CN114100167B - Energy-saving maleic anhydride absorption deep analysis refining process - Google Patents
Energy-saving maleic anhydride absorption deep analysis refining process Download PDFInfo
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- CN114100167B CN114100167B CN202111416950.9A CN202111416950A CN114100167B CN 114100167 B CN114100167 B CN 114100167B CN 202111416950 A CN202111416950 A CN 202111416950A CN 114100167 B CN114100167 B CN 114100167B
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- 238000010521 absorption reaction Methods 0.000 title claims abstract description 91
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims abstract description 39
- 238000004458 analytical method Methods 0.000 title claims abstract description 37
- 238000007670 refining Methods 0.000 title description 6
- 239000002904 solvent Substances 0.000 claims abstract description 139
- 238000003795 desorption Methods 0.000 claims abstract description 68
- 238000012856 packing Methods 0.000 claims abstract description 47
- 239000007788 liquid Substances 0.000 claims abstract description 23
- 238000003303 reheating Methods 0.000 claims abstract description 22
- 239000000463 material Substances 0.000 claims abstract description 11
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims abstract description 7
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000012071 phase Substances 0.000 claims description 40
- 239000011552 falling film Substances 0.000 claims description 31
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 claims description 22
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 claims description 21
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 claims description 21
- 239000011976 maleic acid Substances 0.000 claims description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- 238000001704 evaporation Methods 0.000 claims description 15
- 230000008020 evaporation Effects 0.000 claims description 14
- 150000008064 anhydrides Chemical class 0.000 claims description 10
- 230000005484 gravity Effects 0.000 claims description 10
- 230000000630 rising effect Effects 0.000 claims description 10
- 238000011144 upstream manufacturing Methods 0.000 claims description 9
- 238000001816 cooling Methods 0.000 claims description 8
- 239000007791 liquid phase Substances 0.000 claims description 8
- 230000001174 ascending effect Effects 0.000 claims description 7
- 238000000605 extraction Methods 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- 238000010992 reflux Methods 0.000 claims description 6
- 230000008929 regeneration Effects 0.000 claims description 5
- 238000011069 regeneration method Methods 0.000 claims description 5
- 239000012808 vapor phase Substances 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 4
- 229920006395 saturated elastomer Polymers 0.000 claims description 3
- 239000000945 filler Substances 0.000 claims 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims 1
- 230000018044 dehydration Effects 0.000 description 9
- 238000006297 dehydration reaction Methods 0.000 description 9
- 208000005156 Dehydration Diseases 0.000 description 7
- 238000000354 decomposition reaction Methods 0.000 description 4
- 239000004258 Ethoxyquin Substances 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 239000004257 Anoxomer Substances 0.000 description 2
- 239000004255 Butylated hydroxyanisole Substances 0.000 description 2
- VZCYOOQTPOCHFL-OWOJBTEDSA-N Fumaric acid Chemical compound OC(=O)\C=C\C(O)=O VZCYOOQTPOCHFL-OWOJBTEDSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000007701 flash-distillation Methods 0.000 description 2
- XNGIFLGASWRNHJ-UHFFFAOYSA-N phthalic acid Chemical compound OC(=O)C1=CC=CC=C1C(O)=O XNGIFLGASWRNHJ-UHFFFAOYSA-N 0.000 description 2
- 239000004322 Butylated hydroxytoluene Substances 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- LGRFSURHDFAFJT-UHFFFAOYSA-N Phthalic anhydride Natural products C1=CC=C2C(=O)OC(=O)C2=C1 LGRFSURHDFAFJT-UHFFFAOYSA-N 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- JHIWVOJDXOSYLW-UHFFFAOYSA-N butyl 2,2-difluorocyclopropane-1-carboxylate Chemical compound CCCCOC(=O)C1CC1(F)F JHIWVOJDXOSYLW-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- LDCRTTXIJACKKU-ARJAWSKDSA-N dimethyl maleate Chemical compound COC(=O)\C=C/C(=O)OC LDCRTTXIJACKKU-ARJAWSKDSA-N 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 239000010408 film Substances 0.000 description 1
- 239000001530 fumaric acid Substances 0.000 description 1
- NKHAVTQWNUWKEO-UHFFFAOYSA-N fumaric acid monomethyl ester Natural products COC(=O)C=CC(O)=O NKHAVTQWNUWKEO-UHFFFAOYSA-N 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- NKHAVTQWNUWKEO-IHWYPQMZSA-N methyl hydrogen fumarate Chemical compound COC(=O)\C=C/C(O)=O NKHAVTQWNUWKEO-IHWYPQMZSA-N 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
- XNGIFLGASWRNHJ-UHFFFAOYSA-L phthalate(2-) Chemical compound [O-]C(=O)C1=CC=CC=C1C([O-])=O XNGIFLGASWRNHJ-UHFFFAOYSA-L 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000003797 solvolysis reaction Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/30—Accessories for evaporators ; Constructional details thereof
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01B—BOILING; BOILING APPARATUS ; EVAPORATION; EVAPORATION APPARATUS
- B01B1/00—Boiling; Boiling apparatus for physical or chemical purposes ; Evaporation in general
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/22—Evaporating by bringing a thin layer of the liquid into contact with a heated surface
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/06—Flash distillation
-
- 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
- B01D53/1418—Recovery of products
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—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
- B01D53/1425—Regeneration of liquid absorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
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- Treating Waste Gases (AREA)
- Gas Separation By Absorption (AREA)
Abstract
The invention discloses an energy-saving maleic anhydride absorption depth analysis process, wherein a dehydrated rich solvent at the bottom of an absorption tower enters an analysis tower, a poor solvent at the bottom of the analysis tower enters a reheating flash tower, the poor solvent at the bottom of the reheating flash tower enters the top of the absorption tower, the poor solvent at the top of the analysis tower enters the absorption tower to remove light components such as acrylic acid and the like, and maleic anhydride is recovered; extracting the side line of the resolution tower to a product tower, exchanging heat between the extracted gas phase at the side line of the product tower and the feeding material of the product tower to recover energy, and then condensing to obtain a superior liquid maleic anhydride; and recovering energy from the gas phase at the top of the product tower to the lower side of the lower packing of the feeding material of the desorption tower. The invention has the advantages of low investment, low power consumption and low steam consumption, and the yield of the maleic anhydride is improved by adopting the reheating type post flash tower.
Description
Technical Field
The invention belongs to the maleic anhydride industry, and particularly relates to an energy-saving maleic anhydride absorption deep analysis refining process.
Background
The absorption and desorption process in the existing maleic anhydride industry has the following defects:
maleic anhydride reacts with water in the air and water generated by the reaction in the absorption tower to generate maleic acid and trace fumaric acid, and the continuous operation of the device is influenced and the yield of the maleic anhydride is reduced by exceeding a certain amount, so that a rich solvent dehydration unit is required to be arranged.
At present, two methods for dehydrating the rich solvent exist in the production process, and both the methods need to be provided with a dehydration unit, so that the energy consumption is increased, and the investment is high. One is to use a stripping tower, the top of the tower enters a heated rich solvent, flows downwards, and transfers heat and mass with hot air entering from the bottom of the tower, free water and part of maleic acid dehydrated water in the rich solvent are carried out by the air and returned to an absorption tower, and the maleic acid in the rich solvent is reduced to a required value of the process, and the process needs a rich solvent pump and power of stripping air and the rich solvent is heated to consume steam. The other method is vacuum dehydration, the rich solvent at the bottom of the absorption tower enters a vacuum dehydration tank, free water in the rich solvent is vaporized after flash evaporation and is pumped away by a vacuum pump, maleic acid in the rich solvent cannot be increased continuously, and the process has no good dehydration process of a stripping tower and needs power of the vacuum pump and power consumption of a rich solvent pump.
The components at the bottom of the desorption tower are difficult to vaporize under the operation condition at the bottom of the tower, the establishment of thermosiphon is difficult, forced circulation is forced to pass through a reboiler for heating, and then the components are flashed at the bottom of the desorption tower to provide medium steam upwards along the tower for the desorption tower to transfer heat with liquid flowing downwards in a packing of the desorption tower, so that desorption rectification is realized. The reboiler at the bottom of the desorption tower of the process needs forced circulation, and electric energy is wasted.
The reboiler at the bottom of the analytic tower and the feed heater of the back flash tower both need to use high-grade saturated steam with the pressure of more than 3.5MPa, so that the heat transfer temperature difference of the heat exchanger is ensured, if the steam pressure is reduced, the heat exchange area needs to be greatly increased, and if the steam pressure is too low, the heat exchange area is large again and cannot work.
Since the saturation temperature of the heater using 3.5MPa steam is high, the temperature at the bottom of the desorption tower is up to 198 ℃, the solvent decomposition rate is increased, and the solvent decomposition amount is larger.
No high-grade maleic anhydride can be extracted from the side line of the desorption tower, and crude anhydride, namely unqualified maleic anhydride, is extracted, wherein the side line contains solvolysis products, such as dimethyl maleate, monomethyl maleate, phthalic acid, phthalic anhydride and monoester phthalate.
The yield of the absorption and analysis system is low. The post flash column adopts a first flash, and the maleic anhydride content in the lean solvent at the bottom of the column is 0.25 percent by weight. Resulting in high COD of the wastewater generated in the subsequent solvent regeneration section. If the content of the maleic anhydride in the lean solvent is reduced, the distilled solvent is too large, and the yield of an absorption tower or a vent washing tower is influenced.
The energy consumption of the crude anhydride refining system is high.
Disclosure of Invention
The invention aims to provide an energy-saving maleic anhydride absorption deep analysis process, wherein a rich solvent at the bottom of an absorption tower does not need dehydration treatment, so that the contact time of maleic anhydride and water is reduced, and the generation amount of maleic acid and trans-acid is reduced; the equipment investment and the operating cost of the dehydration unit are saved.
In order to achieve the purpose, the invention provides the following technical scheme:
an energy-saving maleic anhydride absorption depth analysis process comprises the steps that dehydrated rich solvent at the bottom of an absorption tower enters an analysis tower, lean solvent at the bottom of the analysis tower enters a falling film evaporation reboiler at the bottom of the analysis tower (the gas phase of a reboiler enters the bottom of the analysis tower), the solvent at the bottom of a falling film reboiler at the bottom of the analysis tower enters a reheating flash tower, the lean solvent at the bottom of the reheating flash tower enters the top of the absorption tower, the lean solvent at the top of the analysis tower is extracted and enters the absorption tower to remove light components such as acrylic acid, and maleic anhydride is recovered; and (3) carrying out gas phase heat exchange between the side line extraction of the desorption tower and the side line extraction of the product tower (the feeding part of the product tower reaches the top of the product tower, and the part of the feeding part of the product tower reaches the lower part of the first layer of packing on the product tower) to recover energy, and then carrying out recondensation on the side line of the product tower to obtain the high-grade liquid maleic anhydride. And recovering energy from the gas phase at the top of the product tower to the lower side of the lower packing of the feeding material of the desorption tower.
The specific process flow is as follows:
the mixture containing maleic anhydride gas at 125-185 ℃ in the upstream process enters an absorption tower and passes through a 2-layer high-temperature stripping section upwards to remove maleic acid in a rich solvent flowing down from the absorption tower. The rich solvent without maleic acid flows to the low-temperature gas stripping section by means of gravity to remove free water in the rich solvent, then the rich solvent without maleic acid and free water passes through an absorption tower bottom pump, a lean rich solvent heat exchanger and the upper part of a lower packing of an analytical tower, after negative pressure flash evaporation, light components flow upwards through two sections of packing to a condenser at the top of the analytical tower, condensate of the condenser is sent to the top of the analytical tower by a reflux pump, flows downwards to transfer heat with gas rising in the packing, liquid maleic anhydride is extracted from the upper first layer of packing, part of the liquid maleic anhydride is sent to the top of a product tower, part of the liquid maleic anhydride passes through a lateral line for heat exchange and then is sent to the upper first section of packing of the product tower, then gas phase is extracted from the lower side of the upper second layer of the product tower, most of the gas phase is condensed after heat exchange with feed to obtain high-grade liquid maleic anhydride, and the uncondensed gas phase light components enter the upper first layer of the product tower.
The gas rising from the absorption tower passes through the first cooling circulation section, transfers heat with the semi-rich solvent left at the upper part, and absorbs the maleic anhydride in the gas phase at a controlled temperature to flow downwards into the semi-rich solvent; the gas phase which flows upwards through the first cooling circulation passes through a second cooling circulation section, and is subjected to mass and heat transfer with the semi-lean solvent left at the upper part, and the maleic anhydride in the gas phase is absorbed into the semi-lean solvent to flow downwards at controlled temperature; the gas phase which flows through the second cooling circulation section in an ascending way passes through the lean solution absorption section, and the gas phase and the lean solvent left at the upper part are subjected to mass and heat transfer, so that the maleic anhydride in the gas phase is absorbed and flows down into the lean solvent; the gas phase which ascends and flows through the barren solution absorption section is completely deprived of maleic anhydride, and the tail gas is removed from the top of the absorption tower to be burned.
Heavy components of a feed rich solvent of the desorption tower, which are flashed in the desorption tower, flow downwards to a lower section of packing and transfer heat with vapor generated by reboiling at the bottom of the tower, gas phase enters an upper section of packing layer, liquid phase is pumped to a falling film reboiler, light components are vaporized, and the heavy components flow to a reheating flash tower by virtue of gravity; extracting and striking a layer 8 tray of an absorption tower from the top of the desorption tower, removing acrylic acid, and recovering maleic anhydride; the lean solvent at the bottom of the reboiler of the desorption tower flows to the reheat flash tower by virtue of gravity, the lean solvent and liquid condensed by the condenser at the top of the reheat flash tower perform mass transfer and heat transfer with a vapor phase rising from a packing layer and a falling film evaporator, vapor passing through the packing layer enters the condenser at the top of the tower, heavy components flowing through the packing layer enter the falling film evaporator to be evaporated again, rising vapor is provided, the lean solvent contains 0.05-0.10% of anhydride at the bottom of the reheat flash tower, the lean solvent is pumped to the top of an absorption tower, the top of an exhaust washing tower and a solvent regeneration system, and the solvent is sent to the top of the absorption tower after being regenerated.
The feeding of the product tower is extracted and provided by a side line of the desorption tower, wherein part of the feeding is sent to the top of the product tower, part of the feeding exchanges heat with the side line of the product tower and then is sent to the first layer of packing on the product tower, and the flashed gas phase flows upwards and then is sent to the third section of packing on the desorption tower through the top of the product tower; the liquid phase and the liquid phase left at the top of the tower transfer heat downwards with the gas phase provided by a reboiler at the bottom of the tower, and the heavy components at the bottom of the product tower are sent to a feeding section of the desorption tower to recover materials; the ascending vapor phase is extracted from the upper second layer of the packing of the product tower, exchanges heat with the feed of the product tower and is condensed into liquid superior maleic anhydride.
The absorption tower utilizes the maleic anhydride-containing gas mixture at the temperature of 125-185 ℃ in the upstream process to enter the tower, strip the rich solvent, reduce the content of the maleic acid in the rich solvent by less than 0.60 percent by weight, and a float tray or a packing is arranged in a high-temperature stripping section.
Stripping the rich solvent from the bottom of the absorption tower by using air or water-removing air, wherein the stripped rich solvent flows to a stripping section by means of gravity, the content of the maleic acid in the rich solvent is less than 0.60 percent by weight, and the operating temperature of the rich solvent discharged from the bottom of the absorption tower is 106-135 ℃.
The method realizes that the low-temperature stripping gas is not supplied to the absorption tower by optimizing the operating parameters of the absorption tower.
The height difference of the bottom of the desorption tower to the falling film evaporation reboiler at the bottom of the desorption tower must meet the requirement that the minimum resistance of vapor evaporated by the falling film evaporator enters the bottom of the desorption tower, and gravity flow feeding is adopted for feeding of a deep desorption reheating type rear flash tower.
The process comprises the steps of adopting a falling film evaporator at the bottom of a reheating type after-flash tower where the solvent at the bottom of the desorption tower enters, arranging a condenser at the top of the tower, and adopting falling film evaporation for a solvent heater containing the feed of the after-flash tower.
And a reboiler at the bottom of the desorption tower and a reboiler at the bottom of the reheat type post-flash tower for deep desorption of the solvent at the bottom of the desorption tower are used, and saturated steam of 2.0-2.8 Mpa is used.
The gas phase at the top of the product tower enters a third layer of packing on the upper part of the desorption tower, and energy is recovered; and the gas phase extraction at the side of the product tower exchanges heat with the feeding material of the product tower to recover energy.
Compared with the prior art, the invention has the beneficial effects that:
the absorption tower is provided with a first-stage circulation and a second-stage circulation which are used for controlling the temperature at the top of the absorption tower and the temperature at the bottom of the absorption tower. The temperature at the top of the tower is higher than 72 ℃, and the solvent loss is increased; the temperature of the bottom of the column is lower than 105 ℃ and the maleic acid in the rich solvent is increased.
The lower part of the gas phase feeding of the absorption tower is provided with a maleic acid removing section, and the lower part of the maleic acid removing section is provided with a gas stripping section. The high-temperature gas from the cooler of the upstream process two and the rich solvent flowing down from the upper part of the absorption tower are used for dehydrating the maleic acid in the rich solvent to generate maleic anhydride and part of free water. The rich solvent continuously flows downwards into the stripping section and is in mass transfer and heat transfer with hot air (or dehydrated air) supplemented at the bottom of the tower, free water in the rich solvent is carried away by the air flowing upwards, and the rich solvent with the maleic acid content of less than 0.6% flows out from the bottom of the tower. The process does not need a rich solvent delivery pump and does not need external supplementary heat, thereby achieving the purpose of energy conservation.
The falling film reboiler at the bottom of the desorption tower is arranged at the lower part of the desorption tower, a liquid film on the tube wall flows downwards under the working state of a heat exchange tube of the falling film evaporator, the middle space of the tube is connected with a gas phase at the bottom of the desorption tower, and gas evaporated by the falling film evaporator can smoothly flow to the bottom of the desorption tower, so that the operation pressure is reduced, and the operation temperature is further reduced. Greatly reduces the decomposition amount of the solvent.
The invention adopts a reheating type post flash tower. The solvent at the bottom of the reboiler of the desorption tower enters a reheating type post-flash tower, the liquid after flash evaporation flows into a packing layer to transfer heat with the evaporated gas of the falling-film evaporator at the bottom of the tower, the gas flows to a condenser at the top of the tower to be partially condensed, the condensed liquid flows back to the packing layer, the non-condensable gas enters a gas-discharging washing tower at a subsequent working section, and the lean solvent at the bottom of the falling-film evaporator has extremely low maleic anhydride content and is used for an absorption tower and the gas-discharging washing tower.
Because the desorption tower and the reheating flash tower both use the falling film evaporator, the vapor pressure for desorption can be reduced to 2.2-2.5 MPaG. The back pressure can be used to recover pressure energy from the turbine.
A first-stage circulating hot water cooler and a lean solvent hot water cooler are added, and the generated high-temperature water is supplied to a butane evaporator and a carbon four-separation system for use, so that the aim of saving energy is fulfilled.
The temperature of the outlet of the secondary cooler in the upstream procedure is required to be 125-135 ℃ and enter the absorption tower, so that the first-stage and second-stage circulation volume is reduced, and the electric energy is saved.
Due to deep analysis, the content of maleic anhydride in the lean solvent at the bottom of the reheat flash tower is reduced to 0.05-0.10 percent, but the yield of maleic anhydride is improved by 0.3 percent, and the total amount of COD generated in the subsequent solvent regeneration section of the maleic anhydride device is reduced by 30 percent.
The gas phase at the top of the product tower enters the upper third layer of packing of the desorption tower, and the gas stripping desorption tower feeds the heavy components after flash evaporation, so that the energy is recovered; and the gas phase extraction at the side of the product tower exchanges heat with the feeding material of the product tower to recover energy.
Low investment, low power consumption and low steam consumption. Compared with the traditional process, the process has no dehydration unit and a vacuum pump of a crude anhydride refining unit, and the investment is reduced when the grade of a steam pipe network is reduced. And a rich solvent pump for a dehydration process and a forced circulating pump of a reboiler at the bottom of the desorption tower are not provided, so that the power consumption of a maleic anhydride device is reduced. The heat of the product tower is recovered, and the steam consumption is greatly reduced.
Drawings
FIG. 1 is a process flow diagram of the process of the present invention.
In the figure, a G312-second-stage circulating pump, an E312-second-stage water cooler, a T310-absorption tower, a G310-absorption tower bottom pump, a G311-first-stage circulating pump, an E311A-first-stage circulating first cooler, an E311B-first-stage circulating second cooler, an E310A-lean rich agent heat exchanger, an E310B-lean agent warm water cooler, an E310C-lean agent hot water cooler, a G324-after flash tower bottom pump, an E323-flash reboiler, an E324-after flash tower top condenser, a T320-desorption tower, an E320-tower bottom falling film reboiler, a G320-desorption tower reboiler bottom pump, a G321-desorption tower top reflux pump, a G330-product tower bottom recombination branch pump, a T330-product tower, an E330-product reboiler tower bottom, an E331-product tower feed heat exchanger, an E332-product tower side line condenser, a G332-side line product take-out pump, an E321-desorption tower top condenser and a G321-desorption tower top reflux pump.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention include, but are not limited to, the scope shown in the following examples.
Referring to fig. 1, an energy-saving maleic anhydride absorption depth analysis process, a dehydrated rich solvent at the bottom of an absorption tower T310 enters an analysis tower, a lean solvent at the bottom of the analysis tower enters an analysis tower bottom falling film reboiler (the gas phase of the falling film reboiler returns to the bottom of the analysis tower), a falling film reboiler at the bottom of the analysis tower enters a reheating flash tower, the lean solvent at the bottom of the reheating flash tower enters the top of the absorption tower, the lean solvent at the top of the analysis tower enters the absorption tower T310 to remove light components such as acrylic acid, and maleic anhydride is recovered; and (3) performing heat exchange between the side liquid phase extraction of the desorption tower T320 and the side gas phase extraction of the product tower (the side line of the desorption tower T320 is the part of the feeding material of the product tower to the top of the product tower, and the part of the feeding material of the product tower is arranged below the first layer of packing on the product tower T330) to recover energy, and then performing recondensation on the side line of the product tower T330 to obtain the high-grade liquid maleic anhydride. The gas phase at the top of the product tower returns energy to the lower side of the lower packing of the feed of the desorption tower T320.
The energy-saving maleic anhydride absorption, analysis and refining process flow comprises an upstream process mixed gas flow, an absorption tower bottom rich solvent flow and a lean solvent flow, and each flow is specifically explained as follows:
an upstream process mixed gas flow: the mixed gas containing maleic anhydride at high temperature in the reaction section enters an absorption tower T310, and after going through 2 layers of deacidification tower trays upwards along the tower, the mixed gas is subjected to mass transfer and heat transfer with a solvent flowing downwards through 28 layers of tower trays, maleic anhydride in the gas is absorbed by the solvent to generate a rich solvent which flows downwards, and tail gas without maleic anhydride is discharged to an incinerator from the top of the tower. The rich solvent flowing downwards flows into the deacidification section of the absorption tower to transfer heat with the high-temperature anhydride-containing gas coming from the upstream process of the tower, and the maleic acid in the rich solvent is taken away by the rising air and is discharged to a tail gas incinerator from the top of the absorption tower. The deacidified rich solvent passes through a low-temperature stripping section at the bottom of the tower to remove free water in the rich solvent, and the deacidified and dehydrated rich solvent enters a rich solvent pump at the bottom of an absorption tower. The tower top temperature controls the absorption tower top to 70 ℃ through the second-stage circulation amount and the second-stage cooled temperature; the temperature of the bottom of the absorption tower is controlled by the first-stage circulation amount and the first-stage cooled temperature.
Absorption tower bottom rich solvent flow: the rich solvent of the absorption tower bottom pump passes through the absorption tower bottom pump → the lean rich solvent heat exchanger → the upper part of the packing at the lower part of the desorption tower T320, after negative pressure flash evaporation, the light component flows upwards through the 2 sections of packing to the condenser E321 at the top of the desorption tower, the condensate is sent to the top of the desorption tower through the reflux pump G321 at the top of the desorption tower, flows downwards to transfer heat with the gas rising in the packing, and the liquid maleic anhydride is pumped out from the first layer of packing from the top to feed the product tower T330. The heavy component after the rich solvent flash evaporation flows downwards to the lower section of packing and transfers heat with the steam generated by the reboiling at the bottom of the tower, the gas phase enters the upper section 2 of packing layer, the liquid phase is pumped to the falling film reboiler, the light component is vaporized, and the heavy component is pumped to the reheating flash tower through the bottom of the falling film reboiler. The bottom discharging temperature of a falling film reboiler E320 at the bottom of the desorption tower is controlled to be 183-195 ℃ by controlling the steam quantity of the reboiler and the pressure at the top of the tower; the temperature at the top of the desorption tower is controlled to be between 78 and 85 ℃ by controlling the reflux quantity. And extracting from the top of the desorption tower, pumping the tower tray 8 of the absorption tower T310, removing acrylic acid, and recovering maleic anhydride.
By optimizing the operating parameters of the absorber T310, the supply of the low-temperature stripping gas can be stopped, which is more energy-saving.
Lean solvent flow scheme: the bottom of a falling film reboiler E320 at the bottom of the desorption tower is provided with lean solvent containing 0.25-1.20% of maleic anhydride, the lean solvent is pumped to a packing layer of a reheating flash tower, liquid after flash evaporation flows downwards, the liquid condensed by a condenser E324 at the top of the flash tower and the packing layer perform mass transfer and heat transfer with vapor phase rising from the flash reboiler E323, vapor passing through the packing layer enters the condenser E324 at the top of the flash tower, and the outlet temperature at the top of the flash tower is controlled by controlling warm water flow of the condenser E324 at the top of the flash tower to be 90 ℃ and then enters a process exhaust washing tower. Heavy components passing through the packing layer flow into a flash distillation reboiler E323 to be evaporated again to provide rising gas, the content of lean solvent anhydride at the bottom of the reheating flash distillation tower is 0.05-0.10 percent, the lean solvent anhydride is pumped to the top of the absorption tower, the top of the exhaust washing tower and a solvent regeneration system, and the solvent is sent to the top of the absorption tower after being regenerated.
And controlling the content of the poor solvent anhydride at the bottom of the reheat flash tower by controlling the steam quantity at the bottom of the reheat flash tower.
Finally realizing the stable circulation of the rich solvent at the bottom of the absorption tower → the desorption tower, the lean solvent at the bottom of the desorption tower → the reheat flash tower, the lean solvent at the bottom of the reheat flash tower → the top of the absorption tower and the three towers, and balancing the decomposition amount of the solvent in the rich solvent by the amount of the regenerated solvent. When the solvent in the system is insufficient, the solvent can be supplemented.
The specific process parameters of the process of the invention are shown in the following table.
The invention is not limited to the examples, and any equivalent changes to the technical solution of the invention by a person skilled in the art after reading the description of the invention are covered by the claims of the invention.
Claims (7)
1. An energy-saving maleic anhydride absorption depth analysis process is characterized in that:
the dehydrated rich solvent at the bottom of the absorption tower enters an absorption tower, the lean solvent at the bottom of the absorption tower enters a reheating flash tower, the lean solvent at the bottom of the reheating flash tower enters the top of the absorption tower, the lean solvent at the top of the absorption tower enters the absorption tower to remove light components such as acrylic acid and the like, and maleic anhydride is recovered; extracting the side line of the resolution tower to a product tower, exchanging heat between the extracted gas phase at the side line of the product tower and the feeding material of the product tower to recover energy, and then condensing to obtain a superior liquid maleic anhydride; recovering energy from the gas phase at the top of the product tower to the lower side of the lower-layer filler fed into the desorption tower;
the specific process flow is as follows:
the mixture containing maleic anhydride gas at 125-185 ℃ in the upstream process enters an absorption tower, and maleic acid in a rich solvent flowing down from the absorption tower is removed through a 2-layer high-temperature stripping section; the rich solvent without maleic acid flows to the low-temperature gas stripping section by means of gravity to remove free water in the rich solvent, then the rich solvent without maleic acid and free water passes through an absorption tower bottom pump, a lean rich solvent heat exchanger and the upper part of a lower packing of an analytical tower, after negative pressure flash evaporation, light components flow upwards through two sections of packing to a condenser at the top of the analytical tower, condensate of the condenser is sent to the top of the analytical tower by a reflux pump, flows downwards to transfer heat with gas rising in the packing, liquid crude maleic anhydride is extracted from the upper first layer of packing, part of the liquid crude maleic anhydride is sent to the top of a product tower, part of the liquid crude maleic anhydride is sent to the upper first section of packing of the product tower after lateral line heat exchange, then gas phase is extracted from the lower side of the upper second layer of the product tower and is subjected to heat exchange with feed and then mostly condensed to obtain high-grade liquid maleic anhydride, and the uncondensed gas phase light components are sent to the upper first layer of the product tower.
2. The energy-saving maleic anhydride absorption depth analysis process according to claim 1, characterized in that:
gas rising from the absorption tower passes through the first cooling circulation section, and is subjected to mass and heat transfer with the semi-rich solvent flowing downwards from the upper part, and maleic anhydride in a gas phase is absorbed by controlling the temperature to flow into the semi-rich solvent and the lower part of the semi-rich solvent; the gas phase which flows upwards through the first cooling circulation passes through the second cooling circulation section, and is subjected to mass and heat transfer with the semi-lean solvent left at the upper part, and the maleic anhydride in the gas phase is absorbed by controlling the temperature to flow into the semi-lean solvent and flow down the semi-rich solvent; the gas phase which flows through the second cooling circulation section in an ascending way passes through the lean solution absorption section, and the gas phase and the lean solvent left at the upper part are subjected to mass transfer and heat transfer to absorb the maleic anhydride in the gas phase to flow down the semi-rich solvent in the lean solvent; the gas phase which flows through the absorption section of the barren solution in an ascending way is completely deprived of maleic anhydride, and the tail gas is removed from the top of the absorption tower to burn the working section.
3. The energy-saving maleic anhydride absorption depth analysis process according to claim 2, characterized in that:
the heavy component of the feed rich solvent of the desorption tower which is flashed in the desorption tower flows downwards to the lower section of packing and transfers heat with the steam generated by reboiling at the bottom of the tower, the gas phase enters the upper section of packing layer, the liquid phase is pumped to a falling film reboiler at the bottom of the desorption tower, the light component is vaporized, and the heavy component flows to the reheating flash tower by virtue of gravity; the tower top is analyzed and extracted to the tower tray of the layer 8 of the absorption tower, acrylic acid is removed, and maleic anhydride is recovered; the lean solvent at the bottom of the reboiler of the desorption tower flows to the reheat flash tower by virtue of gravity, the lean solvent and the liquid condensed by the condenser at the top of the reheat flash tower perform mass transfer and heat transfer with the ascending vapor phase of the packing layer and the falling film evaporator, the vapor passing through the packing layer enters the condenser at the top of the tower, the heavy component flow passing through the packing layer enters the falling film evaporator for re-evaporation to provide ascending vapor, the lean solvent at the bottom of the reheat flash tower has the anhydride content of 0.05-0.10 percent, and the lean solvent is pumped to the top of the absorption tower, exhausted to the top of the washing tower and a solvent regeneration system, and the solvent is regenerated and then sent to the top of the absorption tower.
4. The energy-saving maleic anhydride absorption depth analysis process according to claim 3, characterized in that:
the feeding of the product tower is provided by side line extraction of the desorption tower, wherein part of the feeding is fed to the top of the product tower, part of the feeding exchanges heat with the side line of the product tower and then is fed to the upper part of the product tower under the first layer of packing, and the flashed gas phase flows upwards and is fed to the upper part of the desorption tower under the third section of packing through the top of the product tower; the liquid phase and the liquid phase flowing down from the top of the tower transfer heat with the gas phase provided by the reboiler at the bottom of the tower, and the heavy component at the bottom of the tower is sent to the feeding section of the desorption tower to recover the material; the ascending vapor phase is extracted under the second layer of the packing on the product tower, exchanges heat with the feeding material of the product tower and is condensed into liquid superior cis-butenedioic anhydride.
5. The energy-saving maleic anhydride absorption depth analysis process according to claim 4, characterized in that:
the absorption tower utilizes the mixture of gas containing maleic anhydride and the temperature of 125-185 ℃ in the upstream process to enter the tower, the rich solvent is stripped, the water content for reducing the maleic acid content in the rich solvent is reduced by less than 0.60 percent by weight, and a float tray or a filler is arranged in a high-temperature stripping section;
stripping the rich solvent at the bottom of the absorption tower by using air or dewatering air, wherein the stripped rich solvent flows to a stripping section by means of gravity, the content of maleic acid in the rich solvent is less than 0.60 percent by weight, and the operating temperature of the rich solvent discharged from the bottom of the absorption tower is 106-135 ℃;
the method realizes that the low-temperature stripping gas is not supplied to the absorption tower by optimizing the operating parameters of the absorption tower.
6. The energy-saving maleic anhydride absorption depth analysis process according to claim 5, characterized in that:
the height difference of the analysis tower bottom to the falling film evaporation reboiler at the analysis tower bottom is larger than that of the falling film evaporation reboiler at the analysis tower bottom, the minimum resistance of vapor evaporated by the falling film evaporator is required to enter the analysis tower bottom, and gravity flow feeding is adopted for feeding of the deep analysis reheating flash tower;
adopting a falling film evaporator at the bottom of a reheating flash tower where the solvent enters from the bottom of the desorption tower, and arranging a condenser at the top of the tower; a solvent heater for feeding the reheating flash tower adopts falling film evaporation;
and a reboiler at the bottom of the desorption tower and a reboiler at the bottom of the reheat flash tower for deep desorption of the solvent at the bottom of the desorption tower use 2.0-2.8 Mpa saturated steam.
7. The energy-saving maleic anhydride absorption depth analysis process according to claim 6, characterized in that:
the bottom of the resolution tower reboiler is additionally provided with a pump for generating a lean solvent with an anhydride content of less than 0.2% at the bottom of the resolution tower reboiler.
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