with more than 70 weight percent, and then the hydrogen fluoride is formed into deep cooling tail gas which enters a washing unit to deeply recover HF components in the deep cooling tail gas to generate hydrofluoric acid products with more than 45 weight percent of F components;
in the washing unit, the deep cooling tail gas is sequentially subjected to water washing by a multi-stage water washing tower and alkaline washing by a first-stage alkaline washing tower to further absorb residual hydrogen fluoride components in the deep cooling tail gas, the alkaline washing period of the first-stage alkaline washing tower is set, or the concentration limit value of sodium fluoride in alkaline liquor sprayed in the first-stage alkaline washing tower is set, and a 1 st-stage water washing tower and the first-stage alkaline washing tower in the multi-stage water washing tower are periodically switched and alternately used.
2. The recycling recovery process of fluorine components in fluorobenzene production tail gas according to claim 1, wherein the washing unit comprises at least 4-stage water washing towers, a first-stage alkaline washing tower and a water washing demisting tower which are connected in series, and the condensed cryogenic tail gas is subjected to water washing in the 4-stage water washing towers, alkaline washing in the first-stage alkaline washing towers and demisting in the water washing demisting towers in sequence.
3. The recycling process for fluorine components in fluorobenzene production tail gas according to claim 2, wherein two circulating liquid tanks are correspondingly arranged at the bottoms of a 1 st stage water washing tower and a first stage alkaline washing tower in the 4-stage water washing tower, one circulating liquid tank is a circulating spray water tank, when the 1 st stage water washing tower of the 4-stage water washing tower works, circulating spray liquid is collected by the circulating spray water tank and then returned to the tower, and when the first stage alkaline washing tower works, circulating spray liquid is collected by the circulating alkaline liquid tank and then returned to the tower; and the bottom of the circulating alkali liquid tank is led out to obtain hydrofluoric acid products with more than 45 weight percent of F-containing components.
4. The process for recycling fluorine components in fluorobenzene production tail gas according to claim 3, wherein the concentration of sodium fluoride in a circulating alkali liquid tank of a tower used as a primary alkali washing tower is monitored, when the concentration exceeds 3wt%, the deep cooling tail gas entering a washing unit is directly switched and introduced into the tower, meanwhile, a circulating liquid tank of the tower is switched, circulating spray water in a circulating spray water tank is sprayed and introduced into the tower for circulating spray, namely, the alkali washing function of the tower is switched to the 1 st stage water washing function;
meanwhile, the original 1 st-stage water washing tower is switched into a first-stage alkaline washing tower, tail gas from the 4 th-stage water washing tower in the 4-stage water washing tower is introduced into the tower, meanwhile, a circulating liquid tank of the tower is switched, and circulating alkali liquor in the circulating alkali liquid tank is introduced into the tower for circulating spraying.
5. The process for recycling fluorine components in fluorobenzene production tail gas according to claim 4, wherein when the process is used as a level 1 water washing tower, circulating alkali liquor is continuously and uniformly discharged from a corresponding circulating alkali liquor tank to enter a corresponding circulating spray water tank, and when the discharge amount reaches 50-60% by volume of the total circulating alkali liquor amount, discharging is stopped, and fresh sodium hydroxide solution is replenished into the circulating alkali liquor tank to the original liquid level.
6. The recycling process for fluorine components in fluorobenzene production tail gas according to claim 2, wherein deionized water is uniformly and continuously supplemented to the water washing demister, and part of washing water discharged from the bottom of the tower reversely and sequentially enters the multistage water washing tower.
7. The recycling recovery process of fluorine components in fluorobenzene production tail gas according to any one of claims 1 to 6, wherein the washing tail gas after HF removal from the washing unit sequentially enters an adsorption unit for deblurring benzene and a denitration unit for denitration and purification and is discharged;
wherein the adsorption unit comprises at least 2 resin adsorption towers, one adsorption tower and one desorption tower are alternately performed; and (3) introducing 10-20% by volume of adsorption tail gas from the other resin adsorption tower into the resin adsorption tower after the desorption is completed, cooling the resin adsorption layer to a set temperature, and then entering a subsequent denitration unit together with the residual adsorption tail gas.
8. The recycling process for fluorine components in fluorobenzene production tail gas according to claim 7, wherein the desorption tail gas led out of the adsorption unit is condensed by a condensing device and is separated into two streams after heat exchange by a purified tail gas heat exchanger, one stream is reused as defrosting gas of a deep cooling unit, and the other stream is sent into a synthesis reaction kettle to regulate the temperature of kettle liquid.
9. The recycling process for fluorine components in fluorobenzene production tail gas according to claim 1, wherein the denitration unit comprises a denitration heat exchanger, a tail gas heater, an ammonia adding device, a pipeline mixer and an SCR denitration reactor; the adsorption tail gas from the adsorption unit is subjected to heat exchange and temperature rise through a denitration heat exchanger and purified tail gas, then is added to be more than 170 ℃ through a tail gas heater, is subjected to ammonia addition through an ammonia adding device, finally is uniformly mixed through a mixer, then enters an SCR denitration reactor for denitration and purification, and the obtained purified tail gas is sent to the denitration heat exchanger for heat exchange with the adsorption tail gas.
10. The recycling process of fluorine components in fluorobenzene production tail gas according to claim 9, wherein the purified tail gas from the denitration heat exchanger is divided into two parts, one part is directly mixed with the adsorption tail gas heated by the denitration heat exchanger to participate in tail gas circulation, the concentration of nitrogen oxides in the tail gas entering the SCR denitration reactor is diluted, and the other part is discharged outside through a chimney after heat exchange, cooling and dehumidification of the purified tail gas heat exchanger and the desorption tail gas.
11. The recycling process for fluorine components in fluorobenzene production tail gas according to claim 1, wherein the deep cooling unit comprises a plurality of deep cooling heat exchangers arranged on a kettle cover of a synthesis reaction kettle, the plurality of deep cooling heat exchangers alternately perform condensation and defrosting processes, and the synthesis tail gas generated by the synthesis reaction kettle enters the deep cooling heat exchanger in a condensation stage from the bottom of the deep cooling heat exchanger to be condensed.
12. The process for recycling fluorine components in tail gas from fluorobenzene production as claimed in claim 11, wherein the cryogenic heat exchanger is provided with a plurality of reinforced cooling sections, and each reinforced cooling section adopts a refrigerant circulating pump to return downstream refrigerant to the upstream.
13. The recycling process for fluorine components in fluorobenzene production tail gas as claimed in claim 7, wherein the plurality of cryogenic units correspond to one washing unit, adsorption unit and denitration unit.
14. The recycling process for fluorine components in fluorobenzene production tail gas according to claim 1, wherein the deep cooling tail gas from the deep cooling unit is divided into two parts, one part enters the washing unit, and the other part returns to the synthesis reaction kettle to adjust the kettle temperature and stir the kettle.
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