System for separating and recovering methyl acetate and methanol by using polytetrahydrofuran device

Abstract

The utility model provides a system for separating and recovering methyl acetate and methanol by a polytetrahydrofuran device, and relates to the technical field of chemical production equipment. By arranging a methyl acetate-methanol separation unit, waste liquid containing methyl acetate, methanol and a small amount of tetrahydrofuran generated by a polytetrahydrofuran reaction unit passes through a high-pressure rectifying tower and a low-pressure rectifying tower, and a large amount of methyl acetate-methanol azeotrope of the low-pressure rectifying tower is circulated back to the high-pressure rectifying tower; a high-purity methyl acetate product is collected from a high-pressure rectifying tower kettle, crude methanol is collected from a low-pressure rectifying tower kettle, the crude methanol enters a methanol rectifying tower to be separated, and a high-purity methanol product is obtained from the tower kettle. According to the system, high-purity methyl acetate and methanol monomer materials are separated through pressure swing distillation, the separated methyl acetate and methanol can be reused, the system has the advantages that the separation system is simple, the separated product is high in purity and the like, and the raw material cost is greatly reduced, so that the production cost is reduced, and the production economic benefits are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of chemical production equipment, in particular to a system for separating and recovering methyl acetate and methanol using a polytetrahydrofuran device. Background Art

[0002] Polytetrahydrofuran (PTMEG) is an important polymer material, which is polymerized from tetrahydrofuran monomers. The molecule has a linear structure and no side chains. It has high flexibility, high elasticity, chemical resistance and easy processing. Polytetrahydrofuran with an average molecular weight of 1000 can be used to produce segmented polyurethane rubber, which is used in tires, transmission belts, gaskets, coatings, films and other fields; Polytetrahydrofuran with an average molecular weight of 2000 can be used to produce polyurethane elastic fibers with good anti-coagulation properties, which can be used as medical polymer materials.

[0003] At present, the preparation methods of polytetrahydrofuran mainly include fluorosulfonic acid method, acid anhydride method, heteropolyacid method and clay method. Among them, the acid anhydride method has the advantages of low operation difficulty, high reliability and continuous use of catalyst, so it has a wide range of applications. The preparation of polytetrahydrofuran by the acid anhydride method is to use tetrahydrofuran, methanol, acetic anhydride, acetic acid and a small amount of hydrogen as raw materials, and to prepare polytetrahydrofuran products with an average molecular weight of 1000 to 2000 through polymerization process, alcoholysis process and ion exchange process. During the entire synthesis process, waste liquid containing by-product methyl acetate, raw material methanol and a small amount of tetrahydrofuran will also be produced. In the waste liquid, methyl acetate and methanol easily form azeotropes and are difficult to separate by conventional distillation. At present, the waste liquid is usually incinerated, resulting in the loss of methyl acetate and methanol.

[0004] In view of this, the present utility model is proposed. Utility Model Content

[0005] The utility model aims to provide a system for separating and recovering methyl acetate and methanol in a polytetrahydrofuran device, which can recover methyl acetate and raw material reactant methanol produced in the process of preparing polytetrahydrofuran by anhydride method, thereby realizing the recovery and utilization of methyl acetate and methanol.

[0006] The embodiment of the utility model is achieved as follows:

[0007] In a first aspect, the utility model provides a system for separating and recovering methyl acetate and methanol in a polytetrahydrofuran device, comprising a polytetrahydrofuran reaction unit and a methyl acetate-methanol separation unit.

[0008] The methyl acetate-methanol separation unit comprises a high-pressure distillation tower, a low-pressure distillation tower and a methanol distillation tower.

[0009] The high-pressure distillation tower includes a high-pressure tower raw material inlet, an azeotrope circulation feed inlet, a high-pressure tower kettle outlet and a high-pressure tower top outlet. The high-pressure tower raw material inlet is connected to the polytetrahydrofuran reaction unit through a pipeline, and the high-pressure tower kettle outlet is configured to discharge methyl acetate.

[0010] The low-pressure distillation tower includes a low-pressure tower raw material inlet, a low-pressure tower kettle outlet and a low-pressure tower top outlet. The high-pressure tower top outlet is connected to the low-pressure tower raw material inlet through a pipeline, and the azeotropic circulation feed port is connected to the low-pressure tower top outlet through a pipeline.

[0011] The methanol distillation tower includes a methanol distillation tower raw material inlet, a methanol tower bottom outlet and a methanol tower top outlet. The low-pressure tower bottom outlet is connected to the methanol distillation tower raw material inlet through a pipeline, the methanol tower bottom outlet is connected to the methanol production pipeline, and the methanol tower top outlet is configured to remove impurities.

[0012] Optionally, an azeotropic distillation tower is also connected between the raw material inlet of the high-pressure tower and the polytetrahydrofuran reaction unit, and the azeotropic distillation tower includes an azeotropic raw material inlet, an azeotropic tower bottom outlet and an azeotropic tower top outlet. The azeotropic raw material inlet is connected to the polytetrahydrofuran reaction unit through a pipeline, and the azeotropic tower bottom outlet is configured to discharge methanol.

[0013] An azeotropic distillation tower condenser is installed on the pipeline connecting the azeotropic tower top outlet with the high-pressure tower raw material inlet, and a first branch pipeline is connected to the pipeline connecting the azeotropic distillation tower condenser with the high-pressure tower raw material inlet, and the other end of the first branch pipeline is connected to one end of the azeotropic distillation tower near the top of the tower.

[0014] Optionally, it also includes an azeotropic distillation tower reboiler, the inlet and outlet of the azeotropic distillation tower reboiler are respectively connected to the pipeline, the pipeline connected to the inlet of the azeotropic distillation tower reboiler is connected to the outlet of the azeotropic tower kettle, the pipeline connected to the outlet of the azeotropic distillation tower reboiler is connected to one end of the azeotropic distillation tower close to the kettle, and the pipeline connected to the inlet of the azeotropic distillation tower reboiler is also connected to the first methanol collection pipe.

[0015] Optionally, a high-pressure distillation tower condenser is installed on the pipeline connecting the high-pressure tower top outlet with the low-pressure tower raw material inlet, and a second branch pipeline is connected to the pipeline connecting the high-pressure distillation tower condenser with the low-pressure tower raw material inlet, and the other end of the second branch pipeline is connected to one end of the high-pressure distillation tower close to the top of the tower.

[0016] Optionally, a low-pressure distillation tower condenser is installed on the pipeline connecting the azeotrope circulation feed port and the low-pressure tower top outlet, and the low-pressure distillation tower condenser is also connected to an end of the low-pressure distillation tower close to the tower top through a third branch pipeline.

[0017] Optionally, the methanol tower top outlet is connected to an end of the methanol distillation tower near the top of the tower through a fourth branch pipeline, and a methanol distillation tower condenser is installed on the fourth branch pipeline, and the fourth branch pipeline is also connected to an impurity discharge pipeline.

[0018] Optionally, it also includes a high-pressure distillation tower reboiler, the inlet and outlet of the high-pressure distillation tower reboiler are respectively connected to the pipeline, the pipeline connected to the inlet of the high-pressure distillation tower reboiler is connected to the outlet of the high-pressure tower kettle, the pipeline connected to the outlet of the high-pressure distillation tower reboiler is connected to one end of the high-pressure distillation tower close to the kettle, and the pipeline connected to the outlet of the high-pressure tower kettle is also connected to a methyl acetate collecting pipe.

[0019] Optionally, it also includes a low-pressure distillation tower reboiler, and a low-pressure distillation reflux port is provided at one end of the low-pressure distillation tower close to the tower bottom, the low-pressure distillation reflux port is connected to the pipeline connecting the low-pressure tower bottom outlet and the methanol distillation tower raw material inlet through the fifth branch pipeline, and the low-pressure distillation tower reboiler is installed on the fifth branch pipeline.

[0020] Optionally, it also includes a methanol distillation tower reboiler, the inlet and outlet of the methanol distillation tower reboiler are respectively connected to the pipeline, the pipeline connected to the inlet of the methanol distillation tower reboiler is connected to the outlet of the methanol tower kettle, the pipeline connected to the outlet of the methanol distillation tower reboiler is connected to one end of the methanol distillation tower close to the kettle, and the pipeline connected to the outlet of the methanol tower kettle is also connected to a second methanol collecting pipe.

[0021] The beneficial effects of the embodiments of the utility model are:

[0022] The utility model provides a system for separating and recovering methyl acetate and methanol from a polytetrahydrofuran device. By setting a methyl acetate-methanol separation unit, the waste liquid containing methyl acetate, methanol and a small amount of tetrahydrofuran generated by the polytetrahydrofuran reaction unit passes through a high-pressure distillation tower and a low-pressure distillation tower, and the methyl acetate-methanol azeotrope of the low-pressure distillation tower is recycled back to the high-pressure distillation tower in large quantities, so that the purity of the methyl acetate product collected from the bottom of the high-pressure distillation tower can be ≥99.5wt%. The crude methanol is collected from the bottom of the low-pressure distillation tower, and the crude methanol is separated in a methanol distillation tower, and the purity of the methanol product obtained in the bottom of the tower is ≥99.5wt%. The above system provided by the utility model can realize the recovery and separation of methyl acetate and methanol, has the advantages of a simple separation system, high purity of the separated product, etc., greatly reduces the cost of raw materials, thereby reducing the production cost and improving the economic benefits of production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the utility model and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1A schematic diagram of the structure of a system for separating and recovering methyl acetate and methanol using a polytetrahydrofuran device provided in an embodiment of the utility model;

[0025] Figure 2 This is a schematic structural diagram of a methyl acetate-methanol separation unit provided in an embodiment of the utility model.

[0026] Icons: 100-system for separating and recovering methyl acetate and methanol in a polytetrahydrofuran device; 110-polytetrahydrofuran reaction unit; 120-methyl acetate-methanol separation unit; 121-azeotropic distillation tower; 1211-azeotropic raw material inlet; 1212-azeotropic tower bottom outlet; 1213-azeotropic tower top outlet; 122-high-pressure distillation tower; 1221-high-pressure tower raw material inlet; 1222-azeotropic product circulation feed port; 12 23-high-pressure tower kettle outlet; 1224-high-pressure tower top outlet; 123-low-pressure distillation tower; 1231-low-pressure tower raw material inlet; 1232-low-pressure tower kettle outlet; 1233-low-pressure tower top outlet; 124-methanol distillation tower; 1241-methanol distillation tower raw material inlet; 1242-methanol tower kettle outlet; 1243-methanol tower top outlet; 125-azeotropic distillation tower condenser; 126-high-pressure distillation tower condenser; 127-low-pressure distillation tower condenser; 128-methanol distillation tower condenser; 129-azeotropic distillation tower reboiler; 130-high-pressure distillation tower reboiler; 131-low-pressure distillation tower reboiler; 132-methanol distillation tower reboiler. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Generally, the components of the embodiments of the utility model described and shown in the drawings here can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention to be protected, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0030] In the description of the present utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the accompanying drawings, or the orientation or position relationship in which the utility model product is usually placed when in use, which is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0031] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0032] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] Please refer to Figure 1 This embodiment provides a system 100 for separating and recovering methyl acetate and methanol in a polytetrahydrofuran device, comprising a polytetrahydrofuran reaction unit 110 and a methyl acetate-methanol separation unit 120 .

[0034] Among them, the system 100 for separating and recovering methyl acetate and methanol in a polytetrahydrofuran device provided in this embodiment is applicable to the process of preparing polytetrahydrofuran by anhydride method, because the polytetrahydrofuran prepared by anhydride method is prepared from tetrahydrofuran, methanol, acetic anhydride, acetic acid and a small amount of hydrogen as raw materials, and a polytetrahydrofuran product with an average molecular weight of 1000 to 2000 is prepared through polymerization process, alcoholysis process and ion exchange process. In the whole synthesis process, methyl acetate is also produced as a by-product, but the by-product methyl acetate is difficult to separate from the unreacted raw material methanol, and is generally directly treated as a pollutant, resulting in the loss of methyl acetate and methanol.

[0035] Therefore, it can be understood that after the reaction of the polytetrahydrofuran reaction unit 110, the residual reaction waste liquid in the reaction device generally includes by-product methyl acetate and part of the unreacted raw material methanol, and there may be a small amount of tetrahydrofuran. The reaction waste liquid is passed into the methyl acetate-methanol separation unit 120 for separation, and the two monomer materials of high purity methyl acetate and methanol are separated by pressure swing distillation, which is suitable for large-scale industrial separation processes.

[0036] Please refer to Figure 2 In this embodiment, the methyl acetate-methanol separation unit 120 includes an azeotropic distillation tower 121, a high-pressure distillation tower 122, a low-pressure distillation tower 123 and a methanol distillation tower 124. In other embodiments, the azeotropic distillation tower 121 may not be provided, and the high-pressure distillation tower 122 may be directly connected to the polytetrahydrofuran reaction unit 110.

[0037] The azeotropic distillation tower 121 includes an azeotropic raw material inlet 1211 , an azeotropic tower bottom outlet 1212 and an azeotropic tower top outlet 1213 . The azeotropic raw material inlet 1211 is connected to the polytetrahydrofuran reaction unit 110 through a pipeline, and the azeotropic tower bottom outlet 1212 is configured to discharge methanol.

[0038] The high-pressure distillation tower 122 includes a high-pressure tower raw material inlet 1221, an azeotrope circulation feed inlet 1222, a high-pressure tower bottom outlet 1223 and a high-pressure tower top outlet 1224. The azeotrope top outlet 1213 is connected to the high-pressure tower raw material inlet 1221 through a pipeline, and the high-pressure tower bottom outlet 1223 is configured to discharge methyl acetate.

[0039] The low-pressure distillation tower 123 includes a low-pressure tower raw material inlet 1231, a low-pressure tower kettle outlet 1232 and a low-pressure tower top outlet 1233. The high-pressure tower top outlet 1224 is connected to the low-pressure tower raw material inlet 1231 through a pipeline, and the azeotrope circulation feed port 1222 is connected to the low-pressure tower top outlet 1233 through a pipeline.

[0040] The methanol distillation tower 124 includes a methanol distillation tower raw material inlet 1241, a methanol tower bottom outlet 1242 and a methanol tower top outlet 1243. The low-pressure tower bottom outlet 1232 is connected to the methanol distillation tower raw material inlet 1241 through a pipeline. The methanol tower bottom outlet 1242 is configured to discharge methanol, and the methanol tower top outlet 1243 is configured to discharge impurities.

[0041] The reaction waste liquid from the polytetrahydrofuran device enters the azeotropic distillation tower 121 for azeotropic distillation, and methyl acetate-methanol azeotrope is obtained at the top of the tower. Methanol that does not participate in the azeotropic reaction is collected in the bottom of the tower. The methyl acetate-methanol azeotrope enters the high-pressure distillation tower 122 again, and methyl acetate in the methyl acetate-methanol azeotrope is separated by pressure. Methyl acetate is collected in the bottom of the tower. A methyl acetate-methanol azeotrope containing a small amount of methyl acetate is obtained at the top of the tower. The methyl acetate-methanol azeotrope containing a small amount of methyl acetate is then passed into the low-pressure distillation tower 123, and methanol in the methyl acetate-methanol azeotrope is separated by pressure. Methanol is collected in the bottom of the tower. The methyl acetate-methanol azeotrope obtained at the top of the tower can enter the high-pressure distillation tower 122 for circulation again, until methyl acetate and methanol are completely separated. The methanol collected from the bottom of the low-pressure distillation tower 123 enters the methanol distillation tower 124 for distillation, and the bottom of the tower obtains methanol with higher purity, while the top of the tower contains impurities containing a small amount of methanol and trace amounts of tetrahydrofuran.

[0042] In this embodiment, the azeotropic raw material inlet 1211, the high-pressure tower raw material inlet 1221, the low-pressure tower raw material inlet 1231 and the methanol distillation tower raw material inlet 1241 are all located in the middle of the corresponding distillation tower to ensure the separation effect of the materials entering the corresponding distillation tower.

[0043] In this embodiment, an azeotropic distillation tower condenser 125 is installed on the pipeline connecting the azeotropic tower top outlet 1213 and the high-pressure tower raw material inlet 1221, and a first branch pipeline is connected to the pipeline connecting the azeotropic distillation tower condenser 125 and the high-pressure tower raw material inlet 1221, and the other end of the first branch pipeline is connected to one end of the azeotropic distillation tower 121 close to the top of the tower.

[0044] The azeotropic distillation tower condenser 125 can condense the methyl acetate-methanol azeotrope flowing out of the azeotropic tower top outlet 1213 into a liquid state, and then send part of it into the high-pressure distillation tower 122 for azeotropic distillation, and the other part is refluxed into the azeotropic distillation tower 121, thereby improving the separation efficiency of the azeotropic distillation tower 121.

[0045] In this embodiment, a high-pressure distillation tower condenser 126 is installed on the pipeline connecting the high-pressure tower top outlet 1224 with the low-pressure tower raw material inlet 1231, and a second branch pipeline is connected to the pipeline connecting the high-pressure distillation tower condenser 126 with the low-pressure tower raw material inlet 1231, and the other end of the second branch pipeline is connected to one end of the high-pressure distillation tower 122 close to the top of the tower.

[0046] The high-pressure distillation tower condenser 126 can condense the methyl acetate-methanol azeotrope flowing out of the high-pressure tower top outlet 1224 into a liquid state, and then send part of it into the low-pressure distillation tower 123 for low-pressure distillation, and the other part is refluxed into the high-pressure distillation tower 122, thereby improving the separation efficiency of the high-pressure distillation tower 122.

[0047] In this embodiment, a low-pressure distillation tower condenser 127 is installed on the pipeline connecting the azeotrope circulation feed inlet 1222 and the low-pressure tower top outlet 1233. The low-pressure distillation tower condenser 127 is also connected to the end of the low-pressure distillation tower 123 close to the tower top through a third branch pipeline.

[0048] The low-pressure distillation tower condenser 127 can condense the methyl acetate-methanol azeotrope flowing out of the low-pressure tower top outlet 1233 into a liquid state, and then send part of it to the low-pressure distillation tower 123, and the other part is refluxed to the high-pressure distillation tower 122, thereby improving the separation efficiency of the low-pressure distillation tower 123.

[0049] In this embodiment, the methanol tower top outlet 1243 is connected to the end of the methanol distillation tower 124 near the tower top through the fourth branch pipeline, and a methanol distillation tower condenser 128 is installed on the fourth branch pipeline, and the fourth branch pipeline is also connected to an impurity discharge pipeline.

[0050] The methanol distillation tower condenser 128 can condense the impurities containing a small amount of methanol and trace amounts of tetrahydrofuran flowing out of the methanol tower top outlet 1243 into liquid, and then partially reflux it into the methanol distillation tower 124 to improve the separation efficiency of the methanol distillation tower 124, and the other part is discharged from the system as impurities through the impurity discharge pipeline.

[0051] In the present embodiment, an azeotropic distillation tower reboiler 129 is also included, and the inlet and outlet of the azeotropic distillation tower reboiler 129 are respectively connected to the pipeline, the pipeline connected to the inlet of the azeotropic distillation tower reboiler 129 is connected to the azeotropic tower bottom outlet 1212, the pipeline connected to the outlet of the azeotropic distillation tower reboiler 129 is connected to one end of the azeotropic distillation tower 121 close to the bottom, and the pipeline connected to the inlet of the azeotropic distillation tower reboiler 129 is also connected to the first methanol collecting pipe.

[0052] The azeotropic distillation tower reboiler 129 can heat part of the methanol collected at the azeotropic tower bottom outlet 1212 and return it to the azeotropic distillation tower 121 to provide heat. Alternatively, the methanol collected at the azeotropic tower bottom outlet 1212 can be directly collected in a methanol storage tank through a pipeline as a product.

[0053] In the present embodiment, a high-pressure distillation tower reboiler 130 is also included, and the inlet and outlet of the high-pressure distillation tower reboiler 130 are respectively connected to pipelines. The pipeline connected to the inlet of the high-pressure distillation tower reboiler 130 is connected to the high-pressure tower bottom outlet 1223, the pipeline connected to the outlet of the high-pressure distillation tower reboiler 130 is connected to one end of the high-pressure distillation tower 122 close to the bottom, and the pipeline connected to the inlet of the high-pressure distillation tower reboiler 130 is also connected to a methyl acetate collecting pipe.

[0054] The high-pressure distillation tower reboiler 130 can heat part of the methyl acetate collected at the high-pressure tower bottom outlet 1223 and return it to the high-pressure distillation tower 122 to provide heat. Alternatively, the methyl acetate collected at the high-pressure tower bottom outlet 1223 can be directly collected in a methyl acetate storage tank through a pipeline as a product.

[0055] In this embodiment, a low-pressure distillation tower reboiler 131 is also included. A low-pressure distillation reflux port is provided at one end of the low-pressure distillation tower 123 close to the tower bottom. The low-pressure distillation reflux port is connected to a pipeline connected to the low-pressure tower bottom outlet 1232 and the methanol distillation tower raw material inlet 1241 through a fifth branch pipeline, and the low-pressure distillation tower reboiler 131 is installed on the fifth branch pipeline.

[0056] The methanol collected at the low-pressure tower kettle outlet 1232 can directly enter the methanol distillation tower 124 through a pipeline, or can be partially heated by the low-pressure distillation tower reboiler 131 and then returned to the low-pressure distillation tower 123 to provide heat.

[0057] In the present embodiment, a methanol distillation tower reboiler 132 is also included, and the inlet and outlet of the methanol distillation tower reboiler 132 are respectively connected to the pipeline, the pipeline connected to the inlet of the methanol distillation tower reboiler 132 is connected to the methanol tower bottom outlet 1242, the pipeline connected to the outlet of the methanol distillation tower reboiler 132 is connected to one end of the methanol distillation tower 124 close to the bottom, and the pipeline connected to the inlet of the methanol distillation tower reboiler 132 is also connected to a second methanol collecting pipe.

[0058] The methanol distillation tower reboiler 132 can heat part of the methanol collected at the methanol tower bottom outlet 1242 and return it to the methanol distillation tower 124 to provide heat. Alternatively, the methanol collected at the methanol tower bottom outlet 1242 can be directly collected in a methanol storage tank through a pipeline as a product.

[0059] This embodiment provides a system 100 for separating and recovering methyl acetate and methanol using a polytetrahydrofuran device, and its working principle is as follows:

[0060] 1) The reaction waste liquid from the polytetrahydrofuran device includes: methyl acetate, methanol and trace amounts of tetrahydrofuran.

[0061] 2) The above-mentioned reaction waste liquid is introduced into the azeotropic distillation tower 121 through the azeotropic raw material inlet 1211 in the middle of the azeotropic distillation tower 121 for azeotropic distillation, and methanol (purity ≥ 99.5wt%) is separated from the bottom of the tower, part of which is extracted, and part of which is heated in the azeotropic distillation tower reboiler 129 and returned to the azeotropic distillation tower 121 to provide heat; the first methyl acetate-methanol azeotrope is separated from the top of the tower. After the first methyl acetate-methanol azeotrope is condensed in the azeotropic distillation tower condenser 125, part of the first methyl acetate-methanol azeotrope is refluxed into the azeotropic distillation tower 121, and part of it is sent to the high-pressure distillation tower 122 for the next separation.

[0062] 3) The first methyl acetate-methanol azeotrope is introduced into the high-pressure distillation tower 122 from the high-pressure tower raw material inlet 1221 in the middle of the high-pressure distillation tower 122 for high-pressure distillation. The methyl acetate (purity is 99.99wt%) is separated from the bottom of the high-pressure distillation tower 122, part of which is extracted, and part of which is heated by the high-pressure distillation tower reboiler 130 and returned to the high-pressure distillation tower 122 to provide heat; the second methyl acetate-methanol azeotrope is separated from the top of the tower. After the second methyl acetate-methanol azeotrope is condensed by the high-pressure distillation tower condenser 126, part of the second methyl acetate-methanol azeotrope is refluxed to the high-pressure distillation tower 122, and part of it is sent to the low-pressure distillation tower 123 for the next separation.

[0063] 4) The second methyl acetate-methanol azeotrope is introduced into the low-pressure distillation tower 123 from the low-pressure tower raw material inlet 1231 in the middle of the low-pressure distillation tower 123 for low-pressure distillation, and crude methanol is separated from the bottom of the low-pressure distillation tower 123. The crude methanol is partially heated by the low-pressure distillation tower reboiler 131 and returned to the low-pressure distillation tower 123 to provide heat, and part of it is sent to the methanol distillation tower 124 for the next separation; the third methyl acetate-methanol azeotrope is separated from the top of the tower. After the third methyl acetate-methanol azeotrope is condensed by the low-pressure distillation tower condenser 127, part of the third methyl acetate-methanol azeotrope is refluxed to the low-pressure distillation tower 123, and part of it is circulated back to the high-pressure distillation tower 122 for separation again.

[0064] 5) The crude methanol separated from the bottom of the low-pressure distillation tower 123 enters the methanol distillation tower 124 for refining. Refined methanol (purity ≥ 99.9%) is extracted from the bottom of the methanol distillation tower 124. Part of the refined methanol is heated by the methanol distillation tower reboiler 132 and then returned to the methanol distillation tower 124 to provide heat. Impurities containing a small amount of methanol and tetrahydrofuran are extracted from the top of the tower, condensed by the methanol distillation tower condenser 128, and part of it is refluxed to the methanol distillation tower 124, and part of it is discharged from the system through a pipeline.

[0065] The system 100 for separating and recovering methyl acetate and methanol by a polytetrahydrofuran device provided by the utility model utilizes the characteristic that the composition of the binary azeotrope system methyl acetate-methanol azeotrope changes significantly with pressure changes, and separates high-purity methyl acetate and methanol materials by pressure swing distillation. Among them, the azeotropic distillation tower 121 realizes the separation of methanol in the reaction waste liquid, obtains methanol purity ≥99.5wt%, and forms a methyl acetate-methanol azeotrope system to improve the purity of methyl acetate. Then, by pressure swing distillation of a high-pressure distillation tower 122 and a low-pressure distillation tower 123, the separation of methyl acetate and methanol in the methyl acetate-methanol azeotrope is realized, and methyl acetate purity ≥99.5wt% and crude methanol are obtained. Then, the crude methanol is further separated and purified by a methanol distillation tower 124 to obtain methanol purity ≥99.5wt%. The system can effectively separate methanol and recycle methanol raw materials. It can also purify methyl acetate, a by-product of the production process of polytetrahydrofuran. It has the advantages of a simple separation system and high purity of the separated products, which greatly reduces the cost of raw materials, thereby reducing production costs and improving production economic benefits.

[0066] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may be subject to various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A system for separating and recovering methyl acetate and methanol in a polytetrahydrofuran device, characterized in that: It includes a polytetrahydrofuran reaction unit and a methyl acetate-methanol separation unit; The methyl acetate-methanol separation unit comprises a high-pressure distillation tower, a low-pressure distillation tower and a methanol distillation tower; The high-pressure distillation tower comprises a high-pressure tower raw material inlet, an azeotrope circulation feed inlet, a high-pressure tower kettle outlet and a high-pressure tower top outlet, wherein the high-pressure tower raw material inlet is connected to the polytetrahydrofuran reaction unit through a pipeline, and the high-pressure tower kettle outlet is configured to discharge methyl acetate; The low-pressure distillation tower comprises a low-pressure tower raw material inlet, a low-pressure tower kettle outlet and a low-pressure tower top outlet, the high-pressure tower top outlet is connected to the low-pressure tower raw material inlet through a pipeline, and the azeotrope circulation feed port is connected to the low-pressure tower top outlet through a pipeline; The methanol distillation tower comprises a methanol distillation tower raw material inlet, a methanol tower bottom outlet and a methanol tower top outlet. The low-pressure tower bottom outlet is connected to the methanol distillation tower raw material inlet through a pipeline, the methanol tower bottom outlet is connected to a methanol production pipeline, and the methanol tower top outlet is configured to discharge impurities.

2. The system according to claim 1, characterized in that It also includes an azeotropic distillation tower, the azeotropic distillation tower includes an azeotropic raw material inlet, an azeotropic tower bottom outlet and an azeotropic tower top outlet, the azeotropic raw material inlet is connected to the polytetrahydrofuran reaction unit through a pipeline, and the azeotropic tower bottom outlet is configured to discharge methanol; An azeotropic distillation tower condenser is installed on the pipeline connecting the azeotropic tower top outlet and the high-pressure tower raw material inlet, and a first branch pipeline is connected to the pipeline connecting the azeotropic distillation tower condenser and the high-pressure tower raw material inlet, and the other end of the first branch pipeline is connected to one end of the azeotropic distillation tower close to the tower top.

3. The system according to claim 2, characterized in that It also includes an azeotropic distillation tower reboiler, the inlet and outlet of the azeotropic distillation tower reboiler are respectively connected to pipelines, the pipeline connected to the inlet of the azeotropic distillation tower reboiler is connected to the outlet of the azeotropic tower kettle, the pipeline connected to the outlet of the azeotropic distillation tower reboiler is connected to one end of the azeotropic distillation tower close to the kettle, and the pipeline connected to the outlet of the azeotropic tower kettle is also connected to a first methanol collecting pipe.

4. The system according to claim 1, characterized in that A high-pressure distillation tower condenser is installed on the pipeline connecting the high-pressure tower top outlet and the low-pressure tower raw material inlet, and a second branch pipeline is connected to the pipeline connecting the high-pressure distillation tower condenser and the low-pressure tower raw material inlet, and the other end of the second branch pipeline is connected to an end of the high-pressure distillation tower close to the tower top.

5. The system according to claim 1, characterized in that A low-pressure distillation tower condenser is installed on the pipeline connecting the azeotrope circulation feed port and the low-pressure tower top outlet. The low-pressure distillation tower condenser is also connected to an end of the low-pressure distillation tower close to the tower top through a third branch pipeline.

6. The system according to claim 1, characterized in that The methanol tower top outlet is connected to an end of the methanol distillation tower close to the tower top through a fourth branch pipeline, and a methanol distillation tower condenser is installed on the fourth branch pipeline, and an impurity discharge pipeline is also connected to the fourth branch pipeline.

7. The system according to claim 1, characterized in that It also includes a high-pressure distillation tower reboiler, wherein the inlet and outlet of the high-pressure distillation tower reboiler are respectively connected to pipelines, the pipeline connected to the inlet of the high-pressure distillation tower reboiler is connected to the outlet of the high-pressure tower kettle, the pipeline connected to the outlet of the high-pressure distillation tower reboiler is connected to one end of the high-pressure distillation tower close to the kettle, and the pipeline connected to the outlet of the high-pressure tower kettle is also connected to a methyl acetate collecting pipe.

8. The system according to claim 1, characterized in that It also includes a low-pressure distillation tower reboiler, and a low-pressure distillation reflux port is provided at one end of the low-pressure distillation tower close to the tower bottom. The low-pressure distillation reflux port is connected to the pipeline connecting the low-pressure tower bottom outlet and the methanol distillation tower raw material inlet through a fifth branch pipeline, and the low-pressure distillation tower reboiler is installed on the fifth branch pipeline.

9. The system according to claim 1, characterized in that It also includes a methanol distillation tower reboiler, the inlet and outlet of the methanol distillation tower reboiler are respectively connected to pipelines, the pipeline connected to the inlet of the methanol distillation tower reboiler is connected to the outlet of the methanol tower kettle, the pipeline connected to the outlet of the methanol distillation tower reboiler is connected to one end of the methanol distillation tower close to the kettle, and the pipeline connected to the outlet of the methanol tower kettle is also connected to a second methanol collecting pipe.

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