CN111170863A - Energy-saving process method and device for purifying dimethyl carbonate by adopting four-tower heat integration - Google Patents

Energy-saving process method and device for purifying dimethyl carbonate by adopting four-tower heat integration Download PDF

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Publication number
CN111170863A
CN111170863A CN202010180483.3A CN202010180483A CN111170863A CN 111170863 A CN111170863 A CN 111170863A CN 202010180483 A CN202010180483 A CN 202010180483A CN 111170863 A CN111170863 A CN 111170863A
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tower
methanol
dimethyl carbonate
light
pressure
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蓝仁水
黄贵明
曹海龙
汤伟
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New Tianjin T & D Co ltd
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New Tianjin T & D Co ltd
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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C68/00Preparation of esters of carbonic or haloformic acids
    • C07C68/08Purification; Separation; Stabilisation
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D3/00Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/14Fractional distillation or use of a fractionation or rectification column
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/10Process efficiency

Abstract

The invention relates to an energy-saving process method and a device for purifying dimethyl carbonate by adopting four-tower heat integration, wherein a high-purity dimethyl carbonate product and a byproduct methanol product are produced from a crude dimethyl carbonate raw material by adopting a four-tower heat integration device through a rectification process. The whole device at least comprises four towers of a light and heavy component removing tower T110, a high-pressure tower T120, a dimethyl carbonate rectifying tower T130, a methanol tower T140 and the like and matched equipment thereof. The invention adopts the clapboard tower structure and the multi-tower heat integration process method, effectively overcomes the defects of the prior art, greatly reduces the operation energy consumption, has obvious practicability and economic benefit and has wide application prospect.

Description

Energy-saving process method and device for purifying dimethyl carbonate by adopting four-tower heat integration
Technical Field
The invention relates to an energy-saving process method and an energy-saving device for purifying dimethyl carbonate by adopting four-tower heat integration, in particular to an energy-saving process method and an energy-saving device for producing a high-purity dimethyl carbonate product and a byproduct methanol product from a crude dimethyl carbonate raw material by adopting a four-tower heat integration device through a rectification process.
Background
Dimethyl carbonate is DMC, a colorless transparent liquid with pungent odor at normal temperature, is combustible, nontoxic and biodegradable. Dimethyl carbonate is an important organic chemical intermediate, and can be used for organic synthesis reactions such as carbonylation, methylation, methoxylation, carbonylation and the like due to the molecular structure of the dimethyl carbonate containing carbonyl, methyl, methoxyl and carbonylmethoxyl; because DMC is non-toxic, can replace virulent phosgene, methyl chloroformate, dimethyl sulfate and the like to be used as methylating agents or carbonylating agents, the safety of production operation is improved, and the environmental pollution is reduced; as a solvent, DMC can replace Freon, trichloroethane, trichloroethylene, benzene, xylene and the like and is used for paint, cleaning solvent and the like; as a gasoline additive, DMC can improve its octane number and oxygen content, and then improve its antiknock; DMC is also used as an additive for detergents, surfactants and softeners, and in any case DMC has a very wide range of applications.
In the production process of the coal-to-ethylene glycol, substances such as dimethyl carbonate, methyl formate, methylal and the like can be by-produced to influence the stable operation of a system, the mixture which is not separated in the existing coal-to-ethylene glycol device and is rich in the dimethyl carbonate and the like is sold as cheap residual liquid, and along with the improvement of the environmental protection requirement and the further requirement of the comprehensive economy of the device, the developed technology-advanced dimethyl carbonate rectification process method has more and more remarkable economic benefits.
Chinese patent CN107400055A discloses a battery-grade dimethyl carbonate rectification and purification method and equipment, and provides a battery-grade dimethyl carbonate rectification and purification method and equipment, which comprise two rectification towers, namely a normal-pressure bulkhead rectification tower, a low-pressure bulkhead rectification tower and the like. The heat integration operation is carried out between the normal pressure bulkhead rectifying tower and the low pressure bulkhead rectifying tower, and the gas phase at the top of the normal pressure bulkhead rectifying tower provides the energy required by the separation for the low pressure bulkhead rectifying tower. This purification method has two major drawbacks: firstly, as is well known, dimethyl carbonate and methanol can form an azeotrope with a lower boiling point, wherein dimethyl carbonate and methanol are not completely separated, and the azeotrope can only be separated, so that a high-purity dimethyl carbonate product can be obtained, but the yield of dimethyl carbonate is greatly reduced along with the evaporation of methanol and the azeotrope thereof; the second defect is that the low-pressure bulkhead rectifying tower for extracting the dimethyl carbonate product is operated in high vacuum, the temperature of the top of the tower is very low (25-33 ℃), a large amount of low-temperature water is consumed as a condensing medium, and the operation cost is very high.
CN1271721A discloses a method for separating methanol and dimethyl carbonate azeotrope under pressure, which comprises two rectifying towers, namely a pressure rectifying tower and an atmospheric pressure rectifying tower, wherein the pressure rectifying tower and the atmospheric pressure rectifying tower are subjected to heat integration operation, and the gas phase at the top of the pressure rectifying tower provides energy required by separation for the atmospheric pressure rectifying tower. Although the method overcomes the defect that a large amount of low-temperature water is consumed in the CN107400055A, two large defects still exist: firstly, similar to the method provided by CN107400055A, dimethyl carbonate is not completely separated from methanol, only azeotrope can be separated, although higher purity dimethyl carbonate product can be obtained, the yield of dimethyl carbonate is lower along with the evaporation of methanol and azeotrope thereof; secondly, the dimethyl carbonate product is obtained from the tower bottom of the normal pressure refining tower, the product purity is not high, if the dimethyl carbonate product with higher purity (99.9%) is desired to be obtained, the operating pressure of the pressurized rectifying tower reaches 1.8MPa, the operating pressure is too high, the operating temperature is high, the equipment safety level is higher, and the investment is higher.
CN108299204A discloses a method and a device for separating dimethyl carbonate from coal-derived ethylene glycol raffinate, wherein the method comprises three rectifying towers, namely a light component removing tower, a crude DMC rectifying tower, a fine DMC rectifying tower and the like, the three rectifying towers are subjected to heat integration operation, and the crude DMC rectifying tower and the fine DMC rectifying tower provide energy required by separation for a reboiler of the light component removing tower. Although CN108299204A overcomes the defect that CN107400055A needs to consume a large amount of low-temperature water, there are two major defects: the first defect, according to the CN108299204A claim 2, "the operating pressure of the light component removal tower is 6-10Kpa, the temperature of the top of the tower is 42-49 ℃, the temperature of the bottom of the tower is 65-69 ℃", and the light component removal tower described in example 1 "the mixture of about 54% of methanol, about 45% of dimethyl carbonate and about 1% of water at the bottom of the tower is returned to the middle tank zone", and "the mixture enters the crude DMC rectification tower 2, 80% of methanol, 20% of dimethyl carbonate and trace amount of low boiling fraction are discharged from the top of the tower after rectification" described in example 1, all indicate that the separation method provided by CN108299204A does not completely separate dimethyl carbonate from methanol, and the large amount of dimethyl carbonate is lost at the bottom of the light component removal tower and the top of the crude DMC rectification tower, and the yield of dimethyl carbonate is very low; and the defect II is that the rectifying DMC rectifying tower does not adopt a partition plate tower structure, and the dimethyl carbonate product is extracted from the side line of the rectifying DMC rectifying tower, so that the high-purity dimethyl carbonate product cannot be obtained no matter the side line is positioned above the feeding material (inevitably carrying light components) or below the feeding material (inevitably carrying heavy components).
Disclosure of Invention
The invention aims to provide an energy-saving process method and device for rectifying and purifying dimethyl carbonate, which are an energy-saving process method and device for producing a high-purity dimethyl carbonate product and a byproduct methanol product from a crude dimethyl carbonate raw material through a rectifying process by adopting a four-tower heat integration device, can overcome the defects of the prior art, greatly reduce the operation energy consumption, have remarkable practicability and economic benefit and have wide application prospect.
The energy-saving process method for purifying the dimethyl carbonate by adopting the four-tower heat integration provided by the invention comprises the following steps:
1) at least comprises a light component removing tower T110, a high pressure tower T120, a dimethyl carbonate rectifying tower T130 and a methanol tower T140.
2) The light and heavy component removing tower T110 can adopt a conventional rectifying tower or a clapboard tower, light components 5 are extracted from the top of the tower, first heavy components 7 are extracted from the bottom of the tower, and side materials 6 are sent to a high-pressure tower T120.
3) The high-pressure tower T120 is pressurized, a mixture of dimethyl carbonate and methanol 15 is extracted from the top of the tower, a methanol removing tower T140 is extracted from the bottom of the tower, and a crude dimethyl carbonate 16 without methanol is obtained from the bottom of the tower, and a dimethyl carbonate rectifying tower T130 is removed.
4) The dimethyl carbonate rectifying tower T130 preferably adopts a clapboard tower, the dimethyl carbonate product 21 is fed from one side of the clapboard, the dimethyl carbonate and methanol mixture 20 is taken out from the top of the tower, the dimethyl carbonate and methanol mixture is preferably fed back to the high-pressure tower T120, the methanol tower T140 can also be fed, and the second heavy component 22 is taken out from the bottom of the tower.
5) The methanol tower T140 is typically operated at normal pressure, and the mixture 26 of dimethyl carbonate and methanol is taken out from the top of the tower, preferably returned to the upper part of the high pressure tower T120, also returned to the upper part of the light and heavy component removal tower T110 or returned to the feed of the high pressure tower T120; the methanol tower T140 obtains a recovered methanol product 27, and the recovered methanol can be extracted from the lower side line of the methanol tower T140 in order to improve the quality of the recovered methanol.
6) Heat integration is performed among the light and heavy component removal tower T110, the high-pressure tower T120, the dimethyl carbonate rectifying tower T130 and the methanol tower T140, and a typical heat integration mode is as follows: the energy required by a reboiler at the bottom of the light and heavy component removal tower T110 is provided by the gas phase at the top of the high-pressure tower T120; the energy required by the reboiler at the tower bottom of the methanol tower T140 is respectively provided by the gas phase at the tower top of the high-pressure tower T120 and the gas phase at the tower top of the dimethyl carbonate rectifying tower T130; the high-pressure tower T120 and the dimethyl carbonate rectifying tower T130 adopt external heat sources for heating.
7) The dimethyl carbonate and the methanol in the feed are completely separated, the purity of the dimethyl carbonate product can reach 99.99 percent, and the content of the dimethyl carbonate in the recovered methanol is lower than 0.1 percent.
The process method provided by the invention is shown as the attached figure 1 and comprises the following steps:
crude dimethyl carbonate raw material 1 enters a light and heavy component removal tower T110.
A gas phase 2 at the top of the light and heavy component removal tower T110 is condensed by a condenser E1101 of the light and heavy component removal tower, a condensate 3 is directly returned to the top of the light and heavy component removal tower T110 as a reflux liquid, a non-condensable gas 4 is condensed and cooled by a light component condenser E1102, and a condensate 5 is sent out of the device as a light component; a liquid phase material 6 is extracted from the upper side line of the light and heavy component removal tower T110 and enters a high pressure tower T120; and the liquid phase material in the bottom of the tower T110 of the light and heavy component removal tower is taken as the heavy component 7 and sent out of the device.
The high-pressure tower T120, a light and heavy component removal tower T110 and a methanol tower T140 are subjected to heat integration operation, a gas phase 8 at the top of the high-pressure tower T120 is divided into two parts of a gas phase 9 and a gas phase 11, the gas phase 9 enters a reboiler E1103 shell pass of the light and heavy component removal tower, the gas phase 11 enters a reboiler E1402 shell pass of the methanol tower, a condensate 10 obtained by condensing the gas phase 9 at the top of the tower and a condensate 12 obtained by condensing the gas phase 11 at the top of the tower are mixed to obtain a condensate 13, the condensate 13 is divided into two strands, one strand is used as a reflux 14 and directly returned to the top of the high-pressure tower T120; the bottoms 16 of the high-pressure column T120 enter the feed side L130 of the dimethyl carbonate rectification column T130.
The dimethyl carbonate rectifying tower T130 and the methanol tower T140 are subjected to heat integration operation, gas phase 17 at the top of the dimethyl carbonate rectifying tower T130 enters a shell pass of a reboiler E1403 of the methanol tower, condensate 18 obtained after condensation of the gas phase 17 at the top of the methanol tower is divided into two parts, one part is used as reflux liquid 19 and directly returns to the top of the dimethyl carbonate rectifying tower T130, and the other part of condensate 20 enters a high-pressure tower T120; the material collected from the side line R130 at the collecting side of the dimethyl carbonate rectifying tower T130 is sent out of the device as a dimethyl carbonate product 21; the material in the bottom of the dimethyl carbonate rectifying tower T130 is taken as the heavy component 22 and sent out of the device.
The condensate 24 of the gas phase 23 at the top of the methanol tower T140 condensed by the methanol tower condenser E1401 is divided into two parts, one part is used as reflux liquid 25 and directly returned to the top of the methanol tower T140, and the other part of the condensate 26 enters the upper part of the high-pressure tower T120; the material in the bottom of the methanol tower T140 is sent out of the device as a methanol product 27.
According to the process method provided by the invention, the four-tower heat integration rectification is adopted to purify the dimethyl carbonate, and the process method can be transformed into other heat integration processes to purify the dimethyl carbonate by rectification.
The first deformation process method comprises the following steps: as shown in FIG. 2, in the four columns, the dimethyl carbonate rectifying column T130 can be omitted, the high pressure column T120 adopts a baffle column structure, the dimethyl carbonate product 21 is fed from one side of the baffle, the dimethyl carbonate product is extracted from the other side of the baffle, and the second heavy component 22 is discharged from the bottom of the column.
And a second deformation process method comprises the following steps: as shown in the attached figure 3, in the four towers, the light and heavy component removing tower T110 can be omitted, the raw material 1 directly enters the high-pressure tower T120, the light component 5 is extracted from the top of the high-pressure tower T120, the mixture of dimethyl carbonate and methanol 15 is extracted from the upper side line of the high-pressure tower T120, the methanol removing tower T140 is extracted from the tower bottom, and the dimethyl carbonate crude product 16 which does not contain methanol basically is obtained, and the dimethyl carbonate rectifying tower T130 is removed.
And a deformation process method III: as shown in fig. 4, in the above four columns, the high pressure column T120 and the dimethyl carbonate rectification column T130 can be omitted, the light and heavy component removing column T110 adopts a baffle column structure, the raw material 1 is fed from one side of the baffle, the dimethyl carbonate product 21 is extracted from the other side of the baffle, the light component 5 is extracted from the top of the column, the mixture 6 of dimethyl carbonate and methanol (material 6) is extracted from the upper side line, the methanol removing column T140 is used, and the first heavy component 7 is discharged from the bottom of the column; the mixture 26 of dimethyl carbonate and methanol is extracted from the top of the methanol tower T140 and returns to the light and heavy component removing tower T110 for feeding, and the methanol tower T140 obtains a recovered methanol product 27. More specifically, when the methanol content in the feed is low, the light and heavy component removing tower T110, the high pressure tower T120 and the methanol tower T140 can be omitted, the raw material 1 directly enters the feed side L130 of the clapboard of the dimethyl carbonate rectifying tower T130, the light component 5 is extracted from the top of the tower, the first heavy component 7 is extracted from the bottom of the tower, and the dimethyl carbonate product 21 is extracted from the clapboard extraction side R130.
And a deformation process method comprises the following steps: as shown in FIG. 5, in the above four columns, the light and heavy components removal column T110 is of a baffle column structure, and the material 6 is fed from a baffle feeding side L110 and taken out from a baffle taking-out side R110 to a high pressure column T120.
And a deformation process method five: as shown in fig. 6, in the four towers described in the fourth variant process, the light and heavy component removal tower T110 adopts a partition tower structure, and can take two side streams, and a liquid phase side stream (a mixture of dimethyl carbonate and methanol) material 6 is taken out above the partition section of the light and heavy component removal tower T110 and sent to the upper part of the high pressure tower T120; another liquid phase side line (dimethyl carbonate crude product containing substantially no methanol) 29 is taken from the clapboard section of the light and heavy component removal tower T110 and is sent to the middle lower part of a high-pressure tower T120 or enters the middle part of a dimethyl carbonate rectifying tower T130.
The deformation process method comprises the following steps: as shown in the attached figure 7, in the four columns of the deformation process method five, the high pressure column T120 can be omitted, and a liquid phase side line (a mixture of dimethyl carbonate and methanol) material 6 methanol removing column T140 is taken out above a partition section of a light and heavy component removing column T110; another liquid phase side line (dimethyl carbonate crude product containing substantially no methanol) is taken from the clapboard section of the light and heavy component removal tower T110, and the feed side (L130) of the clapboard of the dimethyl carbonate rectification tower T130 is removed.
The deformation process method is seven: as shown in the attached figure 8, in the four towers, when the requirement for recovering the methanol is not high, the methanol tower T140 can be omitted, and the recovered methanol 27 is extracted from the tower bottom of the light and heavy component removing tower T110 instead.
And the deformation process method comprises the following steps: as shown in fig. 9, in the four towers, the gas phase at the top of the high-pressure tower T120 is not heated by the bottom of the methanol tower T140 any more, and the energy required by the reboiler at the bottom of the light and heavy component removing tower T110 is provided by the gas phase at the top of the high-pressure tower T120; the energy required by the reboiler at the bottom of the methanol tower T140 is provided by the gas phase at the top of the dimethyl carbonate rectifying tower T130.
According to the process method provided by the invention, the typical operation range of the methanol content in the tower bottom of the high-pressure tower T120 is 0.01-6% (except for special specifications, the mass percentages are all referred to in the specification). The methanol content in the bottom of the high-pressure column T120 does not constitute any limitation to the invention.
According to the process method provided by the invention, the heat integration mode among the four towers can also be as follows: the energy required by the reboiler at the bottom of the light and heavy component removal tower T110 is completely provided by the gas phase at the top of the dimethyl carbonate rectifying tower T130; the energy required by the reboiler of the tower bottom of the methanol tower T140 is provided by the gas phase at the top of the high-pressure tower T120.
According to the process method provided by the invention, the heat integration mode among the four towers can also be as follows: the gas phase at the top of the dimethyl carbonate rectifying tower T130 is used for feeding and heating the light and heavy component removal tower T110, and can also be used for heating a certain position between the feeding of the light and heavy component removal tower T110 and the tower kettle.
According to the process method provided by the invention, an intermediate heat exchanger or a circulating cooling section can be arranged between the top of the light and heavy component removal tower T110 and the position of the liquid-phase material 6 extracted from the upper side line, and is used for partially condensing ascending gas and reducing the heat load of a condenser at the top of the tower. According to the process method provided by the invention, when the heavy component content in the feed is higher, a dimethyl carbonate recovery tower can be additionally arranged for recovering dimethyl carbonate in the discharge of the tower bottom of the light and heavy component removing tower T110 and purifying the heavy component material. According to the process method provided by the invention, when the content of light components in the feed is higher, a light component concentration tower can be additionally arranged for recovering dimethyl carbonate in the top discharge of the light component removing tower T110 and concentrating the light components. These are conventional processes in chemical separation processes, and those skilled in the relevant technical field can implement appropriate recovery methods according to specific device conditions, and the various evolved process flows formed thereby should be considered to be within the spirit, scope and content of the present invention.
In order to simplify the process description, a product cooler in each process is omitted, and heat exchange between cold and hot materials in the system is omitted.
The heat exchange between cold and hot materials in the system comprises the following steps: preheating a raw material 1 by using a dimethyl carbonate product 21; preheating the raw material 1 by adopting steam condensate; the feeding of the high-pressure tower T120 is preheated by the discharging 15 at the top of the high-pressure tower T120; the higher pressure column T120 feed is preheated with steam condensate, and the like.
The heat exchange method is only an auxiliary method for providing further energy saving of the process method, and does not limit the invention in any way, and persons skilled in the relevant technical field can implement appropriate heat exchange method of the system internal material flow according to specific device conditions, and various evolution process flows formed by the method are considered to be in the spirit, scope and content of the invention.
According to the process method provided by the invention, the external heat sources used by the high-pressure tower reboiler E1201 and the dimethyl carbonate rectifying tower reboiler E1301 can be fresh steam, heat conducting oil or material steam generated in the system.
According to the process provided by the invention, the typical operating conditions of each tower are as follows:
the operation pressure range of the top of the light and heavy component removal tower T110 is 30-300 kPa;
the operation pressure range of the top of the high-pressure tower T120 is 500-1500 kPa;
the operating pressure range of the top of the dimethyl carbonate rectifying tower T130 is 80-600 kPa;
the operating pressure range of the top of the methanol tower T140 is 30-400 kPa.
All pressures in the present invention are referred to as absolute pressures, unless otherwise specified.
According to the process provided by the invention, the preferable operation conditions of each tower are as follows:
the operation pressure of the top of the light and heavy component removal tower T110 is 80-190 kpa, the operation temperature of the top of the tower is 35-70 ℃, and the operation temperature of a tower kettle is 85-110 ℃;
the operation pressure of the top of the high-pressure tower T120 is 700-1100 kPa, the operation temperature of the top of the tower is 115-135 ℃, and the operation temperature of the bottom of the tower is 160-180 ℃;
the operating pressure of the top of the dimethyl carbonate rectifying tower T130 is 100-300 kPa, the operating temperature of the top of the tower is 60-130 ℃, and the operating temperature of the bottom of the tower is 110-135 ℃;
the operation pressure of the top of the methanol tower T140 is 80-150 kpa, the operation temperature of the top of the tower is 55-75 ℃, and the operation temperature of the bottom of the tower is 58-82 ℃.
The invention provides an energy-saving device for purifying dimethyl carbonate by adopting four-tower heat integration, which mainly comprises four towers of a light and heavy component removal tower T110, a high-pressure tower T120, a dimethyl carbonate rectifying tower T130, a methanol tower T140 and connecting pipelines:
the raw material crude dimethyl carbonate feed pipeline is connected to the middle part of the light and heavy component removal tower T110.
The top of the light and heavy component removal tower T110 is connected with a light and heavy component removal tower condenser E1101, a condensate outlet of the light and heavy component removal tower condenser E1101 is connected with the top of the light and heavy component removal tower T110, a non-condensable gas outlet of the light and heavy component removal tower condenser E1101 is connected with a light component condenser E1102, and a condensate outlet of the light component condenser E1102 is connected with a light component extraction pipeline; a side draw-out port at the upper part of the light and heavy component removal tower T110 is connected with the middle part of a high-pressure tower T120; the bottom of the light and heavy component removal tower T110 is respectively connected with a tube side inlet of a light and heavy component removal tower reboiler E1103 and a first heavy component 7 extraction pipeline, and a tube side outlet of the light and heavy component removal tower reboiler E1103 is connected to a tower kettle of the light and heavy component removal tower T110.
The top of the high-pressure tower T120 is respectively connected with a light and heavy component removal tower reboiler E1103 shell pass and a methanol tower reboiler E1402 shell pass, a light and heavy component removal tower reboiler E1103 shell pass condensate pipeline and a methanol tower reboiler E1402 shell pass condensate pipeline are converged to form a high-pressure tower T120 top condensate pipeline, and the pipelines are respectively connected with the top of the high-pressure tower T120 and the middle of the methanol tower T140; the bottom of the high-pressure tower T120 is respectively connected with the tube pass inlet of a high-pressure tower reboiler E1201 and the middle part of the feed side L130 of the dimethyl carbonate rectifying tower T130, and the tube pass outlet of the high-pressure tower reboiler E1201 is connected to the tower kettle of the high-pressure tower T120.
The top of the dimethyl carbonate rectifying tower T130 is connected with the shell pass of a methanol tower reboiler E1403, and a condensate outlet of the shell pass of the methanol tower reboiler E1403 is respectively connected with the top of the dimethyl carbonate rectifying tower T130 and the middle of a high-pressure tower T120; a side line withdrawing port R130 at the withdrawing side of the dimethyl carbonate rectifying tower T130 is connected with a dimethyl carbonate product withdrawing pipeline; the bottom of the dimethyl carbonate rectifying tower T130 is respectively connected with a tube pass inlet of a reboiler E1301 of the dimethyl carbonate rectifying tower and a second heavy component 22 extraction pipeline, and a tube pass outlet of the reboiler E1301 of the dimethyl carbonate rectifying tower is connected with the tower bottom of the dimethyl carbonate rectifying tower T130.
The top of the methanol tower T140 is connected with a methanol tower condenser E1401, and a condensate outlet of the methanol tower condenser E1401 is respectively connected with the top of the methanol tower T140 and the upper part of the high-pressure tower T120; the bottom of the methanol tower T140 is respectively connected with a tube side inlet of a methanol tower reboiler E1402, a tube side inlet of a methanol tower reboiler E1403 and a methanol extraction pipeline, and a tube side outlet of the methanol tower reboiler E1402 and a tube side outlet of the methanol tower reboiler E1403 are both connected to a tower kettle of the methanol tower T140.
The invention provides an energy-saving process method and an energy-saving device for purifying dimethyl carbonate by adopting four-tower heat integration, which are an energy-saving process method and an energy-saving device for producing a high-purity dimethyl carbonate product and a byproduct methanol product from a crude dimethyl carbonate raw material by adopting a four-tower heat integration device through a rectification process. The whole device at least comprises four towers of a light and heavy component removing tower T110, a high-pressure tower T120, a dimethyl carbonate rectifying tower T130, a methanol tower T140 and the like and matched equipment thereof. The invention adopts a multi-tower heat integration process method, can overcome the defects of the prior art, greatly reduces the operation energy consumption, has obvious practicability and economic benefit and has wide application prospect.
Drawings
FIG. 1 is a process flow diagram of a typical four-tower heat integrated apparatus for rectification and purification of dimethyl carbonate according to the present invention.
Fig. 2 is a development process of fig. 1, namely a deformation process. In the four-column heat integration shown in fig. 1, the dimethyl carbonate rectification column T130 can be omitted, the high-pressure column T120 adopts a partition column structure, the dimethyl carbonate product 21 is fed from one side of the partition, the dimethyl carbonate product 21 is extracted from the other side of the partition, and the 2 nd heavy component 22 is discharged from the bottom of the column.
Fig. 3 is a development process of fig. 1, namely a deformation process two. In the four-tower heat integration shown in fig. 1, a light and heavy component removing tower T110 can be omitted, a raw material 1 directly enters a high-pressure tower T120, light components 5 are extracted from the top of the high-pressure tower T120, a mixture of dimethyl carbonate and methanol 15 is extracted from the upper side line of the high-pressure tower T120 to form an methanol removing tower T140, and a crude dimethyl carbonate product 16 which does not contain methanol basically is obtained from the bottom of the tower to form a dimethyl carbonate rectifying tower T130.
Fig. 4 is a development process of fig. 1, namely a deformation process. In the four-tower heat integration shown in fig. 1, a high-pressure tower T120 and a dimethyl carbonate rectifying tower T130 can be omitted, a light and heavy component removing tower T110 adopts a partition plate tower structure, a raw material 1 is fed from one side of a partition plate, a dimethyl carbonate product 21 is extracted from the other side of the partition plate, a light component 5 is extracted from the top of the tower, a mixture material of dimethyl carbonate and methanol is extracted from the upper side line, a methanol removing tower T140 is extracted, and a first heavy component 7 is discharged from the bottom of the tower; the mixture 26 of dimethyl carbonate and methanol is extracted from the top of the methanol tower T140 and returns to the light and heavy component removing tower T110 for feeding, and the methanol tower T140 obtains a recovered methanol product 27.
Fig. 5 is a development process of fig. 1, namely a deformation process four. In the four-column heat integration shown in fig. 1, the light and heavy component removal column T110 adopts a baffle column structure, and the material is fed from a baffle feeding side L110, and the material 6 is extracted from a baffle extraction side R110 and sent to a high pressure column T120.
Fig. 6 is an evolution process of fig. 5, namely a deformation process five. In the four-tower heat integration shown in fig. 5, the light and heavy component removal tower T110 adopts a partition tower structure, two side streams can be extracted, and a liquid phase side stream (a mixture of dimethyl carbonate and methanol) material 6 is extracted above the partition section of the light and heavy component removal tower T110 and is fed to the upper part of the high pressure tower T120; another liquid phase side line (dimethyl carbonate crude product containing substantially no methanol) 29 is taken from the clapboard section of the light and heavy component removal tower T110 and is sent to the middle lower part of a high-pressure tower T120.
Fig. 7 is an evolution process of fig. 6, namely deformation process six. In the four-column heat integration shown in fig. 6, the high pressure column T120 can be omitted, and a liquid phase side stream (dimethyl carbonate and methanol mixture) material 6 methanol removing column T140 is taken above the partition section of the light and heavy component removing column T110; the light component removal tower T110 baffle section produces another liquid phase side line (dimethyl carbonate crude product which does not contain methanol basically) 29 to remove dimethyl carbonate rectifying tower T130 baffle feed side L130.
Fig. 8 is a development process, namely deformation process seven, of fig. 1. In the four-tower heat integration shown in fig. 1, when the requirement for recovering methanol is not high, the methanol tower T140 can be omitted, and the recovered methanol 27 is extracted from the bottom of the light and heavy component removal tower T110 instead.
Fig. 9 is an evolution process of fig. 1, namely a deformation process eight. In the four-tower heat integration shown in fig. 1, the gas phase at the top of the high-pressure tower T120 does not heat the bottom of the methanol tower T140 any more, and the energy required by the reboiler at the bottom of the light and heavy component removal tower T110 is provided by the gas phase at the top of the high-pressure tower T120; the energy required by the reboiler at the bottom of the methanol tower T140 is provided by the gas phase at the top of the dimethyl carbonate rectifying tower T130.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, which are illustrative only and not limiting of the invention.
Unless otherwise specified, the composition, structure, materials (connecting lines for connecting the towers), reagents, and the like of the process equipment such as the towers, etc., which are not specifically used in the examples, can be obtained from commercial sources, or can be obtained by methods well known to those skilled in the art. The specific experimental procedures and operating conditions involved are generally in accordance with conventional process conditions and conditions as described in the manual or as recommended by the manufacturer.
The invention provides an energy-saving process method for rectifying and purifying dimethyl carbonate by adopting a four-tower heat integration device, which comprises the following steps:
1) at least comprises a light component removing tower T110, a high pressure tower T120, a dimethyl carbonate rectifying tower T130 and a methanol tower T140;
2) the light and heavy component removal tower T110 can adopt a conventional rectifying tower or a clapboard tower, light components are extracted from the top of the tower, heavy components 1 are extracted from the bottom of the tower, and materials at the side line are sent to a high-pressure tower T120;
3) the high-pressure tower T120 is pressurized, a methanol removing tower T140 for removing the mixture of dimethyl carbonate and methanol is extracted from the tower top, and a rectifying tower T130 for removing dimethyl carbonate from a dimethyl carbonate crude product which does not contain methanol basically is obtained from the tower bottom;
4) the dimethyl carbonate rectifying tower T130 preferably adopts a clapboard tower, the dimethyl carbonate product is extracted from one side of the clapboard, the mixture of dimethyl carbonate and methanol is extracted from the top of the tower, the mixture is preferably returned to the high-pressure tower T120 for feeding, the methanol tower T140 can also be fed, and the second heavy component 22 is extracted from the bottom of the tower;
5) the methanol tower T140 is typically operated at normal pressure, and a mixture of dimethyl carbonate and methanol is extracted from the top of the tower, preferably returned to the upper part of the high-pressure tower T120, also returned to the upper part of the light and heavy component removal tower T110 or returned to the feeding of the high-pressure tower T120; the methanol tower T140 obtains a recovered methanol product, and the recovered methanol can be extracted from the lower side line of the methanol tower T140 in order to improve the quality of the recovered methanol;
6) heat integration is performed among the light and heavy component removal tower T110, the high-pressure tower T120, the dimethyl carbonate rectifying tower T130 and the methanol tower T140, and a typical heat integration mode is as follows: the energy required by a reboiler at the bottom of the light and heavy component removal tower T110 is provided by the gas phase at the top of the high-pressure tower T120; the energy required by the reboiler at the tower bottom of the methanol tower T140 is respectively provided by the gas phase at the tower top of the high-pressure tower T120 and the gas phase at the tower top of the dimethyl carbonate rectifying tower T130; the high-pressure tower T120 and the dimethyl carbonate rectifying tower T130 adopt external heat sources for heating;
7) the dimethyl carbonate and the methanol in the feed are completely separated, the purity of the dimethyl carbonate product can reach 99.99 percent, and the content of the dimethyl carbonate in the recovered methanol is lower than 0.1 percent.
The process method provided by the invention comprises the following specific steps:
crude dimethyl carbonate raw material 1 enters a light and heavy component removal tower T110.
A gas phase 2 at the top of the light and heavy component removal tower T110 is condensed by a condenser E1101 of the light and heavy component removal tower, a condensate 3 is directly returned to the top of the light and heavy component removal tower T110 as a reflux liquid, a non-condensable gas 4 is condensed and cooled by a light component condenser E1102, and a condensate 5 is sent out of the device as a light component; a liquid phase material 6 is extracted from the upper side line of the light and heavy component removal tower T110 and enters a high pressure tower T120; and the liquid phase material in the bottom of the light and heavy component removing tower T110 is taken as the first heavy component 7 and sent out of the device.
The high-pressure tower T120, a light and heavy component removal tower T110 and a methanol tower T140 are subjected to heat integration operation, a gas phase 8 at the top of the high-pressure tower T120 is divided into two parts of a gas phase 9 and a gas phase 11, the gas phase 9 enters a reboiler E1103 shell pass of the light and heavy component removal tower, the gas phase 11 enters a reboiler E1402 shell pass of the methanol tower, a condensate 10 obtained by condensing the gas phase 9 at the top of the tower and a condensate 12 obtained by condensing the gas phase 11 at the top of the tower are mixed to obtain a condensate 13, the condensate 13 is divided into two strands, one strand is used as a reflux 14 and directly returned to the top of the high-pressure tower T120; the bottoms 16 of the high-pressure column T120 enter the feed side L130 of the dimethyl carbonate rectification column T130.
The dimethyl carbonate rectifying tower T130 and the methanol tower T140 are subjected to heat integration operation, gas phase 17 at the top of the dimethyl carbonate rectifying tower T130 enters a shell pass of a reboiler E1403 of the methanol tower, condensate 18 obtained after condensation of the gas phase 17 at the top of the methanol tower is divided into two parts, one part is used as reflux liquid 19 and directly returns to the top of the dimethyl carbonate rectifying tower T130, and the other part of condensate 20 enters a high-pressure tower T120; the material collected from the side line R130 at the collecting side of the dimethyl carbonate rectifying tower T130 is sent out of the device as a dimethyl carbonate product 21; the material in the bottom of the dimethyl carbonate rectifying tower T130 is taken as a second heavy component 22 and sent out of the device.
The condensate 24 of the gas phase 23 at the top of the methanol tower T140 condensed by the methanol tower condenser E1401 is divided into two parts, one part is used as reflux liquid 25 and directly returned to the top of the methanol tower T140, and the other part of the condensate 26 enters the upper part of the high-pressure tower T120; the material in the bottom of the methanol tower T140 is sent out of the device as a methanol product 27.
According to the process provided by the invention, the typical raw material composition of the crude dimethyl carbonate is as follows:
the above ranges of raw material composition do not constitute any limitation to the present invention, which is applicable to the rectification of crude dimethyl carbonate raw material of various compositions.
According to the process provided by the invention, the dimethyl carbonate and the methanol in the feed are completely separated, the purity of the dimethyl carbonate product can reach 99.99%, and the content of the dimethyl carbonate in the recovered methanol is lower than 0.1%. It should be noted that if the separation index is reduced, for example, the index is reduced to 99.9% of the purity of the dimethyl carbonate product, and the content of dimethyl carbonate in the recovered methanol is less than 0.5%, the process provided by the invention is easier to implement and the energy consumption for operation is lower. The variation of the separation index does not limit the present invention, and the corresponding deformation process provided by the present invention can be adopted according to the specific separation index requirement, and persons in the related field can completely implement the technology by appropriately changing or changing and combining the methods provided by the present invention. It is expressly stated that all such modifications or alterations and subcombinations which would be apparent to persons skilled in the art by making similar changes or variations to the process flow provided by the present invention are deemed to be within the spirit, scope and content of the invention.
Example 1:
as shown in fig. 1, crude dimethyl carbonate feed 1 enters a light ends removal column T110.
The gas phase 2 at the top of the light and heavy component removal tower T110 is condensed by a condenser E1101 of the light and heavy component removal tower, the condensate (3) is directly returned to the top of the light and heavy component removal tower T110 as reflux liquid, the non-condensable gas 4 is condensed and cooled by a light component condenser E1102, and the condensate 5 is sent out of the device as light components; a liquid phase material 6 is extracted from the upper side line of the light and heavy component removal tower T110 and enters a high pressure tower T120; and the liquid phase material in the bottom of the light and heavy component removing tower T110 is taken as the first heavy component 7 and sent out of the device.
The high-pressure tower T120, a light and heavy component removal tower T110 and a methanol tower T140 are subjected to heat integration operation, a gas phase 8 at the top of the high-pressure tower T120 is divided into two parts 9 and 11, the gas phase 9 enters a shell pass of a light and heavy component removal tower reboiler E1103, the gas phase 11 enters a shell pass of a methanol tower reboiler E1402, a condensate 10 obtained by condensing the gas phase 9 at the top of the tower and a condensate 12 obtained by condensing the gas phase 11 at the top of the tower are mixed to obtain a condensate 13, the condensate 13 is divided into two strands, one strand is used as a reflux 14 and directly returned to the top of the high-pressure tower T120, and the other strand of; the bottoms 16 of the high-pressure column T120 enter the feed side L130 of the dimethyl carbonate rectification column T130.
The dimethyl carbonate rectifying tower T130 and the methanol tower T140 are subjected to heat integration operation, gas phase 17 at the top of the dimethyl carbonate rectifying tower T130 enters a shell pass of a reboiler E1403 of the methanol tower, condensate 18 obtained after condensation of the gas phase 17 at the top of the methanol tower is divided into two parts, one part is used as reflux liquid 19 and directly returns to the top of the dimethyl carbonate rectifying tower T130, and the other part of condensate 20 enters a high-pressure tower T120; the material collected from the side line R130 at the collecting side of the dimethyl carbonate rectifying tower T130 is sent out of the device as a dimethyl carbonate product 21; the material in the bottom of the dimethyl carbonate rectifying tower T130 is taken as a second heavy component 22 and sent out of the device.
The condensate 24 of the gas phase 23 at the top of the methanol tower T140 condensed by the methanol tower condenser E1401 is divided into two parts, one part is used as reflux liquid 25 and directly returned to the top of the methanol tower T140, and the other part of the condensate 26 enters the upper part of the high-pressure tower T120; the material in the bottom of the methanol tower T140 is sent out of the device as a methanol product 27.
The heat source used by the high-pressure tower reboiler E1201 and the dimethyl carbonate rectifying tower reboiler E1301 can be fresh steam, heat conducting oil or material steam generated inside the system.
The condensate of the fresh steam added into the system can be used for feeding and preheating the materials for each tower respectively or successively.
The preferred operating conditions for each column in example 1 are given below:
the operation pressure of the top of the light and heavy component removal tower T110 is 80-190 kpa, the operation temperature of the top of the tower is 35-70 ℃, and the operation temperature of a tower kettle is 85-110 ℃;
the operation pressure of the top of the high-pressure tower T120 is 700-1100 kPa, the operation temperature of the top of the tower is 115-135 ℃, and the operation temperature of the bottom of the tower is 160-180 ℃;
the operating pressure of the top of the dimethyl carbonate rectifying tower T130 is 100-300 kPa, the operating temperature of the top of the tower is 60-130 ℃, and the operating temperature of the bottom of the tower is 110-135 ℃;
the operation pressure of the top of the methanol tower T140 is 80-150 kpa, the operation temperature of the top of the tower is 55-75 ℃, and the operation temperature of the bottom of the tower is 58-82 ℃.
One typical operating condition and operating energy consumption for each column in example 1 is given below:
the operation pressure at the top of the light and heavy component removal tower T110 is 150kpa, the temperature at the top of the tower is 47 ℃, and the temperature at the bottom of the tower is 99 ℃;
the operation pressure at the top of the high-pressure tower T120 is 800kpa, the temperature at the top of the tower is 127 ℃, and the temperature at the bottom of the tower is 173 ℃;
the operation pressure at the top of the dimethyl carbonate rectifying tower T130 is 235kpa, the top of the tower is 118 ℃, and the temperature of a tower kettle is 122 ℃;
the operation pressure of the top of the methanol tower T140 is 101kpa, the temperature of the top of the tower is 62 ℃, and the temperature of a tower kettle is 66 ℃;
the whole rectifying system only needs medium-pressure steam heating in the high-pressure tower T120 and needs low-pressure steam heating in the dimethyl carbonate rectifying tower T130, so that the operation energy consumption is greatly reduced. According to a 5 ten thousand tons/year dimethyl carbonate rectifying device, the operation time is 8000 hours/year, the yield of the dimethyl carbonate is 6.25 tons/hour, and the total steam consumption is only 18 tons/hour. The energy required by other reboilers and heat exchangers can utilize the energy in the system.
According to the same production scale, the three-tower rectification process method provided by the Chinese patent CN108299204A is adopted, and the operation energy consumption of the rectification system is 58 tons/hour of steam.
(58-18)/58≈69%
Compared with the three-tower rectification process method provided by the Chinese patent CN108299204A, the energy consumption of the process method provided by the invention shown in the figure 1 is reduced by about 69 percent.
Steam can be saved by 58-18 tons/hour to 40 tons/hour.
The medium pressure steam can be saved by 40 tons/hour multiplied by 8000 hours/year which is 320000 tons/year.
The steam cost can be saved by 150 yuan per ton of steam each year:
320000 ton/year × 150 yuan/ton/10000 ═ 4800 ten thousand yuan/year.
The energy-saving process method and the device for purifying the dimethyl carbonate by the four-tower heat integration rectification have extremely remarkable economic benefit and wide application prospect.
Example 2:
as shown in fig. 2, it is an evolution process of fig. 1, and the difference from the process shown in fig. 1 is that:
in the four-column heat integration shown in fig. 1, the dimethyl carbonate rectification column T130 can be omitted, the high-pressure column T120 adopts a baffle column structure, the dimethyl carbonate product 21 is fed from one side of the baffle, the dimethyl carbonate product 21 is extracted from the other side of the baffle, and the second heavy component 22 is discharged from the bottom of the column.
Example 3:
as shown in fig. 3, it is an evolution process of fig. 1, and the difference from the process shown in fig. 1 is that:
in the four-tower heat integration shown in fig. 1, a light and heavy component removing tower T110 can be omitted, a raw material 1 directly enters a high-pressure tower T120, light components 5 are extracted from the top of the high-pressure tower T120, a mixture of dimethyl carbonate and methanol 15 is extracted from the upper side line of the high-pressure tower T120 to form an methanol removing tower T140, and a crude dimethyl carbonate product 16 which does not contain methanol basically is obtained from the bottom of the tower to form a dimethyl carbonate rectifying tower T130.
Example 4:
as shown in fig. 4, it is an evolution process of fig. 1, and the difference from the process shown in fig. 1 is that:
in the four-tower heat integration shown in fig. 1, a high-pressure tower T120 and a dimethyl carbonate rectifying tower T130 can be omitted, a light and heavy component removing tower T110 adopts a partition plate tower structure, a raw material 1 is fed from one side of a partition plate, a dimethyl carbonate product 21 is extracted from the other side of the partition plate, a light component 5 is extracted from the top of the tower, a mixture material of dimethyl carbonate and methanol is extracted from the upper side line, a methanol removing tower T140 is extracted, and a first heavy component 7 is discharged from the bottom of the tower; the mixture 26 of dimethyl carbonate and methanol is extracted from the top of the methanol tower T140 and returns to the light and heavy component removing tower T110 for feeding, and the methanol tower T140 obtains a recovered methanol product 27.
Example 5:
as shown in fig. 5, it is an evolution process of fig. 1, and the difference from the process shown in fig. 1 is that:
in the four-column heat integration shown in fig. 1, the light and heavy component removal column T110 adopts a baffle column structure, and the material is fed from a baffle feeding side L110, and the material 6 is extracted from a baffle extraction side R110 and sent to a high pressure column T120.
Example 6:
as shown in fig. 6, it is an evolution process of fig. 5, and the difference from the process shown in fig. 5 is that:
in the four-tower heat integration shown in fig. 5, the light and heavy component removal tower T110 adopts a partition tower structure, two side streams can be extracted, and a liquid phase side stream (a mixture of dimethyl carbonate and methanol) material 6 is extracted above the partition section of the light and heavy component removal tower T110 and is fed to the upper part of the high pressure tower T120; another liquid phase side line (dimethyl carbonate crude product containing substantially no methanol) 29 is taken from the clapboard section of the light and heavy component removal tower T110 and is sent to the middle lower part of a high-pressure tower T120.
Example 7:
as shown in fig. 7, it is an evolution process of fig. 6, and the difference from the process shown in fig. 6 is that:
in the four-column heat integration shown in fig. 6, the high pressure column T120 can be omitted, and a liquid phase side stream (dimethyl carbonate and methanol mixture) material 6 methanol removing column T140 is taken above the partition section of the light and heavy component removing column T110; the light component removal tower T110 baffle section produces another liquid phase side line (dimethyl carbonate crude product which does not contain methanol basically) 29 to remove dimethyl carbonate rectifying tower T130 baffle feed side L130.
Example 8:
as shown in fig. 8, it is an evolution process of fig. 1, and the difference from the process shown in fig. 1 is that:
in the four-tower heat integration shown in fig. 1, when the requirement for recovering methanol is not high, the methanol tower T140 can be omitted, and the recovered methanol 27 is extracted from the bottom of the light and heavy component removal tower T110 instead.
Example 9:
as shown in fig. 9, it is an evolution process of fig. 1, and the difference from the process shown in fig. 1 is that:
in the four-tower heat integration shown in fig. 1, the gas phase at the top of the high-pressure tower T120 does not heat the bottom of the methanol tower T140 any more, and the energy required by the reboiler at the bottom of the light and heavy component removal tower T110 is provided by the gas phase at the top of the high-pressure tower T120; the energy required by the reboiler at the bottom of the methanol tower T140 is provided by the gas phase at the top of the dimethyl carbonate rectifying tower T130.
The invention provides an energy-saving process method and an energy-saving device for purifying dimethyl carbonate by adopting four-tower heat integration, which are an energy-saving process method and an energy-saving device for producing a high-purity dimethyl carbonate product and a byproduct methanol product from a crude dimethyl carbonate raw material by adopting a four-tower heat integration device through a rectification process. The whole device at least comprises four towers of a light and heavy component removing tower T110, a high-pressure tower T120, a dimethyl carbonate rectifying tower T130, a methanol tower T140 and the like and matched equipment thereof. The invention adopts a multi-tower heat integration process method, can overcome the defects of the prior art, greatly reduces the operation energy consumption, has obvious practicability and economic benefit and has wide application prospect.
Persons skilled in the relevant art can implement the technology by making appropriate changes or modifications and combinations according to the methods provided by the invention. It is expressly stated that all such modifications or alterations and subcombinations which would be apparent to persons skilled in the art by making similar changes or variations to the process flow provided by the present invention are deemed to be within the spirit, scope and content of the invention.

Claims (10)

1. An energy-saving process method for purifying dimethyl carbonate by adopting four-tower heat integration is characterized by comprising the following steps:
1) at least comprises a light component removing tower (T110), a high pressure tower (T120), a dimethyl carbonate rectifying tower (T130) and a methanol tower (T140);
2) the light and heavy component removal tower (T110) adopts a conventional rectifying tower or a clapboard tower; withdrawing light components from the top of the tower, withdrawing first heavy components from the bottom of the tower, and feeding the side materials to a high-pressure tower (T120);
3) the high-pressure tower (T120) is pressurized, a methanol removing tower (T140) for removing the mixture of the dimethyl carbonate and the methanol is extracted from the top of the tower, and a rectifying tower (T130) for removing the dimethyl carbonate from the dimethyl carbonate crude product which does not contain the methanol basically is obtained from the bottom of the tower;
4) the dimethyl carbonate rectifying tower (T130) preferably adopts a clapboard tower, feeding is carried out from one side of a clapboard, a dimethyl carbonate product is extracted from the other side of the clapboard, and a mixture of dimethyl carbonate and methanol is extracted from the top of the tower; or returned to the higher pressure column (T120) feed, or fed methanol column (T140); extracting a second heavy component from the tower kettle;
5) the methanol tower (T140) is typically operated at normal pressure, and a mixture of dimethyl carbonate and methanol is extracted from the top of the tower and returned to the upper part of the high-pressure tower (T120), or returned to the upper part of the light and heavy component removal tower (T110), or returned to the feed of the high-pressure tower (T120); the methanol tower (T140) obtains a recovered methanol product at the tower bottom; recovering methanol or withdrawing methanol from the lower side of the methanol column (T140);
6) the light and heavy component removal tower (T110), the high-pressure tower (T120), the dimethyl carbonate rectifying tower (T130) and the methanol tower (T140) are thermally integrated, and a typical thermal integration mode is as follows: the energy required by a reboiler at the tower bottom of the light and heavy component removal tower (T110) is provided by the gas phase at the top of the high-pressure tower (T120); the energy required by the reboiler at the tower bottom of the methanol tower (T140) is respectively provided by the gas phase at the tower top of the high-pressure tower (T120) and the gas phase at the tower top of the dimethyl carbonate rectifying tower (T130); the high-pressure tower (T120) and the dimethyl carbonate rectifying tower (T130) adopt external heat sources for heating;
7) the dimethyl carbonate and the methanol in the feed are completely separated, the purity of the dimethyl carbonate product reaches 99.99 percent, and the content of the dimethyl carbonate in the recovered methanol is lower than 0.1 percent.
2. The process as claimed in claim 1, wherein the dimethyl carbonate rectification column (T130) is omitted, the high-pressure column (T120) is of a dividing wall column structure, the feed is taken from one side of the dividing wall, the dimethyl carbonate product is taken from the other side of the dividing wall, and the second heavy component is discharged from the bottom of the column.
3. The process according to claim 1, wherein said light ends removal column (T110) is omitted, the raw material is fed directly into the high pressure column (T120), the light ends are taken from the top of the high pressure column (T120), the mixture of dimethyl carbonate and methanol is taken from the upper side of the high pressure column (T120) to form a methanol removal column (T140), and the crude dimethyl carbonate substantially free of methanol is obtained from the bottom of the column to form a rectification column (T130) for removing dimethyl carbonate.
4. The process according to claim 1, wherein the high pressure column (T120) and the dimethyl carbonate rectification column (T130) are omitted, the light and heavy component removal column (T110) is of a baffled column structure, raw materials are fed from one side of a baffle plate, a dimethyl carbonate product is taken from the other side of the baffle plate, light components are taken from the top of the column, a methanol removal column (T140) of a mixture of dimethyl carbonate and methanol is taken from the upper side line, and a first heavy component is discharged from the bottom of the column; the mixture of dimethyl carbonate and methanol is extracted from the top of the methanol tower (T140) and returns to the light and heavy component removing tower (T110) for feeding, and the methanol tower (T140) obtains a recovered methanol product at the tower bottom; or when the methanol content in the feed is low, the light component removing tower (T110), the high-pressure tower (T120) and the methanol tower (T140) are omitted, the raw material directly enters the feed side of a clapboard of a dimethyl carbonate rectifying tower (T130), the light component is extracted from the top of the tower, the first heavy component is extracted from the bottom of the tower, and the dimethyl carbonate product is extracted from the other side of the clapboard.
5. The process according to claim 1, characterized in that the light ends and heavy ends removal column (T110) is a conventional rectification column or a dividing wall column; if the light and heavy component removal tower (T110) adopts a conventional rectifying tower, the materials are laterally extracted from the position above the feeding material or below the feeding material and sent to a high-pressure tower (T120); if the light and heavy component removal tower (T110) adopts a clapboard tower, feeding is carried out from one side of the clapboard, and materials are extracted from the other side of the clapboard and sent to the high-pressure tower (T120).
6. The process according to claim 1 or 5, characterized in that when a dividing wall column is used as the light and heavy component removal column (T110), two side streams are taken, and a liquid phase side stream of the mixture of dimethyl carbonate and methanol is taken from the upper part of the high pressure column (T120) above the dividing wall section of the light and heavy component removal column (T110); the other liquid phase side line is extracted from the clapboard section of the light and heavy component removing tower (T110), and the dimethyl carbonate crude product which does not contain methanol basically enters the middle lower part of the high-pressure tower (T120) or enters the middle part of the dimethyl carbonate rectifying tower (T130).
7. Process according to claim 6, characterized in that the high-pressure column (T120) is omitted and a liquid-phase side stream (mixture of dimethyl carbonate and methanol) methanol removal column (T140) is taken above the partition section of the light and heavy components removal column (T110); the other liquid phase side line is extracted from the clapboard section of the light and heavy component removing tower (T110), and the dimethyl carbonate crude product which does not contain methanol basically removes the feeding side of the clapboard of the dimethyl carbonate rectifying tower (T130).
8. The process according to claim 1, characterized in that when the requirement for methanol recovery is not high, the methanol column (T140) is omitted and the methanol recovery is instead taken from the bottom of the light and heavy components removal column (T110).
9. The process according to claim 1, characterized in that the typical operating conditions of the columns are:
the operation pressure range of the top of the light and heavy component removal tower (T110) is 30-300 kPa;
the operation pressure range of the top of the high-pressure tower (T120) is 500-1500 kPa;
the operating pressure range of the top of the dimethyl carbonate rectifying tower (T130) is 80-600 kPa;
the operating pressure range of the top of the methanol tower (T140) is 30-400 kPa;
the operating conditions of each column were:
the operation pressure at the top of the light and heavy component removal tower (T110) is 80-190 kpa, the operation temperature at the top of the tower is 35-70 ℃, and the operation temperature at the bottom of the tower is 85-110 ℃;
the operation pressure of the top of the high-pressure tower (T120) is 700-1100 kPa, the operation temperature of the top of the tower is 115-135 ℃, and the operation temperature of the bottom of the tower is 160-180 ℃;
the operating pressure at the top of the dimethyl carbonate rectifying tower (T130) is 100-300 kPa, the operating temperature at the top of the tower is 60-130 ℃, and the operating temperature at the bottom of the tower is 110-135 ℃;
the operating pressure at the top of the methanol tower (T140) is 80-150 kpa, the operating temperature at the top of the tower is 55-75 ℃, and the operating temperature at the bottom of the tower is 58-82 ℃.
10. The utility model provides an adopt four tower heat integrations to carry out economizer of dimethyl carbonate purification which characterized in that: mainly comprises four towers of a light component removal tower (T110), a high-pressure tower (T120), a dimethyl carbonate rectifying tower (T130), a methanol tower (T140) and a connecting pipeline;
a raw material crude dimethyl carbonate feed pipeline is connected to the middle part of a light and heavy component removal tower (T110);
the top of the light and heavy component removal tower (T110) is connected with a condenser (E1101) of the light and heavy component removal tower, a condensate outlet of the condenser (E1101) of the light and heavy component removal tower is connected with the top of the light and heavy component removal tower (T110), a noncondensable gas outlet of the condenser (E1101) of the light and heavy component removal tower is connected with a light component condenser (E1102), and a condensate outlet of the light component condenser (E1102) is connected with a light component extraction pipeline; a side draw outlet at the upper part of the light and heavy component removal tower (T110) is connected with the middle part of the high-pressure tower (T120); the bottom of the light and heavy component removal tower (T110) is respectively connected with a tube side inlet of a reboiler (E1103) of the light and heavy component removal tower and a heavy component 1 extraction pipeline, and a tube side outlet of the reboiler (E1103) of the light and heavy component removal tower is connected to a tower kettle of the light and heavy component removal tower (T110);
the top of the high-pressure tower (T120) is respectively connected with the shell pass of a light and heavy component removal tower reboiler (E1103) and the shell pass of a methanol tower reboiler A (E1402), a shell pass condensate pipeline of the light and heavy component removal tower reboiler (E1103) is converged with a shell pass condensate pipeline of the methanol tower reboiler A (E1402) to form a top condensate pipeline of the high-pressure tower (T120), and the pipelines are respectively connected with the top of the high-pressure tower (T120) and the middle of the methanol tower (T140); the bottom of the high-pressure tower (T120) is respectively connected with a tube pass inlet of a reboiler (E1201) of the high-pressure tower and the middle part of the feed side (L130) of the dimethyl carbonate rectifying tower (T130), and a tube pass outlet of the reboiler (E1201) of the high-pressure tower is connected to the tower kettle of the high-pressure tower (T120);
the top of the dimethyl carbonate rectifying tower (T130) is connected with the shell pass of a methanol tower reboiler B (E1403), and the shell pass condensate outlet of the methanol tower reboiler B (E1403) is respectively connected with the top of the dimethyl carbonate rectifying tower (T130) and the middle of a high-pressure tower (T120); a side line withdrawing port of a withdrawing side (R130) of the dimethyl carbonate rectifying tower (T130) is connected with a dimethyl carbonate product withdrawing pipeline; the bottom of the dimethyl carbonate rectifying tower (T130) is respectively connected with a tube pass inlet of a reboiler (E1301) of the dimethyl carbonate rectifying tower and a heavy component 2 extraction pipeline, and a tube pass outlet of the reboiler (E1301) of the dimethyl carbonate rectifying tower is connected to the tower kettle of the dimethyl carbonate rectifying tower (T130);
the top of the methanol tower (T140) is connected with a methanol tower condenser (E1401), and the condensate outlet of the methanol tower condenser (E1401) is respectively connected with the top of the methanol tower (T140) and the upper part of the high-pressure tower (T120); the bottom of the methanol tower (T140) is respectively connected with a tube side inlet of a methanol tower reboiler (E1402), a tube side inlet of the methanol tower reboiler (E1403) and a methanol extraction pipeline, and a tube side outlet of the methanol tower reboiler (E1402) and a tube side outlet of the methanol tower reboiler (E1403) are both connected to a tower kettle of the methanol tower (T140).
CN202010180483.3A 2020-03-16 2020-03-16 Energy-saving process method and device for purifying dimethyl carbonate by adopting four-tower heat integration Pending CN111170863A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113372222A (en) * 2021-05-20 2021-09-10 山东华鲁恒升化工股份有限公司 Method for separating coal-to-ethylene glycol coupling esterification process by-product

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113372222A (en) * 2021-05-20 2021-09-10 山东华鲁恒升化工股份有限公司 Method for separating coal-to-ethylene glycol coupling esterification process by-product

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