CN117599612A - Recovery method of discharged liquid of PTA tail gas washing tower - Google Patents
Recovery method of discharged liquid of PTA tail gas washing tower Download PDFInfo
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- CN117599612A CN117599612A CN202311311851.3A CN202311311851A CN117599612A CN 117599612 A CN117599612 A CN 117599612A CN 202311311851 A CN202311311851 A CN 202311311851A CN 117599612 A CN117599612 A CN 117599612A
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- sodium
- solution
- pta
- hydrobromic acid
- tail gas
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- 238000005406 washing Methods 0.000 title claims abstract description 36
- 238000011084 recovery Methods 0.000 title claims abstract description 34
- 238000000034 method Methods 0.000 title claims abstract description 31
- 239000007788 liquid Substances 0.000 title claims description 33
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims abstract description 94
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 88
- JHJLBTNAGRQEKS-UHFFFAOYSA-M sodium bromide Chemical compound [Na+].[Br-] JHJLBTNAGRQEKS-UHFFFAOYSA-M 0.000 claims abstract description 78
- 239000000243 solution Substances 0.000 claims abstract description 62
- 239000007789 gas Substances 0.000 claims abstract description 57
- BMYNFMYTOJXKLE-UHFFFAOYSA-N 3-azaniumyl-2-hydroxypropanoate Chemical compound NCC(O)C(O)=O BMYNFMYTOJXKLE-UHFFFAOYSA-N 0.000 claims abstract description 55
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims abstract description 47
- 235000019253 formic acid Nutrition 0.000 claims abstract description 47
- 239000004280 Sodium formate Substances 0.000 claims abstract description 44
- 239000012528 membrane Substances 0.000 claims abstract description 44
- HLBBKKJFGFRGMU-UHFFFAOYSA-M sodium formate Chemical compound [Na+].[O-]C=O HLBBKKJFGFRGMU-UHFFFAOYSA-M 0.000 claims abstract description 44
- 235000019254 sodium formate Nutrition 0.000 claims abstract description 44
- 238000000909 electrodialysis Methods 0.000 claims abstract description 40
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 38
- -1 formate ions Chemical class 0.000 claims abstract description 20
- 239000011259 mixed solution Substances 0.000 claims abstract description 15
- 230000008569 process Effects 0.000 claims abstract description 14
- 229910001415 sodium ion Inorganic materials 0.000 claims abstract description 11
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 claims abstract description 8
- 239000007864 aqueous solution Substances 0.000 claims abstract description 8
- 230000002378 acidificating effect Effects 0.000 claims abstract description 7
- 239000001257 hydrogen Substances 0.000 claims abstract description 6
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 6
- 239000000463 material Substances 0.000 claims abstract description 4
- 239000005416 organic matter Substances 0.000 claims abstract description 3
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 claims description 40
- 238000001223 reverse osmosis Methods 0.000 claims description 32
- 238000001704 evaporation Methods 0.000 claims description 11
- 230000008020 evaporation Effects 0.000 claims description 11
- 239000012141 concentrate Substances 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 238000010521 absorption reaction Methods 0.000 description 14
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 14
- 229910052794 bromium Inorganic materials 0.000 description 14
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 13
- 239000000047 product Substances 0.000 description 11
- 238000004064 recycling Methods 0.000 description 11
- 238000010586 diagram Methods 0.000 description 9
- 238000000926 separation method Methods 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- BDAGIHXWWSANSR-UHFFFAOYSA-M Formate Chemical compound [O-]C=O BDAGIHXWWSANSR-UHFFFAOYSA-M 0.000 description 4
- URLKBWYHVLBVBO-UHFFFAOYSA-N Para-Xylene Chemical group CC1=CC=C(C)C=C1 URLKBWYHVLBVBO-UHFFFAOYSA-N 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 239000010865 sewage Substances 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 3
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 239000012266 salt solution Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 150000001450 anions Chemical class 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229940006460 bromide ion Drugs 0.000 description 2
- GZUXJHMPEANEGY-UHFFFAOYSA-N bromomethane Chemical compound BrC GZUXJHMPEANEGY-UHFFFAOYSA-N 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 241001148470 aerobic bacillus Species 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- UBAZGMLMVVQSCD-UHFFFAOYSA-N carbon dioxide;molecular oxygen Chemical compound O=O.O=C=O UBAZGMLMVVQSCD-UHFFFAOYSA-N 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 229940102396 methyl bromide Drugs 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000005201 scrubbing Methods 0.000 description 1
- XUXNAKZDHHEHPC-UHFFFAOYSA-M sodium bromate Chemical compound [Na+].[O-]Br(=O)=O XUXNAKZDHHEHPC-UHFFFAOYSA-M 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 230000001954 sterilising effect Effects 0.000 description 1
- 241001148471 unidentified anaerobic bacterium Species 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 239000008096 xylene Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
- B01D61/44—Ion-selective electrodialysis
- B01D61/445—Ion-selective electrodialysis with bipolar membranes; Water splitting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
- B01D61/422—Electrodialysis
- B01D61/423—Electrodialysis comprising multiple electrodialysis steps
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/58—Multistep processes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2311/00—Details relating to membrane separation process operations and control
- B01D2311/26—Further operations combined with membrane separation processes
- B01D2311/2673—Evaporation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/025—Reverse osmosis; Hyperfiltration
- B01D61/026—Reverse osmosis; Hyperfiltration comprising multiple reverse osmosis steps
-
- 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
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Landscapes
- Engineering & Computer Science (AREA)
- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Urology & Nephrology (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
- Treating Waste Gases (AREA)
- Water Treatment By Electricity Or Magnetism (AREA)
Abstract
The invention provides a recovery method of PTA tail gas washing tower effluent, which is obtained by washing PTA tail gas subjected to organic matter removal treatment by sodium formate and sodium hydroxide solution, and mainly contains sodium formate and sodium bromide according to the material content, and comprises the following steps of: concentrating the effluent of the washing tower containing sodium bromide and sodium formate by adopting a concentration process to obtain concentrated solution and recovery solution of sodium bromide and sodium formate; step 2: adding a certain amount of desalted water into the sodium bromide and sodium formate concentrated solution obtained in the step 1 to enter a bipolar membrane electrodialysis system for treatment to obtain hydrobromic acid and formic acid mixed solution formed by bromide ions, formate ions and hydrogen ions ionized by a bipolar membrane, and sodium hydroxide solution formed by sodium ions and hydroxide ions ionized by the bipolar membrane; step 3: and (3) adding the hydrobromic acid and formic acid mixed solution obtained in the step (2) and desalted water into an electrodialysis system, controlling the pH value to be acidic, and separating to obtain a purified hydrobromic acid aqueous solution and a formic acid solution containing a small amount of hydrobromic acid.
Description
Technical Field
The invention relates to the field of process recovery, in particular to a recovery method of discharged liquid of a PTA tail gas washing tower.
Background
In the PTA production process, paraxylene (PX) reacts with oxygen in the air under the action of catalysts such as bromide ions and the like to generate Crude Terephthalic Acid (CTA), and a large amount of tail gas is generated. The main components of the tail gas are nitrogen, carbon dioxide, carbon monoxide, residual oxygen, acetic acid, organic solvents (benzene, toluene, xylene, methyl acetate and methyl bromide) and trace bromine gas. And then the residual organic components are burnt after the organic matters are recovered by high-pressure washing and high-temperature catalysis. The final components are nitrogen, oxygen, carbon dioxide, carbon monoxide, bromine gas and water vapor.
Because bromine gas has serious influence on the environment and human health, a normal pressure washing tower is required to be used for spraying sodium formate and sodium hydroxide solution, PTA tail gas which is removed by organic matters is treated, bromine molecules are reduced into bromine ions, sodium bromide is generated by the bromine molecules and sodium ions in water, and the bromine molecules and the sodium bromide are discharged to a sewage treatment plant. In order to reduce the bromine emission concentration and reach the environmental emission standard, in practical operation, the excessive amount of sodium formate and sodium hydroxide is required to be maintained, so that the concentration of formate ions in the waste liquid is maintained at 1500ppm, and the PH=8.8 of the waste liquid is maintained.
However, the sterilizing function of sodium bromide itself has considerable harm to anaerobic bacteria and aerobic bacteria in sewage biochemical treatment, which can affect the whole sewage treatment system, and the adoption of the process route for treating PTA tail gas requires a large amount of pure water, sodium formate and sodium hydroxide raw materials, so that the treatment cost is huge, the treated discharge liquid is directly discharged to the sewage system, the waste of tail gas treatment absorption liquid and bromine element is caused, and meanwhile, the environment is also influenced to a certain extent. Therefore, it is necessary to further recycle sodium bromide and sodium formate in the effluent of the scrubber after the PTA tail gas treatment with sodium formate and sodium hydroxide solution.
In the prior art, bromine elements generated in the PTA production process are mostly recovered by adopting electrodialysis and other similar equipment to treat and recover salt solution generated after tail gas treatment, and finally, the salt solution is recovered in the form of hydrobromic acid or sodium bromide. However, when the effluent from the tail gas treatment with an acidic or salt solution is recovered, the resulting hydrobromic acid solution is also in the past rich in other acidic materials. For example, when sodium formate and sodium hydroxide are used as the absorption liquid for tail gas treatment, the hydrobromic acid solution obtained after treatment by the electrodialysis device also contains a large amount of formic acid, which affects further recycling of hydrobromic acid and formic acid.
Disclosure of Invention
The main technical problem to be solved by the invention is to provide a recovery method of the discharged liquid of the PTA tail gas washing tower, which can recover bromine element, sodium ion and formate ion from the discharged liquid of the washing tower and separate the recovered substances.
In order to solve the technical problems, the invention provides a recovery method of PTA tail gas washing tower effluent, wherein the washing tower effluent is obtained by washing PTA tail gas subjected to organic matter removal treatment by using sodium formate and sodium hydroxide solution, and mainly contains sodium formate and sodium bromide according to the material content, and the recovery method comprises the following steps:
step 1: concentrating the effluent of the washing tower containing sodium bromide and sodium formate by adopting a concentration process to obtain concentrated solution and recovery solution of sodium bromide and sodium formate;
step 2: adding a certain amount of desalted water into the sodium bromide and sodium formate concentrated solution obtained in the step 1 to enter a bipolar membrane electrodialysis system for treatment to obtain hydrobromic acid and formic acid mixed solution formed by bromide ions, formate ions and hydrogen ions ionized by a bipolar membrane, and sodium hydroxide solution formed by sodium ions and hydroxide ions ionized by the bipolar membrane;
step 3: and (3) adding the hydrobromic acid and formic acid mixed solution obtained in the step (2) and desalted water into an electrodialysis system, controlling the pH value to be acidic, and separating to obtain a purified hydrobromic acid aqueous solution and a formic acid solution containing a small amount of hydrobromic acid.
In one embodiment, the concentrate of step 1 has an equivalent concentration of 1 to 2N.
In one embodiment, the concentration process in step 1 adopts an RO reverse osmosis membrane device, and the recovery liquid is RO reverse osmosis desalted water.
In one embodiment, the concentration process in step 1 uses a multi-effect evaporation device, and the recovery liquid is a multi-effect evaporation condensate.
In one embodiment, the RO reverse osmosis membrane device comprises a two-stage RO reverse osmosis membrane.
In one embodiment, the pH is in the range of 3.7 or less.
In one embodiment, the recovery liquid of step 1 is returned to the scrubber.
In one embodiment, the sodium hydroxide solution described in step 2 is returned to the scrubber.
In one embodiment, the aqueous solution of purified hydrobromic acid in step 3 is adjusted to a concentration to enter a terephthalic acid production process, and the formic acid solution in step 3 is returned to the scrubber.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1. the invention provides a recovery method of PTA tail gas washing tower effluent, which can recover bromine element, sodium ion and formate ion from PTA tail gas washing effluent containing sodium formate and sodium bromate, purify and separate recovered substances, realize recovery of waste water without discharge, and is beneficial to environmental development.
2. The invention provides a recovery method of discharged liquid of a PTA tail gas washing tower, which is used for recycling the recovered tail gas treatment absorption liquid substances (formic acid and sodium hydroxide) and bromine elements, thereby improving the economic benefit of the process.
Drawings
FIG. 1 is a flow chart of a PTA tail gas scrubbing effluent recovery process;
FIG. 2 is a schematic diagram of RO reverse osmosis concentration process;
FIG. 3 is a schematic diagram of a bipolar membrane electrodialysis flow scheme;
FIG. 4 is a schematic diagram of an electrodialysis scheme;
FIG. 5 is a schematic diagram of bipolar membrane electrodialysis system operation;
FIG. 6 is a schematic diagram of the RO reverse osmosis concentration scheme of example 2;
FIG. 7 is a schematic diagram of a bipolar membrane electrodialysis scheme of example 2;
FIG. 8 is a schematic of the electrodialysis scheme of example 2;
FIG. 9 is a schematic diagram of the RO reverse osmosis concentration scheme of example 3;
FIG. 10 is a schematic diagram of a bipolar membrane electrodialysis scheme of example 3;
FIG. 11 is a schematic of the electrodialysis scheme of example 3;
fig. 12 is a schematic diagram of a multi-effect evaporation concentration process in example 4.
Reference numerals: 1. an electrode; 2. cation permeable membranes; 3. an anion permeable membrane; 4. hydrogen ions; 5. hydroxide ions; 6. sodium ions; 7. a bromide ion; 8. formate ion; 9. concentrating the liquid; 10. a sodium hydroxide solution; 11. hydrobromic acid and formic acid mixed solution;
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments, and that all other embodiments obtained by persons of ordinary skill in the art without making creative efforts based on the embodiments in the present invention are within the protection scope of the present invention.
Example 1
Referring to fig. 1 to 5, this embodiment provides a method for recovering a PTA off-gas scrubber effluent, which is obtained by washing PTA off-gas subjected to organic removal treatment with sodium formate and sodium hydroxide solution, and contains sodium formate and sodium bromide, the method comprising the steps of:
step 1: concentrating the effluent of the washing tower containing sodium bromide and sodium formate by adopting a concentration process to obtain concentrated solution and recovery solution of sodium bromide and sodium formate;
step 2: adding a certain amount of desalted water into the sodium bromide and sodium formate concentrated solution obtained in the step 1 to enter a bipolar membrane electrodialysis system for treatment to obtain hydrobromic acid and formic acid mixed solution formed by bromide ions, formate ions and hydrogen ions ionized by a bipolar membrane, and sodium hydroxide solution formed by sodium ions and hydroxide ions ionized by the bipolar membrane;
step 3: and (3) adding the hydrobromic acid and formic acid mixed solution obtained in the step (2) and desalted water into an electrodialysis system, controlling the pH value to be acidic, and separating to obtain a purified hydrobromic acid aqueous solution and a formic acid solution containing a small amount of hydrobromic acid.
Specifically, the effluent (sodium bromide, sodium formate and water) from the washing tower enters an RO reverse osmosis device, is subjected to primary RO reverse osmosis concentration, is concentrated and separated to obtain concentrated solution 1 and RO reverse osmosis desalted water 1, and is subjected to secondary RO reverse osmosis concentration to obtain concentrated solution 2 and the RO reverse osmosis desalted water 2 of the other part. Thus, the concentrated solution after the two-stage RO reverse osmosis concentration can meet the better working condition of the bipolar membrane electrodialysis of the next step, and the efficiency and effect of the bipolar membrane electrodialysis of the next step are improved.
The concentrated solution 2 after two-stage concentration is added with a certain amount of desalted water to enter a bipolar membrane electrodialysis (BPED) system, wherein bromide ions 7 and formate ions 8 pass through an anion permeable membrane 3 to be combined with hydrogen ions 4 ionized by the bipolar membrane, a main product hydrobromic acid and formic acid mixed solution 11 is extracted, sodium ions 6 pass through a cation permeable membrane 2 to be combined with hydroxide ions 5 ionized by the bipolar membrane, and a byproduct sodium hydroxide solution 10 is extracted. The recovery of bromide ion 7, formate ion 8 and sodium ion 6 in the discharged liquid is realized through bipolar membrane electrodialysis, sodium bromide with side effects on the environment is successfully converted into hydrobromic acid and sodium hydroxide with utilization value, and the recovery of formic acid is also realized.
Since the mixed solution 11 of formic acid and hydrobromic acid is obtained by bipolar membrane electrodialysis, further separation is required to recycle the formic acid and hydrobromic acid. The hydrobromic acid and formic acid mixed solution 11 produced by bipolar membrane electrodialysis is added with a certain amount of desalted water to enter an electrodialysis system (ED), the PH range is adjusted to be acidic, and the hydrobromic acid and the formic acid are separated. The PH range is within a certain acid range, so that the separation of hydrobromic acid and formic acid can be realized.
Through the steps, not only bromine element in the discharged liquid is recovered in the form of hydrobromic acid, but also sodium ions and formate ions in the discharged liquid are recovered as tail gas treatment absorption liquid (formic acid and sodium hydroxide) for further recycling.
In this example, in order to make the concentrate subjected to the concentration step meet the optimal conditions for bipolar membrane electrodialysis, the effluent concentration in step 1 is concentrated to 1-2 equivalent concentration, within which the bipolar membrane electrodialysis system has optimal efficiency.
In this embodiment, in order to better separate hydrobromic acid from formic acid, a purified hydrobromic acid solution is obtained, the PH range in step 3 is controlled to be 3.7 or less, and when the PH range is kept to be 3.7 or less, formic acid can be preferably kept from dissociating, so that hydrobromic acid and formic acid can be better separated, and a purified hydrobromic acid aqueous solution is obtained.
In the embodiment, RO reverse osmosis desalted water 1 subjected to primary concentration and RO reverse osmosis desalted water 2 obtained after two-stage concentration are sent back to the top of the tail gas washing tower, and the RO reverse osmosis desalted water can replace pure water supplied from the outside as tail gas treatment absorption liquid for recycling.
In the embodiment, the sodium hydroxide solution extracted by the bipolar membrane electrodialysis system in the step 2 is sent back to the tail gas washing tower, so that the sodium hydroxide solution is recycled as the tail gas treatment absorption liquid.
In the embodiment, the formic acid separated and collected by electrodialysis in the step 3 is sent back to the tail gas washing tower, so that the formic acid solution is recycled as the tail gas treatment absorption liquid.
In the embodiment, the purified hydrobromic acid aqueous solution obtained by electrodialysis separation in the step 3 enters the terephthalic acid preparation process after being regulated to a certain concentration, so that the hydrobromic acid is recycled as a catalyst raw material in the terephthalic acid preparation process.
Example 2
Step 1: concentrating
As shown in FIG. 6, in this example, the effluent from the washing column having a flow rate of 15000kg/h, containing 33.54kg/h sodium bromide and 16.25kg/h sodium formate was subjected to primary RO reverse osmosis concentration, and thus a concentrated solution 1 having a flow rate of 1500kg/h, containing 32.2kg/h sodium bromide and 15.6kg/h sodium formate and an RO reverse osmosis desalted water 1 having a flow rate of 13500kg/h, containing 1.34kg/h sodium bromide and 0.65kg/h sodium formate were obtained.
The concentrate 1 was subjected to secondary RO reverse osmosis concentration to obtain a concentrate 2 having a flow rate of 150kg/h and containing 30.9kg/h of sodium bromide and 15kg/h of sodium formate, wherein the equivalent concentration of sodium bromide was 2N and the equivalent concentration of sodium formate was 1.5N. After primary and secondary concentration, the equivalent concentration of the concentrated solution accords with the optimal working condition of bipolar membrane electrodialysis in the next step.
And simultaneously, after two-stage concentration, the RO reverse osmosis desalted water 2 with the flow rate of 1350kg/h and containing 1.3kg/h sodium bromide and 0.6kg/h sodium formate is obtained, and the RO reverse osmosis desalted water 2 and the RO reverse osmosis desalted water 1 obtained by 1-stage concentration are sent back to the top of the tail gas washing tower together to replace pure water supplied from the outside to be used as tail gas treatment absorption liquid for recycling.
Step 2: bipolar membrane electrodialysis
As shown in FIG. 7, the concentrated solution 2 obtained in the above step and having a flow rate of 150kg/h and containing 30.9kg/h sodium bromide and 15kg/h sodium formate was subjected to two-stage concentration, and desalted water of 100kg/h was added to a bipolar membrane electrodialysis system, and two products were obtained after bipolar membrane electrodialysis.
Product 1 is a mixture of 127.6kg/h, 19.5kg/h hydrobromic acid and 8.1kg/h formic acid, and product 2 is a sodium hydroxide solution of 122.4kg/h, 16.6kg/h sodium hydroxide, 2kg/h sodium bromide and 8.1kg/h sodium formate. And after the products 1 and 2 are extracted, the products 2 are returned to the tail gas washing tower, and sodium hydroxide is used as tail gas treatment absorption liquid for recycling.
Step 3: electrodialysis
As shown in FIG. 8, the mixed solution obtained in the above step, which has a flow rate of 127.6kg/h, contains 19.5kg/h hydrobromic acid and 8.1kg/h formic acid, is added with 85kg/h desalted water, enters an electrodialysis system for separation, the pH is adjusted to be less than or equal to 3.7, and a hydrobromic acid solution with a flow rate of 100.6kg/h, containing 15.6kg/h hydrobromic acid and a formic acid solution with a flow rate of 112kg/h, containing 8.1kg/h formic acid and 3.9kg/h hydrobromic acid are obtained after separation. The formic acid solution still contains a small amount of hydrobromic acid in order to maintain the pH below 3.7, thus ensuring that the formic acid is not dissociated and obtaining a purified aqueous hydrobromic acid solution.
After separation, the formic acid solution is returned to the tail gas washing tower for recycling of formic acid as the tail gas treatment absorption liquid. The hydrobromic acid solution enters the preparation process of terephthalic acid after being regulated to a certain concentration, and the hydrobromic acid is recycled as a catalyst.
Example 3
Step 1: concentrating
As shown in FIG. 9, in this example, the effluent from the washing column having a flow rate of 15000kg/h, containing 33.54kg/h sodium bromide and 5.51kg/h sodium formate was subjected to primary RO reverse osmosis concentration to obtain concentrate 1 having a flow rate of 1500kg/h, containing 32.2kg/h sodium bromide and 5.21kg/h sodium formate and RO reverse osmosis desalted water 1 having a flow rate of 13500kg/h, containing 1.34kg/h sodium bromide and 0.31kg/h sodium formate.
The concentrate 1 was subjected to two-stage RO reverse osmosis concentration to obtain a concentrate 2 having a flow rate of 150kg/h and containing 30.9kg/h of sodium bromide and 5kg/h of sodium formate, at which time the equivalent concentration of sodium bromide was 2N and the equivalent concentration of sodium formate was 0.5N.
And simultaneously, after two-stage concentration, RO reverse osmosis desalted water 2 with the flow rate of 1350kg/h and containing 1.3kg/h sodium bromide and 0.2kg/h sodium formate is obtained.
The RO reverse osmosis desalted water 2 and the RO reverse osmosis desalted water 1 obtained by the concentration of the level 1 are sent back to the top of the tail gas washing tower together, and the pure water which is supplied outside instead of the original water is used as the tail gas treatment absorption liquid for recycling.
Step 2: bipolar membrane electrodialysis
As shown in FIG. 10, the concentrated solution 2 obtained in the above step and having a flow rate of 150kg/h and containing 30.9kg/h sodium bromide and 5kg/h sodium formate was subjected to two-stage concentration, and 100kg/h desalted water was added to the bipolar membrane electrodialysis system, and after bipolar membrane electrodialysis, two products were obtained.
Product 1 was a mixture of 122.2kg/h, 19.5kg/h hydrobromic acid, 2.7kg/h formic acid, and product 2 was a sodium hydroxide solution of 127.8kg/h, 9.7kg/h sodium hydroxide, 6.2kg/h sodium bromide, 1.0kg/h sodium formate. And (3) after the products 1 and 2 are extracted, the products 2 are returned to the tail gas washing tower, and sodium hydroxide is used as the tail gas treatment absorption liquid for recycling.
Step 3: electrodialysis
As shown in FIG. 11, the mixed solution obtained in the above step, which has a flow rate of 122.2kg/h and contains 19.5kg/h hydrobromic acid and 2.7kg/h formic acid, was fed into an electrodialysis system to be separated, and desalted water of 85kg/h was added to the mixed solution, and the pH was adjusted to 3.7 or less, and after separation, a hydrobromic acid solution having a flow rate of 100.6kg/h and containing 15.6kg/h hydrobromic acid and a formic acid solution having a flow rate of 106.6kg/h and containing 2.7kg/h formic acid and 3.9kg/h hydrobromic acid were obtained.
The formic acid solution still contains a small amount of hydrobromic acid in order to maintain the pH below 3.7, thus ensuring that the formic acid is not dissociated and obtaining a purified aqueous hydrobromic acid solution.
After separation, the formic acid solution is returned to the tail gas washing tower for recycling of formic acid as the tail gas treatment absorption liquid. The hydrobromic acid solution enters the preparation process of terephthalic acid after being regulated to a certain concentration, and the hydrobromic acid is recycled as a catalyst.
Example 4
As shown in fig. 12, this embodiment differs from embodiment 1 in that: the concentration process adopts a multi-effect evaporation device, concentrated solution and multi-effect evaporation condensate are obtained through concentration and separation of the multi-effect evaporation device, the multi-effect evaporation condensate is returned to the top of the tail gas washing tower, and pure water supplied from the outside is replaced to be used as tail gas treatment absorption liquid for recycling. Wherein the multiple effect evaporation can be N-effect evaporation, and N is greater than 1. The rest is the same as in example 1 and will not be described again.
The foregoing is only a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any person skilled in the art will be able to make insubstantial modifications of the present invention within the scope of the present invention disclosed herein by this concept, which falls within the actions of invading the protection scope of the present invention.
Claims (9)
1. The recovery method of the PTA tail gas washing tower effluent is characterized in that the washing tower effluent is obtained by washing PTA tail gas subjected to organic matter removal treatment by using sodium formate and sodium hydroxide solution, and mainly contains sodium formate and sodium bromide according to the material content, and the recovery method comprises the following steps:
step 1: concentrating the effluent of the washing tower containing sodium bromide and sodium formate by adopting a concentration process to obtain concentrated solution and recovery solution of sodium bromide and sodium formate;
step 2: adding a certain amount of desalted water into the sodium bromide and sodium formate concentrated solution obtained in the step 1 to enter a bipolar membrane electrodialysis system for treatment to obtain hydrobromic acid and formic acid mixed solution formed by bromide ions, formate ions and hydrogen ions ionized by a bipolar membrane, and sodium hydroxide solution formed by sodium ions and hydroxide ions ionized by the bipolar membrane;
step 3: and (3) adding the hydrobromic acid and formic acid mixed solution obtained in the step (2) and desalted water into an electrodialysis system, controlling the pH value to be acidic, and separating to obtain a purified hydrobromic acid aqueous solution and a formic acid solution containing a small amount of hydrobromic acid.
2. The PTA off-gas scrubber effluent recovery process according to claim 1, wherein the equivalent concentration of the concentrate in step 1 is 1-2N.
3. The PTA tail gas scrubber effluent recovery method according to claim 2, wherein the concentration process in step 1 employs an RO reverse osmosis membrane device, and the recovery liquid is RO reverse osmosis desalted water.
4. The PTA tail gas scrubber effluent recovery method according to claim 2, wherein the concentration process of step 1 employs a multi-effect evaporation apparatus, and the recovery liquid is a multi-effect evaporation condensate.
5. The PTA off-gas scrubber effluent recovery method according to claim 3, wherein said RO reverse osmosis membrane unit comprises a two-stage RO reverse osmosis membrane.
6. The PTA off-gas scrubber effluent recovery process according to claim 1, wherein the PH range is 3.7 or less.
7. The PTA off-gas scrubber effluent recovery process according to claim 1, wherein the recovery liquid from step 1 is returned to the scrubber.
8. The PTA off-gas scrubber effluent recovery process according to claim 1, wherein the sodium hydroxide solution of step 2 is returned to the scrubber.
9. The PTA off-gas scrubber effluent recovery method according to claim 1, wherein the purified hydrobromic acid aqueous solution of step 3 is adjusted to a concentration to enter a terephthalic acid production process, and the formic acid solution of step 3 is returned to the scrubber.
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