CN113105415B - Method for separating tetrahydrofuran from esterification wastewater - Google Patents
Method for separating tetrahydrofuran from esterification wastewater Download PDFInfo
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- C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
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Abstract
The invention relates to the technical field of tetrahydrofuran recovery, and particularly discloses a method for separating tetrahydrofuran from esterification wastewater. The method for separating tetrahydrofuran from esterification wastewater comprises the following steps: and sequentially carrying out normal-pressure rectification, pervaporation dehydration, light component removal, hydrogenation reduction and heavy component removal on the esterification wastewater to obtain a tetrahydrofuran product. The method for separating tetrahydrofuran from esterification wastewater provided by the invention has the advantages of high recovery efficiency, low energy consumption, low cost, high product purity and high yield, and can directly recover and obtain polymerization-grade tetrahydrofuran, thereby greatly improving the value and application range of the separated tetrahydrofuran product.
Description
Technical Field
The invention relates to the technical field of tetrahydrofuran recovery, in particular to a method for separating tetrahydrofuran from esterification wastewater.
Background
During the esterification process in the production of PBAT, a large amount of esterification wastewater is produced, which contains about 50-60% of water, 40-50% of Tetrahydrofuran (THF) and small amounts of impurities such as tributen-1-ol, 1, 4-butanediol, 2, 3-dihydrofuran, 2, 5-dihydrofuran, n-butanol, etc. The tetrahydrofuran contains a large amount of impurities which have similar physicochemical properties with the tetrahydrofuran, so that the recovery and separation processes of the tetrahydrofuran are difficult, and the purity of the tetrahydrofuran obtained by recovery is low.
The recovery of tetrahydrofuran usually adopts a method combining normal pressure and pressurization treatment, and in the pressurization process, about 50% of feed liquid needs to be repeatedly pressurized and dehydrated, so that the pressurization tower equipment is large, the energy consumption in the operation process is high, and the tetrahydrofuran product obtained by the existing recovery method can only be used as a solvent because of containing inevitable impurities, cannot be directly polymerized to produce polytetrahydrofuran, influences the application range of the polytetrahydrofuran, and cannot be used as a raw material for preparing downstream high-end products.
Disclosure of Invention
Aiming at the problems of tetrahydrofuran recovered from the esterification wastewater in the prior art, the invention provides the method for separating tetrahydrofuran from the esterification wastewater, the method for separating tetrahydrofuran from the esterification wastewater can realize high-efficiency recovery of tetrahydrofuran, has low energy consumption, simple operation and high product purity, and can directly recover and obtain polymer-grade tetrahydrofuran.
In order to achieve the purpose of the invention, the embodiment of the invention adopts the following technical scheme:
a method for separating tetrahydrofuran from esterification wastewater comprises the steps of carrying out normal-pressure rectification, pervaporation dehydration, light component removal, hydrogenation reduction and heavy component removal treatment on the esterification wastewater in sequence to obtain a tetrahydrofuran product.
Compared with the existing normal pressure and pressure rectification technology, the method for separating tetrahydrofuran from esterification wastewater provided by the invention omits the pressure rectification process, thoroughly avoids the material circulating rectification process, remarkably improves the recovery efficiency of tetrahydrofuran, and saves energy consumption by more than 70%. Through the normal-pressure rectification and pervaporation dehydration treatment, the removal rate of water in the esterification wastewater can reach more than 99%, the loss of tetrahydrofuran in the dehydration process is avoided, the subsequent separation and recovery operation of tetrahydrofuran is facilitated, the energy consumption and the equipment operation pressure of the subsequent separation and recovery of tetrahydrofuran are further reduced, and the separation and recovery operation cost is remarkably reduced. The dehydrated materials are sequentially subjected to light component removal, hydrogenation reduction and heavy component removal treatment in sequence, so that the tetrahydrofuran and a compound which has extremely close physical and chemical properties to the tetrahydrofuran can be fully separated, the peroxide content in the separated tetrahydrofuran product is less than or equal to 0.005%, the tetrahydrofuran product does not contain unsaturated compounds, the quality of a polymer-grade tetrahydrofuran product is directly achieved, and the value and the application range of the separated tetrahydrofuran product are greatly improved.
Preferably, the atmospheric distillation process is completed in an atmospheric distillation tower; when the atmospheric distillation tower carries out the atmospheric distillation, the temperature of the top of the tower is 65-70 ℃, and the temperature of the bottom of the tower is 95-105 ℃.
The temperature of the normal pressure rectification is set, so that the purity of the obtained tetrahydrofuran crude product can be further improved, the loss of tetrahydrofuran in the normal pressure rectification process is effectively reduced, and the yield of the product is improved.
Preferably, the pervaporation dehydration process is completed by a pervaporation membrane device; when the pervaporation membrane device carries out pervaporation dehydration, the pressure of a permeation side is 10-50KPa, the pressure of a concentration side is 0.25-0.35MPa, and the temperature of pervaporation dehydration is 95-105 ℃.
The removal rate of the permeation water can be further improved by setting the permeation pressure and the temperature in the permeation gasification dehydration process, and the purity of the permeation water is improved, so that the obtained permeation water can be directly recycled.
Preferably, the light component removal process is completed in a light component removal tower; when the light component is removed by the light component removing tower, the temperature of the top of the tower is 60-80 ℃, the temperature of the bottom of the tower is 100-120 ℃, and the pressure is 0.1-0.5MPa.
The temperature and pressure in the light component removal tower can be set to fully remove light component materials in the tetrahydrofuran crude product and avoid the loss of tetrahydrofuran.
Preferably, the hydrogenation reduction process is completed in a hydrogenation reaction kettle; the temperature of the hydrogenation reaction kettle for hydrogenation reduction is 85-100 ℃, and the pressure is 0.2-0.5MPa.
The temperature and pressure of hydrogenation reduction can make unsaturated substances in the light component-removed material undergo full hydrogenation reduction reaction, and eliminate the influence of unsaturated substances in the material on the quality of tetrahydrofuran products.
Preferably, the hydrogenation catalyst in the hydrogenation reaction kettle is at least one of palladium carbon catalyst, nickel catalyst and rhodium catalyst.
Preferably, the heavy component removal process is completed in a heavy component removal tower, and when the heavy component removal is performed in the heavy component removal tower, the tower top temperature is 65-70 ℃, and the tower bottom temperature is 95-105 ℃.
The temperature in the de-heavy tower is set, so that heavy phase substances in the materials can be further reduced to enter tetrahydrofuran products, and the tetrahydrofuran products with high purity and high quality can be effectively separated.
Preferably, the esterification wastewater is generated in the production process of PBAT, and the esterification wastewater comprises: water, tetrahydrofuran, tributene-1-ol, 1, 4-butanediol, 2, 3-dihydrofuran, 2, 5-dihydrofuran, n-butanol and other common components which are inevitable for esterification wastewater.
Preferably, the mass content of water in the esterification wastewater is 50-60%, the mass content of tetrahydrofuran is 40-50%, and the mass content of tributylene-1 alcohol, 1, 4-butanediol, 2, 3-dihydrofuran, 2, 5-dihydrofuran and n-butanol is 1-5% in total.
The invention also provides a separation system used in the method for separating tetrahydrofuran from the esterification wastewater, wherein the separation system comprises a pretreatment dehydration unit, a light removal processing unit, a hydrogenation impurity removal unit and a heavy removal processing unit which are sequentially connected by virtue of pipelines;
the pretreatment dehydration unit comprises a normal pressure rectifying tower and a pervaporation membrane device; the middle part of the normal pressure rectifying tower is provided with an esterification wastewater feeding hole, the top of the tower is provided with a tetrahydrofuran gas phase outlet and a first condenser communicated with the gas phase outlet, the bottom of the tower is communicated with a first reboiler, and the bottom of the tower is provided with a liquid phase outlet; the tetrahydrofuran crude product condensed from the tower top is communicated with an inlet of the pervaporation membrane device through a pipeline, and the pervaporation membrane device is used for dehydrating the tetrahydrofuran crude product;
the light component removal treatment unit comprises a light component removal tower communicated with a tetrahydrofuran crude product outlet of the pervaporation membrane device; the top of the light component removing tower is provided with a light phase outlet for discharging gasified light phase substances, and the bottom of the light component removing tower is provided with a second reboiler and a discharge hole for leading out light component removing materials;
the hydrogenation impurity removal unit comprises a hydrogenation reaction kettle communicated with a discharge hole of the lightness-removing treatment unit;
the de-heavy treatment unit comprises a de-heavy tower communicated with a discharge hole of the hydrogenation reaction kettle; the top of the de-heavy tower is provided with a gas phase outlet, a third condenser and a tetrahydrofuran storage tank which are matched with the gas phase outlet, and the bottom of the de-heavy tower is provided with a third reboiler and a liquid phase outlet.
The separation system used by the method for separating tetrahydrofuran from esterification wastewater provided by the invention is simple to operate, small in equipment floor area and low in cost, and the separation and recovery efficiency of high-quality tetrahydrofuran is obviously improved.
Preferably, a tetrahydrofuran crude product condensate collecting tank is arranged on a communicating pipeline between the pervaporation membrane device and the first condenser, and the tetrahydrofuran crude product condensate collecting tank is further communicated with the top of the atmospheric pressure rectifying tower through a reflux pipeline.
The arrangement of the tetrahydrofuran crude product condensate collecting tank and the backflow pipeline communicated with the top of the atmospheric rectification tower on the tetrahydrofuran crude product condensate collecting tank can control the flow of the tetrahydrofuran crude product condensate entering the pervaporation membrane device on one hand, and can control the temperature of the flow of the tetrahydrofuran crude product reflux entering the top of the atmospheric rectification tower on the other hand, so that the purity of tetrahydrofuran in the tetrahydrofuran crude product is further ensured.
Preferably, the rear side of the membrane of the pervaporation membrane device is connected with a fourth condenser for condensing the permeated water vapor, and the concentrate outlet of the pervaporation membrane device is communicated with the lightness-removing column through a fifth condenser.
Preferably, a light phase outlet at the top of the light component removal tower is communicated with a light component storage tank through a second condenser, and the bottom of the light component storage tank is communicated with the top of the light component removal tower through a reflux pipeline.
The arrangement of the light component storage tank and the reflux pipeline which is arranged on the light component storage tank and communicated with the top of the light component removal tower can control the temperature at the top of the light component removal tower by controlling the flow of the light component condensed in the light component storage tank to flow back to the top of the light component removal tower, thereby ensuring the full removal of the light component and avoiding the gasification and discharge of tetrahydrofuran.
Preferably, the tetrahydrofuran storage tank is further provided with a reflux line communicated with the top of the de-heavy tower.
The arrangement of the reflux pipeline communicated with the top of the de-heavy tower on the tetrahydrofuran storage tank can control the temperature of the top of the de-heavy tower by controlling the flow of the condensed tetrahydrofuran in the tetrahydrofuran storage tank to flow into the top of the de-heavy tower, so that the full gasification and separation of the tetrahydrofuran are ensured, and the gasification and discharge of heavy components relative to the tetrahydrofuran are further avoided.
Drawings
FIG. 1 is a schematic view of the constitution of a separation system used in the process for separating tetrahydrofuran from esterification wastewater in example 1 of the present invention,
the system comprises a pretreatment dehydration unit, 101, an atmospheric distillation tower, 1011, an esterification wastewater feeding hole, 102, a first reboiler, 103, a first condenser, 104, a tetrahydrofuran crude product condensate collecting tank, 105, a pervaporation membrane device, 106, a fourth condenser, 107, a fifth condenser, 2, a light component removal processing unit, 201, a light component removal tower, 202, a second reboiler, 203, a second condenser, 204, a light component storage tank, 3, a hydrogenation impurity removal unit, 301, a hydrogenation reaction kettle, 4, a heavy component removal processing unit, 401, a heavy component removal tower, 402, a third reboiler, 403, a third condenser, 404 and a tetrahydrofuran storage tank.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
A separation system used in a method for separating tetrahydrofuran from esterification wastewater comprises a pretreatment dehydration unit 1, a light component removal processing unit 2, a hydrogenation impurity removal unit 3 and a heavy component removal processing unit 4 which are sequentially connected by virtue of pipelines;
the pretreatment dehydration unit 1 comprises an atmospheric distillation tower 101 and a pervaporation membrane device 105; the middle part of the atmospheric distillation tower 101 is provided with an esterification wastewater feed inlet 1011, the top of the tower is provided with a tetrahydrofuran gas phase outlet and a first condenser 103 communicated with the gas phase outlet, the bottom of the tower is communicated with a first reboiler 102, and the bottom of the tower is provided with a liquid phase outlet; the tetrahydrofuran crude product condensed from the tower top is communicated with the inlet of the pervaporation membrane device through a pipeline, and the pervaporation membrane device 105 is used for dehydrating the tetrahydrofuran crude product; a tetrahydrofuran crude product condensate collecting tank 104 is arranged on a communicating pipeline between the pervaporation membrane device 105 and the first condenser 103, and the tetrahydrofuran crude product condensate collecting tank 104 is also communicated with the top of the atmospheric distillation tower 101 through a reflux pipeline; a fourth condenser 106 for condensing permeation water vapor is connected to the rear side of the membrane of the pervaporation membrane device 105, and the concentrate outlet of the pervaporation membrane device 105 is communicated with the lightness-removing column 201 through a fifth condenser 107;
the light component removal treatment unit 2 comprises a light component removal tower 201 communicated with a tetrahydrofuran crude product outlet of the pervaporation membrane device 105; the top of the light component removing tower 201 is provided with a light phase outlet for discharging gasified light phase substances, and the bottom of the light component removing tower is provided with a second reboiler 202 and a discharge hole for discharging light component removing materials; a light phase outlet at the top of the light component removal tower 201 is communicated with a light component storage tank 204 through a second condenser 203, and the bottom of the light component storage tank 204 is communicated with the top of the light component removal tower 201 through a reflux pipeline;
the hydrogenation impurity removal unit 3 comprises a hydrogenation reaction kettle 301 communicated with a discharge hole of the light component removal processing unit 2;
the de-heavy treatment unit 4 comprises a de-heavy tower 401 communicated with a discharge hole of the hydrogenation reaction kettle 301; a gas phase outlet, a third condenser 403 and a tetrahydrofuran storage tank 404 which are matched with the gas phase outlet are arranged at the top of the de-heavy tower 401, and a third reboiler 402 and a liquid phase outlet are arranged at the bottom of the de-heavy tower; and a reflux line communicated with the top of the de-heavy tower 401 is also arranged on the tetrahydrofuran storage tank 404.
The method for recovering tetrahydrofuran from esterification wastewater (the mass content of water is 52 percent, the mass content of tetrahydrofuran is 45 percent, and the mass content of tributylene-1 alcohol, 1, 4-butanediol, 2, 3-dihydrofuran, 2, 5-dihydrofuran and n-butyl alcohol is 2.7 percent in total) generated in the PBAT production process by utilizing the separation system comprises the following specific process steps:
a. and (3) normal pressure rectification: feeding esterification wastewater generated in the PBAT production process into an atmospheric rectification tower 101 through an esterification wastewater feed inlet 1011, respectively controlling the temperature of a tower kettle of the atmospheric rectification tower 101 to be kept between 95 and 105 ℃ and the temperature of a tower top to be kept between 65 and 70 ℃ by controlling the flow rate of materials in a first reboiler 102 and a tetrahydrofuran crude product condensate collecting tank 104 which flow back to the atmospheric rectification tower 101, feeding a gas-phase tetrahydrofuran crude product obtained by rectification into a first condenser 103 through a tetrahydrofuran gas-phase outlet of the atmospheric rectification tower 101, and feeding the tetrahydrofuran crude product condensed into a liquid state by the first condenser 103 into the tetrahydrofuran crude product condensate collecting tank 104;
b. and (3) pervaporation dehydration: the tetrahydrofuran crude product in the tetrahydrofuran crude product condensate collecting tank 104 enters the pervaporation membrane device 105 from a feed inlet of the pervaporation membrane device 105, the pressure of the permeation side of the pervaporation membrane device is controlled to be 20KPa, the pressure of the concentration side is controlled to be 0.3MPa, and the temperature of pervaporation dehydration is 100 ℃; obtaining a dehydrated tetrahydrofuran crude product at the concentration side of the pervaporation membrane device 105, obtaining permeated water at the permeation side, condensing the permeated water into liquid water for recycling after flowing out from a permeated water outlet through a fourth condenser 106, and discharging the obtained dehydrated tetrahydrofuran crude product from a concentrated product outlet of the pervaporation membrane device;
c. removing light components: the discharged crude dehydrated tetrahydrofuran enters a light component removal tower 201, the tower kettle temperature of the light component removal tower 201 is controlled to be kept between 100 and 120 ℃ respectively by controlling the flow rate of materials in a second reboiler 202 and a light component storage tank 204 which flow back to the light component removal tower 201, the tower top temperature is kept between 60 and 80 ℃, and the pressure in the light component removal tower 201 is controlled to be 0.1 to 0.5MPa; light component materials generated in the light component removal tower 201 are discharged from a light phase outlet of the light component removal tower 201, condensed by a second condenser 203 and then enter a light component storage tank 204, and light component removal materials generated at the bottom of the tower are discharged from a discharge hole of the light component removal tower 201;
d. hydrogenation reduction: the light component removal material discharged from a discharge port of the light component removal tower 201 enters a hydrogenation reaction kettle 301 for hydrogenation reduction, a palladium-carbon catalyst is added into the hydrogenation reaction kettle 301, under the condition of introducing hydrogen, the temperature in the hydrogenation reaction kettle 301 is controlled to be 95 ℃ and the pressure is controlled to be 0.4MPa, and hydrogenation reduction material is obtained in the reaction kettle through hydrogenation reduction reaction and is discharged from a discharge port of the hydrogenation reaction kettle 301;
e. heavy component removal: feeding the hydrogenation reduction material discharged from a discharge port of the hydrogenation reactor 301 into a de-weighting tower 401, controlling the tower kettle temperature of the de-weighting tower 401 to be kept between 95 ℃ and 105 ℃ and the tower top temperature to be kept between 65 ℃ and 70 ℃ respectively by controlling the flow rate of the material in a third reboiler 402 and a tetrahydrofuran storage tank 404 which flows back to the de-weighting tower 401, feeding the obtained gas-phase tetrahydrofuran into a third condenser 403 through a gas-phase outlet of the de-weighting tower 401, and feeding the tetrahydrofuran product condensed into liquid by the third condenser 403 into the tetrahydrofuran storage tank 404 to complete the process of recovering and separating tetrahydrofuran from the esterification wastewater.
The detection shows that the tetrahydrofuran product obtained by recovery completely reaches the quality of polymerization-grade tetrahydrofuran, the mass fraction of tetrahydrofuran in the tetrahydrofuran product is 99.96%, the yield is 96.8%, the water content is 0.005%, the peroxide content is 0.0005%, and the tetrahydrofuran product does not contain unsaturated compounds.
Example 2
A method for recovering tetrahydrofuran from esterification wastewater (the mass content of water is 50%, the mass content of tetrahydrofuran is 48%, and the mass content of tributylene-1 alcohol, 1, 4-butanediol, 2, 3-dihydrofuran, 2, 5-dihydrofuran and n-butanol is 1.8% in total) generated in the production process of PBAT by using the separation system in the embodiment 1, which comprises the following specific process steps:
a. and (3) normal pressure rectification: feeding esterification wastewater generated in the PBAT production process into an atmospheric rectification tower 101 through an esterification wastewater feed inlet 1011, respectively controlling the temperature of a tower kettle of the atmospheric rectification tower 101 to be kept between 95 and 105 ℃ and the temperature of a tower top to be kept between 65 and 70 ℃ by controlling the flow rate of materials in a first reboiler 102 and a tetrahydrofuran crude product condensate collecting tank 104 which flow back to the atmospheric rectification tower 101, feeding a gas-phase tetrahydrofuran crude product obtained by rectification into a first condenser 103 through a tetrahydrofuran gas-phase outlet of the atmospheric rectification tower 101, and feeding the tetrahydrofuran crude product condensed into a liquid state by the first condenser 103 into the tetrahydrofuran crude product condensate collecting tank 104;
b. and (3) pervaporation dehydration: the tetrahydrofuran crude product in the tetrahydrofuran crude product condensate collecting tank 104 enters the pervaporation membrane device 105 from a feed inlet of the pervaporation membrane device 105, the pressure of the permeation side of the pervaporation membrane device is controlled to be 10KPa, the pressure of the concentration side of the pervaporation membrane device is controlled to be 0.25MPa, and the temperature of pervaporation dehydration is 95 ℃; obtaining a dehydrated tetrahydrofuran crude product at the concentration side of the pervaporation membrane device 105, obtaining permeated water at the permeation side, condensing the permeated water into liquid water for recycling after flowing out from a permeated water outlet through a fourth condenser 106, and discharging the obtained dehydrated tetrahydrofuran crude product from a concentrated product outlet of the pervaporation membrane device;
c. removing light components: the discharged crude dehydrated tetrahydrofuran enters a lightness-removing column 201, the temperature of the column bottom of the lightness-removing column 201 is controlled to be between 100 and 120 ℃ by controlling the flow rate of the materials in a second reboiler 202 and a light component storage tank 204 flowing back to the lightness-removing column 201, the temperature of the column top is controlled to be between 60 and 80 ℃, and the pressure in the lightness-removing column 201 is controlled to be between 0.1 and 0.5MPa; light component materials generated in the light component removal tower 201 are discharged from a light phase outlet of the light component removal tower 201, condensed by a second condenser 203 and enter a light component storage tank 204, and light component removal materials generated at the bottom of the tower are discharged from a discharge hole of the light component removal tower 201;
d. hydrogenation reduction: the light component removal material discharged from a discharge port of the light component removal tower 201 enters a hydrogenation reaction kettle 301 for hydrogenation reduction, a palladium-carbon catalyst is added into the hydrogenation reaction kettle 301, under the condition of introducing hydrogen, the temperature in the hydrogenation reaction kettle 301 is controlled to be 85 ℃ and the pressure is controlled to be 0.2MPa, and hydrogenation reduction material is obtained in the reaction kettle through hydrogenation reduction reaction and is discharged from a discharge port of the hydrogenation reaction kettle 301;
e. heavy component removal: feeding the hydrogenation reduction material discharged from a discharge port of the hydrogenation reactor 301 into a de-weighting tower 401, controlling the tower kettle temperature of the de-weighting tower 401 to be kept between 95 ℃ and 105 ℃ and the tower top temperature to be kept between 65 ℃ and 70 ℃ respectively by controlling the flow rate of the material in a third reboiler 402 and a tetrahydrofuran storage tank 404 which flows back to the de-weighting tower 401, feeding the obtained gas-phase tetrahydrofuran into a third condenser 403 through a gas-phase outlet of the de-weighting tower 401, and feeding the tetrahydrofuran product condensed into liquid by the third condenser 403 into the tetrahydrofuran storage tank 404 to complete the process of recovering and separating tetrahydrofuran from the esterification wastewater.
Detection shows that the recovered tetrahydrofuran product completely reaches the quality of polymerization-grade tetrahydrofuran, and the tetrahydrofuran product has the mass fraction of 99.96%, the yield of 95.9%, the water content of 0.0042%, the peroxide content of 0.0004% and no unsaturated compounds.
Example 3
A method for recovering tetrahydrofuran from esterification wastewater (the mass content of water is 55%, the mass content of tetrahydrofuran is 40%, and the mass content of tributylene-1 alcohol, 1, 4-butanediol, 2, 3-dihydrofuran, 2, 5-dihydrofuran and n-butanol totaled 4.6%) generated in a PBAT production process by using the separation system in the embodiment 1 comprises the following specific process steps:
a. and (3) normal pressure rectification: feeding esterification wastewater generated in the PBAT production process into an atmospheric rectification tower 101 through an esterification wastewater feed port 1011, controlling the tower kettle temperature of the atmospheric rectification tower 101 to be kept between 95 and 105 ℃ by controlling the flow rate of materials in a first reboiler 102 and a tetrahydrofuran crude product condensate collecting tank 104 which flow back to the atmospheric rectification tower 101, keeping the tower top temperature between 65 and 70 ℃, feeding a gas-phase tetrahydrofuran crude product obtained by rectification into a first condenser 103 through a tetrahydrofuran gas-phase outlet of the atmospheric rectification tower 101, and feeding the tetrahydrofuran crude product which is condensed into a liquid state by the first condenser 103 into the tetrahydrofuran crude product condensate collecting tank 104;
b. and (3) pervaporation dehydration: the tetrahydrofuran crude product in the tetrahydrofuran crude product condensate collecting tank 104 enters the pervaporation membrane device 105 from a feed inlet of the pervaporation membrane device 105, the pressure of the permeation side of the pervaporation membrane device is controlled to be 50KPa, the pressure of the concentration side is controlled to be 0.35MPa, and the temperature of pervaporation dehydration is controlled to be 105 ℃; obtaining a dehydrated tetrahydrofuran crude product at the concentration side of the pervaporation membrane device 105, obtaining permeated water at the permeation side, condensing the permeated water into liquid water for recycling through a fourth condenser 106 after the permeated water flows out from a permeated water outlet, and discharging the obtained dehydrated tetrahydrofuran crude product from a concentrated product outlet of the pervaporation membrane system;
c. removing light components: the discharged crude dehydrated tetrahydrofuran enters a lightness-removing column 201, the temperature of the column bottom of the lightness-removing column 201 is controlled to be between 100 and 120 ℃ by controlling the flow rate of the materials in a second reboiler 202 and a light component storage tank 204 flowing back to the lightness-removing column 201, the temperature of the column top is controlled to be between 60 and 80 ℃, and the pressure in the lightness-removing column 201 is controlled to be between 0.1 and 0.5MPa; light component materials generated in the light component removal tower 201 are discharged from a light phase outlet of the light component removal tower 201, condensed by a second condenser 203 and then enter a light component storage tank 204, and light component removal materials generated at the bottom of the tower are discharged from a discharge hole of the light component removal tower 201;
d. hydrogenation reduction: the light component removal material discharged from a discharge port of the light component removal tower 201 enters a hydrogenation reaction kettle 301 for hydrogenation reduction, a palladium-carbon catalyst is added into the hydrogenation reaction kettle 301, under the condition that hydrogen is introduced, the temperature in the hydrogenation reaction kettle 301 is controlled to be 100 ℃ and the pressure is controlled to be 0.5MPa, and through hydrogenation reduction reaction, a hydrogenation reduction material is obtained in the reaction kettle and is discharged from the discharge port of the hydrogenation reaction kettle 301;
e. removing heavy components: feeding the hydrogenation reduction material discharged from a discharge port of the hydrogenation reactor 301 into a de-heavy tower 401, respectively controlling the tower kettle temperature of the de-heavy tower 401 to be kept between 95 and 105 ℃ and the tower top temperature to be kept between 65 and 70 ℃ by controlling the flow rate of the material in a third reboiler 402 and a tetrahydrofuran storage tank 404 which flows back to the de-heavy tower 401, feeding the obtained gas-phase tetrahydrofuran into a third condenser 403 through a gas-phase outlet of the de-heavy tower 401, condensing the gas-phase tetrahydrofuran into a liquid tetrahydrofuran product through the third condenser 403, and feeding the tetrahydrofuran product into the tetrahydrofuran storage tank 404 to complete the process of recovering and separating tetrahydrofuran from the esterification wastewater.
Detection shows that the tetrahydrofuran product obtained by recovery completely reaches the quality of polymer-grade tetrahydrofuran, the mass fraction of tetrahydrofuran in the tetrahydrofuran product is 99.97%, the yield is 96.2%, the water content is 0.0047%, the peroxide content is 0.0004%, and unsaturated compounds are not contained.
Comparative example 1
The order of removing the light components and removing the heavy components in the example 1 is exchanged, that is, the treatment method of the esterification wastewater sequentially comprises normal pressure rectification, pervaporation dehydration, heavy component removal, hydrogenation reduction and light component removal treatment, and the equipment, parameters and other operation methods related to each treatment method are the same as those in the example 1, so that a tetrahydrofuran product is obtained.
The detection proves that the tetrahydrofuran product obtained by recycling can not reach the quality of polymer-grade tetrahydrofuran, the mass fraction of tetrahydrofuran in the tetrahydrofuran product is 99.93 percent, the yield is 94.2 percent, the water content is 0.008 percent, the peroxide content is 0.0005 percent, and the tetrahydrofuran product does not contain unsaturated compounds.
Comparative example 2
The pervaporation dehydration treatment process in the example 1 is performed after the heavy component removal treatment process, that is, the treatment method of the esterification wastewater sequentially comprises normal pressure rectification, light component removal, hydrogenation reduction, heavy component removal and pervaporation dehydration treatment, and the equipment, parameters and other operation methods related to each treatment method are the same as those in the example 1, so that a tetrahydrofuran product is obtained.
By adopting the method, more than 50% of feed liquid needs to be repeatedly pressurized and dehydrated when the light components are removed, so that the light component removal tower has larger equipment and higher energy consumption in the operation process, and the energy consumption is higher than that of the technical scheme in the embodiment 1 by more than 50%.
The detection shows that the recovered tetrahydrofuran product can not reach the quality of polymer-grade tetrahydrofuran, the mass fraction of tetrahydrofuran in the tetrahydrofuran product is 99.85%, the yield is 93.8%, the water content is 0.005%, the peroxide content is 0.0005%, and the tetrahydrofuran product does not contain unsaturated compounds.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (3)
1. A method for separating tetrahydrofuran from esterification wastewater is characterized in that: sequentially carrying out normal-pressure rectification, pervaporation dehydration, light component removal, hydrogenation reduction and heavy component removal on the esterification wastewater to obtain a tetrahydrofuran product;
the esterification wastewater is generated in the PBAT production process, and comprises the following steps: water, tetrahydrofuran, tributene-1-ol, 1, 4-butanediol, 2, 3-dihydrofuran, 2, 5-dihydrofuran, n-butanol and other common components which are inevitable for esterification wastewater;
the atmospheric rectification process is completed in an atmospheric rectification tower; when the atmospheric distillation tower is used for the atmospheric distillation, the tower top temperature is 65-70 ℃, and the tower kettle temperature is 95-105 ℃;
the pervaporation dehydration process is completed by a pervaporation membrane device; when the pervaporation membrane device carries out pervaporation dehydration, the pressure of a permeation side is 10-50KPa, the pressure of a concentration side is 0.25-0.35MPa, and the temperature of pervaporation dehydration is 95-105 ℃;
the light component removing process is completed in a light component removing tower; when the light component is removed by the light component removing tower, the temperature of the top of the tower is 60-80 ℃, the temperature of the bottom of the tower is 100-120 ℃, and the pressure is 0.1-0.5MPa;
the hydrogenation reduction process is completed in a hydrogenation reaction kettle; the temperature of the hydrogenation reaction kettle for hydrogenation reduction is 85-100 ℃, and the pressure is 0.2-0.5MPa;
the heavy component removal process is completed in a heavy component removal tower, and when the heavy component removal is carried out in the heavy component removal tower, the tower top temperature is 65-70 ℃, and the tower kettle temperature is 95-105 ℃;
the method for separating tetrahydrofuran from esterification wastewater uses the following system:
the separation system comprises a pretreatment dehydration unit, a light component removal processing unit, a hydrogenation impurity removal unit and a heavy component removal processing unit which are sequentially connected by virtue of pipelines;
the pretreatment dehydration unit comprises a normal pressure rectifying tower and a pervaporation membrane device; the middle part of the normal pressure rectifying tower is provided with an esterification wastewater feeding hole, the top of the tower is provided with a tetrahydrofuran gas phase outlet and a first condenser communicated with the gas phase outlet, the bottom of the tower is communicated with a first reboiler, and the bottom of the tower is provided with a liquid phase outlet; the tetrahydrofuran crude product condensed from the tower top is communicated with an inlet of the pervaporation membrane device through a pipeline, and the pervaporation membrane device is used for dehydrating the tetrahydrofuran crude product;
the light component removal treatment unit comprises a light component removal tower communicated with a tetrahydrofuran crude product outlet of the pervaporation membrane device; the top of the light component removal tower is provided with a light phase outlet for discharging gasified light phase substances, and the bottom of the light component removal tower is provided with a second reboiler and a discharge hole for discharging light component removal materials;
the hydrogenation impurity removal unit comprises a hydrogenation reaction kettle communicated with a discharge hole of the lightness-removing treatment unit;
the de-weighting treatment unit comprises a de-weighting tower communicated with a discharge hole of the hydrogenation reaction kettle; the top of the de-heavy tower is provided with a gas phase outlet, a third condenser and a tetrahydrofuran storage tank which are matched with the gas phase outlet, and the bottom of the de-heavy tower is provided with a third reboiler and a liquid phase outlet.
2. The process for separating tetrahydrofuran from esterification wastewater according to claim 1, wherein: the hydrogenation catalyst in the hydrogenation reaction kettle is at least one of palladium carbon catalyst, nickel catalyst and rhodium catalyst.
3. The process for separating tetrahydrofuran from esterification wastewater according to claim 1, wherein: the esterification wastewater contains water 50-60 wt%, tetrahydrofuran 40-50 wt%, and tributylene-1 alcohol, 1, 4-butanediol, 2, 3-dihydrofuran, 2, 5-dihydrofuran and n-butanol 1-5 wt%.
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