Rectification system for methanol production

Abstract

The application discloses a kind of rectification systems for methanol production, including crude methanol feeding unit, methanol refining unit and product discharge unit, the discharge end of crude methanol feeding unit is communicated with the feeding end of methanol refining unit, the product discharge end of methanol refining unit is communicated with product discharge unit.The methanol refining unit includes pre-distillation column, pressurized rectification tower and atmospheric rectification tower.The application adopts pre-distillation, pressurization and atmospheric three-tower integrated process, cooperates alkali liquor neutralization, extraction water removes light, fine control means such as fusel oil side line extraction, can effectively remove acid, ester, alcohol, water and other impurities in by-product crude methanol of ester exchange method, can stably produce high-purity refined methanol product.

Description

Technical Field

[0001] This invention relates to the field of methanol production technology, and more particularly to a distillation system for methanol production. Background Technology

[0002] Ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are high-performance solvents for lithium-ion battery electrolytes. Currently, industrially, ethyl methyl carbonate and diethyl carbonate are mainly produced through transesterification of dimethyl carbonate (DMC) with ethanol under catalysis. This reaction co-produces a large amount of methanol. Furthermore, to fully utilize the raw materials, industrial production often involves processes such as disproportionation reactions, resulting in a complex composition of the final crude methanol system, containing various impurities such as methanol, water, ethanol, and dimethyl carbonate.

[0003] In existing technologies, the purification of crude methanol, a byproduct of the transesterification process, typically employs traditional single-tower or double-tower distillation processes. However, these traditional processes suffer from the following significant drawbacks in actual operation: First, due to the complex composition of impurities in crude methanol, particularly components with boiling points similar to or exhibiting azeotropic tendencies, such as water and ethanol, conventional distillation struggles to achieve efficient separation, making it difficult to consistently achieve high-purity standards for the final product, methanol (especially its water content). Second, traditional distillation processes consume enormous amounts of energy. The reboiler in the column requires a large external heat source (such as steam), while the heat from the overhead vapor phase needs to be carried away by circulating water through a condenser, resulting in significant energy waste. This is severely inconsistent with the current trends of green chemistry and energy conservation.

[0004] Therefore, how to provide a methanol refining system that can effectively remove impurities, improve product purity, and significantly reduce energy consumption has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the problems mentioned in the background section, the present invention provides a distillation system for methanol production.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A methanol production distillation system includes a crude methanol feed unit, a methanol refining unit, and a product discharge unit. The discharge end of the crude methanol feed unit is connected to the feed end of the methanol refining unit, and the product discharge end of the methanol refining unit is connected to the product discharge unit. The core improvement lies in that the methanol refining unit includes a pre-distillation column, a pressurized distillation column, and an atmospheric distillation column.

[0008] The specific connection relationships are as follows:

[0009] The pre-distillation column has a crude methanol inlet in the middle of its body, which is connected to the outlet of the crude methanol feed unit. The top of the pre-distillation column has a first gas phase outlet, which is sequentially connected to a first condenser and a first reflux tank. The liquid phase outlet of the first reflux tank is divided into two paths: the first path connects to the top reflux port of the pre-distillation column, and the second path is a non-condensable gas delivery pipeline. The pre-distillation column also has an alkali inlet and an extraction water inlet. The bottom of the pre-distillation column has a light methanol removal outlet, which is connected to the middle inlet of the pressurized distillation column via a pressurized feed pump.

[0010] The pressurized distillation column is equipped with a first reboiler in its reboiler. A second gas phase outlet is located at the top of the pressurized distillation column. This second gas phase outlet is connected to the shell-side gas phase inlet of the second reboiler located in the reboiler of the atmospheric distillation column. The shell-side liquid phase outlet of the second reboiler is connected to a second reflux trough. The liquid phase outlet of the second reflux trough is divided into two paths: the first path is connected to the top reflux port of the pressurized distillation column, and the second path is connected to the product discharge unit. The reboiler of the pressurized distillation column is equipped with a concentrated methanol discharge port, which is connected to the upper-middle feed port of the atmospheric distillation column via a pressure reducing valve.

[0011] The atmospheric distillation column has a third gas phase outlet at the top, which is connected in sequence to a third condenser and a third reflux tank. The liquid phase outlet of the third reflux tank is divided into two paths: the first path is connected to the top reflux port of the atmospheric distillation column, and the second path is connected to the product discharge unit. The lower part of the atmospheric distillation column has a fusel oil side stream outlet, and the bottom of the atmospheric distillation column has a wastewater outlet.

[0012] In a preferred embodiment of the present invention, the crude methanol feed unit includes a crude methanol buffer tank, a precision filter, and a feed preheater connected sequentially by pipelines. The outlet of the feed preheater is connected to the crude methanol inlet of the pre-distillation column via a feed pipeline, and a feed flow regulating valve is installed on the feed pipeline. The crude methanol is first filtered to remove any potentially carried solid particles and catalyst powder, and then preheated to its bubble point temperature before entering the pre-distillation column. This design protects the trays or packing in the subsequent distillation column from clogging, while also reducing the temperature rise burden on the pre-distillation column.

[0013] As a preferred embodiment of the present invention, the tank body of the first reflux tank is provided with a lye feed inlet and an extraction water feed inlet. The lye feed inlet is connected to the lye preparation tank through a lye metering pump, and the extraction water feed inlet is connected to the process condensate feed pipeline through an extraction water regulating valve. Setting the addition points of lye and extraction water in the first reflux tank can, on the one hand, make them evenly dispersed by the mixing and dilution effect of the reflux liquid, and on the other hand, also play a certain role in anti-corrosion protection for the condenser. Adding lye is to neutralize the trace organic acids that may be carried in the crude methanol to prevent equipment corrosion; adding extraction water is to enhance the separation effect of methanol and low-boiling organic impurities (such as dimethyl carbonate) in the non-condensable gas.

[0014] As a preferred embodiment of the present invention, the first reboiler supporting the pressurized distillation column is a shell-and-tube heat exchanger. The tube-side inlet and outlet of the first reboiler are respectively connected to the liquid-phase circulation port at the bottom of the pressurized distillation column, and the shell-side inlet and outlet of the first reboiler are respectively connected to the medium-pressure steam supply pipeline and the steam condensate recovery pipeline. Using external medium-pressure steam as the heat source provides sufficient heat to establish a stable temperature gradient for the pressurized distillation column.

[0015] As a preferred embodiment of the present invention, the second reboiler supporting the atmospheric distillation column is a shell-and-tube heat exchanger. The tube-side inlet and outlet of the second reboiler are respectively connected to the liquid-phase circulation port at the bottom of the atmospheric distillation column, and the gas-phase inlet at the shell side of the second reboiler is directly connected to the second gas-phase outlet of the pressurized distillation column, and the liquid-phase outlet at the shell side is connected to the feed inlet of the second reflux tank. This is the core structure of the present invention to achieve energy conservation and consumption reduction - the differential pressure heat coupling technology. The high-temperature and high-pressure gas-phase material discharged from the top of the pressurized distillation column is directly used as the heat source for the reboiler at the bottom of the atmospheric distillation column, that is, using the heat energy at a high temperature level to heat the material at a low temperature level, thereby greatly reducing the external steam consumption originally required by the atmospheric distillation column. At the same time, the gas phase at the top of the pressurized distillation column is condensed by itself, which also reduces the consumption of circulating water for its original condenser, achieving a double energy-saving effect.

[0016] As a preferred embodiment of the present invention, there are 2 - 4 side draw outlets for fusel oil on the atmospheric distillation column arranged at intervals along the height direction of the tower body. Each side draw outlet for fusel oil is successively connected to a fusel oil cooler and a fusel oil storage tank through a draw pipeline, and a draw flow regulating valve is provided on the draw pipeline. Setting multiple draw outlets at different heights can flexibly select the best draw position according to the actual working conditions and the distribution of the fusel oil composition (mainly a mixture of ethanol and water), achieve precise removal of impurities, and ensure the product quality at the top and bottom of the tower.

[0017] As a preferred embodiment of the present invention, the product discharging unit includes a product cooler and a refined methanol storage tank. The product outlets of the second reflux tank supporting the pressurized distillation column and the product outlets of the third reflux tank supporting the atmospheric distillation column are both connected to the feed end of the product cooler through product pipelines, and the discharge end of the product cooler is connected to the refined methanol storage tank. This refining system can extract qualified products from two positions, with strong production flexibility; the products are uniformly cooled and then stored, and the process is simple.

[0018] As a preferred embodiment of the present invention, the second reboiler is a vertical shell-and-tube heat exchanger, and a plurality of flow guiding plates are arranged at intervals along the axial direction inside the shell side. The flow guiding plates divide the tube bundle into several independent heat exchange sections; each of the flow guiding plates consists of a channel for steam to pass through in the middle area and a liquid collecting structure for collecting condensate in the edge area.

[0019] As a preferred embodiment of the present invention, the flow guiding plate has an umbrella-shaped structure, with a high middle and a low edge. The umbrella surface of the umbrella-shaped structure constitutes a flow guiding surface for guiding the condensate to flow towards the edge, and a ring-shaped liquid collecting groove is arranged at the edge of the umbrella-shaped structure.

[0020] As a preferred embodiment of the present invention, a vertical downcomer is connected to the bottom of each of the ring-shaped liquid collecting grooves, and the lower end of the downcomer leads to the bottom of the shell side; a layered overflow chamber is arranged at the bottom of the shell side of the second reboiler, and each of the downcomers flows into the layered overflow chamber. The layered overflow chamber is provided with a methanol overflow port, and the methanol overflow port is connected to the second reflux tank; a ring-shaped porous distributor is arranged at the gas inlet of the second reboiler for uniformly distributing the high-temperature steam from the pressurized distillation column to the shell side; a water collecting tank is arranged at the bottom of the ring-shaped liquid collecting groove, and a drain port is arranged at the bottom end of the water collecting tank.

[0021] Compared with the prior art, the beneficial effects of the present invention are reflected in three aspects:

[0022] 1. By adopting the integrated process of pre-distillation, pressurization and atmospheric pressure in three towers, and cooperating with refined control means such as lye neutralization, extraction water de-lightening, and side-line extraction of fusel oil, impurities such as acids, esters, alcohols, and water in the by-product crude methanol from the transesterification method can be effectively removed, and high-purity refined methanol products can be stably produced.

[0023] 2. By constructing a differential pressure thermally coupled distillation structure, the high-temperature gas phase at the top of the pressurized distillation column is directly used as the heat source for the bottom of the atmospheric distillation column, making full use of the latent heat of the internal materials of the system. Compared with the traditional process, steam consumption can be saved, and at the same time, the circulating water consumption of the corresponding top condenser is saved, and the energy-saving effect is remarkable.

[0024] 3. The pressure and temperature gradients of each tower are independently controllable, the process design is reasonable, and the anti-interference ability is strong. It can adapt to the fluctuations of the flow rate and composition of the crude methanol from the upstream section, ensuring the long-term stable operation of the entire refining system.

[0025] 4. Through the coordinated structure of the umbrella-shaped guide plate, the annular collection tank, and the vertical downcomer, steam and condensate in the shell side are separated and do not interfere with each other. The condensate generated in each heat exchange section is collected in a timely manner and discharged independently, completely avoiding the gas resistance problem caused by condensate accumulation between the tube bundles and submerging the heat exchange tubes. At the same time, it eliminates tube bundle vibration caused by high-speed airflow impacting irregular liquid flow. Combined with the uniform gas distribution of the annular porous distributor, the heat exchange load of each section is balanced, the heat transfer efficiency is significantly improved, the operational flexibility is enhanced, and the service life of the equipment is extended.

[0026] 5. The stratified overflow chamber at the bottom of the shell side utilizes the stagnant liquid pool where the flow rate drops sharply after the condensate enters, providing sufficient residence time. This allows for gravity stratification of light and heavy components based on density differences: the upper layer of high-purity refined methanol is collected through the methanol overflow port and sent to the reflux tank, while the lower layer of water-containing and water-rich methanol impurities settles into the water collection tank and is discharged through the drain port. This structure enables the second reboiler to perform both efficient heat exchange and liquid-phase pre-fractionation functions, intercepting heavy impurities before they enter the reflux system, thus improving the stability of the reflux material composition. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of the process of this invention;

[0029] Figure 2 Front view of the second reboiler of the present invention;

[0030] Figure 3 A front-view sectional view of the second reboiler of the present invention;

[0031] Figure 4 A perspective cross-sectional view of the second reboiler of the present invention;

[0032] Figure 5 A schematic diagram of the distribution position of the guide plate in this invention;

[0033] In the diagram: 1. Crude methanol feed unit; 2. Methanol refining unit; 3. Product discharge unit; 4. Pre-distillation column; 5. First condenser; 6. First reflux tank; 7. Pressurized feed pump; 8. Pressurized distillation column; 9. First reboiler; 10. Second reboiler; 11. Second reflux tank; 12. Atmospheric distillation column; 13. Third condenser; 14. Third reflux tank; 15. Crude methanol buffer tank; 16. Precision filter; 17. Feed preheater; 20. Fusel oil cooler; 21. Fusel oil storage tank; 22. Product cooler; 23. Refined methanol storage tank; 24. Guide plate; 25. Tube bundle; 26. Annular collection tank; 27. Vertical downcomer; 28. Stratified overflow chamber; 29. ​​Annular porous distributor; 30. Water collection tank; 31. Drain outlet; 32. Methanol overflow outlet. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] Reference Figure 1 As attached Figure 1 As shown, this embodiment provides a distillation system for methanol production. This system is designed for crude methanol produced as a byproduct of the transesterification process for the production of ethyl methyl carbonate (EMC) and diethyl carbonate (DEC). The system has a processing capacity that matches the annual production capacity of 50,000 tons of EMC and 15,000 tons of DEC.

[0037] This system consists of three parts: crude methanol feeding unit 1, methanol refining unit 2, and product discharge unit 3.

[0038] The crude methanol feed unit 1 mainly consists of a crude methanol buffer tank 15, a precision filter 16, and a feed preheater 17 connected in series via pipelines. Crude methanol (containing methanol, water, ethanol, DMC, etc.) from the upstream unit tank area first enters the crude methanol buffer tank 15 for buffering and homogenization, and is then pumped to the precision filter 16 to remove any catalyst powder that may be entrained. After being preheated to 90-130°C by the feed preheater 17, it is then transported to the crude methanol inlet in the middle of the pre-distillation column 4 of the methanol refining unit 2 via a pipeline equipped with a feed flow regulating valve.

[0039] The methanol refining unit 2 includes three core pieces of equipment: a pre-distillation column 4, a pressurized distillation column 8, and an atmospheric distillation column 12.

[0040] Pre-distillation column 4 operates at atmospheric pressure and is used to remove light components with boiling points lower than methanol and non-condensable gases. The gas discharged from the first vapor outlet at the top of pre-distillation column 4 (rich in light components such as DMC) enters the first condenser 5, and the condensate enters the first reflux tank 6. In the first reflux tank 6, a small amount of dilute alkali solution is injected by an alkali metering pump to neutralize acidic substances, while process condensate is added by an extraction water regulating valve, utilizing the principle of extractive distillation to improve the separation efficiency of light components. Most of the liquid in the first reflux tank 6 is refluxed to the top of the column, and a small amount of byproduct rich in light component impurities is sent as non-condensable gas for further processing. The aqueous methanol obtained from the bottom of the column, after being de-pressurized by the pressurized feed pump 7, is sent to the middle feed inlet of the pressurized distillation column 8.

[0041] The pressurized distillation column 8 operates under pressure (approximately 0.8 MPaG). The reboiler is heated by external medium-pressure steam via the first reboiler 9 (a shell-and-tube heat exchanger). High-boiling-point concentrated methanol containing water is collected from the reboiler, depressurized by a pressure reducing valve, and then fed into the upper-middle feed inlet of the atmospheric distillation column 12. High-temperature, high-pressure methanol vapor from the top of the column is directly drawn from the second vapor outlet and used as a heat source in the shell side of the second reboiler 10 of the atmospheric distillation column 12. This vapor exchanges heat with the tube-side material in the reboiler of the atmospheric distillation column 12 within the shell side of the second reboiler 10. The vapor itself is condensed into liquid and flows into the second reflux tank 11. Most of the methanol in the second reflux tank 11 is returned to the top of the pressurized distillation column 8 as reflux liquid, while a small portion is collected as product and sent to the product discharge unit 3.

[0042] Atmospheric distillation column 12 is used to remove water and fusel oil. The reboiler is heated by the second reboiler 10 (i.e., pressurized overhead steam). Refined methanol vapor exits from the third vapor outlet at the top of the column, is condensed by the third condenser 13, and then enters the third reflux tank 14. Part of it is refluxed back to the top of the column, and the other part is collected as product. Water and higher-boiling-point fusel oil accumulate within the column. The fusel oil fraction is drawn off through two fusel oil side-stream outlets located in the lower part of the column, cooled by the fusel oil cooler 20, and collected in the fusel oil storage tank 21. Finally, wastewater containing almost no organic matter is discharged from the reboiler wastewater outlet for sewage treatment.

[0043] The product discharge unit 3 mainly includes a product cooler 22 and a refined methanol storage tank 23. The refined methanol products from the second reflux tank 11 and the third reflux tank 14 are collected, cooled by the product cooler 22, and finally sent to the refined methanol storage tank 23 for analysis, testing and storage.

[0044] Example 2

[0045] Reference Figure 2-5Based on Example 1, the second reboiler 10 is a vertical shell-and-tube heat exchanger, with a number of guide plates 24 spaced axially inside its shell side. The guide plates 24 divide the tube bundle 25 into several independent heat exchange sections. Each guide plate 24 consists of a channel in the middle area for steam to pass through and a liquid collection structure in the edge area for collecting condensate.

[0046] The guide plate 24 has an umbrella-shaped structure, with a high center and low edges. The umbrella surface of the umbrella-shaped structure forms a guide surface to guide the condensate to the edge, while the steam passes through the central channel below the umbrella surface. The edge of the umbrella-shaped structure is provided with an annular liquid collection tank 26 to collect the condensate flowing down along the guide surface.

[0047] Each annular liquid collection tank 26 has a vertical downcomer 27 connected to its bottom, and the lower end of the downcomer 27 leads to the bottom of the shell.

[0048] Guided by the downcomer 27, the condensate can be quickly and smoothly discharged from each heat exchange section, completely avoiding the accumulation of condensate between the tube bundles and the submersion of the heat exchange tubes, effectively eliminating the air resistance problem in conventional designs. At the same time, steam and condensate follow separate paths, the flow field in the shell side is stable, and the impact vibration of high-speed airflow on the tube bundle is greatly reduced.

[0049] The second reboiler 10 has a layered overflow chamber 28 at the bottom of the shell side. All downcomers 27 converge into the layered overflow chamber 28. The layered overflow chamber 28 is provided with a methanol overflow port 32, which is connected to the second reflux tank 11.

[0050] The stratified overflow chamber 28 can utilize density differences to perform preliminary stratification and separation of different components, which is beneficial to improving the stability of the composition of the reflux material. The bottom of the annular liquid collection tank 26 is provided with a water collection tank 30, and the bottom end of the water collection tank 30 is provided with a drain outlet 31. The cross-section of the chamber is much larger than the total cross-sectional area of ​​the downcomer 27. After the liquid enters, the flow rate drops sharply, forming a relatively static liquid pool. The sufficient volume ensures that the liquid has enough residence time in the chamber. If the condensate contains trace amounts of aqueous phase or water-rich methanol (with a higher density), under the action of gravity, these components with higher density will gradually sink to the bottom of the chamber (into the water collection tank 30 and discharged through the drain outlet 31), while the upper layer is purer methanol (flowing out through the methanol overflow outlet 32).

[0051] An annular porous distributor 29 is provided at the gas inlet 32 ​​of the second reboiler 10 to uniformly distribute the high-temperature steam from the pressurized distillation column 8 to the shell side.

[0052] High-temperature steam from the top of pressurized distillation column 8 first enters the annular porous distributor 29, and after being evenly distributed by it, it enters the shell-side heat exchange area. This avoids the flow deviation and local overheating caused by the steam directly scouring the local tube bundle, making the heat exchange load of each section of tube bundle 25 more balanced.

[0053] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0054] In this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," "link," and "fix" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0055] The control method of this invention is automatic control through a controller. The control circuit of the controller can be implemented by simple programming by those skilled in the art. The power supply is also common knowledge in the art. Furthermore, since this invention is mainly used to protect mechanical devices, the control method and circuit connection will not be explained in detail here.

[0056] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A distillation system for methanol production, comprising a crude methanol feed unit (1), a methanol refining unit (2), and a product discharge unit (3), wherein the discharge end of the crude methanol feed unit (1) is connected to the feed end of the methanol refining unit (2), and the product discharge end of the methanol refining unit (2) is connected to the product discharge unit (3), characterized in that, The methanol refining unit (2) includes a pre-distillation column (4), a pressurized distillation column (8), and an atmospheric distillation column (12). The pressurized distillation column (8) is equipped with a first reboiler (9) at its bottom and a second gas phase outlet at its top. The second gas phase outlet is connected to the shell-side gas phase inlet of the second reboiler (10) at the bottom of the atmospheric distillation column (12). The shell-side liquid phase outlet of the second reboiler (10) is connected to a second reflux tank (11). The liquid phase outlet of the second reflux tank (11) is divided into two paths, the first path of which is connected to the pressurized distillation column. The top reflux port of the column (8) is connected to the product discharge unit (3) via a second path; the bottom of the pressurized distillation column (8) is provided with a concentrated methanol discharge port, which is connected to the atmospheric distillation column (12) via a pressure reducing valve; the top of the atmospheric distillation column (12) is provided with a third gas phase outlet, which is connected in sequence to a third condenser (13) and a third reflux tank (14); the liquid phase outlet of the third reflux tank (14) is divided into two paths, the first path is connected to the top reflux port of the atmospheric distillation column (12), and the second path is connected to the product discharge unit (3).

2. The distillation system for methanol production according to claim 1, characterized in that: The pre-distillation column (4) has a crude methanol inlet in the middle of its column body. The top of the pre-distillation column (4) has a first gas phase outlet, which is sequentially connected to a first condenser (5) and a first reflux tank (6). The liquid phase outlet of the first reflux tank (6) is divided into two paths: the first path connects to the top reflux port of the pre-distillation column (4), and the second path is a non-condensable gas delivery pipeline. The bottom of the pre-distillation column (4) has a light methanol removal outlet. The inlet is connected to the pressurized distillation column (8) via a pressurized feed pump (7); the crude methanol feed unit (1) includes a crude methanol buffer tank (15), a precision filter (16) and a feed preheater (17) connected in sequence via pipelines. The outlet of the feed preheater (17) is connected to the crude methanol inlet of the pre-distillation column (4) via a feed pipeline. A feed flow regulating valve is provided on the feed pipeline. The crude methanol inlet is connected to the outlet of the crude methanol feed unit (1).

3. The distillation system for methanol production according to claim 1, characterized in that: The pre-distillation column (4) is also provided with an alkali inlet and an extraction water inlet. The first reflux tank (6) is provided with an alkali inlet and an extraction water inlet. The alkali inlet is connected to the alkali preparation tank through an alkali metering pump. The extraction water inlet is connected to the process condensate feed line through an extraction water regulating valve.

4. A distillation system for methanol production according to claim 1, characterized in that: The first reboiler (9) of the pressurized distillation column (8) is a shell-and-tube heat exchanger. The tube side inlet and tube side outlet of the first reboiler (9) are connected to the liquid phase circulation port of the bottom of the pressurized distillation column (8), respectively. The shell side inlet and shell side outlet of the first reboiler (9) are connected to the medium-pressure steam supply pipeline and the steam condensate recovery pipeline, respectively.

5. A distillation system for methanol production according to claim 1, characterized in that: The second reboiler (10) supporting the atmospheric distillation column (12) is a shell-and-tube heat exchanger. The inlet and outlet of the tube side of the second reboiler (10) are respectively connected to the liquid-phase circulation port at the bottom of the atmospheric distillation column (12). The gas-phase inlet of the shell side of the second reboiler (10) is directly connected to the second gas-phase outlet of the pressurized distillation column (8), and the liquid-phase outlet of the shell side is connected to the feed port of the second reflux tank (11).

6. A distillation system for methanol production according to claim 1, characterized in that: A fusel oil side draw outlet is provided in the middle and lower part of the tower body of the atmospheric distillation column (12). There are 2 - 4 fusel oil side draw outlets provided at intervals along the height direction of the tower body of the atmospheric distillation column (12). Each fusel oil side draw outlet is sequentially connected to a fusel oil cooler (20) and a fusel oil storage tank (21) through a draw pipeline. A draw flow regulating valve is provided on the draw pipeline. A waste water outlet is provided at the bottom of the atmospheric distillation column (12).

7. A distillation system for methanol production according to claim 1, characterized in that: The product discharging unit (3) includes a product cooler (22) and a refined methanol storage tank (23). The product outlets of the second reflux tank (11) supporting the pressurized distillation column (8) and the product outlets of the third reflux tank (14) supporting the atmospheric distillation column (12) are both connected to the feed end of the product cooler (22) through a product pipeline. The discharging end of the product cooler (22) is connected to the refined methanol storage tank (23).

8. A distillation system for methanol production according to claim 1, characterized in that: The second reboiler (10) is a vertical shell-and-tube heat exchanger. A number of flow guiding discs (24) are arranged at intervals along the axial direction inside the shell side. The flow guiding discs (24) divide the tube bundle (25) into several independent heat exchange sections; each flow guiding disc (24) consists of a channel for steam to pass through in the middle area and a liquid collecting structure for collecting condensate in the edge area.

9. A distillation system for methanol production according to claim 8, characterized in that: The flow guiding disc (24) has an umbrella-shaped structure, with a higher middle and a lower edge. The umbrella surface of the umbrella-shaped structure constitutes a flow guiding surface for guiding the condensate to flow towards the edge. A ring-shaped liquid collecting groove (26) is provided at the edge of the umbrella-shaped structure.

10. A distillation system for methanol production according to claim 9, characterized in that: The bottom of each ring-shaped liquid collecting groove (26) is connected to a vertical downcomer (27). The lower end of the downcomer (27) leads to the bottom of the shell side; a stratified overflow chamber (28) is provided at the bottom of the shell side of the second reboiler (10). Each downcomer (27) flows into the stratified overflow chamber (28). A methanol overflow port (32) is provided in the stratified overflow chamber (28), and the methanol overflow port (32) is connected to the second reflux tank (11); an annular porous distributor (29) is provided at the gas inlet (32) of the second reboiler (10) for evenly distributing the high-temperature steam from the pressurized distillation column (8) to the shell side; a water collecting tank (30) is provided at the bottom of the ring-shaped liquid collecting groove (

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