Low-pressure cross-flow triple-effect dividing wall column rectification process and device for refining crude methanol

Abstract

The invention relates to a low-pressure cross-flow triple-effect dividing wall column rectification process and device for refining crude methanol, the process comprises a normal-pressure dividing wall column, a vacuum column and a pressurizing column, the tower top pressure of the normal-pressure dividing wall column is 130-150KPa (A), and the tower top temperature is 70-80 DEG C; the tower kettle temperature of the normal-pressure dividing wall tower is 7-8 DEG C higher than the tower top temperature; an inlet of the pressurizing tower is connected with an outlet of a tower kettle of the vacuum tower, and live steam of 0.6 MPa is used as a heat source; the pressure of the top of the pressurizing tower is 320-340KPa (A), the temperature of the top of the pressurizing tower is 96-100 DEG C, and the temperature of the bottom of the pressurizing tower is 136-140 DEG C; the pressure at the top of the vacuum tower is 50-60KPa (A), the temperature at the top of the vacuum tower is 48-52 DEG C, and the temperature difference between the top and the kettle of the vacuum tower is 7-8 DEG C; and the atmospheric tower reboiler, the vacuum tower top reflux and the second vacuum tower reboiler are all used for partially extracting refined methanol. The triple-effect rectification requirement is met on the premise that low-pressure steam is used, efficient triple-effect rectification of crude methanol in actual engineering is achieved, and energy consumption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of crude methanol refining in coal chemical industry or biomass green methanol process, and specifically to a low-pressure cross-flow three-effect dividing wall tower distillation process and device for crude methanol refining, which uses low-pressure steam as a heat source and is combined with a dividing wall tower and a cross-flow multiple effect for crude methanol refining. Background Art

[0002] Methanol is a basic chemical raw material with a wide range of applications. The current sources of methanol are mainly coal-to-methanol and biomass methanol (green methanol). In order to meet the strategic development needs of the country in energy conservation and consumption reduction, multi-effect distillation and bulkhead thermal coupling are currently recognized as effective energy-saving methods that can be used in methanol refining processes. For example: CN 116947605 A discloses a five-tower four-effect crude methanol refining process and device, which adopts a five-tower three-effect separation technology and can be mainly divided into a pre-tower, a pressure reducing tower, a pressure tower, a normal pressure tower and a recovery tower according to the material flow, wherein the operating pressure of the pressure tower is 0.63MPa (A); the pressure tower heat source steam pressure is 1.0MPa.

[0003] CN 113527058 A discloses a side line and a bulkhead pre-distillation tower heat sink multi-effect methanol distillation method, wherein Example 3 adopts a normal pressure tower, a medium pressure tower and a high pressure tower design. It passes through the pre-tower and the normal pressure tower (combined into a bulkhead tower), the medium pressure tower and the high pressure tower in sequence, wherein the top pressure of the high pressure tower is 700KPa (A), and the steam pressure of the pressurized tower should be conservatively greater than 1.0MPa.

[0004] CN 113289363 A discloses a crude methanol refining and purification system, which adopts a four-tower three-effect separation process. According to the material flow, the system is a pre-tower, a medium-pressure tower, a low-pressure tower, and a normal-pressure tower. The top pressure of the medium-pressure tower is 1.1-1.4 MPa, and 1.1-1.3 MPaG steam needs to be provided to the medium-pressure tower.

[0005] CN 109646980 A discloses a non-fusel oil final effect bulkhead tower coupled with a methanol multi-effect distillation energy-saving device and method, which adopts an external wall-mounted bulkhead tower, which is composed of a main tower and an externally suspended auxiliary tower. The device sequence is a light-removal tower, a high-pressure tower, a medium-pressure tower and an externally mounted bulkhead tower. Although the heating steam pressure adopts 600KPa steam, the gas phase temperature at the top of the medium-pressure tower in the embodiment is 104°C. Considering the influence of the pressure drop of the medium-pressure tower and the increase of the water content in the tower bottom, the tower bottom temperature of the medium-pressure tower is at least 4°C higher than the tower top temperature, that is, the tower bottom temperature is at least not lower than 108°C. The gas phase temperature at the top of the high-pressure tower is 111.8°C. Even if the heat dissipation effect is not considered, the heat transfer temperature difference of the medium-pressure tower reboiler is only 111.8-108=3.8°C. Such a small temperature difference may cause the heat transfer area of ​​the medium-pressure tower reboiler to expand several times in actual engineering, and even cause the problem of inability to operate.

[0006] It can be seen from the above that for the general three-effect methanol refining process, there are certain requirements for the pressure and temperature of the heating steam (heat source). Generally, only when the system increases the steam by more than 1.0MPa can the smooth progress of the three-effect distillation process be guaranteed.

[0007] However, for some coal chemical enterprises, there is a large amount of surplus low-pressure steam (0.6MPa), and it is difficult to meet the design requirements of the three-effect distillation process under this pressure. Therefore, under low-pressure steam conditions, the existing process generally adopts single-effect or double-effect evaporation, which consumes a lot of energy.

[0008] Therefore, it is very important to develop and propose a crude methanol three-effect distillation process with low-pressure steam suitable for actual engineering operations for energy conservation and emission reduction in most existing enterprises. Summary of the invention

[0009] The purpose of the present invention is to provide a low-pressure cross-flow three-effect dividing wall tower distillation process and device for crude methanol refining, so as to meet the requirements of three-effect distillation under the premise of using low-pressure steam, realize efficient three-effect distillation of crude methanol in actual engineering, and save energy consumption.

[0010] To achieve the purpose of the present invention, the technical solution provided by the present invention is: In the first aspect, the present invention provides a low-pressure cross-flow three-effect bulkhead tower distillation process for crude methanol refining, the process comprising an atmospheric pressure bulkhead tower 1, a vacuum tower 2 and a pressurized tower 3, the vacuum tower kettle is equipped with a first vacuum tower reboiler and a second vacuum tower reboiler, and the atmospheric pressure bulkhead tower kettle is equipped with an atmospheric pressure tower reboiler; The crude methanol is firstly preheated by the exhaust steam primary cooler 4 at the top of the vacuum tower 2, and then enters the raw material preheater 5 for secondary preheating. After preheating, the crude methanol temperature rises to 70-80°C; then it enters one side of the atmospheric pressure bulkhead tower from the material inlet of the atmospheric pressure bulkhead tower, and the top gas phase of this side enters the reboiler of the first vacuum tower to provide heat and be condensed, and the uncondensed light phase gas enters the light hydrocarbon condenser 9 to continue condensing, and the tail gas enters the spray absorption tower 10; the condensate from the spray absorption tower 10 is fully refluxed into the atmospheric pressure bulkhead tower on the corresponding side, and the top pressure of this side is 130-150KPa (A), and the top temperature is 70-80°C; The top pressure of the other side of the atmospheric pressure dividing wall tower is 130-150 kPa (A), and the top gas phase temperature is 70-80 ° C. The top gas phase of this side enters the reboiler 8 of the second vacuum tower, and a part of the condensed liquid after condensation is refluxed into the atmospheric pressure dividing wall tower as the reflux liquid of this side; the bottom temperature of the atmospheric pressure dividing wall tower 1 is 7-8 ° C higher than the top temperature; The inlet of the pressure tower is connected to the outlet of the vacuum tower kettle, and 0.6MPa raw steam is used as a heat source; the light phase outlet at the top of the tower is connected to the steam inlet of the atmospheric tower reboiler, which serves as the heat source of the atmospheric tower reboiler. Part of the condensate in the atmospheric tower reboiler flows back to the atmospheric tower, and the rest flows out to the outside as a refined methanol product; The outlet of the pressurized tower is pure water, which is discharged after heat recovery, and fusel alcohol is discharged from the side line; the top pressure of the pressurized tower is 320-340KPa (A), the top temperature is 96-100°C, and the bottom temperature is 136-140°C; The pressure at the top of the vacuum tower is 50-60 KPa (A), the temperature at the top is 48-52°C, and the temperature difference between the top and bottom of the vacuum tower is 7-8°C; The atmospheric tower reboiler, the vacuum tower top reflux, and the second vacuum tower reboiler all partially produce refined methanol.

[0011] Furthermore, the purity of methanol in the refined methanol is not less than 99.98wt%.

[0012] Furthermore, the steam temperature of the raw steam is 155-165°C.

[0013] Furthermore, the crude methanol content is 80-93wt%.

[0014] In a second aspect, the present invention provides a low-pressure cross-flow triple-effect dividing wall tower distillation device for crude methanol refining, the device comprising a normal pressure dividing wall tower 1, a vacuum tower 2 and a pressure tower 3; The atmospheric pressure dividing wall tower is composed of a pre-tower and an atmospheric pressure tower, the upper parts of the pre-tower and the atmospheric pressure tower are separated by a partition, the pre-tower and the atmospheric pressure tower are respectively provided with independent gas phase outlets, and the lower parts of the two towers share a space and a reboiler; The raw material inlet of the pre-tower of the atmospheric pressure dividing wall tower is connected to the upstream crude methanol; The gas phase outlet of the tower top of the pre-tower is connected to the first vacuum tower reboiler 7, and the first vacuum tower reboiler 7 is respectively connected to the light hydrocarbon condenser 9, the tower kettle of the vacuum tower, and the raw steam condensate preheater 12; the outlet of the light hydrocarbon condenser 9 is connected to the bottom inlet of the spray absorption tower, and the bottom outlet of the spray absorption tower is connected to the top reflux port of the pre-tower; the top of the spray absorption tower produces light hydrocarbons, and desalted water enters from the top of the spray absorption tower; The top gas phase of the atmospheric tower of the atmospheric bulkhead tower is connected to the second vacuum tower reboiler 8, and the second vacuum tower reboiler is installed in the vacuum tower kettle. Part of the condensate from the second vacuum tower reboiler flows back into the atmospheric tower, and part of it flows out to the outside as a refined methanol product; The tower bottom liquid phase outlet of the atmospheric pressure dividing wall tower is connected to the material inlet of the vacuum tower 2; the heat source of the atmospheric pressure tower reboiler 6 of the atmospheric pressure dividing wall tower is provided by the tower top gas phase of the pressure tower; The top of the vacuum tower is connected to an exhaust steam primary cooler and a vacuum tower condenser; The outlet of the raw steam condensate preheater 12 is connected to the material inlet of the pressurized tower, and the water vapor inlet of the raw steam condensate preheater 12 is connected to the 0.6 MPa industrial water vapor supply pipeline through the pressurized tower reboiler; The tower kettle of the pressure tower is equipped with a pressure tower reboiler, the top reflux port of the pressure tower is connected to the condensate outlet of the atmospheric tower reboiler, and the top gas phase outlet of the pressure tower is connected to the inlet of the atmospheric tower reboiler; the outlet of the pressure tower reboiler is also connected to the raw material preheater 5; The upstream crude methanol is connected to the raw material inlet of the pre-tower after passing through the exhaust steam primary cooler and the raw material preheater, and waste water is produced in the raw material preheater; The reboiler of the atmospheric tower and the top reflux of the vacuum tower both produce refined methanol.

[0015] Preferably, the atmospheric pressure dividing wall tower and the pressure tower use full countercurrent TST tower plates.

[0016] Preferably, the vacuum tower is a packed tower, and the reboiler of the first vacuum tower is a falling film reboiler.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The process of the present invention can realize efficient three-effect distillation of crude methanol in actual engineering under the conditions of raw steam pressure of 0.6MPa (160℃) and cooling water of room temperature water of 25℃ (negative pressure tower top temperature of 50℃).

[0018] 2. The atmospheric pressure section of the process of the present invention adopts a bulkhead tower structure, a partition is arranged inside the bulkhead tower, the pre-tower and the atmospheric pressure tower are refluxed independently, and share a reboiler, which is more conducive to energy saving and heat load matching of the whole system through thermal coupling; the process material flow adopts a cross-flow design of atmospheric pressure-decompression-pressurization, and the temperature difference of the tower top and the tower bottom of the three effects can be reduced to about 7°C, 8°C, and 40°C respectively (that is, the temperature difference of the tower top and the tower bottom of the atmospheric pressure bulkhead tower is about 7°C, and the temperature difference of the tower top and the tower bottom of the vacuum tower is about 8°C, the temperature difference of the two towers is almost the same, and the temperature difference of the tower top and the tower bottom of the pressure tower is about 40°C, which can make the top of the last pressure tower produce refined methanol), then the total temperature difference for heat transfer can reach 58°C, and the average heat transfer temperature difference of each effect is 17-18°C, which can significantly reduce the equipment cost investment of each effect reboiler.

[0019] 3. The vacuum tower adopts double reboilers, which can better match the pre-tower and pressure tower of the adjacent tower to ensure the stable operation of the adjacent tower.

[0020] 4. The pressure at the top of the pressure tower in the process of the present invention is 320-340 KPa (A), which is much lower than the pressure of 600 KPa (A) in other processes. Not only is the operation safer and the operating cost lower, but the investment in the pressure tower equipment is also reduced.

[0021] 5. In the methanol refining process of the present invention, the steam consumption per ton of refined methanol can be reduced to less than 0.6 tons, and the purity of the methanol product can exceed 99.98%, thereby obtaining refined methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a schematic flow diagram of a low-pressure cross-flow triple-effect dividing wall tower distillation process for crude methanol refining.

[0023] Among them, 1 atmospheric pressure dividing wall tower, 2 vacuum tower, 3 pressurized tower, 4 exhaust steam primary cooler, 5 raw material preheater, 6 atmospheric pressure tower reboiler, 7 first vacuum tower reboiler, 8 second vacuum tower reboiler, 9 light hydrocarbon condenser, 10 spray absorption tower, 11 vacuum tower condenser, 12 raw steam condensate preheater, 13 pressurized tower reboiler. DETAILED DESCRIPTION

[0024] The present invention is further explained below in conjunction with the embodiments and drawings, but this is not intended to limit the scope of protection of the present application.

[0025] The present invention provides a low-pressure cross-flow triple-effect dividing wall tower distillation device for crude methanol refining, comprising a normal pressure dividing wall tower 1, a vacuum tower 2 and a pressure tower 3; The atmospheric pressure dividing wall tower (a partition is arranged at the upper part of the tower) is composed of a pre-tower (sub-tower) (total reflux) and an atmospheric pressure tower (mother tower), and is provided with independent gas phase outlets respectively, while the lower part shares a space and a reboiler.

[0026] The raw material inlet of the pre-tower of the atmospheric pressure dividing wall tower is connected to the upstream crude methanol, and the upstream crude methanol enters the raw material inlet of the pre-tower after being treated by the exhaust steam primary cooler 4 and the raw material preheater; the top gas phase outlet of the pre-tower is connected to the first vacuum tower reboiler 7, and the top gas phase is condensed in the first vacuum tower reboiler, and the light phase component is discharged as non-condensable gas, and the condensate is fully refluxed to the pre-tower; The top gas phase of the atmospheric tower of the atmospheric bulkhead tower is connected to the reboiler 8 of the second vacuum tower, part of the condensate flows back into the atmospheric tower, and the rest flows out to the outside as refined methanol product; refined methanol is extracted from the condensate after heat exchange in the reboiler of the second vacuum tower as the second methanol stream.

[0027] The bottom liquid phase outlet of the atmospheric pressure dividing wall tower is connected to the material inlet of the vacuum tower 2; the pressure tower inlet is connected to the bottom outlet of the vacuum tower, and 0.6MPa raw steam is used as the heat source, and the steam temperature is 160°C, which is effect I. The top light phase outlet of the pressure tower is connected to the steam inlet of the atmospheric pressure tower reboiler as the heat source of the atmospheric pressure tower reboiler, which is effect II. The condensate after heat exchange in the atmospheric pressure tower reboiler produces refined methanol, which is the first methanol stream of refined methanol.

[0028] The vacuum tower adopts double reboilers, and the heat sources of the reboilers are respectively the secondary steam from the top of the pre-tower of the atmospheric pressure tower and the top of the atmospheric pressure tower, which is the III effect. After the light phase at the top of the vacuum tower enters the vacuum tower condenser for treatment, part of the condensate flows out as the refined methanol product, which is the third methanol stream of refined methanol. The mother liquor in the bottom of the vacuum tower is heated by heat exchange and then enters the pressurization tower.

[0029] The outlet of the bottom of the pressurized tower is pure water, which is discharged after heat recovery, and fusel alcohol is discharged from the side line.

[0030] The top pressure of the atmospheric pressure tower is 130-150KPa (A), and the top temperature is 70℃-80℃; the pressure or temperature on both sides of the tower top of the tower (separated by a partition at the top of the tower) is slightly different due to the influence of the top condenser, but try to keep the difference small, which is conducive to the operation of the tower. Adjust the cooling capacity of the reboiler to adjust the gas phase distribution to ensure that it is an atmospheric pressure tower.

[0031] The pressure at the top of the vacuum tower is 50-60KPa (A), corresponding to a temperature of 48-52°C; the temperature at the bottom of the tower is 56-60°C; The pressure at the top of the pressure tower is 320-340KPa (A), corresponding to a temperature of 96-100°C; the temperature at the bottom of the tower is 136-145°C. A represents absolute pressure.

[0032] As a preferred solution, the atmospheric pressure dividing wall tower can use industrial full countercurrent TST tower plates with larger gas-liquid flux, higher mass transfer efficiency and lower plate pressure drop.

[0033] As a preferred solution, the vacuum tower condenser 11 in the present invention is connected to a vacuum pump.

[0034] As a preferred solution, the vacuum tower is a packed tower, and its reboiler is a falling film reboiler, which can be equipped with a circulating pump.

[0035] As a preferred solution, the pressurized tower uses industrial full countercurrent TST tower plates with larger gas-liquid flux, higher mass transfer efficiency and lower plate pressure drop.

[0036] Embodiment 1: The present embodiment is a low-pressure cross-flow three-effect bulkhead distillation process for crude methanol refining. The crude methanol is first preheated in the exhaust steam primary cooler 4 at the top of the vacuum tower 2, and then enters the raw material preheater 5 for secondary preheating. After preheating, the temperature of the crude methanol rises to about 75°C, and enters one side of the atmospheric pressure bulkhead tower (pre-tower side) from the material inlet of the atmospheric pressure bulkhead tower. The top gas phase of the atmospheric pressure bulkhead tower enters the reboiler 7 of the first vacuum tower to provide heat and be condensed, and the uncondensed light phase gas enters the light hydrocarbon condenser 9 for further condensation, and the tail gas enters the spray absorption tower 10, and enters the subsequent combustion system after further recovering methanol; the condensate coming out of the spray absorption tower 10 is fully refluxed into the atmospheric pressure bulkhead tower on the corresponding side, and the top pressure of the tower on this side is 130KPa (A) and the temperature is about 78°C. The top pressure of the other side (distillation side) of the atmospheric pressure dividing wall tower is 130 kPa, and the top gas temperature is 71 ° C. The top gas on the other side of the atmospheric pressure dividing wall tower enters the second vacuum tower reboiler 8, and the tail gas is heated and condensed. Part of the condensed condensate is refluxed into the atmospheric pressure dividing wall tower 1 as the reflux liquid on the distillation side, and the other part is taken out as the vacuum tower refined methanol; the bottom temperature of the atmospheric pressure dividing wall tower 1 is about 80 ° C; the heating steam of the atmospheric pressure tower reboiler 6 comes from the top gas phase of the pressure tower 3, and the gas phase temperature is about 100 ° C, that is, the heat transfer temperature difference of the atmospheric pressure dividing wall tower reboiler is maintained at about 20 ° C.

[0037] Preferably, in order to ensure uniform gas distribution in the atmospheric pressure dividing wall tower, the pre-tower internals of the dividing wall tower adopt TST flow-through tower trays, and are equipped with a gas distribution device matching the TST.

[0038] The bottom liquid of the atmospheric pressure bulkhead tower 1 enters the middle of the vacuum tower 2 by pressure difference; the top pressure of the vacuum tower 2 is 60KPa (A) and the temperature is 52°C. The top gas phase first enters the exhaust steam pre-cooler 4 to preheat the raw materials, and then enters the vacuum tower condenser 11. Part of the condensed liquid is used as the reflux of the vacuum tower 2, and the other part is produced as the pressurized tower refined methanol; the bottom temperature of the vacuum tower 2 is about 60°C, the heat transfer temperature difference of the first vacuum tower reboiler is about 18°C, and the heat transfer temperature difference of the second vacuum tower reboiler 8 is about 11°C.

[0039] Preferably, the internals of the vacuum tower are fillers; the reboiler of the first vacuum tower is a falling film reboiler; The bottom liquid of the vacuum tower 2 enters the raw steam condensate preheater 12 through a pump, and enters the pressurizing tower 3 after preheating; the top pressure of the pressurizing tower 3 is 340KPa (A) and the temperature is 100°C; the top gas phase of the pressurizing tower 3 enters the atmospheric tower reboiler 6 of the atmospheric pressure dividing wall tower 1, and after condensation, part of the condensate is used as the reflux liquid of the pressurizing tower 3, and the other part is produced as the atmospheric tower refined methanol; the bottom liquid temperature of the pressurizing tower 3 is about 141°C, and the discharge from the bottom of the pressurizing tower enters the raw material preheater 5 for cooling and is discharged from the system as waste water; the pressurizing tower reboiler 13 uses 600KPa (A) raw steam as the heat source, and the steam temperature is 159°C, that is, the heat transfer temperature difference of the pressurizing tower reboiler 13 is maintained at 18°C; the side line of the pressurizing tower 3 produces fusel alcohol and is discharged from the system.

[0040] In this embodiment, the crude methanol content is 91.7%, the water content is 6.7%, and the operating parameters of each tower are shown in Table 1:

[0041] The innovative connection mode of the tower equipment in the process of the present invention uses 600KPa (A) raw steam as the heat source, realizes the effective matching of the heat transfer temperature difference in each reboiler, can ensure energy saving and consumption reduction while realizing efficient operation in actual engineering. Each effect in the three-effect distillation of the present invention can operate normally, saving the floor space of the reboiler.

[0042] The present invention uses low-pressure raw steam, and the saturated steam temperature is constant, which can be almost evenly distributed to the three effects, and the refined methanol content is controlled at more than 99.98%, thereby saving steam consumption.

[0043] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A low-pressure cross-flow triple-effect dividing wall tower distillation process for crude methanol refining, characterized in that: The process comprises an atmospheric pressure bulkhead tower, a vacuum tower and a pressure tower, the vacuum tower kettle is equipped with a first vacuum tower reboiler and a second vacuum tower reboiler, and the atmospheric pressure bulkhead tower kettle is equipped with an atmospheric pressure tower reboiler; The crude methanol is first preheated in the primary exhaust steam precooler at the top of the vacuum tower, and then enters the raw material preheater for secondary preheating. After preheating, the crude methanol temperature rises to 70-80°C; then it enters the side of the atmospheric pressure bulkhead tower from the material inlet of the atmospheric pressure bulkhead tower, and the top gas phase of this side enters the reboiler of the first vacuum tower to provide heat and be condensed, and the uncondensed light phase gas enters the light hydrocarbon condenser for further condensation, and the tail gas enters the spray absorption tower; the condensate from the spray absorption tower is fully refluxed into the atmospheric pressure bulkhead tower on the corresponding side, and the top pressure of this side is 130-150KPa (A), and the top temperature is 70-80°C; The top pressure of the other side of the atmospheric pressure bulkhead tower is 130-150 kPa (A), and the top gas phase temperature is 70-80 ° C. The top gas phase of this side enters the reboiler of the second vacuum tower, and part of the condensed condensate is refluxed into the atmospheric pressure bulkhead tower as the reflux liquid of this side; the kettle temperature of the atmospheric pressure bulkhead tower is 7-8 ° C higher than the top temperature; The inlet of the pressure tower is connected to the outlet of the vacuum tower kettle, and 0.6MPa raw steam is used as a heat source; the light phase outlet at the top of the tower is connected to the steam inlet of the atmospheric tower reboiler, which serves as the heat source of the atmospheric tower reboiler. Part of the condensate in the atmospheric tower reboiler flows back to the atmospheric tower, and the rest flows out to the outside as a refined methanol product; The outlet of the pressurized tower is pure water, which is discharged after heat recovery, and fusel alcohol is discharged from the side line; the top pressure of the pressurized tower is 320-340KPa (A), the top temperature is 96-100°C, and the bottom temperature is 136-140°C; The pressure at the top of the vacuum tower is 50-60 KPa (A), the temperature at the top is 48-52°C, and the temperature difference between the top and bottom of the vacuum tower is 7-8°C; The atmospheric tower reboiler, the vacuum tower top reflux, and the second vacuum tower reboiler all partially produce refined methanol.

2. The process according to claim 1, characterized in that The purity of methanol in the refined methanol is not less than 99.98wt%.

3. The process according to claim 1, characterized in that The steam temperature of the raw steam is 155-165°C.

4. The process according to claim 1, characterized in that The crude methanol content is 80-93wt%.

5. A low-pressure cross-flow triple-effect dividing wall tower distillation device for crude methanol refining, characterized in that: The device comprises a normal pressure bulkhead tower, a vacuum tower and a pressure tower; The atmospheric pressure dividing wall tower is composed of a pre-tower and an atmospheric pressure tower, the upper parts of the pre-tower and the atmospheric pressure tower are separated by a partition, the pre-tower and the atmospheric pressure tower are respectively provided with independent gas phase outlets, and the lower parts of the two towers share a space and a reboiler; The raw material inlet of the pre-tower of the atmospheric pressure dividing wall tower is connected to the upstream crude methanol; The gas phase outlet at the top of the pre-tower is connected to the reboiler of the first vacuum tower, and the reboiler of the first vacuum tower is respectively connected to the light hydrocarbon condenser, the kettle of the vacuum tower, and the raw steam condensate preheater; the outlet of the light hydrocarbon condenser is connected to the bottom inlet of the spray absorption tower, and the bottom outlet of the spray absorption tower is connected to the top reflux port of the pre-tower; the top of the spray absorption tower produces light hydrocarbons, and desalted water enters from the top of the spray absorption tower; The top gas phase of the atmospheric tower of the atmospheric bulkhead tower is connected to the reboiler of the second vacuum tower, and the reboiler of the second vacuum tower is installed in the kettle of the vacuum tower. Part of the condensate from the reboiler of the second vacuum tower flows back into the atmospheric tower, and part of it flows out to the outside as a refined methanol product; The tower bottom liquid phase outlet of the atmospheric pressure dividing wall tower is connected to the material inlet of the vacuum tower; the heat source of the atmospheric pressure tower reboiler of the atmospheric pressure dividing wall tower is provided by the tower top gas phase of the pressure tower; The top of the vacuum tower is connected to an exhaust steam primary cooler and a vacuum tower condenser; The outlet of the raw steam condensate preheater is connected to the material inlet of the pressurized tower, and the steam inlet of the raw steam condensate preheater is connected to the 0.6MPa industrial steam supply pipeline through the pressurized tower reboiler; The tower kettle of the pressure tower is equipped with a pressure tower reboiler, the top reflux port of the pressure tower is connected to the condensate outlet of the atmospheric tower reboiler, and the top gas phase outlet of the pressure tower is connected to the inlet of the atmospheric tower reboiler; the outlet of the pressure tower reboiler is also connected to the raw material preheater; The upstream crude methanol is connected to the raw material inlet of the pre-tower after passing through the exhaust steam primary cooler and the raw material preheater, and waste water is produced in the raw material preheater; The reboiler of the atmospheric tower and the top reflux of the vacuum tower both produce refined methanol.

6. The device according to claim 5, characterized in that The atmospheric pressure dividing wall tower and the pressure tower adopt full countercurrent TST tower plates, the vacuum tower adopts a packed tower, and the reboiler of the first vacuum tower adopts a falling film reboiler.

Images