CN211896734U - Energy-saving process device for purifying dimethyl carbonate by adopting four-tower heat integration - Google Patents
Energy-saving process device for purifying dimethyl carbonate by adopting four-tower heat integration Download PDFInfo
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Abstract
The utility model relates to an adopt four tower heat integration to carry out energy-conserving process units of dimethyl carbonate purification, adopt four tower heat integration device to produce high-purity dimethyl carbonate product and byproduct methyl alcohol product through the rectification process from thick dimethyl carbonate raw materials. 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 utility model discloses a baffle tower structure and many towers heat integration process method effectively overcome prior art's defect, reduce the operation energy consumption by a wide margin, have apparent practicality and economic benefits, application prospect is wide.
Description
Technical Field
The utility model relates to an adopt four tower heat integration to carry out energy-conserving process units of dimethyl carbonate purification, it is an adopt four tower heat integration device to produce the energy-conserving process methods and the device of high-purity dimethyl carbonate product and byproduct methyl alcohol product through the rectification process from thick dimethyl carbonate raw materials.
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 is that according to CN108299204A, in step 1 of the embodiment, "the mixture of about 54% of methanol in the bottom, about 45% of dimethyl carbonate and about 1% of water in the bottom of the light component removal tower" returns to the intermediate tank area ", and in step 1 of the embodiment," enters the crude DMC rectification tower 2, 80% of methanol, 20% of dimethyl carbonate and trace amount of low boiling point fraction are discharged from the top of the tower after rectification ", both indicate that the separation method provided by CN108299204A does not completely separate dimethyl carbonate from methanol, a large amount of dimethyl carbonate is lost in 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
An object of the utility model is to provide an energy-conserving process units of dimethyl carbonate rectification purification, it is an energy-conserving process methods and the device that adopts four tower heat integrated device to produce high-purity dimethyl carbonate product and byproduct methyl alcohol product through the rectification process from thick dimethyl carbonate raw materials, can overcome prior art's defect, reduces the operation energy consumption by a wide margin, has apparent practicality and economic benefits, and application prospect is wide.
The energy-saving process method for purifying dimethyl carbonate by adopting four-tower heat integration 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 utility model, as shown in the attached figure 1, 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 A 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, and; 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 operated in a heat integration mode, gas phase 17 at the top of the dimethyl carbonate rectifying tower T130 enters a shell pass of a methanol tower reboiler B E1403, condensate 18 obtained after condensation of the gas phase 17 at the top of the 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 utility model, besides the four-tower heat integration rectification and purification of the dimethyl carbonate, the process method can also be transformed into other heat integration processes for rectifying and purifying the dimethyl carbonate.
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; 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.
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 utility model provides a process, high-pressure tower T120 tower cauldron methyl alcohol content typical operating range 0.01 ~ 6% (except special explanation, all indicate mass percent in this description the high-pressure tower T120 tower cauldron methyl alcohol content does not constitute the utility model discloses any restriction.
According to the utility model provides a technological method, the heat integration mode between four towers can also be: 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 utility model provides a technological method, the heat integration mode between four towers can also be: 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 utility model provides a technological method can set up intermediate heat exchanger or circulative cooling section between taking off light heavy ends tower T110 top of the tower and the 6 positions of upper portion siding extraction liquid phase material for the ascending gas of part condensation reduces top of the tower condenser heat load. According to the utility model provides a process, when heavy ends content was higher in the feeding, can add the dimethyl carbonate recovery tower for take off the recovery of dimethyl carbonate in the light ends tower T110 tower cauldron ejection of compact, and the purification of heavy ends material. According to the utility model provides a technological method, when light component content was higher in the feeding, can add the light component enrichment tower for take off light and heavy components tower T110 top of the tower ejection of compact dimethyl carbonate's recovery to and light component's concentration. 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 evolution processes formed thereby should be considered 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 aforesaid heat transfer method is only the utility model provides a further energy-conserving auxiliary means of process does not constitute right the utility model discloses an any restriction, the technical personnel in relevant professional field can implement the inside commodity circulation heat transfer method of suitable system according to concrete device condition completely, and the various evolution process flows that form from this all should be regarded as in the spirit, scope and the content of the utility model.
According to the utility model provides a process, the used external heat source of high-pressure column reboiler E1201 and dimethyl carbonate rectifying column reboiler E1301 can be live steam, conduction oil, perhaps the inside material steam that produces of system.
According to the process provided by the utility model, the typical operation 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.
Except for the special description, all pressures in the present invention refer to absolute pressures.
According to the process provided by the utility model, 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 utility model provides a pair of adopt four tower heat integration to carry out energy-conserving process units of dimethyl carbonate purification, it is mainly including taking off four towers and connecting line of light heavy ends tower T110, high-pressure column T120, dimethyl carbonate rectifying column T130, methanol column T140:
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 A E1402 shell pass, a light and heavy component removal tower reboiler E1103 shell pass condensate pipeline is converged with a methanol tower reboiler A E1402 shell pass condensate pipeline 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 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 part of the 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 A E1402, a tube side inlet of a methanol tower reboiler B E1403 and a methanol extraction pipeline, and a tube side outlet of the methanol tower reboiler A E1402 and a tube side outlet of the methanol tower reboiler B E1403 are both connected to the tower bottom of the methanol tower T140.
The utility model provides an adopt four tower heat integration to carry out energy-conserving process units of dimethyl carbonate purification, it is an adopt four tower heat integration device to produce the energy-conserving process methods and the device of high-purity dimethyl carbonate product and byproduct methyl alcohol product through the rectification process from thick dimethyl carbonate raw materials. 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 utility model discloses a many towers heat integration process method can overcome prior art's defect, reduces the operation energy consumption by a wide margin, has apparent practicality and economic benefits, and application prospect is wide.
Drawings
FIG. 1 is a process flow diagram of a typical four-tower heat integration device for rectification and purification of dimethyl carbonate.
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 provided for illustration purposes and are not intended to limit 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 utility model provides an energy-conserving processing method that adopts four tower heat integrated device to carry out methyl carbonate rectification purification includes following step:
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.
According to the utility model provides a process method, concrete step is:
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 A 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, and; 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 operated in a heat integration mode, gas phase 17 at the top of the dimethyl carbonate rectifying tower T130 enters a shell pass of a methanol tower reboiler B E1403, condensate 18 obtained after condensation of the gas phase 17 at the top of the 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 utility model, the typical raw material composition of the crude dimethyl carbonate is as follows:
the component names and the mass percentages
Dimethyl carbonate 59.8
Methanol 29.9
Methyl formate 5.1
Methylal 2.9
Water 0.29
Heavy component 1.01
Total of 100.00
The composition range of the raw materials does not form any limit to the utility model, and the utility model can be used for the rectification of the raw material of the coarse dimethyl carbonate with various compositions.
According to the process provided by the utility model, 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. 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 lower than 0.5%, the process provided by the utility model is easier to realize, and the energy consumption for operation is lower. Above-mentioned separation index change does not constitute right the utility model discloses an any restriction can require to adopt according to concrete separation index the utility model provides a corresponding deformation flow, personnel in relevant field can be according to completely the utility model provides a method carries out appropriate change or change and combination, realizes this technique. It is expressly stated that all such modifications or variations and rearrangements of the process flow provided by the present invention as would be obvious to one skilled in the art 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.
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 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 A 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 condensate; 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 operated in a heat integration mode, gas phase 17 at the top of the dimethyl carbonate rectifying tower T130 enters a shell pass of a methanol tower reboiler B E1403, condensate 18 obtained after condensation of the gas phase 17 at the top of the 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 utility model shown in the figure 1 is reduced by about 69%.
Steam can be saved 58-18=40 tons/hour per 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 utility model provides an energy-conserving processing method and device of four tower heat integration rectification purification dimethyl carbonate, it has very showing economic benefits, and application prospect is wide.
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 utility model provides an energy-saving process method and device for purifying dimethyl carbonate by adopting four-tower heat integration, which is an energy-saving process method and device for producing high-purity dimethyl carbonate products and byproduct methanol products by adopting four-tower heat integration devices through a rectification process from raw dimethyl carbonate raw materials. 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 utility model discloses a many towers heat integration process method can overcome prior art's defect, reduces the operation energy consumption by a wide margin, has apparent practicality and economic benefits, and application prospect is wide.
Persons skilled in the relevant art can implement the technology by making appropriate changes or modifications and combinations according to the method provided by the present invention. It is expressly stated that all such modifications or variations and rearrangements of the process flow provided by the present invention as would be obvious to one skilled in the art are deemed to be within the spirit, scope and content of the invention.
Claims (7)
1. An energy-saving process device for purifying dimethyl carbonate by adopting four-tower heat integration is characterized by comprising 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;
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 A (E1402), a tube side inlet of a methanol tower reboiler B (E1403) and a methanol extraction pipeline, and a tube side outlet of the methanol tower reboiler A (E1402) and a tube side outlet of the methanol tower reboiler B (E1403) are both connected to a tower kettle of the methanol tower (T140).
2. The process installation according to claim 1, wherein the dimethyl carbonate rectification column (T130) is omitted and the high-pressure column (T120) is of a dividing wall column construction.
3. The process installation according to claim 1, characterized in that the light ends removal column (T110) is omitted and the feed is fed directly to the high-pressure column (T120) so that light ends are taken off from the top of the high-pressure column (T120), the mixture of dimethyl carbonate and methanol is taken off from the upper side of the column (T120) to form a methanol removal column (T140), and crude dimethyl carbonate substantially free of methanol is taken off from the bottom of the column to form a rectification column (T130) for removing dimethyl carbonate.
4. The process unit as claimed in 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 bottom of the tower.
5. A process unit 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.
6. The process unit as claimed in claim 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 mixture of dimethyl carbonate and methanol with a liquid phase side stream is taken above the dividing wall section of the light and heavy component removal column (T110) and is sent to the upper part of the high-pressure column (T120); 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 plant according to claim 1, characterized in that the methanol column (T140) is omitted so that the recovered methanol is instead taken from the bottom of the light ends and heavy ends removal column (T110).
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