Methanol rectification process based on multi-effect thermal coupling and rectification device thereof

Abstract

The invention provides a methanol rectification process based on multi-effect thermal coupling and a rectification device thereof. The device comprises a pre-rectification tower, a negative pressure rectification tower, a pressurization rectification tower, a secondary pressure rectification tower and a normal pressure rectification tower which are connected in sequence, the pre-rectifying tower, the pressurized rectifying tower, the secondary-pressure rectifying tower and the normal-pressure rectifying tower are respectively provided with a pre-tower reboiler, a pressurized tower reboiler, a secondary-pressure tower reboiler and a normal-pressure tower reboiler, the lower part of the negative-pressure rectifying tower is provided with a first negative-pressure tower reboiler and a second negative-pressure tower reboiler, and a gas phase extracted from the top of the secondary-pressure rectifying tower provides heat for the pre-tower reboiler; a gas phase extracted from the top of the pressurized rectifying tower provides heat for a secondary pressure tower reboiler and an atmospheric tower reboiler respectively; a gas phase extracted from the top of the pre-rectifying tower provides heat for a negative pressure tower reboiler I; a gas phase extracted from the top of the normal-pressure rectifying tower provides heat for a negative-pressure tower reboiler II; the energy utilization efficiency in the methanol rectification process can be remarkably improved, the production cost is reduced, and the environmental pollution is reduced.

Description

Technical Field

[0001] The present application relates to the field of chemical technology, and in particular to a methanol distillation process and a distillation device based on multi-effect thermal coupling. Background Art

[0002] Methanol is a widely used basic chemical raw material, which is applied to many fields such as fine chemicals, polymers, pesticides, medicines and energy, and plays an extremely important role in the international chemical market. Crude methanol usually contains light impurities such as dimethyl ether and heavy impurities such as ethanol and water. It is necessary to remove various impurities through the distillation process to obtain refined methanol products that meet the quality requirements. The energy consumption in the methanol distillation process accounts for about 20-30% of the total production energy consumption, which has a great impact on the product cost.

[0003] With the continuous growth of global energy consumption and increasingly severe environmental problems, energy conservation and consumption reduction have become urgent issues to be addressed in industrial production. In the fields of chemical industry, oil refining industry, biochemical industry, environmental protection industry and energy industry, methanol is an important chemical raw material and fuel. The energy consumption in the distillation process of its production is relatively high. Therefore, it is of great significance to improve the energy utilization efficiency of the methanol distillation process.

[0004] Traditional methanol distillation processes usually use single-effect or multi-effect distillation technology, but these technologies have certain limitations in terms of thermal energy utilization; single-effect distillation equipment is simple, but has high energy consumption and low thermal energy utilization efficiency; double-effect distillation is currently used by more than 90% of companies, and its energy consumption is relatively high compared to multi-effect distillation, and it is gradually being eliminated. Although the multi-effect distillation on the market has improved the thermal energy utilization efficiency to a certain extent, there is still room for improvement in energy-saving effects.

[0005] For example, a five-tower four-effect refining device for crude methanol with application number 202320551853.9 discloses a scheme, including a pre-distillation tower, a negative pressure tower, a pressure tower, a normal pressure tower, and a recovery tower connected in sequence, wherein the pre-distillation tower, the negative pressure tower, the pressure tower, the normal pressure tower, and the recovery tower are respectively provided with a pre-distillation tower reboiler, a negative pressure tower reboiler, a pressure tower reboiler, a normal pressure tower reboiler, and a recovery tower reboiler, wherein the refined methanol extracted from the top of the pressure tower exchanges heat with the pre-distillation tower reboiler and the normal pressure tower reboiler, and the refined methanol extracted from the top of the normal pressure tower Methanol is used to exchange heat with the reboiler of the negative pressure tower; the overall structure of the application is simple, and the equipment manufacturing cost is low; the refined methanol extracted from the top of the pressure tower can not only exchange heat with the reboiler of the pre-distillation tower, but also with the reboiler of the atmospheric pressure tower; the refined methanol extracted from the top of the atmospheric pressure tower is used to exchange heat with the reboiler of the negative pressure tower, and the four effects are achieved by the pressure tower itself, and the second and third effects are achieved by thermal coupling at the top of the tower, and the fourth effect is achieved by coupling the top of the atmospheric pressure tower with the negative pressure tower; and compared with the traditional methanol process, this application can reduce the steam consumption per unit to 0.55-0.65.

[0006] In the above patent application, only the heat of refined methanol extracted from the top of the pressure tower and the heat of refined methanol extracted from the top of the atmospheric tower are used. Although the steam consumption per unit is lower than that of the traditional methanol process, there is still room for improvement in energy saving effect.

[0007] In summary, it is necessary to provide a new technical solution to solve the above technical problems. Summary of the invention

[0008] The present application provides a methanol distillation process based on multi-effect thermal coupling, comprising the following steps:

[0009] The crude methanol is preheated by the pre-tower feed preheater;

[0010] The preheated crude methanol enters the pre-distillation tower for distillation. The gas phase extracted from the top of the pre-distillation tower goes to the negative pressure tower reboiler 1 to provide the negative pressure distillation tower with the heat required for distillation.

[0011] The liquid phase extracted from the kettle of the pre-distillation tower enters the negative pressure distillation tower for distillation, and the material extracted from the kettle of the negative pressure distillation tower enters the pressure distillation tower for further distillation;

[0012] The gas phase extracted from the top of the pressure distillation tower is respectively sent to the reboiler of the secondary pressure tower and the reboiler of the atmospheric pressure tower to provide the heat required for distillation for the secondary pressure distillation tower and the atmospheric pressure distillation tower; after the gas phase extracted from the top of the pressure distillation tower exchanges heat with the reboiler of the secondary pressure tower and the reboiler of the atmospheric pressure tower, part of it is refluxed to the pressure distillation tower, and part of it is extracted as refined methanol;

[0013] The liquid phase of the pressure distillation tower kettle goes to the secondary pressure distillation tower, and the gas phase at the top of the secondary pressure distillation tower goes to the pre-tower reboiler to provide the heat required for distillation for the pre-distillation tower; after the gas phase at the top of the secondary pressure distillation tower exchanges heat with the pre-tower reboiler, part of it flows back to the secondary pressure distillation tower, and part of it is produced as refined methanol;

[0014] The material extracted from the bottom of the secondary pressure distillation tower enters the atmospheric pressure distillation tower for distillation, and the gas phase extracted from the top of the atmospheric pressure distillation tower goes to the second reboiler of the negative pressure tower to provide the heat required for distillation for the negative pressure distillation tower; after the atmospheric pressure distillation tower exchanges heat with the second reboiler of the negative pressure tower, part of it flows back to the atmospheric pressure distillation tower, and part of it is extracted as refined methanol; fusel alcohol is extracted from one side of the atmospheric pressure distillation tower, and waste water is extracted from the bottom of the atmospheric pressure distillation tower.

[0015] As a preferred solution, the gas phase extracted from the top of the negative pressure distillation tower is partially refluxed to the negative pressure distillation tower after condensation, and the rest is extracted as refined methanol.

[0016] As a preferred solution, the materials in the kettle of the negative pressure distillation tower are preheated by the first-stage feed preheater and the second-stage feed preheater of the pressure tower and then enter the pressure distillation tower.

[0017] As a preferred scheme, the liquid phase extracted from the bottom of the pre-distillation tower enters the negative pressure distillation tower and the second negative pressure distillation tower for distillation respectively, and the gas phase extracted from the top of the negative pressure distillation tower goes to the reboiler of the second negative pressure distillation tower to provide the heat required for distillation for the second negative pressure distillation tower. After the gas phase extracted from the top of the negative pressure distillation tower exchanges heat with the reboiler of the second negative pressure distillation tower, part of it flows back to the negative pressure distillation tower, and part of it is extracted as refined methanol; the gas phase extracted from the top of the second negative pressure distillation tower is condensed and part of it flows back to the second negative pressure distillation tower, and part of it is extracted as refined methanol. The materials extracted from the bottoms of the negative pressure distillation tower and the second negative pressure distillation tower enter the pressurized distillation tower for further distillation.

[0018] As a preferred solution, the materials in the bottom of the negative pressure distillation tower and the bottom of the second negative pressure distillation tower are preheated by the first feed preheater of the pressure tower and the second feed preheater of the pressure tower before entering the pressure distillation tower.

[0019] As a preferred solution, the liquid phase of the kettle of the pressure distillation tower goes to the first-stage feed preheater of the pressure tower to provide heat for the first-stage feed preheater of the pressure tower.

[0020] As a preferred solution, the gas phase extracted from the top of the pre-distillation tower is heat exchanged with the negative pressure tower reboiler, and then cooled by the pre-tower top condenser and enters the extraction reflux tank. The non-condensable gas produced after extraction in the extraction reflux tank is discharged, and the liquid phase produced after extraction is refluxed to the pre-distillation tower.

[0021] As a preferred solution, steam is used to heat the pressurized tower reboiler provided in the kettle of the pressurized distillation tower. The heated steam passes through the pressurized tower secondary feed preheater, heats the pressurized tower secondary feed preheater, and is then produced as condensate.

[0022] The present application provides a methanol distillation device based on multi-effect thermal coupling, comprising a pre-distillation tower, a negative pressure distillation tower, a pressurized distillation tower, a secondary pressure distillation tower, and an atmospheric pressure distillation tower connected in sequence, wherein the pre-distillation tower, the pressurized distillation tower, the secondary pressure distillation tower, and the atmospheric pressure distillation tower are respectively provided with a pre-tower reboiler, a pressurized tower reboiler, a secondary pressure tower reboiler, and an atmospheric pressure tower reboiler, and the lower part of the negative pressure distillation tower is provided with a negative pressure tower reboiler 1 and a negative pressure tower reboiler 2, wherein the gas phase extracted from the top of the secondary pressure distillation tower provides heat to the pre-tower reboiler; the gas phase extracted from the top of the pressurized distillation tower provides heat to the secondary pressure tower reboiler and the atmospheric pressure tower reboiler respectively; the gas phase extracted from the top of the pre-distillation tower provides heat to the negative pressure tower reboiler 1; the gas phase extracted from the top of the atmospheric pressure distillation tower provides heat to the negative pressure tower reboiler 2.

[0023] As a preferred solution, the output end of the negative pressure tower reboiler 1 is connected to a pre-tower reflux device.

[0024] As a preferred embodiment, the pre-tower reflux device includes an extraction reflux tank, an extraction water pipeline is arranged on one side of the extraction reflux tank, a purge gas pipeline is arranged on the top of the extraction reflux tank, and the bottom of the extraction reflux tank is connected to the upper part of the pre-distillation tower through the pre-tower reflux pipeline.

[0025] As a preferred solution, a negative pressure tower reflux device is provided at the top of the negative pressure distillation tower.

[0026] As a preferred solution, the output end of the secondary pressure tower reboiler and the output end of the atmospheric pressure tower reboiler are respectively connected to the pressure tower reflux tank, the bottom of the pressure tower reflux tank is connected to the upper part of the pressure distillation tower through the pressure tower reflux pipeline, and the pressure tower reflux pipeline is connected to the pressure tower refined methanol extraction pipeline.

[0027] As a preferred solution, the output end of the pre-tower reboiler is connected to the secondary pressure tower reflux device.

[0028] As a preferred embodiment, the secondary pressure tower reflux device includes a secondary pressure tower reflux tank, the bottom of the secondary pressure tower reflux tank is connected to the upper part of the secondary pressure distillation tower through a secondary pressure tower reflux pipeline, and the secondary pressure tower reflux pipeline is connected to the secondary pressure tower refined methanol production pipeline.

[0029] As a preferred solution, the output end of the negative pressure tower reboiler 2 is connected to the atmospheric pressure tower reflux device.

[0030] As a preferred embodiment, the atmospheric tower reflux device includes an atmospheric tower reflux tank, the bottom of which is connected to the upper part of the atmospheric distillation tower through an atmospheric tower reflux pipeline, and the atmospheric tower reflux pipeline is connected to the atmospheric tower refined methanol production pipeline.

[0031] As a preferred solution, the pre-distillation tower is connected to the negative pressure distillation tower and the negative pressure distillation tower 2 respectively, the negative pressure distillation tower and the negative pressure distillation tower 2 are connected to the pressurized distillation tower, and a negative pressure tower 2 reboiler is provided on the negative pressure distillation tower 2, and the gas extracted from the top of the negative pressure distillation tower provides heat for the negative pressure tower 2 reboiler.

[0032] As a preferred solution, the output end of the second reboiler of the negative pressure tower is connected to the negative pressure tower reflux device.

[0033] As a preferred embodiment, the negative pressure tower reflux device includes a negative pressure tower reflux tank, the bottom of the negative pressure tower reflux tank is connected to the upper part of the negative pressure distillation tower through a negative pressure tower reflux pipeline, and the negative pressure tower reflux pipeline is connected to the negative pressure tower refined methanol production pipeline; the upper part of the negative pressure tower reflux tank is connected to the negative pressure tower top secondary condenser through a top pipeline, and the output ends of the negative pressure tower top secondary condenser are respectively connected to a non-condensable steam production pipeline and a condensate pipeline, the condensate pipeline is connected to the negative pressure tower reflux tank, and the non-condensable steam production pipeline is provided with a vacuum pump.

[0034] As a preferred scheme, a negative pressure tower two reflux device is provided at the top of the negative pressure distillation tower two, and the negative pressure tower two reflux device includes a negative pressure tower two reflux tank, and the bottom of the negative pressure tower two reflux tank is connected to the upper part of the negative pressure distillation tower two through a negative pressure tower two reflux pipeline, and the negative pressure tower two reflux pipeline is connected to the negative pressure tower two refined methanol production pipeline; the upper part of the negative pressure tower two reflux tank is connected to the negative pressure tower two secondary condenser through a top pipeline two, and the output ends of the negative pressure tower two secondary condensers are respectively connected to a non-condensable steam production pipeline two and a condensate pipeline two, and the condensate pipeline two is connected to the negative pressure tower two reflux tank, and a vacuum pump two is provided on the non-condensable steam production pipeline two.

[0035] As a preferred solution, a feed pipeline is provided on one side of the pre-distillation tower, and a pre-tower feed preheater is provided on the feed pipeline.

[0036] As a preferred solution, the bottom of the negative pressure distillation tower is connected to the pressurized distillation tower through a negative pressure tower kettle extraction pipeline, and the negative pressure tower kettle extraction pipeline is sequentially provided with a first-level feed preheater for the pressurized tower and a second-level feed preheater for the pressurized tower.

[0037] As a preferred solution, the input end of the pressurized tower reboiler is connected to the steam pipeline, and the output end of the pressurized tower reboiler is connected to the condensate pipeline.

[0038] As a preferred solution, the condenser pipeline passes through the secondary feed preheater and the feed preheater of the pressurized tower in sequence.

[0039] In the present application, the top heat of the pre-distillation tower, the pressure distillation tower, the secondary pressure distillation tower and the atmospheric pressure distillation tower is fully utilized, and the unit steam consumption is significantly reduced, and the consumption is reduced to 0.5-0.55 tons of steam / ton of refined alcohol, which greatly reduces the energy consumption. Moreover, through the effective recovery and utilization of heat, the thermal efficiency of the entire distillation system is improved, the operating cost of the system is guaranteed to be reduced, the economic benefits of the enterprise are improved, and the emission of carbon dioxide and other pollutants is reduced, which is in line with the green and environmentally friendly production concept; preferably, the heat at the top of the negative pressure distillation tower is also utilized to further reduce the unit steam consumption to 0.4-0.45 tons of steam / ton of refined alcohol, and the energy-saving effect is more significant; the overall thermal efficiency of the system is further improved, the operating cost of the system is further reduced, and the environmental impact is further reduced, which is conducive to achieving sustainable development and environmental protection.

[0040] The present invention can significantly improve the energy efficiency of the methanol distillation process, reduce production costs, and reduce environmental pollution, thus having significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a structural schematic diagram of the first embodiment of the present application;

[0042] Figure 2It is a structural diagram of Embodiment 2 of the present application;

[0043] 1. Pre-distillation tower; 2. Negative pressure distillation tower; 3. Pressurized distillation tower; 4. Secondary pressure distillation tower; 5. Atmospheric pressure distillation tower; 6. Feed pipeline; 7. Pre-tower feed preheater; 8. Pre-tower kettle extraction pipeline; 9. Negative pressure tower feed pump; 10. Negative pressure tower kettle extraction pipeline; 11. Pressurized tower feed pump; 12. Pressurized tower primary feed preheater; 13. Pressurized tower secondary feed preheater; 14. Pressurized tower kettle extraction pipeline; 15. Secondary pressure tower extraction pipeline; 16. Atmospheric pressure tower feed pump; 17. Fusel alcohol extraction pipeline; 18. Wastewater extraction pipeline; 19. Pre-tower reboiler; 20. Pressurized tower reboiler; 21. Secondary pressure tower reboiler; 22. Atmospheric pressure tower reboiler; 23. Negative pressure tower reboiler 1; 24. Negative pressure tower reboiler 2; 25. Production pipeline at the top of the secondary pressure tower; 26. Production pipeline at the top of the pressure tower; 27. Production pipeline at the top of the pressure tower 1; 28. Production pipeline at the top of the pre-tower; 29. ​​Production pipeline at the top of the atmospheric pressure tower; 30. Steam pipeline; 31. Condensate pipeline; 32. Extraction reflux tank; 33. Output pipeline of the negative pressure tower reboiler 1; 34. Condenser at the top of the pre-tower; 35. Extraction water pipeline; 36. Purge gas pipeline; 37. Reflux pipeline at the pre-tower; 38. Reflux pump at the pre-tower; 39. Reflux tank at the negative pressure tower; 40. Production pipeline at the top of the negative pressure tower; 41. First-level condenser at the top of the negative pressure tower; 42. Reflux pipeline at the negative pressure tower; 43. Reflux production pump at the negative pressure tower; 44. Production pipeline for refined methanol at the negative pressure tower; 45. Cooler at the top of the negative pressure tower; 46. Refined methanol Methanol tank; 47, top pipeline; 48, negative pressure tower top secondary condenser; 49, non-condensable steam extraction pipeline; 50, condensate pipeline; 51, vacuum pump; 52, secondary pressure tower reboiler output pipeline; 53, pressure tower reflux tank; 54, atmospheric pressure tower reboiler output pipeline; 55, pressure tower reflux pipeline; 56, pressure tower reflux extraction pump; 57, pressure tower refined methanol extraction pipeline; 58, pressure tower top cooler; 59, pre-tower reboiler output pipeline; 60, secondary pressure tower reflux tank; 61, secondary pressure tower reflux pipeline; 62, secondary pressure tower reflux extraction pump; 63, secondary pressure tower refined methanol extraction pipeline; 64, negative pressure tower reboiler second output pipeline; 65, atmospheric pressure tower reflux tank; 66, atmospheric pressure tower reflux pipeline; 67, atmospheric pressure tower reflux extraction Output pump; 68. Atmospheric pressure tower refined methanol production pipeline; 69. Atmospheric pressure tower top cooler; 70. Negative pressure distillation tower II; 71. Pre-tower kettle production pipeline I; 72. Negative pressure tower II kettle production pipeline; 73. Negative pressure tower II reboiler; 74. Negative pressure tower II reboiler output pipeline; 75. Negative pressure tower II reflux tank; 76. Negative pressure tower II top production pipeline; 77. Negative pressure tower II first-stage condenser; 78. Negative pressure tower II reflux pipeline; 79. Negative pressure tower II reflux production pump; 80. Negative pressure tower II refined methanol production pipeline; 81. Top pipeline II; 82. Negative pressure tower II second-stage condenser; 83. Non-condensable steam production pipeline II; 84. Condensate pipeline II; 85. Wastewater production pipeline II; 86. Negative pressure tower II kettle pump; 87. Vacuum pump II. DETAILED DESCRIPTION

[0044] The following is combined with Figure 1 —2 Detailed description of the specific implementation of the present invention. It should be noted that the specific implementation described herein is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0045] Embodiment 1:

[0046] This embodiment provides a methanol distillation process based on multi-effect thermal coupling, characterized in that it includes the following steps:

[0047] The crude methanol is preheated by the pre-tower feed preheater 7;

[0048] The preheated crude methanol enters the pre-distillation tower 1 for distillation, and the gas phase extracted from the top of the pre-distillation tower 1 goes to the negative pressure tower reboiler 23 to provide the heat required for distillation for the negative pressure distillation tower 2, and then enters the extraction reflux tank 32 after being cooled by the pre-tower top condenser 34, and the non-condensable gas produced after extraction in the extraction reflux tank 32 is discharged, and the liquid phase produced after extraction is refluxed to the pre-distillation tower 1; the pre-distillation tower 1 provides the heat required for distillation of the pre-distillation tower 1 in the form of indirect heating by the pre-tower reboiler 19, wherein the heat source of the pre-tower reboiler 19 is the gas phase extracted from the top of the secondary pressure distillation tower 4;

[0049] The liquid phase extracted from the bottom of the pre-distillation tower 1 enters the negative pressure distillation tower 2 for distillation. The gas phase extracted from the top of the negative pressure distillation tower 2 is condensed and partially refluxed to the negative pressure distillation tower 2, and partially extracted as extracted refined methanol. Specifically: the gas phase extracted from the top of the negative pressure distillation tower 2 is condensed by the negative pressure tower top primary condenser 41, and then enters the negative pressure tower reflux tank 39. The refined methanol in the negative pressure tower reflux tank 39 is divided into two streams, one of which is refluxed to the negative pressure distillation tower 2, and the other is extracted as extracted refined methanol; the gas phase in the negative pressure tower reflux tank 39 is condensed by the negative pressure tower top secondary condenser 48, and the liquid phase returns to the negative pressure tower reflux tank 39, and the gas phase is passed through the negative pressure tower top secondary condenser 48. The vacuum distillation tower 2 is extracted through the non-condensable steam extraction pipeline 49; the vacuum distillation tower 2 provides the heat required for distillation of the vacuum distillation tower 2 in the form of indirect heating by the vacuum tower reboiler 1 23 and the vacuum tower reboiler 2 24, wherein the heat source of the vacuum tower reboiler 1 23 is the gas phase extracted from the top of the pre-distillation tower 1, and the heat source of the vacuum tower reboiler 2 24 is the gas phase extracted from the top of the atmospheric distillation tower 5; the material extracted from the bottom of the vacuum distillation tower 2 enters the pressurized distillation tower 3 for further distillation; preferably, the material in the bottom of the vacuum distillation tower 2 is preheated by the first-level feed preheater 12 of the pressurized tower and the second-level feed preheater 13 of the pressurized tower before entering the pressurized distillation tower 3;

[0050] The gas phase extracted from the top of the pressure distillation tower 3 is respectively sent to the secondary pressure tower reboiler 21 and the atmospheric pressure tower reboiler 22 to provide the heat required for distillation for the secondary pressure distillation tower 4 and the atmospheric pressure distillation tower 5; the gas phase extracted from the top of the pressure distillation tower 3 is heat-exchanged with the secondary pressure tower reboiler 4 and the atmospheric pressure tower reboiler 5, and part of it is refluxed to the pressure distillation tower 3, and part of it is extracted as extracted refined methanol; specifically: the gas phase extracted from the top of the pressure distillation tower 3 is heat-exchanged with the secondary pressure tower reboiler 21 and the atmospheric pressure tower reboiler 22, and then enters the pressure tower reflux tank 53, and the refined methanol in the pressure tower reflux tank 53 is divided into two streams, one of which is refluxed to the pressure distillation tower 3, and the other is extracted as extracted refined methanol. It is produced as refined methanol; the liquid phase of the bottom of the pressurized distillation tower 3 goes to the secondary pressure distillation tower 4, preferably, the liquid phase of the bottom of the pressurized distillation tower 3 goes to the first-level feed preheater 12 of the pressurized tower, which provides heat for the first-level feed preheater 12 of the pressurized tower, and the material after heat exchange with the first-level feed preheater 12 of the pressurized tower goes to the secondary pressure distillation tower 4; the pressurized distillation tower 3 provides the heat required for distillation in the form of indirect heating by the pressurized tower reboiler 20, and the heat source of the pressurized tower reboiler 20 is steam. Preferably, the heated steam passes through the second-level feed preheater 13 of the pressurized tower, and is produced as condensate after providing heat for the second-level feed preheater 13 of the pressurized tower.

[0051] The gas phase at the top of the secondary pressure distillation tower 4 goes to the pre-tower reboiler 19 to provide the heat required for distillation for the pre-distillation tower 1; after the gas phase at the top of the secondary pressure distillation tower 4 exchanges heat with the pre-tower reboiler 19, part of it flows back to the secondary pressure distillation tower 4, and part of it is produced as refined methanol; specifically, the gas phase at the top of the secondary pressure distillation tower 4 exchanges heat with the pre-tower reboiler 19 and enters the secondary pressure tower reflux tank 60, and the refined methanol in the secondary pressure tower reflux tank 60 is divided into two streams, one of which flows back to the secondary pressure distillation tower 4, and the other is produced as refined methanol; the secondary pressure distillation tower 4 provides the heat required for distillation in the form of indirect heating by the secondary pressure tower reboiler 21, and the heat source of the secondary pressure tower reboiler 21 is the gas phase at the top of the pressurized distillation tower 3;

[0052] The material extracted from the bottom of the secondary pressure distillation tower 4 enters the atmospheric pressure distillation tower 5 for distillation, and the gas phase extracted from the top of the atmospheric pressure distillation tower 5 goes to the negative pressure tower reboiler 24 to provide the heat required for distillation for the negative pressure distillation tower 2; the gas phase extracted from the top of the atmospheric pressure distillation tower 5 exchanges heat with the negative pressure tower reboiler 24, and part of it flows back to the atmospheric pressure distillation tower 5, and part of it is extracted as refined methanol; specifically: the gas phase extracted from the top of the atmospheric pressure distillation tower 5 exchanges heat with the negative pressure tower reboiler 24 and enters the atmospheric pressure tower reflux tank 65, and the refined methanol in the atmospheric pressure tower reflux tank 65 is divided into two streams, one of which flows back to the atmospheric pressure distillation tower 5, and the other is extracted as refined methanol; one side of the atmospheric pressure distillation tower 5 extracts fusel alcohol, and the bottom of the atmospheric pressure distillation tower 5 extracts waste water; the atmospheric pressure distillation tower 5 provides the heat required for distillation in the form of indirect heating by the atmospheric pressure tower reboiler 22, and the heat source of the atmospheric pressure tower reboiler 22 is the gas phase at the top of the atmospheric pressure distillation tower 5.

[0053] In this embodiment, the top heat of the pre-distillation tower 1, the pressure distillation tower 3, the secondary pressure distillation tower 4, and the atmospheric distillation tower 5 is fully utilized, and the steam consumption per unit is significantly reduced from the consumption of the traditional process to 0.5-0.55 tons of steam / ton of refined alcohol, which greatly reduces energy consumption. In addition, through the effective recovery and utilization of heat, the thermal efficiency of the entire distillation system is improved, the system operation cost is reduced, the economic benefits of the enterprise are improved, and the emission of carbon dioxide and other pollutants is reduced, which is in line with the green and environmentally friendly production concept.

[0054] Embodiment 2

[0055] The difference between this embodiment and the first embodiment is that:

[0056] The liquid phase extracted from the bottom of the pre-distillation tower 1 enters the negative pressure distillation tower 2 and the negative pressure distillation tower 2 70 for distillation respectively, and the gas phase extracted from the top of the negative pressure distillation tower 2 goes to the negative pressure tower 2 reboiler 73 to provide the heat required for distillation for the negative pressure distillation tower 2 70. After the gas phase extracted from the top of the negative pressure distillation tower 2 exchanges heat with the negative pressure tower 2 reboiler 73, part of it refluxes to the negative pressure distillation tower 2, and part of it is extracted as refined methanol; specifically: the gas phase extracted from the top of the negative pressure distillation tower 2 exchanges heat with the negative pressure tower 2 reboiler 73 and enters the negative pressure tower reflux tank 39, refer to Example 1 for details, and no specific details are given here;

[0057] The gas phase extracted from the top of the negative pressure distillation tower 2 70 is partially refluxed to the negative pressure distillation tower 2 70 after condensation, and partially extracted as refined methanol. Specifically, the gas phase extracted from the top of the negative pressure distillation tower 2 70 is condensed by the first-level condenser 77 of the negative pressure tower 2 and enters the reflux tank 75 of the negative pressure tower 2. The refined methanol in the reflux tank 75 of the negative pressure tower 2 is divided into two streams, one of which is refluxed to the negative pressure distillation tower 2 70, and the other is extracted as refined methanol; the gas phase in the reflux tank 75 of the negative pressure tower 2 is condensed by the second-level condenser 82 of the negative pressure tower 2, and the liquid phase returns to the reflux tank of the negative pressure tower 2 75, the gas phase is produced through the non-condensable steam production pipeline 2 83; the negative pressure distillation tower 2 70 provides the heat required for distillation in the form of indirect heating through the negative pressure tower 2 reboiler 73, and the heat source of the negative pressure tower 2 reboiler 73 is the gas phase at the top of the negative pressure distillation tower 2; the materials produced from the bottom of the negative pressure distillation tower 2 and the negative pressure distillation tower 2 70 enter the pressurized distillation tower 3 for further distillation, and the bottom material of the negative pressure distillation tower 2 and the bottom material of the negative pressure distillation tower 2 70 are preheated by the first-level feed preheater 12 of the pressurized tower and the second-level feed preheater 13 of the pressurized tower before entering the pressurized distillation tower.

[0058] In addition, waste water is extracted from the bottom of the secondary pressure distillation tower 4.

[0059] In this embodiment, compared with the first embodiment, a negative pressure distillation tower 2 70 is further provided, and the heat at the top of the negative pressure distillation tower 2 is also used to heat the negative pressure tower 2 reboiler 73 to meet the heat required for the distillation of the negative pressure distillation tower 2 70, so that the steam unit consumption is further reduced to 0.4-0.45 tons of steam / ton of refined alcohol, and the energy saving effect is more significant; by increasing the utilization of the heat at the top of the negative pressure distillation tower 2, a deeper heat recovery is achieved, and the overall thermal efficiency of the system is improved; due to more efficient thermal coupling, the operating cost of the system is further reduced, and the economic benefit is more obvious; the environmental impact is further reduced, which is conducive to achieving sustainable development and environmental protection.

[0060] Embodiment three:

[0061] like Figure 1 As shown, the present application provides a methanol distillation device based on multi-effect thermal coupling, comprising a pre-distillation tower 1, a negative pressure distillation tower 2, a pressurized distillation tower 3, a secondary pressure distillation tower 4, and an atmospheric distillation tower 5 connected in sequence. More specifically, a feed pipeline 6 is provided on one side of the pre-distillation tower 1, and a pre-tower feed preheater 7 is provided on the feed pipeline 6. The crude methanol enters the pre-distillation tower 1 after being preheated by the pre-tower feed preheater 7; the bottom of the pre-distillation tower 1 is connected to the negative pressure distillation tower 2 through a pre-tower reactor extraction pipeline 8, and a negative pressure tower feed pump 9 is provided on the pre-tower reactor extraction pipeline 8; the bottom of the negative pressure distillation tower 2 is connected to the pressurized distillation tower 3 through a negative pressure tower reactor extraction pipeline 10, and the negative pressure tower reactor extraction pipeline 10 is sequentially provided with a pressurized tower feed pump 9. The material at the bottom of the negative pressure distillation tower 2 is preheated in sequence by the negative pressure distillation tower first-level feed preheater 12 and the negative pressure distillation tower second-level feed preheater 13, and then enters the negative pressure distillation tower 3; the bottom of the negative pressure distillation tower 3 is connected with the secondary pressure distillation tower 4 through the negative pressure distillation tower kettle extraction pipeline 14, and the negative pressure distillation tower kettle extraction pipeline 14 passes through the negative pressure distillation tower first-level feed preheater 12; the secondary pressure distillation tower 4 is connected with the atmospheric distillation tower 5 through the secondary pressure tower extraction pipeline 15, and the atmospheric pressure tower feed pump 16 is arranged on the secondary pressure tower extraction pipeline 15; a fusel alcohol extraction pipeline 17 is arranged on one side of the atmospheric distillation tower 5, and a wastewater extraction pipeline 18 is arranged at the bottom of the atmospheric distillation tower 5 for extracting wastewater that meets the standards.

[0062] The pre-distillation tower 1, the pressure distillation tower 3, the secondary pressure distillation tower 4, and the atmospheric pressure distillation tower 5 are respectively provided with a pre-tower reboiler 19, a pressure tower reboiler 20, a secondary pressure tower reboiler 21, and an atmospheric pressure tower reboiler 22. The lower part of the negative pressure distillation tower 2 is provided with a negative pressure tower reboiler 1 23 and a negative pressure tower reboiler 2 24. The top of the secondary pressure distillation tower 4 is connected to the input end of the pre-tower reboiler 19 through a secondary pressure tower top extraction pipeline 25. The top of the secondary pressure distillation tower 4 is extracted The gaseous refined alcohol is used as a heat source to provide heat to the pre-tower reboiler 19; the top of the pressure distillation tower 3 is connected to the atmospheric tower reboiler 22 and the secondary pressure tower reboiler 21 through the pressure tower top extraction pipeline 26 and the pressure tower top extraction pipeline 27, respectively, and the gaseous refined alcohol extracted from the top of the pressure distillation tower 3 is used as a heat source to provide heat to the atmospheric tower reboiler 22 and the secondary pressure tower reboiler 21, respectively; the top of the pre-distillation tower 1 is connected to the negative pressure tower reboiler through the pre-tower top extraction pipeline 28. The top of the atmospheric distillation tower 5 is connected to the negative pressure tower reboiler 24 through the atmospheric tower top extraction pipeline 29, and the gaseous phase refined alcohol extracted from the top of the atmospheric distillation tower 5 is used as a heat source to provide heat to the negative pressure tower reboiler 24; the pressure tower reboiler 20 is heated by 0.5MpaG steam. Specifically, the input end of the pressure tower reboiler 20 is connected to the negative pressure tower reboiler 24 through the atmospheric tower top extraction pipeline 29. The gaseous phase refined alcohol extracted from the top of the atmospheric distillation tower 5 is used as a heat source to provide heat to the negative pressure tower reboiler 24; the pressure tower reboiler 20 is heated by 0.5MpaG steam. Specifically, the input end of the pressure tower reboiler 20 is connected to the negative pressure tower reboiler 24 through the atmospheric tower top extraction pipeline 29. The inlet end is connected to the steam pipeline 30, and the output end of the pressure tower reboiler 20 is connected to the condensate pipeline 31. Preferably, the condensate pipeline 31 passes through the pressure tower secondary feed preheater 13 and the pre-tower feed preheater 7 in sequence; the pressure tower reboiler 20 is heated by 0.5MpaG steam, and the gaseous refined alcohol at the top of the pressure distillation tower 3 is used as a heat source to provide heat for the secondary pressure tower reboiler 21 and the atmospheric pressure tower reboiler 22, thereby further optimizing the utilization of thermal energy.

[0063] The output end of the negative pressure tower reboiler 23 is connected to a pre-tower reflux device, and the pre-tower reflux device includes an extraction reflux tank 32, and the extraction reflux tank 32 is connected to the output end of the negative pressure tower reboiler 23 through a negative pressure tower reboiler output pipeline 33, and a pre-tower top condenser 34 is arranged on the negative pressure tower reboiler output pipeline 33, and an extraction water pipeline 35 is arranged on one side of the extraction reflux tank 32, and a venting gas pipeline 36 is arranged on the top of the extraction reflux tank 32, and the bottom of the extraction reflux tank 32 is connected to the upper part of the pre-distillation tower 1 through a pre-tower reflux pipeline 37. Then, a pre-tower reflux pump 38 is arranged on the pre-tower reflux line 37; the gaseous refined methanol extracted from the top of the pre-distillation tower 1 is used as a heat source to provide heat to the negative pressure tower reboiler 23, and the material after heat exchange and cooling with the negative pressure tower reboiler 23 is further cooled by the pre-tower top condenser 34 and then enters the extraction reflux tank 32, and extraction water is introduced into the extraction reflux tank 32, and the gas phase in the extraction reflux tank 32 is extracted through the purge gas pipeline 36, and the liquid phase in the extraction reflux tank 32 is refluxed to the pre-distillation tower 1 through the pre-tower reflux line 37, so as to improve the distillation accuracy of refined methanol.

[0064] A negative pressure tower reflux device is provided at the top of the negative pressure distillation tower 2, and the negative pressure tower reflux device includes a negative pressure tower reflux tank 39, which is connected to the top of the negative pressure distillation tower 2 through a negative pressure tower top extraction pipeline 40, and a negative pressure tower top primary condenser 41 is provided on the negative pressure tower top extraction pipeline 40, and the bottom of the negative pressure tower reflux tank 39 is connected to the upper part of the negative pressure distillation tower 2 through a negative pressure tower reflux pipeline 42, and a negative pressure tower reflux extraction pump 43 is provided on the negative pressure tower reflux pipeline 42, and the negative pressure tower reflux pipeline 42 is connected to a negative pressure tower refined methanol extraction pipeline 44, and a negative pressure tower top cooler 45 is provided on the negative pressure tower refined methanol extraction pipeline 44; the negative pressure tower refined methanol extraction pipeline 44 is used to extract refined methanol, and the negative pressure tower refined methanol extraction pipeline 44 can be connected to a refined methanol tank 46, and the refined methanol tank 46 is used to store the extracted the refined methanol produced; the upper part of the negative pressure tower reflux tank 39 is connected to the negative pressure tower top secondary condenser 48 through the top pipeline 47, and the output ends of the negative pressure tower top secondary condenser 48 are respectively connected to the non-condensable steam extraction pipeline 49 and the condensate pipeline 50, the condensate pipeline 50 is connected to the negative pressure tower reflux tank 39, and the non-condensable steam extraction pipeline 49 is provided with a vacuum pump 51; the gas phase extracted from the top of the negative pressure distillation tower 2 enters the negative pressure tower reflux tank 39 after being condensed by the negative pressure tower top primary condenser 41, and the liquid phase in the negative pressure tower reflux tank 39 is partially refluxed to the negative pressure distillation tower 2, and part is extracted as refined methanol; the gas phase in the negative pressure tower reflux tank 39 is condensed by the negative pressure tower top secondary condenser 48, and the liquid phase returns to the negative pressure tower reflux tank 39, and the gas phase is extracted through the non-condensable steam extraction pipeline 49, and the extracted non-condensable steam enters the exhaust gas treatment system for treatment.

[0065] The output end of the secondary pressure tower reboiler 21 is connected to the pressure tower reflux tank 53 through the secondary pressure tower reboiler output pipeline 52, and the output end of the atmospheric pressure tower reboiler 22 is connected to the pressure tower reflux tank 53 through the atmospheric pressure tower reboiler output pipeline 54. The bottom of the pressure tower reflux tank 53 is connected to the upper part of the pressurized distillation tower 3 through the pressure tower reflux pipeline 55. The pressure tower reflux pipeline 55 is provided with a pressure tower reflux extraction pump 56. The pressure tower reflux pipeline 55 is connected to the pressure tower refined methanol extraction pipeline 57. The pressure tower refined methanol extraction A pressurized tower top cooler 58 is provided on the pipeline 57, and the pressurized tower refined methanol production pipeline 57 can be connected to the refined methanol tank 46, and the refined methanol tank 46 is used to store the produced refined methanol; the gaseous refined alcohol produced from the top of the pressurized distillation tower 3 is used as a heat source to provide heat to the secondary pressure tower reboiler 21 and the atmospheric pressure tower reboiler 22 respectively, and the liquid phase after heat exchange and cooling with the secondary pressure tower reboiler 21 and the atmospheric pressure tower reboiler 22 enters the pressurized tower reflux tank 53, and part of the liquid phase in the pressurized tower reflux tank 53 is refluxed to the pressurized distillation tower 3, and part is produced as refined methanol.

[0066] The output end of the pre-tower reboiler 19 is connected to the secondary pressure tower reflux device through the pre-tower reboiler output pipeline 59; the secondary pressure tower reflux device includes a secondary pressure tower reflux tank 60, which is connected to the output end of the pre-tower reboiler 19 through the pre-tower reboiler output pipeline 59, and the bottom of the secondary pressure tower reflux tank 60 is connected to the upper part of the secondary pressure distillation tower 4 through the secondary pressure tower reflux pipeline 61, and the secondary pressure tower reflux pipeline 61 is provided with a secondary pressure tower reflux extraction Pump 62, the secondary pressure tower reflux pipeline 61 is connected to the secondary pressure tower refined methanol production pipeline 63; the secondary pressure tower refined methanol production pipeline 63 can be connected to the refined methanol tank 46; the gaseous refined alcohol produced from the top of the secondary pressure distillation tower 4 is used as a heat source to provide heat to the pre-tower reboiler 19, and the liquid phase after heat exchange and cooling in the pre-tower reboiler 19 enters the secondary pressure tower reflux tank 60, and part of the liquid phase in the secondary pressure tower reflux tank 60 is refluxed to the secondary pressure distillation tower 4, and part is produced as refined methanol.

[0067] The output end of the negative pressure tower reboiler 24 is connected to the atmospheric pressure tower reflux device through the negative pressure tower reboiler 2 output pipeline 64; the atmospheric pressure tower reflux device includes an atmospheric pressure tower reflux tank 65, which is connected to the output end of the negative pressure tower reboiler 24 through the negative pressure tower reboiler 2 output pipeline 64, and the bottom of the atmospheric pressure tower reflux tank 65 is connected to the upper part of the atmospheric distillation tower 5 through the atmospheric pressure tower reflux pipeline 66, and the atmospheric pressure tower reflux pipeline 66 is provided with an atmospheric pressure tower reflux extraction pump 67, and the atmospheric pressure tower reflux pipeline 66 is connected to the atmospheric pressure tower refined methanol extraction pipeline 68, and the atmospheric pressure tower refined methanol extraction pipeline 68 is provided with an atmospheric pressure tower top cooler 69, the atmospheric tower refined methanol extraction pipeline 68 can be connected to the refined methanol tank 46; the above-mentioned secondary pressure tower refined methanol extraction pipeline 63 can be directly connected to the refined methanol tank 46, or the secondary pressure tower refined methanol extraction pipeline 63 can be connected to the atmospheric pressure tower refined methanol extraction pipeline 68, the refined methanol extracted from the secondary pressure distillation tower 4 and the atmospheric pressure distillation tower 5 are mixed and then enter the refined methanol tank 46; the gaseous refined alcohol extracted from the top of the atmospheric pressure distillation tower 5 is used as a heat source to provide heat to the negative pressure tower reboiler 24, and the liquid phase after heat exchange and cooling with the negative pressure tower reboiler 24 enters the atmospheric pressure tower reflux tank 65, and part of the liquid phase in the atmospheric pressure tower reflux tank 65 is refluxed to the atmospheric pressure distillation tower 5, and part is extracted as refined methanol.

[0068] This embodiment takes a 2350 t / d refined methanol distillation unit as an example, the ethanol content in the feed crude alcohol is calculated as 2000 ppm (at the end of the catalyst period), and the refined alcohol target value is ≤10 ppm; the operating pressure, temperature and refined alcohol output of each tower in this embodiment are as follows:

[0069]

[0070]

[0071] In this embodiment, the top heat of the pre-distillation tower 1, the pressure distillation tower 3, the secondary pressure distillation tower 4, and the atmospheric distillation tower 5 is fully utilized, and the steam consumption per unit is significantly reduced from the consumption of the traditional process to 0.5-0.55 tons of steam / ton of refined alcohol, which greatly reduces energy consumption. In addition, through the effective recovery and utilization of heat, the thermal efficiency of the entire distillation system is improved, the system operation cost is reduced, the economic benefits of the enterprise are improved, and the emission of carbon dioxide and other pollutants is reduced, which is in line with the green and environmentally friendly production concept.

[0072] Embodiment 4:

[0073] The difference between the fourth embodiment and the third embodiment is that, in the present embodiment, the pre-distillation tower 1 is connected to the negative pressure distillation tower 2 and the negative pressure distillation tower 2 70 respectively, and the negative pressure distillation tower 2 and the negative pressure distillation tower 2 70 are connected to the pressurized distillation tower 3 respectively, and the pre-distillation tower 1 is connected to the negative pressure distillation tower 2 and the negative pressure distillation tower 2 70 respectively through the pre-tower kettle extraction pipeline 8 and the pre-tower kettle extraction pipeline 1 71; the bottom of the negative pressure distillation tower 2 70 is connected to the negative pressure tower kettle extraction pipeline 10 through the negative pressure tower 2 kettle extraction pipeline 72, or is directly connected to the pressurized distillation tower 3 through the negative pressure tower 2 kettle extraction pipeline 72. The distillation tower 3 is connected, and the vacuum tower 2 kettle extraction pipeline 72 passes through the first-level feed preheater 12 of the pressure tower and the second-level feed preheater 13 of the pressure tower; the vacuum tower 2 kettle extraction pipeline 72 is provided with a vacuum tower 2 kettle pump 86; the vacuum distillation tower 2 70 is provided with a vacuum tower 2 reboiler 73, and the top of the vacuum distillation tower 2 is connected to the input end of the vacuum tower 2 reboiler 73 through the vacuum tower top extraction pipeline 40, and the gas extracted from the top of the vacuum distillation tower 2 provides heat to the vacuum tower 2 reboiler 73; the heat at the top of the vacuum distillation tower 2 is utilized, and the steam unit consumption is further reduced.

[0074] The output end of the negative pressure tower second reboiler 73 is connected to the negative pressure tower reflux device through the negative pressure tower second reboiler output pipeline 74; the negative pressure tower reflux device includes a negative pressure tower reflux tank 39, and the negative pressure tower reflux tank 39 is connected to the output end of the negative pressure tower second reboiler 73 through the negative pressure tower second reboiler output pipeline 74. The structure of the negative pressure tower reflux device is the same as that of Example 1, and will not be described in detail here; the gas phase refined alcohol extracted from the top of the negative pressure distillation tower 2 is used as a heat source for the negative pressure tower second The reboiler 73 provides heat, and the liquid phase after heat exchange and cooling with the negative pressure tower second reboiler 73 enters the negative pressure tower reflux tank 39. Part of the liquid phase in the negative pressure tower reflux tank 39 is refluxed to the negative pressure distillation tower 2, and part is produced as refined methanol; the gas phase in the negative pressure tower reflux tank 39 is condensed by the negative pressure tower top secondary condenser 48, and the liquid phase returns to the negative pressure tower reflux tank 39, and the gas phase is produced through the non-condensable steam production pipeline 49. The produced non-condensable steam enters the exhaust gas treatment system for treatment.

[0075] The top of the negative pressure distillation tower 2 70 is provided with a negative pressure tower 2 reflux device, and the negative pressure tower 2 reflux device includes a negative pressure tower 2 reflux tank 75, and the negative pressure tower 2 reflux tank 75 is connected to the top of the negative pressure distillation tower 2 70 through a negative pressure tower 2 top extraction pipeline 76, and a negative pressure tower 2 primary condenser 77 is provided on the negative pressure tower 2 top extraction pipeline 76; the bottom of the negative pressure tower 2 reflux tank 75 is connected to the upper part of the negative pressure distillation tower 2 70 through a negative pressure tower 2 reflux pipeline 78, and the negative pressure tower 2 reflux pipeline 79 is connected to the upper part of the negative pressure distillation tower 2 70. A negative pressure tower two reflux extraction pump 79 is provided on line 78, and the negative pressure tower two reflux pipeline 78 is connected to the negative pressure tower two refined methanol extraction pipeline 80, and the negative pressure tower two refined methanol extraction pipeline 80 can be directly connected to the refined methanol tank 46. In this case, the negative pressure tower two refined methanol extraction pipeline 80 needs to be provided with a cooler. Another form of negative pressure tower two refined methanol extraction pipeline 80 is connected to the negative pressure tower refined methanol extraction pipeline 44, and the refined methanol extracted from the negative pressure distillation tower two 70 is connected to the negative pressure distillation tower 2 The extracted refined methanol is mixed, cooled together through the negative pressure tower top cooler 45, and then enters the refined methanol tank 46 for storage; the upper part of the negative pressure tower second reflux tank 75 is connected to the negative pressure tower second secondary condenser 82 through the top pipeline 2 81, and the output ends of the negative pressure tower second secondary condenser 82 are respectively connected to the non-condensable steam extraction pipeline 2 83 and the condensate pipeline 2 84, the condensate pipeline 2 84 is connected to the negative pressure tower second reflux tank 75, and the non-condensable steam extraction pipeline 2 83 is provided with a vacuum pump 2 87; The gas phase extracted from the top of the negative pressure distillation tower 70 is condensed by the first-level condenser 77 of the negative pressure tower and then enters the reflux tank 75 of the negative pressure tower. Part of the liquid phase in the reflux tank 75 of the negative pressure tower flows back to the negative pressure distillation tower 70, and part of it is extracted as refined methanol; the gas phase in the reflux tank 75 of the negative pressure tower is condensed by the second-level condenser 82 of the negative pressure tower, and the liquid phase returns to the reflux tank 75 of the negative pressure tower, and the gas phase is extracted through the non-condensable steam extraction pipeline 83. The extracted non-condensable gas enters the waste gas treatment system for treatment.

[0076] In this embodiment, the lower part of the secondary pressure distillation tower 4 is connected with a wastewater extraction pipeline 2 85 for discharging wastewater that meets the standards.

[0077] This embodiment takes a 2350 t / d refined methanol distillation unit as an example, the ethanol content in the feed crude alcohol is calculated as 2000 ppm (at the end of the catalyst period), and the refined alcohol target value is ≤10 ppm; the operating pressure, temperature and refined alcohol output of each tower in this embodiment are as follows:

[0078]

[0079] In this embodiment, a negative pressure distillation tower 2 70 is provided, and the heat at the top of the negative pressure distillation tower 2 is also utilized to further reduce the steam consumption to 0.4-0.45 tons of steam / ton of refined alcohol, and the energy saving effect is more significant; by adding the negative pressure distillation tower 2 70, a deeper heat recovery is achieved, and the overall thermal efficiency of the system is improved; due to more efficient thermal coupling, the operating cost of the system is further reduced, and the economic benefit is more obvious; the environmental impact is further reduced, which is conducive to achieving sustainable development and environmental protection.

[0080] In summary, due to the adoption of the above-mentioned technical scheme, the present application can significantly improve the energy utilization efficiency of the methanol distillation process, reduce production costs, reduce environmental pollution, and has significant economic and social benefits; the tower configuration and specific heat exchange network set up in the present application ensure the efficient utilization of heat and the reduction of energy consumption, and realize efficient thermal energy utilization; and can improve the distillation efficiency.

[0081] The devices, connection relationships, etc. not specifically described above all belong to the prior art and will not be described in detail in the present invention.

[0082] 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.

[0083] 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.

[0084] 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 methanol distillation process based on multi-effect thermal coupling, characterized in that: The steps include: The crude methanol is preheated by a pre-tower feed preheater (7); The preheated crude methanol enters the pre-distillation tower (1) for distillation, and the gas phase extracted from the top of the pre-distillation tower (1) goes to the negative pressure tower reboiler 1 (23) to provide the heat required for distillation for the negative pressure distillation tower (2); The material extracted from the bottom of the pre-distillation tower (1) enters the negative pressure distillation tower (2) for distillation, and the material extracted from the bottom of the negative pressure distillation tower (2) enters the pressure distillation tower (3) for further distillation; The gas phase extracted from the top of the pressure distillation tower (3) is respectively sent to the secondary pressure tower reboiler (21) and the atmospheric pressure tower reboiler (22) to provide the heat required for distillation for the secondary pressure distillation tower (4) and the atmospheric pressure distillation tower (5); the gas phase extracted from the top of the pressure distillation tower (3) exchanges heat with the secondary pressure tower reboiler (21) and the atmospheric pressure tower reboiler (22), and then part of it is refluxed to the pressure distillation tower (3), and part of it is extracted as extracted refined methanol; The liquid phase in the bottom of the pressure distillation tower (3) is sent to the secondary pressure distillation tower (4), and the gas phase at the top of the secondary pressure distillation tower (4) is sent to the pre-tower reboiler (19) to provide the heat required for distillation for the pre-distillation tower (1); after the gas phase at the top of the secondary pressure distillation tower (4) exchanges heat with the pre-tower reboiler (19), part of it is refluxed to the secondary pressure distillation tower (4), and part of it is extracted as refined methanol; The material extracted from the bottom of the secondary pressure distillation tower (4) enters the atmospheric pressure distillation tower (5) for distillation. The gas phase extracted from the top of the atmospheric pressure distillation tower (5) goes to the second negative pressure tower reboiler (24) to provide the heat required for distillation for the negative pressure distillation tower (2); after the atmospheric pressure distillation tower (5) exchanges heat with the second negative pressure tower reboiler (24), part of it flows back to the atmospheric pressure distillation tower (5), and part of it is extracted as refined methanol; fusel alcohol is extracted from one side of the atmospheric pressure distillation tower (5), and waste water is extracted from the bottom of the atmospheric pressure distillation tower (5).

2. A methanol distillation process based on multi-effect thermal coupling according to claim 1, characterized in that: The gas phase extracted from the top of the negative pressure distillation tower (2) is partially refluxed to the negative pressure distillation tower (2) after condensation, and the remaining part is extracted as refined methanol.

3. A methanol distillation process based on multi-effect thermal coupling according to claim 1, characterized in that: The materials in the bottom of the negative pressure distillation tower (2) are preheated by the first-stage feed preheater (12) of the pressure tower and the second-stage feed preheater (13) of the pressure tower, and then enter the pressure distillation tower (3).

4. A methanol distillation process based on multi-effect thermal coupling according to claim 1, characterized in that: The liquid phase extracted from the bottom of the pre-distillation tower (1) enters the negative pressure distillation tower (2) and the second negative pressure distillation tower (70) for distillation respectively; the gas phase extracted from the top of the negative pressure distillation tower (2) is sent to the second negative pressure distillation tower reboiler (73) to provide the heat required for distillation for the second negative pressure distillation tower (70); after the gas phase extracted from the top of the negative pressure distillation tower (2) exchanges heat with the second negative pressure distillation tower reboiler (73), part of it flows back to the negative pressure distillation tower (2), and part of it is extracted as refined methanol; after the gas phase extracted from the top of the second negative pressure distillation tower (70) is condensed, part of it flows back to the second negative pressure distillation tower (70), and part of it is extracted as extracted refined methanol; the materials extracted from the bottoms of the negative pressure distillation tower (2) and the second negative pressure distillation tower (70) enter the pressurized distillation tower (3) for further distillation.

5. A methanol distillation process based on multi-effect thermal coupling according to claim 4, characterized in that: The materials in the bottom of the negative pressure distillation tower (1) and the materials in the bottom of the second negative pressure distillation tower (70) are preheated by the first feed preheater (12) of the pressure tower and the second feed preheater (13) of the pressure tower before entering the pressure distillation tower (3).

6. A methanol distillation process based on multi-effect thermal coupling according to any one of claims 3 or 5, characterized in that: The liquid phase of the bottom of the pressure distillation tower (3) goes to the pressure tower primary feed preheater (12) to provide heat for the pressure tower primary feed preheater (12).

7. According to a methanol distillation process based on multi-effect thermal coupling as described in any one of claims 3 or 5, steam is used to heat the pressurized tower reboiler (20) arranged in the bottom of the pressurized distillation tower (3), and the heated steam passes through the pressurized tower secondary feed preheater (13), and after heating the pressurized tower secondary feed preheater (13), it is produced as condensate.

8. A methanol distillation device based on multi-effect thermal coupling, characterized in that: The invention comprises a pre-distillation tower (1), a negative pressure distillation tower (2), a pressure distillation tower (3), a secondary pressure distillation tower (4), and an atmospheric pressure distillation tower (5) which are connected in sequence. The pre-distillation tower (1), the pressure distillation tower (3), the secondary pressure distillation tower (4), and the atmospheric pressure distillation tower (5) are respectively provided with a pre-tower reboiler (19), a pressure tower reboiler (20), a secondary pressure tower reboiler (21), and an atmospheric pressure tower reboiler (22). The lower part of the negative pressure distillation tower (2) is provided with a negative pressure tower reboiler. One (23) and negative pressure tower reboiler two (24), wherein the gas phase extracted from the top of the secondary pressure distillation tower (4) provides heat to the pre-tower reboiler (19); the gas phase extracted from the top of the pressure distillation tower (3) provides heat to the secondary pressure tower reboiler (21) and the atmospheric pressure tower reboiler (22) respectively; the gas phase extracted from the top of the pre-distillation tower (1) provides heat to the negative pressure tower reboiler one (23); and the gas phase extracted from the top of the atmospheric pressure distillation tower (5) provides heat to the negative pressure tower reboiler two (24).

9. A methanol distillation device based on multi-effect thermal coupling according to claim 8, characterized in that: A negative pressure tower reflux device is provided at the top of the negative pressure distillation tower (2).

10. A methanol distillation device based on multi-effect thermal coupling according to claim 8, characterized in that: The pre-distillation tower (1) is connected to the negative pressure distillation tower (2) and the negative pressure distillation tower 2 (70) respectively, and the negative pressure distillation tower (2) and the negative pressure distillation tower 2 (70) are connected to the pressurized distillation tower (3) respectively. The negative pressure distillation tower 2 (70) is provided with a negative pressure tower 2 reboiler (73), and the gas extracted from the top of the negative pressure distillation tower (2) provides heat for the negative pressure tower 2 reboiler (73).

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