Crude methanol five-tower multi-effect rectification device

Abstract

The utility model provides a coarse methanol five-tower multi-effect rectification device which comprises a pre-rectification tower, a negative pressure rectification tower, a normal pressure rectification tower, a low pressure rectification tower and a high pressure rectification tower, a first pre-tower reboiler and a second pre-tower reboiler are arranged on the lower portion of the pre-rectification tower, and a first negative pressure tower reboiler and a second negative pressure tower reboiler are arranged on the lower portion of the negative pressure rectification tower. An atmospheric tower reboiler, a low-pressure tower reboiler and a high-pressure tower reboiler are respectively arranged at the lower parts of the atmospheric rectifying tower, the low-pressure rectifying tower and the high-pressure rectifying tower; heat at the top of the pre-rectifying tower is used for supplying heat to a first negative-pressure tower reboiler, heat at the top of the normal-pressure rectifying tower is used for supplying heat to a second negative-pressure tower reboiler, and heat at the top of the low-pressure rectifying tower is used for supplying heat to a normal-pressure tower reboiler and a second pre-tower reboiler; according to the invention, the steam unit consumption can be reduced to 0.52-0.54 t of steam per ton of refined methanol, and the highest steam unit consumption is 0.54 t of steam per ton of refined methanol, so that the steam unit consumption is reduced.

Description

Technical Field

[0001] This application relates to the field of chemical technology, specifically to a five-tower multi-effect distillation device for crude methanol. Background Technology

[0002] Methanol is an important chemical raw material, widely used in chemical, energy and fuel cell fields. In the production of methanol, distillation is a key separation operation used to purify methanol products. Traditional methanol distillation usually adopts a three-tower process: a pre-tower, an atmospheric tower, and an atmospheric tower. The overhead steam of the atmospheric tower is used to heat the atmospheric tower to achieve energy saving. However, the top of the atmospheric tower and the pre-tower are cooled by circulating water, which leads to a large amount of heat being wasted, resulting in a high steam consumption of the entire system, approximately 1.2t steam / t refined methanol.

[0003] With increasingly stringent national requirements for carbon emission targets, a new technology is needed to recover heat from existing systems to achieve energy conservation and emission reduction goals. Therefore, energy-saving devices such as five-tower triple-effect, five-tower quadruple-effect, and five-tower multi-effect systems have emerged. A technical solution disclosed in application number 202421477006.3 for a crude methanol five-tower thermally coupled refining device includes a pre-distillation tower, an atmospheric distillation tower, a medium-pressure distillation tower, a pressurized distillation tower one, and a pressurized distillation tower two connected in sequence. The top of the pre-distillation tower is connected to the reboiler of the atmospheric distillation tower one, the top of the medium-pressure distillation tower is connected to the reboiler of the pre-distillation tower, and the pressurized distillation tower one... The top of the column is connected to the reboiler of the medium-pressure column and the reboiler of the second pressurized column. The top of the second pressurized distillation column is connected to the second atmospheric distillation column via the top outlet pipeline of the second pressurized column. The top steam of the first pressurized distillation column in this application provides heat to the medium-pressure distillation column and the second pressurized distillation column. The top steam of the medium-pressure distillation column provides heat to the pre-distillation column. The top steam of the pre-distillation column and the second pressurized distillation column provides heat to the atmospheric distillation column, thus making full use of the heat at the top of each distillation column. Through this application, the unit consumption of the methanol distillation process can be reduced from 1.2t steam / t refined alcohol to 0.50-0.60t steam / t refined alcohol, achieving a significant reduction in energy consumption.

[0004] The steam consumption of the methanol distillation process in the above application is significantly reduced compared to existing technologies, but the maximum of 0.60t steam / t refined methanol is still relatively high, and there is room for further reduction.

[0005] In summary, a new technical solution is needed to address the aforementioned technical problems. Utility Model Content

[0006] This application provides a five-tower multi-effect distillation apparatus for crude methanol, comprising a pre-distillation tower, a negative pressure distillation tower, an atmospheric pressure distillation tower, a low-pressure distillation tower, and a high-pressure distillation tower connected in sequence. The lower part of the pre-distillation tower is equipped with a first pre-tower reboiler and a second pre-tower reboiler. The lower part of the negative pressure distillation tower is equipped with a first negative pressure reboiler and a second negative pressure reboiler. The lower parts of the atmospheric pressure distillation tower, the low-pressure distillation tower, and the high-pressure distillation tower are respectively equipped with an atmospheric pressure reboiler, a low-pressure reboiler, and a high-pressure reboiler. The heat from the top of the pre-distillation tower is used to heat the first negative pressure reboiler; the heat from the top of the atmospheric pressure distillation tower is used to heat the second negative pressure reboiler; the heat from the top of the low-pressure distillation tower is used to heat both the atmospheric pressure reboiler and the second pre-tower reboiler; and the heat from the top of the high-pressure distillation tower is used to heat the low-pressure reboiler.

[0007] As a preferred embodiment, the top of the pre-distillation column is connected to the first reboiler of the negative pressure column via a pre-distillation column top outlet pipeline; the top of the atmospheric pressure distillation column is connected to the second reboiler of the negative pressure column via an atmospheric pressure column top outlet pipeline; the top of the low-pressure distillation column is connected to the second pre-distillation column reboiler and the atmospheric pressure column reboiler via a low-pressure column top outlet pipeline; and the top of the high-pressure distillation column is connected to the low-pressure column reboiler via a high-pressure column top outlet pipeline.

[0008] As a preferred embodiment, the output ends of the pre-reboiler II and the atmospheric reboiler are respectively connected to the low-pressure column reflux tank. The bottom of the low-pressure column reflux tank is connected to the low-pressure distillation column through the low-pressure column reflux pipeline, and the low-pressure column reflux pipeline is connected to the low-pressure column refined methanol collection pipeline.

[0009] As a preferred embodiment, the output end of the reboiler of the negative pressure tower is connected to the pre-tower reflux tank, the bottom of the pre-tower reflux tank is connected to the pre-distillation tower through the pre-tower reflux pipeline, the top of the pre-tower reflux tank is connected to the extraction tower through the gas phase exit pipeline, a pre-tower tail cooler is installed on the gas phase exit pipeline, a non-condensable gas exit pipeline is connected to the top of the extraction tower, an extraction water pipeline is connected to one side of the extraction tower, and a miscellaneous oil exit pipeline is connected to one side of the extraction tower.

[0010] As a preferred embodiment, the output end of the negative pressure tower reboiler two is connected to the atmospheric pressure tower reflux tank, the bottom of the atmospheric pressure tower reflux tank is connected to the atmospheric pressure distillation tower through the atmospheric pressure tower reflux pipeline, and the atmospheric pressure tower reflux pipeline is connected to the atmospheric pressure tower refined methanol collection pipeline.

[0011] As a preferred embodiment, the output end of the low-pressure tower reboiler is connected to the high-pressure tower reflux tank, the bottom of the high-pressure tower reflux tank is connected to the high-pressure distillation tower through the high-pressure tower reflux pipeline, and the high-pressure tower reflux pipeline is connected to the high-pressure tower refined methanol collection pipeline.

[0012] As a preferred embodiment, the input end of the pre-tower reboiler is connected to the steam pipeline, and the output end of the pre-tower reboiler is connected to the steam condensate collection pipeline.

[0013] As a preferred embodiment, the input end of the high-pressure tower reboiler is connected to steam pipeline two, and the output end of the high-pressure tower reboiler is connected to steam condensate collection pipeline two.

[0014] As a preferred embodiment, the bottom of the negative pressure distillation column is connected to the atmospheric pressure distillation column via a negative pressure column bottom pipeline, and a negative pressure column bottom pump and an atmospheric pressure column feed preheater are installed on the negative pressure column bottom pipeline.

[0015] As a preferred embodiment, the bottom of the atmospheric distillation column is connected to the low-pressure distillation column via an atmospheric column bottom pipeline, and the low-pressure column bottom pipeline is equipped with an atmospheric column bottom pump and a low-pressure column feed preheater.

[0016] As a preferred embodiment, the bottom of the low-pressure distillation column is connected to the high-pressure distillation column via a low-pressure column bottom pipeline, and a low-pressure column bottom pump and a high-pressure column feed preheater are installed on the low-pressure column bottom pipeline.

[0017] As a preferred embodiment, the second steam condensate extraction pipeline passes sequentially through a high-pressure tower feed preheater, a low-pressure tower feed preheater, and an atmospheric pressure tower feed preheater.

[0018] As a preferred embodiment, the top of the negative pressure distillation column is connected to the negative pressure column reflux tank via a negative pressure column top outlet pipeline, and a negative pressure column condenser is installed on the negative pressure column top outlet pipeline. The bottom of the negative pressure column reflux tank is connected to the negative pressure distillation column via a negative pressure column reflux pipeline, and the negative pressure column reflux pipeline is connected to the negative pressure column refined methanol outlet pipeline. The reflux tank's vapor phase outlet pipeline is connected to a buffer tank, and a negative pressure column tail cooler is installed on the reflux tank's vapor phase outlet pipeline. The bottom of the buffer tank is connected to the negative pressure column reflux tank via a buffer tank bottom pipeline, and a vacuum pipeline is connected to the top of the buffer tank.

[0019] As a preferred embodiment, a feed pipeline is connected to one side of the pre-distillation column, and a pre-column preheater 1 and a pre-column preheater 2 are connected in parallel on the feed pipeline.

[0020] As a preferred embodiment, the bottom of the high-pressure distillation column is connected to a wastewater pipeline, which passes through a preheater (preheater 2). A wastewater cooler is installed on the wastewater pipeline at the output end of the preheater (preheater 2).

[0021] As a preferred embodiment, the atmospheric pressure tower refined methanol extraction pipeline, the low pressure tower refined methanol extraction pipeline, and the high pressure tower refined methanol extraction pipeline are respectively connected to the main refined methanol extraction pipeline. The main refined methanol extraction pipeline passes through a preheater in the preheater tower, and a product cooler is installed on the main refined methanol extraction pipeline at the output end of the preheater in the preheater tower.

[0022] This application utilizes the heat from the steam at the top of the pre-distillation column to heat the reboiler 1 of the negative pressure column, and the heat from the steam at the top of the atmospheric pressure distillation column to heat the reboiler 2 of the negative pressure column, together meeting the energy requirements for distillation in the negative pressure distillation column; the energy from the methanol steam at the top of the low-pressure distillation column heats the reboiler of the atmospheric pressure column and the reboiler 2 of the pre-distillation column, meeting the energy requirements for distillation in the atmospheric pressure distillation column and the pre-distillation column; the steam at the top of the high-pressure distillation column heats the reboiler of the low-pressure column, meeting the energy requirements for distillation in the low-pressure distillation column; by adjusting the coupling sequence, the five-column thermal coupling process of this application can reduce the steam consumption to 0.52-0.54 t steam / t refined methanol, with the highest steam consumption being 0.54 t steam / t refined methanol, less than 0.6 t steam / t refined methanol, further reducing the steam consumption; and it can produce methanol with a concentration ≥99.99% and an ethanol content between 10-100 ppm. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of this application;

[0024] 1. Pre-distillation column; 2. Negative pressure distillation column; 3. Atmospheric pressure distillation column; 4. Low-pressure distillation column; 5. High-pressure distillation column; 6. Feed line; 7. Preheater 1 of the pre-distillation column; 8. Preheater 2 of the pre-distillation column; 9. Pre-distillation column reboiler line; 10. Pre-distillation column reboiler pump; 11. Negative pressure column reboiler line; 12. Negative pressure column reboiler pump; 13. Atmospheric pressure column feed preheater; 14. Atmospheric pressure column reboiler line; 15. Atmospheric pressure column reboiler pump; 16. Low-pressure column feed preheater; 17. Low-pressure column reboiler line; 18. Low-pressure column reboiler pump; 19. High-pressure column feed preheater; 20. Fusel alcohol side-collection line; 21. Fusel alcohol cooler; 22. 23. Wastewater pipeline; 24. Wastewater extraction pump; 25. Wastewater cooler; 26. Pre-tower reboiler 1; 27. Pre-tower reboiler 2; 28. Negative pressure tower reboiler 1; 29. ​​Negative pressure tower reboiler 2; 30. Atmospheric pressure tower reboiler; 31. Low-pressure tower reboiler; 32. High-pressure tower reboiler; 33. Pre-tower top extraction pipeline; 34. Atmospheric pressure tower top extraction pipeline; 35. Low-pressure tower top extraction pipeline; 36. High-pressure tower top extraction pipeline; 37. Steam pipeline 1; 38. Steam condensate extraction pipeline 1; 39. Steam condensate extraction pipeline 2; 40. Low-pressure tower reflux tank connection pipeline. ; 41. Low-pressure tower reflux tank; 42. Low-pressure tower reflux pipeline; 43. Low-pressure tower refined methanol production pipeline; 44. Low-pressure tower reflux pump; 45. Pre-tower reflux tank connection pipeline; 46. Pre-tower reflux tank; 47. Pre-tower reflux pipeline; 48. Pre-tower reflux pump; 49. Gas phase production pipeline; 50. Extraction tower; 51. Pre-tower tail cooler; 52. Non-condensable gas production pipeline; 53. Extraction water pipeline; 54. Miscellaneous oil production pipeline; 55. Atmospheric pressure tower reflux tank connection pipeline; 56. Atmospheric pressure tower reflux tank; 57. Atmospheric pressure tower reflux pipeline; 58. Atmospheric pressure tower reflux pump; 59. Atmospheric pressure tower refined methanol production pipeline; 60. 61. High-pressure tower reflux tank connection pipeline; 62. High-pressure tower reflux tank; 63. High-pressure tower reflux pipeline; 64. High-pressure tower reflux pump; 65. High-pressure tower refined methanol extraction pipeline; 66. Top extraction pipeline of negative pressure tower; 67. Negative pressure tower reflux tank; 68. Negative pressure tower condenser; 69. Negative pressure tower reflux pipeline; 70. Negative pressure tower refined methanol extraction pipeline; 71. Reflux tank gas phase extraction pipeline; 72. Buffer tank; 73. Negative pressure tower tail cooler one; 74. Bottom pipeline of buffer tank; 75. Vacuum pipeline; 76. Main refined methanol extraction pipeline; 77. Product cooler; 78. Refined methanol tank. Detailed Implementation

[0025] The following is in conjunction with the appendix Figure 1 The specific embodiments of this utility model will be described in detail below. It should be noted that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of this utility model. Example 1

[0026] This application provides a five-tower thermally coupled refining apparatus for crude methanol, comprising a pre-distillation tower 1, a negative pressure distillation tower 2, an atmospheric pressure distillation tower 3, a low pressure distillation tower 4, and a high pressure distillation tower 5 connected in sequence; preferably, the top pressure of the pre-distillation tower 1 is 120-180 kPa, the top pressure of the negative pressure distillation tower 2 is 40-70 kPa, the top pressure of the atmospheric pressure distillation tower 3 is 125-140 kPa, the top pressure of the low pressure distillation tower 4 is 280-350 kPa, and the top pressure of the high pressure distillation tower 5 is 705-800 kPa;

[0027] A feed line 6 is provided on one side of the pre-distillation column 1. A pre-column preheater 7 and a pre-column preheater 8 are connected in parallel on the feed line 6 to preheat the crude methanol material entering the pre-distillation column 1, improving distillation stability. The bottom of the pre-distillation column 1 is connected to the negative pressure distillation column 2 via a pre-column bottom outlet line 9, on which a pre-column bottom pump 10 is installed. The bottom of the negative pressure distillation column 2 is connected to the atmospheric pressure distillation column 3 via a negative pressure column bottom outlet line 11, on which a negative pressure column bottom pump 12 and an atmospheric pressure column feed preheater 13 are installed. The bottom of the atmospheric pressure distillation column 3 is connected to the low-pressure distillation column 4 via an atmospheric pressure column bottom outlet line 14, on which an atmospheric pressure column bottom pump 10 is installed. 5. Low-pressure column feed preheater 16; The bottom of the low-pressure distillation column 4 is connected to the high-pressure distillation column 5 through the low-pressure column bottom pipeline 17. The low-pressure column bottom pipeline 17 is equipped with a low-pressure column bottom pump 18 and a high-pressure column feed preheater 19; A fusel oil side sampling pipeline 20 is provided on one side of the high-pressure distillation column 5 for collecting fusel oil. A fusel oil cooler 21 is provided on the fusel oil side sampling pipeline 20; The bottom of the high-pressure distillation column 5 is connected to a wastewater pipeline 22. A wastewater collection pump 23 is provided on the wastewater pipeline 22; The wastewater pipeline 22 passes through the preheater 8, and a wastewater cooler 24 is provided on the wastewater pipeline 22 at the output end of the preheater 8; The heat of the wastewater is supplied by the preheater 8, and the wastewater after heat exchange is cooled by the wastewater cooler 24 before being collected.

[0028] The lower part of the pre-distillation column 1 is equipped with a first pre-distillation column reboiler 25 and a second pre-distillation column reboiler 26. The lower part of the negative pressure distillation column 2 is equipped with a first negative pressure distillation column reboiler 27 and a second negative pressure distillation column reboiler 28. The lower parts of the atmospheric pressure distillation column 3, the low-pressure distillation column 4, and the high-pressure distillation column 5 are respectively equipped with an atmospheric pressure distillation column reboiler 29, a low-pressure distillation column reboiler 30, and a high-pressure distillation column reboiler 31. The heat from the top of the pre-distillation column 1 is used to heat the first negative pressure distillation column reboiler 27. Specifically, the top of the pre-distillation column 1 is connected to the first negative pressure distillation column reboiler 27 via a pre-distillation column top outlet pipeline 32. The heat from the top of the atmospheric pressure distillation column 3 is used to heat the second negative pressure distillation column reboiler 27. The reboiler 28 of the low-pressure distillation column 3 is heated. Specifically, the top of the atmospheric distillation column 3 is connected to the reboiler 28 of the low-pressure distillation column 2 through the atmospheric distillation column top outlet pipeline 33. The heat from the top of the low-pressure distillation column 4 is used to heat the reboiler 29 of the atmospheric distillation column 29 and the pre-reboiler 26 of the low-pressure distillation column 4 through the low-pressure distillation column top outlet pipeline 34. The heat from the top of the high-pressure distillation column 5 is used to heat the reboiler 30 of the low-pressure distillation column 30. Specifically, the top of the high-pressure distillation column 5 is connected to the reboiler 30 of the low-pressure distillation column 30 through the high-pressure distillation column top outlet pipeline 35.

[0029] The aforementioned pre-reboiler 25 and high-pressure reboiler 31 are heated by steam. Specifically: the input end of the pre-reboiler 25 is connected to steam pipeline 36, and the output end of the pre-reboiler 25 is connected to steam condensate collection pipeline 37. The required steam pressure for the pre-reboiler 25 is 0.471 MPa. The input end of the high-pressure reboiler 31 is connected to steam pipeline 38, and the output end of the high-pressure reboiler 31 is connected to steam pipeline 39. The steam condensate extraction pipeline 2 39 is connected, and the steam pressure required by the high-pressure tower reboiler 31 is 1.167 MPaG. In order to further improve the utilization rate of steam, the steam condensate extraction pipeline 2 39 passes through the high-pressure tower feed preheater 19, the low-pressure tower feed preheater 16, and the atmospheric tower feed preheater 13 in sequence. After providing heat to the high-pressure tower feed preheater 19, the low-pressure tower feed preheater 16, and the atmospheric tower feed preheater 13, it is extracted as condensate.

[0030] In this embodiment, the steam heat from the top of the pre-distillation column 1 is used to heat the reboiler 27 of the negative pressure column, and the steam heat from the top of the atmospheric distillation column 3 is used to heat the reboiler 28 of the negative pressure column, together meeting the energy requirements of the negative pressure distillation column 2. The energy of the methanol steam from the top of the low-pressure distillation column 4 is used to heat the reboiler 29 of the atmospheric pressure column and the reboiler 26 of the pre-distillation column, meeting the energy requirements of the atmospheric distillation column 3 and the pre-distillation column 1. The steam from the top of the high-pressure distillation column 5 is used to heat the reboiler 30 of the low-pressure column, meeting the energy requirements of the low-pressure distillation column 4. By adjusting the coupling sequence, the five-column thermal coupling process of this application can reduce the steam consumption to 0.52-0.54 t steam / t refined methanol, with the highest steam consumption being 0.54 t steam / t refined methanol, which is less than 0.6 t steam / t refined methanol, further reducing the steam consumption. Moreover, it can produce methanol with a concentration ≥99.99%, and the ethanol content is guaranteed to be between 10-100 ppm. Example 2

[0031] In this embodiment, the reflux and / or refined methanol production of each column are described in detail, specifically:

[0032] The output ends of the pre-reboiler 26 and the atmospheric reboiler 29 are connected to the low-pressure column reflux tank 41 via the low-pressure column reflux tank connecting pipeline 40. The bottom of the low-pressure column reflux tank 41 is connected to the low-pressure distillation column 4 via the low-pressure column reflux pipeline 42. The low-pressure column reflux pipeline 42 is connected to the low-pressure column refined methanol collection pipeline 43. A low-pressure column reflux pump 44 is installed on the low-pressure column reflux pipeline 42. The steam at the top of the low-pressure distillation column 4 provides heat to the pre-reboiler 26 and the atmospheric reboiler 29, thereby providing the energy required for distillation to the pre-distillation column 1 and the atmospheric distillation column 3. The material after heat exchange in the pre-reboiler 26 and the atmospheric reboiler 29 enters the low-pressure column reflux tank 41. Part of it is collected as refined methanol, and part of it is returned to the low-pressure distillation column 4 for further distillation, thereby improving the accuracy of distillation.

[0033] The output end of the negative pressure tower reboiler 27 is connected to the pre-tower reflux tank 46 via a pre-tower reflux tank connecting pipeline 45. The bottom of the pre-tower reflux tank 46 is connected to the pre-distillation column 1 via a pre-tower reflux pipeline 47. A pre-tower reflux pump 48 is installed on the pre-tower reflux pipeline 47. The top of the pre-tower reflux tank 46 is connected to the extraction column 50 via a gas phase exit pipeline 49. A pre-tower tail cooler 51 is installed on the gas phase exit pipeline 49. The top of the extraction column 50 is connected to... A non-condensable gas extraction pipeline 52 is connected to the extraction tower 50. An extraction water pipeline 53 is connected to one side of the extraction tower 50, and a mixed oil extraction pipeline 54 is connected to the bottom side of the extraction tower 50. The steam at the top of the pre-distillation tower 1 provides heat to the reboiler 27 of the negative pressure tower, which in turn provides the energy required for distillation in the negative pressure distillation tower 2. The material after heat exchange enters the pre-tower reflux tank 46. The liquid phase is refluxed back to the pre-distillation tower 1 for further distillation, and the gas phase enters the extraction tower 50 for extraction, extracting non-condensable gas and mixed oil.

[0034] The output end of the reboiler 28 of the negative pressure tower is connected to the atmospheric pressure tower reflux tank 56 via the atmospheric pressure tower reflux tank connecting pipeline 55. The bottom of the atmospheric pressure tower reflux tank 56 is connected to the atmospheric pressure distillation column 3 via the atmospheric pressure tower reflux pipeline 57. An atmospheric pressure tower reflux pump 58 is installed on the atmospheric pressure tower reflux pipeline 57, which is connected to the atmospheric pressure tower refined methanol collection pipeline 59. The steam at the top of the atmospheric pressure distillation column 3 provides heat to the reboiler 28 of the negative pressure tower, thereby providing the energy required for distillation in the negative pressure distillation column 2. After heat exchange, the material enters the atmospheric pressure tower reflux tank 56, part of which is collected as refined methanol, and part of which is returned to the atmospheric pressure distillation column 3 for further distillation, thereby improving the accuracy of distillation.

[0035] The output end of the low-pressure reboiler 30 is connected to the high-pressure reflux tank 61 via the high-pressure reflux tank connection pipeline 60. The bottom of the high-pressure reflux tank 61 is connected to the high-pressure distillation column 5 via the high-pressure reflux pipeline 62. The high-pressure reflux pump 63 is installed on the high-pressure reflux pipeline 62, and the high-pressure reflux pipeline 62 is connected to the high-pressure refined methanol collection pipeline 64. The steam at the top of the high-pressure distillation column 5 provides heat to the low-pressure reboiler 30, thereby providing the energy required for distillation in the low-pressure distillation column 4. After heat exchange, the material enters the high-pressure reflux tank 61, part of which is collected as refined methanol, and part of which is returned to the high-pressure distillation column 5 for further distillation, thereby improving the accuracy of distillation.

[0036] The top of the negative pressure distillation column 2 is connected to the negative pressure column reflux tank 66 via a negative pressure column top outlet pipeline 65. A negative pressure column condenser 67 is installed on the negative pressure column top outlet pipeline 65. The bottom of the negative pressure column reflux tank 66 is connected to the negative pressure distillation column 2 via a negative pressure column reflux pipeline 68. A negative pressure column reflux pump 69 is installed on the negative pressure column reflux pipeline 68. The negative pressure column reflux pipeline 68 is connected to the negative pressure column refined methanol outlet pipeline 70. The negative pressure column reflux tank 66 is connected to the buffer tank 72 via a reflux tank gas phase outlet pipeline 71. A negative pressure tower tail cooler 73 is installed on the 1st column. The bottom of the buffer tank 72 is connected to the negative pressure tower reflux tank 66 through the bottom pipeline 74 of the buffer tank. The top of the buffer tank 72 is connected to the vacuum pipeline 75. The vapor at the top of the negative pressure distillation tower 2 enters the negative pressure tower reflux tank 66 after passing through the negative pressure tower condenser 67. The liquid phase in the negative pressure tower reflux tank 66 is collected as refined methanol, and part of it is returned to the negative pressure distillation tower 2 for further distillation. The gas phase in the negative pressure tower reflux tank 66 is condensed and enters the buffer tank 72. The liquid phase separated in the buffer tank 72 is returned to the negative pressure tower reflux tank 66.

[0037] Preferably, to facilitate the utilization of the heat from the refined methanol, the atmospheric pressure tower refined methanol outlet pipeline 59, the low-pressure tower refined methanol outlet pipeline 43, and the high-pressure tower refined methanol outlet pipeline 64 are respectively connected to the main refined methanol outlet pipeline 76. The main refined methanol outlet pipeline 76 passes through the preheater 7, and the main refined methanol outlet pipeline 76 at the output end of the preheater 7 is connected to the negative pressure tower refined methanol outlet pipeline 70. A product cooler 77 is installed on the main refined methanol outlet pipeline 76 at the output end of the preheater 7, and the main refined methanol outlet pipeline 76 at the output end of the preheater 7 is connected to the refined methanol tank 78 for easy storage of refined methanol products. Example 3

[0038] This embodiment provides a specific application scenario:

[0039] At a methanol plant, there is already a crude methanol refining and recovery unit with an annual output of 600,000 tons and a feed rate of 108,720 kg / h. The original five-tower process is now being modified by changing the feed sequence and thermal coupling method between the towers. Once the relevant process parameters are optimized to the best, the annual output can be increased to 700,000 tons through this five-tower thermal coupling process. The steam energy consumption for refined methanol is about 0.53-0.54 t steam / t refined methanol, and the methanol purity can reach more than 99.99%, with an ethanol content of less than 50 ppm.

[0040] Crude methanol is preheated in preheater 7 and / or preheater 8 to approximately 68°C. The preheated crude methanol then enters pre-distillation column 1 for distillation. The top pressure of pre-distillation column 1 is 129 kPa, the top temperature is 75°C, and the bottom temperature is 76°C. The vapor from the top of pre-distillation column 1 is sent to reboiler 27 of the negative pressure column to provide some of the heat required for distillation in negative pressure distillation column 2. After heat exchange in reboiler 27, the material enters the pre-distillation column reflux tank 46. The gas phase in the reflux tank 46 enters the pre-column tail cooler 51, and the cooled medium enters the extraction column 50. The non-condensable gas generated after extraction is discharged, and the liquid phase is refluxed back to the pre-column reflux tank 46. The liquid phase in the pre-column reflux tank 46 is refluxed back to the middle and upper part of the pre-distillation column 1. The pre-column reboiler 1 25 and the pre-column reboiler 26 provide the heat required for distillation in the pre-distillation column 1 in the form of indirect heating. The heat source of the pre-column reboiler 1 25 is steam, and the heat source of the pre-column reboiler 26 is the gas phase taken out from the top of the low-pressure distillation column 4.

[0041] The liquid phase collected from the bottom of pre-distillation column 1 enters the negative pressure distillation column 2 for distillation. The top pressure of the negative pressure distillation column 2 is 57 kPa, the top temperature is 50℃, and the bottom temperature is 59℃. The vapor phase collected from the top of the negative pressure distillation column 2 is condensed by the negative pressure column condenser 67 and then enters the negative pressure column reflux tank 66. The liquid phase in the negative pressure column reflux tank 66 is pressurized by the negative pressure column reflux pump 69 and divided into two streams. One stream flows back to the negative pressure distillation column 2, that is, it flows back to the upper middle part of the negative pressure distillation column 2 as reflux feed. The other stream... The methanol is extracted as refined methanol. The reboilers 27 and 28 of the negative pressure distillation column provide the heat required for the distillation of the negative pressure distillation column 2 in the form of indirect heating. The heat source of the reboiler 27 is the vapor phase extracted from the top of the pre-distillation column 1, and the heat source of the reboiler 28 is the vapor phase extracted from the top of the atmospheric pressure distillation column 3. The liquid in the bottom of the negative pressure distillation column 2 is pressurized by the bottom pump 12 and then enters the feed preheater 13 of the atmospheric pressure column for preheating. After the temperature is raised, it continues to enter the atmospheric pressure distillation column 3 for further distillation.

[0042] The atmospheric distillation column 3 has a top pressure of 128 kPa, a top temperature of 70°C, and a bottom temperature of 80°C. The vapor phase collected from the top of the atmospheric distillation column 3 goes to the reboiler 28 of the negative pressure column to provide part of the heat required for distillation in the negative pressure distillation column 2. After heat exchange, it enters the atmospheric reflux tank 56. The liquid phase in the atmospheric reflux tank 56 is pressurized by the atmospheric reflux pump 58 and divided into two streams. One stream flows back to the atmospheric distillation column 3, that is, it flows back to the middle and upper part of the atmospheric distillation column 3 as reflux feed. The other stream is collected as refined methanol. The atmospheric reboiler 29 provides the heat required for distillation in the atmospheric distillation column 3 in the form of indirect heating. The heat source is the vapor phase collected from the top of the low-pressure distillation column 4. The bottom liquid of the atmospheric distillation column 3 is pressurized by the atmospheric column bottom pump 15 and enters the low-pressure column feed preheater 16 for preheating. After the temperature is raised, it continues to enter the low-pressure distillation column 4 for distillation.

[0043] The pressure at the top of low-pressure distillation column 4 is 338 kPa, the temperature at the top is 98℃, and the temperature at the bottom is 112℃. The vapor phase at the top of low-pressure distillation column 4 splits into two streams. One stream goes to the atmospheric reboiler 29 to provide the heat required for distillation in atmospheric distillation column 3, and the other stream goes to the pre-distillation reboiler 26 to provide part of the heat required for distillation in pre-distillation column 1. After heat exchange, the two streams converge and then enter the low-pressure column reflux tank 41. The liquid phase in the low-pressure column reflux tank 41 is then pumped by the low-pressure column reflux pump 44. After compression, the liquid is divided into two streams. One stream flows back to the low-pressure distillation column 4, specifically to the upper middle part of the low-pressure distillation column 4 as reflux feed. The other stream is collected as refined methanol. The low-pressure column reboiler 30 provides the heat required for distillation in the low-pressure distillation column 4 in the form of indirect heating. The heat source is the vapor phase collected from the top of the high-pressure distillation column 5. The bottom liquid of the low-pressure distillation column 4 is pressurized by the low-pressure column bottom pump 18 and then enters the high-pressure column feed preheater 19 for preheating. After the temperature is raised, it continues to enter the high-pressure distillation column 5 for distillation.

[0044] The pressure at the top of the high-pressure distillation column 5 is 705 kPa, the temperature at the top is 123℃, and the temperature at the bottom is 165℃. The vapor phase from the top of the high-pressure distillation column 5 goes to the reboiler 30 of the low-pressure column to provide the heat required for distillation in the low-pressure distillation column 4, and then enters the reflux tank 61 of the high-pressure column. The liquid phase in the reflux tank 61 is pressurized by the high-pressure column reflux pump 63 and divided into two streams. One stream flows back to the high-pressure distillation column 5, that is, it flows back to the middle and upper part of the high-pressure distillation column 5 as reflux feed, and the other stream is collected as refined methanol. The heat source of the high-pressure column reboiler 31 is medium-pressure steam. The side stream of the high-pressure distillation column 5 is used to collect fusel oil, and the bottom is used to collect wastewater. The bottom wastewater is pressurized by the wastewater collection pump 23 and sent to the preheater 8 of the pre-column to preheat the crude alcohol, and then enters the wastewater cooler 24.

[0045] The methanol product streams from atmospheric distillation column 3, low-pressure distillation column 4, and high-pressure distillation column 5 are combined into one stream and enter the preheater 7 to preheat the crude methanol. The stream from the preheater 7 is mixed with the refined methanol product from the top of the negative pressure distillation column 2 and then enters the product cooler 77. The cooled methanol enters the refined methanol tank 78.

[0046] In this embodiment, the crude methanol feed rate is 108,720 kg / h, with a water content of approximately 7.91% and an ethanol content of approximately 0.18%. The crude methanol is preheated to 68°C by preheater 7 and preheater 8 before entering pre-distillation column 1. The operating parameters of each column are shown in Table 1 below:

[0047]

[0048] Table 1

[0049] In this embodiment, methanol with a concentration of ≥99.99% and an ethanol content of 10~100ppm can be extracted. The distillation process can be expanded by about 14%, while reducing steam consumption by 32.5%-33.7%. For new markets, the investment is small and the operation is highly feasible. By adopting energy-saving measures such as heat exchange network optimization and heat recovery, steam consumption is greatly reduced. The consumption per ton of methanol can be reduced to about 0.53 tons of steam / ton of refined methanol. Traditional processes can be transformed to achieve a significant reduction in energy consumption.

[0050] In summary, by adopting the above technical solutions, this application uses the steam heat from the top of the pre-distillation column to heat the reboiler 1 of the negative pressure column, and the steam heat from the top of the atmospheric pressure distillation column to heat the reboiler 2 of the negative pressure column, together meeting the energy requirements for distillation in the negative pressure distillation column; the energy of the methanol vapor from the top of the low-pressure distillation column heats the reboiler of the atmospheric pressure column and the reboiler 2 of the pre-distillation column, meeting the energy requirements for distillation in the atmospheric pressure distillation column and the pre-distillation column; the steam from the top of the high-pressure distillation column heats the reboiler of the low-pressure column, meeting the energy requirements for distillation in the low-pressure distillation column; by adjusting the coupling sequence, the five-column thermal coupling process of this application can reduce the steam consumption to 0.52-0.54 t steam / t refined methanol, with the highest steam consumption being 0.54 t steam / t refined methanol, less than 0.6 t steam / t refined methanol, further reducing the steam consumption; and it can ensure methanol concentration ≥99.99% and ethanol content between 10-100 ppm.

[0051] The devices and connections not specifically described above are all existing technologies, and will not be described in detail here.

[0052] The preferred embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, and these simple modifications all fall within the protection scope of this application.

[0053] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, the various possible combinations in this application will not be described separately.

[0054] Furthermore, various different implementations of this application can be combined in any way, as long as they do not violate the spirit of this application, and such combinations should also be regarded as the content disclosed in this application.

Claims

1. A five-tower multi-effect distillation unit for crude methanol, characterized in that, The system includes a pre-distillation column (1), a negative pressure distillation column (2), an atmospheric pressure distillation column (3), a low pressure distillation column (4), and a high pressure distillation column (5) connected in sequence. The lower part of the pre-distillation column (1) is provided with a first pre-distillation column reboiler (25) and a second pre-distillation column reboiler (26). The lower part of the negative pressure distillation column (2) is provided with a first negative pressure column reboiler (27) and a second negative pressure column reboiler (28). The lower parts of the atmospheric pressure distillation column (3), the low pressure distillation column (4), and the high pressure distillation column (5) are respectively provided with atmospheric pressure columns. Reboiler (29), low-pressure tower reboiler (30), high-pressure tower reboiler (31); wherein, the heat at the top of the pre-distillation tower (1) is used to heat the first reboiler of the negative pressure tower (27), the heat at the top of the atmospheric distillation tower (3) is used to heat the second reboiler of the negative pressure tower (28), the heat at the top of the low-pressure distillation tower (4) is used to heat the reboiler of the atmospheric distillation tower (29) and the second reboiler of the pre-distillation tower (26) respectively, and the heat at the top of the high-pressure distillation tower (5) is used to heat the reboiler of the low-pressure tower (30).

2. The crude methanol five-tower multi-effect distillation apparatus according to claim 1, characterized in that, The top of the pre-distillation column (1) is connected to the first reboiler of the negative pressure column (27) via the pre-distillation column top outlet pipeline (32). The top of the atmospheric distillation column (3) is connected to the second reboiler of the negative pressure column (28) via the atmospheric distillation column top outlet pipeline (33). The top of the low-pressure distillation column (4) is connected to the second reboiler of the pre-distillation column (26) and the atmospheric distillation column (29) via the low-pressure distillation column top outlet pipeline (34). The top of the high-pressure distillation column (5) is connected to the low-pressure distillation column (30) via the high-pressure distillation column top outlet pipeline (35).

3. The crude methanol five-tower multi-effect distillation apparatus according to claim 2, characterized in that, The output ends of the pre-tower reboiler (26) and the atmospheric pressure tower reboiler (29) are respectively connected to the low-pressure tower reflux tank (41). The bottom of the low-pressure tower reflux tank (41) is connected to the low-pressure distillation tower (4) through the low-pressure tower reflux pipeline (42). The low-pressure tower reflux pipeline (42) is connected to the low-pressure tower refined methanol collection pipeline (43).

4. The crude methanol five-tower multi-effect distillation apparatus according to claim 2, characterized in that, The output end of the reboiler 1 (27) of the negative pressure tower is connected to the pre-tower reflux tank (46). The bottom of the pre-tower reflux tank (46) is connected to the pre-distillation tower (1) through the pre-tower reflux pipeline (47). The top of the pre-tower reflux tank (46) is connected to the extraction tower (50) through the gas phase outlet pipeline (49). The gas phase outlet pipeline (49) is equipped with a pre-tower tail cooler (51). The top of the extraction tower (50) is connected to a non-condensable gas outlet pipeline (52). One side of the extraction tower (50) is connected to an extraction water pipeline (53). One side of the extraction tower (50) is connected to a miscellaneous oil outlet pipeline (54).

5. The crude methanol five-tower multi-effect distillation apparatus according to claim 2, characterized in that, The output end of the negative pressure tower reboiler two (28) is connected to the atmospheric pressure tower reflux tank (56). The bottom of the atmospheric pressure tower reflux tank (56) is connected to the atmospheric pressure distillation tower (3) through the atmospheric pressure tower reflux pipeline (57). The atmospheric pressure tower reflux pipeline (57) is connected to the atmospheric pressure tower refined methanol collection pipeline (59).

6. The crude methanol five-tower multi-effect distillation apparatus according to claim 2, characterized in that, The output end of the low-pressure tower reboiler (30) is connected to the high-pressure tower reflux tank (61). The bottom of the high-pressure tower reflux tank (61) is connected to the high-pressure distillation tower (5) through the high-pressure tower reflux pipeline (62). The high-pressure tower reflux pipeline (62) is connected to the high-pressure tower refined methanol collection pipeline (64).

7. The crude methanol five-tower multi-effect distillation apparatus according to claim 2, characterized in that, The top of the negative pressure distillation column (2) is connected to the negative pressure column reflux tank (66) via the negative pressure column top outlet pipeline (65). A negative pressure column condenser (67) is installed on the negative pressure column top outlet pipeline (65). The bottom of the negative pressure column reflux tank (66) is connected to the negative pressure distillation column (2) via the negative pressure column reflux pipeline (68). The negative pressure column reflux pipeline (68) is connected to the negative pressure column refined methanol outlet pipeline (70). The negative pressure column reflux tank (66) is connected to the buffer tank (72) via the reflux tank gas phase outlet pipeline (71). A negative pressure column tail cooler (73) is installed on the reflux tank gas phase outlet pipeline (71). The bottom of the buffer tank (72) is connected to the negative pressure column reflux tank (66) via the buffer tank bottom pipeline (74). A vacuum pipeline (75) is connected to the top of the buffer tank (72).

8. The crude methanol five-tower multi-effect distillation apparatus according to claim 1, characterized in that, The pre-distillation column (1) is connected to a feed line (6) on one side, and a pre-column preheater (7) and a pre-column preheater (8) are connected in parallel on the feed line (6).

9. A five-tower multi-effect distillation apparatus for crude methanol according to claim 8, characterized in that, The bottom of the high-pressure distillation column (5) is connected to a wastewater pipeline (22), which passes through the pre-tower preheater (8). A wastewater cooler (24) is installed on the wastewater pipeline (22) at the output end of the pre-tower preheater (8).

10. A five-tower multi-effect distillation apparatus for crude methanol according to any one of claims 3, 5, and 6, characterized in that, The refined methanol extracted from the atmospheric pressure tower refined methanol extraction pipeline (59), the low pressure tower refined methanol extraction pipeline (43), and the high pressure tower refined methanol extraction pipeline (64) provides heat to the preheater (7) of the preheater tower.

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