Energy-saving device for producing dimethyl carbonate

Abstract

The utility model provides an energy-saving device for producing dimethyl carbonate, which comprises a catalytic rectifying tower, a pressurizing tower, an atmospheric tower and a preheater for heating the pressurizing tower, and the catalytic rectifying tower, the pressurizing tower and the atmospheric tower are connected through a heat coupling system. The heat coupling system comprises a second condensation reboiler used for heating the catalytic rectifying tower and a first condensation reboiler used for heating the atmospheric tower, and in the heat coupling system, rising material steam of the pressurizing tower serves as a heat source of the catalytic rectifying tower; and rising material steam of the catalytic rectifying tower is reused as a heat source of the atmospheric tower, so that the effects of saving energy and reducing consumption are achieved, and the economic benefit is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of rectification energy saving, in particular to an energy-saving device for producing dimethyl carbonate. Background Art

[0002] The transesterification process for producing dimethyl carbonate involves the transesterification of ethylene carbonate or propylene carbonate with methanol to produce dimethyl carbonate and ethylene glycol or propylene glycol. This reaction is carried out in a catalytic distillation column using either a homogeneous or heterogeneous catalyst. Due to the presence of excess methanol, methanol and the dimethyl carbonate product form an azeotrope, making separation of this azeotrope a crucial issue in the dimethyl carbonate production process.

[0003] In industrial plants, pressure swing distillation is often used to separate azeotropes. Dimethyl carbonate is obtained in the pressure column kettle, and methanol is obtained in the atmospheric pressure column kettle and recycled back to the catalytic distillation column. In order to save energy, industrial plants often use thermal coupling between the pressure column and the atmospheric pressure column, using the rising steam from the pressure column as the heating medium for the atmospheric pressure column, thereby saving steam energy consumption in the atmospheric pressure column. Figure 1 The pressure tower and the atmospheric tower are coupled to produce dimethyl carbonate. There is also a device that combines the atmospheric tower and the reaction tower, as shown in the attached figure. Figure 2 The illustrated apparatus for producing dimethyl carbonate by coupling a pressurizing tower and a distillation tower is described in patent CN201310692281.7A. The methanol at the top of the pressurizing tower, which contains a relatively low amount of dimethyl carbonate (approximately 5-10%), is directly returned to the reaction tower. The rising steam from the pressurizing tower is then used to heat the reaction tower, achieving thermal coupling between the pressurizing and reaction towers. This can reduce energy consumption and equipment costs by more than 50%. However, since the methanol recycle stream contains 5-10% dimethyl carbonate, the recirculation of the dimethyl carbonate product inhibits the reaction, resulting in a decrease in the conversion rate of ethylene carbonate or propylene carbonate, thereby increasing material consumption. Furthermore, since the catalytic distillation tower incorporates the function of atmospheric pressure, its reflux rate increases, which to a certain extent increases energy consumption. Utility Model Content

[0004] In response to the shortcomings of the prior art, the present invention discloses an energy-saving device for producing dimethyl carbonate, which addresses the high energy consumption during azeotrope separation in the prior art dimethyl carbonate production process. The present invention provides an energy-saving device for producing dimethyl carbonate, which connects a catalytic distillation tower, a pressurized tower, and an atmospheric pressure tower via thermal coupling. The rising vapor from the pressurized tower serves as the heat source for the catalytic distillation tower, and the rising vapor from the catalytic distillation tower is reused as the heat source for the atmospheric pressure tower.

[0005] In order to achieve the above technical objectives, the utility model provides an energy-saving device for producing dimethyl carbonate, comprising a catalytic distillation tower, a pressure tower, an atmospheric pressure tower and a preheater for heating the pressure tower, wherein the catalytic distillation tower, the pressure tower and the atmospheric pressure tower are connected by a heat coupling system, and the heat coupling system comprises a second condenser-reboiler for heating the catalytic distillation tower and a first condenser-reboiler for heating the atmospheric pressure tower.

[0006] The rising material vapor of the pressure tower is connected to the heat source inlet of the second condenser reboiler through the material outlet at the top of the pressure tower, and the heat source is provided to the catalytic distillation tower after being heated in the second condenser reboiler; the rising material vapor of the catalytic distillation tower is connected to the heat source inlet of the first condenser reboiler through the material outlet at the top of the catalytic distillation tower, and the heat source is provided to the atmospheric pressure tower after being heated in the first condenser reboiler, so as to realize thermal coupling of the three towers of the catalytic distillation tower, the pressure tower and the atmospheric pressure tower.

[0007] Furthermore, the tower body of the catalytic distillation tower is provided with a catalytic distillation tower feed pipe and a catalytic distillation tower liquid inlet pipe; the top material outlet of the catalytic distillation tower is connected to the pressure tower through a first condenser-reboiler; the top material outlet of the pressure tower is connected to the atmospheric pressure tower through a second condenser-reboiler; the top material outlet of the atmospheric pressure tower is connected to the pressure tower through a condenser; and the bottom material outlet of the atmospheric pressure tower is connected to the catalytic distillation tower.

[0008] The feed pipe of the catalytic distillation tower is raw material ethylene carbonate or propylene carbonate, the liquid inlet pipe of the catalytic distillation tower is raw material methanol, methanol and dimethyl carbonate azeotrope are separated at the top of the catalytic distillation tower, and the methanol and dimethyl carbonate azeotrope are sent to the pressure tower through a first condenser reboiler, separated by the pressure tower, most of the methanol and a small amount of dimethyl carbonate azeotrope are separated at the top of the pressure tower, and most of the methanol and a small amount of dimethyl carbonate azeotrope are sent to the atmospheric pressure tower through a second condenser reboiler, separated by the atmospheric pressure tower, most of the dimethyl carbonate and a small amount of methanol azeotrope are separated at the top of the atmospheric pressure tower, and sent to the pressure tower through a condenser, and methanol is extracted from the atmospheric pressure tower kettle and refluxed to the catalytic distillation tower for reuse.

[0009] Specifically, the top material outlet of the catalytic distillation tower is connected to the first condenser-reboiler through a catalytic distillation tower discharge pipe, and the first branch of the first condenser-reboiler is connected to the first feed port of the pressurizing tower.

[0010] Specifically, the top material outlet of the pressure tower is connected to the second condenser-reboiler through a pressure tower discharge pipe, and the first branch of the second condenser-reboiler is connected to the atmospheric tower feed port of the atmospheric tower.

[0011] Specifically, the material outlet discharge pipe at the top of the atmospheric tower is connected to the second feed inlet of the pressure tower through a condenser.

[0012] Furthermore, the catalytic distillation tower kettle is provided with a discharge pipe for a mixture of methanol, ethylene glycol or propylene glycol. After being distilled in the catalytic distillation tower, the mixture of methanol, ethylene glycol or propylene glycol is extracted from the kettle of the catalytic distillation tower.

[0013] Furthermore, the pressurized tower kettle is connected to a dimethyl carbonate discharge pipe, and the dimethyl carbonate separated by the pressurized tower is taken out from the pressurized tower kettle.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides an energy-saving device for producing dimethyl carbonate, which connects a catalytic distillation tower, a pressure tower and an atmospheric pressure tower through thermal coupling. The rising material steam of the pressure tower is used as the heat source of the catalytic distillation tower, and the rising material steam of the catalytic distillation tower is reused as the heat source of the atmospheric pressure tower. The heating steam required for conventional reaction pressure swing distillation is 16404.84 kW. Through thermal coupling, 8295.08 kW of steam is saved, and 50.56% of the steam consumption is saved, achieving the effect of energy saving and consumption reduction, thereby improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings constituting the specification of this application are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0016] Figure 1 It shows a device for producing dimethyl carbonate by coupling a pressure tower and an atmospheric pressure tower;

[0017] Figure 2 It shows a device for producing dimethyl carbonate by coupling a pressure tower and a distillation tower;

[0018] Figure 3 An energy-saving device for producing dimethyl carbonate according to an embodiment of the present utility model is shown.

[0019] Among them, the above-mentioned drawings include the following figure marks: 1. catalytic distillation tower; 2. pressure tower; 3. atmospheric tower; 4. first condenser-reboiler; 5. second condenser-reboiler; 6. catalytic distillation tower feed pipe; 7. catalytic distillation tower liquid inlet pipe; 8. catalytic distillation tower discharge pipe; 9. methanol, ethylene glycol or propylene glycol mixture discharge pipe; 10. first feed port of pressure tower; 11. first branch of first condenser-reboiler; 12. pressure tower discharge pipe; 13. preheater; 14. dimethyl carbonate product discharge pipe; 15. atmospheric tower feed port; 16. first branch of second condenser-reboiler; 17. atmospheric tower discharge pipe; 18. condenser; 19. atmospheric tower kettle discharge pipe; 20. second feed port of pressure tower. DETAILED DESCRIPTION

[0020] To facilitate understanding of the present invention, the present invention will be described in more detail below, with preferred embodiments thereof given. However, it should be understood that these embodiments are merely for the purpose of further explanation and should not be construed as limiting the present invention in any form, i.e., they are not intended to limit the scope of protection of the present invention.

[0021] The present invention will be further described below in conjunction with the accompanying drawings.

[0022] Example 1

[0023] An energy-saving device for producing dimethyl carbonate, as shown in the following Figure 3 As shown: it includes a catalytic distillation tower 1, a pressure tower 2, an atmospheric tower 3 and a preheater 13 for heating the pressure tower 2. The catalytic distillation tower 1, the pressure tower 2 and the atmospheric tower 3 are connected by a heat coupling system. The heat coupling system includes a second condenser-reboiler 5 for heating the catalytic distillation tower 1 and a first condenser-reboiler 4 for heating the atmospheric tower 3. The rising material steam of the pressure tower 2 is connected to the heat source inlet of the second condenser-reboiler 5 through the material outlet of the pressure tower top, and the heat source is provided to the catalytic distillation tower 1 after being heated by the second condenser-reboiler 5; the rising material steam of the catalytic distillation tower 1 is connected to the heat source inlet of the first condenser-reboiler 4 through the material outlet of the catalytic distillation tower 1 top, and the heat source is provided to the atmospheric tower 3 after being heated by the first condenser-reboiler 4, so as to realize the heat coupling of the three towers of the catalytic distillation tower 1, the pressure tower 2 and the atmospheric tower 3; the raw material ethylene carbonate or carbon Propylene glycol ester enters the catalytic distillation tower 1 through the catalytic distillation tower feed pipe 6, and the raw material methanol enters the catalytic distillation tower through the catalytic distillation tower liquid inlet pipe 7. After the above raw materials are catalytically distilled, the methanol and dimethyl carbonate azeotrope are separated at the top of the catalytic distillation tower, and the methanol and dimethyl carbonate azeotrope are sent to the pressure tower 2 through the catalytic distillation tower discharge pipe 8 via the first condenser reboiler 4. After separation in the pressure tower, most of the methanol and a small amount of dimethyl carbonate azeotrope are separated from the top of the pressure tower, and most of the methanol and a small amount of dimethyl carbonate azeotrope are sent to the atmospheric tower 3 through the pressure tower discharge pipe 12 via the second condenser reboiler 5. After separation in the atmospheric tower, most of the dimethyl carbonate and a small amount of methanol azeotrope are separated from the top of the atmospheric tower, and are sent to the pressure tower 2 through the atmospheric tower top discharge pipe 17 via the condenser 18. The methanol produced from the atmospheric tower kettle is refluxed to the catalytic distillation tower 1 for reuse through the atmospheric tower kettle discharge pipe 19. Among them, the top temperature of catalytic distillation tower 1 is 65-110°C, the bottom temperature is 80-120°C, and the top pressure is 0.1-0.5MpaA; the top temperature of pressure tower 2 is 120-160°C, the bottom temperature is 160-180°C, and the top pressure is 0.8-1.3MpaA; the top temperature of atmospheric pressure tower 3 is 50-65°C, the bottom temperature is 55-70°C, and the top pressure is 0.006-0.1MpaA.

[0024] Example 2

[0025] The preferred embodiment of the present utility model is as shown in the attached Figure 3 As shown: On the basis of Example 1, the bottom of the catalytic distillation tower 1 is provided with a methanol, ethylene glycol or propylene glycol mixture discharge pipe 9, the top material outlet of the catalytic distillation tower 1 is connected to the first condenser reboiler 4 through the catalytic distillation tower discharge pipe 8, and the first branch 11 of the first condenser reboiler is connected to the first feed port 10 of the pressurized tower 2.

[0026] Example 3

[0027] The preferred embodiment of the present utility model is as shown in the attached Figure 3 As shown: Based on Example 1, the bottom of the pressure tower 2 is connected to the dimethyl carbonate product discharge pipe 14, the top material outlet of the pressure tower 2 is connected to the second condenser reboiler 5 through the provided pressure tower discharge pipe 12, and the first branch 16 of the second condenser reboiler is connected to the atmospheric tower feed port 15 of the atmospheric tower 2.

[0028] Example 4

[0029] The preferred embodiment of the present utility model is as shown in the attached Figure 3 As shown: Based on Example 1, the top discharge pipe 17 of the atmospheric tower 3 is connected to the second feed port 20 of the pressure tower through the condenser 18.

[0030] It should be noted that the above content is a further detailed description of the present invention in conjunction with specific implementation methods, and the specific implementation of the present invention cannot be considered to be limited to these descriptions; the connection method of this embodiment does not necessarily limit the present technical solution, but only illustrates one specific working condition. For those skilled in the art of the present invention, it is possible to make several simple improvements and modifications without departing from the concept of the present invention, and these should be considered to fall within the scope of protection of the present invention.

Claims

1. An energy-saving device for producing dimethyl carbonate, comprising a catalytic distillation tower (1), a pressure tower (2), an atmospheric tower (3), and a preheater (13) for heating the pressure tower (2), characterized in that: The catalytic distillation tower (1), the pressure tower (2) and the atmospheric pressure tower (3) are connected via a heat coupling system, wherein the heat coupling system comprises a second condenser-reboiler (5) for heating the catalytic distillation tower (1) and a first condenser-reboiler (4) for heating the atmospheric pressure tower (3); the tower body of the catalytic distillation tower (1) is provided with a catalytic distillation tower feed pipe (6) and a catalytic distillation tower liquid inlet pipe (7); the tower top material outlet of the catalytic distillation tower (1) is connected to the pressure tower (2) via the first condenser-reboiler (4); the tower top material outlet of the pressure tower (2) is connected to the atmospheric pressure tower (3) via the second condenser-reboiler (5); the tower top material outlet of the atmospheric pressure tower (3) is connected to the pressure tower (2) via a condenser (18); and the atmospheric pressure tower kettle discharge pipe (19) of the atmospheric pressure tower (3) is connected to the catalytic distillation tower (1).

2. An energy-saving device for producing dimethyl carbonate according to claim 1, characterized in that, The top material outlet of the catalytic distillation tower (1) is connected to the first condenser-reboiler (4) via a catalytic distillation tower discharge pipe (8), and the first branch (11) of the first condenser-reboiler is connected to the first feed port (10) of the pressurized tower (2).

3. An energy-saving device for producing dimethyl carbonate according to claim 2, characterized in that, The top material outlet of the pressure tower (2) is connected to the second condenser-reboiler (5) via a pressure tower discharge pipe (12), and the first branch (16) of the second condenser-reboiler is connected to the atmospheric tower feed port (15) of the atmospheric tower (3).

4. An energy-saving device for producing dimethyl carbonate according to claim 2, characterized in that, The atmospheric tower top discharge pipe (17) of the atmospheric tower (3) is connected to the second feed port (20) of the pressure tower through a condenser (18).

5. An energy-saving device for producing dimethyl carbonate according to claim 1, characterized in that, The bottom of the catalytic distillation tower (1) is provided with a discharge pipe (9) for a mixture of methanol, ethylene glycol or propylene glycol.

6. An energy-saving device for producing dimethyl carbonate according to claim 1, characterized in that, The bottom of the pressurized tower (2) is connected to a dimethyl carbonate product discharge pipe (14).

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