Six-tower multi-effect rectification process and rectification device for crude methanol

Abstract

The invention provides a six-tower multi-effect rectification process and rectification device for crude methanol, and the device comprises a pre-rectification tower, a negative pressure rectification tower, a pressurized rectification tower, a normal pressure rectification tower and a recovery tower which are connected in sequence, the pressurizing rectifying tower and the secondary pressurizing rectifying tower are arranged in parallel, or the secondary pressurizing rectifying tower is arranged between the negative-pressure rectifying tower and the pressurizing rectifying tower, or the secondary pressurizing rectifying tower is arranged between the pressurizing rectifying tower and the normal-pressure rectifying tower; a secondary pressurizing tower reboiler is arranged at the lower part of the secondary pressurizing rectifying tower and is connected with a heat input device; according to the invention, heat of the heat input device is integrated into the rectification system, so that greater energy-saving and carbon-reducing benefits are achieved; a six-tower thermal coupling process is adopted, a heat exchange network is optimized, and the energy-saving space is enlarged; compared with the traditional methanol process, the unit consumption of steam can be reduced; and the methanol with the concentration of more than 99.99% can be extracted.

Description

Technical Field

[0001] The present application relates to the technical field of methanol distillation, and in particular to a six-tower multi-effect distillation process and a distillation device for crude methanol. Background Art

[0002] Methanol is an important chemical raw material, widely used in chemical, energy and fuel cell fields. In the production process of methanol, distillation is a key separation operation used to purify methanol products. Traditional methanol distillation usually adopts a three-tower process of pre-tower, pressure tower and atmospheric tower, and uses the technology of thermal coupling between the pressure tower and the atmospheric tower to achieve energy saving of the distillation system. Specifically, the steam from the top of the pressure tower is used to heat the atmospheric tower to achieve energy saving. However, the atmospheric tower and the pre-tower top are cooled by circulating water, which results in a large amount of heat being wasted, making the steam consumption of the entire system relatively high, about 1.2t steam / t refined alcohol. Against the background of the country's increasingly stringent requirements on carbon emission indicators, a new technology is needed to recover heat in the original system to achieve the goal of energy saving and emission reduction.

[0003] The methanol synthesis tower is one of the key equipment in the methanol production process. It is at the front end of the entire production process. In the methanol synthesis tower, carbon monoxide, carbon dioxide and hydrogen react chemically under a certain temperature, pressure and catalyst to generate crude methanol. The methanol synthesis tower is an exothermic reaction process. Most of the low-temperature waste heat of the methanol synthesis tower is dissipated into the atmosphere by water cooling, air cooling or evaporative cooling, and is not fully utilized. This application aims to achieve greater energy-saving and carbon-reduction benefits by integrating the heat of the synthesis gas generated by the methanol synthesis tower into the distillation system.

[0004] The applicant has not found any relevant invention ideas after searching; therefore, a new technical solution is provided to solve the above problems. Summary of the invention

[0005] The present application provides a six-tower multi-effect distillation process for crude methanol, comprising the following steps:

[0006] The crude methanol enters the pre-distillation tower, and the liquid phase extracted from the bottom of the pre-distillation tower enters the negative pressure distillation tower for distillation;

[0007] The liquid phase extracted from the kettle of the negative pressure distillation tower enters the pressure distillation tower and the secondary pressure distillation tower for distillation respectively;

[0008] The liquid phase extracted from the kettle of the pressure distillation tower is mixed with the liquid phase extracted from the kettle of the secondary pressure distillation tower and then enters the atmospheric distillation tower;

[0009] Wastewater is extracted from the bottom of the atmospheric distillation tower, and fusel alcohol extracted from one side of the atmospheric distillation tower enters the recovery tower;

[0010] Fusel alcohol is produced from one side of the recovery tower, and waste water is produced from the kettle of the recovery tower;

[0011] The reboiler of the pressure tower provides heat through low-pressure steam or a heat input device, and the reboiler of the sub-pressure tower recovers heat through a heat input device to provide heat.

[0012] As a preferred solution, the crude methanol is preheated and then enters the pre-distillation tower.

[0013] As a preferred solution, the gas at the top of the secondary pressure distillation tower provides heat to the pre-tower reboiler.

[0014] As a preferred solution, the gas phase at the top of the pre-distillation tower supplies heat to the negative pressure tower reboiler 1, the gas phase at the top of the atmospheric distillation tower supplies heat to the negative pressure tower reboiler 2, the gas phase at the top of the recovery tower supplies heat to the negative pressure tower reboiler 3, the gas phase at the top of the pressure distillation tower supplies heat to the atmospheric pressure tower reboiler and the recovery tower reboiler respectively, or the gas phase at the top of the pressure distillation tower supplies heat to the atmospheric pressure tower reboiler, the recovery tower reboiler, and the pre-tower reboiler 1 respectively.

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

[0016] As a preferred embodiment, the heat input device adopts a synthesis reaction tower, and the synthesis gas extracted from the bottom of the synthesis reaction tower enters the heat exchanger tube for heat exchange, and enters the cooling device after heat exchange. The cooling medium is introduced into one input end of the cooling device, and one output end of the cooling device is connected to the reboiler of the secondary pressure tower, or is connected to the reboiler of the secondary pressure tower and the reboiler of the pressure tower.

[0017] As a preferred solution, after heat exchange with the heat exchanger, it enters the cooler, cooler 2, and cooler 3 in sequence, and cold medium is introduced into the shell side of the cooler, cooler 2, and cooler 3. After heat exchange with the synthesis gas, the cold medium entering the cooler, cooler 2, and cooler 3 is completely converted into gas phase, and at least one gas phase is sent to the reboiler of the secondary pressure tower and / or the reboiler of the pressure tower.

[0018] As a preferred solution, the gas phase is compressed and then sent to the reboiler of the secondary pressure tower and / or the reboiler of the pressure tower.

[0019] As a preferred solution, the synthesis gas after cooling in the cooler is further condensed through the condenser, and after condensation, it is decompressed by the high-pressure separator, and the liquid phase obtained after gas-liquid separation is filtered through the crude methanol filter, and then enters the methanol flash tank for flash evaporation, and the crude methanol obtained by flash evaporation is sent to the pre-distillation tower as a raw material.

[0020] As a preferred solution, the crude methanol obtained by flash evaporation enters the crude methanol buffer tank, and the crude methanol extracted from the crude methanol buffer tank enters the pre-distillation tower as a raw material.

[0021] As a preferred solution, the gas phase is compressed and then sent to the reboiler of the secondary pressure tower and / or the reboiler of the pressure tower.

[0022] The present application provides a six-tower multi-effect distillation device for crude methanol, comprising a pre-distillation tower, wherein the rear portion of the pre-distillation tower is sequentially connected to a negative pressure distillation tower, a pressurized distillation tower, an atmospheric pressure distillation tower, and a recovery tower, wherein the pressurized distillation tower is arranged in parallel with a secondary pressurized distillation tower, or the secondary pressurized distillation tower is arranged between the negative pressure distillation tower and the pressurized distillation tower, or the secondary pressurized distillation tower is arranged between the pressurized distillation tower and the atmospheric pressure distillation tower; a secondary pressurized tower reboiler is arranged at the lower portion of the secondary pressurized distillation tower, and the secondary pressurized tower reboiler is connected to a heat input device.

[0023] As a preferred solution, the top of the secondary pressure distillation tower is connected to the pre-tower reboiler.

[0024] As a preferred solution, the pressure tower reboiler arranged at the bottom of the pressure distillation tower is connected to a low-pressure steam device and / or a heat input device.

[0025] As a preferred solution, the heat input device adopts a synthesis reaction tower.

[0026] As a preferred embodiment, the synthesis reaction tower is connected to a heat exchanger, the heat exchanger is connected to a cooling device, the cooling device is connected to the input end of the synthesis gas processing device, and the output end of the synthesizer processing device is connected to the pre-distillation tower; wherein, the other input end of the cooling device is connected to the medium input pipeline, and the other output end of the cooling device is connected to the secondary pressure tower reboiler, or is connected to the secondary pressure tower reboiler and the pressure tower reboiler.

[0027] As a preferred embodiment, the cooling device includes a cooler, a cooler 2, and a cooler 3 connected in sequence, the input ends of the cooler, the cooler 2, and the cooler 3 are connected to a medium input pipeline, and the output ends of the cooler, the cooler 2, and the cooler 3 are respectively connected to a medium gas output pipeline, a medium gas output pipeline 2, and a medium gas output pipeline 3, and at least one of the medium gas output pipeline, the medium gas output pipeline 2, and the medium gas output pipeline 3 is connected to a secondary pressure tower reboiler and / or a pressure tower reboiler.

[0028] As a preferred solution, the medium gas output pipeline, the medium gas output pipeline 2, and the medium gas output pipeline 3 are respectively provided with compressor 1, compressor 2, and compressor 3.

[0029] As a preferred solution, the synthesis gas processing device includes a condenser connected to cooler three, and the condenser is connected to the high-pressure separator, the crude methanol filter, and the methanol flash tank in sequence.

[0030] As a preferred solution, the methanol flash tank is connected to the crude methanol buffer tank via an output pipeline, and the crude methanol buffer tank is connected to the pre-distillation tower.

[0031] As a preferred embodiment, the top of the pre-distillation tower is connected to the negative pressure tower reboiler one through the pre-tower gas phase extraction pipeline, the top of the atmospheric distillation tower is connected to the negative pressure tower reboiler two through the atmospheric pressure tower gas phase pipeline, the top of the recovery tower is connected to the negative pressure tower reboiler three through the recovery tower gas phase pipeline, and the top of the secondary pressurized distillation tower is connected to the pre-tower reboiler through the secondary pressurized tower gas phase pipeline; the top of the pressurized distillation tower is respectively connected to the atmospheric pressure tower reboiler and the recovery tower reboiler through the pressurized tower gas phase pipeline, or the top of the pressurized distillation tower is respectively connected to the pre-tower reboiler one, the atmospheric pressure tower reboiler, and the recovery tower reboiler through the pressurized tower gas phase pipeline.

[0032] As a preferred embodiment, the pressure tower reboiler includes a pressure tower reboiler 1, and the pressure tower reboiler 1 is connected to a low-pressure steam device.

[0033] As a preferred embodiment, the pressure tower reboiler includes pressure tower reboiler one and pressure tower reboiler two, the pressure tower reboiler one is connected to the low-pressure steam device, and the pressure tower reboiler two is connected to the heat input device.

[0034] As a preferred scheme, the output end of the negative pressure tower reboiler one is connected to the pre-tower reflux device through the negative pressure tower reboiler one output pipeline; the negative pressure tower reboiler two is connected to the atmospheric pressure tower refined methanol production device through the negative pressure tower reboiler two output pipeline; the negative pressure tower reboiler three output pipeline of the negative pressure tower reboiler three is connected to the recovery tower refined methanol production device; the pre-tower reboiler output pipeline of the pre-tower reboiler is connected to the secondary pressurized tower refined methanol production device; the output ends of the atmospheric pressure tower reboiler and the recovery tower reboiler are connected to the pressurized tower refined methanol production device through the output pipelines, or the output ends of the pre-tower reboiler one, the atmospheric pressure tower reboiler and the recovery tower reboiler are connected to the pressurized tower refined methanol production device through the output pipelines.

[0035] As a preferred solution, the top of the negative pressure distillation tower is connected to the negative pressure tower refined methanol extraction device through a negative pressure tower gas phase pipeline, and a negative pressure tower top condenser is arranged on the negative pressure tower gas phase pipeline.

[0036] As a preferred embodiment, the negative pressure tower refined methanol production device includes a negative pressure tower reflux tank, the bottom of the negative pressure tower reflux tank is connected to the middle and upper part of the negative pressure tower through a negative pressure tower reflux pipeline, and the negative pressure tower reflux pipeline is connected to the negative pressure tower refined methanol production pipeline.

[0037] As a preferred scheme, the bottom of the negative pressure distillation tower is connected to the pressurized distillation tower and the sub-pressurized distillation tower respectively through the negative pressure tower bottom extraction pipeline and the negative pressure tower bottom extraction pipeline 1, and the negative pressure tower bottom extraction pipeline is provided with a pressurized tower preheater 1 and a pressurized tower preheater 2; the pressurized tower reboiler is connected to the low-pressure steam input pipeline, the pressurized tower reboiler output pipeline of the pressurized tower reboiler is connected to the pressurized tower preheater 2, the output end of the pressurized tower preheater 2 is connected to the pre-tower preheater 2 through the preheater 2 output pipeline, and the output end of the pre-tower preheater 2 is connected to the steam reflux pipeline.

[0038] The present application achieves greater energy conservation and carbon reduction benefits by integrating the heat of the synthesis gas generated by the methanol synthesis tower into the distillation system; adopts a six-tower thermal coupling process and device to optimize the heat exchange network and increase energy conservation space; compared with the traditional methanol process, it can reduce steam consumption per unit; and the present application can produce methanol with a concentration of >99.99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic structural block diagram of Embodiment 1 of the present application;

[0040] Figure 2 It is a structural schematic diagram of Embodiment 1 of the present application;

[0041] Figure 3 is a schematic structural block diagram of Embodiment 2 of the present application;

[0042] Figure 4 This is a schematic diagram of the structure of the second embodiment of the present application;

[0043] Figure 5 is a structural schematic diagram of a synthesis gas processing device according to Example 1 of the present application;

[0044] Figure 6 It is a schematic diagram of the structure of the synthesis gas processing device of Example 2 of the present application.

[0045] 1. Pre-rectification tower; 2. Feed pipeline; 3. Pre-tower preheater 1; 4. Pre-tower preheater 2; 5. Pre-tower kettle extraction pipeline; 6. Negative pressure distillation tower; 7. Negative pressure tower bottom extraction pipeline; 8. Negative pressure tower bottom extraction pipeline 1; 9. Pressurized distillation tower; 10. Secondary pressurized distillation tower; 11. Pressurized tower preheater 1; 12. Pressurized tower preheater 2; 13. Pressurized tower kettle extraction pipeline; 14. Atmospheric pressure distillation tower; 15. Secondary pressurized tower kettle extraction pipeline; 16. Atmospheric pressure tower side extraction pipeline; 17. Recovery tower; 18. Atmospheric pressure tower wastewater extraction pipeline; 19. Fusel alcohol extraction pipeline; 20. Recovery tower wastewater extraction pipeline; 21. Pre-tower reboiler; 22. Pressurized tower reboiler 1; 23. Atmospheric pressure tower reboiler; 24. Recovery tower reboiler; 25 , secondary pressure tower reboiler; 26, cooler; 27, cooler two; 28, cooler three; 29, synthesis gas inlet pipeline; 30, condenser; 31, output pipeline; 32, negative pressure tower reboiler one; 33, negative pressure tower reboiler two; 34, negative pressure tower reboiler three; 35, pre-tower gas phase extraction pipeline; 36, negative pressure tower reboiler one output pipeline; 37, pre-tower buffer tank; 38, pre-tower buffer tank reflux pipeline; 39, pre-tower reflux pump; 40, non-condensable gas extraction pipeline; 41, extraction water pipeline; 42, negative pressure tower reflux tank; 43, negative pressure tower gas phase pipeline; 44, negative pressure tower top condenser; 45, negative pressure tower reflux pipeline; 46, negative pressure tower reflux pump; 47, negative pressure tower refined methanol extraction pipeline; 48, pressure tower gas phase pipeline; 4 9. Output pipeline; 50. Reflux tank of pressure tower; 51. Reflux pipeline of pressure tower; 52. Reflux pump of pressure tower; 53. Extraction pipeline of refined methanol of pressure tower; 54. Gas phase pipeline of atmospheric tower; 55. Second output pipeline of reboiler of negative pressure tower; 56. Reflux tank of atmospheric tower; 57. Reflux pipeline of atmospheric tower; 58. Reflux pump of atmospheric tower; 59. Extraction pipeline of refined methanol of atmospheric tower; 60. Gas phase pipeline of recovery tower; 61. Third output pipeline of reboiler of negative pressure tower; 62. Reflux tank of recovery tower; 63. Reflux pipeline of recovery tower; 64. Reflux pump of recovery tower; 65. Extraction pipeline of refined methanol of recovery tower; 66. Gas phase pipeline of secondary pressure tower; 67. Output pipeline of reboiler of pre-tower; 68. Reflux tank of secondary pressure tower; 69. Reflux pipeline of secondary pressure tower; 70. Reflux pump; 71, secondary pressure tower refined methanol extraction pipeline; 72, low-pressure steam input pipeline; 73, pressure tower reboiler output pipeline; 74, preheater second output pipeline; 75, steam reflux pipeline; 76, medium gas output pipeline; 77, medium input pipeline; 78, heat exchanger; 79, high-pressure separator; 80, methanol flash tank; 81, crude methanol primary filter; 82, crude methanol secondary filter; 83, pre-tower reboiler one; 84, pressure tower reboiler two; 85, methanol gas output main pipeline; 86, medium gas output pipeline two; 87, medium gas output pipeline three; 88, compressor two; 89, compressor three; 90, compressor one; 92, buffer tank gas phase extraction pipeline; 93, pre-tower flash tank; 94, pre-tower condenser;95. Tower condenser outlet pipeline; 96. Flash tank liquid phase extraction pipeline; 97. Crude methanol buffer tank. ; DETAILED DESCRIPTION

[0046] The following is combined with Figure 1 To Attachment Figure 6 The specific implementation of the present invention is described in detail. It should be noted that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0047] Embodiment 1:

[0048] This embodiment provides a six-tower multi-effect distillation process for crude methanol, characterized in that it includes the following steps:

[0049] After being preheated by pre-tower preheater 3 and pre-tower preheater 2 4, crude methanol enters pre-distillation tower 1, and the gas phase at the top of pre-distillation tower 1 supplies heat to negative pressure tower reboiler 32, and the liquid phase extracted from the kettle of pre-distillation tower 1 enters negative pressure distillation tower 6 for distillation; the gas phase after supplying heat to negative pressure tower reboiler 32 enters pre-tower buffer tank 37, and after the material in pre-tower buffer tank 37 is extracted, the gas phase in pre-tower buffer tank 37 enters pre-tower condenser 94 through buffer tank gas phase extraction pipeline 92 for condensation, and the obtained condensate enters pre-tower flash tank 93 through pre-tower condenser outlet pipeline 95, the non-condensable gas in pre-tower flash tank 93 is extracted through non-condensable gas extraction pipeline 40, and the liquid phase in pre-tower flash tank 93 is extracted through flash tank liquid phase extraction pipeline 96 and refluxed to pre-tower buffer tank 37, and the liquid phase in pre-tower buffer tank 37 refluxes to pre-distillation tower 1;

[0050] The gas phase at the top of the negative pressure distillation tower 6 is partially refluxed to the negative pressure distillation tower 6 after condensation, and part of it is extracted as refined methanol; specifically: the gas phase extracted from the top of the negative pressure distillation tower 6 is condensed by the negative pressure tower top condenser 44 and enters the negative pressure tower reflux tank 42, and part of the refined methanol in the negative pressure tower reflux tank 42 is refluxed to the negative pressure distillation tower 6, and part of it is extracted as refined methanol; the liquid phase extracted from the bottom of the negative pressure distillation tower 6 enters the pressure distillation tower 9 and the secondary pressure distillation tower 10 for distillation respectively;

[0051] The gas phase at the top of the pressure distillation tower 9 heats the atmospheric tower reboiler 23 and the recovery tower reboiler 24 respectively, and the gas phase at the top of the secondary pressure distillation tower 10 heats the pre-tower reboiler 21, and the materials after heat exchange with the atmospheric tower reboiler 23 and the recovery tower reboiler 24 enter the pressure tower reflux tank 50, and part of the refined methanol in the pressure tower reflux tank 50 refluxes to the pressure distillation tower 9, and part of it is extracted as refined methanol; the liquid phase extracted from the bottom of the pressure distillation tower 9 is mixed with the liquid phase extracted from the bottom of the secondary pressure distillation tower 10 and then enters the atmospheric distillation tower 14;

[0052] The gas phase at the top of the atmospheric distillation tower 14 provides heat to the negative pressure tower reboiler 2 33, and the material after heat exchange with the negative pressure tower reboiler 2 33 enters the atmospheric tower reflux tank 56, and part of the refined methanol in the atmospheric tower reflux tank 56 is refluxed to the atmospheric distillation tower 14, and part of it is produced as refined methanol; the tower bottom of the atmospheric distillation tower 14 produces waste water, and the fusel alcohol produced on one side of the atmospheric distillation tower 14 enters the recovery tower 17;

[0053] The gas phase at the top of the recovery tower 17 provides heat to the negative pressure tower reboiler 34, and the material after heat exchange with the negative pressure tower reboiler 34 enters the recovery tower reflux tank 62, and part of the refined methanol in the recovery tower reflux tank 62 is refluxed to the recovery tower 17, and part of it is produced as refined methanol; one side of the recovery tower 17 produces fusel alcohol, and the bottom of the recovery tower 17 produces waste water;

[0054] The pressure tower reboiler includes a pressure tower reboiler 22, which provides heat through low-pressure steam. The secondary pressure tower reboiler 25 recovers heat through a heat input device for heating. The heat input device can be a synthesis reaction tower, a converter, etc. In this embodiment, the heat of the synthesis gas extracted from the bottom of the synthesis reaction tower is used for heating. Specifically, the gas extracted from the bottom of the synthesis reaction tower enters the heat exchanger 78 tube pass for heat exchange, and enters the cooling device after heat exchange. A cold water is introduced into one input end of the cooling device. Cooling medium, one output end of the cooling device is connected to the secondary pressure tower reboiler 25, or is connected to the secondary pressure tower reboiler 25 and the pressure tower reboiler 22; more specifically: after heat exchange with the heat exchanger 78, it enters the cooler 26, and the cold medium is introduced into the shell side of the cooler 26. After heat exchange with the synthesis gas, the cold medium entering the shell side of the cooler 26 is completely converted into gas phase, and the gas phase is sent to the secondary pressure tower reboiler 25 to provide heat for the secondary pressure tower reboiler 25; preferably, the gas phase is compressed and sent to the secondary pressure tower reboiler 25.

[0055] The synthesis gas cooled by cooler 26 enters cooler 27 and cooler 3 28 for further cooling. A cold medium can be introduced into cooler 27 and cooler 3 28. The cold medium introduced into cooler 27 and cooler 3 28 is completely converted into gas phase through secondary steam recovery and tertiary steam recovery. At least one gas phase outputted by cooler 26, cooler 27 and cooler 3 28 can be used to supply heat to pressure tower reboiler 1 22. Since the present embodiment takes the low-pressure steam supplying heat to pressure tower reboiler 1 22 as an example, therefore, no cold medium is introduced into cooler 27 and cooler 3 28, and only the reboiler 1 22 is used. The synthesis gas cooled by the cooler 26 is further cooled to a suitable temperature. The synthesis gas cooled by the cooler 28 is further condensed by the condenser 30. After condensation, the liquid phase obtained by decompression and gas-liquid separation in the high-pressure separator 79 is filtered through the crude methanol filter and then enters the methanol flash tank 80 for flash evaporation. The crude methanol obtained by flash evaporation enters the pre-distillation tower 1, more specifically, the crude methanol obtained by flash evaporation enters the pre-tower preheater 3; preferably, the crude methanol obtained by flash evaporation enters the crude methanol buffer tank 97, and the crude methanol extracted from the crude methanol buffer tank 97 enters the pre-tower preheater 3 as raw material through the feed pipeline 2.

[0056] Embodiment 2:

[0057] The present embodiment provides a six-tower multi-effect distillation process for crude methanol, which is different from the first embodiment in that the gas phase at the top of the pressurized distillation tower 9 provides heat to the atmospheric pressure tower reboiler 23, the recovery tower reboiler 24, and the pre-tower reboiler 83 respectively, and the materials after heat exchange with the atmospheric pressure tower reboiler 23, the recovery tower reboiler 24, and the pre-tower reboiler 83 enter the pressurized tower reflux tank 50, and part of the refined methanol in the pressurized tower reflux tank 50 is refluxed to the pressurized distillation tower 9, and part is produced as refined methanol.

[0058] In addition, in this embodiment, the pressure tower reboiler 2 84 supplies heat through the primary recovery heat of the synthesis gas extracted from the bottom of the synthesis reaction tower; the secondary pressure tower reboiler 25 supplies heat through the secondary recovery heat and the tertiary recovery heat of the synthesis gas extracted from the bottom of the synthesis reaction tower; specifically: the synthesis gas extracted from the bottom of the synthesis reaction tower enters the tube side of the heat exchanger 78 for heat exchange, and enters the cooler 26 after heat exchange. A cold medium is introduced into the shell side of the cooler 26. After heat exchange with the synthesis gas, the cold medium entering the shell side of the cooler 26 is completely converted into a gas phase, and the gas phase is sent to the pressure tower reboiler 2 84 to supply heat for the pressure tower reboiler 2 84; the heat required for distillation is provided to the pressurized distillation tower 9, and the synthesis gas cooled by the cooler 26 continues to be cooled by the cooler 27. Methanol enters the shell side of the cooler 27 as a cold medium. After the heat exchange is completed, the methanol is completely converted into a gas phase, and the synthesis gas is cooled to a corresponding temperature by controlling the feed amount of methanol. The gas phase methanol gas is output through the medium gas The pipeline 2 86 is sent to the secondary pressure tower reboiler 25 to provide heat for the secondary pressure tower reboiler 25; the synthesis gas cooled by the cooler 27 continues to be cooled by the cooler 3 28, and methanol enters the shell side of the cooler 3 28 as a cold medium. After the heat exchange is completed, the methanol is completely converted into a gas phase, and the synthesis gas is cooled to a corresponding temperature by controlling the methanol feed amount. The gas phase methanol gas is sent to the secondary pressure tower reboiler 25 through the medium gas output pipeline 3 87 to provide heat for the secondary pressure tower reboiler 25; the synthesis gas cooled by the cooler 3 28 continues to be condensed by the condenser 30, and after the high-pressure separator 79 reduces pressure and separates gas and liquid, the obtained liquid phase is filtered by the crude methanol primary filter 81 and the crude methanol secondary filter 82, and then enters the methanol flash tank 80 for flash evaporation. The crude methanol obtained by flash evaporation enters the crude methanol buffer tank 97, and the crude methanol coming out of the crude methanol buffer tank 97 enters the pre-tower preheater 3 as a raw material through the feed pipeline 2 for preheating and then enters the pre-distillation tower 1.

[0059] Embodiment three:

[0060] like Figure 1 , Figure 2 , Figure 5As shown, this embodiment provides a crude methanol six-tower multi-effect distillation device, including a pre-distillation tower 1, a feed pipeline 2 is arranged on one side of the pre-distillation tower 1, and a pre-tower preheater 3 and a pre-tower preheater 4 are arranged in sequence on the feed pipeline 2, which are used to preheat the crude methanol material entering the pre-distillation tower 1 to improve the stability of distillation; the pre-distillation tower 1 is connected to the middle and lower part of the negative pressure distillation tower 6 through the pre-tower kettle extraction pipeline 5, and the bottom of the negative pressure distillation tower 6 is connected to the middle and lower part of the pressurized distillation tower 9 and the middle and lower part of the secondary pressurized distillation tower 10 through the negative pressure tower bottom extraction pipeline 7 and the negative pressure tower bottom extraction pipeline 8 respectively. In this embodiment, the secondary pressurized distillation tower 10 is connected in parallel with the pressurized distillation tower 9, and the negative pressure A pressure tower preheater 11 and a pressure tower preheater 2 12 are provided on the extraction pipeline 7 at the bottom of the tower; the pressure distillation tower 9 is connected to the middle and lower part of the atmospheric distillation tower 14 through the pressure tower kettle extraction pipeline 13, the pressure tower kettle extraction pipeline 13 is connected to the pressure tower preheater 11, and the secondary pressure distillation tower 10 is connected to the middle and lower part of the atmospheric distillation tower 14 through the secondary pressure tower kettle extraction pipeline 15; one side of the atmospheric distillation tower 14 is connected to the middle and lower part of the recovery tower 17 through the atmospheric tower side extraction pipeline 16, and the bottom of the atmospheric distillation tower 14 is provided with an atmospheric tower wastewater extraction pipeline 18; one side of the recovery tower 17 is provided with a fusel alcohol extraction pipeline 19, and the bottom of the recovery tower 17 is provided with a recovery tower wastewater extraction pipeline 20.

[0061] The lower parts of the pre-distillation tower 1, the pressure distillation tower 9, the atmospheric distillation tower 14, the recovery tower 17 and the secondary pressure distillation tower 10 are respectively provided with a pre-tower reboiler 21, a pressure tower reboiler 22, an atmospheric tower reboiler 23, a recovery tower reboiler 24 and a secondary pressure tower reboiler 25; the lower part of the negative pressure distillation tower 6 is provided with a negative pressure tower reboiler 1 32, a negative pressure tower reboiler 2 33 and a negative pressure tower reboiler 3 34; wherein, the gas phase at the top of the pre-distillation tower 1 is heated by the negative pressure tower reboiler 1 32, the gas phase at the top of the pressure distillation tower 9 is heated by the atmospheric tower reboiler 23 and the recovery tower reboiler 24, and the gas phase at the top of the atmospheric distillation tower 14 is heated by the negative pressure tower reboiler 2 33. Heat, the gas phase at the top of the recovery tower 17 is heated by the negative pressure tower reboiler 34, and the gas phase at the top of the secondary pressurized distillation tower 10 is heated by the pre-tower reboiler 21; the secondary pressurized tower reboiler 25 is connected to the heat input device, and the heat of the heat input device is used to heat the secondary pressurized tower reboiler 25, such as the heat of the synthesis reaction tower and the converter. In this embodiment, the synthesis gas of the methanol synthesis reaction tower is used to provide heat to the secondary pressurized tower reboiler 25 as an example for explanation: the pressurized tower reboiler 22 can be heated by low-pressure steam, or it can be connected to the heat input device, and the heat of other equipment is used to heat the pressurized tower reboiler 22. In this embodiment, low-pressure steam heating is used as an example:

[0062] The synthesis gas of the methanol synthesis reaction tower heats the medium, and the medium adopts methanol, water, heat transfer oil, etc. Taking methanol as an example, the formed methanol vapor supplies heat to the secondary pressure tower reboiler 25. The bottom of the synthesis reaction tower is connected to the heat exchanger 78 through the synthesis gas inlet pipeline 29, and the heat exchanger 78 is connected to the cooling device. The cooling device of this embodiment includes a cooler 26 connected to the heat exchanger 78, one input end of the cooler 26 is connected to the medium input pipeline 77, and the other output end of the cooler 26 is connected to the medium gas output pipeline 76, and the medium gas output pipeline 76 is connected to the secondary pressure tower reboiler 25; the medium gas output pipeline 76 determines whether to set the compressor 90 according to the situation; the cooler 26 and the cooler 27 and the cooler 3 28 are connected according to the situation. The output end of the cooler three 28 is connected to the input end of the synthesis gas processing device, and the output end of the synthesis gas processing device is connected to the pre-tower preheater one 3; preferably, a crude methanol buffer tank 97 is arranged between the output end of the synthesis gas processing device and the pre-tower preheater one 3; specifically, the synthesis gas processing device includes a condenser 30 connected to the cooler three 28 in sequence, the condenser 30 is connected to the high-pressure separator 79, the crude methanol filter, and the methanol flash tank 80 in sequence, the crude methanol filter includes a crude methanol primary filter 81 and a crude methanol secondary filter 82, the methanol flash tank 80 is connected to the crude methanol buffer tank 97 through the output pipeline 31, and the crude methanol buffer tank 97 is connected to the pre-tower preheater one 3 through the feed pipeline 2.

[0063] The specific utilization process of the heat of the synthesis reaction tower in this embodiment is as follows: the gas from the bottom of the synthesis reaction tower enters the tube side of the heat exchanger 78 for heat exchange, the pressure P after heat exchange in the heat exchanger 78 is 7.8MPag, the temperature T after heat exchange is 125℃-130℃, methanol enters the shell side of the cooler 26 as a cold medium, and the methanol is completely converted into gas phase after the heat exchange is completed, and the synthesis gas is cooled to 83℃ by controlling the feed amount of methanol, and the gas phase methanol gas is sent to the secondary pressure tower reboiler 25 through the medium gas output pipeline 76 to provide heat for the secondary pressure tower reboiler 25 and the secondary pressure tower reboiler 25. The distillation tower 10 provides the heat required for distillation, and the synthesis gas cooled by the cooler 26 continues to pass through the cooler 27, the cooler 3 28, and the condenser 30 to be condensed to about 40°C. After decompression and gas-liquid separation by the high-pressure separator 79, the obtained liquid phase is filtered by the crude methanol primary filter 81 and the crude methanol secondary filter 82, and then enters the methanol flash tank 80 for flash evaporation. The crude methanol obtained by flash evaporation enters the crude methanol buffer tank 97. The crude methanol coming out of the crude methanol buffer tank 97 is used as a raw material and enters the pre-tower preheater 3 through the feed pipeline 2 for preheating, and then enters the pre-distillation tower 1.

[0064] like Figure 2 As shown, the utilization of the heat at the top of each tower is described in detail, specifically:

[0065] The top of the pre-distillation tower 1 is connected to the negative pressure tower reboiler 32 through a pre-tower gas phase extraction pipeline 35, and the output end of the negative pressure tower reboiler 32 is connected to the pre-tower reflux device through a negative pressure tower reboiler output pipeline 36, and the pre-tower reflux device includes a pre-tower buffer tank 37, and the negative pressure tower reboiler output pipeline 36 is connected to the pre-tower buffer tank 37, and the bottom of the pre-tower buffer tank 37 is connected to the middle and upper part of the pre-distillation tower 1 through a pre-tower buffer tank reflux pipeline 38, and the pre-tower buffer tank reflux pipeline 38 is provided with a pre-tower reflux pump 39, and one side of the pre-tower buffer tank 37 is connected to an extraction water pipeline 41, and the top of the pre-tower buffer tank 37 is connected to a pre-tower condenser 94 through a buffer tank gas phase extraction pipeline 92, and the outlet of the pre-tower condenser 94 is connected to a pre-tower flash tank 93 through a pre-tower condenser outlet pipeline 95, and the top of the pre-tower flash tank 93 is connected with an un The condensed gas extraction pipeline 40, the bottom of the pre-tower flash tank 93 is connected to the pre-tower buffer tank 37 through the flash tank liquid phase extraction pipeline 96; the gas phase at the top of the pre-distillation tower 1 is used to supply the heat required for distillation for the negative pressure tower reboiler-32, and the material after heat exchange enters the pre-tower buffer tank 37. After the material in the pre-tower buffer tank 37 is extracted, the gas phase in the pre-tower buffer tank 37 enters the pre-tower condenser 94 through the buffer tank gas phase extraction pipeline 92 for condensation, and the obtained condensate enters the pre-tower flash tank 93 through the pre-tower condenser outlet pipeline 95, the non-condensable gas is extracted through the non-condensable gas extraction pipeline 40, and the liquid phase is extracted through the flash tank liquid phase extraction pipeline 96 and refluxed to the pre-tower buffer tank 37, and the liquid phase of the pre-tower buffer tank 37 refluxes to the pre-distillation tower 1; the heat at the top of the pre-distillation tower 1 is used to heat the negative pressure tower reboiler-32, and the heat required for part of the distillation is provided to the negative pressure distillation tower 6, thereby improving the utilization rate of heat.

[0066] The top of the negative pressure distillation tower 6 is provided with a negative pressure tower refined methanol extraction device for extracting refined methanol. Specifically, the negative pressure tower refined methanol extraction device includes a negative pressure tower reflux tank 42. The top of the negative pressure distillation tower 6 is connected to the negative pressure tower reflux tank 42 through a negative pressure tower gas phase pipeline 43. A negative pressure tower top condenser 44 is provided on the negative pressure tower gas phase pipeline 43. The bottom of the negative pressure tower reflux tank 42 is connected to the middle and upper part of the negative pressure distillation tower 6 through a negative pressure tower reflux pipeline 45. A negative pressure tower reflux pump 46 is provided on the tower reflux pipeline 45, and the negative pressure tower reflux pipeline 45 is connected to the negative pressure tower refined methanol production pipeline 47; the negative pressure tower refined methanol production pipeline 47 is connected to the refined methanol tank, and the refined methanol tank is used to store refined methanol; the gas phase produced from the top of the negative pressure distillation tower 6 is condensed by the negative pressure tower top condenser 44 and enters the negative pressure tower reflux tank 42, and part of the refined methanol in the negative pressure tower reflux tank 42 is refluxed to the negative pressure distillation tower 6 to improve the purity of the refined methanol; part of it is produced as refined methanol.

[0067] The top of the pressurized distillation tower 9 is connected to the atmospheric tower reboiler 23 and the recovery tower reboiler 24 respectively through the pressurized tower gas phase pipeline 48, and the output ends of the atmospheric tower reboiler 23 and the recovery tower reboiler 24 are connected to the pressurized tower refined methanol extraction device through the output pipeline 49. The pressurized tower refined methanol extraction device includes a pressurized tower reflux tank 50, and the output pipeline 49 is connected to the pressurized tower reflux tank 50. The bottom of the pressurized tower reflux tank 50 The pressure tower reflux pipeline 51 is connected to the middle and upper part of the pressure distillation tower 9, and the pressure tower reflux pipeline 51 is provided with a pressure tower reflux pump 52. The pressure tower reflux pipeline 51 is connected to the pressure tower refined methanol extraction pipeline 53, and the pressure tower refined methanol extraction pipeline 53 is connected to the refined methanol tank; the pressure tower refined methanol extraction pipeline 53 can be connected to the negative pressure tower refined methanol extraction pipeline 47, and the refined methanol extracted from the pressure distillation tower 9 and the negative pressure distillation tower 6 can be connected to the negative pressure tower refined methanol extraction pipeline 47. The methanol is mixed and enters the refined methanol tank; the gas phase at the top of the pressure distillation tower 9 exchanges heat with the atmospheric pressure tower reboiler 23 and the recovery tower reboiler 24, providing the atmospheric pressure distillation tower 14 and the recovery tower 17 with the heat required for distillation, and the materials after heat exchange enter the pressure tower reflux tank 50, and part of the refined methanol in the pressure tower reflux tank 50 is refluxed to the pressure distillation tower 9, and part of it is extracted as refined methanol; the heat at the top of the pressure distillation tower 9 is used to heat the atmospheric pressure tower reboiler 23 and the recovery tower The reboiler 24 supplies heat to provide the atmospheric distillation tower 14 and the recovery tower 17 with the heat required for distillation, thereby improving the utilization rate of heat; preferably, the output pipeline 49 is connected to the pressure tower reflux tank 50 after passing through the pre-tower preheater-3; the heat from the top of the pressure distillation tower 9 is exchanged with the atmospheric tower reboiler 23 and the recovery tower reboiler 24, and then with the pre-tower preheater-3, providing heat for the pre-tower preheater-3, thereby further improving the utilization rate of heat.

[0068] The top of the atmospheric distillation tower 14 is connected to the negative pressure tower reboiler 2 33 through the atmospheric pressure tower gas phase pipeline 54, and the negative pressure tower reboiler 2 33 is connected to the atmospheric pressure tower refined methanol extraction device through the negative pressure tower reboiler 2 output pipeline 55, and the atmospheric pressure tower refined methanol extraction device includes an atmospheric pressure tower reflux tank 56 connected to the negative pressure tower reboiler 2 output pipeline 55, and the bottom of the atmospheric pressure tower reflux tank 56 is connected to the middle and upper part of the atmospheric distillation tower 14 through the atmospheric pressure tower reflux pipeline 57, and the atmospheric pressure tower reflux pump 58 is provided on the atmospheric pressure tower reflux pipeline 57, and the atmospheric pressure tower reflux pipeline 57 is connected to the atmospheric pressure tower refined methanol extraction pipeline 59; the atmospheric pressure tower refined methanol extraction pipeline 59 is connected to the refined methanol tank; The refined methanol extraction pipeline 59 of the atmospheric pressure tower can be connected to the refined methanol extraction pipeline 47 of the negative pressure tower, and the refined methanol extracted from the pressure distillation tower 9, the negative pressure distillation tower 6, and the atmospheric pressure distillation tower 14 are mixed and then enter the refined methanol tank; the gas phase at the top of the atmospheric pressure distillation tower 14 exchanges heat with the negative pressure tower reboiler 2 33 to provide part of the heat required for distillation for the negative pressure distillation tower 6, and the material after heat exchange enters the atmospheric pressure tower reflux tank 56, and part of the refined methanol in the atmospheric pressure tower reflux tank 56 refluxes to the atmospheric pressure distillation tower 14, and part of it is extracted as refined methanol; the heat at the top of the atmospheric pressure distillation tower 14 is used to heat the negative pressure tower reboiler 2 33, to provide the negative pressure distillation tower 6 with the heat required for distillation, thereby improving the utilization rate of the heat at the top of the atmospheric pressure distillation tower 14.

[0069] The top of the recovery tower 17 is connected to the negative pressure tower reboiler three 34 through the recovery tower gas phase pipeline 60, the negative pressure tower reboiler three output pipeline 61 of the negative pressure tower reboiler three 34 is connected to the recovery tower refined methanol production device, the recovery tower refined methanol production device includes a recovery tower reflux tank 62 connected to the negative pressure tower reboiler three output pipeline 61, the bottom of the recovery tower reflux tank 62 is connected to the middle and upper part of the recovery tower 17 through the recovery tower reflux pipeline 63, the recovery tower reflux pipeline 63 is provided with a recovery tower reflux pump 64, the recovery tower reflux pipeline 63 is connected to the recovery tower refined methanol production pipeline 65; the recovery tower refined methanol production pipeline 65 is connected to the refined methanol tank; the recovery tower The refined methanol extraction pipeline 65 can be connected to the refined methanol extraction pipeline 47 of the negative pressure tower, and the refined methanol extracted from the pressure distillation tower 9, the negative pressure distillation tower 6, the atmospheric distillation tower 14, and the recovery tower 17 are mixed and then enter the refined methanol tank; the gas phase at the top of the recovery tower 17 exchanges heat with the negative pressure tower reboiler three 34, providing the negative pressure distillation tower 6 with part of the heat required for distillation, and the material after heat exchange enters the recovery tower reflux tank 62, and part of the refined methanol in the recovery tower reflux tank 62 is refluxed to the recovery tower 17, and part of it is extracted as refined methanol; the heat at the top of the recovery tower 17 is used to heat the negative pressure tower reboiler three 34, providing the negative pressure distillation tower 6 with the heat required for distillation, thereby improving the utilization rate of the heat at the top of the recovery tower 17.

[0070] The top of the secondary pressure distillation tower 10 is connected to the pre-tower reboiler 21 through the secondary pressure tower gas phase pipeline 66, the pre-tower reboiler output pipeline 67 of the pre-tower reboiler 21 is connected to the secondary pressure tower refined methanol production device, the secondary pressure tower refined methanol production device includes a secondary pressure tower reflux tank 68 connected to the pre-tower reboiler output pipeline 67, the bottom of the secondary pressure tower reflux tank 68 is connected to the secondary pressure distillation tower 10 through a secondary pressure tower reflux pipeline 69, a secondary pressure tower reflux pump 70 is provided on the secondary pressure tower reflux pipeline 69, the secondary pressure tower reflux pipeline 69 is connected to the secondary pressure tower refined methanol production pipeline 71; the secondary pressure tower refined methanol production pipeline 71 is connected to the refined methanol tank; the secondary pressure tower refined methanol production pipeline Line 71 can be connected to the negative pressure tower refined methanol extraction pipeline 47, and the refined methanol extracted from the pressure distillation tower 9, the negative pressure distillation tower 6, the atmospheric distillation tower 14, the recovery tower 17, and the secondary pressure distillation tower 10 are mixed and enter the refined methanol tank; the gas phase at the top of the secondary pressure distillation tower 10 exchanges heat with the pre-tower reboiler 21 to provide the heat required for distillation for the pre-distillation tower 1, and the material after heat exchange enters the secondary pressure tower reflux tank 68, and part of the refined methanol in the secondary pressure tower reflux tank 68 is refluxed to the secondary pressure distillation tower 10, and part of it is extracted as refined methanol; the heat at the top of the secondary pressure distillation tower 10 is used to heat the pre-tower reboiler 21, to provide the heat required for distillation for the pre-distillation tower 1, thereby improving the utilization rate of the heat at the top of the secondary pressure distillation tower 10.

[0071] The pressure tower reboiler 22 provides heat through low-pressure steam. Specifically, the pressure tower reboiler 22 is connected to the low-pressure steam input pipeline 72, the pressure tower reboiler output pipeline 73 of the pressure tower reboiler 22 is connected to the pressure tower preheater 12, the output end of the pressure tower preheater 12 is connected to the pre-tower preheater 4 through the preheater 2 output pipeline 74, and the output end of the pre-tower preheater 4 is connected to the steam reflux pipeline 75.

[0072] This embodiment integrates the synthesis gas generated by the methanol synthesis reaction tower into the distillation system, and uses the primary recovered heat of the synthesis reaction tower to heat the secondary pressure tower reboiler 25, thereby achieving greater energy saving and carbon reduction benefits; adopts a six-tower thermal coupling process, optimizes the heat exchange network, and increases energy saving space; compared with the traditional methanol process, the steam unit consumption can be reduced to 0.35-0.38t steam / t refined alcohol; and the present application can produce methanol with a concentration of >99.99% and an ethanol content of 10-100ppm.

[0073] Embodiment 4:

[0074] In this embodiment, the top pressure of the pre-distillation tower 1 is 120-180 kPa, the top pressure of the atmospheric distillation tower 14 is 103-120 kPa, the top pressure of the secondary pressure distillation tower 10 is 200-355 kPa, the top pressure of the negative pressure distillation tower 6 is 40-70 kPa, and the top pressure of the pressure distillation tower 9 is 600-800 kPa.

[0075] The difference between this embodiment and embodiment one lies in that a pre-tower reboiler 21 and a pre-tower reboiler 83 are provided at the lower portion of the pre-distillation tower 1, and a pressure tower reboiler 22 and a pressure tower reboiler 84 are provided at the lower portion of the pressurized distillation tower 9; the gas phase at the top of the pressurized distillation tower 9 supplies heat to the pre-tower reboiler 83, the atmospheric pressure tower reboiler 23 and the recovery tower reboiler 24 respectively; specifically: the top of the pressurized distillation tower 9 is connected to the pre-tower reboiler 83, the atmospheric pressure tower reboiler 23 and the recovery tower reboiler 24 respectively through the pressurized tower gas phase pipeline 48, and the output ends of the pre-tower reboiler 83, the atmospheric pressure tower reboiler 23 and the recovery tower reboiler 24 are connected to the pressurized tower refined methanol extraction device through the output pipeline 49, and the pressurized tower refined methanol extraction device is as described in embodiment one and will not be described in detail here.

[0076] In this embodiment, the secondary pressure tower reboiler 25 is heated by the secondary recovery heat and the tertiary recovery heat of the synthesis reaction tower, the pressure tower reboiler 1 22 is heated by low-pressure steam, and the pressure tower reboiler 2 84 is heated by the primary recovery heat of the synthesis reaction tower, specifically:

[0077] The secondary pressure tower reboiler 25 is connected to the methanol gas output main pipeline 85, and the methanol gas output main pipeline 85 is respectively connected to the medium gas output pipeline 2 86 and the medium gas output pipeline 3 87. The medium gas output pipeline 2 86 and the medium gas output pipeline 3 87 can be respectively provided with compressor 2 88 and compressor 3 89. The pressure tower reboiler 2 84 is connected to the medium gas output pipeline 76, and the medium gas output pipeline 76 can be provided with compressor 1 90.

[0078] The specific utilization process of the heat of the synthesis reaction tower in this embodiment is as follows: the gas coming out of the bottom of the synthesis reaction tower enters the tube side of the heat exchanger 78 for heat exchange, and methanol enters the shell side of the cooler 26 as a cold medium. After the heat exchange is completed, all the methanol is converted into a gas phase, and the synthesis gas is cooled to a corresponding temperature by controlling the feed amount of methanol. The gaseous methanol gas is sent to the pressure tower reboiler 284 through the medium gas output pipeline 76 to provide heat for the pressure tower reboiler 284 and provide the heat required for distillation for the pressurized distillation tower 9. The synthesis gas cooled by the cooler 26 continues to be cooled by the cooler 27, and methanol enters the shell side of the cooler 27 as a cold medium. After the heat exchange is completed, all the methanol is converted into a gas phase, and the synthesis gas is cooled to a corresponding temperature by controlling the feed amount of methanol. The gaseous methanol gas is sent to the secondary pressure tower reboiler 25 through the medium gas output pipeline 286 to provide heat for the secondary pressure tower reboiler 26. 25 for heating; the synthesis gas cooled by cooler two 27 is further cooled by cooler three 28, and methanol enters the shell side of cooler three 28 as a cold medium. After the heat exchange is completed, all the methanol is converted into gas phase, and the synthesis gas is cooled to the corresponding temperature by controlling the methanol feed amount, and the gas phase methanol gas is sent to the secondary pressure tower reboiler 25 through the medium gas output pipeline three 87 to provide heat for the secondary pressure tower reboiler 25; the synthesis gas cooled by cooler three 28 is further condensed by the condenser 30, and after the high-pressure separator 79 reduces pressure and separates gas and liquid, the obtained liquid phase is filtered by the crude methanol primary filter 81 and the crude methanol secondary filter 82, and then enters the methanol flash tank 80 for flash evaporation, and the crude methanol obtained by flash evaporation enters the crude methanol buffer tank 97. The crude methanol coming out of the crude methanol buffer tank 97 is used as a raw material and enters the pre-tower preheater one 3 through the feed pipeline 2 for preheating, and then enters the pre-distillation tower 1.

[0079] Through this embodiment, the unit consumption of methanol distillation can be reduced from 1.2t steam / t refined alcohol to 0.12-0.15t steam / t refined alcohol, which can save more than 70% energy compared with the traditional double-tower thermal coupling process, and the output can be increased by more than 50%, which greatly reduces the operating costs for enterprises, significantly reduces carbon emissions and improves the competitiveness of enterprises; this embodiment integrates the heat of the synthesis gas generated by the methanol synthesis tower into the distillation system, thereby achieving greater energy-saving and carbon-reduction benefits; adopts a six-tower thermal coupling process, optimizes the heat exchange network, and increases energy-saving space; and this application can produce methanol with a concentration of >99.99% and an ethanol content of less than 50ppm 。

[0080] Embodiment five:

[0081] This embodiment provides a specific application scenario of Embodiment 3:

[0082] In a methanol plant, a new crude methanol refining and recovery unit with an annual output of 600,000 tons was installed, with a feed rate of 78,750 kg / h. When the process-related parameters were optimized to the best, the steam energy consumption of refined methanol was about 0.35 tons of steam / refined methanol through the six-tower thermal coupling process, of which the methanol purity could reach more than 99.99% and the ethanol content was less than 50 pp m.

[0083] The following is combined with Figure 2 This implementation method is described in detail:

[0084] The crude methanol enters the pre-tower preheater 3 and the pre-tower preheater 4 in sequence for preheating, and finally the crude methanol is preheated to about 85°C. The preheated crude methanol enters the pre-distillation tower 1 for distillation. The top pressure of the pre-distillation tower 1 is 127KPa, the top temperature is 71°C, and the bottom temperature is 72°C. The gas phase extracted from the top of the pre-distillation tower 1 goes to the negative pressure tower reboiler 32 to provide the heat required for distillation to the negative pressure distillation tower 6, and after being cooled by the negative pressure tower reboiler 32, it enters the pre-tower buffer tank 37, and is extracted in the pre-tower buffer tank 37. The gas phase produced after extraction enters the pre-tower condenser 94 for condensation, and the obtained condensate enters the pre-tower flash tank 93, the produced non-condensable gas is discharged, and the liquid phase refluxes to the pre-tower buffer tank 37, and the liquid phase in the pre-tower buffer tank 37 refluxes to the pre-distillation tower 1; specifically, it is pressurized by the pre-tower reflux pump 39 and sent to the upper and middle part of the pre-distillation tower 1 as reflux feed; the pre-tower reboiler 21 provides the heat required for the pre-tower distillation 1 in the form of indirect heating, wherein the heat source of the pre-tower reboiler 21 is the gas phase extracted from the top of the secondary pressurized distillation tower 10.

[0085] The liquid phase extracted from the bottom of the pre-distillation tower 1 enters the negative pressure distillation tower 6 for distillation. The top pressure of the negative pressure distillation tower 6 is 60KPa, the top temperature is 52°C, and the bottom temperature is 56°C. The gas phase extracted from the top of the negative pressure distillation tower 6 enters the negative pressure tower reflux tank 42 after condensation by the negative pressure tower top condenser 44. The liquid phase of the negative pressure tower reflux tank 42 is pressurized by the negative pressure tower reflux pump 46 and is divided into two streams, one of which refluxes to the negative pressure distillation tower 6, that is, refluxes to the middle and upper part of the negative pressure distillation tower 6 as the reflux into material, and another stream of refined methanol; the negative pressure tower reboiler provides the heat required for distillation of the negative pressure distillation tower 6 in the form of indirect heating, and the negative pressure tower reboiler includes a negative pressure tower reboiler 1 32, a negative pressure tower reboiler 2 33, and a negative pressure tower reboiler 3 34, wherein the heat source of the negative pressure tower reboiler 1 32 is the gas phase extracted from the top of the pre-distillation tower 1, the heat source of the negative pressure tower reboiler 2 33 is the gas phase extracted from the top of the atmospheric distillation tower 14, and the heat source of the negative pressure tower reboiler 3 34 is the gas phase extracted from the top of the recovery tower 17.

[0086] The bottom liquid of the negative pressure distillation tower 6 is divided into two streams after being pressurized by a pump, and enters the pressure distillation tower 9 and the secondary pressure distillation tower 10 for further distillation respectively; the top pressure of the pressure distillation tower 9 is 630KPa, the top temperature is 120°C, and the bottom temperature is 124°C. The gas phase extracted from the top of the pressure distillation tower 9 is divided into two streams, one stream goes to the atmospheric pressure tower reboiler 23 to provide the heat required for distillation for the atmospheric pressure distillation tower 14, and the other stream goes to the recovery tower reboiler 24 to provide the heat required for distillation for the recovery tower 17; the two streams are combined and the feed stream of the pre-distillation tower 1 is fed through the pre-tower preheater 3. It is preliminarily preheated and then goes to the pressurized tower reflux tank 50. The liquid phase in the pressurized tower reflux tank 50 is divided into two streams, one of which is pressurized by the pressurized tower reflux pump 52 and then enters the upper and middle part of the pressurized distillation tower 9 as reflux feed, and the other is extracted with refined methanol; the pressurized distillation tower 9 provides the heat required for distillation of the pressurized distillation tower 9 in the form of indirect heating by the reboiler, and the heat of the pressurized tower reboiler 22 comes from the low-pressure steam. The outlet stream of the pressurized distillation tower 9 is preliminarily preheated by the pressurized tower preheater 11 to the pressurized distillation tower 9 feed stream, and the pressurized tower reboiler 22 provides heat by low-pressure steam.

[0087] The top pressure of the secondary pressurized distillation tower 10 is 200KPa, the top temperature is 83°C, and the bottom temperature is 91°C. The gas phase at the top of the secondary pressurized distillation tower 10 goes to the pre-tower reboiler 21 to provide the heat required for distillation for the pre-distillation tower 1, and then enters the secondary pressurized tower reflux tank 68. The liquid phase in the secondary pressurized tower reflux tank 68 is divided into two streams, one of which refluxes to the secondary pressurized distillation tower 10, that is, flows into the middle and upper part of the secondary pressurized distillation tower 10 as reflux feed, and the other extracts refined methanol; the secondary pressurized distillation tower 10 provides the heat required for distillation of the secondary pressurized distillation tower 10 in the form of indirect heating by the secondary pressurized tower reboiler 25, and the required heat of the secondary pressurized tower reboiler 25 comes from the primary heat recovery of the synthesis gas at the outlet of the synthesis reaction tower.

[0088] The extracted streams from the bottom of the pressure distillation tower 9 and the secondary pressure distillation tower 10 are combined into one stream, and then the stream enters the atmospheric distillation tower 14 for further distillation. The top pressure of the atmospheric distillation tower 14 is 120KPa, the top temperature is 69°C, and the bottom temperature is 108°C. The gas phase at the top of the atmospheric distillation tower 14 goes to the negative pressure tower reboiler 23 to provide the heat required for distillation for the negative pressure distillation tower 6, and then enters the atmospheric pressure tower reflux tank 56. The refined methanol in the atmospheric pressure tower reflux tank 56 is divided into two streams, one of which refluxes to the atmospheric pressure distillation tower 14, that is, flows into the middle and upper part of the atmospheric pressure distillation tower 14 as reflux feed, and the other extracts refined methanol; the heat source of the atmospheric pressure tower reboiler 23 is the gas phase extracted from the top of the pressure distillation tower 9, the side line of the atmospheric distillation tower 14 extracts fusel alcohol, and the bottom extracts waste water.

[0089] The fusel alcohol produced by the atmospheric tower side production line 16 enters the recovery tower 17 to recover the remaining methanol; the top pressure of the recovery tower 17 is 109KPa, the top temperature is 67°C, and the bottom temperature is 105°C. The gas phase at the top of the recovery tower 17 goes to the negative pressure tower reboiler 34 to provide the heat required for distillation for the negative pressure distillation tower 6, and then enters the recovery tower reflux tank 62. The refined methanol in the recovery tower reflux tank 62 is divided into two streams, one of which refluxes to the middle and upper part of the recovery tower 17 as reflux feed, and the other extracts refined methanol; the heat source of the recovery tower reboiler 24 is the gas phase extracted from the top of the pressurized distillation tower 9, the fusel alcohol production pipeline 19 of the recovery tower 17 produces fusel alcohol, and the bottom produces waste water.

[0090] In this embodiment, the heat source of the pressure tower reboiler 22 is low-pressure steam, and the methanol vapor at the top of the pressure distillation tower 9 supplies heat to the atmospheric pressure tower reboiler 23 and the recovery tower reboiler 24 respectively; the heat source of the secondary pressure tower reboiler 25 adopts the steam at the outlet of the synthesis reaction tower to recover heat once, and the methanol vapor at the top of the secondary pressure distillation tower 10 supplies heat to the pre-tower reboiler 21, and the methanol vapor at the top of the pre-distillation tower 1, the atmospheric distillation tower 14 and the recovery tower 17 supplies heat to the negative pressure tower reboiler, and the energy consumption per ton of refined methanol is about 0.35t of steam.

[0091] In this embodiment, the feed rate of crude methanol is 78750 kg / h, wherein the water content is 3.80%, and the ethanol content is about 0.23%. The crude methanol is preheated to 85° C. by pre-tower preheater 1 and pre-tower preheater 2 and then enters the pre-distillation tower. The operating parameters of each tower are shown in Table 1 below:

[0092]

[0093] Table 1

[0094] In summary, the distillation (cocurrent double-effect distillation) process of this embodiment expands the capacity by more than 50%, while reducing the steam consumption by 50%-65%; for the new market, the investment is small, the operability is strong, and the energy-saving measures such as heat recovery are adopted to optimize the heat exchange network, which greatly reduces the steam consumption, and the consumption per ton of methanol can be reduced to 0.35 tons of steam / ton of refined methanol.

[0095] Embodiment six:

[0096] This embodiment provides a specific application scenario of Embodiment 4:

[0097] In a methanol plant, a new crude methanol refining and recovery unit with an annual output of 600,000 tons was installed with a feed rate of 78,750 kg / h. When the process-related parameters were optimized to the best, the steam energy consumption of refined methanol was about 0.119 tons of steam / refined methanol through the six-tower thermal coupling process, of which the methanol purity could reach more than 99.99% and the ethanol content was less than 50 ppm.

[0098] The following is combined with Figure 4This implementation method is described in detail:

[0099] The crude methanol enters the pre-tower preheater-3 and the pre-tower preheater-4 for preheating. The pre-tower preheater-3 and the pre-tower preheater-4 preheat the crude methanol to about 64°C. The preheated crude methanol enters the pre-distillation tower 1 for distillation. The top pressure of the pre-distillation tower 1 is 127KPag, the top temperature is 71°C, and the bottom temperature is 72°C. The gas phase extracted from the top of the pre-distillation tower 1 goes to the negative pressure tower reboiler-32 to provide the heat required for distillation to the negative pressure distillation tower 6. The gas phase in the pre-distillation tower 1 is cooled and then enters the pre-tower buffer tank 37. The gas phase generated after extraction in the pre-tower buffer tank 37 enters the pre-tower condenser 94 for cooling. The condensate obtained enters the pre-tower flash tank 93, the generated non-condensable gas is discharged, and the liquid phase flows back to the pre-tower buffer tank 37, and the liquid phase in the pre-tower buffer tank 37 flows back to the pre-distillation tower 1; specifically, it is pressurized by the pre-tower reflux pump 39 and sent to the upper and middle part of the pre-distillation tower 1 as reflux feed; the pre-distillation tower 1 provides the heat required for the distillation of the pre-distillation tower 1 through the pre-tower reboiler 21 and the pre-tower reboiler-83 indirect heating, wherein the heat source of the pre-tower reboiler 21 is the gas phase extracted from the top of the secondary pressure distillation tower 10; the heat source of the pre-tower reboiler-83 is the gas phase extracted from the top of the pressure distillation tower 9.

[0100] The liquid phase extracted from the bottom of the pre-distillation tower 1 enters the negative pressure distillation tower 6 for distillation. The top pressure of the negative pressure distillation tower 6 is 60KPa, the top temperature is 52°C, and the bottom temperature is 56°C. The gas phase extracted from the top of the negative pressure distillation tower 6 enters the negative pressure tower reflux tank 42 after condensation by the negative pressure tower top condenser 44. The liquid phase of the negative pressure tower reflux tank 42 is pressurized by the negative pressure tower reflux pump 46 and is divided into two streams, one of which refluxes to the negative pressure distillation tower 6, that is, refluxes to the negative pressure distillation tower 6. The middle and upper parts are used as reflux feed, and the other stream is used to produce refined methanol through the negative pressure tower refined methanol production pipeline 47; the negative pressure distillation tower 6 provides the heat required for distillation of the negative pressure distillation tower through indirect heating of the negative pressure tower reboiler, wherein the heat source of the negative pressure tower reboiler 1 32 is the gas phase produced from the top of the pre-distillation tower 1; the heat source of the negative pressure tower reboiler 2 33 is the gas phase produced from the top of the atmospheric distillation tower 14; the heat source of the negative pressure distillation tower reboiler 3 34 is the gas phase produced from the top of the recovery tower 17.

[0101] The bottom liquid of the negative pressure distillation tower 6 is pressurized by a pump and divided into two streams, which respectively enter the pressure distillation tower 9 and the secondary pressure distillation tower 10 for further distillation.

[0102] The top pressure of the pressurized distillation tower 9 is 630KPa, the top temperature is 120℃, and the bottom temperature is 125℃. The gas phase extracted from the top of the pressurized distillation tower 9 is divided into three streams, one stream goes to the pre-tower reboiler 83 to provide the heat required for distillation for the pre-distillation tower 1; the second stream goes to the atmospheric pressure tower reboiler 23 to provide the heat required for distillation for the atmospheric pressure distillation tower 14; the third stream goes to the recovery tower reboiler 24 to provide the heat required for distillation for the recovery tower 17; the three streams are gathered, and the feed stream of the pre-distillation tower 1 is preliminarily preheated by the pre-tower preheater 3, and then goes to the pressurized tower reflux tank 50, and the liquid phase in the pressurized tower reflux tank 50 is divided into two streams, one stream is pressurized by the pressurized tower reflux pump 52 and then enters the top of the pressurized distillation tower 9 as reflux feed, and the other stream is extracted with refined methanol ; The pressurized distillation tower 9 provides the heat required for distillation of the pressurized distillation tower 9 in the form of indirect heating by the pressurized tower reboiler 22. The heat of the pressurized tower reboiler 22 comes from the low-pressure steam, and the heat of the pressurized tower reboiler 284 comes from the primary heat recovery of the synthesis gas at the outlet of the synthesis reaction tower; the output stream of the pressurized distillation tower 9 is preliminarily preheated by the pressurized tower preheater 11 to the feed stream of the pressurized distillation tower 9, and the steam condensate generated by the pressurized tower reboiler 22 is further preheated to 100°C by the pressurized tower preheater 212, and the preheated stream enters the pressurized distillation tower 9; the steam condensate after cooling is further preheated to 64°C for the crude methanol raw material by the pre-tower preheater 24, and the preheated crude methanol raw material enters the pre-distillation tower 1.

[0103] The top pressure of the secondary pressurized distillation tower 10 is 200KPa, the top temperature is 83°C, and the bottom temperature is 90°C. The gas phase at the top of the secondary pressurized distillation tower 10 goes to the pre-tower reboiler 21 to provide the heat required for distillation for the pre-distillation tower 1, and then enters the secondary pressurized tower reflux tank 68. The refined methanol in the secondary pressurized tower reflux tank 68 is divided into two streams, one of which refluxes to the secondary pressurized distillation tower 10, that is, flows into the middle and upper part of the secondary pressurized distillation tower 10 as reflux feed, and the other extracts refined methanol; the secondary pressurized distillation tower 10 provides the heat required for distillation of the secondary pressurized distillation tower 10 in the form of indirect heating by the secondary pressurized tower reboiler 25, and the heat of the secondary pressurized tower reboiler 25 comes from the secondary and tertiary recovery heat of the synthesis gas at the outlet of the synthesis reaction tower, specifically the methanol gas obtained after heat exchange of the synthesis gas of the synthesis reaction tower.

[0104] The streams extracted from the bottom of the pressure distillation tower 9 and the secondary pressure distillation tower 10 are combined into one stream, and then the streams enter the atmospheric distillation tower 14 for further distillation. The top pressure of the atmospheric distillation tower 14 is 120KPa, the top temperature is 69°C, and the bottom temperature is 108°C. The gas phase at the top of the atmospheric distillation tower 14 goes to the negative pressure tower reboiler 23 to provide the heat required for distillation for the negative pressure distillation tower 6, and then enters the atmospheric tower reflux tank 56. The refined methanol in the atmospheric tower reflux tank 56 is divided into two streams, one of which refluxes to the atmospheric distillation tower 14, that is, flows into the middle and upper part of the atmospheric distillation tower 14 as reflux feed, and the other extracts refined methanol; the heat source of the atmospheric tower reboiler 23 is the gas phase extracted from the top of the pressure distillation tower 9, the atmospheric tower side extraction pipeline 16 of the atmospheric distillation tower 14 extracts fusel alcohol, and the bottom extracts waste water.

[0105] The fusel alcohol produced by the atmospheric tower side production pipeline 16 enters the recovery tower 17 to recover the remaining methanol. The top pressure of the recovery tower 17 is 109 KPa, the top temperature is 67°C, and the bottom temperature is 101°C. The gas phase at the top of the recovery tower 17 goes to the negative pressure tower reboiler 34 to provide the heat required for distillation for the negative pressure distillation tower 6, and then enters the recovery tower reflux tank 62. The refined methanol in the recovery tower reflux tank 62 is divided into two streams, one of which refluxes to the middle and upper part of the recovery tower 17 as reflux feed, and the other extracts refined methanol; the heat source of the recovery tower reboiler 24 is the gas phase extracted from the top of the pressurized distillation tower 9, the recovery tower side line 19 of the recovery tower 17 extracts fusel alcohol, and the bottom extracts waste water.

[0106] In this embodiment, the heat source of the pressure tower reboiler 2 84 adopts the synthesis gas at the outlet of the synthesis reaction tower to recover heat once, the heat source of the pressure tower reboiler 1 22 adopts low-pressure steam, and the methanol vapor at the top of the pressure distillation tower 9 provides heat to the pre-tower reboiler 1 83, the atmospheric pressure tower reboiler 23 and the recovery tower reboiler 24 respectively; the heat source of the secondary pressure tower reboiler 25 adopts the synthesis gas at the outlet of the synthesis reaction tower to recover heat twice and tertiary times; the methanol vapor at the top of the pre-distillation tower 1, the atmospheric pressure distillation tower 14 and the recovery tower 17 provides heat to the negative pressure tower reboiler 1 32, the negative pressure tower reboiler 2 33 and the negative pressure tower reboiler 3 34 respectively, and the energy consumption per ton of refined methanol is about 0.119t of steam.

[0107] In this embodiment, the feed rate of crude methanol is 78750 kg / h, wherein the water content is 3.80%, and the ethanol content is about 0.23%. The crude methanol is preheated to 64° C. by pre-tower preheater 1 3 and pre-tower preheater 2 4 and then enters the pre-distillation tower 1. The operating parameters of each tower are shown in Table 2 below:

[0108]

[0109]

[0110] Table 2

[0111] The purpose of the distillation (cocurrent double-effect distillation) process is to expand the capacity by more than 50% and reduce steam consumption by 50%-65% at the same time; for the new market, the investment is small and the operability is strong. The use of energy-saving measures such as heat exchange network optimization heat recovery has greatly reduced steam consumption, and the consumption per ton of methanol can be reduced to 0.12 tons of steam / ton of refined methanol.

[0112] The present application achieves greater energy conservation and carbon reduction benefits by integrating the heat of the synthesis gas generated by the methanol synthesis tower into the distillation system; adopts a six-tower thermal coupling process, optimizes the heat exchange network, and increases energy conservation space; compared with the traditional methanol process, the steam consumption per unit can be reduced; and the present application can produce methanol with a concentration of >99.99%.

[0113] The devices, connection relationships, etc. not specifically described above all belong to the prior art and will not be described in detail in the present invention.

[0114] The preferred embodiments of the present application are described in detail above in conjunction with the accompanying drawings; however, the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, a variety of simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the protection scope of the present application.

[0115] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the various possible combinations of this application will not be described separately.

[0116] In addition, the various implementation modes of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed in the present application.

Claims

1. A six-tower multi-effect distillation process for crude methanol, characterized in that: The steps include: The crude methanol enters the pre-distillation tower (1), and the liquid phase extracted from the bottom of the pre-distillation tower (1) enters the negative pressure distillation tower (6) for distillation; The liquid phase extracted from the bottom of the negative pressure distillation tower (6) enters the pressure distillation tower (9) and the secondary pressure distillation tower (10) for distillation respectively; The liquid phase extracted from the bottom of the pressure distillation tower (9) is mixed with the liquid phase extracted from the bottom of the secondary pressure distillation tower (10) and then enters the atmospheric distillation tower (14); The waste water is extracted from the bottom of the atmospheric distillation tower (14), and the fusel alcohol extracted from one side of the atmospheric distillation tower (14) enters the recovery tower (17); Fusel alcohol is produced from one side of the recovery tower (17), and waste water is produced from the bottom of the recovery tower (17); The pressure tower reboiler provides heat through low-pressure steam or a heat input device, and the sub-pressure tower reboiler (25) recovers heat through a heat input device to provide heat.

2. A six-tower multiple-effect distillation process for crude methanol according to claim 1, characterized in that: The gas phase at the top of the secondary pressure distillation tower (10) provides heat to the pre-tower reboiler (21).

3. A six-tower multiple-effect distillation process for crude methanol according to claim 1, characterized in that: The heat input device adopts a synthesis reaction tower. The synthesis gas extracted from the bottom of the synthesis reaction tower enters the heat exchanger (78) tube for heat exchange, and enters the cooling device after heat exchange. The cooling medium is introduced into an input end of the cooling device, and an output end of the cooling device is connected to the secondary pressure tower reboiler (25), or is connected to the secondary pressure tower reboiler (25) and the pressure tower reboiler.

4. A six-tower multiple-effect distillation process for crude methanol according to claim 3, characterized in that: The synthesis gas extracted from the bottom of the synthesis reaction tower enters the tube side of the heat exchanger (78) for heat exchange, and after the heat exchange, it enters the cooler (26), the second cooler (27), and the third cooler (28) in sequence. A cold medium is introduced into the shell side of the cooler (26), the second cooler (27), and the third cooler (28). After the synthesis gas heat exchange, the cold medium entering the cooler (26), the second cooler (27), and the third cooler (28) is completely converted into a gas phase, and at least one gas phase is sent to the reboiler (25) of the secondary pressure tower and / or the reboiler of the pressure tower.

5. A six-tower multiple-effect distillation process for crude methanol according to claim 4, characterized in that: The gas phase is compressed and sent to the secondary pressure tower reboiler (25) and / or the pressure tower reboiler.

6. A six-tower multiple-effect distillation process for crude methanol according to claim 4, characterized in that: The synthesis gas cooled by cooler 3 (28) is further condensed by condenser (30), and after condensation, it is decompressed by high-pressure separator (79), and the liquid phase obtained after gas-liquid separation is filtered by crude methanol filter, and then enters methanol flash tank (80) for flash evaporation. The crude methanol obtained by flash evaporation is sent to pre-distillation tower (1) as raw material.

7. A six-tower multi-effect distillation device for crude methanol, comprising a pre-distillation tower (1), characterized in that: The rear part of the pre-distillation tower (1) is connected in sequence with a negative pressure distillation tower (6), a pressure distillation tower (9), an atmospheric pressure distillation tower (14), and a recovery tower (17); the pressure distillation tower (9) and the secondary pressure distillation tower (10) are arranged in parallel, or the secondary pressure distillation tower (10) is arranged between the negative pressure distillation tower (6) and the pressure distillation tower (9), or the secondary pressure distillation tower (10) is arranged between the pressure distillation tower (9) and the atmospheric pressure distillation tower (14); a secondary pressure tower reboiler (25) is arranged at the lower part of the secondary pressure distillation tower (10), and the secondary pressure tower reboiler (25) is connected to a heat input device.

8. A six-tower multiple-effect distillation device for crude methanol according to claim 7, characterized in that: The top of the secondary pressure distillation tower (10) is connected to the pre-tower reboiler (21).

9. A six-tower multiple-effect distillation device for crude methanol according to claim 7, characterized in that: The pressure tower reboiler arranged at the bottom of the pressure distillation tower (9) is connected to a low-pressure steam device and / or a heat input device.

10. A six-tower multiple-effect distillation device for crude methanol according to claim 7 or 9, characterized in that: The heat input device adopts a synthesis reaction tower.

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