Heat pump assisted integrated extractive distillation separation method for diethyl ether-methyl formate-n-pentane azeotropic mixture

Abstract

The continuous production heat pump assisted integrated extractive distillation device is adopted to realize high-purity separation and recovery of the diethyl ether-methyl formate-n-pentane azeotrope, and separation is realized by utilizing the characteristic that the extraction agent has great influence on the relative volatility of the diethyl ether-methyl formate-n-pentane azeotrope. The purity of the separated diethyl ether, n-pentane and methyl formate reaches 99.9% or above, high-purity recycling of the extraction agent can be achieved, the separation cost is greatly reduced, and the method is low in energy consumption and flexible to operate.

Description

Technical field

[0001] The invention belongs to the field of chemical separation and purification, and particularly relates to a method for separating an azeotropic mixture of ether, methyl formate and n-pentane by using a heat pump-assisted integrated extraction and distillation method. [Background Technology]

[0002] The reduction of CO by H₂ in 2-methoxyethanol produces diethyl ether and methyl formate. Diethyl ether is often used to measure the effectiveness of hot water pumps. Diethyl ether, n-pentane, and methyl formate are commonly used as organic solvents in the chemical, pharmaceutical, and industrial sectors. However, the mixture of diethyl ether, n-pentane, and methyl formate contains three binary azeotropes, making efficient separation and recovery of this ternary mixture a crucial challenge.

[0003] Patent (CN106660920A) discloses a method for separating methyl formate from a mixture of dimethyl ether, methanol and methyl formate to recover dimethyl ether and methanol. The method is implemented by catalytic dehydration and hydrolysis of the mixture of methanol and methyl acetate. However, the method heats the methyl formate to steam and discharges it, which does not meet economic and environmental requirements.

[0004] Patent (CN101380522A) discloses a pressurized distillation device and a method for separating ether-ethanol solutions. The method specifically controls the pressure in the distillation tower by changing the size of the condenser heat exchange area. However, the method has strict parameter control and is difficult to operate.

[0005] The present invention utilizes a continuous heat pump-assisted integrated extraction and distillation apparatus to achieve high-purity separation and recovery of an azeotropic mixture of ether, methyl formate, and n-pentane. This separation is achieved by utilizing the extractant's significant influence on the relative volatility of the azeotropic mixture. The purities of the separated ether, n-pentane, and methyl formate all exceed 99.9%. The extractant can also be recovered and reused at high purity, significantly reducing separation costs. The method also features low energy consumption and flexible operation. [Summary of the invention]

[0006] [Technical problems to be solved]

[0007] The present invention aims to provide a method for separating an azeotropic mixture of ether, methyl formate and n-pentane by heat pump-assisted integrated extraction and distillation, thereby realizing a process design for efficiently separating the azeotropic mixture.

[0008] [Technical solution]

[0009] The present invention is achieved through the following technical solutions.

[0010] A method for separating an azeotropic mixture of ether, methyl formate and n-pentane by heat pump-assisted integrated extraction and distillation, characterized in that the device for separating the azeotropic mixture of ether, methyl formate and n-pentane mainly comprises the following parts:

[0011] Distillation tower 1 (T1), distillation tower 2 (T2), extractant recovery tower (T3), condenser 2 (CL2), condenser 3 (CL3), overhead storage tank 2 (RD2), overhead storage tank (RD3), reboiler 1 (C1), reboiler 3 (C3), cooler (COL), centrifugal pump 1 (P1), centrifugal pump 2 (P2), centrifugal pump 3 (P3), compressor (Comp), heat exchanger 1 (H1), heat exchanger 2 (H2); the added fresh extractant is mixed with the circulating extractant cooled by the cooler (COL) and then connected to the distillation tower 1 (T1) through a pipeline; the overhead vapor of the distillation tower (T1) is compressed and heated by the compressor (Comp) and then used in the reboiler 1 (C1) is heated; the distillation tower 1 (T1) is connected to the distillation tower 2 (T2) through a pipeline via a centrifugal pump 1 (P1); the material distilled from the top of the distillation tower 2 (T2) is condensed by a condenser (CL2) and enters the tower top storage tank (RD2), part of which is refluxed and part is extracted as a product; the distillation tower 2 (T2) is connected to the extractant recovery tower (T3) through a pipeline via a centrifugal pump 2 (P2), the material distilled from the top of the extractant recovery tower (T3) is condensed by a condenser (CL3) and enters the tower top storage tank (RD3); the bottom discharge of the extractant recovery tower (T3) is heated with the distillation tower 2 (T2) through a heat exchanger 2 (H2), and then heat-exchanged with the distillation tower (T1) through a heat exchanger 1 (H2).

[0012] The invented method for separating an azeotropic mixture of ether, methyl formate and n-pentane by extractive distillation mainly comprises the following steps:

[0013] (1) A raw material mixture of ether, n-pentane and methyl formate is introduced into a distillation tower 1 (T1), where ether is separated. The distillate at the top of the distillation tower 1 (T1) is pressurized and heated by a compressor (Comp) and heat-exchanged in a reboiler 1 (C1). A portion of the mixed flow at the bottom of the distillation tower 1 (T1) is reheated by the residual heat at the bottom of the extractant recovery tower (T3) through heat exchangers 2 (H2) and 3 (H3), and then reduced to atmospheric pressure through a pressure reducing valve and returned to the distillation tower (T1). The other portion of the mixed flow is introduced from the bottom of the distillation tower 1 (T1) into the distillation tower 2 (T2) through a centrifugal pump 1 (P1).

[0014] (2) In distillation tower 2 (T2), n-pentane is separated. The overhead distillate from distillation tower 2 (T2) is condensed in condenser (CL2) and enters overhead storage tank (RD2), with a portion refluxed and a portion withdrawn as product. The bottom stream of distillation tower (T2) is heated via heat exchanger (H2) using waste heat from the bottom of the extractant recovery tower (T3). The heated bottom mixture flows through centrifugal pump 2 (P2) and is then passed to the extractant recovery tower (T3).

[0015] (3) In the extractant recovery tower (T3), methyl formate is separated. The overhead distillate of the distillation tower 3 (T3) is condensed in the condenser (CL3) and enters the overhead storage tank (RD3). A portion of it is refluxed and a portion is extracted as a product. The extractant recovery tower (T3) and the extractive distillation tower (T2) exchange heat through the heat exchanger (H2). The extractant is cooled and then returns to the distillation tower 1 (T1) and the distillation tower 2 (T2) through the cooler (COL) and the replenished extractant for recycling.

[0016] According to another preferred embodiment of the present invention, the method for separating the ether-methyl formate-n-pentane mixture by extractive distillation is characterized in that a heat-integrated assisted extractive distillation process is used to reduce gas emissions of the entire process by 35%, energy consumption by 35.09%, and TAC by 22.1%.

[0017] [Beneficial Effects]

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The beneficial effect of the present invention is that the heat pump-assisted integrated extraction distillation method is used to achieve efficient separation of the azeotropic mixture of ether, methyl formate and n-pentane.

[0020] (2) The present invention has the advantages of simple process, less investment in equipment, and high purity of ether, methyl formate and n-pentane after separation.

[0021] (3) Effectively utilize the heat load of the extractant recovery tower reboiler to reduce energy consumption and production costs during the production process.

Brief Description of the Drawings

[0022] The accompanying figure is a schematic diagram of a heat pump-assisted integrated extraction and distillation azeotropic mixture of ether, methyl formate and n-pentane.

[0023] In the figure, there are distillation tower 1 (T1), distillation tower 2 (T2), extractant recovery tower (T3), condenser 2 (CL2), condenser 3 (CL3), overhead storage tank 2 (RD2), overhead storage tank (RD3), reboiler 1 (C1), reboiler 3 (C3), cooler (COL), centrifugal pump 1 (P1), centrifugal pump 2 (P2), centrifugal pump 3 (P3), compressor (Comp), heat exchanger 1 (H1), and heat exchanger 2 (H2). [Specific implementation method]

[0024] The following is further described with reference to the accompanying drawings, which does not limit the scope of the present invention.

[0025] Example 1:

[0026] The feed flow rate is 100 kmol / h, and the feed contains 30% diethyl ether, 30% methyl formate, and 40% n-pentane (molar fraction). The number of theoretical plates of the distillation tower (T1) is 164. The mixture of diethyl ether, methyl formate, and n-pentane first enters the distillation tower 1 (T1), and the top steam is heated by the compressor (Comp) to heat the bottom flow of the tower. At the same time, a part of the mixed flow at the bottom of the distillation tower 1 (T1) passes through the heat exchanger 2 (H2) and the heat exchanger 3 (H3) and is heated again by the waste heat at the bottom of the extractant recovery tower (T3). 40 kmol is obtained at the top of the distillation tower (T1). / h of 99.99% n-pentane; the distillation tower (T2) has 65 theoretical plates, the mixture enters from the 23rd plate of the distillation tower 2 (T2), and is heated through a heat exchanger (H2) using the waste heat from the bottom of the extractant recovery tower (T3), with a flow rate of 282 kmol / h, and 30 kmol / h of 99.97% ether is obtained at the top of the tower; the extractant recovery tower (T3) has 13 theoretical plates, the mixture enters from the 6th plate of the extractant recovery tower (T3), with a flow rate of 315 kmol / h, and 30 kmol / h of 99.97% methyl formate is obtained at the top of the tower. After separation, the purity of the ether is 99.97%, and the yield is 99.97%; the purity of the n-pentane is 99.99%, and the yield is 99.99%; the purity of the methyl formate is 99.97%, and the yield is 99.97%.

[0027] Example 2:

[0028] The feed flow rate is 100 kmol / h, the feed contains 30% ether, 30% methyl formate, and 40% n-pentane (molar fraction), and the number of theoretical plates of the distillation tower (T1) is 164. The mixture of ether, methyl formate, and n-pentane first enters the distillation tower 1 (T1), and 40 kmol / h of 99.99% n-pentane is obtained at the top of the distillation tower (T1); the number of theoretical plates of the distillation tower (T2) is 65, and the mixture is discharged from the distillation tower 2 (T2). The extractant recovery tower (T3) has 13 theoretical plates, and the mixture enters the extractant recovery tower (T3) from the sixth plate at a flow rate of 315 kmol / h, producing 30 kmol / h of 99.97% methyl formate at the top of the tower. The bottom discharge of the extractant recovery tower (T3) exchanges heat with the reboiler of the distillation tower (T1). After separation, the purity of the ether is 99.97%, and the yield is 99.97%. The purity of the n-pentane is 99.99%, and the yield is 99.99%. The purity of the methyl formate is 99.97%, and the yield is 99.97%.

Claims

1. A method for separating an azeotropic mixture of ether, methyl formate and n-pentane by heat pump-assisted integrated extraction and distillation, characterized in that The device for separating the ether-methyl formate-n-pentane azeotropic system mainly comprises the following parts: a distillation tower 1 (T1), a distillation tower 2 (T2), an extractant recovery tower (T3), a condenser 2 (CL2), a condenser 3 (CL3), a tower top storage tank 2 (RD2), a tower top storage tank (RD3), a reboiler 1 (C1), a reboiler 3 (C3), a cooler (COL), a centrifugal pump 1 (P1), a centrifugal pump 2 (P2), a centrifugal pump 3 (P3), a compressor (Comp), a heat exchanger 1 (H1), and a heat exchanger 2 (H2); the fresh extractant added is mixed with the circulating extractant cooled by the cooler (COL) and then connected to the distillation tower 1 (T1) through a pipeline; the vapor at the top of the distillation tower (T1) is discharged by the compressor ( Comp) is compressed and heated and then used to heat reboiler 1 (C1); distillation tower 1 (T1) is connected to distillation tower 2 (T2) through a pipeline via centrifugal pump 1 (P1); the material distilled from the top of distillation tower 2 (T2) is condensed in condenser (CL2) and enters the tower top storage tank (RD2), part of which is refluxed and part is withdrawn as product; distillation tower 2 (T2) is connected to extractant recovery tower (T3) through a pipeline via centrifugal pump 2 (P2); the material distilled from the top of extractant recovery tower (T3) is condensed in condenser (CL3) and enters the tower top storage tank (RD3); the bottom discharge of extractant recovery tower (T3) is exchanged with distillation tower 2 (T2) through heat exchanger 2 (H2), and then heat exchanged with distillation tower (T1) through heat exchanger 1 (H2).

2. According to claim 1, it is characterized in that A method for separating an azeotropic mixture of ether, methyl formate and n-pentane by heat pump-assisted integrated extraction and distillation is as follows: A raw material mixture of ether, n-pentane, and methyl formate is passed into distillation tower 1 (T1). Within distillation tower 1 (T1), ether is separated. The distillate from the top of distillation tower 1 (T1) is pressurized and heated by a compressor (Comp) and then heat-exchanged in reboiler 1 (C1). A portion of the mixed stream at the bottom of distillation tower 1 (T1) is reheated by the residual heat from the bottom of the extractant recovery tower (T3) through heat exchangers 2 (H2) and 3 (H3). The stream is then reduced to atmospheric pressure through a pressure reducing valve and returned to distillation tower (T1). The remaining portion is passed from the bottom of distillation tower 1 (T1) through centrifugal pump 1 (P1) and passed to distillation tower 2 (T2). Within distillation tower 2 (T2), n-pentane is separated. The distillate from the top of distillation tower 2 (T2) is condensed in a condenser (CL2) and then entered into an overhead storage tank (RD2). A portion is refluxed, and a portion is withdrawn as product. The bottom stream of the distillation tower (T2) is heated by the waste heat from the bottom of the extractant recovery tower (T3) through the heat exchanger (H2). The heated bottom mixture flows through the centrifugal pump 2 (P2) and is passed to the extractant recovery tower (T3). To achieve the separation of methyl formate, the overhead distillate from distillation tower 3 (T3) is condensed in a condenser (CL3) and then enters an overhead storage tank (RD3), where a portion is refluxed and a portion is withdrawn as product. The extractant recovery tower (T3) exchanges heat with the extractive distillation tower (T2) via a heat exchanger (H2), cooling the extractant. The extractant is then returned to distillation tower 1 (T1) and distillation tower 2 (T2) for recycling after passing through a cooler (COL) and replenishing the extractant.

3. According to claim 1, it is characterized in that: The use of heat-integrated assisted extraction distillation process reduces gas emissions of the entire process by 35%, energy consumption by 35.09%, and TAC by 22.1%.

4. According to claim 1, it is characterized in that: After separation, the purity of ether was 99.97%, and the yield was 99.97%. The purity of n-pentane was 99.99%, and the yield was 99.99%. The purity of methyl formate was 99.97%, and the yield was 99.97%.

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