CN113979840A - Three-tower differential pressure thermal coupling rectification method for separating methanol, dimethyl carbonate and phenol - Google Patents

Three-tower differential pressure thermal coupling rectification method for separating methanol, dimethyl carbonate and phenol Download PDF

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CN113979840A
CN113979840A CN202111432554.5A CN202111432554A CN113979840A CN 113979840 A CN113979840 A CN 113979840A CN 202111432554 A CN202111432554 A CN 202111432554A CN 113979840 A CN113979840 A CN 113979840A
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tower
dmc
methanol
stream
refining
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CN113979840B (en
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刘玉龙
刘果
周齐领
陈予
郑兰
唐卫新
梁建平
李强
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China Chengda Engineering Co Ltd
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China Chengda Engineering Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
    • C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
    • C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
    • C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
    • C07C37/70—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment
    • C07C37/74—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment by distillation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C68/00—Preparation of esters of carbonic or haloformic acids
    • C07C68/08—Purification; Separation; Stabilisation
    • 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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  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The invention belongs to the technical field of chemical industry, and particularly relates to a three-tower differential pressure thermal coupling rectification method for separating methanol, dimethyl carbonate and phenol. The technical scheme is as follows: a three-tower differential pressure thermal coupling rectification method for separating methanol, dimethyl carbonate and phenol comprises the following steps: s1: introducing a stream from the diphenyl carbonate reaction column into the middle lower part of the DMC rectification column; s2: condensing the gas stream at the top of the DMC rectifying tower and introducing the gas stream into the middle of the methanol refining tower; s3: sending the top stream of the methanol rectifying tower back to the middle upper part of the DMC rectifying tower; s4: a methanol product is extracted from the bottom of the methanol refining tower; s5: introducing the bottom flow strand of the DMC rectification tower into a DMC refining tower; s6: recovering the DMC product from the top of the DMC refining column; s7: phenol product is withdrawn from the bottom of the DMC purification column. The invention provides a three-tower differential pressure thermal coupling rectification method capable of effectively separating and refining methanol, dimethyl carbonate and phenol in a diphenyl carbonate plant stream.

Description

Three-tower differential pressure thermal coupling rectification method for separating methanol, dimethyl carbonate and phenol
Technical Field
The invention belongs to the technical field of chemical industry, and particularly relates to a three-tower differential pressure thermal coupling rectification method for separating methanol, dimethyl carbonate and phenol.
Background
Methanol is not only an important chemical raw material, but also an energy source and vehicle fuel with excellent performance, and can replace methyl tert-butyl ether to be used as a gasoline additive. Besides, the method can also prepare olefin, thereby solving the problem of resource shortage at present.
In the production process of diphenyl carbonate (DPC), a part of methanol is produced as a byproduct, the purity of the product is only 93 wt%, and the product cannot be sold as a commodity; however, methanol and dimethyl carbonate (DMC) as a raw material form a binary azeotropic system, if a high-grade methanol product is to be obtained, the separation is difficult by using a traditional rectification method, and the energy consumption is very high because special rectification is selected for the separation.
Disclosure of Invention
In order to solve the above problems in the prior art, an object of the present invention is to provide a three-tower differential pressure thermal coupling rectification method capable of effectively separating and refining methanol, dimethyl carbonate and phenol in a diphenyl carbonate plant stream.
The technical scheme adopted by the invention is as follows:
a three-tower differential pressure thermal coupling rectification method for separating methanol, dimethyl carbonate and phenol comprises the following steps:
s1: introducing a stream from the diphenyl carbonate reaction column into the middle lower part of the DMC rectification column;
s2: condensing the gas stream at the top of the DMC rectifying tower and introducing the gas stream into the middle of the methanol refining tower;
s3: sending the top stream of the methanol rectifying tower back to the middle upper part of the DMC rectifying tower;
s4: a methanol product is extracted from the bottom of the methanol refining tower;
s5: introducing the bottom flow strand of the DMC rectification tower into a DMC refining tower;
s6: recovering the DMC product from the top of the DMC refining column;
s7: phenol product is withdrawn from the bottom of the DMC purification column.
The DMC rectifying tower can separate a stream containing methanol from the top, the stream condensed by the condensing pipeline is fully separated in the methanol refining tower, and a methanol product is separated from the methanol refining tower. And (3) delivering the stream at the top of the methanol rectifying tower to the top of the DMC rectifying tower, so that after the stream is separated by the DMC rectifying tower and the methanol rectifying tower, the purity of the methanol extracted from the methanol rectifying tower is higher, and DMC and phenol in the stream at the top of the DMC rectifying tower can be fully returned to the DMC rectifying tower. And sending the mixed stream containing DMC and phenol extracted from the DMC rectifying tower to a DMC refining tower, wherein the DMC refining tower can fully separate DMC and phenol, thereby respectively obtaining DMC products and phenol products with higher purity.
As a preferable embodiment of the present invention, in step S2, when condensing the gas stream at the top of the DMC rectification column, the gas stream is introduced into the tube side of the reboiler at the bottom of the methanol refining column. And the stream extracted from the top of the DMC rectifying tower passes through the tube pass of a reboiler at the bottom of the methanol refining tower and is condensed, and the heat is absorbed by part of the stream extracted from the bottom of the methanol refining tower, so that the heat is effectively utilized.
As a preferred embodiment of the present invention, in step S2, the stream passing through the methanol refining tower bottom reboiler is passed into the DMC rectification tower top first condenser to be condensed again. And condensing the stream condensed by the reboiler at the bottom of the methanol refining tower by the first condenser at the top of the DMC rectification tower, and sending the stream into the middle part of the methanol refining tower after full condensation.
As a preferred embodiment of the invention, in step S2, the partial stream which has passed through the methanol refining bottoms reboiler and the DMC rectification overhead first condenser is returned to the top of the DMC rectification column. Part of the stream condensed by the reboiler at the bottom of the methanol refining tower and the first condenser at the top of the DMC rectifying tower returns to the top of the DMC rectifying tower, so that DMC and phenol in the stream extracted from the top of the DMC rectifying tower can be fully sent back to the DMC rectifying tower.
As a preferable scheme of the present invention, in step S4, a part of the stream at the bottom of the methanol refining column passes through the shell side of the reboiler at the bottom of the methanol refining column and then is introduced into the bottom of the methanol refining column, and the other part of the stream is extracted. And part of the stream extracted from the bottom of the methanol refining tower is reboiled by a reboiler at the bottom of the methanol refining tower and then is sent back to the bottom of the methanol refining tower, so that components except methanol in the extracted stream are fully evaporated, and the purity of the extracted methanol product is improved. The heat source is provided for the reboiler at the bottom of the methanol refining tower by utilizing the gas phase condensation latent heat at the top of the DMC rectifying tower, the reutilization of the vaporization latent heat is realized, and the steam required by the reboiler at the bottom of the methanol refining tower is further saved.
As a preferable embodiment of the present invention, in step S4, during the first startup, a part of the stream at the bottom of the methanol refining column is introduced into the bottom of the methanol refining column through the startup reboiler, and the other part of the stream is extracted. When the methanol refining tower is started for the first time, the stream at the bottom of the methanol refining tower is sent to the bottom of the methanol refining tower after passing through the start reboiler, so that the condition that no stream flows into the tube pass of the reboiler at the bottom of the methanol refining tower in the initial period is avoided.
As a preferable scheme of the present invention, in step S3, the gas stream at the top of the methanol refining tower is introduced into the second condenser at the top of the methanol refining tower, part of the stream after total condensation is sent back to the top of the methanol refining tower, and the other part of the stream is returned to the middle upper part of the DMC rectifying tower. And condensing the stream on the reflux pipeline through a second condenser at the top of the methanol refining tower, and sending part of the stream back to the top of the methanol refining tower, so that the methanol in the extracted stream is reduced, and the methanol can be fully settled in the methanol refining tower.
As a preferable scheme of the invention, in step S5, part of the stream at the bottom of the DMC rectification column is passed through a reboiler at the bottom of the DMC rectification column and then introduced into the bottom of the DMC rectification column, and the recovered stream is introduced into the middle of the DMC rectification column. And the reboiler at the bottom of the DMC rectifying tower can ensure that part of stream extracted from the bottom of the DMC rectifying tower is fully reboiled and then sent back to the DMC rectifying tower, so that the methanol in the stream can be fully evaporated, and the content of the methanol in the stream sent to the middle part of the DMC rectifying tower is reduced.
As a preferable scheme of the present invention, in step S6, the gas stream at the top of the DMC refining column is introduced into the DMC refining column top condenser, part of the stream of the fully condensed stream is sent back to the top of the DMC refining column, and the other part of the stream is withdrawn. The DMC refining tower top condenser can fully condense the stream extracted from the top of the DMC refining tower, and the partially condensed stream is sent back to the top of the DMC refining tower, so that phenol in the stream can be fully settled, and the purity of the extracted DMC product is improved.
In a preferred embodiment of the present invention, in step S7, a part of the stream at the bottom of the DMC refining column is passed through a reboiler at the bottom of the DMC refining column and then introduced into the bottom of the DMC refining column, and another part of the stream is recovered. And the reboiler at the bottom of the DMC refining tower can ensure that the stream produced at the bottom of the DMC refining tower is fully reboiled and then sent back to the bottom of the DMC refining tower, so that phenol in the stream produced at the bottom of the DMC refining tower is fully evaporated, and the purity of the produced DMC product is improved.
The invention has the beneficial effects that:
the DMC rectifying tower can separate a stream containing methanol from the top, the stream condensed by the condensing pipeline is fully separated in the methanol refining tower, and a methanol product is separated from the methanol refining tower. And (3) delivering the stream at the top of the methanol rectifying tower to the top of the DMC rectifying tower, so that after the stream is separated by the DMC rectifying tower and the methanol rectifying tower, the purity of the methanol extracted from the methanol rectifying tower is higher, and DMC and phenol in the stream at the top of the DMC rectifying tower can be fully returned to the DMC rectifying tower. And sending the mixed stream containing DMC and phenol extracted from the DMC rectifying tower to a DMC refining tower, wherein the DMC refining tower can fully separate DMC and phenol, thereby respectively obtaining DMC products and phenol products with higher purity.
Drawings
FIG. 1 is a flow chart of a method of the present invention;
fig. 2 is a schematic diagram of the structure of a system used in the present invention.
In the figure, a 1-DMC rectifying tower; 2-a condensation line; 3-a mixed stream line; 4-methanol refining column; 5-a return line; 6-methanol product line; 7-DMC purification column; 8-DMC product line; a 9-phenol product line; 11-feed line; 21-methanol refining tower bottom reboiler; 22-DMC rectification overhead first condenser; 23-a condensate return line; 31-mixed stream return line; a 32-DMC rectification column bottom reboiler; a second condenser at the top of the 51-methanol refining tower; 52-methanol return line; 61-methanol return line; 62-methanol initial return line; 63-start-up reboiler; 81-DMC refining overhead condenser; 82-DMC return line; 91-phenol return line; 92-DMC refining bottoms reboiler.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
As shown in fig. 1, the three-tower differential pressure thermal coupling rectification method for separating methanol, dimethyl carbonate and phenol of the present embodiment includes the following steps:
s1: introducing a stream from the diphenyl carbonate reaction column into the middle lower part of the DMC rectification column 1;
s2: condensing the gas stream at the top of the DMC rectifying tower 1 and introducing the gas stream into the middle of a methanol refining tower 4;
s3: the top stream of the methanol refining column 4 is sent back to the middle upper part of the DMC rectifying column 1;
s4: a methanol product is extracted from the bottom of the methanol refining tower 4;
s5: introducing the stream at the bottom of the DMC rectifying tower 1 into a DMC refining tower 7;
s6: extracting DMC product from the top of DMC refining tower 7;
s7: phenol product is withdrawn from the bottom of the DMC refining column 7.
The DMC rectifying tower 1 can separate a stream containing methanol from the top, the stream condensed by the condensing pipeline 2 is fully separated in the methanol refining tower 4, and a methanol product is separated from the methanol refining tower 4. The stream at the top of the methanol refining tower 4 is sent to the top of the DMC rectifying tower 1, so that after the stream is separated by the DMC rectifying tower 1 and the methanol refining tower 4, the purity of the methanol extracted from the methanol refining tower 4 is higher, and DMC and phenol in the stream at the top of the DMC rectifying tower 1 can be fully returned to the DMC rectifying tower 1. The mixed stream containing DMC and phenol extracted from the DMC rectifying tower 1 is sent to a DMC refining tower 7, and the DMC refining tower 7 can fully separate DMC and phenol, thereby obtaining DMC products and phenol products with higher purity respectively.
Specifically, in step S2, while condensing the gas stream at the top of the DMC rectification column 1, the gas stream is passed into the tube side of the methanol refining column bottom reboiler 21. And the stream extracted from the top of the DMC rectifying tower 1 passes through the tube pass of the reboiler 21 at the bottom of the methanol refining tower and is condensed, and the heat is absorbed by part of the stream extracted from the bottom of the methanol refining tower 4, so that the heat is effectively utilized.
The stream passing through the methanol refining tower bottom reboiler 21 is passed to the DMC rectification tower top first condenser 22 for re-condensation. And the stream condensed by the reboiler 21 at the bottom of the methanol refining tower is condensed by the first condenser 22 at the top of the DMC rectifying tower, and the stream is sent to the middle part of the methanol refining tower 4 after being condensed completely.
Part of the stream passing through the methanol refining bottoms reboiler 21 and the DMC rectification overhead first condenser 22 is sent back to the top of the DMC rectification column 1. Part of the stream condensed by the methanol refining tower bottom reboiler 21 and the DMC rectification tower top first condenser 22 returns to the top of the DMC rectification tower 1, so that DMC and phenol in the stream extracted from the top of the DMC rectification tower 1 can be fully returned to the DMC rectification tower 1.
Further, in step S4, a part of the stream at the bottom of the methanol refining column 4 passes through the shell side of the reboiler 21 at the bottom of the methanol refining column and then is introduced into the bottom of the methanol refining column 4, and another part of the stream is extracted. Part of the stream extracted from the bottom of the methanol refining tower 4 is reboiled by a reboiler 21 at the bottom of the methanol refining tower and then sent back to the bottom of the methanol refining tower 4, so that components except methanol in the extracted stream are fully evaporated, and the purity of the extracted methanol product is improved. The heat source is provided for the reboiler 21 at the bottom of the methanol refining tower by utilizing the gas phase condensation latent heat at the top of the DMC rectifying tower 1, the recycling of the vaporization latent heat is realized, and the steam required by the reboiler 21 at the bottom of the methanol refining tower is further saved.
During the first startup, part of the stream at the bottom of the methanol refining tower 4 passes through the startup reboiler 63 and enters the bottom of the methanol refining tower 4, and the other part of the stream is extracted. When the car is started for the first time, the stream at the bottom of the methanol refining tower 4 is sent to the bottom of the methanol refining tower 4 after passing through the car-starting reboiler 63, so that the condition that no stream flows into the tube pass of the methanol refining tower bottom reboiler 21 in the initial period is avoided.
Further, in step S3, the gas stream at the top of the methanol refining tower 4 is passed to the second condenser 51 at the top of the methanol refining tower, the totally condensed partial stream is sent back to the top of the methanol refining tower 4, and the other partial stream is returned to the middle upper part of the DMC rectification tower 1. After the stream on the reflux pipeline 5 is condensed by the second condenser 51 at the top of the methanol refining tower, part of the stream is sent back to the top of the methanol refining tower 4, so that the methanol in the extracted stream is reduced, and the methanol can be fully settled in the methanol refining tower 4.
Further, in step S5, part of the stream at the bottom of the DMC rectification column 1 is passed through the DMC rectification column bottom reboiler 32 and then introduced into the bottom of the DMC rectification column 1, and the extracted stream is introduced into the middle of the DMC refining column 7. The reboiler 32 at the bottom of the DMC rectifying tower can ensure that part of stream extracted from the bottom of the DMC rectifying tower 1 is fully reboiled and then sent back to the DMC rectifying tower 1, so that the methanol in the stream can be fully evaporated, and the content of the methanol in the stream sent to the middle part of the DMC rectifying tower 7 is reduced.
Further, in step S6, the gas stream at the top of the DMC refining column 7 is passed to the DMC refining overhead condenser 81, a part of the stream of the fully condensed stream is sent back to the top of the DMC refining column 7, and another part of the stream is taken out. The DMC refining tower top condenser 81 can fully condense the stream extracted from the tower top of the DMC refining tower 7, and the partially condensed stream is sent back to the tower top of the DMC refining tower 7, so that phenol in the stream can be fully settled, and the purity of the extracted DMC product is improved.
Further, in step S7, a part of the stream at the bottom of the DMC refining column 7 is passed through the DMC refining column bottom reboiler 92 and then introduced into the bottom of the DMC refining column 7, and another part of the stream is withdrawn. And the reboiler at the bottom of the DMC refining tower 7 can ensure that the stream extracted from the bottom of the DMC refining tower 7 is fully reboiled and then sent back to the bottom of the DMC refining tower 7, so that phenol in the stream extracted from the bottom of the DMC refining tower 7 is fully evaporated, and the purity of the extracted DMC product is improved.
As shown in fig. 2, the system used in the present invention:
the system comprises a DMC rectifying tower 1, wherein the middle lower part of the DMC rectifying tower 1 is connected with a raw material pipeline 11 for introducing streams from a diphenyl carbonate reaction tower, the top of the DMC rectifying tower 1 is connected with a condensation pipeline 2, and the bottom of the DMC rectifying tower 1 is connected with a mixed stream pipeline 3; the device also comprises a methanol refining tower 4, the other end of the condensation pipeline 2 is connected to the middle part of the methanol refining tower 4, a return pipeline 5 is connected between the top of the methanol refining tower 4 and the middle upper part of the DMC rectifying tower 1, and the bottom of the methanol refining tower 4 is connected with a methanol product pipeline 6; the device further comprises a DMC refining tower 7, the other end of the mixed stream pipeline 3 is connected to the middle of the DMC refining tower 7, the top of the DMC refining tower 7 is connected with a DMC product pipeline 8, and the bottom of the DMC refining tower 7 is connected with a phenol product pipeline 9.
The DMC rectifying tower 1 can separate a stream containing methanol from the top, the stream condensed by the condensing pipeline 2 is fully separated in the methanol refining tower 4, and a methanol product is separated from the methanol refining tower 4. The stream at the top of the methanol refining tower 4 is sent to the top of the DMC rectifying tower 1, so that after the stream is separated by the DMC rectifying tower 1 and the methanol refining tower 4, the purity of the methanol extracted from the methanol refining tower 4 is higher, and DMC and phenol in the stream at the top of the DMC rectifying tower 1 can be fully returned to the DMC rectifying tower 1. The mixed stream containing DMC and phenol extracted from the DMC rectifying tower 1 is sent to a DMC refining tower 7, and the DMC refining tower 7 can fully separate DMC and phenol, thereby obtaining DMC products and phenol products with higher purity respectively.
The condensation pipeline 2 is connected with a methanol refining tower bottom reboiler 21, and the condensation pipeline 2 is connected with the tube pass of the methanol refining tower bottom reboiler 21. The stream extracted from the top of the DMC rectification column 1 passes through the tube pass of the reboiler 21 at the bottom of the methanol refining column and is then condensed. The condensation pipeline 2 is also connected with a DMC rectification tower top first condenser 22. And the stream condensed by the reboiler 21 at the bottom of the methanol refining tower is condensed by the first condenser 22 at the top of the DMC rectifying tower, and the stream is sent to the middle part of the methanol refining tower 4 after being condensed completely. And one end of the condensation pipeline 2 close to the methanol refining tower 4 is also connected with a condensation return pipeline 23, and the other end of the condensation return pipeline 23 is connected to the top of the DMC rectification tower 1. Part of the stream condensed by the methanol refining tower bottom reboiler 21 and the DMC rectification tower top first condenser 22 returns to the top of the DMC rectification tower 1, so that DMC and phenol in the stream extracted from the top of the DMC rectification tower 1 can be fully returned to the DMC rectification tower 1.
The methanol product pipeline 6 is connected with a methanol return pipeline 61, the other end of the methanol return pipeline 61 is connected with the bottom of the methanol refining tower 4, and the methanol return pipeline 61 is connected with the shell side of a reboiler 21 at the bottom of the methanol refining tower. Part of the stream extracted from the bottom of the methanol refining tower 4 is reboiled by a reboiler 21 at the bottom of the methanol refining tower and then sent back to the bottom of the methanol refining tower 4, so that components except methanol in the extracted stream are fully evaporated, and the purity of the extracted methanol product is improved. The heat source is provided for the reboiler 21 at the bottom of the methanol refining tower by utilizing the gas phase condensation latent heat at the top of the DMC rectifying tower 1, the recycling of the vaporization latent heat is realized, and the steam required by the reboiler 21 at the bottom of the methanol refining tower is further saved.
The methanol product pipeline 6 is also connected with a methanol initial return pipeline 62, the other end of the methanol initial return pipeline 62 is connected with the bottom of the methanol refining tower 4, and the methanol initial return pipeline 62 is connected with a start reboiler 63. When the car is started for the first time, the stream at the bottom of the methanol refining tower 4 is sent to the bottom of the methanol refining tower 4 after passing through the car-starting reboiler 63, so that the condition that no stream flows into the tube pass of the methanol refining tower bottom reboiler 21 in the initial period is avoided.
The reflux pipeline 5 is connected with a methanol refining tower top second condenser 51, the reflux pipeline 5 positioned at the outlet side of the methanol refining tower top second condenser 51 is connected with a methanol return pipeline 52, and the other end of the methanol return pipeline 52 is connected with the top of the methanol refining tower 4. After the stream on the reflux pipeline 5 is condensed by the second condenser 51 at the top of the methanol refining tower, part of the stream is sent back to the top of the methanol refining tower 4, so that the methanol in the extracted stream is reduced, and the methanol can be fully settled in the methanol refining tower 4.
The mixed stream pipeline 3 is connected with a mixed stream return pipeline 31, the other end of the mixed stream return pipeline 31 is connected to the bottom of the DMC rectifying tower 1, and the mixed stream return pipeline 31 is connected with a bottom reboiler 32 of the DMC rectifying tower. The reboiler 32 at the bottom of the DMC rectifying tower can ensure that part of stream extracted from the bottom of the DMC rectifying tower 1 is fully reboiled and then sent back to the DMC rectifying tower 1, so that the methanol in the stream can be fully evaporated, and the content of the methanol in the stream sent to the middle part of the DMC rectifying tower 7 is reduced.
The DMC product pipeline 8 is connected with a DMC refining tower top condenser 81, the DMC product pipeline 8 positioned at the outlet side of the DMC refining tower top condenser 81 is connected with a DMC return pipeline 82, and the other end of the DMC return pipeline 82 is connected to the top of the DMC refining tower 7. The DMC refining tower top condenser 81 can fully condense the stream extracted from the tower top of the DMC refining tower 7, and the partially condensed stream is sent back to the tower top of the DMC refining tower 7, so that phenol in the stream can be fully settled, and the purity of the extracted DMC product is improved.
The phenol product pipeline 9 is connected with a phenol return pipeline 91, the other end of the phenol return pipeline 91 is connected to the bottom of the DMC refining tower 7, and the phenol return pipeline 91 is connected with a DMC refining tower bottom reboiler 92. The reboiler 92 at the bottom of the DMC refining tower can ensure that the stream extracted from the bottom of the DMC refining tower 7 is fully reboiled and then sent back to the bottom of the DMC refining tower 7, so that phenol in the stream extracted from the bottom of the DMC refining tower 7 is fully evaporated, and the purity of the extracted DMC product is improved.
The working process is as follows:
introducing the stream from the DPC reaction tower into the middle lower part of the DMC rectifying tower 1; and (3) feeding a gas stream (139.7 ℃) at the top of the DMC rectifying tower 1 into a reboiler 21 at the bottom of the methanol refining tower, feeding the condensed stream into a second condenser at the top of the DMC rectifying tower 1, refluxing the condensed stream to the top of the DMC rectifying tower 1, and feeding the other stream into the middle of the methanol refining tower 4 b. And the stream (202.2 ℃) at the bottom of the DMC rectifying tower 1 enters the bottom of the DMC rectifying tower 1 after passing through a reboiler 32 at the bottom of the DMC rectifying tower, and the extracted stream enters the middle part of a DMC refining tower 7. And a gas stream (67.7 ℃) at the top of the methanol refining tower 4 enters a condenser at the top of the methanol refining tower 4, a full-condensation rear split stream reflows to the top of the methanol refining tower 4, and the other part of the stream returns to the middle upper part of the DMC rectifying tower 1. The stream (70.6 ℃) at the bottom of the methanol refining tower 4 passes through a reboiler 21 at the bottom of the methanol refining tower and enters the bottom of the methanol refining tower 4, and the extracted stream is 99.96 wt% of methanol product. And when the automobile is started for the first time, the stream at the bottom of the methanol refining tower 4 enters the bottom of the methanol refining tower 4 after passing through the start reboiler 63. And a gas stream (69.5 ℃) at the top of the DMC refining tower 7 enters a DMC refining tower top condenser 81, a part of fully condensed stream reflows to the top of the DMC refining tower 7, and the other part of stream is 99.99 wt% of DMC product. And the stream (161 ℃) at the bottom of the DMC refining tower 7 enters the bottom of the DMC refining tower 7 after passing through a reboiler 92 at the bottom of the DMC refining tower, and the extracted stream is 99.99 wt% of phenol product.
The heat load at the top of the DMC rectifying tower 1 is matched with the heat load at the bottom of the methanol refining tower 4, and other heat exchange devices are not required to be started.
The operating pressure range of the DMC rectifying tower 1 is 0.8-1.2 MPaG, the operating pressure range of the methanol refining tower 4 is 0-0.3 MPaG, and the operating pressure range of the DMC refining tower 7 is-0.1 MPaG.
The feeding amount of methanol, DMC and phenol mixture was 10000kg/h, wherein the mass fraction of methanol was 3.0 wt%, and the mass fraction of DMC was 74.0 wt%. The optimum operating pressure for DMC column 1 was 0.98MPaG, the top temperature 139.7 ℃ and the bottom temperature 202.2 ℃. The optimum operating pressure of the DMC refining column 7 was 0.02MPaG, the top temperature was 67.7 ℃ and the bottom temperature was 70.6 ℃. The optimum operating pressure of the methanol refining column 4 was-0.051 MPaG, the column top temperature was 69.5 ℃ and the column bottom temperature was 161 ℃.
The gas phase condensation latent heat at the top of the DMC rectifying tower 1 in the prior method is completely taken away by circulating cooling water, thereby causing a great deal of waste of energy. The heat source is provided for the reboiler 21 at the bottom of the methanol refining tower by utilizing the gas phase condensation latent heat at the top of the DMC rectifying tower 1, the recycling of the vaporization latent heat is realized, and the steam required by the reboiler 21 at the bottom of the methanol refining tower is further saved.
The invention is not limited to the above alternative embodiments, and any other various forms of products can be obtained by anyone in the light of the present invention, but any changes in shape or structure thereof, which fall within the scope of the present invention as defined in the claims, fall within the scope of the present invention.

Claims (10)

1. The three-tower differential pressure thermal coupling rectification method for separating the methanol, the dimethyl carbonate and the phenol is characterized by comprising the following steps of:
s1: introducing a stream from the diphenyl carbonate reaction tower into the middle lower part of the DMC rectifying tower (1);
s2: condensing a gas stream at the top of the DMC rectifying tower (1) and introducing the gas stream into the middle of the methanol refining tower (4);
s3: sending the top stream of the methanol refining tower (4) back to the middle upper part of the DMC rectifying tower (1);
s4: a methanol product is extracted from the bottom of the methanol refining tower (4);
s5: introducing the bottom stream of the DMC rectifying tower (1) into a DMC refining tower (7);
s6: extracting DMC product from the top of the DMC refining tower (7);
s7: phenol product is recovered from the bottom of the DMC refining tower (7).
2. The three-tower differential pressure thermal coupling rectification method for separating methanol from dimethyl carbonate and phenol according to claim 1 is characterized in that in step S2, when condensing the gas stream at the top of the DMC rectification tower (1), the gas stream is introduced into the tube side of a methanol refining tower bottom reboiler (21).
3. The three-tower differential pressure thermal coupling rectification method for separating methanol from dimethyl carbonate and phenol according to claim 2 is characterized in that in step S2, a stream passing through a methanol refining tower bottom reboiler (21) is passed into a DMC rectification tower top first condenser (22) to be condensed again.
4. The three-column differential pressure thermal coupling rectification method for separating methanol from dimethyl carbonate and phenol according to claim 3 is characterized in that in step S2, a part of the stream passing through the methanol refining column bottom reboiler (21) and the DMC rectification column top first condenser (22) is sent back to the top of the DMC rectification column (1).
5. The three-tower differential pressure thermal coupling rectification method for separating methanol from dimethyl carbonate and phenol according to claim 2 is characterized in that in step S4, part of the stream at the bottom of the methanol refining tower (4) passes through the shell side of a reboiler (21) at the bottom of the methanol refining tower and then is introduced into the bottom of the methanol refining tower (4), and the other part of the stream is extracted.
6. The three-tower differential pressure thermal coupling rectification method for separating methanol from dimethyl carbonate and phenol according to claim 1, characterized in that in step S4, during the first startup, a part of stream at the bottom of the methanol refining tower (4) enters the bottom of the methanol refining tower (4) after passing through a startup reboiler (63), and another part of stream is extracted.
7. The three-tower differential pressure thermal coupling rectification method for separating methanol from dimethyl carbonate and phenol according to claim 1 is characterized in that in step S3, a gas stream at the top of the methanol refining tower (4) is introduced into a second condenser (51) at the top of the methanol refining tower, a part of the fully condensed stream is sent back to the top of the methanol refining tower (4), and the other part of the stream is returned to the middle upper part of the DMC rectifying tower (1).
8. The three-tower differential pressure thermal coupling rectification method for separating the methanol from the dimethyl carbonate and the phenol according to claim 1 is characterized in that in step S5, part of stream at the bottom of the DMC rectification tower (1) passes through a reboiler (32) at the bottom of the DMC rectification tower and then is introduced into the bottom of the DMC rectification tower (1), and the extracted stream is introduced into the middle of the DMC refining tower (7).
9. The three-tower differential pressure thermal coupling rectification method for separating methanol from dimethyl carbonate and phenol according to claim 1 is characterized in that in step S6, a gas stream at the top of the DMC refining tower (7) is introduced into a DMC refining tower top condenser (81), part of the stream of the fully condensed stream is sent back to the top of the DMC refining tower (7), and the other part of the stream is extracted.
10. The three-tower differential pressure thermal coupling rectification method for separating methanol from dimethyl carbonate and phenol according to any one of claims 1 to 9, characterized in that in step S7, a part of stream at the bottom of the DMC refining tower (7) passes through a DMC refining tower bottom reboiler (92) and then is introduced into the bottom of the DMC refining tower (7), and another part of stream is extracted.
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