Separation device and method for water-methanol-acetonitrile ternary azeotropic system mixture

Abstract

The invention discloses a separation device and method for a water-methanol-acetonitrile ternary azeotropic system mixture. The separating device comprises a dehydrating tower, a high-pressure tower and a low-pressure tower. In a reaction product obtained by a conventional reaction, the content of methanol is often low, and under the condition, two pairs of azeotropic systems often need to be treated in ternary system separation, so that higher equipment and operation investment is caused. The separation method provided by the invention is different from conventional azeotropic system separation modes such as extractive distillation, azeotropic distillation and differential pressure distillation, and adopts a circulating process to improve the concentration of methanol in the raw materials, so that azeotropic pair compounds needing to be separated are reduced, and the number of separation equipment for a water-methanol-acetonitrile ternary azeotropic system mixture is reduced.

Description

Technical Field

[0001] The present application relates to a device and method for separating a water-methanol-acetonitrile ternary azeotropic mixture, and belongs to the technical field of chemical industry. Background Art

[0002] The acetonitrile-methanol-water mixed system is a key separation raw material involved in the new acetonitrile production process. The water-acetonitrile system will form an azeotropic system under conditions above 2kPaA absolute pressure, and the azeotropic composition molar ratio is 33:66 at normal pressure, and the azeotropic temperature is 76.6°C; the acetonitrile-methanol system will form an azeotropic system at any operable pressure, and the acetonitrile-methanol azeotropic composition molar ratio is 18.9:81.1 at normal pressure, and the azeotropic temperature is 63.64°C. The methanol content in the reaction products obtained by conventional reactions is often low. In this case, the separation of the ternary system often requires the treatment of two pairs of azeotropic systems. The traditional separation methods of azeotropic mixtures generally include extractive distillation separation, azeotropic distillation separation, differential pressure distillation separation, etc., which require more separation equipment, resulting in higher equipment and operating investment. If the process flow can be shortened and the number of separation equipment can be reduced, the production cost will be greatly reduced. Summary of the invention

[0003] According to one aspect of the present application, a separation device for a multi-azeotropic mixture is provided, the separation device comprising a dehydration tower, a high-pressure tower, and a low-pressure tower. The concentration of methanol in the raw material is increased, thereby reducing the azeotropic compounds that need to be separated, and reducing the number of separation devices for the water-methanol-acetonitrile ternary azeotropic system mixture. It can be used for continuous separation of a water-methanol-acetonitrile ternary azeotropic system with a high acetonitrile-methanol ratio, is easy to operate, has a small number of production equipment, and can save fixed investment.

[0004] The separation device of the multi-azeotropic mixture comprises a dehydration tower I, a high-pressure tower II and a low-pressure tower III.

[0005] Optionally, the dehydration tower I is provided with a feed inlet I-1, a tower top discharge port I-2, and a tower bottom discharge port I-3.

[0006] Optionally, the high-pressure tower II is provided with feed ports II-1, II-2, a tower top discharge port II-3, and a tower bottom discharge port II-4.

[0007] Optionally, the low-pressure tower III is provided with a feed inlet III-1, a tower top discharge outlet III-2, and a tower bottom discharge outlet III-3.

[0008] Optionally, the tower top outlet I-2 is connected to the feed port II-1 via a pipeline.

[0009] Optionally, the tower top discharge port II-3 is connected to the feed port III-1 via a pipeline.

[0010] Optionally, the tower top discharge port III-2 is connected to the feed port II-2 via a pipeline.

[0011] Optionally, the tower bottom discharge port III-3 is connected to the feed port I-1 via a pipeline.

[0012] Optionally, the reflux ratio of the dehydration tower I is 0.1-10.

[0013] Optionally, the reflux ratio of the dehydration tower I is independently selected from any value among 0.1, 2, 4, 6, 8, 10 or any value between any two of the above points.

[0014] Optionally, the dehydration tower I has 10 to 80 theoretical plates.

[0015] Optionally, the number of theoretical plates of the dehydration tower I is independently selected from any value among 10, 30, 50, 80 or any value between any two of the above points.

[0016] Optionally, the reflux ratio of the high-pressure tower II is 3-30.

[0017] Optionally, the reflux ratio of the high-pressure column II is independently selected from any value among 3, 10, 15, 20, 25, 30 or any value between any two of the above points.

[0018] Optionally, the high-pressure tower II has 10 to 80 theoretical plates.

[0019] Optionally, the number of theoretical plates of the high-pressure tower II is independently selected from any value among 10, 30, 50, 80 or any value between any two of the above points.

[0020] Optionally, the reflux ratio of the low-pressure tower III is 3-30.

[0021] Optionally, the reflux ratio of the low-pressure tower III is independently selected from any value among 3, 10, 15, 20, 25, 30 or any value between any two of the above points.

[0022] Optionally, the number of theoretical plates of the low-pressure tower III is 10 to 80.

[0023] Optionally, the number of theoretical plates of the low-pressure tower III is independently selected from any value among 10, 30, 50, 80 or any value between any two of the above points.

[0024] According to still another aspect of the present application, a method for separating multiple azeotropic mixtures is provided.

[0025] The method comprises: introducing a water-methanol-acetonitrile ternary azeotropic system mixture as a raw material into a separation device to obtain water, acetonitrile and methanol.

[0026] Optionally, the following steps are included:

[0027] (1) the raw material is mixed with the circulating methanol and then enters the dehydration tower I for separation, and a separation product containing water is obtained from the tower bottom outlet I-3, and a methanol-acetonitrile azeotropic mixture is obtained from the tower top outlet I-2;

[0028] (2) the methanol-acetonitrile azeotropic mixture flows out from the tower top outlet I-2, enters the high-pressure tower II from the feed port II-1, is pressurized, and separated, and a separated product containing acetonitrile is obtained from the tower bottom outlet II-4, and a methanol-acetonitrile high-pressure azeotropic mixture is obtained from the tower top outlet II-3;

[0029] (3) The methanol-acetonitrile high-pressure azeotropic mixture flows out from the tower top outlet II-3, enters the low-pressure tower III from the feed port III-1, and is depressurized. A product containing methanol is separated from the tower bottom outlet III-3, and a methanol-acetonitrile low-pressure azeotropic mixture is obtained from the tower top outlet III-2.

[0030] Optionally, the raw material is a ternary azeotropic mixture of water-methanol-acetonitrile.

[0031] Optionally, the methanol-acetonitrile low-pressure azeotropic mixture flows out from the tower top outlet III-2 and enters the high-pressure tower II from the feed inlet II-2 for circulation and separation.

[0032] Optionally, the methanol flows out from the bottom outlet III-3, and the circulating methanol circulates into the dehydration tower I from the feed inlet I-1 as a mixed raw material.

[0033] Optionally, the molar composition of the raw materials is: 0.01-75% methanol, 20-80% acetonitrile, and 10-70% water.

[0034] Optionally, the molar composition of the methanol is independently selected from any value of 0.01%, 0.05%, 0.1%, 0.5%, 1%, 5%, 10%, 30%, 45%, 60%, 75% or any value between any two of the above points.

[0035] Optionally, the molar composition of the acetonitrile is independently selected from any value among 20%, 30%, 40%, 50%, 60%, 70%, 80% or any value between any two of the above points.

[0036] Optionally, the molar composition of the water is independently selected from any value of 10%, 20%, 30%, 40%, 50%, 60%, 70% or any value between any two of the above points.

[0037] Optionally, in step (1), the molar ratio of the methanol to the raw material is 0.5 to 5.

[0038] Optionally, the molar ratio of the methanol to the raw material is independently selected from any value among 0.5, 2, 3, 4, 5 or any value between any two of the above points.

[0039] Optionally, the top temperature of the dehydration tower I is 30-100°C.

[0040] Optionally, the top temperature of the dehydration tower I is independently selected from any value of 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C or any value between any two of the above points.

[0041] Optionally, the operating pressure of the dehydration tower I is 100-500 kPaA.

[0042] Optionally, the operating pressure of the dehydration tower I is independently selected from any value among 100kPaA, 200kPaA, 300kPaA, 400kPaA, 500kPaA or any value between any two of the above points.

[0043] Optionally, the top temperature of the high-pressure tower II is 40-140°C.

[0044] Optionally, the top temperature of the high-pressure tower II is independently selected from any value of 40°C, 60°C, 80°C, 100°C, 120°C, 140°C or any value between any two of the above points.

[0045] Optionally, the operating pressure of the high-pressure tower II is 100 to 500 kPaA.

[0046] Optionally, the operating pressure of the high-pressure column II is independently selected from any value among 100 kPaA, 200 kPaA, 300 kPaA, 400 kPaA, 500 kPaA or any value between any two of the above points.

[0047] Optionally, the top temperature of the low-pressure tower III is 30-100°C.

[0048] Optionally, the top temperature of the low-pressure tower III is independently selected from any value of 30°C, 50°C, 70°C, 100°C or any value between any two of the above points.

[0049] Optionally, the operating pressure of the low-pressure tower III is 100 to 300 kPaA.

[0050] Optionally, the operating pressure of the low-pressure column III is independently selected from any value among 100 kPaA, 200 kPaA, 300 kPaA or any value between any two of the above points.

[0051] Optionally, the molar purity of the methanol obtained in step (3) is 99.99%.

[0052] The beneficial effects of this application:

[0053] The present application adopts a circulation process to increase the concentration of methanol in the raw material, thereby reducing the azeotropic compounds that need to be separated and the number of separation equipment for the water-methanol-acetonitrile ternary azeotropic system mixture. It can be used for the continuous separation of the water-methanol-acetonitrile ternary azeotropic system with a high acetonitrile-methanol ratio. The process is simple and easy to operate, the number of production equipment is small, and fixed investment can be saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a schematic diagram of a method for separating multiple azeotropic mixtures in one embodiment of the present application.

[0055] in:

[0056] 1. Dehydration tower I; 2. High-pressure tower II; 3. Low-pressure tower III; 4. Feed inlet I-1; 5. Tower bottom discharge port I-3; 6. Tower top discharge port I-2; 7. Feed inlet II-1; 8. Feed inlet II-2; 9. Tower top discharge port II-3; 10. Tower bottom discharge port II-4; 11. Feed inlet III-1; 12. Tower top discharge port III-2; 13. Tower bottom discharge port III-3. DETAILED DESCRIPTION

[0057] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0058] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0059] According to one embodiment of the present application, a water-methanol-acetonitrile ternary azeotropic system mixture enters a dehydration tower, water is separated at the bottom of the tower, and a methanol-acetonitrile mixture is separated at the top of the tower. The methanol-acetonitrile mixture enters a high-pressure tower, and the high-pressure tower separates acetonitrile at the bottom of the tower by a boost operation, and an acetonitrile-methanol azeotropic mixture under high pressure is obtained at the top of the tower. The ethanol-methanol azeotropic mixture enters a low-pressure tower, reduces the operating pressure, and obtains methanol at the bottom of the tower. Part of the methanol is circulated to the dehydration tower as a mixed raw material, and an acetonitrile-methanol mixture under low pressure is obtained at the top of the tower, and enters a high-pressure tower for circulation and separation.

[0060] Device example 1

[0061] like Figure 1 The multi-azeotropic mixture separation device comprises a dehydration tower 1, a high-pressure tower 2, and a low-pressure tower 3.

[0062] The dehydration tower 1, the high-pressure tower 2 and the low-pressure tower 3 are connected in sequence; the dehydration tower 1 is provided with a feed port I-1, a tower top discharge port I-2 and a tower bottom discharge port I-3; the high-pressure tower 2 is provided with a feed port II-1, a feed port II-2, a tower top discharge port II-3 and a tower bottom discharge port II-4; the low-pressure tower 3 is provided with a feed port III-1, a tower top discharge port III-2 and a tower bottom discharge port III-3; the tower top discharge port I-2 is connected to the feed port II-1 via a pipeline; the tower top discharge port II-3 is connected to the feed port III-1 via a pipeline; the tower top discharge port III-2 is connected to the feed port II-2 via a pipeline; the tower bottom discharge port III-3 is connected to the feed port I-1 via a pipeline.

[0063] Example 1

[0064] The multi-azeotropic mixture separation device described in Device Example 1 is used, and the methanol-acetonitrile-water azeotropic mixture (molar composition of methanol 34.3%, acetonitrile 32.6%, water 33.1%) is mixed with 1.18 times the molar flow of circulating methanol and then sent to the dehydration tower 1. The top pressure of the dehydration tower 1 is 110kPaA, the top temperature is 66°C, 42 theoretical plates are provided, and the reflux ratio is 1.7. Waste water is separated at the bottom of the tower, and the methanol-acetonitrile mixture is separated at the top of the tower and sent to the high-pressure tower 2. The top pressure of the high-pressure tower 2 is 300kPaA, the top temperature is 95°C, 50 theoretical plates are provided, and the reflux ratio is 10. Through the pressure-increasing operation, acetonitrile with a molar purity of 99.98% is separated at the bottom of the tower, and an acetonitrile-methanol azeotropic mixture under high pressure is obtained at the top of the tower and sent to the low-pressure tower 3. The low-pressure tower 3 reduces the operating pressure, the tower top pressure is 110kPaA, the tower top temperature is 66°C, 50 theoretical plates are set, the reflux ratio is 15, and methanol with a molar purity of 99.99% is obtained at the bottom of the tower. Part of the methanol is recycled back to the inlet of the dehydration tower 1 and used as a mixed raw material. An acetonitrile-methanol mixture under low pressure is obtained at the top of the tower and sent to the high-pressure tower 2 for circulation and separation.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention.

[0066] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A separation device for a multi-azeotropic mixture, characterized in that: It includes dehydration tower I, high pressure tower II and low pressure tower III; The dehydration tower I is provided with a feed inlet I-1, a tower top discharge port I-2, and a tower bottom discharge port I-3; The high-pressure tower II is provided with a feed port II-1, a feed port II-2, a tower top discharge port II-3, and a tower bottom discharge port II-4; The low-pressure tower III is provided with a feed inlet III-1, a tower top discharge outlet III-2, and a tower bottom discharge outlet III-3; The tower top outlet I-2 is connected to the feed inlet II-1 via a pipeline; The tower top outlet II-3 is connected to the feed inlet III-1 via a pipeline.

2. The separation device according to claim 1, characterized in that: The tower top outlet III-2 is connected to the feed inlet II-2 via a pipeline.

3. The separation device according to claim 1, characterized in that: The tower bottom outlet III-3 is connected to the feed inlet I-1 via a pipeline.

4. The separation device according to claim 1, characterized in that: The reflux ratio of the dehydration tower I is 0.1 to 10; The number of theoretical plates of the dehydration tower I is 10 to 80; The reflux ratio of the high-pressure tower II is 3 to 30; The number of theoretical plates of the high-pressure column II is 10 to 80; The reflux ratio of the low pressure tower III is 3 to 30; The number of theoretical plates of the low-pressure tower III is 10 to 80.

5. A method for separating a multi-azeotropic mixture, characterized in that: A separation device for a multi-azeotropic mixture according to any one of claims 1 to 4; The steps include: (1) the raw material is mixed with the circulating methanol and then enters the dehydration tower I for separation, and a separation product containing water is obtained from the tower bottom outlet I-3, and a methanol-acetonitrile azeotropic mixture is obtained from the tower top outlet I-2; (2) the methanol-acetonitrile azeotropic mixture flows out from the tower top outlet I-2, enters the high-pressure tower II from the feed port II-1, is pressurized, and separated, and a separated product containing acetonitrile is obtained from the tower bottom outlet II-4, and a methanol-acetonitrile high-pressure azeotropic mixture is obtained from the tower top outlet II-3; (3) the methanol-acetonitrile high-pressure azeotropic mixture flows out from the tower top outlet II-3, enters the low-pressure tower III from the feed port III-1, and is depressurized, and a product containing methanol is separated from the tower bottom outlet III-3, and a methanol-acetonitrile low-pressure azeotropic mixture is obtained from the tower top outlet III-2; The raw material is a ternary azeotropic mixture of water, methanol and acetonitrile.

6. The separation method according to claim 5, characterized in that The methanol-acetonitrile low-pressure azeotropic mixture flows out from the tower top outlet III-2 and enters the high-pressure tower II from the feed inlet II-2 for cyclic separation; Preferably, the methanol flows out from the bottom outlet III-3, and the circulating methanol circulates into the dehydration tower I from the feed inlet I-1 as a mixed raw material.

7. The separation method according to claim 5, characterized in that The molar composition of the raw materials is: 0.01-75% methanol, 20-80% acetonitrile, and 10-70% water; The molar ratio of the circulating methanol to the raw material is 0.5-5.

8. The separation method according to claim 5, characterized in that The top temperature of the dehydration tower I is 30-100°C; The operating pressure of the dehydration tower I is 100-500 kPaA.

9. The separation method according to claim 5, characterized in that The top temperature of the high-pressure tower II is 40-140°C; The operating pressure of the high-pressure tower II is 100-500 kPaA; Preferably, the top temperature of the low-pressure tower III is 30 to 100° C.; The operating pressure of the low-pressure tower III is 100-300 kPaA.

10. The separation method according to claim 5, characterized in that The molar purity of the methanol obtained in step (3) is 99.99%.

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