A complete cascade multi-effect rectification device for crude methanol

Abstract

The application provides a crude methanol complete cascade multi-effect rectification device, which comprises a pre-rectification tower, a negative pressure tower, a reduced pressure tower, an atmospheric pressure tower, a medium pressure tower, a pressurized tower and a high pressure tower which are connected in sequence, the top of the pre-rectification tower is connected with the atmospheric pressure tower reboiler, the top of the reduced pressure tower is connected with the negative pressure tower reboiler, the top of the atmospheric pressure tower is connected with the reduced pressure tower reboiler, the top of the medium pressure tower is connected with the pre-tower reboiler, the top of the pressurized tower is connected with the medium pressure tower reboiler, the top of the high pressure tower is connected with the pressurized tower reboiler, and seven-effect steam recycling is realized; the device completes heat closed loop transmission through six directional tower top pipelines, the tower kettle liquid and the condensate waste heat further preheat the feed or the upstream stream, the steam unit consumption can be reduced to 0.20-0.30 t / t rectified alcohol, the energy consumption is reduced by more than 40%, the device has the advantages of compact structure, stable operation and high efficiency of fusel side line separation, has economic and environmental protection values, and can reduce emissions.

Description

Technical Field

[0001] This application relates to the field of chemical technology, specifically to a crude methanol fully cascaded multi-effect distillation device. 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 uses the thermal coupling technology of pressurized tower and atmospheric tower to achieve energy saving of the distillation system, but there is still a lot of heat wasted in the system and the system energy consumption is still relatively high.

[0003] Existing methanol distillation processes typically employ a three-tower system: a pre-tower, a pressurized tower, and an atmospheric tower. The pressurized tower's overhead steam is used to heat the atmospheric tower, achieving energy savings. However, the atmospheric and pre-tower towers are cooled by circulating water, resulting in significant heat waste and high steam consumption per ton of methanol (approximately 1.2 t steam / t refined methanol). Given the increasingly stringent national carbon emission standards, a new technology is needed to recover heat from the existing system to achieve energy conservation and emission reduction goals.

[0004] Although many energy-saving distillation processes have been developed, including five-tower triple-effect, five-tower quadruple-effect, and six-tower multi-effect processes, the multiple distillation towers in these processes are not fully coupled in cascade, resulting in slightly poor controllability of process parameters during parallel operation. Therefore, there is room for further energy savings. For example, our company's application (application number 2024218492902) discloses a technical solution for a crude methanol six-tower eight-effect refining device, including a pre-distillation tower connected to a parallel atmospheric pressure distillation tower and a negative pressure distillation tower. The atmospheric pressure distillation tower and the negative pressure distillation tower are connected to a medium-pressure distillation tower, which is then sequentially connected to a pressurized distillation tower one and a pressurized distillation tower two. The pre-distillation tower is connected to the reboiler of the negative pressure tower via a pre-tower top outlet pipeline, and the atmospheric pressure distillation tower is connected to... The atmospheric distillation column's top outlet pipeline is connected to the second reboiler in the negative pressure column. The medium-pressure distillation column is connected to the pre-coiler via the top outlet pipeline of the medium-pressure column. The first pressurized distillation column is connected to the reboilers of the medium-pressure column and the second pressurized column via the top outlet pipelines of the first and second pressurized columns, respectively. The second pressurized distillation column is connected to the atmospheric distillation column's reboiler via the top outlet pipeline of the second pressurized column. This application employs a six-column thermal coupling system, optimizing the heat exchange network and increasing energy-saving potential. The unit consumption of methanol distillation can be reduced from 1.2 t steam / t refined methanol to 0.42-0.50 t steam / t refined methanol, significantly reducing operating costs and enhancing the company's competitiveness. Although the unit consumption of methanol distillation in the above application is low, the multiple distillation columns are not entirely coupled in a cascade manner, and there is still room for improvement in system efficiency.

[0005] Therefore, a new technical solution is needed to solve the above-mentioned technical problems. Utility Model Content

[0006] This application provides a complete cascade multi-effect distillation device for crude methanol, comprising a pre-distillation column, a negative pressure column, a reduced pressure column, an atmospheric pressure column, a medium pressure column, a pressurized column, and a high pressure column connected in sequence. The reboilers of the pre-distillation column, negative pressure column, reduced pressure column, atmospheric pressure column, medium pressure column, pressurized column, and high pressure column are respectively connected to a pre-distillation column reboiler, a negative pressure column reboiler, a reduced pressure column reboiler, an atmospheric pressure column reboiler, a medium pressure column reboiler, a pressurized column reboiler, and a high pressure column reboiler. The top of the distillation column is connected to the reboiler of the atmospheric distillation column via the top pipeline of the pre-distillation column; the top of the vacuum distillation column is connected to the reboiler of the negative pressure distillation column via the top pipeline of the vacuum distillation column; the top of the atmospheric distillation column is connected to the reboiler of the vacuum distillation column via the top pipeline of the atmospheric distillation column; the top of the medium-pressure distillation column is connected to the reboiler of the pre-distillation column via the top pipeline of the medium-pressure distillation column; the top of the pressurization column is connected to the reboiler of the medium-pressure distillation column via the top pipeline of the pressurization column; and the top of the high-pressure distillation column is connected to the reboiler of the pressurization column via the top pipeline of the high-pressure distillation column.

[0007] As a preferred embodiment, the top of the negative pressure tower is connected to the negative pressure tower reflux tank via a negative pressure tower top pipeline. A negative pressure tower condenser is installed on the negative pressure tower top pipeline. The pressure reducing tower is connected to the negative pressure tower condenser via a pressure reducing tower top pipeline. A negative pressure tower vacuum system is connected to the top of the negative pressure tower reflux tank. The bottom of the negative pressure tower reflux tank is connected to the upper middle part of the negative pressure tower via a negative pressure tower reflux pipeline. The bottom of the negative pressure tower reflux tank is also connected to the upper middle part of the pressure reducing tower via a negative pressure tower-pressure reducing tower reflux pipeline. The negative pressure tower reflux pipeline and the negative pressure tower-pressure reducing tower reflux pipeline are connected to the negative pressure tower refined methanol collection pipeline.

[0008] As a preferred embodiment, a vacuum column is provided between the pre-distillation column and the negative pressure column, the bottom of the vacuum column is connected to a vacuum column reboiler, and the top of the negative pressure column is connected to the vacuum column reboiler through a negative pressure column top pipeline.

[0009] As a preferred embodiment, the reboiler of the pre-distillation column is connected to the vacuum column via a pre-column reboiler pipeline, the reboiler of the vacuum column is connected to the negative pressure column via a vacuum column reboiler pipeline, the top of the negative pressure column is connected to the input end of the vacuum column reboiler via a negative pressure column top pipeline, the output end of the vacuum column reboiler is connected to the negative pressure column reflux tank, the top of the negative pressure column reflux tank is connected to the negative pressure column vacuum system, the bottom of the negative pressure column reflux tank is connected to the upper middle part of the negative pressure column via a negative pressure column reflux pipeline, a negative pressure column reflux pump is installed on the negative pressure column reflux pipeline, and the negative pressure column reflux pipeline is connected to the negative pressure column refined methanol collection pipeline.

[0010] As a preferred embodiment, the reboilers of the medium-pressure column, the pre-distillation column, the atmospheric column, the vacuum column, and the negative-pressure column are respectively equipped with a second reboiler for the medium-pressure column, the second reboiler for the pre-distillation column, the second reboiler for the atmospheric column, the second reboiler for the vacuum column, and the second reboiler for the negative-pressure column.

[0011] As a preferred embodiment, the output end of the atmospheric reboiler is connected to the extraction tank via a pre-tower reflux line one. A pre-tower condenser is installed on the pre-tower reflux line one. An extraction water line is connected to one side of the extraction tank, and a venting gas line is connected to the top of the extraction tank. The bottom of the extraction tank is connected to the upper part of the pre-distillation column via a pre-tower reflux line two, and a pre-tower reflux pump is installed on the pre-tower reflux line two.

[0012] As a preferred embodiment, the methanol extraction pipeline from the negative pressure tower is connected to the product methanol tank, and a methanol cooler for the negative pressure tower is installed on the methanol extraction pipeline from the negative pressure tower.

[0013] As a preferred embodiment, the output end of the negative pressure tower reboiler is connected to the pressure reducing tower reflux tank via a first pressure reducing tower reflux pipeline. The top of the pressure reducing tower reflux tank is connected to a pressure reducing tower vacuum system, and the bottom of the pressure reducing tower reflux tank is connected to the top of the pressure reducing tower via a second pressure reducing tower reflux pipeline. A pressure reducing tower reflux pump is installed on the second pressure reducing tower reflux pipeline, and the second pressure reducing tower reflux pipeline is connected to the pressure reducing tower refined methanol collection pipeline.

[0014] As a preferred embodiment, the purified methanol collection pipeline of the vacuum distillation tower is connected to the product methanol tank, and a purified methanol cooler of the vacuum distillation tower is installed on the purified methanol collection pipeline.

[0015] As a preferred embodiment, the output end of the vacuum distillation tower reboiler is connected to the atmospheric distillation tower reflux tank. The bottom of the atmospheric distillation tower reflux tank is connected to the upper part of the atmospheric distillation tower through the second atmospheric distillation tower reflux pipeline. An atmospheric distillation tower reflux pump is installed on the second atmospheric distillation tower reflux pipeline, and the second atmospheric distillation tower reflux pipeline is connected to the atmospheric distillation tower refined methanol collection pipeline.

[0016] As a preferred embodiment, the atmospheric pressure tower refined methanol outflow pipeline is connected to the product methanol tank, and an atmospheric pressure tower refined methanol cooler is installed on the atmospheric pressure tower refined methanol outflow pipeline.

[0017] As a preferred embodiment, the output end of the pre-tower reboiler is connected to the medium-pressure tower reflux tank via a medium-pressure tower reflux pipeline one. The bottom of the medium-pressure tower reflux tank is connected to the medium-pressure tower via a medium-pressure tower reflux pipeline two. A medium-pressure tower reflux pump is installed on the medium-pressure tower reflux pipeline two, and the medium-pressure tower reflux pipeline two is connected to the medium-pressure tower refined methanol collection pipeline.

[0018] As a preferred embodiment, the atmospheric pressure tower is connected to the medium pressure tower via an atmospheric pressure tower bottom pipeline. A medium pressure tower preheater is installed on the atmospheric pressure tower bottom pipeline, and the refined methanol collection pipeline of the medium pressure tower is connected to the input and output ends of the medium pressure tower preheater, respectively.

[0019] As a preferred embodiment, the medium-pressure tower refined methanol outflow pipeline is connected to the product methanol tank, and a medium-pressure tower refined methanol cooler is installed on the medium-pressure tower refined methanol outflow pipeline.

[0020] As a preferred embodiment, the output end of the medium-pressure tower reboiler is connected to the pressure tower reflux tank via a first pressure tower reflux pipeline. The bottom of the pressure tower reflux tank is connected to the pressure tower via a second pressure tower reflux pipeline. A pressure tower reflux pump is installed on the second pressure tower reflux pipeline, and the second pressure tower reflux pipeline is connected to the pressure tower refined methanol collection pipeline.

[0021] As a preferred embodiment, the medium-pressure tower is connected to the pressurized tower via a medium-pressure tower bottom pipeline, and a pressurized tower preheater is installed on the medium-pressure tower bottom pipeline; the pressurized tower refined methanol outlet pipeline is connected to the input and output ends of the pressurized tower preheater respectively.

[0022] As a preferred embodiment, the pressurized methanol extraction pipeline is connected to the product methanol tank, and a pressurized methanol cooler is installed on the pressurized methanol extraction pipeline.

[0023] As a preferred embodiment, the output end of the pressurized tower reboiler is connected to the high-pressure tower reflux tank via a high-pressure tower reflux pipeline one. The bottom of the high-pressure tower reflux tank is connected to the high-pressure tower via a high-pressure tower reflux pipeline two. A high-pressure tower reflux pump is installed on the high-pressure tower reflux pipeline two, and the high-pressure tower reflux pipeline two is connected to the high-pressure tower refined methanol collection pipeline.

[0024] As a preferred embodiment, the high-pressure tower refined methanol collection pipeline is connected to the product methanol tank, and a high-pressure tower refined methanol cooler is installed on the high-pressure tower refined methanol collection pipeline.

[0025] As a preferred embodiment, a feed pipeline is provided on one side of the pre-distillation column, and a pre-column preheater I and a pre-column preheater II are provided on the feed pipeline.

[0026] As a preferred embodiment, the pre-distillation column is connected to the negative pressure column via a pre-column bottom pipeline, and the pre-column bottom pipeline passes through a pre-column preheater.

[0027] As a preferred embodiment, the bottom of the pressurized tower is connected to the high-pressure tower via a pressurized tower bottom pipeline, and a high-pressure tower preheater 1, a high-pressure tower preheater 2, and a high-pressure tower preheater 3 are sequentially installed on the pressurized tower bottom pipeline.

[0028] As a preferred embodiment, the methanol extraction pipeline from the high-pressure tower passes through a high-pressure tower preheater.

[0029] As a preferred embodiment, the bottom of the high-pressure tower is equipped with a wastewater pipeline, which passes through the high-pressure tower preheater.

[0030] As a preferred embodiment, the input end of the high-pressure tower reboiler is connected to the steam pipeline, and the output end of the high-pressure tower reboiler is connected to the condensate pipeline.

[0031] As a preferred embodiment, the condensate pipeline passes sequentially through the high-pressure tower preheater three and the preheater two.

[0032] In this application, methanol vapor from the top of the high-pressure tower is used to heat the bottom of the pressurized tower, achieving thermal coupling; methanol vapor from the top of the pressurized tower is used to heat the bottom of the medium-pressure tower, achieving thermal coupling; methanol vapor from the top of the medium-pressure tower is used to heat the bottom of the pre-pressure tower, achieving thermal coupling; methanol vapor from the top of the pre-pressure tower is used to heat the bottom of the atmospheric tower, achieving thermal coupling; methanol vapor from the top of the atmospheric tower is used to heat the bottom of the vacuum tower, achieving thermal coupling; and methanol vapor from the top of the vacuum tower is used to heat the bottom of the negative-pressure tower, achieving thermal coupling. A closed-loop heat transfer is completed through six directional tower top pipelines. The waste heat from the bottom liquid and condensate further preheats the feed or upstream material, achieving seven-effect steam recycling and significant energy savings. Compared with traditional methanol processes, steam consumption can be reduced to 0.20-0.3. With 0t steam / t refined alcohol, energy consumption is reduced by more than 40%. It also has the advantages of compact structure, stable operation and high efficiency of side-stream separation of fusel alcohols, which has economic and environmental value and can reduce emissions. For the pre-distillation column, atmospheric column, vacuum column, and negative pressure column, where the bottom temperature is low and the heat source grade requirement is not high, the bottom of the column can be partially heated by external hot water, low-pressure steam or other low-grade heat sources. Furthermore, the top steam of the vacuum column can be switched to be connected to the top condenser of the negative pressure column. In the case of insufficient cold source, the negative pressure column can be cut off and shut down to carry out six-column operation. When the cold source is sufficient, a vacuum column can be set up before the pre-distillation column and the negative pressure column, and the top steam of the negative pressure column can be used to heat the reboiler of the vacuum column to realize eight-column series operation. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the six-tower and seven-tower structure of this application;

[0034] Figure 2 This is a schematic diagram of the eight-tower structure of this application;

[0035] 1. Pre-distillation column; 2. Negative pressure column; 3. Reduced pressure column; 4. Atmospheric pressure column; 5. Medium pressure column; 6. Pressurized column; 7. High pressure column; 8. Feed line; 9. Preheater 1 of the pre-distillation column; 10. Preheater 2 of the pre-distillation column; 11. Reboiler line of the pre-distillation column; 12. Reboiler line of the negative pressure column; 13. Reboiler line of the reduced pressure column; 14. Reboiler line of the atmospheric pressure column; 15. Preheater of the medium pressure column; 16. Reboiler line of the medium pressure column; 17. Preheater of the pressurized column; 18. Reboiler line of the pressurized column; 19. Preheater 1 of the high pressure column; 20. Preheater 2 of the high pressure column; 21. Preheater 3 of the high pressure column; 22. Side-collection line; 23. Wastewater line; 24. Reboiler of the pre-distillation column; 25. Reboiler of the negative pressure column; 26. Reboiler of the reduced pressure column; 27. Reboiler of the atmospheric pressure column; 28. Reboiler of the medium pressure column. Equipment; 29. ​​Pressurized tower reboiler; 30. High-pressure tower reboiler; 31. Pre-tower top pipeline; 32. Reduced pressure tower top pipeline; 33. Atmospheric pressure tower top pipeline; 34. Medium-pressure tower top pipeline; 35. Pressurized tower top pipeline; 36. High-pressure tower top pipeline; 37. Steam pipeline; 38. Condensate pipeline; 39. Pre-tower reflux pipeline one; 40. Extraction tank; 41. Pre-tower condenser; 42. Extraction water pipeline; 43. Purge gas pipeline; 44. Pre-tower reflux pipeline two; 45. Pre-tower reflux pump; 46. Negative pressure tower top pipeline; 47. Negative pressure tower reflux tank; 48. Negative pressure tower condenser; 49. Negative pressure tower vacuum system; 50. Negative pressure tower reflux pipeline; 51. Negative pressure tower reflux pump; 52. Negative pressure tower refined methanol collection pipeline; 53. Product 54. Methanol Tank; 55. Negative Pressure Tower Refined Methanol Cooler; 56. Pressure Reducing Tower Reflux Line 1; 57. Pressure Reducing Tower Reflux Tank; 58. Pressure Reducing Tower Vacuum System; 59. Pressure Reducing Tower Reflux Line 2; 60. Pressure Reducing Tower Reflux Pump; 61. Pressure Reducing Tower Refined Methanol Outlet Pipeline; 62. Pressure Reducing Tower Refined Methanol Cooler; 63. Atmospheric Pressure Tower Reflux Line 1; 64. Atmospheric Pressure Tower Reflux Tank; 65. Atmospheric Pressure Tower Reflux Pump; 66. Atmospheric Pressure Tower Refined Methanol Outlet Pipeline; 67. Atmospheric Pressure Tower Refined Methanol Cooler; 68. Medium Pressure Tower Reflux Line 1; 69. Medium Pressure Tower Reflux Tank; 70. Medium Pressure Tower Reflux Line 2; 71. Medium Pressure Tower Reflux Pump; 72. Medium Pressure Tower Refined Methanol Outlet Pipeline; 73. Medium Pressure Tower Refined Methanol Cooler; 74. Pressurized Tower Reflux Pipeline Line 1; 75. Pressurized Tower Reflux Tank; 76. Pressurized Tower Reflux Line 2; 77. Pressurized Tower Reflux Pump; 78. Pressurized Tower Refined Methanol Outlet Pipeline; 79. Pressurized Tower Refined Methanol Cooler; 80. High-Pressure Tower Reflux Line 1; 81. High-Pressure Tower Reflux Tank; 82. High-Pressure Tower Reflux Line 2; 83. High-Pressure Tower Reflux Pump; 84. High-Pressure Tower Refined Methanol Outlet Pipeline; 85. High-Pressure Tower Refined Methanol Cooler; 86. Pre-Tower Second Reboiler; 87. Vacuum Tower; 88. Vacuum Tower Bottom Pipeline; 89. Vacuum Tower Reboiler; 90. Vacuum Tower Top Outlet Pipeline; 91. Vacuum Tower Reflux Tank; 92. Vacuum Tower Condenser; 93. Vacuum Tower Vacuum System; 94. Vacuum Tower Reflux Pipeline; 95. Vacuum Tower Reflux Pump; 96. Vacuum Tower Refined Methanol Outlet Pipeline;97. Negative pressure tower methanol cooler; 98. Vacuum tower second reboiler; 99. Negative pressure tower-reduced pressure tower reflux pipeline; 100. Negative pressure tower second reboiler; 101. Reduced pressure tower second reboiler; 102. Atmospheric pressure tower second reboiler; 103. Medium pressure tower second reboiler. Detailed Implementation

[0036] The following is in conjunction with the appendix Figure 1 , Figure 2 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.

[0037] Example 1:

[0038] This embodiment provides a complete cascade multi-effect distillation device for crude methanol, comprising a pre-distillation column 1, a negative pressure column (negative pressure distillation column) 2, a reduced pressure column (reduced pressure distillation column) 3, an atmospheric pressure column (atmospheric pressure distillation column) 4, a medium pressure column (medium pressure distillation column) 5, a pressurized column (pressurized distillation column) 6, and a high pressure column (high pressure distillation column) 7 connected in sequence. Preferably, the top pressure of the pre-distillation column 1 is 120 kPa-180 kPa, the top pressure of the negative pressure column 2 is 20 kPa-60 kPa, the top pressure of the reduced pressure column 3 is 50 kPa-90 kPa, the top pressure of the atmospheric pressure column 4 is 90 kPa-140 kPa, the top pressure of the medium pressure column 5 is 200 kPa-450 kPa, the top pressure of the pressurized column 6 is 400 kPa-700 kPa, and the top pressure of the high pressure column 7 is 600 kPa-1200 kPa.

[0039] A feed line 8 is provided on one side of the pre-distillation column 1. A pre-column preheater 9 and a pre-column preheater 10 are sequentially installed on the feed line 8 to preheat the crude methanol material entering the pre-distillation column 1 and improve the stability of distillation. Preferably, an ambient temperature negative pressure flash tank is provided before the preheater 9 to flash out a portion of the CO2 in the crude methanol, which is beneficial for coupling the top gas of the pre-distillation column 1 to the atmospheric pressure column 4.

[0040] The bottom of the pre-distillation column 1 is connected to the negative pressure column 2 via the pre-column reboiler pipeline 11, and to the vacuum column 3 via the pre-column reboiler pipeline 11 and the negative pressure column reboiler pipeline 12. Corresponding valves are installed on the pre-column reboiler pipeline 11 and the negative pressure column reboiler pipeline 12 to control the flow of liquid from the reboiler of the pre-distillation column 1 into the negative pressure column 2 or the vacuum column 3. The pre-column reboiler pipeline 11 passes through the pre-column preheater 9, meaning that the pre-column reboiler pipeline 11 is connected to both the input and output ends of the pre-column preheater 9. The heat from the reboiler of the pre-distillation column 1 heats the pre-column preheater 9. Heating; the bottom of the negative pressure tower 2 is connected to the pressure reducing tower 3 via the negative pressure tower bottom pipeline 12, the bottom of the pressure reducing tower 3 is connected to the atmospheric pressure tower 4 via the pressure reducing tower bottom pipeline 13, and the bottom of the atmospheric pressure tower 4 is connected to the medium pressure tower 5 via the atmospheric pressure tower bottom pipeline 14. Preferably, a medium pressure tower preheater 15 is installed on the atmospheric pressure tower bottom pipeline 14, and the material in the bottom of the atmospheric pressure tower 4 enters the medium pressure tower 5 after being preheated by the medium pressure tower preheater 15; the bottom of the medium pressure tower 5 is connected to the pressurized tower 6 via the medium pressure tower bottom pipeline 16. Preferably, the medium pressure tower... A pressure tower preheater 17 is installed on the bottom pipeline 16. The material in the bottom of the medium-pressure tower 5 is preheated by the pressure tower preheater 17 before entering the pressure tower 6. The bottom of the pressure tower 6 is connected to the high-pressure tower 7 via a pressure tower bottom pipeline 18. Preferably, a high-pressure tower preheater 19, a high-pressure tower preheater 20, and a high-pressure tower preheater 3 21 are sequentially installed on the pressure tower bottom pipeline 18. The material in the bottom of the pressure tower 6 is heated sequentially by the high-pressure tower preheater 19, the high-pressure tower preheater 20, and the high-pressure tower preheater 3 21 before entering the high-pressure tower 7. A side-collection pipeline 22 is installed on one side of the high-pressure tower 7 for collecting fusel oil. The control target for the side-collection pipeline 22 is to achieve a high compliance rate of ethanol at the top of the high-pressure tower 7 and to control the methanol content in the side-collection to below 20%. A wastewater pipeline 23 is installed at the bottom of the high-pressure tower 7 for collecting wastewater. The wastewater pipeline 23 passes through the high-pressure tower preheater 20, that is, the wastewater pipeline 23 is connected to the input and output ends of the high-pressure tower preheater 20. The wastewater collected from the bottom of the high-pressure tower 7 is used to heat the high-pressure tower preheater 20, and is collected as wastewater after heat exchange.

[0041] The reboilers of the pre-distillation column 1, negative pressure column 2, vacuum column 3, atmospheric pressure column 4, medium pressure column 5, pressurized column 6, and high pressure column 7 are respectively connected to the reboilers 24, 25, 26, 27, 28, 29, and 30 of the pre-distillation column, negative pressure column, vacuum column, atmospheric pressure column, medium pressure column, pressurized column, and high pressure column. The vapor phase at the top of each column, flowing counter-currently, provides heat to the reboiler of the next low-pressure column, forming a fully cascaded seven-effect thermal coupling. Specifically, the vapor at the top of the pre-distillation column 1 heats the reboiler 27 of the atmospheric pressure column, meaning the vapor at the top of the pre-distillation column 1 heats the reboiler 27 of the atmospheric pressure column. Thermal coupling is achieved through reboiler heating; the top steam of vacuum distillation column 3 heats the reboiler 25 of the negative pressure column, meaning the methanol vapor at the top of vacuum distillation column 3 heats the reboiler of negative pressure column 2, achieving thermal coupling; the top steam of atmospheric distillation column 4 heats the reboiler 26 of vacuum distillation column, meaning the methanol vapor at the top of atmospheric distillation column 4 heats the reboiler of vacuum distillation column 3, achieving thermal coupling; the top steam of medium-pressure distillation column 5 heats the reboiler 24 of the pre-distillation column, meaning the methanol vapor at the top of medium-pressure distillation column 5 heats the reboiler of pre-rectification column 1, achieving thermal coupling; the top steam of pressurized distillation column 6 heats the reboiler 28 of medium-pressure distillation column, meaning the methanol vapor at the top of pressurized distillation column 6 heats the reboiler of medium-pressure distillation column 28, achieving thermal coupling. 5. Heating the reboiler of column 5 achieves thermal coupling; the top steam of high-pressure column 7 supplies heat to the reboiler 29 of pressurized column 6, that is, the methanol vapor at the top of high-pressure column 7 heats the reboiler of pressurized column 6, achieving thermal coupling; more specifically: the top of the pre-distillation column 1 is connected to the reboiler 27 of atmospheric column 4 through the pre-column top pipeline 31, providing the heat required for distillation in atmospheric column 4; the top of the vacuum column 3 is connected to the reboiler 25 of negative pressure column 2 through the vacuum column top pipeline 32, providing the heat required for distillation in negative pressure column 2; the top of the vacuum column 3 is also connected to the negative pressure column condenser 48 at the top of negative pressure column 2 through the vacuum column top pipeline 32; The top of pressure column 4 is connected to the reboiler 26 of vacuum column 3 via atmospheric column top pipeline 33, providing the heat required for distillation in vacuum column 3; the top of medium-pressure column 5 is connected to the reboiler 24 of pre-distillation column 1 via medium-pressure column top pipeline 34, providing the heat required for distillation in pre-distillation column 1; the top of pressure column 6 is connected to the reboiler 28 of medium-pressure column 5 via pressure column top pipeline 35, providing the heat required for distillation in medium-pressure column 5; the top of high-pressure column 7 is connected to the reboiler 29 of pressure column 6 via high-pressure column top pipeline 36, providing the heat required for distillation in pressure column 6; Table 1 below shows the energy-material coupling network between the columns.

[0042]

[0043] Table 1. Energy-material coupling network between towers

[0044] The aforementioned high-pressure tower reboiler 30 is heated by steam. Specifically, the input end of the high-pressure tower reboiler 30 is connected to the steam pipeline 37, and the output end of the high-pressure tower reboiler 30 is connected to the condensate pipeline 38. In order to further improve the utilization rate of steam, the condensate pipeline 38 passes through the high-pressure tower preheater 31 and the preheater 20 in sequence. That is, the condensate pipeline 38 is connected to the input and output ends of the high-pressure tower preheater 31 and the preheater 20 in the preheater. After the steam condensate provides heat to the high-pressure tower preheater 31 and the preheater 20 in the preheater, it is collected as condensate.

[0045] More specifically: the pressure gradient in this embodiment is as follows: pre-distillation column 1 (170 / 180) — negative pressure column 2 (40 / 50) — reduced pressure column 3 (70 / 75) — atmospheric pressure column 4 (115 / 121) — medium pressure column 5 (300 / 340) — pressurized column 6 (550 / 570) — high pressure column 7 (1050 / 1076); the aforementioned pre-distillation column 1 (170 / 180) refers to the operating pressure range of pre-distillation column 1 being 170kPa—180kPa, and so on, which will not be elaborated here. The temperature coupling relationship is as follows: high-pressure tower 7 (139 / 182) — pressurized tower 6 (115 / 132) — medium-pressure tower 5 (95 / 109) — pre-distillation tower 1 (81 / 83) — atmospheric tower 4 (68 / 76) — vacuum tower 3 (55 / 63) — negative-pressure tower 2 (43 / 50); the above high-pressure tower 7 (139 / 182) refers to the operating temperature range of the high-pressure tower being 139℃—182℃, and so on. It will not be elaborated here. The above gradient can ensure that the high-temperature tower top steam can drive the low-temperature tower bottom heat transfer.

[0046] The gas phase pipelines between each tower are independent of each other, and the transport of the liquid phase in the tower bottom relies on pumps. The pressure of each tower is determined by the temperature of the heating and cooling medium in each tower and the heat exchange effect of the coupled reboiler. By rationally designing the reboiler and adjusting the effective heating area during operation, the pressure difference between each tower can be effectively controlled. The above content belongs to conventional existing technology and will not be elaborated in detail by the applicant. For negative pressure tower 2 and pressure reducing tower 3, vacuum systems 49 and 57 are used to evacuate negative pressure tower 2 and pressure reducing tower 3 respectively to maintain them in a low-pressure state and form a stable pressure difference with the upstream tower.

[0047] Vacuum level affects the heat transfer temperature difference; therefore, heat exchanger efficiency, ambient temperature, and humidity all affect the vacuum level of negative pressure tower 2 and pressure reducing tower 3. The specific pressure control schemes for negative pressure tower 2 and pressure reducing tower 3 are as follows:

[0048] Level 1 control: When the pressure of pressure reducing tower 3 and / or negative pressure tower 2 increases, it is necessary to adjust the variable frequency fan of the pressure reducing tower condenser in vacuum system 57 and / or the variable frequency fan of the negative pressure tower condenser in vacuum system 49, and monitor and adjust the inlet and outlet temperatures of circulating water.

[0049] Secondary control mode: When primary control is insufficient to maintain pressure, secondary control mode is activated. In summer, air cooling is difficult to control and water spraying is required. The air cooler then switches to wet evaporative cooling mode.

[0050] Three-level control mode: If the pressure inside the tower still rises after the first and second level control, multiple vacuum pumps need to be operated in parallel to increase the pumping capacity of the vacuum pumps in order to maintain the vacuum level of negative pressure tower 2 and pressure reducing tower 3.

[0051] Level 4 control mode: Add a heat exchanger with chilled water as the condensing medium before the vacuum pump to condense the steam that the circulating water cannot condense, reduce the amount of gas entering the vacuum pump, and improve the effective pumping efficiency of the vacuum pump.

[0052] This embodiment utilizes the principle of multi-effect distillation. By adjusting the operating pressure of each column, a temperature gradient is created, using the top steam of the higher-temperature distillation column as a heat source for the bottom of the lower-temperature distillation column. This achieves multiple energy couplings, significantly reducing the system's steam energy consumption. It enables complete cascade coupling of multiple columns, increasing steam utilization efficiency and resulting in greater energy saving and carbon reduction benefits. In this embodiment, the unit consumption of methanol distillation can be reduced from 1.2t steam / t methanol to 0.20-0.30t steam / t methanol, achieving energy savings of over 70% compared to the traditional dual-tower thermal coupling process. This significantly reduces operating costs for enterprises, substantially lowers carbon emissions, and enhances their competitiveness.

[0053] Example 2:

[0054] The difference between this embodiment and Embodiment 1 is that a vacuum column 87 is installed between the pre-distillation column 1 and the negative pressure column 2. The reboiler of the pre-distillation column 1 is connected to the vacuum column 87 via a pre-column reboiler pipeline 11, which passes through a pre-column preheater 9. The reboiler of the vacuum column 87 is connected to the negative pressure column 2 via a vacuum column reboiler pipeline 88. A vacuum column reboiler 89 is installed at the bottom of the vacuum column 87, and the top of the vacuum column 87 is connected to a vacuum column reflux tank 91 via a vacuum column top outlet pipeline 90. A vacuum tower condenser 92 is installed on the outlet pipeline 90. A vacuum tower vacuum system 93 is installed at the top of the vacuum tower reflux tank 91. The bottom of the vacuum tower reflux tank 91 is connected to a vacuum tower reflux pipeline 94. A vacuum tower reflux pump 95 is installed on the vacuum tower reflux pipeline 94. The vacuum tower reflux pipeline 94 is also connected to the vacuum tower refined methanol outlet pipeline 96. The top of the negative pressure tower 2 is connected to the vacuum tower reboiler 89 through the negative pressure tower top pipeline 46. The output end of the vacuum tower reboiler 89 is connected to the negative pressure tower reflux tank 47.

[0055] Preferably, the vacuum tower refined methanol collection pipeline 96 is connected to the product methanol tank 53, and a negative pressure tower refined methanol cooler 97 is installed on the vacuum tower refined methanol collection pipeline 96; the collected refined methanol is stored in the product methanol tank 53 after being cooled by the vacuum tower refined methanol cooler 97; in this embodiment, the top steam of the negative pressure tower 2 is used to heat the vacuum tower reboiler 89, realizing the series operation of eight towers.

[0056] Preferably, the vacuum tower 87 can be equipped with a second reboiler 98 according to the actual coupling situation and on-site heat source conditions, so as to use external low-temperature waste heat for partial heating, thereby further reducing steam consumption while maintaining product quality.

[0057] Example 3:

[0058] In this embodiment, based on Example 1, the reflux and / or refined methanol production of each tower are specifically described, specifically:

[0059] The output of the atmospheric reboiler 27 is connected to the extraction tank 40 via a pre-recirculation line 39. A pre-recirculation condenser 41 is installed on the pre-recirculation line 39. An extraction water line 42 is connected to one side of the extraction tank 40, and a purge gas line 43 is connected to the top of the extraction tank 40. The bottom of the extraction tank 40 is connected to the upper part of the pre-distillation column 1 via a second pre-recirculation line 44. A pre-recirculation pump 45 is installed on the second pre-recirculation line 44. The steam at the top of the pre-distillation column 1 provides heat to the atmospheric reboiler 27, thereby providing the energy required for distillation in the atmospheric column 4. After heat exchange, the material enters the extraction tank 40 for extraction. After extraction, the liquid phase is refluxed back to the pre-distillation column 1 for further distillation, while the gas phase is released through the purge gas line. 43. Extraction; the above is used for impurity removal and gas emission, realizing stable operation and efficient energy consumption control of the process flow; the top of the negative pressure tower 2 is connected to the negative pressure tower reflux tank 47 through the negative pressure tower top pipeline 46, and a negative pressure tower condenser 48 is installed on the negative pressure tower top pipeline 46; the pressure reducing tower 3 is connected to the negative pressure tower condenser 48 through the pressure reducing tower top pipeline 32; the top of the negative pressure tower reflux tank 47 is connected to the negative pressure tower vacuum system 49, which can adopt the existing chemical vacuum system, and this application does not make any improvement to it; the negative pressure tower vacuum system 49 maintains low-pressure operating conditions, which can ensure that the negative pressure tower 2 operates in a vacuum environment, because the negative pressure tower reflux tank 47 and the negative pressure tower 2 gas The negative pressure tower reflux tank 47 is also under negative pressure because they are interconnected. The bottom of the negative pressure tower reflux tank 47 is connected to the upper middle part of the negative pressure tower 2 via a negative pressure tower reflux pipeline 50. A negative pressure tower reflux pump 51 is installed on the negative pressure tower reflux pipeline 50. The bottom of the negative pressure tower reflux tank 47 is also connected to the pressure reducing tower 3 via a negative pressure tower-pressure reducing tower reflux pipeline 99. A negative pressure tower-pressure reducing tower reflux pump is installed on the negative pressure tower-pressure reducing tower reflux pipeline 99. The negative pressure tower reflux pipeline 50 and the negative pressure tower-pressure reducing tower reflux pipeline 99 are connected to the negative pressure tower refined methanol extraction pipeline 52. As is well known, corresponding valves are installed on the negative pressure tower reflux pipeline 50 and the negative pressure tower-pressure reducing tower reflux pipeline 99 respectively. When the negative pressure tower 2 participates in operation... During operation, the reflux is controlled to flow back to the negative pressure tower 2. When the negative pressure tower 2 is not in operation, the reflux is controlled to flow back to the pressure reducing tower 3. Preferably, the methanol extraction pipeline 52 of the negative pressure tower is connected to the product methanol tank 53, and a methanol cooler 54 of the negative pressure tower is installed on the methanol extraction pipeline 52. When the negative pressure tower 2 is in operation, the vapor at the top of the negative pressure tower 2 is condensed by the negative pressure tower condenser 48 and then enters the negative pressure tower reflux tank 47, keeping the negative pressure tower reflux tank 47 in a vacuum state. Part of the liquid phase in the negative pressure tower reflux tank 47 is extracted as methanol, and part of it is returned to the negative pressure tower 2 for further distillation, thereby improving the accuracy of distillation. Preferably, the extracted methanol is cooled by the methanol cooler 54 of the negative pressure tower and then stored in the product methanol tank 53.When the cold source for the negative pressure tower condenser 48 is insufficient, the negative pressure tower 2 does not operate, and the vapor phase at the top of the pressure reducing tower 3 directly enters the negative pressure tower condenser 48. After being condensed by the negative pressure tower condenser 48, it enters the negative pressure tower reflux tank 47, which is kept under vacuum. Part of the liquid phase in the negative pressure tower reflux tank 47 is collected as refined methanol, and part is returned to the pressure reducing tower 3 for further distillation.

[0060] The output end of the reboiler 25 of the negative pressure tower is connected to the reflux tank 56 of the pressure reducing tower via a first reflux pipeline 55. A vacuum system 57 is connected to the top of the reflux tank 56, maintaining low-pressure operating conditions to ensure that the pressure reducing tower 3 operates in a vacuum environment. Because the reflux tank 56 is connected to the pressure reducing tower 3, it is also under negative pressure. The bottom of the reflux tank 56 is connected to the top of the pressure reducing tower 3 via a second reflux pipeline 58. A reflux pump 59 is installed on the second reflux pipeline 58. The second reflux pipeline 58 is connected to the refined methanol collection pipeline 60 of the pressure reducing tower. Connection; Preferably, the methanol collection pipeline 60 of the vacuum tower is connected to the product methanol tank 53, and a methanol cooler 61 of the vacuum tower is installed on the methanol collection pipeline 60; the steam at the top of the vacuum tower 3 provides heat to the reboiler 25 of the negative pressure tower, thereby providing the energy required for distillation of the negative pressure tower 2. The material after heat exchange enters the reflux tank 56 of the vacuum tower. The reflux tank 56 of the vacuum tower maintains a vacuum state. Part of the liquid phase in the reflux tank 56 is collected as methanol, and part of it is returned to the vacuum tower 3 for further distillation to improve the accuracy of distillation; preferably, the collected methanol is stored in the product methanol tank 53 after being cooled by the methanol cooler 61 of the vacuum tower.

[0061] The output end of the vacuum distillation reboiler 26 is connected to the atmospheric distillation reflux tank 63 via atmospheric distillation reflux pipeline 62. The bottom of the atmospheric distillation reflux tank 63 is connected to the upper part of the atmospheric distillation tower 4 via atmospheric distillation reflux pipeline 64. An atmospheric distillation reflux pump 65 is installed on atmospheric distillation reflux pipeline 64. Atmospheric distillation reflux pipeline 64 is connected to the atmospheric distillation refined methanol collection pipeline 66. Preferably, the atmospheric distillation refined methanol collection pipeline 66 is connected to the product methanol tank 53. An atmospheric pressure column methanol cooler 67 is installed on the outgoing pipeline 66; the steam at the top of the atmospheric pressure column 4 provides heat to the reboiler 26 of the vacuum column, and in turn provides the energy required for the distillation of the vacuum column 3. The material after heat exchange enters the atmospheric pressure column reflux tank 63. Part of the liquid phase in the atmospheric pressure column reflux tank 63 is taken out as refined methanol, and part of it is returned to the atmospheric pressure column 4 for further distillation to improve the accuracy of distillation. Preferably, the refined methanol is stored in the product methanol tank 53 after being cooled by the atmospheric pressure column methanol cooler 67.

[0062] The output of the pre-reboiler 24 is connected to the intermediate-pressure tower reflux tank 69 via intermediate-pressure tower reflux pipeline 68. The bottom of the intermediate-pressure tower reflux tank 69 is connected to the intermediate-pressure tower 5 via intermediate-pressure tower reflux pipeline 70. An intermediate-pressure tower reflux pump 71 is installed on the intermediate-pressure tower reflux pipeline 70. The intermediate-pressure tower reflux pipeline 70 is also connected to the intermediate-pressure tower refined methanol outlet pipeline 72. Preferably, the intermediate-pressure tower refined methanol outlet pipeline 72 is connected to the product methanol tank 53, and an intermediate-pressure tower refined methanol cooler 73 is installed on the intermediate-pressure tower refined methanol outlet pipeline 72. The steam at the top of the intermediate-pressure tower 5 is from the pre-reboiler 24. The heat is provided to supply the energy required for distillation in the pre-distillation column 1. After heat exchange, the material enters the medium-pressure column reflux tank 69. Part of the liquid phase in the medium-pressure column reflux tank 69 is collected as refined methanol, and part of it is returned to the medium-pressure column 5 for further distillation to improve the accuracy of distillation. The collected refined methanol is cooled by the medium-pressure column refined methanol cooler 73 and then stored in the product methanol tank 53. Preferably, the medium-pressure column refined methanol collection pipeline 72 passes through the medium-pressure column preheater 15 and exchanges heat with the feed of the medium-pressure column. Specifically, the medium-pressure column refined methanol collection pipeline 72 is connected to the input end and the output end of the medium-pressure column preheater 15 respectively.

[0063] The output end of the intermediate-pressure tower reboiler 28 is connected to the pressure tower reflux tank 75 via a first pressure tower reflux pipeline 74. The bottom of the pressure tower reflux tank 75 is connected to the pressure tower 6 via a second pressure tower reflux pipeline 76. A pressure tower reflux pump 77 is installed on the second pressure tower reflux pipeline 76, which is also connected to the pressure tower refined methanol outlet pipeline 78. Preferably, the pressure tower refined methanol outlet pipeline 78 is connected to the product methanol tank 53, and a pressure tower refined methanol cooler 79 is installed on the pressure tower refined methanol outlet pipeline 78. Preferably, the pressure tower refined methanol outlet pipeline 78 passes through the pressure tower preheater 17, i.e., the pressure tower refined methanol outlet pipeline 78 is connected to both the input and output ends of the pressure tower preheater 17. The refined methanol produced heats the preheater 17 of the pressurized tower and is collected after heat exchange. The steam at the top of the pressurized tower 6 provides heat to the reboiler 28 of the medium-pressure tower, which in turn provides the energy required for distillation in the medium-pressure tower 5. The material after heat exchange enters the reflux tank 75 of the pressurized tower. Part of the liquid phase in the reflux tank 75 is collected as refined methanol, and part of it is returned to the pressurized tower 6 for further distillation to improve the accuracy of distillation. Preferably, the collected refined methanol is cooled by the pressurized tower refined methanol cooler 79 and then stored in the product methanol tank 53. Preferably, the pressurized tower refined methanol collection pipeline 78 passes through the pressurized tower preheater 17 and undergoes heat exchange. Specifically, the pressurized tower refined methanol collection pipeline 78 is connected to the input and output ends of the pressurized tower preheater 17 respectively.

[0064] The output end of the pressurized tower reboiler 29 is connected to the high-pressure tower reflux tank 81 via a first high-pressure tower reflux pipeline 80. The bottom of the high-pressure tower reflux tank 81 is connected to the high-pressure tower 7 via a second high-pressure tower reflux pipeline 82. A high-pressure tower reflux pump 83 is installed on the second high-pressure tower reflux pipeline 82, which is also connected to the high-pressure tower refined methanol outlet pipeline 84. Preferably, the high-pressure tower refined methanol outlet pipeline 84 is connected to the product methanol tank 53, and a high-pressure tower refined methanol cooler 85 is installed on the high-pressure tower refined methanol outlet pipeline 84. The steam at the top of the high-pressure tower 7 provides heat to the pressurized tower reboiler 29, thereby... To provide the energy required for distillation to the pressurized tower 6, the material after heat exchange enters the high-pressure tower reflux tank 81. Part of the liquid phase in the high-pressure tower reflux tank 81 is collected as refined methanol, and part is returned to the high-pressure tower 7 for further distillation to improve the accuracy of distillation. Preferably, the collected refined methanol is cooled by the high-pressure tower refined methanol cooler 85 and then stored in the product methanol tank 53. More preferably, the high-pressure tower refined methanol collection pipeline 84 passes through the high-pressure tower preheater 19, that is, the high-pressure tower refined methanol collection pipeline 84 is connected to the input and output ends of the high-pressure tower preheater 19, and the collected refined methanol heats the high-pressure tower preheater 19 and is collected after heat exchange.

[0065] Example 4:

[0066] This embodiment provides a specific application scenario:

[0067] This embodiment provides a specific application, taking the seven-tower system of Example 3 as an example. The crude methanol feed rate is 44,000 kg / h, with a water content of 6.56% and an ethanol content of approximately 600 ppm. Through this application, the steam energy consumption for refining methanol is approximately 0.2492 tons of steam / refined methanol, where the methanol purity can reach over 99.99% and the ethanol content is less than 100 ppm. The operating parameters of each tower are shown in Table 2 below:

[0068]

[0069] The crude methanol fully cascaded multi-effect distillation apparatus provided by this utility model is sequentially connected to a pre-distillation column 1, a negative pressure column 2, a reduced pressure column 3, an atmospheric pressure column 4, a medium pressure column 5, a pressurized column 6, and a high pressure column 7. The feed enters the system through the feed pipeline 8. Each column bottom is respectively equipped with a pre-column reboiler 24, a negative pressure column reboiler 25, a reduced pressure column reboiler 26, an atmospheric pressure column reboiler 27, a medium pressure column reboiler 28, a pressurized column reboiler 29, and a high pressure column reboiler 30.

[0070] The preheating tower bottom pipeline 11, negative pressure tower bottom pipeline 12, pressure reducing tower bottom pipeline 13, atmospheric pressure tower bottom pipeline 14, medium pressure tower bottom pipeline 16, pressurized tower bottom pipeline 18, preheating tower preheater 19, preheating tower preheater 20, medium pressure tower preheater 15, pressurized tower preheater 17, high pressure tower preheater 19, high pressure tower preheater 20, and high pressure tower preheater 3 21 are connected. The bottom pipelines of each of the above towers are connected to the corresponding preheaters to form a complete preheating and reboiling circulation loop. The material discharge and intermediate extraction are realized through wastewater pipeline 23 and side extraction pipeline 22.

[0071] In the thermal coupling layout, the top vapor phases of the pre-distillation column 1, the vacuum column 3, the atmospheric column 4, the medium-pressure column 5, the pressurized column 6, and the high-pressure column 7 are sequentially connected to the reboiler 27 of the atmospheric column, the reboiler 25 of the vacuum column, the reboiler 26 of the vacuum column, the reboiler 24 of the pre-distillation column, the reboiler 28 of the medium-pressure column, and the reboiler 29 of the pressurized column via the top pipeline 31 of the pre-distillation column, the top pipeline 32 of the vacuum column, the top pipeline 33 of the atmospheric column, the top pipeline 34 of the medium-pressure column, the top pipeline 35 of the pressurized column, and the top pipeline 36 of the high-pressure column, forming a completely cascaded multi-effect thermal coupling system. The high-pressure column reboiler 30 is heated by medium-pressure steam transported by the steam pipeline 37. The steam condensate is discharged after exchanging heat with the high-pressure column preheater 31 and the pre-distillation column preheater 20 via the condensate pipeline 38, thereby improving the thermal energy utilization efficiency and reducing the steam consumption per unit.

[0072] In addition, the reboilers of pre-distillation column 1, negative pressure column 2, vacuum column 3, atmospheric pressure column 4, and medium pressure column 5 can be equipped with second reboilers according to the actual coupling situation and on-site heat source conditions, utilizing external low-temperature waste heat for partial heating, thereby further reducing steam consumption while maintaining product quality; specifically, when the low-temperature heat source at the distillation site exceeds 60°C, a second reboiler 100 is installed in the reboiler of negative pressure column 2, and the low-temperature heat source is used to heat the second reboiler 100; the low-temperature heat source includes, but is not limited to, excess low-temperature heat sources such as steam condensate and syngas; at the distillation site When the low-temperature heat source exceeds 70℃, a second reboiler 101 for the vacuum distillation tower 3 and a second reboiler 100 for the negative pressure tower 2 are respectively installed in the reboiler of the vacuum distillation tower 3 and the negative pressure tower 2. The low-temperature heat source sequentially heats the second reboiler 101 for the vacuum distillation tower and the second reboiler 100 for the negative pressure tower. When the low-temperature heat source at the distillation site exceeds 80℃, a second reboiler 102 for the atmospheric distillation tower 4, a second reboiler 101 for the vacuum distillation tower 3, and a second reboiler 100 for the negative pressure tower 2 are respectively installed in the reboiler of the atmospheric distillation tower 4 and the reboiler of the vacuum distillation tower 3. The low-temperature heat source sequentially heats the second reboiler 102 for the atmospheric distillation tower 4 and the second reboiler 101 for the vacuum distillation tower 3 and the second reboiler 100 for the negative pressure tower 2. 2. The second reboiler 101 of the vacuum distillation tower and the second reboiler 100 of the negative pressure tower are heated. When the low temperature heat source at the distillation site exceeds 100°C, the bottom of the pre-distillation tower 1, the bottom of the atmospheric distillation tower 4, the bottom of the vacuum distillation tower 3, and the bottom of the negative pressure tower 2 are respectively equipped with a second reboiler 86 of the pre-distillation tower, a second reboiler 102 of the atmospheric distillation tower, a second reboiler 101 of the vacuum distillation tower, and a second reboiler 100 of the negative pressure tower. The low temperature heat source is heated by the second reboiler 86 of the pre-distillation tower, the second reboiler 102 of the atmospheric distillation tower, the second reboiler 101 of the vacuum distillation tower, and the second reboiler 100 of the negative pressure tower in sequence. When the low-temperature heat source at the distillation site exceeds 120℃, the reboilers of the medium-pressure column 5, the pre-distillation column 1, the atmospheric column 4, the vacuum column 3, and the negative-pressure column 2 are respectively equipped with a medium-pressure column second reboiler 103, a pre-distillation column second reboiler 86, an atmospheric column second reboiler 102, a vacuum column second reboiler 101, and a negative-pressure column second reboiler 100. The low-temperature heat sources are supplied sequentially by the medium-pressure column second reboiler 103, the pre-distillation column second reboiler 86, the atmospheric column second reboiler 102, the vacuum column second reboiler 101, and the negative-pressure column second reboiler 86.

[0073] In the initial stage, crude methanol is fed into each tower, and heat is supplied to the high-pressure tower reboiler 30 through steam pipeline 37 to gradually establish the temperature gradient of each tower. Specifically:

[0074] Crude methanol is preheated in preheater 9 and preheater 10 to about 80°C. The preheated crude methanol then enters pre-distillation column 1 for distillation. The top pressure of pre-distillation column 1 is 170 kPa, the top temperature is 81°C, and the bottom temperature is 83°C. The vapor phase collected from the top of pre-distillation column 1 goes to reboiler 27 of atmospheric pressure column to provide the heat required for distillation in atmospheric pressure column 4. After being cooled by pre-distillation column condenser 41, it enters extraction tank 40. The non-condensable gas generated after extraction in extraction tank 40 is discharged, and the liquid phase generated after extraction is refluxed to pre-distillation column 1.

[0075] The liquid phase collected from the bottom of the pre-distillation column 1 is cooled by heat exchange with the preheater 9 and then enters the negative pressure column 2. The pressure at the top of the negative pressure column 2 is 40 kPa, the temperature at the top is 43°C, and the temperature at the bottom is 50°C. The vapor phase collected from the top of the negative pressure column 2 is condensed by the negative pressure column condenser 48 and then enters the negative pressure column reflux tank 47. The liquid phase in the negative pressure column reflux tank 47 is divided into two streams. One stream flows back to the negative pressure column 2, and the other stream is collected as refined methanol. The heat required for the reboiler 25 of the negative pressure column is provided by the methanol vapor at the top of the vacuum column 3. The vacuum environment of the negative pressure column 2 is provided by the vacuum system 49 of the negative pressure column.

[0076] The material from the bottom of the negative pressure tower 2 enters the vacuum tower 3 for distillation. The pressure at the top of the vacuum tower 3 is 70 kPa, the temperature at the top is 55°C, and the temperature at the bottom is 63°C. The vapor phase collected from the top of the vacuum tower 3 enters the vacuum tower reflux tank 56 after heat exchange in the negative pressure tower reboiler 25. The liquid phase in the vacuum tower reflux tank 56 is divided into two streams, one of which flows back to the vacuum tower 3, and the other is collected as refined methanol. The heat required by the vacuum tower reboiler 26 is provided by the methanol vapor from the top of the atmospheric pressure tower 4, and the vacuum environment of the vacuum tower 3 is provided by the vacuum tower vacuum system 57.

[0077] The material from the bottom of the vacuum distillation tower 3 enters the atmospheric distillation tower 4 for rectification. The pressure at the top of the atmospheric distillation tower 4 is 115 kPa, the temperature at the top is 68°C, and the temperature at the bottom is 76°C. The vapor phase collected from the top of the atmospheric distillation tower 4 exchanges heat with the reboiler 26 of the vacuum distillation tower and then enters the reflux tank 63 of the atmospheric distillation tower. The liquid phase in the reflux tank 63 of the atmospheric distillation tower is divided into two streams. One stream flows back to the atmospheric distillation tower 4, and the other stream is collected as refined methanol. The heat required by the reboiler 27 of the atmospheric distillation tower is provided by the steam from the top of the pre-distillation tower 1.

[0078] The liquid in the bottom of atmospheric column 4 is preheated by medium-pressure column preheater 15 and then enters medium-pressure column 5 for further distillation. The top pressure of medium-pressure column 5 is 300 kPa, the top temperature is 95°C, and the bottom temperature is 109°C. The vapor phase collected from the top of medium-pressure column 5 goes to the pre-distillation column reboiler 24 to provide the heat required for distillation in pre-distillation column 1. After heat exchange, it enters the medium-pressure column reflux tank 69. The liquid phase in the medium-pressure column reflux tank 69 is divided into two streams. One stream flows back to medium-pressure column 5, and the other stream exchanges heat with the medium-pressure column preheater 15 and is collected as refined methanol. Medium-pressure column 5 is indirectly heated by medium-pressure column reboiler 28, which is heated by the vapor phase collected from the top of pressurized column 6.

[0079] The liquid at the bottom of the medium-pressure column 5 is preheated by the pressure column preheater 17 and then enters the pressure column 6 for further distillation. The pressure at the top of the pressure column 6 is 550 kPa, the temperature at the top is 115°C, and the temperature at the bottom is 132°C. The vapor phase collected from the top of the pressure column 6 goes to the medium-pressure column reboiler 28 to provide the heat required for distillation in the medium-pressure column 5. After heat exchange, it enters the pressure column reflux tank 75. The liquid phase in the pressure column reflux tank 75 is divided into two streams. One stream flows back to the pressure column 6, and the other stream exchanges heat with the pressure column preheater 17 and is collected as refined methanol. The pressure column 6 is indirectly heated by the pressure column reboiler 29, which is the heat source of the vapor phase collected from the top of the high-pressure column 7.

[0080] The liquid in the bottom of pressurized column 6 is heated sequentially by high-pressure column preheaters 1-19, 20-20, and 3-21 before entering high-pressure column 7 for further distillation. The pressure at the top of high-pressure column 7 is 1050 kPa, the temperature at the top is 139°C, and the temperature at the bottom is 182°C. The vapor phase from the top of high-pressure column 7 goes to the reboiler 29 of pressurized column 6 to provide the heat required for distillation. After condensation, it enters the reflux tank 81 of high-pressure column 6. The liquid phase in the reflux tank 81 splits into two streams, one of which flows back to the pressurized column. 6. One stream, after exchanging heat with the high-pressure tower preheater 19, is collected as refined methanol; the side-collection pipeline 22 of the high-pressure tower 7 collects fusel oil; the bottom liquid collected from the high-pressure tower 7 is collected as wastewater after exchanging heat with the high-pressure tower preheater 20; the high-pressure tower 7 is provided with the heat required for distillation by indirect heating through the high-pressure tower reboiler 30. The heat source of the high-pressure tower reboiler 30 is medium-pressure steam or low-pressure steam. The steam after heating is collected as steam condensate after exchanging heat with the high-pressure tower preheater 31 and the preheater 210.

[0081] Furthermore, the wastewater from the bottom of high-pressure tower 7 is used to heat high-pressure tower preheater 20, thus reusing the heat; the material from the bottom of pre-distillation tower 1 is used to heat preheater 9, thus reusing the heat; steam provides heat to high-pressure tower reboiler 30, and then continues to heat high-pressure tower preheater 21 and preheater 10, thus reusing the heat; the refined methanol from high-pressure tower 7 is used to heat high-pressure tower preheater 19, thus reusing the heat; the refined methanol from pressurized tower 6 is used to heat pressurized tower preheater 17, thus reusing the heat; the refined methanol from medium-pressure tower 5 is used to heat medium-pressure tower preheater 16, thus reusing the heat; the above-mentioned heat reuse further reduces additional energy consumption.

[0082] Example 5:

[0083] Taking the distillation apparatus of Example 3 as an example, another specific embodiment is as follows:

[0084] In this embodiment, the operating pressures of the pre-distillation tower 1, negative pressure tower 2, reduced pressure tower 3, atmospheric pressure tower 4, medium pressure tower 5, pressurized tower 6, and high pressure tower 7 are 0.25 MPa, 25 kPa, 55 kPa, 0.10 MPa, 0.30 MPa, 0.55 MPa, and 1.20 MPa, respectively. Crude methanol with a water content of 12.0% is distilled according to this application. After 24 hours of equilibrium, the refined methanol content in the product methanol tank 53 is ≥99.99%. The flow rate of fusel oil collected from the side sampling pipeline 22 is 0.35 t·h⁻¹. The wastewater from the high pressure tower 7 is discharged through the wastewater pipeline 23, and the methanol content in the wastewater is ≤150 mg·L⁻¹.

[0085] Example 6:

[0086] Taking the distillation apparatus of Example 3 as an example, another specific embodiment is as follows:

[0087] In this embodiment, the operating pressures of the pre-distillation column 1, negative pressure column 2, reduced pressure column 3, atmospheric pressure column 4, medium pressure column 5, pressurized column 6, and high pressure column 7 are 0.25 MPa, 30 kPa, 65 kPa, 0.10 MPa, 0.30 MPa, 0.55 MPa, and 1.20 MPa, respectively. Crude methanol (80 t·h⁻¹) with a water content of 15.0% is distilled using this method, and continuous operation yields refined methanol with a mass fraction ≥99.95%. The flow rate of fusel oil from the side-harvest pipeline 22 is increased to 0.42 t·h⁻¹, and the steam consumption is 0.21 t of steam (t of methanol). - 1.

[0088] Example 7:

[0089] Another specific embodiment using the distillation apparatus of Example 3:

[0090] An aldehyde extraction branch pipe is added to the top of atmospheric pressure tower 4 and connected in parallel with the atmospheric pressure tower reflux tank 63 to a gas phase water washing tower; the rest of the equipment is the same as in Example 5. The raw material is crude methanol (60t·h-1) containing 1.5% aldehyde impurities. 90% of the gas phase at the top of atmospheric pressure tower 4 is still supplied to the vacuum tower reboiler 26 by the atmospheric pressure tower top pipeline 33, and 10% enters the gas phase water washing tower and is then refluxed to the atmospheric pressure tower reflux tank 63.

[0091] Results: Aldehyde content ≤ 4 mg·kg -1 The yield of refined methanol was 97.2%, and the steam consumption was 0.245 t steam (t methanol). - 1.

[0092] Example 8:

[0093] Based on Example 3, the gas phase at the top of the high-pressure tower 7 is sent to the mechanical steam recompression unit (compression ratio 1.35) via the high-pressure tower top pipeline 36 for heating and then exchanges heat with the pressurized tower reboiler 29, replacing the direct heat exchange between the gas phase at the top of the high-pressure tower 7 and the pressurized tower reboiler 29 via the tower top pipeline 36; the high-pressure tower reboiler 30 is supplemented with 0.25MPag low-pressure steam.

[0094] After balanced operation, the net steam consumption was reduced to 0.155 t (t methanol). - 1. Total energy costs decreased by 14.6%.

[0095] Example 9:

[0096] Based on Example 3, the packing of medium-pressure tower 5 and pressurized tower 6 is replaced with stainless steel floating valve tower plates. The original flow rates of medium-pressure tower reflux pump 71 and pressurized tower reflux pump 77 are maintained, with only the reflux ratio being slightly adjusted (by the automatic control system); other pipelines and thermal coupling remain unchanged.

[0097] The theoretical plate number of medium-pressure tower 5 and pressurized tower 6 is reduced by 18.5% each, and the system pressure drop is reduced by 8.4 kPa; the purity of refined methanol is above 99.97%, and the steam consumption is 0.232 t steam (t methanol). - 1.

[0098] Example 10:

[0099] In Example 3, a distributed control system is configured: the methanol volume fraction at the top of each of the pre-distillation column 1, negative pressure column 2, reduced pressure column 3, atmospheric pressure column 4, medium pressure column 5, pressurized column 6, and high pressure column 7 is fed back to the control valve by the online chromatograph, automatically adjusting the frequency of the reflux pumps: pre-distillation column reflux pump 45, negative pressure column reflux pump 51, reduced pressure column reflux pump 59, atmospheric pressure column reflux pump 65, medium pressure column reflux pump 71, pressurized column reflux pump 77, and high pressure column reflux pump 83; the steam valve of the high pressure column reboiler 30 is connected to the top pressure of the high pressure column 7 in a closed loop, with a sampling period of 5 seconds.

[0100] After 72 hours of continuous operation, the purity of refined methanol fluctuated by ±0.02%, and the yield of fusel oil produced by side-harvest pipeline 22 increased by 12%.

[0101] In summary, this application achieves thermal coupling by using methanol vapor from the top of the high-pressure column to heat the bottom of the pressurized column; by using methanol vapor from the top of the pressurized column to heat the bottom of the medium-pressure column; by using methanol vapor from the top of the medium-pressure column to heat the bottom of the pre-distillation column; by using methanol vapor from the top of the pre-distillation column to heat the bottom of the atmospheric column; by using methanol vapor from the top of the atmospheric column to heat the bottom of the vacuum column; and by using methanol vapor from the top of the vacuum column to heat the bottom of the negative-pressure column. This application achieves seven-fold utilization of steam, resulting in significant energy savings. Compared with traditional methanol processes, it can... This reduces steam consumption to 0.20-0.30 t steam / t refined alcohol; compared to the traditional dual-tower thermal coupling process, it can save more than 70% of energy, significantly reducing operating costs for enterprises, significantly reducing carbon emissions, and improving enterprise competitiveness; furthermore, the top steam of the vacuum distillation tower can be switched to be connected to the top condenser of the negative pressure tower, and the negative pressure tower can be shut down in the case of insufficient cold source, so as to carry out six-tower operation; when the cold source is sufficient, a vacuum tower can be set up before the pre-distillation tower and the negative pressure tower, and the top steam of the negative pressure tower can be used to heat the reboiler of the vacuum tower, so as to realize eight-tower series operation.

[0102] This application achieves comprehensive performance optimization of the system by increasing the number of towers and enhancing the coupling effect between them, especially by further reducing energy consumption and addressing the problem of poor controllability of parallel operation process parameters. The coupling effect between the towers in this application has the following advantages: (1) More energy-efficient: The heat transfer temperature difference is reduced, the thermodynamic reversibility of the system is increased, and heat consumption is reduced; (2) More stable: Through the step temperature difference control, multiple towers produce products, and the indicators are balanced with each other, avoiding the impact of fluctuations in a single link on the overall system and ensuring stronger system stability; (3) More flexible: This application distributes the load to multiple towers to adapt and bear the load respectively, and increases the system operation flexibility by adjusting the preheating method and adding a second reboiler, thereby increasing the system operation elasticity and improving the capacity elasticity.

[0103] The devices and connections not specifically described above are all existing technologies, and will not be described in detail here.

[0104] 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.

[0105] 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.

[0106] Furthermore, various different implementations of this application can be combined in any way, as long as they do not violate the spirit of this application, and such combinations should also be regarded as the content disclosed in this application.

Claims

1. A crude methanol complete cascade multi-effect distillation apparatus, characterized in that, The system includes a pre-distillation column (1), a negative pressure column (2), a reduced pressure column (3), an atmospheric pressure column (4), a medium pressure column (5), a pressurized column (6), and a high pressure column (7) connected in sequence. The reboilers of the pre-distillation column (1), negative pressure column (2), reduced pressure column (3), atmospheric pressure column (4), medium pressure column (5), pressurized column (6), and high pressure column (7) are respectively connected to a pre-distillation column reboiler (24), a negative pressure column reboiler (25), a reduced pressure column reboiler (26), an atmospheric pressure column reboiler (27), a medium pressure column reboiler (28), a pressurized column reboiler (29), and a high pressure column reboiler (30). The top of the pre-distillation column (1) is open to... The top of the pre-pressure tower is connected to the reboiler (27) of the atmospheric pressure tower via the top pipeline (31). The top of the pressure reducing tower (3) is connected to the reboiler (25) of the negative pressure tower via the top pipeline (32). The top of the atmospheric pressure tower (4) is connected to the reboiler (26) of the pressure reducing tower via the top pipeline (33). The top of the medium pressure tower (5) is connected to the reboiler (24) of the pre-pressure tower via the top pipeline (34). The top of the pressurized tower (6) is connected to the reboiler (28) of the medium pressure tower via the top pipeline (35). The top of the high pressure tower (7) is connected to the reboiler (29) of the pressurized tower via the top pipeline (36).

2. The crude methanol complete cascade multi-effect distillation apparatus according to claim 1, characterized in that, The top of the negative pressure tower (2) is connected to the negative pressure tower reflux tank (47) via the negative pressure tower top pipeline (46). A negative pressure tower condenser (48) is installed on the negative pressure tower top pipeline (46). The pressure reducing tower (3) is connected to the negative pressure tower condenser (48) via the pressure reducing tower top pipeline (32). The top of the negative pressure tower reflux tank (47) is connected to the negative pressure tower vacuum system (49). The bottom of the negative pressure tower reflux tank (47) is connected to the middle and upper part of the negative pressure tower (2) via the negative pressure tower reflux pipeline (50). The bottom of the negative pressure tower reflux tank (47) is also connected to the middle and upper part of the pressure reducing tower (3) via the negative pressure tower-pressure reducing tower reflux pipeline (99). The negative pressure tower reflux pipeline (50) and the negative pressure tower-pressure reducing tower reflux pipeline (99) are connected to the negative pressure tower refined methanol collection pipeline (52).

3. The crude methanol complete cascade multi-effect distillation apparatus according to claim 1, characterized in that, A vacuum tower (87) is provided between the pre-distillation tower (1) and the negative pressure tower (2). The bottom of the vacuum tower (87) is connected to a vacuum tower reboiler (89). The top of the negative pressure tower (2) is connected to the vacuum tower reboiler (89) through a negative pressure tower top pipeline (46).

4. The crude methanol complete cascade multi-effect distillation apparatus according to claim 3, characterized in that, The bottom of the pre-distillation column (1) is connected to the vacuum column (87) via the pre-distillation column bottom pipeline (11). The bottom of the vacuum column (87) is connected to the negative pressure column (2) via the vacuum column bottom pipeline (88). The top of the negative pressure column (2) is connected to the input end of the vacuum column reboiler (89) via the negative pressure column top pipeline (46). The output end of the vacuum column reboiler (89) is connected to the negative pressure column reflux tank (47). The top of the negative pressure column reflux tank (47) is connected to the negative pressure column vacuum system (49). The bottom of the negative pressure column reflux tank (47) is connected to the middle and upper part of the negative pressure column (2) via the negative pressure column reflux pipeline (50). A negative pressure column reflux pump (51) is installed on the negative pressure column reflux pipeline (50). The negative pressure column reflux pipeline (50) is connected to the negative pressure column refined methanol collection pipeline (52).

5. A crude methanol complete cascade multi-effect distillation apparatus according to claim 2 or 4, characterized in that, The reboilers of the medium-pressure column (5), the pre-distillation column (1), the atmospheric column (4), the vacuum column (3), and the negative-pressure column (2) are respectively equipped with a second reboiler (103) for the medium-pressure column, a second reboiler (86) for the pre-distillation column, a second reboiler (102) for the atmospheric column, a second reboiler (101) for the vacuum column, and a second reboiler (100) for the negative-pressure column.

6. A crude methanol complete cascade multi-effect distillation apparatus according to claim 2 or 4, characterized in that, The atmospheric pressure tower (4) is connected to the medium pressure tower (5) through the atmospheric pressure tower bottom pipeline (14). The atmospheric pressure tower bottom pipeline (14) is equipped with a medium pressure tower preheater (15). The output end of the preheater reboiler (24) is connected to the medium pressure tower reflux tank (69) through the first medium pressure tower reflux pipeline (68). The bottom of the medium pressure tower reflux tank (69) is connected to the medium pressure tower (5) through the second medium pressure tower reflux pipeline (70). The second medium pressure tower reflux pipeline (70) is equipped with a medium pressure tower reflux pump (71). The second medium pressure tower reflux pipeline (70) is connected to the medium pressure tower refined methanol outlet pipeline (72). The medium pressure tower refined methanol outlet pipeline (72) is connected to the input end and the output end of the medium pressure tower preheater (15) respectively.

7. A crude methanol complete cascade multi-effect distillation apparatus according to claim 2 or 4, characterized in that, The medium-pressure tower (5) is connected to the pressurized tower (6) via the medium-pressure tower bottom pipeline (16), and a pressurized tower preheater (17) is installed on the medium-pressure tower bottom pipeline (16); the output end of the medium-pressure tower reboiler (28) is connected to the pressurized tower reflux tank (75) via the first pressurized tower reflux pipeline (74), and the bottom of the pressurized tower reflux tank (75) is connected to the pressurized tower (6) via the second pressurized tower reflux pipeline (76), and a pressurized tower reflux pump (77) is installed on the second pressurized tower reflux pipeline (76), which is connected to the pressurized tower refined methanol outlet pipeline (78), and the pressurized tower refined methanol outlet pipeline (78) is connected to the input end and the output end of the pressurized tower preheater (17) respectively.

8. A crude methanol complete cascade multi-effect distillation apparatus according to claim 2 or 4, characterized in that, The output end of the pressurized tower reboiler (29) is connected to the high-pressure tower reflux tank (81) through the high-pressure tower reflux pipeline one (80). The bottom of the high-pressure tower reflux tank (81) is connected to the high-pressure tower (7) through the high-pressure tower reflux pipeline two (82). The high-pressure tower reflux pump (83) is installed on the high-pressure tower reflux pipeline two (82). The high-pressure tower reflux pipeline two (82) is connected to the high-pressure tower refined methanol collection pipeline (84).

9. The crude methanol complete cascade multi-effect distillation apparatus according to claim 8, characterized in that, A feed line (8) is provided on one side of the pre-distillation column (1), and a pre-column preheater (9) and a pre-column preheater (10) are provided on the feed line (8); the pre-distillation column (1) is connected to the negative pressure column (2) through the pre-column bottom line (11), and the pre-distillation column (1) is connected to the pressure reducing column (3) through the pre-column bottom line (11) and the negative pressure column bottom line (12), and the pre-column bottom line (11) passes through the pre-column preheater (9).

10. A crude methanol complete cascade multi-effect distillation apparatus according to claim 9, characterized in that, The bottom of the pressurized tower (6) is connected to the high-pressure tower (7) via the pressurized tower bottom pipeline (18). The pressurized tower bottom pipeline (18) is sequentially equipped with a high-pressure tower preheater one (19), a high-pressure tower preheater two (20), and a high-pressure tower preheater three (21). The high-pressure tower refined methanol collection pipeline (84) passes through the high-pressure tower preheater one (19). The bottom of the high-pressure tower (7) is equipped with a wastewater pipeline (23), which passes through the high-pressure tower preheater two (20). The input end of the high-pressure tower reboiler (30) is connected to the steam pipeline (37), and the output end of the high-pressure tower reboiler (30) is connected to the condensate pipeline (38). The condensate pipeline (38) passes through the high-pressure tower preheater three (21) and the preheater two (10) in sequence.

Images