Apparatus and method for separating dimethyl carbonate and methanol by heat pump pressure swing distillation

Abstract

The present application relates to the technical field of mixture purification, and more particularly to a device and method for separating dimethyl carbonate and methanol by heat pump pressure swing rectification, which comprises a raw material mixer, a first compression heat pump system for extracting dimethyl carbonate and a second compression heat pump system for extracting methanol, the raw material mixer, the first compression heat pump system and the second compression heat pump system are sequentially communicated, and further comprises a first feed heat exchanger, an evaporator, an absorber, a generator and a third condenser, the compression heat pump and the absorption heat pump are combined, the waste heat of the first compression heat pump system and the second compression heat pump system is fully recovered by using the absorption heat pump, the amount of circulating cooling water is reduced, the recovered heat is redistributed to the feed heating, the feed temperature is increased, the energy consumption of the separation process is reduced, the flexible transfer and redistribution of the recovered heat are realized, and the heat recovery and utilization efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mixture purification, and more particularly to a device and method for separating dimethyl carbonate and methanol by heat pump pressure swing rectification. BACKGROUND

[0002] Dimethyl carbonate is a low-toxicity, environmentally friendly, high-performance, and widely used chemical raw material, and has very wide industrial applications. Currently, the main process for industrial production of dimethyl carbonate is ester exchange, such as the ester exchange reaction of carbonic acid ethyl (propyl) ester and methanol (MeOH) in a reaction rectification column to generate dimethyl carbonate and ethylene (propylene) glycol. Because it involves azeotrope separation, ordinary rectification methods cannot achieve effective separation of the system.

[0003] For separating the dimethyl carbonate / methanol system, pressure swing rectification process has the advantages of simple operation, low device investment, and no introduction of a third component, and is widely used in the separation of dimethyl carbonate / methanol azeotrope system. Heat pump technology can convert low-grade heat energy at the top of the column into high-grade heat energy, which can effectively reduce the energy consumption of the pressure swing rectification system and improve the thermodynamic efficiency of the rectification column, achieving good energy-saving effect.

[0004] The prior art discloses a method and device for separating dimethyl carbonate and methanol by heat pump pressure swing rectification. The overhead stream is compressed by a heat pump, which is used as a heat source to heat the kettle liquid. The heated stream is directly used to heat the feed. In this scheme, the overhead waste heat is only used to heat the corresponding kettle material and preheat the corresponding feed. The heat transfer position is limited, and is limited by the temperature difference between the kettle and the overhead and the heat transfer temperature difference. The overhead heat recovery is not sufficient, and the heat recovery and utilization efficiency is low. SUMMARY

[0005] The present application aims to overcome the limitations of heat transfer position and low recovery and utilization efficiency in the prior art, and provides a device and method for separating dimethyl carbonate and methanol by heat pump pressure swing rectification, which increases the amount of waste heat recovered and realizes flexible transfer and redistribution of the recovered heat, thereby improving the heat recovery and utilization efficiency.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is: a device for separating dimethyl carbonate and methanol by heat pump pressure swing rectification is provided, which comprises a raw material mixer, a first compression heat pump system for extracting dimethyl carbonate and a second compression heat pump system for extracting methanol, and the raw material mixer, the first compression heat pump system and the second compression heat pump system are sequentially communicated; characterized in that it further comprises a first feed heat exchanger, an evaporator, an absorber, a generator and a third condenser, the discharge port of the raw material mixer is communicated with the first inlet of the first feed heat exchanger, the first outlet of the first feed heat exchanger is communicated with the first compression heat pump system, the circulating material of the first compression heat pump system enters the generator after heat exchange and then enters the second compression heat pump system, the circulating material of the second compression heat pump system enters the evaporator after heat exchange and then enters the raw material mixer, the concentrated solution outlet of the generator is communicated with the first inlet of the absorber, the dilute solution outlet of the generator is communicated with the first inlet of the third condenser, the first outlet of the third condenser is communicated with the second inlet of the evaporator, the second outlet of the evaporator is communicated with the second inlet of the absorber, the first outlet of the absorber is communicated with the second inlet of the generator, the second outlet of the absorber is communicated with the second inlet of the third condenser, the second outlet of the third condenser is communicated with the second inlet of the first feed heat exchanger, and the second outlet of the first feed heat exchanger is communicated with the third inlet of the absorber.

[0007] The device for separating dimethyl carbonate and methanol by heat pump pressure swing rectification of the present application combines the first compression heat pump system, the second compression heat pump system and the absorption heat pump formed by the absorber, the generator, the third condenser and the evaporator, recovers the waste heat of the first compression heat pump system and the second compression heat pump system by the absorption heat pump, reduces the amount of circulating cooling water, redistributes the heat to the feed heating through the first feed heat exchanger, increases the feed temperature, reduces the energy consumption of the separation process, realizes flexible transfer and redistribution of the recovered heat, and improves the heat recovery and utilization efficiency.

[0008] Further, it further comprises a second centrifugal pump, a first centrifugal pump and a third valve, the first outlet of the absorber is communicated with the second inlet of the generator through the second centrifugal pump, and the first outlet of the third condenser is communicated with the second inlet of the evaporator through the first centrifugal pump and the third valve.

[0009] Further, the first compression heat pump system comprises a high pressure column, a first compressor, a first heat exchanger, a first valve and a first condenser, the first outlet of the first feed heat exchanger is communicated with a first feed port of the high pressure column, a column bottom of the high pressure column is provided with a second discharge port for extracting dimethyl carbonate, a first discharge port at a top of the high pressure column is communicated with an inlet of the first compressor, an outlet of the first compressor is communicated with a first inlet of the first heat exchanger, the second discharge port is communicated with a second inlet of the first heat exchanger, a second outlet of the first heat exchanger is communicated with a second feed port of the column bottom of the high pressure column, the first outlet of the first heat exchanger is communicated with a first inlet of the generator through the first valve, a first outlet of the generator is connected with an inlet of the first condenser, and an outlet of the first condenser is communicated with a third feed port at the top of the high pressure column and the second compression heat pump system respectively.

[0010] Further, the first compression heat pump system comprises a high pressure column, a first compressor, a first heat exchanger, a first valve and a first condenser, the first outlet of the first feed heat exchanger is communicated with a first feed port of the high pressure column, a column bottom of the high pressure column is provided with a second discharge port for extracting dimethyl carbonate, a first discharge port at a top of the high pressure column is communicated with an inlet of the first compressor, an outlet of the first compressor is communicated with a first inlet of the first heat exchanger, the second discharge port is communicated with a second inlet of the first heat exchanger, a second outlet of the first heat exchanger is communicated with a second feed port of the column bottom of the high pressure column, the first outlet of the first heat exchanger is communicated with a first inlet of the generator through the first valve, a first outlet of the generator is connected with an inlet of the first condenser, and an outlet of the first condenser is communicated with a third feed port at the top of the high pressure column and the second compression heat pump system respectively.

[0011] Further, the first compression heat pump system comprises a high pressure column, a first compressor, a first heat exchanger, a first valve and a first condenser, the first outlet of the first feed heat exchanger is communicated with a first feed port of the high pressure column, a column bottom of the high pressure column is provided with a second discharge port for extracting dimethyl carbonate, a first discharge port at a top of the high pressure column is communicated with an inlet of the first compressor, an outlet of the first compressor is communicated with a first inlet of the first heat exchanger, the second discharge port is communicated with a second inlet of the first heat exchanger, a second outlet of the first heat exchanger is communicated with a second feed port of the column bottom of the high pressure column, the first outlet of the first heat exchanger is communicated with a first inlet of the generator through the first valve, a first outlet of the generator is connected with an inlet of the first condenser, and an outlet of the first condenser is communicated with a third feed port at the top of the high pressure column and the second compression heat pump system respectively.

[0012] Further, the first compression heat pump system comprises a high pressure column, a first compressor, a first heat exchanger, a first valve and a first condenser, the first outlet of the first feed heat exchanger is communicated with a first feed port of the high pressure column, a column bottom of the high pressure column is provided with a second discharge port for extracting dimethyl carbonate, a first discharge port at a top of the high pressure column is communicated with an inlet of the first compressor, an outlet of the first compressor is communicated with a first inlet of the first heat exchanger, the second discharge port is communicated with a second inlet of the first heat exchanger, a second outlet of the first heat exchanger is communicated with a second feed port of the column bottom of the high pressure column, the first outlet of the first heat exchanger is communicated with a first inlet of the generator through the first valve, a first outlet of the generator is connected with an inlet of the first condenser, and an outlet of the first condenser is communicated with a third feed port at the top of the high pressure column and the second compression heat pump system respectively.

[0013] Further, the second compression heat pump system comprises a low-pressure column, a second compressor, a second heat exchanger, a second valve and a second condenser, the fifth feed port of the low-pressure column is communicated with the outlet of the first condenser, the column sump of the low-pressure column is provided with a fourth discharge port for extracting methanol, the third discharge port at the top of the low-pressure column is respectively communicated with the inlet of the second compressor and the first outlet of the second heat exchanger, the outlet of the second compressor is communicated with the first inlet of the second heat exchanger, the fourth discharge port of the column sump of the low-pressure column is communicated with the second inlet of the second heat exchanger, the second outlet of the second heat exchanger is communicated with the sixth feed port of the column sump of the low-pressure column, the first outlet of the second heat exchanger is communicated with the first inlet of the evaporator through the second valve, the first outlet of the evaporator is communicated with the inlet of the second condenser, and the outlet of the second condenser is communicated with the seventh feed port of the top of the low-pressure column and communicated with the raw material mixer through a third centrifugal pump.

[0014] The application further provides a method for separating dimethyl carbonate and methanol by heat pump pressure rectification, which is applied to the device for separating dimethyl carbonate and methanol by heat pump pressure rectification, and comprises the following steps: mixing a raw material mixture of dimethyl carbonate and methanol in a raw material mixer, preheating the material through a first feed heat exchanger, and then entering a first compression heat pump system, the first compression heat pump system outputs dimethyl carbonate, and the circulating material in the first compression heat pump system enters a generator to exchange heat and then enters a second compression heat pump system; the second compression heat pump system outputs methanol; and the circulating material in the second compression heat pump system enters an evaporator to exchange heat; the absorbent dilute solution absorbs the heat of the circulating material in the first compression heat pump system in the generator to form hot steam and an absorbent concentrated solution, the hot steam exchanges heat with heat medium water through a third condenser to condense into saturated liquid, and the saturated liquid absorbs the heat of the circulating material in the second compression heat pump system in the evaporator to become cold steam; the absorbent concentrated solution enters an absorber to mix with the cold steam to become dilute and release heat to the heat medium water; the absorbent dilute solution flowing out of the absorber enters the generator to circulate; the heat medium water enters the absorber to absorb heat, then enters the third condenser to absorb the heat of the hot steam, and finally preheats the feed in the first feed heat exchanger and circulates.

[0015] The method for separating dimethyl carbonate and methanol by heat pump pressure rectification of the application combines the first compression heat pump system, the second compression heat pump system and the absorption heat pump formed by the absorber, the generator, the third condenser and the evaporator, recovers the waste heat of the first compression heat pump system and the second compression heat pump system by the absorption heat pump, reduces the amount of circulating cooling water, redistributes the heat to the feed heating through the first feed heat exchanger to increase the temperature of the feed, reduces the energy consumption of the separation process, realizes flexible transfer and redistribution of the recovered heat, and improves the heat recovery and utilization efficiency.

[0016] Preferably, part of the column still distillate from the second outlet of the high-pressure column is returned to the high-pressure column through the second inlet after heat exchange in the first heat exchanger, and the remaining column still distillate is extracted as product dimethyl carbonate; the overhead azeotrope of the high-pressure column enters the first compressor for compression, and after heat exchange with the first heat exchanger, is depressurized through the first valve and enters the generator for heat exchange, is condensed in the first condenser, part of the condensed overhead azeotrope is returned to the high-pressure column through the third inlet, and the remaining condensed overhead azeotrope enters the low-pressure column through the fifth inlet.

[0017] Preferably, the column still distillate of the high-pressure column is divided into three parts, part of the column still distillate is returned to the high-pressure column through the second inlet after heat exchange in the first heat exchanger, part of the column still distillate is returned to the high-pressure column through the fourth inlet after heat exchange in the reboiler, and the remaining column still distillate is extracted as product dimethyl carbonate.

[0018] Preferably, the reboiler exchanges heat with part of the column still distillate of the high-pressure column to generate condensate water, which enters the third feed heat exchanger to heat the feed.

[0019] Preferably, part of the column still distillate from the fourth outlet of the low-pressure column is returned to the low-pressure column through the sixth inlet after heat exchange in the second heat exchanger, and the remaining column still distillate is extracted as product methanol; part of the overhead azeotrope of the low-pressure column enters the second compressor for compression, exchanges heat with the second heat exchanger, the remaining overhead azeotrope is mixed with the stream passing through the second heat exchanger and is depressurized through the second valve to enter the evaporator for heat exchange, and finally the overhead azeotrope is condensed in the second condenser, part of the condensed overhead azeotrope is returned to the low-pressure column through the seventh inlet, and the remaining condensed overhead azeotrope is returned to the raw material mixer as a circulating stream through the third centrifugal pump.

[0020] Preferably, the absorbent is lithium bromide or ammonia water.

[0021] Preferably, the operating pressure of the high-pressure column is 5 bar to 9 bar, and the number of theoretical plates is 20 to 40; the number of theoretical plates of the low-pressure column is 40 to 70.

[0022] Preferably, the overhead temperature of the high-pressure column is , and the column still temperature of the high-pressure column is .

[0023] Preferably, the overhead temperature of the low-pressure column is , and the column still temperature of the low-pressure column is .

[0024] Compared with the prior art, the present application has the beneficial effects that the compression heat pump and the absorption heat pump are combined, the amount of waste heat recovery is increased, the recovered waste heat is redistributed to the feed heating, the feed temperature is increased, the energy consumption of the separation process is reduced, the flexible transfer and redistribution of the recovered heat are realized, and the heat recovery and utilization efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Figure 1 is a structural schematic diagram of a device for separating dimethyl carbonate and methanol by heat pump variable pressure rectification in an embodiment of the present application.

[0026] In the drawings: 1 - raw material mixer; 2 - first feed heat exchanger; 3 - second feed heat exchanger; 4 - third feed heat exchanger; 5 - high-pressure column; 6 - first compressor; 7 - first heat exchanger; 8 - first valve; 9 - first condenser; 10 - low-pressure column; 11 - second compressor; 12 - second heat exchanger; 13 - second valve; 14 - second condenser; 15 - third centrifugal pump; 16 - reboiler; 17 - evaporator; 18 - absorber; 19 - second centrifugal pump; 20 - generator; 21 - third condenser; 22 - first centrifugal pump; 23 - third valve. DETAILED DESCRIPTION

[0027] The present application will be further described below in conjunction with specific embodiments. In the drawings, only exemplary illustrations are shown, and the representations are only schematic diagrams, not physical drawings, and should not be understood as limiting the present patent; in order to better illustrate the embodiments of the present application, some components in the drawings may be omitted, enlarged or reduced, and do not represent the actual product size; for those skilled in the art, it is understandable that some well-known structures in the drawings and their descriptions may be omitted.

[0028] In the drawings of the embodiments of the present application, the same or similar reference numerals correspond to the same or similar components; in the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore the terms describing the positional relationships in the drawings should not be understood as limiting the present patent, and for those skilled in the art, the specific meanings of the above terms can be understood according to the specific circumstances.

[0029] Embodiment one

[0030] This embodiment is the first embodiment of a device for separating dimethyl carbonate and methanol by heat pump variable pressure rectification, as shown in Figure 1As shown, the raw material mixer 1, the first compression heat pump system for extracting dimethyl carbonate and the second compression heat pump system for extracting methanol, the raw material mixer, the first compression heat pump system and the second compression heat pump system are sequentially communicated; further comprising a first feed heat exchanger, an evaporator 17, an absorber 18, a generator 20 and a third condenser 21, the discharge port of the raw material mixer 1 is communicated with the first inlet of the first feed heat exchanger 2, the first outlet of the first feed heat exchanger 2 is communicated with the first compression heat pump system, the circulating material of the first compression heat pump system enters the generator after heat exchange and then enters the second compression heat pump system, the circulating material of the second compression heat pump system enters the evaporator 17 after heat exchange and then enters the raw material mixer 1, the concentrated solution outlet of the generator 20 is communicated with the first inlet of the absorber 18, the dilute solution outlet of the generator 20 is communicated with the first inlet of the third condenser 21, the first outlet of the third condenser 21 is communicated with the second inlet of the evaporator 17, the second outlet of the evaporator 17 is communicated with the second inlet of the absorber 18, the first outlet of the absorber 18 is communicated with the second inlet of the generator 20, the second outlet of the absorber 18 is communicated with the second inlet of the third condenser 21, the second outlet of the third condenser 21 is communicated with the second inlet of the first feed heat exchanger 2, and the second outlet of the first feed heat exchanger 2 is communicated with the third inlet of the absorber 18.

[0031] The above-mentioned device for separating dimethyl carbonate and methanol by heat pump pressure swing rectification combines the first compression heat pump system, the second compression heat pump system and the absorption heat pump formed by the absorber, the generator, the third condenser and the evaporator, recovers the waste heat of the first compression heat pump system and the second compression heat pump system by the absorption heat pump, reduces the amount of circulating cooling water, and through the first feed heat exchanger, redistributes the heat to the feed heating, increases the feed temperature, reduces the energy consumption of the separation process, and at the same time realizes flexible transfer and redistribution of the recovered heat, improves the heat recovery and utilization efficiency.

[0032] Further comprising a second centrifugal pump 19, a first centrifugal pump 22 and a third valve 23, the first outlet of the absorber 18 is communicated with the second inlet of the generator 20 through the second centrifugal pump 19, and the first outlet of the third condenser 21 is communicated with the second inlet of the evaporator 17 through the first centrifugal pump 22 and the third valve 23. The dilute solution of the absorbent absorbs the waste heat of the first compression heat pump system in the generator 20 to form hot steam and concentrated solution of the absorbent, the hot steam is condensed into saturated liquid by heat exchange with the heat medium water in the third condenser 21, and then becomes cold steam by absorbing the waste heat of the second compression heat pump system in the evaporator 17 through the first centrifugal pump 22 and the third valve 23; the concentrated solution of the absorbent enters the absorber 18 to mix with the cold steam to become dilute solution and release heat to the heat medium water; the dilute solution of the absorbent is pressurized by the second centrifugal pump 19 and then enters the generator 20 for circulation.

[0033] The first compression heat pump system includes a high-pressure tower 5, a first compressor 6, a first heat exchanger 7, a first valve 8 and a first condenser 9. The first outlet of the first feed heat exchanger 2 is connected to the first feed port of the high-pressure tower 5. The bottom of the high-pressure tower 5 is provided with a second discharge port for extracting dimethyl carbonate. The first discharge port at the top of the high-pressure tower 5 is connected to the inlet of the first compressor 6. The outlet of the first compressor 6 is connected to the first inlet of the first heat exchanger 7. The second discharge port is connected to the second inlet of the first heat exchanger 7. The second outlet of the first heat exchanger 7 is connected to the second feed port of the bottom of the high-pressure tower 5. The first outlet of the first heat exchanger 7 is connected to the first inlet of the generator 20 through the first valve 8. The first outlet of the generator 20 is connected to the inlet of the first condenser 9. The outlet of the first condenser 9 is respectively connected to the third feed port at the top of the high-pressure tower 5 and the second compression heat pump system. During implementation, part of the bottom distillate flowing out from the second discharge port of the high-pressure tower 5 is returned to the high-pressure tower 5 through the second feed port after heat exchange in the first heat exchanger 7, and the remaining bottom distillate is extracted as the product dimethyl carbonate; the top azeotrope of the high-pressure tower 5 enters the first compressor 6 for compression through the first discharge port, exchanges heat with the first heat exchanger 7, is reduced in pressure through the first valve 8, enters the generator 20 for heat exchange, enters the first condenser 9 for condensation, and part of the condensed top azeotrope is refluxed to the high-pressure tower 5 through the third feed port, and the remaining condensed top azeotrope enters the second compression heat pump system.

[0034] It also includes a second feed heat exchanger 3, the first outlet of the first feed heat exchanger 2 is connected to the first inlet of the second feed heat exchanger 3, the first outlet of the second feed heat exchanger 3 is connected to the first feed port of the high-pressure tower 5, the first outlet of the first heat exchanger 7 is also connected to the second inlet of the second feed heat exchanger 3, and the second outlet of the second feed heat exchanger 3 is connected to the inlet of the first condenser 9. During implementation, the raw material mixture of dimethyl carbonate and methanol is mixed in the raw material mixer 1 and then preheated through the first feed heat exchanger 2 and the second feed heat exchanger 3, and then enters the high-pressure tower 5. The top azeotrope of the high-pressure tower 5 enters the first compressor 6 for compression through the first discharge port, exchanges heat with the first heat exchanger 7 and then is split. Part of the top azeotrope exchanges heat with the second feed heat exchanger 3, and the remaining top azeotrope is reduced in pressure through the first valve 8 and enters the generator 20 for heat exchange. Finally, the top azeotrope is mixed and enters the first condenser 9 for condensation. Part of the condensed top azeotrope is refluxed to the high-pressure tower 5 through the third feed port, and the remaining condensed top azeotrope enters the second compression heat pump system.

[0035] like Figure 1 As shown, a reboiler 16 is further included, and the second discharge port of the tower kettle of the high-pressure tower 5 is also connected to the fourth feed port of the tower kettle of the high-pressure tower 5 through the reboiler 16. The reboiler 16 can be used for heating.

[0036] like Figure 1As shown, the third feed heat exchanger 4 is further included, the first outlet of the second feed heat exchanger 3 is communicated with the first inlet of the third feed heat exchanger 4, the first outlet of the third feed heat exchanger 4 is communicated with the first feed port of the high-pressure column 5, and the discharge port of the reboiler 16 is communicated with the second inlet of the third feed heat exchanger 4. The heat of the condensed water after reboiling of the reboiler 16 is fully recovered to preheat the feed, so that the temperature of the feed is increased, and the steam consumption of the pressure swing distillation is reduced.

[0037] The second compression heat pump system includes a low-pressure column 10, a second compressor 11, a second heat exchanger 12, a second valve 13 and a second condenser 14. The fifth feed port of the low-pressure column 10 is communicated with the outlet of the first condenser 9, the column still of the low-pressure column 10 is provided with a fourth discharge port for extracting methanol, the third discharge port at the top of the low-pressure column 10 is respectively communicated with the inlet of the second compressor 11 and the first outlet of the second heat exchanger 12, the outlet of the second compressor 11 is communicated with the first inlet of the second heat exchanger 12, the fourth discharge port of the column still of the low-pressure column 10 is communicated with the second inlet of the second heat exchanger 12, the second outlet of the second heat exchanger 12 is communicated with the sixth feed port of the column still of the low-pressure column 10, the first outlet of the second heat exchanger 12 is communicated with the first inlet of the evaporator 17 through the second valve 13, the first outlet of the evaporator 17 is communicated with the inlet of the second condenser 14, and the outlet of the second condenser 14 is communicated with the seventh feed port at the top of the low-pressure column 10 and communicated with the raw material mixer 1 through the third centrifugal pump 15. In implementation, part of the column still distillate flowing out of the fourth discharge port of the low-pressure column 10 is heated by the second heat exchanger 12 and then returned to the low-pressure column 10 through the sixth feed port, and the remaining column still distillate is extracted as product methanol; part of the azeotrope at the top of the low-pressure column 10 enters the second compressor 11 through the third discharge port, is compressed, is heated by the second heat exchanger 12, the remaining azeotrope at the top is mixed with the stream passing through the second heat exchanger 12, is depressurized by the second valve 13, enters the evaporator 17 to be heated, and finally the azeotrope at the top enters the second condenser 14 to be condensed, part of the condensed azeotrope at the top returns to the low-pressure column 10 through the seventh feed port, and the remaining condensed azeotrope at the top returns to the raw material mixer 1 as a circulating stream through the third centrifugal pump 15.

[0038] Example Two

[0039] The first embodiment of the method for separating dimethyl carbonate and methanol by heat pump pressure swing rectification is applied to the device for separating dimethyl carbonate and methanol by heat pump pressure swing rectification in the first embodiment, which comprises the following steps: mixing the raw material mixture of dimethyl carbonate and methanol with the circulating material in the raw material mixer 1, preheating the material through the first feed heat exchanger 2, the second feed heat exchanger 3 and the third feed heat exchanger 4, and then entering the high-pressure column 5 through the first feed port; part of the column stillage of the high-pressure column 5 is returned to the high-pressure column 5 through the second feed port after heat exchange through the first heat exchanger 7; part of the column stillage is returned to the high-pressure column 5 through the fourth feed port after heat exchange through the reboiler 16; the remaining column stillage is taken out as the product dimethyl carbonate; the condensed water generated by the reboiler enters the third feed heat exchanger to heat the feed; the azeotrope at the top of the high-pressure column 5 enters the first compressor 6 through the first discharge port, is branched after heat exchange with the first heat exchanger 7, part of the azeotrope at the top is heat exchanged with the second feed heat exchanger 3, the remaining azeotrope at the top is depressurized through the first valve 8 and enters the generator 20 for heat exchange, and finally the azeotrope at the top is mixed and enters the first condenser 9 for condensation, part of the condensed azeotrope at the top is returned to the high-pressure column 5 through the third feed port, and the remaining condensed azeotrope at the top enters the low-pressure column 10 through the fifth feed port; part of the column stillage of the low-pressure column 10 is returned to the low-pressure column 10 through the sixth feed port after heat exchange through the second heat exchanger 12, and the remaining column stillage is taken out as the product methanol; part of the azeotrope at the top of the low-pressure column 10 enters the second compressor 11 through the third discharge port, is heat exchanged with the second heat exchanger 12, the remaining azeotrope at the top is mixed with the stream passing through the second heat exchanger 12 and is depressurized through the second valve 13 to enter the evaporator 17 for heat exchange, and finally the azeotrope at the top enters the second condenser 14 for condensation, part of the condensed azeotrope at the top is returned to the low-pressure column 10 through the seventh feed port, and the remaining condensed azeotrope at the top is returned to the raw material mixer 1 as the circulating material through the third centrifugal pump 15; the heat absorbed by the absorbent dilute solution in the generator 20 after heat exchange with the azeotrope at the top of the high-pressure column 5 forms hot steam and an absorbent concentrated solution, the hot steam is condensed into saturated liquid by heat exchange with the heat medium water through the third condenser 21, and is changed into cold steam by absorbing the heat after heat exchange with the azeotrope at the top of the low-pressure column 10 in the evaporator 17 through the first centrifugal pump 22 and the third valve 23; the absorbent concentrated solution is mixed with the cold steam in the absorber 18 to become dilute and release heat to the heat medium water; the absorbent dilute solution is pressurized by the second centrifugal pump 19 and enters the generator 20 for circulation; the heat medium water absorbs heat in the absorber 18, absorbs the heat of the hot steam in the third condenser 21, and finally preheats the feed in the first feed heat exchanger 2 and circulates.

[0040] The absorbent is lithium bromide or ammonia water.

[0041] The operating pressure of the high-pressure column 5 is 5 bar to 9 bar, and the theoretical plate number is 20 to 40; the theoretical plate number of the low-pressure column 10 is 40 to 70.

[0042] The overhead temperature of the high pressure column 5 is The bottom temperature of the high pressure column 5 is .

[0043] The overhead temperature of the low pressure column 10 is The bottom temperature of the low pressure column 10 is .

[0044] Example Three

[0045] The second embodiment of the method for separating dimethyl carbonate and methanol by heat pump pressure swing rectification, which is similar to the second embodiment, includes: the feed flow rate of the raw material mixer 1 is 20000 kg / h, the feed contains 27% dimethyl carbonate and 73% methanol by mass fraction, the number of theoretical plates of the high-pressure column 5 is 30, the number of theoretical plates of the low-pressure column 10 is 50, the mixture of dimethyl carbonate and methanol is mixed with the circulating material, and then preheated by the first feed heat exchanger 2, the second feed heat exchanger 3 and the third feed heat exchanger 4, and then enters the 15th plate of the high-pressure column 5, 98% of the high-pressure column 5 column stills out of the total mass flow rate returns to the high-pressure column 5 after heat exchange by the first heat exchanger 7 and the reboiler 16, the condensed water in the reboiler 16 enters the third feed heat exchanger 4 to heat the feed, and the remaining stills are collected as product dimethyl carbonate, and 5400 kg / h of 99.5% dimethyl carbonate is obtained at the bottom of the high-pressure column 5. The azeotrope at the top of the high-pressure column 5 is compressed by the first compressor 6, the compression ratio of the first compressor 6 is 2.76, the gaseous phase stream after pressure increase is heated by the first heat exchanger 7, then is branched, 35% of the azeotrope at the top of the column by the total mass flow rate is sent to the second feed heat exchanger 3 to heat the feed, the remaining azeotrope provides heat for the generator 20, and finally the mixture is condensed in the first condenser 9; after condensation, 64% of the azeotrope by the total mass flow rate returns to the top of the high-pressure column 5, and the remaining azeotrope enters the low-pressure column 10 at the 25th plate of the low-pressure column 10, and the flow rate is 32600 kg / h. 87% of the azeotrope at the top of the low-pressure column 10 by the total mass flow rate is compressed by the second compressor 11, the compression ratio of the second compressor 11 is 1.25, and then provides heat for the second heat exchanger 12, the remaining azeotrope is mixed with the stream after heat exchange by the second heat exchanger 12, then is heat exchanged by the evaporator 17, and finally is condensed by the second condenser 14; after condensation, 73% of the azeotrope by the total mass flow rate returns to the top of the low-pressure column 10, and the remaining azeotrope returns to the raw material mixer 1 as a circulating stream by the third centrifugal pump 15, 23% of the low-pressure column 10 column stills by the total mass flow rate returns to the low-pressure column 10 after heat exchange by the second heat exchanger 12, and the remaining column still is collected as product methanol, and 14600 kg / h of 99.8% methanol is obtained at the bottom of the low-pressure column 10; the dilute solution of the absorbent absorbs the heat after heat exchange of the azeotrope at the top of the high-pressure column 5 by the generator 20, the absorbent is lithium bromide solution, forms hot steam and concentrated solution of the absorbent, the concentrated solution of the absorbent enters the absorber 18 to mix with cold steam to become thin and release heat to the heat medium water; the hot steam is condensed into saturated liquid by the third condenser 21, is evaporated into cold steam by the first centrifugal pump 22 in the evaporator 17, is mixed with the concentrated solution of the low-pressure absorbent in the absorber 18 to become dilute solution of the absorbent, and the dilute solution of the absorbent is pressurized by the second centrifugal pump 19 to enter the generator 20 to circulate; the heat medium water first absorbs heat in the absorber 18, then absorbs heat in the third condenser 21, and finally heats the feed in the first feed heat exchanger 2 and circulates.

[0046] In this embodiment, the operating pressure of the high-pressure column 5 is 7 bar, the overhead temperature of the high-pressure column 5 is 123 , the bottom temperature is 163 ; the operating pressure of the low-pressure column 10 is 1 bar, the overhead temperature of the low-pressure column 10 is 63 , the bottom temperature is 64 ; the purity of the separated dimethyl carbonate is 99.5%, and the purity of the methanol is 99.8%. Compared with the existing heat pump assisted pressure swing distillation process, the energy consumption is reduced by about 18% under the condition of achieving the same separation requirement and product purity.

[0047] Example Four

[0048] This embodiment is a third embodiment of the method for separating dimethyl carbonate and methanol by heat pump pressure swing distillation. This embodiment is similar to Example Three, except that the feed flow rate of the raw material mixer 1 is 100000 kg / h, the feed contains 30% by mass of dimethyl carbonate and 70% by mass of methanol, the compression ratio of the first compressor 6 is 2.9, 30000 kg / h of 99.5% dimethyl carbonate is obtained at the bottom of the high-pressure column 5; after heat exchange of the high-pressure column 5, the gas phase stream enters from the 25th tray of the low-pressure column 10 at a flow rate of 126000 kg / h, the compression ratio of the second compressor 11 is 1.3, 70000 kg / h of 99.8% methanol is obtained at the bottom of the low-pressure column 10. Compared with the existing heat pump assisted pressure swing distillation process, the energy consumption is reduced by about 15% under the condition of achieving the same separation requirement and product purity.

[0049] Example Five

[0050] This embodiment is a fourth embodiment of the method for separating dimethyl carbonate and methanol by heat pump pressure swing distillation. This embodiment is similar to Example Three, except that the feed flow rate of the raw material mixer 1 is 80000 kg / h, the feed contains 28% by mass of dimethyl carbonate and 72% by mass of methanol, the compression ratio of the first compressor 6 is 2.84, 22335 kg / h of 99.5% dimethyl carbonate is obtained at the bottom of the high-pressure column 5; after heat exchange of the high-pressure column 5, the gas phase stream enters from the 25th tray of the low-pressure column 10 at a flow rate of 103792 kg / h, the compression ratio of the second compressor 11 is 1.28, 57662 kg / h of 99.8% methanol is obtained at the bottom of the low-pressure column 10. Compared with the existing heat pump assisted pressure swing distillation process, the energy consumption is reduced by about 16% under the condition of achieving the same separation requirement and product purity.

[0051] In the specific contents of the foregoing specific embodiments, each technical feature can be combined arbitrarily without contradiction. In order to make the description simple, all possible combinations of the foregoing technical features are not described, but as long as the combinations of the technical features do not contradict, they should be considered as the scope of the present disclosure.

[0052] Obviously, the above embodiments of the present application are merely exemplary and are not intended to limit the implementation of the present application. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. Here, it is not necessary and impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A device for separating dimethyl carbonate and methanol by heat pump pressure swing distillation, comprising a raw material mixer (1), a first compression heat pump system for extracting dimethyl carbonate, and a second compression heat pump system for extracting methanol, wherein the raw material mixer, the first compression heat pump system, and the second compression heat pump system are connected in sequence; characterized in that: The invention also includes a first feed heat exchanger, an evaporator (17), an absorber (18), a generator (20) and a third condenser (21). The discharge port of the raw material mixer (1) is communicated with the first inlet of the first feed heat exchanger (2), the first outlet of the first feed heat exchanger (2) is communicated with the first compression heat pump system, the circulating material of the first compression heat pump system enters the generator for heat exchange and then enters the second compression heat pump system, the circulating material of the second compression heat pump system enters the evaporator (17) for heat exchange and then enters the raw material mixer (1), the concentrated solution outlet of the generator (20) is communicated with the first inlet of the absorber (18), the generator The dilute solution outlet of (20) is communicated with the first inlet of the third condenser (21), the first outlet of the third condenser (21) is communicated with the second inlet of the evaporator (17), the second outlet of the evaporator (17) is communicated with the second inlet of the absorber (18), the first outlet of the absorber (18) is communicated with the second inlet of the generator (20), the second outlet of the absorber (18) is communicated with the second inlet of the third condenser (21), the second outlet of the third condenser (21) is communicated with the second inlet of the first feed heat exchanger (2), and the second outlet of the first feed heat exchanger (2) is communicated with the third inlet of the absorber (18); It also includes a second centrifugal pump (19), a first centrifugal pump (22) and a third valve (23), wherein the first outlet of the absorber (18) is connected to the second inlet of the generator (20) through the second centrifugal pump (19), and the first outlet of the third condenser (21) is connected to the second inlet of the evaporator (17) through the first centrifugal pump (22) and the third valve (23).

2. The device for separating dimethyl carbonate and methanol by heat pump pressure swing distillation according to claim 1, characterized in that: The first compression heat pump system comprises a high-pressure tower (5), a first compressor (6), a first heat exchanger (7), a first valve (8) and a first condenser (9); the first outlet of the first feed heat exchanger (2) is communicated with the first feed port of the high-pressure tower (5); the bottom of the high-pressure tower (5) is provided with a second discharge port for extracting dimethyl carbonate; the first discharge port at the top of the high-pressure tower (5) is communicated with the inlet of the first compressor (6); the outlet of the first compressor (6) is communicated with the first inlet of the first heat exchanger (7); the second discharge port is communicated with the second inlet of the first heat exchanger (7); the second outlet of the first heat exchanger (7) is communicated with the second feed port of the bottom of the high-pressure tower (5); the first outlet of the first heat exchanger (7) is communicated with the first inlet of the generator (20) through the first valve (8); the first outlet of the generator (20) is connected to the inlet of the first condenser (9); the outlet of the first condenser (9) is communicated with the third feed port at the top of the high-pressure tower (5) and the second compression heat pump system respectively.

3. The device for separating dimethyl carbonate and methanol by heat pump pressure swing distillation according to claim 2, characterized in that: The first outlet of the first feed heat exchanger (2) is connected to the first inlet of the second feed heat exchanger (3), the first outlet of the second feed heat exchanger (3) is connected to the first feed port of the high-pressure column (5), the first outlet of the first heat exchanger (7) is also connected to the second inlet of the second feed heat exchanger (3), and the second outlet of the second feed heat exchanger (3) is connected to the inlet of the first condenser (9).

4. The device for separating dimethyl carbonate and methanol by heat pump pressure swing distillation according to claim 3, characterized in that: It also includes a reboiler (16), and the second discharge port of the tower kettle of the high-pressure tower (5) is also connected to the fourth feed port of the tower kettle of the high-pressure tower (5) through the reboiler (16).

5. The device for separating dimethyl carbonate and methanol by heat pump pressure swing distillation according to claim 4, characterized in that: The invention also includes a third feed heat exchanger (4), a first outlet of the second feed heat exchanger (3) is connected to a first inlet of the third feed heat exchanger (4), the first outlet of the third feed heat exchanger (4) is connected to a first feed port of the high-pressure column (5), and the discharge port of the reboiler (16) is connected to a second inlet of the third feed heat exchanger (4).

6. The device for separating dimethyl carbonate and methanol by heat pump pressure swing distillation according to any one of claims 2 to 5, characterized in that: The second compression heat pump system comprises a low-pressure tower (10), a second compressor (11), a second heat exchanger (12), a second valve (13) and a second condenser (14); the fifth feed port of the low-pressure tower (10) is connected to the outlet of the first condenser (9); the bottom of the low-pressure tower (10) is provided with a fourth discharge port for extracting methanol; the third discharge port at the top of the low-pressure tower (10) is respectively connected to the inlet of the second compressor (11) and the first outlet of the second heat exchanger (12); the outlet of the second compressor (11) is connected to the first inlet of the second heat exchanger (12); The fourth discharge port of the bottom of the high-pressure tower (10) is communicated with the second inlet of the second heat exchanger (12), the second outlet of the second heat exchanger (12) is communicated with the sixth feed port of the bottom of the low-pressure tower (10), the first outlet of the second heat exchanger (12) is communicated with the first inlet of the evaporator (17) through the second valve (13), the first outlet of the evaporator (17) is communicated with the inlet of the second condenser (14), the outlet of the second condenser (14) is communicated with the seventh feed port at the top of the low-pressure tower (10) and is communicated with the raw material mixer (1) through the third centrifugal pump (15).

7. A method for separating dimethyl carbonate and methanol by heat pump pressure swing distillation, applied to the device for separating dimethyl carbonate and methanol by heat pump pressure swing distillation according to claim 6, characterized in that: include: The raw material mixture of dimethyl carbonate and methanol is mixed in the raw material mixer (1), and then preheated by the first feed heat exchanger (2). The mixture then enters the first compression heat pump system. The first compression heat pump system produces dimethyl carbonate, and the circulating material in the first compression heat pump system enters the generator (20) for heat exchange and then enters the second compression heat pump system. The second compression heat pump system produces methanol. The circulating material in the second compression heat pump system enters the evaporator (17) for heat exchange. The absorbent dilute solution absorbs the circulating material in the first compression heat pump system in the generator (20). Heat is absorbed to form hot steam and concentrated absorbent solution. The hot steam is condensed into saturated liquid through heat exchange with the heat medium water in the third condenser (21). The hot steam absorbs the heat of the circulating material in the second compression heat pump system in the evaporator (17) and turns into cold steam. The concentrated absorbent solution enters the absorber (18) and mixes with the cold steam to become thinner and release heat to the heat medium water. The dilute absorbent solution flowing out of the absorber (18) enters the generator (20) for circulation. The heat medium water enters the absorber (18) to absorb heat, then enters the third condenser (21) to absorb heat from the hot steam, and finally preheats the feed in the first feed heat exchanger (2) and circulates.

8. The method for separating dimethyl carbonate and methanol by heat pump pressure swing distillation according to claim 7, characterized in that: Part of the bottom distillate flowing out of the second discharge port of the high-pressure tower (5) is returned to the high-pressure tower (5) through the second feed port after heat exchange in the first heat exchanger (7), and the remaining bottom distillate is extracted as the product dimethyl carbonate; the top azeotrope of the high-pressure tower (5) enters the first compressor (6) through the first discharge port for compression, exchanges heat with the first heat exchanger (7), is decompressed through the first valve (8), enters the generator (20) for heat exchange, enters the first condenser (9) for condensation, and part of the condensed top azeotrope is refluxed to the high-pressure tower (5) through the third feed port, and the remaining condensed top azeotrope enters the low-pressure tower (10) through the fifth feed port.

9. The method for separating dimethyl carbonate and methanol by heat pump pressure swing distillation according to claim 7, characterized in that: Part of the bottom distillate flowing out of the fourth outlet of the low-pressure tower (10) is returned to the low-pressure tower (10) through the sixth feed port after heat exchange in the second heat exchanger (12), and the remaining bottom distillate is extracted as product methanol; part of the top azeotrope of the low-pressure tower (10) enters the second compressor (11) through the third outlet for compression and heat exchange with the second heat exchanger (12), and the remaining top azeotrope is mixed with the stream passing through the second heat exchanger (12) and decompressed through the second valve (13) and enters the evaporator (17) for heat exchange, and finally the top azeotrope enters the second condenser (14) for condensation, and part of the condensed top azeotrope is refluxed to the low-pressure tower (10) through the seventh feed port, and the remaining condensed top azeotrope is returned to the raw material mixer (1) as a circulating stream through the third centrifugal pump (15).

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