A device for improving the thermal efficiency of a dimethyl carbonate distillation system
By adding a heat exchanger at the top of the propylene carbonate distillation column and adjusting the pressure and reflux ratio of the pressurized distillation column, the problem of high energy consumption in dimethyl carbonate production was solved, and the system's thermal efficiency was improved while energy consumption was reduced.
Patent Information
- Application Number
- CN202522416308.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-14
- Publication Date
- 2026-11-06
- Estimated Expiration
- 2035-11-14
AI Technical Summary
In the existing dimethyl carbonate production process, the separation of dimethyl carbonate and methanol azeotropes is energy-intensive, and the cooling energy at the top of the propylene carbonate distillation column is severely wasted, resulting in low system thermal efficiency.
By adding a heat exchanger at the top of the propylene carbonate distillation column, heat exchange between the gaseous propylene carbonate and the bottom material of the dimethyl carbonate reaction column is achieved, reducing the cooling load at the top of the column. In the pressurized dimethyl carbonate distillation column, the pressure and reflux ratio are adjusted to optimize process parameters and reduce energy consumption.
This reduced energy consumption in dimethyl carbonate production, improved system thermal efficiency, reduced heat loss in the propylene carbonate unit, increased vacuum levels, and achieved energy-saving results.
Smart Images
Figure CN224938169U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of dimethyl carbonate production technology, and in particular to a device for improving the thermal efficiency of a dimethyl carbonate distillation system. Background Technology
[0002] The dimethyl carbonate (DMC) production process utilizes a transesterification reaction. Furthermore, the combined DMC and propylene carbonate unit can reduce costs and increase efficiency. During the reaction, excess methanol and dimethyl carbonate form an azeotrope at ambient temperature and pressure. The process design involves pressurized distillation to reduce the DMC content in the azeotrope, thereby separating methanol and DMC. Currently, the pressurized distillation tower operates at 0.55 MPa, 118°C, and a reflux ratio of 1.3:1.
[0003] The propylene carbonate distillation unit is a negative pressure distillation unit, which requires controlling the reflux temperature at the top of the distillation column to maintain the vacuum of the system. This part of the vapor phase heat is cooled by a water cooler to reduce the reflux temperature, resulting in energy waste. Utility Model Content
[0004] The purpose of this invention is to address the aforementioned deficiencies in the existing technology by providing a device for improving the thermal efficiency of a dimethyl carbonate distillation system. This device increases the pressure of the dimethyl carbonate pressurized distillation column, altering the azeotropic composition of methanol and dimethyl carbonate, and reducing the reflux ratio to achieve energy savings. Furthermore, by adding a top heat exchanger, thermal coupling is achieved between the propylene carbonate top vapor phase and dimethyl carbonate, thereby improving the system's thermal efficiency. This reduces energy consumption in dimethyl carbonate production, increases the vacuum level of propylene carbonate, and minimizes heat loss in the propylene carbonate unit.
[0005] The present invention relates to a device for improving the thermal efficiency of a dimethyl carbonate distillation system. The technical solution includes: a propylene carbonate distillation column (1), a top heat exchanger (2), a top water cooler (3), a material storage tank (4) for the bottom of a dimethyl carbonate reaction column, a dimethyl carbonate transfer pump (5), a propylene carbonate distillation column reflux tank (8), a reflux pump (9), a dimethyl carbonate pressurized distillation column (10), a reaction column bottom heat exchanger (11), a methanol recovery column heat exchanger (12), a pressurized column reflux tank (13), and a dimethyl carbonate pressurized distillation column reflux pump (16). The top vapor phase of the propylene carbonate distillation column (1) is connected to the propylene carbonate distillation column reflux tank (8) via pipelines, the top heat exchanger (2), and the top water cooler (3). The bottom of the propylene carbonate distillation column reflux tank (8) is connected via pipelines... The reflux pump (9) is connected to the upper side line of the propylene carbonate distillation column (1); the tube side inlet of the top heat exchanger (2) is connected to the lower end of the material storage tank (4) of the dimethyl carbonate reaction column via a pipeline and the dimethyl carbonate transfer pump (5); the tube side outlet of the top heat exchanger (2) is connected to the dimethyl carbonate pressurized distillation column (10) via a pipeline; the top gas phase of the dimethyl carbonate pressurized distillation column (10) is split into two paths via a pipeline, one path is connected to the pressurized column reflux tank (13) via the reaction column bottom heat exchanger (11), and the other path is connected to the pressurized column reflux tank (13) via the methanol recovery column heat exchanger (12); the bottom of the pressurized column reflux tank (13) is connected to the upper side line of the dimethyl carbonate pressurized distillation column (10) via a pipeline and the methyl carbonate pressurized distillation column reflux pump (16).
[0006] Preferably, the top gas phase of the propylene carbonate distillation column (1) is connected to the shell-side inlet of the top heat exchanger (2) via a pipeline, and the shell-side outlet of the top heat exchanger (2) is connected to the shell-side inlet of the top water cooler (3) via a pipeline.
[0007] Preferably, the shell-side outlet of the above-mentioned top water cooler (3) is connected to the reflux tank (8) of the propylene carbonate distillation column via a pipeline, the tube-side inlet of the top water cooler (3) is connected to the circulating water pipe (6), and the tube-side outlet of the top water cooler (3) is connected to the circulating return water pipe (7).
[0008] Preferably, the pipeline connected to the outlet end of the dimethyl carbonate delivery pump (5) is divided into two paths. One path is connected to the top of the dimethyl carbonate pressurized distillation column (10) through the feed pipeline and the first control valve (17), and the other path is connected to the tube side inlet of the top heat exchanger (2) through the heat exchange pipeline and the third control valve (19).
[0009] Preferably, the tube-side outlet of the above-mentioned tower top heat exchanger (2) is connected to the feed line via a pipeline and a second control valve (18).
[0010] Preferably, the pipeline connected to the output end of the reflux pump (16) of the methyl carbonate pressurized distillation column is divided into two paths. One path is connected to the upper side line of the dimethyl carbonate pressurized distillation column (10), and a reflux flow meter (14) is installed on the pipeline. The other path is connected to the external transmission pipeline, and a top extraction flow meter (15) is installed on the external transmission pipeline.
[0011] The beneficial effects of this utility model are: This invention adds a top heat exchanger before the water cooler at the top of the propylene carbonate distillation column, allowing heat exchange between the gaseous propylene carbonate and the material from the bottom of the dimethyl carbonate reaction column. This reduces the cooling load at the top of the propylene carbonate column and significantly improves the vacuum at the top. Furthermore, by adjusting the process control parameters within the design pressure range of the dimethyl carbonate pressurized distillation column, the column pressure is increased. This increased pressure at the top reduces the dimethyl carbonate content in the top azeotrope. The reflux ratio of the pressurized column can also be adjusted to reduce the steam consumption at the bottom of the column, thereby reducing the separation load of the subsequent stages and lowering the energy consumption of the unit, ultimately improving the thermal efficiency of the system. Attached Figure Description
[0012] Figure 1 This is a connection diagram of Embodiment 1 of this utility model; Figure 2 This is a connection diagram of Embodiment 2 of this utility model; In the diagram above: 1. Propylene carbonate distillation column; 2. Top heat exchanger; 3. Top water cooler; 4. Dimethyl carbonate reaction column bottom material storage tank; 5. Dimethyl carbonate transfer pump; 6. Circulating water pipe; 7. Circulating water return pipe; 8. Propylene carbonate distillation column reflux tank; 9. Reflux pump; 10. Dimethyl carbonate pressurized distillation column; 11. Reaction column bottom heat exchanger; 12. Methanol recovery column heat exchanger; 13. Pressurized column reflux tank; 14. Reflux flow meter; 15. Top flow meter; 16. Dimethyl carbonate pressurized distillation column reflux pump; 17. First control valve; 18. Second control valve; 19. Third control valve. Detailed Implementation
[0013] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0014] Example 1, referring to Figure 1The present invention relates to a device for improving the thermal efficiency of a dimethyl carbonate distillation system. The technical solution includes: a propylene carbonate distillation column 1, a top heat exchanger 2, a top water cooler 3, a dimethyl carbonate reaction column bottom material storage tank 4, a dimethyl carbonate transfer pump 5, a propylene carbonate distillation column reflux tank 8, a reflux pump 9, a dimethyl carbonate pressurized distillation column 10, a reaction column bottom heat exchanger 11, a methanol recovery column heat exchanger 12, a pressurized column reflux tank 13, and a dimethyl carbonate pressurized distillation column reflux pump 16. The top vapor phase of the propylene carbonate distillation column 1 is connected to the propylene carbonate distillation column reflux tank 8 via pipelines, the top heat exchanger 2, and the top water cooler 3. The bottom of the propylene carbonate distillation column reflux tank 8 is connected to... The reflux pump 9 is connected to the upper side line of the propylene carbonate distillation column 1; the tube-side inlet of the top heat exchanger 2 is connected to the lower end of the material storage tank 4 of the dimethyl carbonate reaction column via a pipeline and the dimethyl carbonate transfer pump 5, and the tube-side outlet of the top heat exchanger 2 is connected to the dimethyl carbonate pressurized distillation column 10 via a pipeline. The top gas phase of the dimethyl carbonate pressurized distillation column 10 is split into two paths via a pipeline, one path is connected to the pressurized column reflux tank 13 via the reaction column bottom heat exchanger 11, and the other path is connected to the pressurized column reflux tank 13 via the methanol recovery column heat exchanger 12. The bottom of the pressurized column reflux tank 13 is connected to the upper side line of the dimethyl carbonate pressurized distillation column 10 via a pipeline and the methyl carbonate pressurized distillation column reflux pump 16.
[0015] The top vapor phase of the aforementioned propylene carbonate distillation column 1 is connected to the shell-side inlet of the top heat exchanger 2 via a pipeline, and the shell-side outlet of the top heat exchanger 2 is connected to the shell-side inlet of the top water cooler 3 via a pipeline.
[0016] The shell-side outlet of the aforementioned top water cooler 3 is connected to the reflux tank 8 of the propylene carbonate distillation column via a pipeline, the tube-side inlet of the top water cooler 3 is connected to the circulating water pipe 6, and the tube-side outlet of the top water cooler 3 is connected to the circulating return water pipe 7.
[0017] The pipeline connected to the output end of the reflux pump 16 of the aforementioned methyl carbonate pressurized distillation column is divided into two lines. One line is connected to the upper side line of the dimethyl carbonate pressurized distillation column 10, and a reflux flow meter 14 is installed on the pipeline. The other line is connected to the external transmission pipeline, and a top extraction flow meter 15 is installed on the external transmission pipeline.
[0018] When using this utility model, In the propylene carbonate distillation column 1, a heat exchanger 2 is added before the top water cooler 3 to exchange heat between the gaseous propylene carbonate and the material in the temporary storage tank 4 of the dimethyl carbonate reaction column. After the heat exchange, the 125°C gaseous medium at the top of the propylene carbonate distillation column is condensed into a 100°C liquid medium, which reduces the cooling load at the top of the propylene carbonate column and significantly improves the vacuum at the top of the column. The dimethyl carbonate pressurized distillation column 10 adjusts the process control parameters within the design pressure range, slowly increasing the column pressure from 0.55 MPa to 0.7 MPa. After the pressure at the top of the pressurized column is increased, the dimethyl carbonate content in the azeotrope at the top of the column is reduced. The reflux ratio of the pressurized column can be adjusted to reduce the steam consumption in the bottom of the column, while reducing the separation load of the subsequent stage, thus reducing the energy consumption of the unit and achieving the goal of improving the thermal efficiency of the unit.
[0019] Example 2: The present invention discloses a device for improving the thermal efficiency of a dimethyl carbonate distillation system. The technical solution includes: a propylene carbonate distillation column 1, a top heat exchanger 2, a top water cooler 3, a dimethyl carbonate reaction column bottom material storage tank 4, a dimethyl carbonate transfer pump 5, a propylene carbonate distillation column reflux tank 8, a reflux pump 9, a dimethyl carbonate pressurized distillation column 10, a reaction column bottom heat exchanger 11, a methanol recovery column heat exchanger 12, a pressurized column reflux tank 13, and a dimethyl carbonate pressurized distillation column reflux pump 16. The top gas phase of the propylene carbonate distillation column 1 is connected to the propylene carbonate distillation column reflux tank 8 via pipelines, the top heat exchanger 2, and the top water cooler 3. The bottom of the propylene carbonate distillation column reflux tank 8 is connected via pipes... The line and reflux pump 9 are connected to the upper side line of the propylene carbonate distillation column 1; the tube-side inlet of the top heat exchanger 2 is connected to the lower end of the material storage tank 4 of the dimethyl carbonate reaction column via a pipeline and the dimethyl carbonate transfer pump 5, and the tube-side outlet of the top heat exchanger 2 is connected to the dimethyl carbonate pressurized distillation column 10 via a pipeline. The top gas phase of the dimethyl carbonate pressurized distillation column 10 is split into two paths via a pipeline, one path is connected to the pressurized column reflux tank 13 via the reaction column bottom heat exchanger 11, and the other path is connected to the pressurized column reflux tank 13 via the methanol recovery column heat exchanger 12. The bottom of the pressurized column reflux tank 13 is connected to the upper side line of the dimethyl carbonate pressurized distillation column 10 via a pipeline and the methyl carbonate pressurized distillation column reflux pump 16.
[0020] The difference from Example 1 is: Reference Figure 2 In this embodiment, the pipeline connected to the outlet end of the dimethyl carbonate delivery pump 5 is divided into two paths. One path is connected to the top of the dimethyl carbonate pressurized distillation column 10 via a feed pipeline and a first control valve 17. The other path is connected to the tube-side inlet of the top heat exchanger 2 via a heat exchange pipeline and a third control valve 19. The tube-side outlet of the top heat exchanger 2 is connected to the feed pipeline via a pipeline and a second control valve 18. This allows the material from the material storage tank 4 at the bottom of the dimethyl carbonate reaction column to be easily adjusted as needed. It can be directly fed into the dimethyl carbonate pressurized distillation column 10, or it can be fed into the dimethyl carbonate pressurized distillation column 10 after heat exchange in the top heat exchanger 2, or it can be fed into the dimethyl carbonate reaction column.
[0021] The above description is merely a preferred embodiment of this utility model. Any person skilled in the art may modify this utility model or modify it into an equivalent technical solution using the technical solutions described above. Therefore, any simple modifications or equivalent transformations made based on the technical solutions of this utility model are within the scope of protection claimed by this utility model.
Claims
1. A device for improving the thermal efficiency of a dimethyl carbonate distillation system, characterized in that: The dimethyl carbonate distillation column includes a propylene carbonate distillation column (1), a top heat exchanger (2), a top water cooler (3), a dimethyl carbonate reaction column bottom material storage tank (4), a dimethyl carbonate transfer pump (5), a propylene carbonate distillation column reflux tank (8), a reflux pump (9), a dimethyl carbonate pressurized distillation column (10), a reaction column bottom heat exchanger (11), a methanol recovery column heat exchanger (12), a pressurized column reflux tank (13), and a dimethyl carbonate pressurized distillation column reflux pump (16). The top vapor phase of the propylene carbonate distillation column (1) is connected to the propylene carbonate distillation column reflux tank (8) via pipelines, the top heat exchanger (2), and the top water cooler (3). The bottom of the propylene carbonate distillation column reflux tank (8) is connected to the propylene carbonate distillation column via pipelines and the reflux pump (9). The upper side line of the tower (1); the tube side inlet of the tower top heat exchanger (2) is connected to the lower end of the material storage tank (4) of the dimethyl carbonate reaction tower via a pipeline and a dimethyl carbonate transfer pump (5), and the tube side outlet of the tower top heat exchanger (2) is connected to the dimethyl carbonate pressurized distillation tower (10) via a pipeline. The top gas phase of the dimethyl carbonate pressurized distillation tower (10) is divided into two paths via a pipeline. One path is connected to the pressurized tower reflux tank (13) via the reaction tower bottom heat exchanger (11), and the other path is connected to the pressurized tower reflux tank (13) via the methanol recovery tower heat exchanger (12). The bottom of the pressurized tower reflux tank (13) is connected to the upper side line of the dimethyl carbonate pressurized distillation tower (10) via a pipeline and a methyl carbonate pressurized distillation tower reflux pump (16).
2. The device for improving the thermal efficiency of a dimethyl carbonate distillation system according to claim 1, characterized in that: The top gas phase of the propylene carbonate distillation column (1) is connected to the shell-side inlet of the top heat exchanger (2) via a pipeline, and the shell-side outlet of the top heat exchanger (2) is connected to the shell-side inlet of the top water cooler (3) via a pipeline.
3. The device for improving the thermal efficiency of a dimethyl carbonate distillation system according to claim 2, characterized in that: The shell-side outlet of the top water cooler (3) is connected to the reflux tank (8) of the propylene carbonate distillation column via a pipeline. The tube-side inlet of the top water cooler (3) is connected to the circulating water pipe (6), and the tube-side outlet of the top water cooler (3) is connected to the circulating return water pipe (7).
4. The device for improving the thermal efficiency of a dimethyl carbonate distillation system according to claim 3, characterized in that: The pipeline connected to the outlet end of the dimethyl carbonate delivery pump (5) is divided into two paths. One path is connected to the top of the dimethyl carbonate pressurized distillation column (10) through the feed pipeline and the first control valve (17), and the other path is connected to the tube inlet of the heat exchanger (2) at the top of the column through the heat exchange pipeline and the third control valve (19).
5. The device for improving the thermal efficiency of a dimethyl carbonate distillation system according to claim 4, characterized in that: The tube-side outlet of the top heat exchanger (2) is connected to the feed line via a pipeline and a second control valve (18).
6. The device for improving the thermal efficiency of a dimethyl carbonate distillation system according to claim 1, characterized in that: The pipeline connected to the output end of the methyl carbonate pressurized distillation column reflux pump (16) is divided into two paths. One path is connected to the upper side line of the dimethyl carbonate pressurized distillation column (10), and a reflux flow meter (14) is installed on the pipeline. The other path is connected to the external transmission pipeline, and a top extraction flow meter (15) is installed on the external transmission pipeline.