Method and system for purifying crude methanol by membrane separation coupled with rectification
By using a membrane separation coupled with distillation, water and methanol are separated using heat exchange and membrane separation technologies, solving the problem of high energy consumption in the green methanol purification process and achieving efficient and low-energy methanol production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI HUANQIU ENG
- Filing Date
- 2024-12-05
- Publication Date
- 2026-06-05
AI Technical Summary
Existing green methanol purification processes are energy-intensive, especially the distillation stage, which requires a large amount of steam to displace water, leading to increased energy consumption.
The method of membrane separation coupled with distillation first recovers the heat of crude methanol through heat exchange, then uses membrane separation technology to separate water and methanol, and then uses the separated clear liquid and refined methanol product as heat exchange medium to further reduce the temperature, and finally obtains high-purity methanol through distillation.
It significantly reduces energy consumption in the green methanol purification stage, improves energy utilization, and produces high-purity methanol products.
Smart Images
Figure CN122145274A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of green methanol preparation technology, and in particular to a method and system for purifying crude methanol by membrane separation coupled with distillation. Background Technology
[0002] Currently, methanol production mainly relies on coal, natural gas, and coke oven gas as raw materials. Coal-based methanol production is the primary method in China, but this process emits large amounts of carbon dioxide—approximately 3 tons of carbon dioxide per ton of methanol produced. Furthermore, it generates significant amounts of sulfur and nitrogen oxides, necessitating tail gas treatment. Green methanol, as a clean energy source, not only reduces carbon dioxide emissions from traditional methanol production processes but can even utilize carbon dioxide as a raw material to generate methanol, offering a new pathway to global carbon neutrality. Most current green methanol production processes involve: gasifying biomass to obtain carbon dioxide as a feedstock, electrolyzing water to obtain green hydrogen, and then directly synthesizing green methanol using the carbon dioxide feedstock and green hydrogen.
[0003] Currently, methanol purification is mainly carried out through various distillation units, such as double-tower single-effect, triple-tower double-effect, and triple-tower triple-effect. These distillation units account for 20% to 30% of the total energy consumption required for methanol production. Therefore, optimizing this purification process requires consideration not only of the purification effect but also of the energy consumption during the purification stage. However, the synthesis reaction stage currently generates not only methanol but also a large amount of water, which accumulates during subsequent methanol purification stages. Due to the high miscibility of methanol and water, methanol is typically extracted from the bottom of the last distillation column during purification, leaving a large amount of water behind. This residual water requires steam displacement, which undoubtedly increases the steam demand on the distillation column's bottom, thus increasing the energy consumption during the purification stage. Summary of the Invention
[0004] This application provides a method and system for purifying crude methanol using membrane separation coupled with distillation, in order to solve the following technical problem: how to reduce energy consumption in the green methanol purification stage.
[0005] In a first aspect, this application provides a method for purifying crude methanol using membrane separation coupled with distillation, wherein the crude methanol contains water, and the method includes:
[0006] The crude methanol is subjected to heat exchange to recover the heat from the crude methanol, resulting in heat-exchanged crude methanol.
[0007] The heat-exchange crude methanol is subjected to membrane separation to obtain concentrated methanol and a separation supernatant, respectively.
[0008] The concentrated methanol is then subjected to distillation to obtain refined methanol product;
[0009] The heat exchange medium includes the separated clear liquid and / or the refined methanol product.
[0010] Optionally, the endpoint temperature of the heat exchange is 35℃~45℃.
[0011] Optionally, the step of heat-exchanging the crude methanol to obtain heat-exchanged crude methanol includes the following steps:
[0012] The crude methanol is subjected to a first heat exchange to obtain a first-heat-exchanged crude methanol; wherein the heat exchange medium of the first heat exchange includes the separated clear liquid and / or the refined methanol product;
[0013] The crude methanol obtained by the first heat exchange is subjected to a second heat exchange to obtain the heat-exchanged crude methanol.
[0014] Optionally, the endpoint temperature of the first heat exchange is 90℃~110℃, and the endpoint temperature of the second heat exchange is 35℃~40℃.
[0015] Optionally, when the heat exchange medium of the first heat exchange includes the separated clear liquid and the refined methanol product, the step of performing the first heat exchange on the crude methanol to obtain primary heat-exchanged crude methanol includes the following steps:
[0016] The crude methanol is subjected to a first heat exchange using the separated clear liquid and the refined methanol product to obtain crude methanol after one heat exchange, separated clear liquid after heat exchange, and refined methanol product after heat exchange, respectively.
[0017] Optionally, the temperature of the heat exchange separation liquid is 58℃~62℃, and the temperature of the heat exchange refined methanol product is 45℃~50℃.
[0018] Optionally, the heat exchange medium for the second heat exchange includes a circulating solvent.
[0019] Optionally, the distillation temperature is 35℃~110℃, and the distillation pressure is 20kPa~150kPa.
[0020] Secondly, this application provides a system for purifying crude methanol using membrane separation coupled with distillation, the system being adapted to the method described in the first aspect, wherein the feed end of the system is connected to a methane synthesis tower, and the system includes:
[0021] The heat exchange section includes a first heat exchanger, a second heat exchanger, and a circulating water feed pipe. The feed inlet of the first heat exchanger is connected to the outlet of the methane synthesis tower, and the outlet of the first heat exchanger is connected to the feed inlet of the second heat exchanger. The circulating water feed pipe is connected to the heat exchange medium inlet of the second heat exchanger.
[0022] The purification processing unit includes a membrane separation tower and a distillation tower. The outlet of the membrane separation tower is connected to the inlet of the distillation tower. The liquid outlet of the membrane separation tower is connected to the heat exchange medium inlet of the first heat exchanger. The product outlet of the distillation tower is connected to the heat exchange medium inlet of the first heat exchanger, so as to promote the recovery of heat from crude methanol by using the separated clear liquid and refined methanol product as heat exchange mediums.
[0023] Optionally, the heat exchange unit further includes a controller, a first regulating valve, a first temperature sensor, a second regulating valve, and a second temperature sensor. The first temperature sensor is located in the outlet of the first heat exchanger, the first regulating valve is located in the heat exchange medium inlet of the first heat exchanger, the second temperature sensor is located in the outlet of the second heat exchanger, and the second regulating valve is located between the circulating water inlet pipe and the second heat exchanger. The controller is connected to the first regulating valve, the first temperature sensor, the second regulating valve, and the second temperature sensor via electrical signals.
[0024] The technical solutions provided in this application have the following advantages compared with the prior art:
[0025] This application provides a method for purifying crude methanol using membrane separation coupled with distillation. Before distillation, the crude methanol undergoes membrane separation. Utilizing the selective permeability of the semi-permeable membrane, the aqueous solvent and methanol solute in the crude methanol are spontaneously separated, avoiding the need for water displacement during distillation and thus reducing energy consumption. Furthermore, the separated clarified liquid and purified methanol product are used as heat exchange media. Heat exchange occurs between these media and the crude methanol, allowing for the recovery of heat from the crude methanol and lowering its temperature to the required operating temperature for membrane separation. This reduces the number of cooling operations required in the membrane separation stage, thereby reducing energy consumption in the green methanol purification stage. Therefore, this method achieves low-energy purification of crude methanol through the coupling of heat exchange and membrane separation, thus reducing energy consumption in the green methanol purification stage. Attached Figure Description
[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.
[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0028] Figure 1 This is a schematic diagram of the main process of a membrane separation coupled with distillation to purify crude methanol, provided in an embodiment of this application.
[0029] Figure 2 This is a schematic flowchart of a method for purifying crude methanol using membrane separation coupled with distillation, as provided in an embodiment of this application.
[0030] Figure 3 A detailed flow diagram of a method for purifying crude methanol using membrane separation coupled with distillation, provided in this application embodiment;
[0031] Figure 4 A system logic diagram for purifying crude methanol using membrane separation coupled with distillation, provided in this application embodiment;
[0032] Figure 5 This is a schematic diagram of the actual structure of a membrane separation coupled with distillation to purify crude methanol, provided in an embodiment of this application.
[0033] Among them, 1-methane synthesis tower, 2-first heat exchanger, 3-second heat exchanger, 4-circulating water feed pipe, 5-membrane separation tower, 6-distillation tower, 7-controller, 8-first regulating valve, 9-first temperature sensor, 10-second regulating valve, 11-second temperature sensor. Detailed Implementation
[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0035] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values within that range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range; in addition, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.
[0036] In this document, terms such as “comprising” mean “including but not limited to”. Relational terms such as “first” and “second” are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. “And / or” describes the relationship between related objects, indicating that there can be three relationships, for example, A and / or B can mean: A alone, A and B simultaneously, or B alone; where A and B can be singular or plural. “At least one” means one or more, “more” means two or more; “at least one,” “at least one of the following,” or similar expressions refer to any combination of these items, including any combination of single or plural items; for example, “at least one of a, b, or c,” or “at least one of a, b, and c,” can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts representation" such as parts by weight or parts by mass indicates the proportional relationship between components. In the proportional relationships discussed in this article, the parameters that need to be described by proportion should be understood as the first term of the proportion in the order of description, and the proportion figures should be understood as the second term of the proportion. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportion figures in the proportion in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.
[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.
[0038] Figure 1 An exemplary schematic diagram of the main process of a membrane separation coupled with distillation purification method for crude methanol provided in an embodiment of this application is shown.
[0039] like Figure 1 As shown in the embodiments of this application, a method for purifying crude methanol using membrane separation coupled with distillation is provided. The crude methanol contains water. The method includes:
[0040] S1. The crude methanol is subjected to heat exchange to recover the heat of the crude methanol, thereby obtaining heat-exchanged crude methanol;
[0041] S2. The heat-exchange crude methanol is subjected to membrane separation to obtain concentrated methanol and separation supernatant, respectively;
[0042] S3. The concentrated methanol is distilled to obtain refined methanol product;
[0043] The heat exchange medium includes the separated clear liquid and / or the refined methanol product.
[0044] It should be noted that this crude methanol is generally obtained through methanol synthesis. The temperature of this crude methanol is typically 200℃~300℃, therefore it has a high calorific value and is difficult to separate directly using membrane separation without recovery. The pressure for this methanol synthesis can be 8.0MPa.
[0045] It should be noted that the selective permeable membrane of this membrane separation has a separation factor of more than 100 for water or methanol, which can separate concentrated methanol with low water content and enter the distillation stage to obtain methanol products with higher purity.
[0046] In some optional embodiments, the endpoint temperature of the heat exchange is 35°C to 45°C;
[0047] In these embodiments, the endpoint temperature of heat exchange can be 35°C to 45°C to ensure sufficient heat exchange, thereby reducing the crude methanol to the normal operating temperature range of membrane separation. In addition, sufficient heat exchange yields refined methanol product and separated clear liquid with a certain amount of heat, facilitating their subsequent use. Furthermore, this heat exchange temperature ensures that the temperature of the crude methanol being heated is within the normal operating temperature range of membrane separation, avoiding damage to the semi-permeable membrane of the membrane separation caused by excessively high temperatures.
[0048] It should be noted that the heat exchange process is continuous in actual production, so its duration is difficult to determine precisely. The residence time of the material in the air exchange stage can be controlled by the end temperature of the heat exchange to ensure complete heat exchange. In addition, the specific heat exchange time also needs to be considered comprehensively based on the actual feed rate, feed speed, and other factors.
[0049] The endpoint temperature for this heat exchange can be 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃, 44℃, or 45℃.
[0050] Figure 2 An exemplary schematic diagram of a method for purifying crude methanol using membrane separation coupled with distillation, provided in an embodiment of this application, is shown.
[0051] In some alternative implementations, such as Figure 2 As shown, the step of heat-exchanging the crude methanol to obtain heat-exchanged crude methanol includes the following steps:
[0052] S101. The crude methanol is subjected to a first heat exchange to obtain crude methanol with a single heat exchange; wherein the heat exchange medium of the first heat exchange includes the separated clear liquid and / or the refined methanol product;
[0053] S102. The crude methanol obtained by the first heat exchange is subjected to a second heat exchange to obtain heat-exchanged crude methanol;
[0054] In these embodiments, the heat exchange is divided into a first heat exchange and a second heat exchange. The heat exchange medium for the first heat exchange may include the separated clear liquid and / or refined methanol product. By separating the clear liquid and refined methanol product, the heat of crude methanol can be effectively recovered, which not only facilitates the normal operation of subsequent membrane separation, but also facilitates the use of the separated clear liquid and refined methanol product. In addition, the introduction of the second heat exchange can further enhance the temperature control of the heat exchange stage, so as to further reduce the energy consumption of the green methanol purification stage.
[0055] In some alternative implementations, the endpoint temperature of the first heat exchange is 90°C to 110°C, and the endpoint temperature of the second heat exchange is 35°C to 40°C.
[0056] In these embodiments, the endpoint temperature of the first heat exchange can be 90°C to 110°C, and the endpoint temperature of the second heat exchange can be 35°C to 40°C, so that the first and second heat exchanges are carried out sufficiently, so that the crude methanol is reduced to the normal operating temperature range of membrane separation. In addition, the refined methanol product or the separated clear liquid after sufficient heat exchange can be used directly, thereby avoiding subsequent heating operations and reducing the energy consumption of the overall method.
[0057] The endpoint temperature of the first heat exchange can be 90℃, 95℃, 100℃, 105℃ or 110℃.
[0058] The endpoint temperature of the second heat exchange can be 35℃, 36℃, 37℃, 38℃, 39℃ or 40℃.
[0059] Figure 3 A detailed flowchart illustrating a method for purifying crude methanol using membrane separation coupled with distillation, as provided in an embodiment of this application, is shown as an example.
[0060] In some alternative implementations, such as Figure 3 As shown, when the heat exchange medium of the first heat exchange includes the separated clear liquid and the refined methanol product, the step of performing the first heat exchange on the crude methanol to obtain crude methanol after one heat exchange includes the following steps:
[0061] S111. The crude methanol is subjected to a first heat exchange using the separated clear liquid and the refined methanol product to obtain crude methanol after one heat exchange, separated clear liquid after heat exchange, and refined methanol product after heat exchange, respectively.
[0062] In these embodiments, using the separated clear liquid and refined methanol product as heat exchange mediums for the first heat exchange allows the heat from the crude methanol to be distributed to the separated clear liquid and refined methanol product, facilitating their direct use and saving subsequent heating operations on the separated clear liquid and refined methanol product, thereby reducing the overall energy consumption of the method.
[0063] It should be noted that the separated clear liquid, after heat exchange, can be used as industrial water or as a heat exchange medium for other equipment, or it can be directly discharged as waste liquid.
[0064] In some optional embodiments, the temperature of the heat exchange separation clarified liquid is 58°C to 62°C, and the temperature of the heat exchange refined methanol product is 45°C to 50°C.
[0065] In these embodiments, the temperature of the heat exchange separation liquid can be 58°C to 62°C, and the temperature of the heat exchange refined methanol product can be 45°C to 50°C. This indicates that after the first heat exchange, the heat of the crude methanol is fully distributed to the heat exchange separation liquid and the heat exchange refined methanol product.
[0066] The temperature of the heat exchange separation solution can be 58℃, 59℃, 60℃, 61℃ or 62℃.
[0067] The temperature for heat exchange to refine methanol products can be 45℃, 46℃, 47℃, 48℃, 49℃ or 50℃.
[0068] In some alternative embodiments, the heat exchange medium of the second heat exchange includes a circulating solvent;
[0069] In these embodiments, the heat exchange medium for the second heat exchange can be a circulating solvent. By using the circulating solvent as the heat exchange medium for the second heat exchange, the crude methanol can be further heated to reach the range of 35°C to 45°C after heat exchange, so as to effectively recover the heat of the crude methanol and reduce the energy consumption of the green methanol purification stage.
[0070] It should be noted that the circulating solvent can be water; after heat exchange, the circulating solvent can be used as a raw material for the preparation of hydrogen required for methanol synthesis, and electrolysis can be used to convert the circulating solvent into hydrogen raw material.
[0071] In some optional embodiments, the distillation temperature is 35°C to 110°C, and the distillation pressure is 20 kPa to 150 kPa;
[0072] In these embodiments, the distillation temperature can be 35°C to 110°C, and the distillation pressure can be 20 kPa to 150 kPa, to promote thorough distillation so that the methanol in the concentrated methanol is separated from other organic impurities, thereby obtaining a pure refined methanol product.
[0073] The distillation temperature can be 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, or 110℃.
[0074] The pressure for this distillation can be 20 kPa, 30 kPa, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa, 100 kPa, 110 kPa, 120 kPa, 130 kPa, 140 kPa, or 150 kPa.
[0075] It should be noted that the distillation time depends on the feed rate of the heat exchange crude methanol. The distillation can be carried out by setting up a circulation pipeline to promote the full distillation of the heat exchange crude methanol.
[0076] Figure 4 An exemplary system logic diagram of a membrane separation coupled with distillation purification of crude methanol provided in an embodiment of this application is shown.
[0077] Figure 5 An exemplary schematic diagram of the actual structure of a membrane separation coupled with distillation purification system for crude methanol provided in an embodiment of this application is shown.
[0078] Based on a general inventive concept, such as Figure 4 and Figure 5 As shown in the embodiment of this application, a system for purifying crude methanol using membrane separation coupled with distillation is provided. The system is adapted to the method described above, and its feed end is connected to a methane synthesis tower 1. The system includes:
[0079] The heat exchange section includes a first heat exchanger 2, a second heat exchanger 3, and a circulating water feed pipe 4. The feed port of the first heat exchanger 2 is connected to the discharge port of the methane synthesis tower 1, and the discharge port of the first heat exchanger 2 is connected to the feed port of the second heat exchanger 3. The circulating water feed pipe 4 is connected to the heat exchange medium inlet of the second heat exchanger 3.
[0080] The purification treatment unit includes a membrane separation tower 5 and a distillation tower 6. The outlet of the membrane separation tower 5 is connected to the inlet of the distillation tower 6. The liquid outlet of the membrane separation tower 5 is connected to the heat exchange medium inlet of the first heat exchanger 2. The product outlet of the distillation tower 6 is connected to the heat exchange medium inlet of the first heat exchanger 2, so as to promote the recovery of heat from crude methanol by using the separated clear liquid and refined methanol product as heat exchange mediums.
[0081] It should be noted that the first heat exchanger 2 is also equipped with a non-condensable gas outlet to return the non-condensable gas components (mainly hydrogen, carbon dioxide, methanol, etc.) in the first heat exchanger 2 to the methane synthesis tower 1 for further processing.
[0082] The system is implemented based on the above method. The specific steps of the method can be referred to the above embodiments. Since the system adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.
[0083] In some optional embodiments, the heat exchange unit further includes a controller 7, a first regulating valve 8, a first temperature sensor 9, a second regulating valve 10, and a second temperature sensor 11. The first temperature sensor 9 is located in the outlet of the first heat exchanger 2, the first regulating valve 8 is located in the heat exchange medium inlet of the first heat exchanger 2, the second temperature sensor 11 is located in the outlet of the second heat exchanger 3, and the second regulating valve 10 is located between the circulating water inlet pipe 4 and the second heat exchanger 3. The controller 7 is connected to the first regulating valve 8, the first temperature sensor 9, the second regulating valve 10, and the second temperature sensor 11 via electrical signals.
[0084] In these embodiments, the heat exchange unit may further include a controller 7, a first regulating valve 8, a first temperature sensor 9, a second regulating valve 10, and a second temperature sensor 11. The first temperature sensor 9 detects the temperature of the crude methanol flowing out of the first heat exchanger 2, which determines whether the first heat exchange is complete. If it is not complete, the controller 7 controls the first regulating valve 8 to control the feed flow rate of the separated clear liquid and refined methanol product, so that the temperature measured by the first temperature sensor 9 reaches the preset standard (40℃~45℃). Based on the same principle, the second temperature sensor 11 detects the temperature of the crude methanol flowing out of the second heat exchanger 3, which determines whether the second heat exchange is complete. If it is not complete, the controller 7 controls the second regulating valve 10 to control the feed flow rate of the circulating solvent, so that the temperature measured by the second temperature sensor 11 reaches the preset standard (35℃~40℃).
[0085] In summary, the method for purifying crude methanol using membrane separation coupled with distillation provided in this application not only effectively separates water from crude methanol and produces a high-purity methanol product, but also significantly reduces energy consumption throughout the entire production process. Specifically:
[0086] (1) Heat exchange can reduce the heat of crude methanol and reduce the cooling requirements of the membrane separation process.
[0087] (2) The low energy consumption of membrane separation technology means that most of the water is removed before entering the distillation column, which reduces the load on the distillation column for purifying crude methanol.
[0088] (3) The optimization of the membrane separation coupled distillation process further improved the separation efficiency and reduced the consumption of heating steam.
[0089] In summary, this method achieves efficient refining of crude methanol while significantly reducing energy consumption during the production process through multi-stage energy-saving measures.
[0090] Another embodiment of this application provides a system for purifying crude methanol using membrane separation coupled with distillation. This system consists of the following components: a first heat exchanger 2 for initially reducing the temperature of the crude methanol; the inlet of the first heat exchanger 2 is connected to the outlet of the methane synthesis tower 1 to receive crude methanol from the methane synthesis tower 1; the outlet of the first heat exchanger 2 is connected to the inlet of the second heat exchanger 3 to send the cooled crude methanol into the second heat exchanger 3; the heat exchange medium inlet of the first heat exchanger 2 is connected to the liquid outlet of the membrane separation tower 5 and the product outlet of the distillation tower 6 to receive the separated clear liquid and refined methanol product as the heat exchange medium. Second heat exchanger 3: further reduces the temperature of crude methanol; The inlet of second heat exchanger 3: connected to the outlet of first heat exchanger 2, receiving the cooled crude methanol; The outlet of second heat exchanger 3: connected to the inlet of membrane separator 5, sending the further cooled crude methanol into membrane separator 5; The heat exchange medium inlet of second heat exchanger 3: connected to circulating water inlet pipe 4, receiving circulating water as the heat exchange medium. Circulating water inlet pipe 4: provides circulating water to second heat exchanger 3, helping to further reduce the temperature of crude methanol. The purification treatment unit includes:
[0091] Membrane separator 5: used for preliminary separation of methanol and water; the inlet of membrane separator 5 is connected to the outlet of the second heat exchanger 3 to receive crude methanol that has been further cooled; the outlet of membrane separator 5 is connected to the inlet of distillation column 6 to feed concentrated methanol into distillation column 6; the outlet of membrane separator 5 is connected to the heat exchange medium inlet of the first heat exchanger 2 to return the separated clarified liquid to the first heat exchanger 2 as a heat exchange medium; the purification treatment unit also includes: distillation column 6: used for final purification of methanol. The inlet of distillation column 6 is connected to the outlet of membrane separator 5 to receive concentrated methanol; the product outlet of distillation column 6 is connected to the heat exchange medium inlet of the first heat exchanger 2 to return the purified methanol product to the first heat exchanger 2 as a heat exchange medium; the outlet of distillation column 6 outputs the final purified methanol product.
[0092] The system's workflow includes: preliminary cooling of crude methanol (S1): Process: Crude methanol from methane synthesis tower 1 passes through the first heat exchanger 2, where it exchanges heat with the separated clear liquid and refined methanol product, thus initially cooling the crude methanol; Effect: The temperature of the cooled crude methanol increases, reducing the energy required for subsequent heating and saving energy.
[0093] Further cooling of crude methanol (S2): Process: After cooling, the crude methanol exchanges heat with circulating water through the second heat exchanger 3, further increasing the temperature of the crude methanol; Effect: The crude methanol with a higher temperature after further cooling reduces the heating requirements in the membrane separation and distillation process, further saving energy.
[0094] Membrane separation (S3): Process: Further cooled crude methanol enters membrane separation column 5. Through the selective permeability of the semi-permeable membrane, methanol and water are separated into two streams: concentrated methanol and a clear liquid. Effect: Membrane separation can efficiently remove most of the water, reducing the load on distillation column 6 and decreasing energy consumption during the distillation process.
[0095] Distillation (S4): Process: The concentrated methanol obtained from membrane separation enters distillation column 6, where it is further separated from water to obtain refined methanol product. Effect: By optimizing the distillation process, the consumption of heating steam can be reduced while maintaining separation efficiency, thus further saving energy.
[0096] Heat exchange medium recovery (S5): Process: The separated liquid from membrane separation tower 5 and the refined methanol product from distillation tower 6 are respectively sent back to the first heat exchanger 2 as heat exchange medium to recover the heat from the crude methanol. Effect: By recovering the heat exchange medium, energy is further saved and the overall energy efficiency of the system is improved.
[0097] Therefore, the designed system and its workflow not only effectively separate water from crude methanol to produce high-purity methanol, but also significantly reduce energy consumption throughout the production process. Specifically: the cooling process of the heat exchanger reduces the temperature control requirements in the membrane separation and distillation processes. The low-energy consumption characteristic of membrane separation technology ensures that most of the water is removed before entering distillation column 6, reducing the load on distillation column 6. Optimization of the distillation process further improves separation efficiency and reduces heating steam consumption. The recovery of the heat exchange medium further saves energy and improves the overall energy efficiency of the system.
[0098] In summary, this system achieves efficient refining of crude methanol through multi-stage energy-saving measures, while significantly reducing energy consumption during the production process.
[0099] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.
[0100] Example 1
[0101] like Figure 3As shown, a method for purifying crude methanol using membrane separation coupled with distillation, wherein the crude methanol contains water, includes:
[0102] S111. The crude methanol is subjected to a first heat exchange using the separated clear liquid and the refined methanol product to obtain crude methanol after one heat exchange, separated clear liquid after heat exchange, and refined methanol product after heat exchange, respectively.
[0103] S102. The crude methanol produced by the first heat exchange is subjected to a second heat exchange to obtain heat-exchanged crude methanol;
[0104] S2. The heat-exchanged crude methanol is subjected to membrane separation to obtain concentrated methanol and clear liquid;
[0105] S3. Distill the concentrated methanol to obtain refined methanol product;
[0106] The heat exchange medium includes the separated clear liquid and the refined methanol product.
[0107] The endpoint temperature of the heat exchange is 40℃.
[0108] The endpoint temperature of the first heat exchange is 45℃, and the endpoint temperature of the second heat exchange is 40℃.
[0109] The temperature for heat exchange separation of the clear liquid is 60℃, and the temperature for heat exchange purification of methanol product is 50℃.
[0110] The heat exchange medium for the second heat exchange includes a circulating solvent.
[0111] The distillation temperature is 70℃ and the distillation pressure is 80kPa.
[0112] Example 2
[0113] Based on the content disclosed in Example 1, the following modifications are made:
[0114] The endpoint temperature of the heat exchange is 35℃.
[0115] The endpoint temperature of the first heat exchange is 40℃, and the endpoint temperature of the second heat exchange is 35℃.
[0116] The temperature of the heat exchange separation of the clear liquid is 58℃, and the temperature of the heat exchange purification of the methanol product is 45℃.
[0117] The heat exchange medium for the second heat exchange includes a circulating solvent.
[0118] The distillation temperature is 35℃ and the distillation pressure is 20kPa.
[0119] Example 3
[0120] Based on the content disclosed in Example 1, the following modifications are made:
[0121] The endpoint temperature of the heat exchange is 45℃.
[0122] The endpoint temperature of the first heat exchange is 45℃, and the endpoint temperature of the second heat exchange is 40℃.
[0123] The temperature for heat exchange separation of the clear liquid is 62℃, and the temperature for heat exchange purification of methanol product is 50℃.
[0124] The heat exchange medium for the second heat exchange includes a circulating solvent.
[0125] The distillation temperature is 110℃ and the distillation pressure is 150kPa.
[0126] Example 4
[0127] Based on the method disclosed in Example 1, a further related system is designed, as follows:
[0128] like Figure 4 As shown, a system for purifying crude methanol using membrane separation coupled with distillation is described.
[0129] The feed end of the system is connected to methane synthesis tower 1, including:
[0130] The heat exchange section includes a first heat exchanger 2, a second heat exchanger 3, and a circulating water feed pipe 4. The feed port of the first heat exchanger 2 is connected to the discharge port of the methane synthesis tower 1, and the discharge port of the first heat exchanger 2 is connected to the feed port of the second heat exchanger 3. The circulating water feed pipe 4 is connected to the heat exchange medium inlet of the second heat exchanger 3.
[0131] The purification treatment unit includes a membrane separation tower 5 and a distillation tower 6. The outlet of the membrane separation tower 5 is connected to the inlet of the distillation tower 6. The liquid outlet of the membrane separation tower 5 is connected to the heat exchange medium inlet of the first heat exchanger 2. The product outlet of the distillation tower 6 is connected to the heat exchange medium inlet of the first heat exchanger, so as to promote the separation of the clear liquid and the refined methanol product as heat exchange mediums to recover the heat of the crude methanol.
[0132] The heat exchange section also includes a controller 7, a first regulating valve 8, a first temperature sensor 9, a second regulating valve 10, and a second temperature sensor 11. The first temperature sensor 9 is located in the outlet of the first heat exchanger 2, the first regulating valve 8 is located in the heat exchange medium inlet of the first heat exchanger 2, the second temperature sensor 11 is located in the inlet of the second heat exchanger 3, and the second regulating valve 10 is located between the circulating water inlet pipe 4 and the second heat exchanger 3. The controller 7 is connected to the first regulating valve 8, the first temperature sensor 9, the second regulating valve 10, and the second temperature sensor 11 via electrical signals.
[0133] Comparative Example 1
[0134] Based on the content disclosed in Example 1, the following modifications are made:
[0135] Instead of using the first heat exchanger, the second heat exchanger, and membrane separation, the traditional crude methanol distillation process is used directly.
[0136] Comparative Example 2
[0137] Based on the content disclosed in Example 1, the following modifications are made:
[0138] The first and second heat exchangers are not used.
[0139] Comparative Example 3
[0140] Based on the content disclosed in Example 1, the following modifications are made:
[0141] Membrane separation is not used.
[0142] Comparative Example 4
[0143] Based on the content disclosed in Example 1, the following modifications are made:
[0144] The endpoint temperature of the first heat exchange is 35℃, and the endpoint temperature of the second heat exchange is 30℃.
[0145] Comparative Example 5
[0146] Based on the content disclosed in Example 1, the following modifications are made:
[0147] The endpoint temperature of the first heat exchange is 55℃, and the endpoint temperature of the second heat exchange is 50℃.
[0148] Relevant experimental and effect data:
[0149] The fuel consumption of the entire method in Comparative Example 1 was 100%. Under the condition that the material ratio and other operating conditions were the same, the fuel consumption of each embodiment and the comparative example was statistically analyzed. The statistically analyzed fuel consumption was compared with that of Comparative Example 1. The fuel consumption rate was calculated with the fuel consumption of Comparative Example 1 as the denominator and the fuel consumption of each method as the numerator. The energy utilization rate was calculated using the following formula: Energy utilization rate = 1 - Fuel consumption rate. The results are shown in Table 1.
[0150] Table 1 shows the energy efficiency achieved by the methods in each embodiment and comparative example.
[0151]
[0152] As shown in Table 1, the embodiment of this application provides a method for purifying crude methanol by membrane separation coupled with distillation. This method achieves low-energy purification of crude methanol through the coupling process of heat exchange and membrane separation, thereby reducing the energy consumption of the green methanol purification stage and increasing the energy utilization rate of the green methanol purification stage to more than 40%.
[0153] Furthermore, although Comparative Example 3 only omits the membrane separation process, it also lacks the separated supernatant as a heat exchange medium, which significantly impacts the heat exchange process. In Comparative Example 4, both the first and second heat exchange temperatures are relatively low, preventing the membrane separation from functioning properly. This reduces the purity of the concentrated methanol and the amount of separated supernatant. The small amount of separated supernatant is insufficient as a heat exchange medium, resulting in low energy utilization in Comparative Example 4. While Comparative Example 5 utilizes higher first and second heat exchange temperatures, its membrane separation process performs poorly at these higher temperatures, resulting in a final methanol product purity of <80%, compared to >95% for the products in Examples 1-3.
[0154] In summary, the embodiments of this application provide a method for purifying crude methanol using membrane separation coupled with distillation. This method, through the coupling of heat exchange and membrane separation processes, can implement multi-stage energy-saving measures during the methanol purification stage, thereby achieving efficient purification of crude methanol while significantly reducing energy consumption in the production process.
[0155] In addition, the membrane separation coupled distillation purification method for crude methanol provided in this application embodiment can effectively reduce the input of external energy and reduce energy consumption by more than 40% compared with the traditional methanol distillation process, thereby achieving efficient methanol distillation.
[0156] Furthermore, the embodiments of this application provide a system for purifying crude methanol using membrane separation coupled with distillation. This system only requires the addition of a first heat exchanger, a second heat exchanger, and a membrane separation tower. It only requires the construction of multiple heaters and membrane separation towers in the original distillation system, and the relevant system can be modified at a lower cost to save production costs.
[0157] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.
Claims
1. A method for purifying crude methanol using membrane separation coupled with distillation, wherein the crude methanol contains water, the method comprising: The crude methanol is subjected to heat exchange to recover the heat from the crude methanol, resulting in heat-exchanged crude methanol. The heat-exchange crude methanol is subjected to membrane separation to obtain concentrated methanol and a separation supernatant, respectively. The concentrated methanol is then subjected to distillation to obtain refined methanol product; The heat exchange medium includes the separated clear liquid and / or the refined methanol product.
2. The method according to claim 1, wherein the endpoint temperature of the heat exchange is 35℃~45℃.
3. The method according to claim 1, wherein the step of heat-exchanging the crude methanol to obtain heat-exchanged crude methanol comprises the following steps: The crude methanol is subjected to a first heat exchange to obtain primary heat-exchanged crude methanol; wherein... The heat exchange medium for the first heat exchange includes the separated clear liquid and / or the refined methanol product; The crude methanol obtained by the first heat exchange is subjected to a second heat exchange to obtain the heat-exchanged crude methanol.
4. The method according to claim 3, wherein the endpoint temperature of the first heat exchange is 90℃~110℃, and the endpoint temperature of the second heat exchange is 35℃~40℃.
5. The method according to claim 3, wherein when the heat exchange medium of the first heat exchange includes the separated clear liquid and the refined methanol product, the step of performing a first heat exchange on the crude methanol to obtain a single-heat-exchanged crude methanol includes the following steps: The crude methanol is subjected to a first heat exchange using the separated clear liquid and the refined methanol product to obtain crude methanol after one heat exchange, separated clear liquid after heat exchange, and refined methanol product after heat exchange, respectively.
6. According to claim 5, the temperature of the heat exchange separation liquid is 58℃~62℃, and the temperature of the heat exchange refined methanol product is 45℃~50℃.
7. The method according to claim 3, wherein the heat exchange medium of the second heat exchange includes a circulating solvent.
8. The method according to claim 1, wherein the distillation temperature is 35℃~110℃ and the distillation pressure is 20kPa~150kPa.
9. A system for purifying crude methanol using membrane separation coupled with distillation, the system being adapted to the method of any one of claims 1 to 8, wherein the feed end of the system is connected to a methane synthesis tower (1), and the system comprises: The heat exchange section includes a first heat exchanger (2), a second heat exchanger (3), and a circulating water feed pipe (4). The feed inlet of the first heat exchanger (2) is connected to the outlet of the methane synthesis tower (1), and the outlet of the first heat exchanger (2) is connected to the feed inlet of the second heat exchanger (3). The circulating water feed pipe (4) is connected to the heat exchange medium inlet of the second heat exchanger (3). The purification processing unit includes a membrane separation tower (5) and a distillation tower (6). The outlet of the membrane separation tower (5) is connected to the inlet of the distillation tower (6). The liquid outlet of the membrane separation tower (5) is connected to the heat exchange medium inlet of the first heat exchanger (2). The product outlet of the distillation tower (6) is connected to the heat exchange medium inlet of the first heat exchanger, so as to promote the separation of the clear liquid and the refined methanol product as heat exchange medium to recover the heat of the crude methanol.
10. The system according to claim 9, wherein the heat exchange unit further comprises a controller (7), a first regulating valve (8), a first temperature sensor (9), a second regulating valve (10), and a second temperature sensor (11), wherein the first temperature sensor (9) is disposed in the outlet of the first heat exchanger (2), the first regulating valve (8) is disposed in the heat exchange medium inlet of the first heat exchanger (2), the second temperature sensor (11) is disposed in the outlet of the second heat exchanger (3), the second regulating valve (10) is disposed between the circulating water inlet pipe (4) and the second heat exchanger (3), and the controller (7) is connected to the first regulating valve (8), the first temperature sensor (9), the second regulating valve (10), and the second temperature sensor (11) respectively by electrical signals.