Low-pressure three-tower triple-effect refining device for crude methanol

Abstract

The low-pressure three-tower triple-effect refining device comprises a pre-rectifying tower, a negative pressure rectifying tower and a pressurizing rectifying tower which are sequentially connected, a pre-tower reboiler and a start-up reboiler are arranged on the lower portion of the pre-rectifying tower, and a pressurizing tower reboiler is arranged on the lower portion of the pressurizing rectifying tower. The lower part of the negative pressure rectifying tower is connected with a negative pressure tower reboiler I and a negative pressure tower reboiler II; a gas phase at the top of the pressurized rectifying tower is used for supplying heat to a pre-tower reboiler and a negative pressure tower reboiler II respectively, and a gas phase at the top of the pre-rectifying tower is used for supplying heat to a negative pressure tower reboiler I; the system comprises three main devices, namely the pre-rectifying tower, the negative pressure rectifying tower and the pressurizing rectifying tower, heat of the pressurizing rectifying tower is used for supplying heat to the pre-tower reboiler and the second negative pressure tower reboiler, heat of the top of the pre-rectifying tower is used for supplying heat to the first negative pressure tower reboiler, heat of each tower top is fully utilized, and the energy consumption is reduced. Compared with the traditional three-tower two-effect process, the multi-effect utilization of the tower top material steam and the optimization of the heat exchange process can reduce the steam unit consumption by 0.29 and realize the great reduction of the energy consumption.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of chemical equipment, in particular to a low-pressure three-tower three-effect refining device for crude methanol. BACKGROUND

[0002] Methanol is an important raw material for producing formaldehyde, acetic acid, chloromethane, methylamine and dimethyl sulfate and many other organic products. Formaldehyde is a raw material for producing many synthetic resins such as phenolic resin, urea-formaldehyde resin and melamine resin; acetic acid is an important organic acid and is widely used in the chemical industry, pharmaceutical industry, food industry and other industries; methanol can be directly used as fuel for automobiles, boilers and the like, and has a high octane rating, clean combustion and can reduce the emission of nitrogen oxides and particulate matter in automobile exhaust; in addition, methanol is an excellent organic solvent that can dissolve many organic compounds and some inorganic compounds, and is often used as a solvent to dissolve resins, pigments and other components in the coating, ink and adhesive industries to adjust the viscosity and drying performance of the products; due to its versatility, methanol plays an extremely important role in the chemical industry.

[0003] Crude methanol usually contains light component impurities such as dimethyl ether and heavy component impurities such as ethanol and water, and therefore needs to be subjected to a refining process to remove various impurities before obtaining refined methanol products that meet quality requirements; the energy consumption in the methanol refining process accounts for about 20-30% of the total energy consumption in production, which has a great impact on the production cost of the products.

[0004] In order to reduce energy consumption, the skilled in the art have been making innovations, and the closest prior art found is as follows: a crude methanol three-tower three-effect heat pump refining process device with application number 202321742454.7 discloses a technical solution comprising a pre-distillation tower, a negative pressure distillation tower and a pressurized distillation tower connected in sequence, and a pre-distillation tower reboiler, a negative pressure distillation tower reboiler and a pressurized distillation tower reboiler connected to the lower part of the pre-distillation tower, the negative pressure distillation tower and the pressurized distillation tower respectively; wherein the gas phase at the top of the pressurized distillation tower is used to heat the pre-distillation tower reboiler, and the gas phase at the top of the negative pressure distillation tower is used to heat the negative pressure distillation tower reboiler; refined methanol is collected from the top of the negative pressure distillation tower and the pressurized distillation tower; the application adopts a three-tower three-effect process, including three main equipment towers, namely the pre-distillation tower, the negative pressure distillation tower and the pressurized distillation tower, the three effects are realized by the pressurized distillation tower itself, the methanol vapor at the top of the pressurized distillation tower is coupled with the pre-distillation tower reboiler to realize the second effect, and the three effects are realized by the heat pump of the negative pressure distillation tower; the traditional process can be modified to greatly reduce energy consumption.

[0005] In the above application, the heat of each tower is utilized, but the use of a heat pump distillation increases the number of moving devices, the investment is relatively high, and the power consumption is large, which is quite different from the multi-effect distillation in the conventional large methanol industry.

[0006] In view of the above, the application provides a new technical solution. Utility Model Content

[0007] This application provides a crude methanol low-pressure three-tower three-effect refining device, comprising a pre-distillation tower, a negative pressure distillation tower, and a pressurized distillation tower connected in sequence. A feed line is provided on one side of the pre-distillation tower. A pre-tower reboiler and a start-up reboiler are connected to the lower part of the pre-distillation tower. A first negative pressure reboiler and a second negative pressure reboiler are connected to the lower part of the negative pressure distillation tower. A pressurized reboiler is connected to the lower part of the pressurized distillation tower. The vapor phase at the top of the pressurized distillation tower is used to heat the pre-tower reboiler and the second negative pressure reboiler, respectively, while the vapor phase at the top of the pre-distillation tower is used to heat the first negative pressure reboiler. Refined methanol is collected from the top of the negative pressure distillation tower and the pressurized distillation tower.

[0008] As a preferred embodiment, the top of the pressurized distillation column is connected to the pre-distillation column reboiler and the negative pressure column reboiler 2 via pressurized column top outlet pipeline 1 and pressurized column top outlet pipeline 2, respectively; the top of the pre-distillation column is connected to the negative pressure column reboiler 1 via the pre-distillation column top outlet pipeline.

[0009] As a preferred embodiment, the output end of the negative pressure tower reboiler is connected to a gas processing device.

[0010] As a preferred embodiment, the gas processing device includes a pre-tower condenser connected to the output end of the reboiler of the negative pressure tower. The pre-tower condenser is connected to a gas-liquid separator. The bottom of the gas-liquid separator is connected to the upper part of the pre-distillation tower through a pre-tower reflux pipeline. A pre-tower reflux pump is installed on the pre-tower reflux pipeline, and a venting gas pipeline is installed on the top of the gas-liquid separator.

[0011] As a preferred embodiment, the output end of the pre-reboiler and the output end of the second negative pressure reboiler are respectively connected to the pressurized column reflux tank. The bottom of the pressurized column reflux tank is connected to the pressurized column refined methanol collection pipeline. A collection pump is installed on the pressurized column refined methanol collection pipeline. The pressurized column reflux pipeline is connected to the pressurized column refined methanol collection pipeline. The pressurized column reflux pipeline is connected to the upper part of the pressurized distillation column.

[0012] As a preferred embodiment, the pressurized tower methanol extraction pipeline is connected to the methanol tank.

[0013] As a preferred embodiment, the top of the negative pressure distillation column is connected to the top reflux tank of the negative pressure column via a top outlet pipeline. A top condenser of the negative pressure column is installed on the top outlet pipeline. The bottom of the top reflux tank of the negative pressure column is connected to the upper part of the negative pressure distillation column via a reflux pipeline. A reflux pump of the negative pressure column is installed on the reflux pipeline. A refined methanol outlet pipeline of the negative pressure column is connected to the reflux pipeline.

[0014] As a preferred embodiment, the methanol extraction pipeline from the negative pressure tower is connected to the methanol tank.

[0015] As a preferred embodiment, the top of the reflux tank at the top of the negative pressure tower is connected to the lower part of the vacuum tail gas absorption tower via a pipeline at the top of the reflux tank. A vacuum pump is installed on the pipeline at the top of the reflux tank, and the bottom of the vacuum tail gas absorption tower is connected to the lower middle part of the negative pressure distillation tower.

[0016] As a preferred embodiment, the upper part of the vacuum exhaust gas absorption tower is provided with a water inlet pipeline, and the top of the vacuum exhaust gas absorption tower is provided with a vacuum exhaust gas discharge pipeline.

[0017] As a preferred embodiment, the feed pipeline is sequentially equipped with feed preheater one, feed preheater two, and feed preheater three.

[0018] As a preferred embodiment, the input end of the pressurized reboiler is connected to the steam pipeline, and the output end of the pressurized reboiler is connected to the condensate pipeline.

[0019] As a preferred embodiment, the bottom of the negative pressure distillation column is connected to the pressurized distillation column via a negative pressure column bottom outlet pipeline, and a negative pressure column bottom pump and a pressurized column preheater are installed on the negative pressure column bottom outlet pipeline.

[0020] As a preferred embodiment, the condensate pipeline passes sequentially through a pressurized tower preheater and a feed preheater.

[0021] As a preferred embodiment, the reboiler of the pressurized distillation column is equipped with a wastewater collection pipeline, which passes through a feed preheater.

[0022] As a preferred embodiment, the methanol extraction pipeline from the pressurized tower passes through a feed preheater.

[0023] This application includes three main equipment towers: a pre-distillation tower, a negative pressure distillation tower, and a pressurized distillation tower. The heat from the pressurized distillation tower is used to heat the reboiler of the pre-distillation tower and the second reboiler of the negative pressure tower, respectively. The heat from the top of the pre-distillation tower is used to heat the first reboiler of the negative pressure tower. By making full use of the heat from the top of each tower, and through multi-effect utilization of the steam from the top of the towers and optimization of the heat exchange process, compared with the traditional three-tower two-effect methanol process, the steam consumption can be reduced by about 0.29, achieving a significant reduction in energy consumption. Compared with the prior art, no additional rotating equipment is required, resulting in relatively lower investment. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of this application;

[0025] 1. Pre-distillation column; 2. Negative pressure distillation column; 3. Pressurized distillation column; 4. Feed line; 5. Feed preheater one; 6. Feed preheater two; 7. Feed preheater three; 8. Pre-distillation column bottom outlet line; 9. Negative pressure column bottom outlet line; 10. Negative pressure column bottom pump; 11. Pressurized column preheater; 12. Wastewater outlet line; 13. Fusel alcohol outlet line; 14. Pre-distillation column reboiler; 15. Negative pressure column reboiler one; 16. Negative pressure column reboiler two; 17. Pressurized column reboiler; 18. Pre-distillation column top outlet line; 19. Refined methanol tank; 20. Pre-distillation column condenser; 21. Gas-liquid separator; 22. Pre-distillation column reflux line; 23. Pre-distillation column reflux pump; 24. 25. Exhaust gas pipeline; 26. Top of pressurized tower extraction pipeline 1; 27. Top of pressurized tower extraction pipeline 2; 28. Pressurized tower reflux tank; 29. ​​Pressurized tower refined methanol extraction pipeline; 30. Extraction pump; 31. Pressurized tower reflux pipeline; 32. Top of negative pressure tower extraction pipeline; 33. Negative pressure tower top reflux tank; 34. Negative pressure tower top condenser; 35. Negative pressure tower reflux pipeline; 36. Negative pressure tower reflux pump; 37. Negative pressure tower refined methanol extraction pipeline; 38. Vacuum tail gas absorption tower; 39. Top pipeline of reflux tank; 40. Vacuum pump; 41. Water inlet pipeline; 42. Vacuum tail gas discharge pipeline; 43. Steam pipeline; 44. Condensate pipeline; 45. Start-up reboiler. Detailed Implementation

[0026] The following is in conjunction with the appendix Figure 1 The specific embodiments of this utility model will be described in detail below. It should be noted that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of this utility model.

[0027] Example 1:

[0028] This embodiment provides a low-pressure three-tower, three-effect refining device for crude methanol, comprising a pre-distillation tower 1, a negative pressure distillation tower 2, and a pressurized distillation tower 3 connected in sequence. A feed line 4 is provided on one side of the pre-distillation tower 1, and feed preheaters 5, 6, and 7 are sequentially installed on the feed line 4 to preheat the feed entering the pre-distillation tower 1. The bottom of the pre-distillation tower 1 is connected to the negative pressure distillation tower 2 via a pre-tower bottom outlet line 8, and the bottom of the negative pressure distillation tower 2 is connected to the pressurized distillation tower 3 via a negative pressure distillation tower bottom outlet line 9. A negative pressure tower bottom pump 10 is installed on the negative pressure tower bottom outlet pipeline 9. Preferably, a pressure tower preheater 11 is also installed on the negative pressure tower bottom outlet pipeline 9 to preheat the material entering the pressure distillation tower 3. A wastewater outlet pipeline 12 is installed in the bottom of the pressure distillation tower 3 to outlet wastewater. Preferably, the wastewater outlet pipeline 12 passes through the feed preheater 6, that is, the wastewater waste heat is used to heat the feed preheater 6. A fusel oil outlet pipeline 13 is provided on one side of the pressure distillation tower 3 to outlet fusel oil for the next process.

[0029] The lower part of the pre-distillation column 1 is connected to a pre-column reboiler 14, the lower part of the negative pressure distillation column 2 is connected to a negative pressure reboiler 15 and a negative pressure reboiler 16, and the lower part of the pressurized distillation column 3 is connected to a pressurized reboiler 17. The vapor phase at the top of the pressurized distillation column 3 is used to heat the pre-column reboiler 14 and the negative pressure reboiler 16, respectively. The top of the pre-distillation column 1 is connected to the negative pressure reboiler 15 via a pre-column top outlet pipeline 18, and the vapor phase at the top of the pre-distillation column 1 is used to heat the negative pressure reboiler 15. Refined methanol is collected from the top of the negative pressure distillation column 2 and the pressurized distillation column 3. Preferably, the refined methanol is stored in a refined methanol tank 19, which is used to collect the collected refined methanol.

[0030] To ensure stable system operation, the output end of the negative pressure tower reboiler 15 is connected to a gas processing device. The gas processing device includes a pre-tower condenser 20 connected to the output end of the negative pressure tower reboiler 15. The pre-tower condenser 20 is connected to a gas-liquid separator 21. The bottom of the gas-liquid separator 21 is connected to the upper part of the pre-distillation tower 1 through a pre-tower reflux pipeline 22. A pre-tower reflux pump 23 is installed on the pre-tower reflux pipeline 22. A purge gas pipeline 24 is installed at the top of the gas-liquid separator 21. The purge gas collection ensures stable system operation, and the proper treatment and recycling of the purge gas can improve the economic efficiency and environmental friendliness of production.

[0031] Example 2:

[0032] This embodiment provides a detailed explanation of how the vapor phase at the top of the pressurized distillation column 3 is used to heat the pre-column reboiler 14 and the negative pressure column reboiler 16, respectively:

[0033] The top of the pressurized distillation column 3 is connected to the pre-reboiler 14 and the negative pressure reboiler 16 via pressurized column top outlet pipeline 25 and pressurized column top outlet pipeline 26, respectively. The output ends of the pre-reboiler 14 and the negative pressure reboiler 16 are connected to the pressurized column reflux tank 27, respectively. The bottom of the pressurized column reflux tank 27 is connected to the pressurized column refined methanol outlet pipeline 28. An outlet pump 29 is installed on the pressurized column refined methanol outlet pipeline 28. A pressurized column reflux pipeline 30 is connected to the pressurized column refined methanol outlet pipeline 28 and is connected to the upper part of the pressurized distillation column 3. Preferably, the pressurized column refined methanol outlet pipeline 28 is connected to the refined methanol tank 19.

[0034] The vapor phase at the top of the pressurized distillation column 3 is used to heat the pre-distillation column reboiler 14 and the negative pressure column reboiler 16, respectively, to provide the heat required for distillation in the pre-distillation column 1 and the negative pressure distillation column 2. The material after heat exchange and condensation flows into the pressurized column reflux tank 27. Part of the material in the pressurized column reflux tank 27 is extracted as refined methanol, and part of it is returned to the top of the pressurized distillation column 3.

[0035] Preferably, the pressurized methanol extraction pipeline 28 passes through the feed preheater 5 to provide heat to the feed preheater 5, thereby utilizing the heat of the refined methanol extracted from the pressurized distillation column 3.

[0036] Example 3:

[0037] This embodiment provides a detailed description of the structure connected to the negative pressure distillation column 2, specifically:

[0038] The top of the negative pressure distillation column 2 is connected to the negative pressure column top reflux tank 32 via a negative pressure column top outlet pipeline 31. A negative pressure column top condenser 33 is installed on the negative pressure column top outlet pipeline 31. The bottom of the negative pressure column top reflux tank 32 is connected to the upper part of the negative pressure distillation column 2 via a negative pressure column reflux pipeline 34. A negative pressure column reflux pump 35 is installed on the negative pressure column reflux pipeline 34. A negative pressure column refined methanol outlet pipeline 36 is connected to the negative pressure column reflux pipeline 34. Preferably, the negative pressure column refined methanol outlet pipeline 36 is connected to the refined methanol tank 19. The refined methanol collected from the top of the negative pressure distillation column 2 is condensed by the negative pressure column top condenser 33 and then sent to the negative pressure column top reflux tank 32. Part of the liquid phase in the negative pressure column top reflux tank 32 is collected as refined methanol, and part of it is returned to the negative pressure distillation column 2.

[0039] Furthermore, to prevent harmful gases from being directly emitted into the atmosphere and polluting the environment, and to prevent the accumulation of flammable, explosive, or toxic gases in the exhaust gas and the resulting safety accidents, ensuring the safety of the production environment; in this embodiment, the top of the negative pressure tower top reflux tank 32 is connected to a vacuum exhaust gas absorption tower 37; specifically, the top of the negative pressure tower top reflux tank 32 is connected to the vacuum exhaust gas absorption tower 37 via a top pipeline 38, a vacuum pump 39 is installed on the top pipeline 38, a water inlet pipeline 40 is installed at the top of the vacuum exhaust gas absorption tower 37, and a vacuum exhaust gas outlet pipeline 41 is installed at the top of the vacuum exhaust gas absorption tower 37; the bottom of the vacuum exhaust gas absorption tower 37 is connected to the lower middle part of the negative pressure distillation tower 2; due to Under negative pressure, the non-condensable gases and volatile components in the reflux tank 32 at the top of the negative pressure tower are transported from the reflux tank 32 to the vacuum tail gas absorption tower 37 under the action of pressure difference. The vacuum tail gas absorption tower 37 introduces an aqueous solution, which is sprayed through a spraying device. The non-condensable gases and volatile components enter from the bottom of the vacuum tail gas absorption tower 37 and come into full contact with the sprayed liquid from top to bottom on the packing layer or tower plate to achieve gas-liquid separation. The gas phase is discharged through the vacuum tail gas discharge pipeline 41, and the liquid phase is returned to the negative pressure distillation tower 2 for recycling and distillation. After absorption and treatment by the vacuum tail gas absorption tower 37, the content of harmful substances is greatly reduced, and the purified gas is discharged from the top of the vacuum tail gas absorption tower 37, meeting the environmental emission standards before being discharged into the atmosphere.

[0040] Example 4:

[0041] This embodiment describes the heating method for the pressurized reboiler 17 and the start-up reboiler 44, specifically:

[0042] The input ends of the pressurized tower reboiler 17 and the start-up reboiler 44 are connected to the steam pipeline 42, which is connected to a steam heating device, etc. The pressurized tower reboiler 17 and the start-up reboiler 44 are heated by steam. In this embodiment, a lower pressure steam of 0.4-0.6 MPa (gauge pressure) is used. The output ends of the pressurized tower reboiler 17 and the start-up reboiler 44 are connected to the condensate pipeline 43. The steam enters the pressurized tower reboiler 17 through the steam pipeline 42 for heat exchange.

[0043] Preferably, in order to further improve the utilization rate of steam, the condensate pipeline 43 passes sequentially through the pressurized tower preheater 11 and the feed preheater 7. After the steam heats the pressurized tower reboiler 17, it enters the pressurized tower preheater 11 to provide heat to the pressurized tower preheater 11, thereby heating the material entering the pressurized distillation tower 3. The material after exchanging heat with the pressurized tower preheater 11 enters the feed preheater 7 to provide heat to the feed preheater 7, thereby preheating the raw material entering the pre-distillation tower 1. The steam after exchanging heat with the feed preheater 7 is discharged as condensate, preferably to a steam condensate tank, etc.

[0044] The working principle of this application is as follows: the raw material is preheated to 70℃-80℃ through feed preheater 5, feed preheater 6, and feed preheater 7 and then conveyed to pre-distillation column 1. The gas phase at the top of pre-distillation column 1 is used to heat the reboiler 15 of the negative pressure column and to provide part of the heat required for distillation in negative pressure distillation column 2. The material after heat exchange enters the gas treatment device for processing and discharges the purge gas to ensure stable operation of the system.

[0045] The bottom product of pre-distillation column 1 is conveyed to negative pressure distillation column 2 for methanol distillation. The vapor phase at the top of negative pressure distillation column 2 is condensed and enters the negative pressure column top reflux tank 32. Part of the material in the negative pressure column top reflux tank 32 is returned to negative pressure distillation column 2, and part is collected as refined methanol. The vapor phase in the negative pressure column top reflux tank 32 is treated by vacuum tail gas absorption tower 37 to meet emission standards before being discharged. The bottom product of negative pressure distillation column 2 is preheated by pressurized column preheater 11 and then conveyed to pressurized distillation column 3. The vapor phase at the top of pressurized distillation column 3 is used to heat the pre-distillation column reboiler 14 and the negative pressure column reboiler 16, respectively, providing the heat required for distillation in pre-distillation column 1 and the negative pressure column. Distillation column 2 provides another portion of the heat required for distillation. The material that exchanges heat with the pre-distillation reboiler 14 and the negative pressure reboiler 16 enters the pressurized column reflux tank 27. The liquid phase in the pressurized column reflux tank 27 first heats the feed preheater 5. Part of the liquid phase after heat exchange is refluxed to the pressurized distillation column 3, and the other part is collected as refined methanol. The bottom product of the pressurized distillation column 3 passes through the feed preheater 6, which provides heat to the feed entering the pre-distillation column 1. The wastewater that exchanges heat with the feed preheater 6 is sent to the wastewater treatment process for treatment. The fusel oil is collected from the side stream of the pressurized distillation column 3 for the next process.

[0046] Steam heats the reboiler 44 to provide heat for the start-up of the pre-distillation column 1. Steam also heats the pressurized column reboiler 17 to provide the heat required for distillation in the pressurized distillation column 3. The condensed steam after heat exchange enters the pressurized column preheater 11 to provide heat for the material entering the pressurized distillation column 3. The condensed steam after heat exchange with the pressurized column preheater 11 enters the feed preheater 7 to provide heat for the feed preheater 7 to heat the raw material entering the pre-distillation column 1. The condensed steam after heat exchange with the feed preheater 7 is discharged to the next process.

[0047] This application includes three main equipment towers: a pre-distillation tower, a negative pressure distillation tower, and a pressurized distillation tower. The heat from the pressurized distillation tower is used to heat the reboiler of the pre-distillation tower and the second reboiler of the negative pressure tower, respectively. The heat from the top of the pre-distillation tower is used to heat the first reboiler of the negative pressure tower. By making full use of the heat from the top of each tower, and through the multi-effect utilization of the steam from the top of the towers and the optimization of the heat exchange process, compared with the traditional three-tower two-effect methanol process, the steam consumption can be reduced by 0.29, resulting in a significant reduction in energy consumption.

[0048] The preferred embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, and these simple modifications all fall within the protection scope of this application.

[0049] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, the various possible combinations in this application will not be described separately.

[0050] Furthermore, various different implementations of this application can be combined in any way, as long as they do not violate the spirit of this application, and such combinations should also be regarded as the content disclosed in this application.

Claims

1. A crude methanol low-pressure three-tower triple-effect refining device, comprising a pre-distillation tower (1), a negative pressure distillation tower (2), and a pressurized distillation tower (3) connected in sequence, wherein a feed line (4) is provided on one side of the pre-distillation tower (1), a pre-tower reboiler (14) and a start-up reboiler (44) are connected to the lower part of the pre-distillation tower (1), and a pressurized tower reboiler (17) is connected to the lower part of the pressurized distillation tower (3), characterized in that, The lower part of the negative pressure distillation column (2) is connected to a negative pressure reboiler one (15) and a negative pressure reboiler two (16); wherein, the gas phase at the top of the pressurized distillation column (3) is used to heat the pre-column reboiler (14) and the negative pressure reboiler two (16), respectively, and the gas phase at the top of the pre-distillation column (1) is used to heat the negative pressure reboiler one (15); the top of the negative pressure distillation column (2) and the pressurized distillation column (3) produces refined methanol.

2. The crude methanol low-pressure three-tower three-effect refining device according to claim 1, characterized in that, The top of the pressurized distillation column (3) is connected to the pre-column reboiler (14) and the negative pressure column reboiler (16) through the pressurized column top outlet pipeline 1 (25) and the pressurized column top outlet pipeline 2 (26), respectively; the top of the pre-column distillation column (1) is connected to the negative pressure column reboiler 1 (15) through the pre-column top outlet pipeline (18).

3. The crude methanol low-pressure three-tower three-effect refining device according to claim 1, characterized in that, The output end of the negative pressure tower reboiler (15) is connected to the gas processing device.

4. The crude methanol low-pressure three-tower three-effect refining device according to claim 1, characterized in that, The output end of the pre-tower reboiler (14) and the output end of the negative pressure tower reboiler (16) are respectively connected to the pressurized tower reflux tank (27). The bottom of the pressurized tower reflux tank (27) is connected to the pressurized tower refined methanol collection pipeline (28). The pressurized tower refined methanol collection pipeline (28) is equipped with a collection pump (29). The pressurized tower refined methanol collection pipeline (28) is connected to the pressurized tower reflux pipeline (30). The pressurized tower reflux pipeline (30) is connected to the upper part of the pressurized distillation tower (3).

5. The crude methanol low-pressure three-tower three-effect refining device according to claim 1, characterized in that, The top of the negative pressure distillation column (2) is connected to the negative pressure column top reflux tank (32) via a negative pressure column top outlet pipeline (31). A negative pressure column top condenser (33) is installed on the negative pressure column top outlet pipeline (31). The bottom of the negative pressure column top reflux tank (32) is connected to the upper part of the negative pressure distillation column (2) via a negative pressure column reflux pipeline (34). A negative pressure column reflux pump (35) is installed on the negative pressure column reflux pipeline (34). A negative pressure column refined methanol outlet pipeline (36) is connected to the negative pressure column reflux pipeline (34).

6. The crude methanol low-pressure three-tower three-effect refining device according to claim 5, characterized in that, The top of the negative pressure tower top reflux tank (32) is connected to the bottom of the vacuum tail gas absorption tower (37) through the top pipeline (38) of the reflux tank. A vacuum pump (39) is installed on the top pipeline (38) of the reflux tank. The bottom of the vacuum tail gas absorption tower (37) is connected to the middle and lower part of the negative pressure distillation tower (2).

7. The crude methanol low-pressure three-tower three-effect refining device according to claim 1, characterized in that, The feed pipeline (4) is provided with feed preheater one (5), feed preheater two (6) and feed preheater three (7) in sequence.

8. The crude methanol low-pressure three-tower three-effect refining device according to claim 7, characterized in that, The input end of the pressurized tower reboiler (17) is connected to the steam pipeline (42), and the output end of the pressurized tower reboiler (17) is connected to the condensate pipeline (43).

9. The crude methanol low-pressure three-tower three-effect refining device according to claim 7, characterized in that, The pressurized distillation column (3) is equipped with a wastewater outlet pipeline (12), which passes through the feed preheater (6).

10. A crude methanol low-pressure three-tower three-effect refining device according to claim 8, characterized in that, The bottom of the negative pressure distillation column (2) is connected to the pressurized distillation column (3) through the negative pressure column bottom outlet pipeline (9). The negative pressure column bottom outlet pipeline (9) is equipped with a negative pressure column bottom pump (10) and a pressurized column preheater (11). The condensate pipeline (43) passes through the pressurized column preheater (11) and the feed preheater (7) in sequence.

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