Six-tower mixed four-effect negative pressure heat pump assisted methanol rectification energy-saving device and method
By using a six-tower mixed-direction four-effect double heat trap assisted methanol distillation unit and negative pressure heat pump technology, heat utilization is optimized, solving the problem of high energy consumption in methanol distillation and achieving significant energy saving and production expansion effects.
Patent Information
- Application Number
- CN202510942895.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-09
- Publication Date
- 2025-11-14
AI Technical Summary
Existing methanol distillation units have high energy consumption, accounting for about 20% of the total production energy consumption. The traditional three-tower double-effect scheme still requires a large heat source, resulting in persistently high energy consumption.
A six-tower mixed-direction four-effect double heat trap assisted methanol distillation unit is adopted, combined with negative pressure heat pump technology. Through top vapor recompression and multi-effect distillation, heat utilization is optimized, the operating pressure and reflux ratio of each tower are reduced, and efficient heat recycling is achieved.
It significantly reduces the unit consumption of refined methanol production, increases the process capacity by 20% to 50%, reduces the unit consumption of refined methanol production to 0.55 to 0.65 steam consumption, miniaturizes tower equipment, and increases product yield.
Smart Images
Figure CN120939595A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of distillation technology, specifically to a six-tower mixed-direction four-effect negative pressure heat pump-assisted methanol distillation energy-saving device and method. Background Technology
[0002] Methanol is an important basic organic chemical raw material and fuel resource with excellent properties. It has wide applications in organic synthesis, dyes, pharmaceuticals, pesticides, coatings, transportation, and defense industries, ranking fourth in global chemical raw material consumption. With the continuous development of modern science and technology and the global energy structure, new methods for producing high-purity methanol are constantly emerging, but distillation remains the preferred method for improving methanol purity. However, distillation has a relatively high overall energy consumption, accounting for approximately 20% of the total energy consumption in methanol production. Therefore, technologies to reduce the energy consumption of methanol distillation play a crucial role in reducing methanol production costs and improving the economic benefits for enterprises. Currently, the three-tower double-effect methanol distillation scheme has been widely used in industrial methanol production in my country. This scheme uses pressurized tower top steam to drive the atmospheric tower reboiler. The atmospheric tower does not require saturated steam, but the pre-distillation tower reboiler still requires saturated steam as a heat source. Therefore, the energy consumption of the methanol distillation unit remains at a relatively high level. Summary of the Invention
[0003] To address the problems in the background art, this invention proposes an energy-saving device and method for methanol distillation with six-tower mixed-direction four-effect double heat trap.
[0004] The technical solution of the present invention is a six-tower mixed-direction four-effect double heat trap assisted methanol distillation energy-saving device, comprising a pre-distillation tower (T1), a negative pressure distillation tower (T2), a medium pressure distillation tower (T3), a pressurized distillation tower (T4), an atmospheric pressure distillation tower (T5), and a methanol recovery tower (T6) connected in sequence. The lower part of the pre-distillation tower (T1) is connected to a pre-distillation tower reboiler (R1), the lower part of the negative pressure distillation tower (T2) is connected to a negative pressure distillation tower reboiler (R2), the lower part of the medium pressure distillation tower (T3) is connected to a medium pressure distillation tower reboiler (R3), the lower part of the pressurized distillation tower (T4) is connected to a pressurized distillation tower reboiler (R4), the lower part of the atmospheric pressure distillation tower (T5) is connected to an atmospheric pressure distillation tower reboiler (R5), and the lower part of the methanol recovery tower (T6) is connected to a methanol recovery tower reboiler (R6).
[0005] The overhead gas from the pre-distillation column (T1) heats the reboiler (R2) of the negative pressure distillation column; the overhead steam from the medium-pressure distillation column (T3) heats the reboiler (R1) of the pre-distillation column.
[0006] One branch of gas from the top of the pressurized distillation column (T4) heats the reboiler (R3) of the medium-pressure distillation column, and the heated stream flows back to the top of the pressurized distillation column (T4). The other branch of gas heats the reboiler (R5) of the atmospheric distillation column, and the heated stream flows back to the top of the pressurized distillation column (T4). The remaining trace amount of top gas is sent to the pre-distillation column (T1) through a vacuum jet pump (P1) to generate low pressure, thereby controlling the negative pressure of the negative pressure distillation column (T2) and the methanol separation column (T6).
[0007] The bottom stream of the pressurized distillation column (T4) is heated by steam and vaporized before flowing into the pressurized distillation column (T4). The remaining stream flows into the lower part of the atmospheric distillation column (T5).
[0008] The vapor at the top of the atmospheric distillation column (T5) is partially condensed and flows into the atmospheric distillation column reflux tank (D3). Part of it flows into the atmospheric distillation column (T5) and the negative pressure distillation column (T2), and part of it flows out of the boundary area as refined methanol product. The remaining vapor phase is sent to the pre-distillation column (T1) via the vacuum jet pump (P1), and wastewater is collected from the bottom of the column and flows out of the boundary area.
[0009] The vapor at the top of the methanol recovery tower (T6) is partially condensed, with some flowing into the methanol recovery tower (T6) and the rest flowing out as refined methanol product. The non-condensable gas is sent to the pre-distillation tower (T1) via the jet vacuum pump (P1) to generate low pressure, and the bottom stream flows out as fuel alcohol product.
[0010] Approximately 2% of the vapor at the top of the pressurized distillation column (T4) is sent to the pre-distillation column (T1) via a vacuum jet pump (P1).
[0011] The second technical solution of the present invention is a process method using the above-mentioned apparatus, comprising the following steps:
[0012] First, the raw material crude methanol flows into the pre-distillation column (T1). The top steam of the column heats the reboiler (R2) of the negative pressure distillation column, and part of it is condensed to separate the light component non-condensable vapor. The bottom stream of the pre-distillation column (T1) flows into the reboiler (R1) of the pre-distillation column and is heated by the top gas of the medium-pressure distillation column (T3). After being heated and vaporized, it flows into the pre-distillation column (T1). The remaining stream flows into the lower part of the negative pressure distillation column (T2) for separation.
[0013] Secondly, the vapor from the top of the negative pressure distillation column (T2) is partially condensed and then sent to the reflux tank (D3) of the atmospheric pressure distillation column via the jet vacuum pump B (P2). Part of it flows into the atmospheric pressure distillation column (T5) and the negative pressure distillation column (T2), while part flows out as refined methanol product. The non-condensable gas is sent to the pre-distillation column (T1) via the jet vacuum pump (P1) to generate low pressure. The bottom stream of the negative pressure distillation column (T2) flows into the reboiler (R2) of the negative pressure distillation column and is heated by the vapor phase from the top of the pre-distillation column (T1). After being heated and vaporized, it flows into the negative pressure distillation column (T2). The remaining stream flows into the lower part of the medium-pressure distillation column (T3) for separation.
[0014] The steam from the top of the medium-pressure distillation column (T3) heats the reboiler (R1) of the pre-distillation column, and is then sent to the reflux tank (D3) of the atmospheric distillation column via the jet vacuum pump B (P2). Part of the steam flows into the atmospheric distillation column (T5) and the negative pressure distillation column (T2), while the rest flows out as refined methanol product. The bottom stream of the medium-pressure distillation column (T3) flows into the reboiler (R3) of the medium-pressure distillation column, where it is heated by the steam from the top of the pressurized distillation column. After being heated and vaporized, the vaporized steam flows into the medium-pressure distillation column (T3).
[0015] The first stream of steam from the top of the pressurized distillation column (T4) heats the reboiler (R3) of the medium-pressure distillation column, and then refluxes. The second stream of steam heats the reboiler (R5) of the atmospheric distillation column, and then refluxes. The remaining steam is sent to the pre-distillation column (T1) via a vacuum jet pump (P1), thereby controlling the negative pressure of the negative pressure distillation column (T2) and the methanol recovery column (T6). The bottom stream of the pressurized distillation column (T4) flows into the reboiler (R4) of the pressurized distillation column, is heated by steam, and then flows back into the pressurized distillation column (T4). The remaining stream flows into the lower part of the atmospheric distillation column (T5) for separation.
[0016] The vapor at the top of the atmospheric distillation column (T5) is partially condensed and flows into the atmospheric distillation column reflux tank (D3). Part of it flows into the atmospheric distillation column (T5) and the negative pressure distillation column (T2), and part of it flows out of the boundary area as refined methanol product. The remaining vapor phase is sent to the pre-distillation column (T1) via the vacuum jet pump (P1). Wastewater is collected from the bottom of the column and flows out of the boundary area.
[0017] The vapor at the top of the methanol recovery tower (T6) is partially condensed, with some flowing back into the methanol recovery tower (T6) and the rest flowing out as refined methanol. The non-condensable gas is pumped by a jet vacuum pump (P1) to the pre-distillation tower (T1) to generate low pressure. The bottom stream flows out as fuel alcohol.
[0018] Preferably, the operating pressure of the pre-distillation column (T1) is 150±5 kPa; the operating pressure of the vacuum distillation column (T2) is 55±5 kPa and the reflux ratio is 1.5-2; the operating pressure of the medium-pressure distillation column (T3) is 320±5 kPa and the reflux ratio is 2-3; and the operating pressure of the pressurized distillation column (T4) is 600±5 kPa and the reflux ratio is 2.5-3.
[0019] Preferably, the atmospheric distillation column (T5) operates at a pressure of 100±5 kPa and a reflux ratio of 4-5.
[0020] Preferably, the methanol recovery tower (T6) operates at a pressure of 55±5 kPa and a reflux ratio of 3-4.
[0021] Preferably, the temperature of the fuel alcohol collected from the bottom of the methanol recovery tower (T6) is 63.6±5℃.
[0022] This invention has the following advantages: In order to reduce energy consumption, this invention proposes for the first time an innovative six-tower mixed-direction four-effect negative pressure heat pump assisted methanol distillation energy-saving device and process. The process couples heat pump assisted distillation technology and multi-effect distillation technology. Compared with the traditional four-tower process, the production capacity can be expanded by 20% to 50%, and the unit refined methanol production consumption is 0.55 to 0.65 steam consumption, realizing significant energy saving in methanol distillation. It is suitable for large-scale expansion of the traditional four-tower process.
[0023] 1. The negative pressure distillation column acts as a heat sink. The top vapor of the pre-distillation column heats the reboiler of the negative pressure distillation column; the top vapor of the medium-pressure distillation column heats the reboiler of the pre-distillation column; one branch of the gas from the top of the pressurized distillation column heats the reboiler of the medium-pressure distillation column, and another branch of the gas from the pressurized distillation column heats the reboiler of the atmospheric pressure distillation column.
[0024] 2. The production capacity of refined methanol is dispersed. Among them, the top of the negative pressure distillation tower, the atmospheric pressure distillation tower and the methanol recovery tower produce refined methanol products with high yield. The tower equipment is small in size, which is convenient for manufacturing, transportation and safety inspection.
[0025] 3. The negative pressure distillation column, the atmospheric pressure distillation column, and the methanol recovery column all operate under atmospheric or negative pressure, which reduces the heat trap temperature and the temperature difference between the top and bottom of the column.
[0026] 4. The process makes full use of waste heat, and the steam consumption per unit of refined methanol production is 0.55 to 0.65, which achieves significant energy saving in methanol distillation and meets the energy saving target. Attached Figure Description
[0027] Figure 1 This is a flowchart illustrating the present invention;
[0028] Figure reference numerals: T1 Pre-distillation column, T2 Negative pressure distillation column, T3 Medium pressure distillation column, T4 Pressurized distillation column, T5 Atmospheric pressure distillation column, T6 Methanol recovery column, R1 Pre-distillation column reboiler, R2 Negative pressure distillation column reboiler, R3 Medium pressure distillation column reboiler, R4 Pressurized distillation column reboiler, R5 Atmospheric pressure distillation column reboiler, R6 Methanol recovery column reboiler II, CX1 Negative pressure distillation column condenser, CX2 Atmospheric pressure distillation column condenser, CX3 Methanol recovery column condenser, D1 Pre-distillation column reflux tank, D2 Pressurized distillation column reflux tank, D3 Atmospheric pressure distillation column reflux tank, P1 Jet vacuum pump A, P2 Jet vacuum pump B. Detailed Implementation
[0029] The following is in conjunction with the appendix Figure 1 The specific embodiments of the present invention will be described in detail below. It should be noted that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the present invention.
[0030] Example 1:
[0031] like Figure 1 As shown, this embodiment provides a six-tower reverse quadruple-effect negative pressure heat pump-assisted methanol distillation energy-saving device and process method. The device includes a pre-distillation tower T1, a negative pressure distillation tower T2, a medium-pressure distillation tower T3, a pressurized distillation tower T4, an atmospheric pressure distillation tower T5, and a methanol recovery tower T6 connected in sequence. This invention employs a top vapor recompression heat pump coupled with multi-effect distillation technology, and its process flow includes the following steps:
[0032] First, the raw material crude methanol flows into the pre-distillation column T1. The top vapor of the column heats the reboiler R2 of the negative pressure distillation column, and part of it is condensed to separate the light component non-condensable vapor. The bottom stream of the pre-distillation column T1 flows into the reboiler R1 of the pre-distillation column and is heated by the top gas of the medium-pressure distillation column T3. After being heated and vaporized, it flows into the pre-distillation column T1. The remaining stream flows into the lower part of the negative pressure distillation column T2 for separation.
[0033] Secondly, the vapor at the top of the negative pressure distillation column T2 is partially condensed and then sent to the reflux tank D3 of the atmospheric pressure distillation column via the P2 jet vacuum pump B. Part of it flows into the atmospheric pressure distillation column T5 and the negative pressure distillation column T2, while part of it flows out as refined methanol product. The non-condensable gas is sent to the pre-distillation column T1 via the jet vacuum pump P1 to generate low pressure. The bottom stream of the negative pressure distillation column T2 flows into the reboiler R2 of the negative pressure distillation column and is heated by the vapor phase at the top of the pre-distillation column T1. After being heated and vaporized, it flows into the negative pressure distillation column T2. The remaining stream flows into the lower part of the medium-pressure distillation column T3 for separation.
[0034] The steam from the top of the medium-pressure distillation column T3 heats the reboiler R1 of the pre-distillation column, and is then sent to the reflux tank D3 of the atmospheric distillation column via the vacuum pump B (P2). Part of the steam flows into the atmospheric distillation column T5 and the negative pressure distillation column T2, while the rest flows out as refined methanol product. The bottom stream of the medium-pressure distillation column T3 flows into the reboiler R3 of the medium-pressure distillation column, is heated by part of the steam from the top of the pressurized distillation column, and after vaporization, flows into the medium-pressure distillation column T3.
[0035] The first stream of steam from the top of the pressurized distillation column T4 heats the reboiler R3 of the medium-pressure distillation column, and then refluxes. The second stream of steam heats the reboiler R5 of the atmospheric distillation column, and then refluxes. The remaining 2% of steam is sent to the pre-distillation column T1 via the vacuum jet pump P1, thereby controlling the negative pressure of the negative pressure distillation column T2 and the methanol recovery column T6. The bottom stream of the pressurized distillation column T4 flows into the reboiler R4 of the pressurized distillation column, is heated by steam, and then flows back into the pressurized distillation column T4 after vaporization. The remaining stream flows into the lower part of the atmospheric distillation column T5 for separation.
[0036] Part of the vapor at the top of atmospheric distillation column T5 is condensed and flows into the atmospheric distillation column reflux tank D3. Part of it flows into atmospheric distillation column T5 and negative pressure distillation column T2, and part of it flows out of the boundary area as refined methanol product. The remaining vapor phase is sent to pre-distillation column T1 via vacuum jet pump P1. Wastewater is collected from the bottom of the column and flows out of the boundary area.
[0037] The vapor at the top of methanol recovery tower T6 is partially condensed, with part flowing back into tower T6 and part exiting as refined methanol. The non-condensable gas is pumped by jet vacuum pump P1 to the pre-distillation tower T1 to generate low pressure. The bottom stream exits as fuel alcohol.
[0038] The operating pressure of the pre-distillation column T1 is 150±5 kPa; the operating pressure of the vacuum distillation column T2 is 55±5 kPa, and the reflux ratio is 1.5-2; the operating pressure of the medium-pressure distillation column T3 is 320±5 kPa, and the reflux ratio is 2-3; the operating pressure of the pressurized distillation column T4 is 600±5 kPa, and the reflux ratio is 2.5-3; the operating pressure of the atmospheric distillation column T5 is 100±5 kPa, and the reflux ratio is 4-5; and the operating pressure of the methanol recovery column T6 is 55±5 kPa, and the reflux ratio is 3-4.
[0039] The temperature of the fuel alcohol collected from the bottom of the T6 alcohol recovery tower is 63.6±5℃.
[0040] The crude methanol feedstock has a water content of about 4%.
[0041] Compared with existing industrial processes, the unit steam consumption of this solution for producing refined methanol is only 0.55 to 0.65, with a yield of 99.99% and a purity of up to 99.99%.
[0042] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
[0043] 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 the present invention will not be described separately.
[0044] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, and such inventions should also be regarded as the contents disclosed in the present invention.
Claims
1. A six-tower mixed-direction four-effect negative pressure heat pump assisted methanol distillation energy-saving device, characterized in that, The system comprises a pre-distillation column (T1), a negative pressure distillation column (T2), a medium pressure distillation column (T3), a pressurized distillation column (T4), an atmospheric pressure distillation column (T5), and a methanol recovery column (T6) connected in sequence. The lower part of the pre-distillation column (T1) is connected to a pre-distillation column reboiler (R1). The lower part of the negative pressure distillation column (T2) is connected to a negative pressure distillation column reboiler (R2). The lower part of the medium pressure distillation column (T3) is connected to a medium pressure distillation column reboiler (R3). The lower part of the pressurized distillation column (T4) is connected to a pressurized distillation column reboiler (R4). The lower part of the atmospheric pressure distillation column (T5) is connected to an atmospheric pressure distillation column reboiler (R5). The lower part of the methanol recovery column (T6) is connected to a methanol recovery column reboiler (R6). The overhead gas from the pre-distillation column (T1) heats the reboiler (R2) of the negative pressure distillation column; the overhead steam from the medium-pressure distillation column (T3) heats the reboiler (R1) of the pre-distillation column. One branch of gas from the top of the pressurized distillation column (T4) heats the reboiler (R3) of the medium-pressure distillation column, and the heated stream flows back to the top of the pressurized distillation column (T4). The other branch of gas heats the reboiler (R5) of the atmospheric distillation column, and the heated stream flows back to the top of the pressurized distillation column (T4). The remaining trace amount of top gas is sent to the pre-distillation column (T1) through a vacuum jet pump (P1) to generate low pressure, thereby controlling the negative pressure of the negative pressure distillation column (T2) and the methanol separation column (T6).
2. The apparatus according to claim 2, characterized in that, The bottom stream of the pressurized distillation column (T4) is heated by steam and vaporized before flowing into the pressurized distillation column (T4). The remaining stream flows into the lower part of the atmospheric distillation column (T5).
3. The apparatus according to claim 3, characterized in that, The vapor at the top of the atmospheric distillation column (T5) is partially condensed and flows into the atmospheric distillation column reflux tank (D3). Part of it flows into the atmospheric distillation column (T5) and the negative pressure distillation column (T2), and part of it flows out of the boundary area as refined methanol product. The remaining vapor phase is sent to the pre-distillation column (T1) via the vacuum jet pump (P1), and wastewater is collected from the bottom of the column and flows out of the boundary area.
4. The apparatus according to claim 1, characterized in that, The vapor at the top of the methanol recovery tower (T6) is partially condensed, with some flowing into the methanol recovery tower (T6) and the rest flowing out as refined methanol product. The non-condensable gas is sent to the pre-distillation tower (T1) via the jet vacuum pump (P1) to generate low pressure, and the bottom stream flows out as fuel alcohol product.
5. The apparatus according to claim 5, characterized in that, Approximately 2% of the vapor at the top of the pressurized distillation column (T4) is sent to the pre-distillation column (T1) via a vacuum jet pump (P1).
6. The process method using the apparatus according to claims 1 to 5, characterized in that, Includes the following steps: First, the raw material crude methanol flows into the pre-distillation column (T1). The top steam of the column heats the reboiler (R2) of the negative pressure distillation column, and part of it is condensed to separate the light component non-condensable vapor. The bottom stream of the pre-distillation column (T1) flows into the reboiler (R1) of the pre-distillation column and is heated by the top gas of the medium-pressure distillation column (T3). After being heated and vaporized, it flows into the pre-distillation column (T1). The remaining stream flows into the lower part of the negative pressure distillation column (T2) for separation. Secondly, the vapor from the top of the negative pressure distillation column (T2) is partially condensed and then sent to the reflux tank (D3) of the atmospheric pressure distillation column via the jet vacuum pump B (P2). Part of it flows into the atmospheric pressure distillation column (T5) and the negative pressure distillation column (T2), while part flows out as refined methanol product. The non-condensable gas is sent to the pre-distillation column (T1) via the jet vacuum pump (P1) to generate low pressure. The bottom stream of the negative pressure distillation column (T2) flows into the reboiler (R2) of the negative pressure distillation column and is heated by the vapor phase from the top of the pre-distillation column (T1). After being heated and vaporized, it flows into the negative pressure distillation column (T2). The remaining stream flows into the lower part of the medium-pressure distillation column (T3) for separation. The steam from the top of the medium-pressure distillation column (T3) heats the reboiler (R1) of the pre-distillation column, and is then sent to the reflux tank (D3) of the atmospheric distillation column via the jet vacuum pump B (P2). Part of the steam flows into the atmospheric distillation column (T5) and the negative pressure distillation column (T2), while the rest flows out as refined methanol product. The bottom stream of the medium-pressure distillation column (T3) flows into the reboiler (R3) of the medium-pressure distillation column, where it is heated by the steam from the top of the pressurized distillation column. After being heated and vaporized, the vaporized steam flows into the medium-pressure distillation column (T3). The first stream of steam from the top of the pressurized distillation column (T4) heats the reboiler (R3) of the medium-pressure distillation column, and then refluxes. The second stream of steam heats the reboiler (R5) of the atmospheric distillation column, and then refluxes. The remaining steam is sent to the pre-distillation column (T1) via a vacuum jet pump (P1), thereby controlling the negative pressure of the negative pressure distillation column (T2) and the methanol recovery column (T6). The bottom stream of the pressurized distillation column (T4) flows into the reboiler (R4) of the pressurized distillation column, is heated by steam, and then flows back into the pressurized distillation column (T4). The remaining stream flows into the lower part of the atmospheric distillation column (T5) for separation. The vapor at the top of the atmospheric distillation column (T5) is partially condensed and flows into the atmospheric distillation column reflux tank (D3). Part of it flows into the atmospheric distillation column (T5) and the negative pressure distillation column (T2), and part of it flows out of the boundary area as refined methanol product. The remaining vapor phase is sent to the pre-distillation column (T1) via the vacuum jet pump (P1). Wastewater is collected from the bottom of the column and flows out of the boundary area. The vapor at the top of the methanol recovery tower (T6) is partially condensed, with some flowing into the methanol recovery tower (T6) and the rest flowing out of the boundary as refined methanol product. The non-condensable gas is sent to the pre-distillation tower (T1) via the jet vacuum pump (P1) to generate low pressure, and the bottom stream flows out of the boundary as fuel alcohol product.
7. The method according to claim 6, characterized in that, The operating pressure of the pre-distillation column (T1) is 150±5 kPa; the operating pressure of the vacuum distillation column (T2) is 55±5 kPa, and the reflux ratio is 1.5-2; the operating pressure of the medium-pressure distillation column (T3) is 320±5 kPa, and the reflux ratio is 2-3; the operating pressure of the pressurized distillation column (T4) is 600±5 kPa, and the reflux ratio is 2.5-3.
8. The method according to claim 6, characterized in that, The atmospheric distillation column (T5) operates at a pressure of 100±5 kPa and has a reflux ratio of 4-5.
9. The method according to claim 6, characterized in that, The methanol recovery tower (T6) operates at a pressure of 55±5 kPa and a reflux ratio of 3-4.
10. The method according to claim 6, characterized in that, The temperature of the fuel alcohol collected from the bottom of the methanol recovery tower (T6) is 63.6±5℃.