Methanol dehydration quality-improving consumption-reducing recovery method and device for esterification section of process for preparing ethylene glycol from coal-based synthesis gas

Abstract

The invention belongs to the field of coal chemical industry, and particularly relates to a methanol dehydration quality-improving consumption-reducing recovery method and a methanol dehydration quality-improving consumption-reducing recovery device for an esterification section of a process for preparing ethylene glycol from coal-based synthesis gas, raw materials are introduced into a normal / vacuum rectification tower for preliminary separation, light components are extracted from the tower top, refined methanol is extracted from a side line, and normal / vacuum rectification tower bottom liquid is obtained from a tower bottom; introducing the normal / vacuum rectifying tower kettle liquid into a low-pressure rectifying tower for separation, extracting refined methanol from the tower top, and obtaining low-pressure rectifying tower kettle liquid from the tower kettle; tower bottom liquid of the low-pressure rectifying tower exchanges heat with tower bottom wastewater of the pressurizing rectifying tower through a pressurizing tower feeding preheater and then is introduced into the pressurizing rectifying tower for final separation, a gas phase at the top of the pressurizing rectifying tower is used for supplying heat to a reboiler of the low-pressure rectifying tower, and the gas phase at the top of the low-pressure rectifying tower is used for supplying heat to a reboiler of an atmospheric / vacuum rectifying tower. According to the method, light components are prevented from being accumulated in the ethylene glycol production process, the purity of methanol is improved, and meanwhile steam consumption is reduced by 40%-70%.

Description

Technical Field

[0001] This invention belongs to the field of coal chemical industry, specifically relating to a method and apparatus for methanol dehydration, upgrading, consumption reduction and recovery in the esterification stage of a coal-based syngas to ethylene glycol process. Background Technology

[0002] The coal-based syngas to ethylene glycol process mainly consists of two parts: CO oxidative coupling to dimethyl oxalate (DMO) and catalytic hydrogenation of DMO to ethylene glycol (EG).

[0003] The synthesis of dimethyl oxalate (DMO) from CO oxidative coupling mainly involves two reactions.

[0004] First, methyl nitrite (MN) and CO undergo an oxidative coupling reaction under the action of a catalyst to generate DMO. The reaction equation is as follows:

[0005] 2CH3ONO + 2CO → (COOCH3)2 + 2NO

[0006] This step is completed in the synthesis reactor.

[0007] The generated NO then undergoes an oxidative esterification reaction with methanol and oxygen (O2) to produce methyl nitrite (MN). The reaction equation is as follows:

[0008] 2CH3OH+2NO+1 / 2O2→2CH3ONO+H2O

[0009] This step is completed in the esterification tower. The reaction product, methyl nitrite (MN), is returned to the synthesis reactor and combined with CO oxidant to form dimethyl oxalate (DMO). The bottom liquid of the esterification tower contains not only the reaction product water, but also the raw material methanol and various light components produced by the side reactions.

[0010] The synthesis of DMO produces dimethyl carbonate (DMC) as a byproduct. The DMO product generated in the synthesis reactor enters the DMO section and is absorbed by methanol spraying in the DMO absorption tower. The methanol absorption liquid containing DMO and DMC enters the DMO distillation tower, where methanol and DMC are separated and recovered. Numerous documents describe the methanol recovery process in this procedure.

[0011] In the catalytic hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG), the DMO purified by the DMO distillation column is mixed with H2 and then fed into the hydrogenation reactor, where it reacts to produce ethylene glycol (EG) and methanol. Some literature describes methanol recovery in the ethylene glycol synthesis unit, such as invention patent CN105218305B, but this patent does not address methanol recovery from the esterification column.

[0012] As mentioned above, there are literature reports on methanol recovery in both the DMO and ethylene glycol processes.

[0013] Currently, there is little literature on methanol recovery from the bottom liquid of esterification towers. The bottom liquid phase of esterification towers contains a large amount of methanol, and the conventional method is to recover the methanol from a single tower. Patent CN204918418U mentions using a methanol recovery tower (single tower) to recover methanol from the esterification reaction tower, but this process consumes a lot of energy and does not remove the light components contained in the bottom liquid of the esterification tower, which will accumulate in the entire process system. Summary of the Invention

[0014] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and apparatus for methanol dehydration, upgrading, energy saving and recovery in the esterification stage of a coal-based syngas to ethylene glycol process. This reduces the energy consumption of the entire ethylene glycol production process, improves the purity of recovered methanol, and enhances the economic and social benefits of enterprises.

[0015] The technical solution for achieving the objective of this invention is as follows:

[0016] The first aspect of this invention is to provide a method for methanol dehydration, upgrading, energy saving, and recovery in the esterification stage of a coal-based syngas-to-ethylene glycol process, comprising the following steps:

[0017] The raw material is introduced into an atmospheric / vacuum distillation column for preliminary separation. The light component is collected from the top of the column, the refined methanol is collected from the side stream, and the bottom liquid of the atmospheric / vacuum distillation column is obtained from the bottom of the column.

[0018] The bottom liquid of the atmospheric / vacuum distillation column is introduced into a low-pressure distillation column for further separation. Refined methanol is collected from the top of the column, and the bottom liquid of the low-pressure distillation column is obtained from the bottom of the column.

[0019] The liquid in the bottom of the low-pressure distillation column is introduced into the pressurized distillation column for final separation after exchanging heat with the wastewater in the bottom of the pressurized distillation column through the feed preheater of the pressurized column. Refined methanol is collected from the top of the column, and wastewater is discharged from the bottom of the column.

[0020] The pressurized distillation column overhead vapor is used to heat the reboiler of the low-pressure distillation column, and the low-pressure distillation column overhead vapor is used to heat the reboiler of the atmospheric / low-pressure distillation column.

[0021] Furthermore, the raw material is a mixture of alcohol-containing wastewater from one or more operating units, including the esterification tower, nitric acid reduction tower / reduction reactor, esterification section circulating gas separator, and DMO light component removal tower, which has been neutralized with alkali.

[0022] Furthermore, the operating pressure of the atmospheric / vacuum distillation column is 30–200 kPa absolute, the reflux flow rate is 0.1–10 times the feed flow rate, and the theoretical plate number is 10–150.

[0023] Furthermore, the operating pressure of the low-pressure distillation column is 100–1500 kPa absolute, the reflux ratio is 0.8–20, and the number of theoretical plates is 20–150.

[0024] Furthermore, the operating pressure of the pressurized distillation column is 200–2000 kPa absolute pressure, the reflux ratio is 0.8–40, and the number of theoretical plates is 20–150.

[0025] Furthermore, the refined methanol collected from the atmospheric / vacuum distillation column, the refined methanol collected from the top of the low-pressure distillation column, and the refined methanol collected from the top of the pressurized distillation column are cooled by cooler one, cooler two, and cooler three, respectively, and then combined into high-purity methanol as the product output.

[0026] A second aspect of the present invention is to provide a methanol dehydration, upgrading, energy-saving, and recovery device for the method described above, comprising:

[0027] A normal / low-pressure distillation column, a low-pressure distillation column, and a pressurized distillation column are connected in sequence.

[0028] The lower part of the atmospheric / vacuum distillation column is connected to a reboiler, and the top of the column is connected to a condenser and a reflux tank.

[0029] The lower part of the low-pressure distillation column is connected to a low-pressure distillation column reboiler, and the top of the column is connected to the atmospheric / vacuum distillation column reboiler via a pipeline, and is also connected to a low-pressure distillation column reflux tank.

[0030] The lower part of the pressurized distillation column is connected to a pressurized distillation column reboiler, and the top of the column is connected to the low-pressure distillation column reboiler via a pipeline, and is also connected to a pressurized distillation column reflux tank.

[0031] The reboiler of the low-pressure distillation column is connected to the feed inlet of the pressurized distillation column via a pressurized column feed preheater.

[0032] Furthermore, the feed inlet of the atmospheric / vacuum distillation column is located in the middle or lower part of the column.

[0033] Furthermore, the atmospheric / reduced pressure distillation column, the low-pressure distillation column, and the pressurized distillation column are one or a combination of plate columns, bulk packed columns, or structured packed columns.

[0034] Furthermore, it also includes:

[0035] A reflux pump for an atmospheric / vacuum distillation column is connected between the reflux tank of the atmospheric / vacuum distillation column and the top of the atmospheric / vacuum distillation column;

[0036] A bottom pump for atmospheric / vacuum distillation column, connected between the bottom of the atmospheric / vacuum distillation column and the low-pressure distillation column;

[0037] A low-pressure distillation column reflux pump is connected between the low-pressure distillation column reflux tank and the top of the low-pressure distillation column, and is equipped with a refined methanol outlet;

[0038] A bottom pump for a low-pressure distillation column is connected between the bottom of the low-pressure distillation column and the feed preheater of the pressurized column;

[0039] The pressurized distillation column reflux pump is connected between the pressurized distillation column reflux tank and the top of the pressurized distillation column, and is equipped with a refined methanol outlet.

[0040] Furthermore, it also includes cooler one, cooler two, and cooler three, which are used to cool the refined methanol collected from the side of the atmospheric / vacuum distillation column, the refined methanol collected from the top of the low-pressure distillation column, and the refined methanol collected from the top of the pressurized distillation column, respectively, and combine them into high-purity methanol output.

[0041] The present invention has the following beneficial effects:

[0042] Most literature does not address methanol recovery in the esterification stage of existing coal-based syngas-to-ethylene glycol processes. In actual production, methanol recovery consumes a huge amount of energy, and the accumulation of light components in the recovered methanol due to their non-removal throughout the entire unit is a significant problem. This invention can remove light components from the recovered methanol, preventing their accumulation throughout the ethylene glycol production process, improving methanol purity, and reducing steam consumption by 40%-70%. This significantly reduces the energy consumption of the ethylene glycol production process, making the product highly competitive. Attached Figure Description

[0043] Figure 1 This is a process flow diagram used in this invention.

[0044] T1 is an atmospheric / vacuum distillation column, T2 is a low-pressure distillation column, T3 is a pressurized distillation column, V1 is a reflux tank for the atmospheric / vacuum distillation column, V2 is a reflux tank for the low-pressure distillation column, V3 is a reflux tank for the pressurized distillation column, E101 is a reboiler for the atmospheric / vacuum distillation column, E102 is a top condenser for the atmospheric / vacuum distillation column, E103 is cooler one, E201 is a reboiler for the low-pressure distillation column, E202 is cooler two, E301 is a reboiler for the pressurized distillation column, E302 is a feed preheater for the pressurized column, E303 is cooler three, V1 is a reflux tank for the atmospheric / vacuum distillation column, V... 2 is the reflux tank of the low-pressure distillation column, V3 is the reflux tank of the pressurized distillation column, P101 is the reflux pump of the atmospheric / vacuum distillation column, P102 is the bottom pump of the atmospheric / vacuum distillation column, P201 is the reflux pump of the low-pressure distillation column, P202 is the bottom pump of the low-pressure distillation column, P301 is the reflux pump of the pressurized distillation column, 1 is the feed, 2 is the light component, 3 is the side-collected refined methanol of the atmospheric / vacuum distillation column, 4 is the bottom liquid of the atmospheric / vacuum distillation column, 5 is the bottom liquid of the low-pressure distillation column, 6 is the refined methanol collected from the top of the low-pressure distillation column, 7 is the refined methanol collected from the top of the pressurized distillation column, 8 is the wastewater, and 9 is the high-purity methanol. Detailed Implementation

[0045] The following detailed description, in conjunction with specific implementation examples, provides a method and apparatus for methanol dehydration, upgrading, energy saving, and recovery in the esterification stage of a coal-based syngas to ethylene glycol process, as described in this invention. These examples are descriptive only and not limiting, and should not be construed as limiting the scope of protection of this invention.

[0046] like Figure 1 The illustrated methanol dehydration, upgrading, and energy-saving recovery process in the esterification stage of a coal-based syngas to ethylene glycol process includes an atmospheric / vacuum distillation column T1, a low-pressure distillation column T2, and a pressurized distillation column T3 connected in sequence. The lower parts of the atmospheric / vacuum distillation column T1, the low-pressure distillation column T2, and the pressurized distillation column T3 are respectively connected to an atmospheric / vacuum distillation column reboiler E101, a low-pressure distillation column reboiler E201, and a pressurized distillation column reboiler E301.

[0047] Raw material 1 is introduced into atmospheric / vacuum distillation column T1 for preliminary separation. Light component 2 is collected from the top of the column, refined methanol is collected from the side stream, and atmospheric / vacuum distillation column bottom liquid 4 is obtained from the bottom of the column. The atmospheric / vacuum distillation column bottom liquid 4 is introduced into low-pressure distillation column T2 for further separation. Refined methanol is collected from the top of the column, and low-pressure distillation column bottom liquid 5 is obtained from the bottom of the column. The low-pressure distillation column bottom liquid 5 is introduced into pressurized column T3 for final separation after exchanging heat with the wastewater 8 from the bottom of pressurized column T3 via pressurized column feed preheater E302. Refined methanol is collected from the top of the column, and wastewater 8 is discharged from the bottom of the column. The vapor phase from the top of pressurized column T3 is used to heat the reboiler E201 of the low-pressure distillation column, and the vapor phase from the top of low-pressure distillation column T2 is used to heat the reboiler E101 of the atmospheric / vacuum distillation column.

[0048] The atmospheric / vacuum distillation column T1 produces gaseous or liquid refined methanol via a side stream above the column's feed inlet. The atmospheric / vacuum distillation column T1 is connected to the feed inlet for raw material 1 in the middle or lower part.

[0049] The top of the atmospheric / vapor distillation column T1 is connected to the overhead condenser E102 via a pipeline. The overhead condenser E102 also extracts the non-condensable light component 2. The overhead condenser E102 is connected to the reflux tank V1 via a pipeline. The bottom of the reflux tank V1 is connected to the top of the atmospheric / vapor distillation column T1 via a pipeline through the reflux pump P101. The bottom of the atmospheric / vapor distillation column T1 is connected to the bottom pump P102 and the low-pressure distillation column T2 via pipelines, and the bottom liquid 4 of the atmospheric / vapor distillation column is pumped into the low-pressure distillation column T2.

[0050] The operating pressure of atmospheric / vacuum distillation column T1 is 30-200 kPa absolute pressure, the reflux flow rate is 0.1-10 times the feed flow rate, and the theoretical plate number is 10-150.

[0051] After the top gas of the low-pressure distillation column T2 is heated relative to the reboiler E101 of the atmospheric / vacuum distillation column, it is connected to the reflux tank V2 of the low-pressure distillation column through a pipeline. The bottom of the reflux tank V2 is connected to the top of the low-pressure distillation column T2 through the reflux pump P201 of the low-pressure distillation column via a pipeline. Moreover, refined methanol is also collected from the outlet of the reflux pump P201. The bottom of the low-pressure distillation column T2 is connected to the bottom pump P202 of the low-pressure distillation column, the feed preheater E302 of the pressurized column, and the pressurized distillation column T3 through pipelines, and the bottom liquid 5 of the low-pressure distillation column is pumped into the pressurized distillation column T3.

[0052] The operating pressure of the low-pressure distillation column T2 is 100–1500 kPa absolute pressure, the reflux ratio is 0.8–20, and the number of theoretical plates is 20–150.

[0053] After the top gas of the pressurized distillation column T3 is heated relative to the reboiler E201 of the low-pressure distillation column, it is connected to the pressurized distillation column reflux tank V3 through a pipeline. The bottom of the pressurized distillation column reflux tank V3 is connected to the top of the pressurized distillation column T3 through the pressurized distillation column reflux pump P301 via a pipeline. Furthermore, refined methanol is also collected from the outlet of the pressurized distillation column reflux pump P301.

[0054] The operating pressure of the pressurized distillation column T3 is 200–2000 kPa absolute pressure, the reflux ratio is 0.8–40, and the number of theoretical plates is 20–150.

[0055] The methanol 3 collected from the side of the atmospheric / vacuum distillation column, the methanol 6 collected from the top of the low-pressure distillation column, and the methanol 7 collected from the top of the pressurized distillation column are cooled by cooler E103, cooler E202, and cooler E303 respectively, and then combined into high-purity methanol 9 as a product for reuse.

[0056] The atmospheric / reduced pressure distillation column T1, low-pressure distillation column T2, and pressurized distillation column T3 are selected from one or a combination of plate columns, bulk packed columns, or structured packed columns.

[0057] Example 1

[0058] use Figure 1 The process flow diagram shown indicates that the raw materials are fed into the feed inlet of atmospheric / vacuum distillation column T1 at a feed rate of 41516 kg / h, containing 0.61 wt% methanol, 0.356 wt% water, 0.014 wt% light components, and 0.02 wt% dimethyl carbonate.

[0059] The operating pressure of atmospheric / vacuum distillation column T1 is 105 kPa absolute, the reflux flow rate is 0.85 times the feed flow rate, and the theoretical number of plates is 50.

[0060] The operating pressure of the low-pressure distillation column T2 is 300 kPa absolute, the reflux ratio is 1.6, and the theoretical plate number is 50.

[0061] The operating pressure of the pressurized distillation column T3 is 800 kPa absolute pressure, the reflux ratio is 2.2, and the theoretical plate number is 50.

[0062] The recovered refined methanol 9 has a methanol purity of 96.4 wt%, a water content of 34 ppm, a DMC content of 3.3 wt%, and a light component of 0.3 wt%. The energy consumption of the entire process is 6.98 gcal / h.

[0063] Example 2

[0064] use Figure 1 The process flow diagram shown indicates that the raw materials are fed into the feed inlet of atmospheric / vacuum distillation column T1 at a feed rate of 41516 kg / h, containing 0.61 wt% methanol, 0.356 wt% water, 0.014 wt% light components, and 0.02 wt% dimethyl carbonate.

[0065] The operating pressure of atmospheric / vacuum distillation column T1 is 65 kPa absolute, the reflux rate is 0.68 times the feed rate, and the theoretical number of plates is 70.

[0066] The operating pressure of the low-pressure distillation column T2 is 220 kPa absolute, the reflux ratio is 1.15, and the theoretical plate number is 70.

[0067] The operating pressure of the pressurized distillation column T3 is 600 kPa absolute pressure, the reflux ratio is 1.6, and the theoretical plate number is 70.

[0068] The recovered refined methanol 9 has a methanol purity of 96.4 wt%, a water content of 27 ppm, a DMC content of 3.3 wt%, and a light component of 0.3 wt%. The energy consumption of the entire process is 5.66 gcal / h.

[0069] Example 3

[0070] use Figure 1 The process flow diagram shown indicates that the raw materials are fed into the feed inlet of atmospheric / vacuum distillation column T1 at a feed rate of 41516 kg / h, containing 0.61 wt% methanol, 0.356 wt% water, 0.014 wt% light components, and 0.02 wt% dimethyl carbonate.

[0071] The operating pressure of atmospheric / vacuum distillation column T1 is 65 kPa absolute, the reflux rate is 0.8 times the feed rate, and the theoretical number of plates is 50.

[0072] The operating pressure of the low-pressure distillation column T2 is 220 kPa absolute, the reflux ratio is 1.4, and the theoretical plate number is 50.

[0073] The operating pressure of the pressurized distillation column T3 is 600 kPa absolute pressure, the reflux ratio is 1.9, and the theoretical plate number is 50.

[0074] The recovered refined methanol 9 has a methanol purity of 96.4 wt%, a water content of 33 ppm, a DMC content of 3.3 wt%, and a light component of 0.3 wt%. The energy consumption of the entire process is 6.31 gcal / h.

[0075] Comparative Example

[0076] Using a traditional single-tower process with 70 theoretical plates, methanol is collected from the top of the tower at a feed rate of 41,516 kg / h, containing 0.61 wt% methanol, 0.356 wt% water, 0.014 wt% light components, and 0.02 wt% dimethyl carbonate. The recovered methanol has a purity of 94.69 wt% and a light component content of 2.1 wt%, with an energy consumption as high as 14.51 gcal / h.

[0077] The comparison revealed that, compared to the current process of the comparative example, Example 1 consumed only 48.1% of the energy of the comparative example, saving 51.9% of energy. The methanol purity of 96.4% was much higher than the 94.69% of the current process, and the content of light components dropped sharply to 0.3%, which was only 14.3% of the original.

[0078] Compared with the current process in the comparative example, Example 2 consumes only 39.0% of the energy of the comparative example, saving 61.0% of energy. The methanol purity of 96.4% is much higher than the 94.69% of the current process, and the content of light components drops sharply to 0.3%, which is only 14.3% of the original.

[0079] Compared with the current process in the comparative example, Example 3 consumes only 43.5% of the energy of the comparative example, saving 56.5% of energy. The methanol purity of 96.4% is much higher than the 94.69% of the current process, and the content of light components drops sharply to 0.3%, which is only 14.3% of the original.

Claims

1. A method for methanol dehydration, upgrading, energy saving, and recovery in the esterification stage of a coal-based syngas-to-ethylene glycol process, characterized in that: The raw material (1) is introduced into the atmospheric / vacuum distillation column (T1) for preliminary separation. The light component (2) is collected from the top of the column, the refined methanol is collected from the side stream, and the bottom liquid (4) of the atmospheric / vacuum distillation column is obtained from the bottom of the column. The bottom liquid (4) of the atmospheric / vacuum distillation column is introduced into the low-pressure distillation column (T2) for further separation. Refined methanol is collected from the top of the column, and the bottom liquid (5) of the low-pressure distillation column is obtained from the bottom of the column. The liquid in the bottom of the low-pressure distillation column (5) is introduced into the pressure distillation column (T3) for final separation after exchanging heat with the wastewater (8) in the bottom of the pressure distillation column (T3) through the feed preheater (E302). The refined methanol is collected from the top of the column and the wastewater (8) is discharged from the bottom of the column. The vapor phase from the top of the pressurized distillation column (T3) is used to heat the reboiler (E201) of the low-pressure distillation column, and the vapor phase from the top of the low-pressure distillation column (T2) is used to heat the reboiler (E101) of the atmospheric / vacuum distillation column.

2. The method according to claim 1, characterized in that, The raw material (1) is a mixture of alcohol-containing wastewater from one or more operating units in the esterification tower, nitric acid reduction tower / reduction reactor, esterification section circulating gas separator, and DMO light removal tower, which has been neutralized by adding alkali.

3. The method according to claim 1, characterized in that, The operating pressure of the atmospheric / vacuum distillation column (T1) is 30-200 kPa absolute pressure, the reflux flow rate is 0.1-10 times the feed flow rate, and the theoretical plate number is 10-150.

4. The method according to claim 1, characterized in that, The low-pressure distillation column (T2) operates at an absolute pressure of 100–1500 kPa, a reflux ratio of 0.8–20, and has a theoretical plate number of 20–150.

5. The method according to claim 1, characterized in that, The pressurized distillation column (T3) operates at an absolute pressure of 200–2000 kPa, a reflux ratio of 0.8–40, and has 20–150 theoretical plates.

6. The method according to claim 1, characterized in that, The methanol collected from the side of the atmospheric / reduced pressure distillation column (3), the methanol collected from the top of the low-pressure distillation column (6), and the methanol collected from the top of the pressurized distillation column (7) are cooled by cooler one (E103), cooler two (E202), and cooler three (E303) respectively, and then combined into high-purity methanol (9) as the product output.

7. A methanol dehydration, upgrading, energy-saving, and recovery device for implementing the method according to any one of claims 1-6, characterized in that, include: The atmospheric / vacuum distillation column (T1), the low-pressure distillation column (T2), and the pressurized distillation column (T3) are connected in sequence. The atmospheric / vacuum distillation column (T1) is connected to a reboiler (E101) at the bottom and to a condenser (E102) and a reflux tank (V1) at the top. The lower part of the low-pressure distillation column (T2) is connected to the low-pressure distillation column reboiler (E201), and the top of the column is connected to the atmospheric / vacuum distillation column reboiler (E101) through a pipeline, and is also connected to the low-pressure distillation column reflux tank (V2). The lower part of the pressurized distillation column (T3) is connected to the pressurized distillation column reboiler (E301), and the top of the column is connected to the low-pressure distillation column reboiler (E201) through a pipeline, and is also connected to the pressurized distillation column reflux tank (V3). The bottom of the low-pressure distillation column (T2) is connected to the feed inlet of the pressurized distillation column (T3) via the pressurized column feed preheater (E302).

8. The apparatus according to claim 7, characterized in that, The atmospheric / reduced pressure distillation column (T1), low-pressure distillation column (T2), and pressurized distillation column (T3) are one or a combination of plate columns, bulk packed columns, or structured packed columns.

9. The apparatus according to claim 7, characterized in that, Also includes: The atmospheric / vacuum distillation column reflux pump (P101) is connected between the atmospheric / vacuum distillation column reflux tank (V1) and the top of the atmospheric / vacuum distillation column (T1); The bottom pump (P102) of the atmospheric / vacuum distillation column is connected between the bottom of the atmospheric / vacuum distillation column (T1) and the low-pressure distillation column (T2); The low-pressure distillation column reflux pump (P201) is connected between the low-pressure distillation column reflux tank (V2) and the top of the low-pressure distillation column (T2), and is equipped with a refined methanol outlet; The low-pressure distillation column bottom pump (P202) is connected between the bottom of the low-pressure distillation column (T2) and the pressurized column feed preheater (E302); The pressurized distillation column reflux pump (P301) is connected between the pressurized distillation column reflux tank (V3) and the top of the pressurized distillation column (T3), and is equipped with a refined methanol outlet.

10. The apparatus according to claim 7, characterized in that, It also includes cooler one (E103), cooler two (E202) and cooler three (E303), which are used to cool the methanol collected from the side of the atmospheric / reduced pressure distillation column (3), the methanol collected from the top of the low pressure distillation column (6) and the methanol collected from the top of the pressurized distillation column (7), and combine them into high-purity methanol (9) for output.

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