Crude methanol cascade heat pump energy-saving device

Abstract

The utility model provides a crude methanol cascade heat pump energy-saving device which comprises a pre-rectifying tower and a normal pressure rectifying tower which are connected in sequence, the bottom of the pre-rectifying tower is connected with a pre-tower reboiler, the normal pressure rectifying tower is connected with N normal pressure tower reboilers, the top of the pre-rectifying tower is connected with a pre-tower heat pump, the pre-tower heat pump is connected with the pre-tower reboiler, and the N normal pressure tower reboilers are connected with N normal pressure tower reboilers. The pre-tower reboiler is connected with a pre-tower reflux device, the top of the normal-pressure rectifying tower is connected with M normal-pressure tower heat pumps, M is equal to N, and M and N are greater than or equal to 2; the atmospheric tower heat pumps are respectively connected with atmospheric tower reboilers, and the N atmospheric tower reboilers are all connected with a refined methanol extraction device; according to the invention, the traditional methanol rectification process is changed, the tower is supplied with heat in a stepped manner through a steam direct compression type heat pump energy-saving technology at the top of the normal-pressure rectification tower, efficient stepped recovery of waste heat energy at the top of the normal-pressure rectification tower is facilitated, production operation is facilitated, and energy consumption is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of chemical equipment, and in particular to a crude methanol cascade heat pump energy-saving device. Background Art

[0002] Methanol is an important organic chemical raw material. Methanol that has not been distilled contains more impurities, which affect the quality of methanol. Therefore, distillation is a key link in the production of methanol. In recent years, with the development of downstream methanol derivatives, higher requirements have been put forward for methanol distillation. On the one hand, the process directly affects the quality and output of the end product. On the other hand, reducing the energy consumption of the distillation link is an important task for enterprises to save costs and achieve emission reduction targets.

[0003] In the traditional methanol distillation process, most of the methanol distillation units adopt a three-tower double-effect methanol distillation process, that is, a three-stage process of a pre-distillation tower, a pressure distillation tower, and an atmospheric distillation tower. The energy consumption for producing one ton of refined methanol is about 1.2 tons of steam. At present, a series of new technologies have emerged in China, which use multi-effect distillation to design and optimize the tower top steam heat exchange network to match various levels of energy. The steam consumption is 0.7-1.2 tons / refined methanol. In addition, the existing energy-saving processes are mostly thermal coupling energy saving or a combination of heat pumps and thermal coupling processes. There are many equipment, long processes, large land area, and complex waste heat recovery methods. Methanol is easy to scale in the heat exchange network, affecting the operation of the atmospheric tower.

[0004] After searching, the applicant has found the closest comparative documents as follows:

[0005] Comparative Document 1: A three-tower three-effect crude methanol refining process system with application number 201820870873.1 provides a technical solution, including a pre-distillation tower, a pressure distillation tower and an atmospheric distillation tower, at least two reboilers are provided at the bottom of the pre-distillation tower, and the bottom extraction port of the pre-distillation tower is connected to the feed port of the pressure distillation tower; the top extraction port of the pressure distillation tower is divided into two branches: one is connected to one of the reboilers at the bottom of the pre-distillation tower and returns to the reflux tank connected to the pressure distillation tower, and the other is connected to the reboiler at the bottom of the atmospheric distillation tower and returns to the reflux tank connected to the pressure distillation tower; the reflux tank of the pressure distillation tower is divided into at least two branches: one is connected to the top reflux of the pressure distillation tower, and the other is connected to the product extraction device; the bottom extraction port of the pressure distillation tower is connected to the feed port of the atmospheric distillation tower; the top extraction port of the atmospheric distillation tower is connected to the product extraction device. The utility model is capable of reducing the energy consumption of the methanol refining system and reducing the equipment investment. In the application, the heat coupling between the pressurized distillation tower M2 and the atmospheric distillation tower M3 is a two-effect distillation, and the heat coupling between the pressurized distillation tower M2 and the pre-distillation tower M1 is a three-effect distillation. The application adopts a three-tower three-effect crude methanol refining process system, which has a better refining effect than a three-tower double-effect system. However, the heat pump technology is not introduced in the application document, and it has no economic advantage for areas with high steam prices and low electricity prices.

[0006] In summary, this application provides a new technical solution. Utility Model Content

[0007] The present application provides a crude methanol cascade heat pump energy-saving device, comprising a pre-distillation tower and an atmospheric distillation tower connected in sequence, wherein the bottom of the pre-distillation tower is connected to a pre-tower reboiler, the atmospheric distillation tower is connected to N atmospheric distillation tower reboilers, the top of the pre-distillation tower is connected to a pre-tower heat pump, the pre-tower heat pump is connected to the pre-tower reboiler, the pre-tower reboiler is connected to a pre-tower reflux device, the top of the atmospheric distillation tower is connected to M atmospheric distillation tower heat pumps, M=N, and M, N≥2; each atmospheric distillation tower heat pump is respectively connected to an atmospheric distillation tower reboiler, and the N atmospheric distillation tower reboilers are all connected to a refined methanol extraction device.

[0008] As a preferred embodiment, the pre-tower reflux device includes a pre-tower top cooler connected to a pre-tower reboiler, the pre-tower top cooler is connected to a pre-tower reflux tank, a relaxation gas pipeline is provided on the top of the pre-tower reflux tank, an extraction water pipeline is connected to one side of the pre-tower reflux tank, and the bottom of the pre-tower reflux tank is connected to the middle and upper part of the pre-distillation tower.

[0009] As a preferred solution, the bottom of the pre-tower reflux tank is connected to the pre-distillation tower through a buffer tank bottom pipeline, and a pre-tower reflux pump is provided on the buffer tank bottom pipeline.

[0010] As a preferred embodiment, the refined methanol production device includes an atmospheric tower top condenser, which is connected to the atmospheric tower top reflux tank, the bottom of the atmospheric tower top reflux tank is connected to the refined methanol production pipeline, the refined methanol production pipeline is connected to the atmospheric tower reflux pipeline, and the atmospheric tower reflux pipeline is connected to the middle and upper part of the atmospheric distillation tower.

[0011] As a preferred solution, the refined methanol production pipeline is provided with an atmospheric pressure tower refined methanol production pump.

[0012] As a preferred solution, the refined methanol production pipeline is connected to the refined methanol tank.

[0013] As a preferred solution, a stripping tower is connected to one side of the atmospheric distillation tower.

[0014] As a preferred embodiment, the top of the stripping tower is connected to a stripping tower top condenser, the stripping tower top condenser is connected to a stripping tower top reflux tank, the bottom of the stripping tower top reflux tank is connected to a stripping tower refined methanol production pipeline, the stripping tower refined methanol production pipeline is connected to a stripping tower reflux pipeline, and the stripping tower reflux pipeline is connected to the middle and upper part of the stripping tower.

[0015] As a preferred solution, a stripping tower refined methanol production pump is provided on the stripping tower refined methanol production pipeline.

[0016] As a preferred solution, one side of the stripping tower is connected to a fusel alcohol extraction pipeline, and the bottom of the stripping tower is connected to a wastewater pipeline.

[0017] As a preferred solution, the wastewater pipeline is connected to a wastewater reflux pipeline, and the wastewater reflux pipeline is connected to the middle and lower part of the atmospheric distillation tower.

[0018] As a preferred scheme, N=2, which respectively represents the atmospheric pressure tower kettle reboiler and the atmospheric pressure tower second reboiler; M=2, which respectively represents the atmospheric pressure tower heat pump 1 and the atmospheric pressure tower heat pump 2, wherein the atmospheric pressure tower heat pump 1 is connected to the atmospheric pressure tower kettle reboiler, and the atmospheric pressure tower heat pump 2 is connected to the atmospheric pressure tower second reboiler.

[0019] As a preferred scheme, N=3, which are respectively the atmospheric pressure tower kettle reboiler, the atmospheric pressure tower second reboiler, and the atmospheric pressure tower intermediate reboiler; M=3, which are respectively the atmospheric pressure tower heat pump 1, the atmospheric pressure tower heat pump 2, and the atmospheric pressure tower heat pump 3, wherein the atmospheric pressure tower heat pump 1 is connected to the atmospheric pressure tower kettle reboiler, the atmospheric pressure tower heat pump 2 is connected to the atmospheric pressure tower second reboiler, and the atmospheric pressure tower heat pump 3 is connected to the atmospheric pressure tower intermediate reboiler.

[0020] This application has the following beneficial effects:

[0021] 1. The traditional methanol distillation process has been changed. The direct compression heat pump energy-saving technology of the atmospheric distillation tower top steam is used to supply heat to the tower steps, which is conducive to the efficient step-by-step recovery of the waste heat energy at the top of the atmospheric distillation tower, facilitating production operations and reducing energy consumption;

[0022] 2. The step heat exchange of atmospheric distillation tower can effectively improve the extraction rate of products, reduce energy consumption, reduce heat loss, and save investment;

[0023] 3. Rationally distribute the load of the atmospheric distillation tower system, integrate heat, realize cascade utilization of energy, optimize the heat exchange process, and reduce energy consumption to meet the requirements of large-scale equipment and diversified methanol production; try to recover the medium and low temperature heat at the top of the atmospheric distillation tower and realize cascade heat combination with the downstream reboiler, make full use of low-temperature waste heat and use new insulation materials to reduce heat dissipation losses;

[0024] 4. Combining heat pump technology with traditional distillation process to fully recover the latent heat of the steam at the top of the pre-distillation tower and the atmospheric distillation tower can reduce the use of cooling water and hot steam in the distillation system. The cascade heat exchange at the top of the atmospheric distillation tower can effectively increase production capacity, improve product purity, reduce product costs, and achieve the purpose of energy saving and consumption reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the first embodiment of the present application;

[0026] Figure 2 It is a structural diagram of the second embodiment of the present application;

[0027] 1. Pre-distillation tower 2. Atmospheric distillation tower 3. Pre-distillation tower kettle pipeline 4. Pre-tower reboiler

[0028] 5. Pre-tower heat pump 6. Pre-tower top cooler 7. Pre-tower reflux tank 8. Relaxation gas pipeline

[0029] 9. Extraction water pipeline 10. Buffer tank bottom pipeline 11. Pre-tower reflux pump 12. Feed pipeline

[0030] 13. Atmospheric pressure tower top condenser 14. Atmospheric pressure tower top reflux tank 15. Refined methanol extraction pipeline

[0031] 16. Atmospheric tower reflux pipeline 17. Atmospheric tower refined methanol extraction pump 18. Refined methanol tank

[0032] 19. Stripping tower 20. Atmospheric distillation tower side line 21. Stripping tower top condenser

[0033] 22. Reflux tank at the top of stripping tower 23. Refined methanol extraction pipe of stripping tower 24. Reflux pipeline of stripping tower

[0034] 25. Stripping tower refined methanol extraction pump 26. Wastewater pipeline 27. Atmospheric pressure tower kettle reboiler

[0035] 28. Atmospheric tower second reboiler 29. Atmospheric tower heat pump 1 30. Atmospheric tower heat pump 2

[0036] 31. Atmospheric tower intermediate reboiler 32. Atmospheric tower heat pump 3 33. Atmospheric distillation tower wastewater pipeline

[0037] 34. Wastewater reflux pipeline 35. Fusel alcohol production pipeline. DETAILED DESCRIPTION

[0038] The following is combined with Figure 1 , Figure 2 The specific implementation of the utility model is described in detail. It should be noted that the specific implementation described here is only used to illustrate and explain the utility model, and is not used to limit the utility model.

[0039] Embodiment 1:

[0040] The present embodiment provides a crude methanol cascade heat pump energy-saving device, comprising a pre-distillation tower 1 and an atmospheric distillation tower 2 connected in sequence, the bottom of the pre-distillation tower 1 is connected to the middle and upper part of the atmospheric distillation tower 3 through a pre-distillation tower kettle pipeline 3; a pre-distillation tower 1 is arranged in front of the atmospheric distillation tower 2, the pre-distillation tower 1 is used to remove dimethyl ether, add water for extraction, remove light components with a boiling point close to that of methanol, and remove light components in organic impurities, the bottom of the pre-distillation tower 1 is connected to a pre-tower reboiler 4, the top of the pre-distillation tower 1 is connected to a pre-tower heat pump 5, the pre-tower heat pump 5 is connected to the pre-tower reboiler 4, and the pre-tower reboiler 4 is connected to a pre-tower reflux device; more specifically, the pre-tower reflux device comprises a pre-tower top cooler 6 connected to the pre-tower reboiler 4, and the pre-tower top cooler 6 is connected to the pre-tower reboiler 4. A pre-tower reflux tank 7 is connected, a relaxation gas pipeline 8 is arranged on the top of the pre-tower reflux tank 7, an extraction water pipeline 9 is connected to one side of the pre-tower reflux tank 7, and is used to introduce extraction water into the pre-tower reflux tank 7. The bottom of the pre-tower reflux tank 7 is connected to the upper and middle part of the pre-distillation tower 1 through a buffer tank bottom pipeline 10, and a pre-tower reflux pump 11 is arranged on the buffer tank bottom pipeline 10; the pre-distillation tower 1 introduces crude methanol to be distilled through a feed pipeline 12, and the gas phase at the top of the pre-distillation tower 1 is pressurized and heated by the pre-tower heat pump 5 and then used as a heat source in the pre-tower reboiler 4. The gas-liquid mixed phase after heat exchange is cooled by the pre-tower top cooler 6 and then enters the pre-tower reflux tank 7. After the extraction water is introduced into the pre-tower reflux tank 7 for extraction, the gas phase is discharged through the relaxation gas pipeline 8, and the liquid phase refluxes to the pre-distillation tower 1.

[0041] The atmospheric distillation tower 2 is connected to N atmospheric distillation tower reboilers, and the top of the atmospheric distillation tower 2 is connected to M atmospheric distillation tower heat pumps, M = N, and M, N ≥ 2; each atmospheric distillation tower heat pump is respectively connected to an atmospheric distillation tower reboiler, and the N atmospheric distillation tower reboilers are all connected to a refined methanol extraction device; the tower kettle of the atmospheric distillation tower 2 is connected to an atmospheric distillation tower wastewater pipeline 31 for extracting wastewater in the atmospheric distillation tower 2; the refined methanol extraction device includes an atmospheric tower top condenser 13, and the atmospheric tower top condenser 13 is connected to each The atmospheric tower reboiler is connected, the atmospheric tower top condenser 13 is connected to the atmospheric tower top reflux tank 14, the bottom of the atmospheric tower top reflux tank 14 is connected to the refined methanol extraction pipeline 15, the refined methanol extraction pipeline 15 is connected to the atmospheric tower reflux pipeline 16, and the atmospheric tower reflux pipeline 16 is connected to the middle and upper part of the atmospheric distillation tower 2; the refined methanol extraction pipeline 16 is provided with an atmospheric tower refined methanol extraction pump 17, and the refined methanol extraction pipeline 15 is also connected to the refined methanol tank 18, which is used to store the extracted methanol. The refined methanol produced; the energy at the top of the atmospheric distillation tower 2 is pressurized and heated by M atmospheric tower heat pumps through a green electric-driven compressor, and then returned to the N atmospheric tower reboilers in the middle and lower sections of the atmospheric distillation tower. The gas-liquid mixture of the N atmospheric tower reboilers is cooled by the atmospheric tower top condenser 13 and enters the atmospheric tower top reflux tank 14. A part of the liquid phase in the atmospheric tower top reflux tank 14 is extracted as refined methanol, and a part of it is refluxed to the atmospheric distillation tower 2 as an ascending gas. The advantages of using a direct steam compression heat pump are: the required heat carrier (tower top steam) is ready-made; the system is simple, stable and reliable; the compression ratio of the compressor is relatively low, and the required energy consumption is also low; in this embodiment, the low-grade and medium-low-grade waste heat energy at the top of the atmospheric distillation tower 2 is upgraded to a heat pump through a green electric-driven compressor, and the upgrade is converted into high-grade steam. The cost of generating steam is much lower than the cost of generating steam by burning natural gas liquefied gas. The steam can also be used in the position of the device in reverse, and the energy recovery is used on the atmospheric tower reboiler.

[0042] The refined methanol production device produces refined methanol and ensures that part of the liquid phase refluxes to the atmospheric distillation tower 2, the reflux in the middle and lower sections, so as to evenly distribute the gas-liquid load of the whole tower and optimize the heat exchange network of the whole device, and recover the excess heat at the top of the tower to heat the atmospheric tower reboiler; through the setting of M atmospheric tower heat pumps, a cascade heat pump process with different compression ratios is adopted at the top of the atmospheric tower, and the heat at the top of the atmospheric distillation tower is pressurized and heated by M heat pump technologies with different compression ratios. The heat after heating provides heat for N atmospheric tower reboilers in the middle and lower sections of the atmospheric distillation tower, effectively saving external steam; the cascade tower top steam direct compression heat pump distillation can reduce energy consumption, recover and reuse heat, and improve distillation efficiency.

[0043] Embodiment 2:

[0044] In this embodiment, the product quality and fractionation accuracy can be better guaranteed;

[0045] Specifically, the side product of the atmospheric distillation tower 2 is provided with a stripping tower 19, and the fusel alcohol produced from the atmospheric distillation tower 2 by the side line is distilled by the stripping tower 19; the atmospheric distillation tower 2 is connected to the middle and lower parts of the stripping tower 19 through the atmospheric distillation tower side line 20, and refined methanol is produced from the top of the stripping tower 19, and waste water is produced from the bottom of the stripping tower 19; the atmospheric distillation tower side line 20 of the atmospheric distillation tower 2 adds the stripping tower 19, and the atmospheric distillation tower side line 20 of the atmospheric distillation tower 2 produces a gas phase that enters the stripping tower 19, so as to effectively recover the methanol in the fusel alcohol.

[0046] More specifically, the top of the stripping tower 19 is connected to a stripping tower top condenser 21, which is connected to a stripping tower top reflux tank 22, and the bottom of the stripping tower top reflux tank 22 is connected to a stripping tower refined methanol extraction pipeline 23, which is connected to a stripping tower reflux pipeline 24, and a stripping tower refined methanol extraction pump 25 is provided on the stripping tower refined methanol extraction pipeline 23, that is, a part of the liquid phase in the stripping tower top reflux tank 22 is extracted with refined methanol, and a part of it is refluxed to the stripping tower 19; one side of the stripping tower 19 is connected to a mixed The alcohol extraction pipeline 35 is used to extract the mixed alcohol in the stripping tower 19. The bottom of the stripping tower 19 is connected to a wastewater pipe 26 for extracting wastewater. More preferably, the wastewater pipe 26 is connected to a wastewater reflux pipe 34, and the wastewater reflux pipe 34 is connected to the middle and lower part of the atmospheric distillation tower 2. When the wastewater discharged from the bottom of the stripping tower 19 is qualified, it is directly discharged through the wastewater pipe 26. When the wastewater discharged from the bottom of the stripping tower 19 is unqualified, it is refluxed to the atmospheric distillation tower 2 through the wastewater reflux pipe 34 for distillation to ensure that the wastewater discharged from the bottom of the stripping tower 19 is qualified.

[0047] Embodiment three:

[0048] In this embodiment, N=2, and two atmospheric tower reboilers are used, namely, atmospheric tower kettle reboiler 27 and atmospheric tower second reboiler 28, which are connected to atmospheric tower top condenser 13 respectively; M=2, namely, atmospheric tower heat pump 1 29 and atmospheric tower heat pump 2 30, wherein atmospheric tower heat pump 1 29 is connected to atmospheric tower kettle reboiler 27, and atmospheric tower heat pump 2 30 is connected to atmospheric tower second reboiler 28; the top gas of atmospheric distillation tower 2 is divided into two streams, one stream is pressurized and heated by atmospheric tower heat pump 1 29 to provide heat source for atmospheric tower kettle reboiler 27, and the other stream is pressurized and heated by atmospheric tower heat pump 2 30 to provide heat source for atmospheric tower second reboiler 28, that is, the top gas of atmospheric distillation tower 2 is divided into two streams to provide heat source for atmospheric tower reboiler 27, so as to meet the demand of atmospheric tower distillation 2 and effectively reduce the energy consumption of the system.

[0049] Embodiment 4:

[0050] In this embodiment, N=3, which are respectively atmospheric tower kettle reboiler 27, atmospheric tower second reboiler 28, atmospheric tower intermediate reboiler 31, atmospheric tower kettle reboiler 27, atmospheric tower second reboiler 28, atmospheric tower intermediate reboiler 31 are respectively connected to atmospheric tower top condenser 13; M=3, which are atmospheric tower heat pump 1 29, atmospheric tower heat pump 2 30, atmospheric tower heat pump 3 32, wherein atmospheric tower heat pump 1 29 is connected to atmospheric tower kettle reboiler 27, atmospheric tower heat pump 2 30 is connected to atmospheric tower second reboiler 28, atmospheric tower heat pump 3 Three 32 is connected to the intermediate reboiler 31 of the atmospheric pressure tower; the top gas of the atmospheric pressure distillation tower 2 is divided into three streams, one stream is pressurized and heated by the atmospheric pressure tower heat pump one 29 to provide a heat source for the atmospheric pressure tower kettle reboiler 27, another stream is pressurized and heated by the atmospheric pressure tower heat pump two 30 to provide a heat source for the second reboiler 28 of the atmospheric pressure tower, and the last stream is pressurized and heated by the atmospheric pressure tower heat pump three 32 to provide a heat source for the intermediate reboiler 31 of the atmospheric pressure tower; that is, the top gas of the atmospheric pressure distillation tower 2 is graded to provide heat source for the atmospheric pressure tower reboiler, so as to meet the demand of the atmospheric pressure tower distillation 2 and effectively reduce the energy consumption of the system.

[0051] This application has the following beneficial effects:

[0052] 1. Use direct compression heat pump to heat the atmospheric distillation tower top steam for atmospheric tower reboiler cascade, fully couple the atmospheric tower reboiler, recover the tower top waste heat at the lowest cost, save system steam usage, reduce system energy consumption, increase refined alcohol yield, and improve overall economic benefits;

[0053] 2. The traditional methanol distillation process has been changed. The direct compression heat pump energy-saving technology of the atmospheric distillation tower top steam is used to supply heat to the tower steps, which is conducive to the efficient step-by-step recovery of the waste heat energy at the top of the atmospheric distillation tower, facilitating production operations and reducing energy consumption;

[0054] 3. The steam at the top of the atmospheric distillation tower is utilized through direct compression heat pump heat energy, and the atmospheric distillation tower cascade heat exchange can effectively improve the extraction rate of the product, reduce energy consumption, reduce heat loss, and save investment;

[0055] 4. Rationally distribute the load of the atmospheric distillation tower system, integrate heat, realize cascade utilization of energy, optimize the heat exchange process, and reduce energy consumption to meet the requirements of large-scale equipment and diversified methanol production; try to recover the medium and low temperature heat at the top of the atmospheric distillation tower and realize cascade heat combination with the atmospheric tower reboiler, so as to make full use of the low temperature waste heat and reduce heat dissipation loss;

[0056] 5. Combining heat pump technology with traditional distillation process, fully recovering the latent heat of the steam at the top of the pre-distillation tower and the atmospheric distillation tower can reduce the use of cooling water and hot steam in the distillation system. The cascade heat exchange at the top of the atmospheric distillation tower can effectively increase production capacity, improve product purity, reduce product costs, and achieve the purpose of energy saving and consumption reduction;

[0057] 6. It saves saturated steam and circulating water, and reduces the heat discharged into the atmosphere.

[0058] The preferred embodiments of the present application are described in detail above in conjunction with the accompanying drawings; however, the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, a variety of simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the protection scope of the present application.

[0059] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the various possible combinations of this application will not be described separately.

[0060] In addition, the various implementation modes of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed in the present application.

Claims

1. A crude methanol cascade heat pump energy-saving device, comprising a pre-distillation tower (1) and an atmospheric distillation tower (2) connected in sequence, wherein the bottom of the pre-distillation tower (1) is connected to a pre-tower reboiler (4), the top of the pre-distillation tower (1) is connected to a pre-tower heat pump (5), the pre-tower heat pump (5) is connected to the pre-tower reboiler (4), and the pre-tower reboiler (4) is connected to a pre-tower reflux device, It is characterized in that The atmospheric distillation tower (2) is connected to N atmospheric distillation tower reboilers, and the top of the atmospheric distillation tower (2) is connected to M atmospheric distillation tower heat pumps, M=N, and M, N≥2, each atmospheric distillation tower heat pump is respectively connected to an atmospheric distillation tower reboiler, and the N atmospheric distillation tower reboilers are all connected to a refined methanol extraction device.

2. A crude methanol cascade heat pump energy-saving device according to claim 1, It is characterized in that The pre-tower reflux device comprises a pre-tower top cooler (6) connected to a pre-tower reboiler (4), the pre-tower top cooler (6) is connected to a pre-tower reflux tank (7), a purge gas pipeline (8) is arranged at the top of the pre-tower reflux tank (7), an extraction water pipeline (9) is connected to one side of the pre-tower reflux tank (7), and the bottom of the pre-tower reflux tank (7) is connected to the middle and upper part of the pre-distillation tower (1).

3. A crude methanol cascade heat pump energy-saving device according to claim 1, It is characterized in that The refined methanol extraction device comprises an atmospheric tower top condenser (13), the atmospheric tower top condenser (13) is connected to an atmospheric tower top reflux tank (14), the bottom of the atmospheric tower top reflux tank (14) is connected to a refined methanol extraction pipeline (15), the refined methanol extraction pipeline (15) is connected to an atmospheric tower reflux pipeline (16), and the atmospheric tower reflux pipeline (16) is connected to the middle and upper part of the atmospheric distillation tower (2).

4. A crude methanol cascade heat pump energy-saving device according to claim 3, It is characterized in that The refined methanol extraction pipeline (15) is connected to the refined methanol tank (18).

5. A crude methanol cascade heat pump energy-saving device according to claim 1, It is characterized in that A stripping tower (19) is connected to one side of the atmospheric distillation tower (2).

6. A crude methanol cascade heat pump energy-saving device according to claim 5, It is characterized in that The top of the stripping tower (19) is connected to a stripping tower top condenser (21), which is connected to a stripping tower top reflux tank (22), the bottom of the stripping tower top reflux tank (22) is connected to a stripping tower refined methanol extraction pipeline (23), the stripping tower refined methanol extraction pipeline (23) is connected to a stripping tower reflux pipeline (24), and the stripping tower reflux pipeline (24) is connected to the middle and upper part of the stripping tower (19).

7. A crude methanol cascade heat pump energy-saving device according to claim 5, It is characterized in that One side of the stripping tower (19) is connected to a fusel alcohol extraction pipeline (35), and the bottom of the stripping tower (19) is connected to a wastewater pipeline (26).

8. A crude methanol cascade heat pump energy-saving device according to claim 7, It is characterized in that The wastewater pipeline (26) is connected to a wastewater reflux pipeline (34), and the wastewater reflux pipeline (34) is connected to the middle and lower part of the atmospheric distillation tower (2).

9. The crude methanol cascade heat pump energy-saving device according to claim 1, It is characterized in that N=2, the atmospheric tower kettle reboiler includes an atmospheric tower kettle reboiler (27) and an atmospheric tower second reboiler (28); M=2, the atmospheric tower heat pump includes an atmospheric tower heat pump 1 (29) and an atmospheric tower heat pump 2 (30), wherein the atmospheric tower heat pump 1 (29) is connected to the atmospheric tower kettle reboiler (27), and the atmospheric tower heat pump 2 (30) is connected to the atmospheric tower second reboiler (28).

10. The crude methanol cascade heat pump energy-saving device according to claim 1, It is characterized in that N=3, the atmospheric tower kettle reboiler comprises an atmospheric tower kettle reboiler (27), an atmospheric tower second reboiler (28), and an atmospheric tower intermediate reboiler (31); M=3, the atmospheric tower heat pump comprises an atmospheric tower heat pump one (29), an atmospheric tower heat pump two (30), and an atmospheric tower heat pump three (32), wherein the atmospheric tower heat pump one (29) is connected to the atmospheric tower kettle reboiler (27), the atmospheric tower heat pump two (30) is connected to the atmospheric tower second reboiler (28), and the atmospheric tower heat pump three (32) is connected to the atmospheric tower intermediate reboiler (31).

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