Equipment and process for purifying dimethyl carbonate

Abstract

The invention discloses dimethyl carbonate purification equipment and a dimethyl carbonate purification process. The dimethyl carbonate purification equipment comprises an extraction device, a refining device and a crystallization device, the extraction device comprises an extraction tower and a first reboiler with a first heating medium cavity, and the extraction tower is used for extracting and purifying the dimethyl carbonate crude product to obtain a primary purified product; the refining device comprises a refining tower communicated with the extraction tower to obtain a secondary purified product, and a tower kettle of the refining tower is provided with a high-temperature waste outlet communicated with the first heating medium cavity; the crystallization device comprises a crystallizer, a precooler and a lithium bromide absorption refrigerator, and the lithium bromide absorption refrigerator is communicated with the tower top of the refining tower, so that heat energy generated by liquefying vapor discharged from the tower top of the refining tower is used as a heat source of the lithium bromide absorption refrigerator. According to the dimethyl carbonate purification equipment and the purification process thereof, the electronic-grade dimethyl carbonate can be prepared, and the energy consumption in the purification process is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of separation and purification of dimethyl carbonate, and specifically relates to a purification device and a purification process of dimethyl carbonate. Background Art

[0002] Dimethyl carbonate (DMC) is a colorless, transparent, slightly odorous, slightly sweet liquid that is insoluble in water, but miscible with almost all organic solvents such as alcohols, ethers, and ketones. DMC has very low toxicity and is an environmentally friendly chemical raw material that meets the requirements of modern "clean processes." As a chemical intermediate, DMC can replace phosgene as a carbonylating agent and dimethyl sulfate (DMS) as a methylating agent. In addition, DMC can be used in lithium battery electrolytes as a low-toxic and excellent solvent. With the rapid development of new energy vehicles, its demand has greatly increased. Driven by the development of new energy vehicles, the demand for electrolyte solvents has become the largest downstream of dimethyl carbonate. DMC used in lithium battery electrolytes has higher requirements for its purity than other applications. Electronic grade dimethyl carbonate requires a purity of more than 99.99wt%.

[0003] The existing purification process of dimethyl carbonate generally involves distillation, extraction and other purification processes on the crude dimethyl carbonate synthesized by oxidative carbonylation of methanol to obtain dimethyl carbonate with higher purity; however, the existing process either obtains dimethyl carbonate with a purity of less than 99.99wt%, or requires repeated distillation, extraction and other purification methods to obtain electronic grade dimethyl carbonate, which consumes a lot of energy.

[0004] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0005] The object of the present invention is to provide a purification device for dimethyl carbonate and a purification process thereof, which can produce electronic grade dimethyl carbonate and reduce energy consumption in the purification process.

[0006] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows: a purification device for dimethyl carbonate, comprising:

[0007] An extraction device, comprising an extraction tower and a first reboiler for heating a substance in the extraction tower, wherein the first reboiler has a first heat medium chamber for accommodating a heat medium, and the extraction tower is used to extract and purify a crude dimethyl carbonate product to obtain a primary purified product containing an extractant and dimethyl carbonate;

[0008] A refining device, comprising a refining tower connected to the extraction tower, the refining tower is used to purify the primary purification product to obtain a secondary purification product, the tower kettle of the refining tower has a high-temperature waste outlet, the high-temperature waste outlet is connected to the first heat medium chamber, and is used to use the high-temperature waste discharged from the tower kettle of the refining tower as a heat medium for heating the first heat medium chamber;

[0009] The crystallization device comprises a crystallizer connected to the refining tower, a precooler connected between the refining tower and the crystallizer, and a lithium bromide absorption refrigerator for providing a cold source to the precooler, wherein the precooler is used to cool the secondary purification product transported from the refining tower to the crystallizer, the lithium bromide absorption refrigerator is connected to the top of the refining tower so as to use the heat energy generated by the liquefaction of the gas discharged from the top of the refining tower as the heat source of the lithium bromide absorption refrigerator, and the crystallizer is used to crystallize and sweat the secondary purification product to obtain electronic grade dimethyl carbonate.

[0010] In one or more embodiments of the present invention, the extraction device further comprises an extraction tower preheater connected to the extraction tower, wherein the crude dimethyl carbonate is preheated by the extraction tower preheater before entering the extraction tower.

[0011] In one or more embodiments of the present invention, the extraction tower preheater has a second heat medium chamber for accommodating heat medium, which is used to heat the crude dimethyl carbonate in the extraction tower preheater.

[0012] In one or more embodiments of the present invention, the high-temperature waste includes an extractant, and the second heat medium chamber of the extraction tower preheater is connected to the extraction tower for adding the heat medium in the second heat medium chamber into the extraction tower.

[0013] In one or more embodiments of the present invention, the extraction device further comprises an extraction reflux tank, the top of the extraction tower comprises a first vapor outlet and a first reflux inlet respectively connected to the extraction reflux tank, and a first condenser is connected between the first vapor outlet and the extraction reflux tank.

[0014] In one or more embodiments of the present invention, the refining device also includes a refining reflux tank connected between the lithium bromide absorption refrigerator and the refining tower, and the top of the refining tower has a second vapor outlet and a second reflux inlet, the second vapor outlet is connected to the lithium bromide absorption refrigerator, and the second reflux inlet is connected to the refining reflux tank.

[0015] In one or more embodiments of the present invention, the crystallizer has a crystallization mother liquor outlet, and the crystallization mother liquor outlet is connected to the refining tower to transport the crystallization mother liquor to the refining tower.

[0016] In one or more embodiments of the present invention, the purification equipment further comprises a finished product tank, which is connected to the crystallizer and is used to collect the electronic grade dimethyl carbonate in the crystallizer.

[0017] A specific embodiment of the present invention further provides a dimethyl carbonate purification process, based on the dimethyl carbonate purification equipment as described above, the dimethyl carbonate purification process comprises the following steps:

[0018] The crude dimethyl carbonate is subjected to extractive distillation by an extraction tower to obtain a primary purified product;

[0019] The primary purified product is refined by a refining tower to obtain a secondary purified product and high-temperature waste respectively;

[0020] The high-temperature waste is transported to the first heat medium chamber of the first reboiler and serves as the heat medium of the first reboiler;

[0021] The secondary purified product is crystallized and sweated by a crystallizer to obtain electronic grade dimethyl carbonate;

[0022] In the refining process, the heat energy generated by the liquefaction of the gas discharged from the top of the refining tower is used as the heat source of the lithium bromide absorption refrigerator, and the lithium bromide absorption refrigerator is used to provide a cold source for the precooler.

[0023] In one or more embodiments of the present invention, in the crystallization and sweating treatment, the crystallization temperature is 2-4°C, the crystallization time is 2-5h, the sweating temperature is 4-5°C, and the sweating time is 1-3h.

[0024] Compared with the prior art, the dimethyl carbonate purification equipment and purification process of the present invention, by conveying the high-temperature waste obtained from the refining tower kettle to the first heat medium chamber of the first reboiler as the heat medium for heating the first heat medium chamber, uses the industrial waste heat released from the liquefaction of the gas at the top of the refining tower as the heat source of the lithium bromide absorption refrigerator (that is, the heat source of the generator in the lithium bromide absorption refrigerator), thereby playing the role of reusing and recovering heat energy and reducing the energy consumption of the entire purification process; in addition, through the cooperation of the extraction tower, the refining tower and the crystallizer, electronic grade dimethyl carbonate is obtained, the multiple distillation process in the prior art is simplified, and the energy consumption of the entire purification process is also reduced, which can achieve a reduction of more than 10% in energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a schematic diagram of a purification device for dimethyl carbonate in an example of the present invention.

[0027] Description of main reference numerals:

[0028] 1. Extraction device; 11. Extraction tower; 12. First reboiler; 13. Extraction reflux tank; 14. First condenser; 15. Extraction tower preheater; 2. Refining device; 21. Refining tower; 22. Second reboiler; 23. Refining reflux tank; 24. Secondary purification product storage tank; 25. Second condenser; 3. Crystallization device; 31. Crystallizer; 32. Precooler; 33. Lithium bromide absorption refrigerator; 4. Finished product tank; 5. Driving pump. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0030] like Figure 1 As shown, a purification device for dimethyl carbonate in an example of the present invention comprises an extraction device 1, a refining device 2 and a crystallization device 3; the extraction device 1 comprises an extraction tower 11 and a first reboiler 12 for heating a substance in the extraction tower 11, the first reboiler 12 having a first heat medium cavity for accommodating a heat medium, the extraction tower 11 being used to extract and purify a crude dimethyl carbonate product to obtain a primary purified product containing an extractant and dimethyl carbonate; the refining device 2 comprises a refining tower 21 connected to the extraction tower 11, the refining tower 21 being used to purify the primary purified product to obtain a secondary purified product, the tower kettle of the refining tower 21 having a high-temperature waste outlet, the high-temperature waste outlet being connected to the first heat medium cavity, Used to use the high-temperature waste discharged from the bottom of the refining tower 21 as a heat medium for heating the first heat medium chamber; the crystallization device 3 includes a crystallizer 31 connected to the refining tower 21, a precooler 32 connected between the refining tower 21 and the crystallizer 31, and a lithium bromide absorption refrigerator 33 for providing a cold source to the precooler 32, the precooler 32 is used to cool the secondary purification product transported from the refining tower 21 to the crystallizer 31, the lithium bromide absorption refrigerator 33 is connected to the top of the refining tower 21, so as to use the heat energy generated by the liquefaction of the gas discharged from the top of the refining tower 21 as the heat source of the lithium bromide absorption refrigerator 33, and the crystallizer 31 is used to crystallize and sweat the secondary purification product to obtain electronic grade dimethyl carbonate.

[0031] It should be noted that the dimethyl carbonate purification device of the present invention can be used to purify crude dimethyl carbonate synthesized by oxidative carbonylation of methanol to obtain electronic grade dimethyl carbonate (the electronic grade dimethyl carbonate purity specified in the national standard GB / T 33107-2016 is ≥99.99wt%). The crude dimethyl carbonate includes methanol, dimethyl carbonate (DMC), methyl formate (MF), methylal (ML) and water.

[0032] It is understandable that during the distillation process of the refining tower 21, part of the gaseous components at the top of the tower need to be liquefied and then the reflux rate (refluxed to the refining tower 21) is determined according to the reflux ratio. The liquefaction of the gaseous components will release heat, and the heat will be wasted. Therefore, the present invention utilizes the property of the higher temperature of the gaseous components and uses the thermal energy of the gaseous components as the heat source of the lithium bromide absorption refrigerator 33, thereby also achieving the effect of energy recovery and reuse.

[0033] The extraction device 1 may include a plurality of first reboilers 12 , wherein the first heat medium chamber of at least one of the plurality of first reboilers 12 is connected to the high-temperature waste outlet, and other first reboilers 12 may use other heat mediums, such as steam and the like.

[0034] The extraction tower 11 will mix and heat the extractant and the crude dimethyl carbonate during the extraction and purification process, thereby removing most of the light component impurities. The light component impurities can be considered to be methanol, methyl formate, methylal, etc. The light component impurities are extracted from the top of the extraction tower 11, and the extractant, dimethyl carbonate and the remaining impurities are obtained in the bottom of the extraction tower 11 to form the primary purification product.

[0035] The primary purified product is transported to the refining tower 21 for heating and distillation. After distillation, the top of the refining tower 21 produces a mixture of dimethyl carbonate and light component impurities, and the side line in the middle of the refining tower 21 produces the secondary purified product. The residue in the bottom of the refining tower 21 is high-temperature impurities, which are mainly extractants. In the example of the present invention, the extractant can be dimethyl oxalate (DMO). The refining device 2 also has a second reboiler 22 for heating the material in the refining tower 21.

[0036] The secondary purified product is transported to a crystallizer 31 for crystallization and sweating treatment to obtain electronic grade dimethyl carbonate.

[0037] like Figure 1 As shown, the extraction device 1 also includes an extraction reflux tank 13. The top of the extraction tower 11 has a first vapor outlet and a first reflux inlet. The first vapor outlet is connected to the extraction reflux tank 13, the first reflux inlet is connected to the extraction reflux tank 13, and a first condenser 14 is connected between the first vapor outlet and the extraction reflux tank 13.

[0038] In a specific example, the number of plates of the extraction tower 11 is 40 to 80, the temperature of the bottom of the tower is 110 to 150° C., and the reflux ratio is 1 to 5; the crude dimethyl carbonate enters the extraction tower 11 from the 26th to 53rd plates, and the extractant enters the extraction tower 11 from the 13th to 27th plates. That is, the middle side line of the extraction tower 11 has a crude dimethyl carbonate inlet and an extractant inlet, and the bottom of the extraction tower 11 has a primary purified product outlet.

[0039] Preferably, the number of plates of the extraction tower 11 is 55-65, the bottom temperature is 120-140° C., and the reflux ratio is 1-3; the crude dimethyl carbonate enters the extraction tower 11 from the 37th to 43rd plates, and the extractant enters the extraction tower 11 from the 18th to 22nd plates.

[0040] Specifically, the extraction device 1 further includes an extraction tower preheater 15 connected to the extraction tower 11, wherein the crude dimethyl carbonate is preheated by the extraction tower preheater 15 before entering the extraction tower 11. The extraction tower preheater 15 serves to preheat the crude dimethyl carbonate, and the extraction tower preheater 15 has a preheating chamber for the crude dimethyl carbonate to flow through.

[0041] Furthermore, the extraction tower preheater 15 has a second heat medium chamber for accommodating heat medium, which is used to heat the crude dimethyl carbonate in the extraction tower preheater 15, and the second heat medium chamber is not connected to the preheating chamber.

[0042] Specifically, the second heat medium chamber of the extraction tower preheater 15 is connected to the extraction tower 11, and is used to add the heat medium in the second heat medium chamber into the extraction tower 11. Since the heat medium is the high-temperature impurities remaining in the bottom of the refining tower 21, and the high-temperature impurities are mainly the extractant, the heat medium is added to the extraction tower 11 and reused as the extractant, so as to realize the recycling of the extractant and reduce the cost.

[0043] like Figure 1 As shown, the refining device 2 also includes a refining reflux tank 23, which is connected between the lithium bromide absorption refrigerator 33 and the refining tower 21. The top of the refining tower 21 is provided with a second vapor outlet and a second reflux inlet, the second vapor outlet is connected to the lithium bromide absorption refrigerator 33, and the second reflux inlet is connected to the refining reflux tank 23.

[0044] In a specific example, the number of plates of the refining tower 21 is 20 to 50, the temperature of the bottom of the tower is 150 to 180°C, the reflux ratio is 10 to 30, the primary purification product is fed at the plate number 10 to 25, and the secondary purification product is taken out of the side line at the plate number 6 to 13. That is, the middle side line of the refining tower 21 has a primary purification product inlet and a secondary product outlet, and the secondary product outlet is connected to the crystallizer 31. A secondary purification product storage tank 24 can be connected between the secondary product outlet and the crystallizer 31, and a second condenser 25 is connected between the secondary product outlet and the secondary purification product storage tank 24.

[0045] Preferably, the refining tower 21 has 25 to 40 plates, a bottom temperature of 160 to 170° C., a reflux ratio of 15 to 25, a primary purification product is fed at 13 to 20 plates, and a secondary purification product is taken out from the side line at 7 to 11 plates.

[0046] Among them, the dimethyl carbonate content in the material that can be extracted from the top of the refining tower 21 is ≥99.5wt%, which can be considered as an industrial-grade dimethyl carbonate product, and the dimethyl oxalate content in the high-temperature impurities extracted from the bottom of the tower is ≥99.9wt%, so the high-temperature impurities can be directly used as the extractant in the extraction process of the extraction tower 11.

[0047] Specifically, the crystallizer 31 has a crystallization mother liquor outlet, which is connected to the refining tower 21 to transport the crystallization mother liquor to the refining tower 21. In the crystallization process of the secondary purification product, uncrystallized crystallization mother liquor (the main component of which is dimethyl carbonate, but the purity is not enough) will be produced. In order to avoid waste, the crystallization mother liquor can be transported to the refining tower 21 for distillation. The crystallization mother liquor is high-purity DMC, which is returned to the refining tower 21. It is more advantageous than the crystallization mother liquor directly returning to the extraction tower to mix with low-purity DMC, which is more economical and reduces consumption, and realizes the full coupling of distillation and crystallization.

[0048] Preferably, the crystallization mother liquor outlet is connected to the refining reflux tank 23 , that is, the crystallization mother liquor outlet is connected to the refining tower 21 through the refining reflux tank 23 .

[0049] Among them, after the secondary purification product in the crystallizer 31 is crystallized, sweating treatment can be continued to improve the purity of the crystals to obtain electronic grade dimethyl carbonate crystals. The sweating liquid produced in the sweating process is treated in the same way as the crystallization mother liquor, that is, the sweating liquid can also be transported to the refining tower 21 through the crystallization mother liquor outlet.

[0050] In a specific example, the purification device further includes a finished product tank 4, which is connected to the crystallizer 31 and is used to collect the electronic grade dimethyl carbonate in the crystallizer 31. The electronic grade dimethyl carbonate crystals obtained in the crystallizer 31 are heated and liquefied to obtain electronic grade dimethyl carbonate liquid, which enters the finished product tank 4 through the crystallizer 31.

[0051] like Figure 1 As shown, in the example of the present invention, each component in each device can be connected through a pipeline, and a driving pump 5 can be provided on the pipeline to drive the fluid to flow in the pipeline.

[0052] A specific embodiment of the present invention further provides a dimethyl carbonate purification process. Based on the dimethyl carbonate purification equipment as described above, the dimethyl carbonate purification process comprises the following steps:

[0053] The crude dimethyl carbonate is subjected to extractive distillation by an extraction tower 11 to obtain a primary purified product;

[0054] The primary purified product is refined by a refining tower 21 to obtain a secondary purified product and high-temperature waste respectively;

[0055] The high-temperature waste is transported to the first heat medium chamber of the first reboiler 12 and serves as the heat medium of the first reboiler 12;

[0056] The secondary purified product is crystallized and sweated by a crystallizer 31 to obtain electronic grade dimethyl carbonate;

[0057] In the refining process, the heat energy generated by the liquefaction of the gas discharged from the top of the refining tower is used as the heat source of the lithium bromide absorption refrigerator, and the lithium bromide absorption refrigerator is used to provide a cold source for the precooler.

[0058] Specifically, in the crystallization and sweating treatment, the crystallization temperature is 2 to 4°C, the crystallization time is 2 to 5 hours, the sweating temperature is 4 to 5°C, and the sweating time is 1 to 3 hours.

[0059] The purification equipment and purification process of dimethyl carbonate of the present invention will be described in detail below in conjunction with specific embodiments.

[0060] Example 1

[0061] Build as Figure 1 The purification equipment of dimethyl carbonate is shown.

[0062] The crude dimethyl carbonate synthesized from the oxidative carbonylation of methanol (whose composition is methanol: 16.98wt%, DMC (dimethyl carbonate): 77.19wt%, MF (methyl formate): 2.67wt%, ML (methylal): 2.70wt%, water: 0.45wt%) is preheated to 120°C by an extraction tower preheater and then added to an extraction tower, and the extraction agent DMO is added to the extraction tower, wherein the extraction tower has 60 plates, the crude dimethyl carbonate is fed from the 40th plate with a feed temperature of 120°C, the extraction agent DMO is fed from the 20th plate with a feed temperature of 125°C, the tower top temperature is 65.7°C, the tower bottom temperature is 129.7°C, and the reflux ratio is 1.5.

[0063] The composition of the top distillate of the extraction tower is: methanol: 73.58wt%, DMC: 1.15wt%, MF: 11.60wt%, ML: 11.71wt%, water: 1.97wt%. After extraction, the mixture in the bottom of the extraction tower is the primary purification product, which is composed of extractant DMO: 74.62wt%, DMC: 25.37wt% and a small amount of methanol, water and other components.

[0064] The primary purified product is transferred to a refining tower, wherein the refining tower has 30 plates. The primary purified product is fed from the 15th plate with a feed temperature of 130°C. The secondary purified product is taken out from the 8th plate with a take-off temperature of 93.1°C. The tower top temperature is 92.7°C, the tower bottom temperature is 167.8°C, and the reflux ratio is 20.

[0065] The content of DMC in the secondary purification product is 99.97wt%; the composition of the top distillate of the refining tower is: methanol: 0.14wt%, DMC: 99.86wt%, water: 24ppm, the top distillate of the refining tower can be connected with the extraction tower preheater, that is, the top distillate of the refining tower can be combined with the crude dimethyl carbonate and then enter the extraction tower preheater for preheating before entering the extraction tower; the content of the extractant DMO in the high-temperature impurities in the refining tower kettle is 99.9wt%. The high-temperature impurities are transported to the first heat medium chamber of the first reboiler, the second heat medium chamber of the extraction tower preheater, and the extraction tower in sequence for recycling. During the refining process, the vapor at the top of the refining tower is used as a heat source for a lithium bromide absorption refrigerator.

[0066] The secondary purified product is cooled (precooled to 5.5°C in a precooler) and then transported to a crystallizer, where a program cooling is started, with a cooling rate of 1°C / h, a final crystallization temperature of 2.5°C, and a constant temperature of 2h before discharging the crystallization mother liquor. Subsequently, the program heating is performed to 4°C to start sweating, with a heating rate of 2°C / h, and a constant temperature of 2h before sweating and liquid discharge, wherein the crystallization mother liquor and the sweating liquid are pumped to a refining reflux tank. Then the crystallizer is heated to room temperature, and all dimethyl carbonate crystals melt to obtain electronic grade dimethyl carbonate with a purity of 99.993wt%, which is then transferred to a finished product tank. The cold source of the precooler is mainly provided by a lithium bromide absorption refrigerator, and the industrial waste heat recovery rate released by the liquefaction of the vapor at the top of the refining tower is as high as 0.70.

[0067] The existing electronic-grade dimethyl carbonate separation and purification method, that is, crude dimethyl carbonate is distilled to obtain industrial-grade dimethyl carbonate, and then the electronic-grade dimethyl carbonate product is prepared by melt crystallization. The energy consumption per kg of electronic-grade dimethyl carbonate product is 5231 kJ. The electronic-grade dimethyl carbonate obtained by separation and purification in Example 1 has an energy consumption per unit mass (kg) of product of 4400 kJ, which is a reduction of about 15.89%.

[0068] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0069] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A purification device for dimethyl carbonate, characterized in that, include: An extraction device, comprising an extraction tower and a first reboiler for heating a substance in the extraction tower, wherein the first reboiler has a first heat medium chamber for accommodating a heat medium, and the extraction tower is used to extract and purify a crude dimethyl carbonate product to obtain a primary purified product containing an extractant and dimethyl carbonate; A refining device, comprising a refining tower connected to the extraction tower, the refining tower is used to purify the primary purification product to obtain a secondary purification product, the tower kettle of the refining tower has a high-temperature waste outlet, the high-temperature waste outlet is connected to the first heat medium chamber, and is used to use the high-temperature waste discharged from the tower kettle of the refining tower as a heat medium for heating the first heat medium chamber; The crystallization device comprises a crystallizer connected to the refining tower, a precooler connected between the refining tower and the crystallizer, and a lithium bromide absorption refrigerator for providing a cold source to the precooler, wherein the precooler is used to cool the secondary purification product transported from the refining tower to the crystallizer, the lithium bromide absorption refrigerator is connected to the top of the refining tower so as to use the heat energy generated by the liquefaction of the gas discharged from the top of the refining tower as the heat source of the lithium bromide absorption refrigerator, and the crystallizer is used to crystallize and sweat the secondary purification product to obtain electronic grade dimethyl carbonate.

2. The purification equipment for dimethyl carbonate according to claim 1, characterized in that, The extraction device further comprises an extraction tower preheater connected to the extraction tower, wherein the crude dimethyl carbonate is preheated by the extraction tower preheater before entering the extraction tower.

3. The purification equipment for dimethyl carbonate according to claim 2, characterized in that, The extraction tower preheater has a second heat medium chamber for accommodating heat medium, which is used for heating the crude dimethyl carbonate in the extraction tower preheater.

4. The purification equipment for dimethyl carbonate according to claim 3, characterized in that, The high-temperature waste material includes an extractant, and the second heat medium cavity of the extraction tower preheater is connected to the extraction tower for adding the heat medium in the second heat medium cavity into the extraction tower.

5. The purification equipment for dimethyl carbonate according to claim 1, characterized in that, The extraction device also includes an extraction reflux tank. The top of the extraction tower has a first vapor outlet and a first reflux inlet respectively connected to the extraction reflux tank. A first condenser is connected between the first vapor outlet and the extraction reflux tank.

6. The purification equipment for dimethyl carbonate according to claim 1, characterized in that: The refining device also includes a refining reflux tank connected between the lithium bromide absorption refrigerator and the refining tower. The top of the refining tower has a second vapor outlet and a second reflux inlet. The second vapor outlet is connected to the lithium bromide absorption refrigerator, and the second reflux inlet is connected to the refining reflux tank.

7. The purification equipment for dimethyl carbonate according to claim 1, characterized in that, The crystallizer has a crystallization mother liquor outlet, and the crystallization mother liquor outlet is connected to the refining tower so as to transport the crystallization mother liquor to the refining tower.

8. The purification equipment for dimethyl carbonate according to claim 1, characterized in that, The purification equipment also includes a finished product tank, which is connected to the crystallizer and is used to collect the electronic grade dimethyl carbonate in the crystallizer.

9. A dimethyl carbonate purification process, based on the dimethyl carbonate purification device according to any one of claims 1 to 8, characterized in that: The purification process of dimethyl carbonate comprises the following steps: The crude dimethyl carbonate is subjected to extractive distillation by an extraction tower to obtain a primary purified product; The primary purified product is refined by a refining tower to obtain a secondary purified product and high-temperature waste respectively; The high-temperature waste is transported to the first heat medium chamber of the first reboiler and serves as the heat medium of the first reboiler; The secondary purified product is crystallized and sweated by a crystallizer to obtain electronic grade dimethyl carbonate; In the refining process, the heat energy generated by the liquefaction of the gas discharged from the top of the refining tower is used as the heat source of the lithium bromide absorption refrigerator, and the lithium bromide absorption refrigerator is used to provide a cold source for the precooler.

10. The process for purifying dimethyl carbonate according to claim 9, characterized in that: In the crystallization and sweating treatment, the crystallization temperature is 2-4°C, the crystallization time is 2-5 hours, the sweating temperature is 4-5°C, and the sweating time is 1-3 hours.

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