Method for extracting, rectifying and separating acetone, methanol and dichloromethane by using mixed extracting agent

Abstract

The invention relates to a method for separating acetone, methanol and dichloromethane through extractive distillation by using a mixed extractant. The extractive distillation has the characteristics of simplicity in operation, high flexibility and high separation efficiency. Compared with a single extraction agent, the mixed extraction agent can generate a unique effect, so that the azeotrope is easier to separate. On the basis of extractive distillation of a mixed extractant, a heat pump technology and a heat integration technology are combined to reinforce the process, efficient separation of a ternary mixture is realized, the molar fraction of acetone after separation is greater than 99.93%, the molar fraction of methanol is greater than 99.92%, and the molar fraction of dichloromethane is greater than 99.97%. The method solves the problem that the azeotropic system is difficult to separate by using conventional rectification, is simple to operate, is economical and environment-friendly, and can realize effective separation of the ternary azeotropic mixture.

Description

Technical Field

[0001] The present invention belongs to the field of chemical separation and purification, and particularly relates to a method for separating an azeotrope of acetone, methanol, and dichloromethane by extractive distillation using a mixed extractant.

Background Art

[0002] Acetone, methanol, and dichloromethane are important chemical raw materials widely used in the chemical industry. Acetone and methanol can be used to synthesize organic chemicals and can also be used to manufacture gasoline additives and drugs. In addition, acetone and methanol are key organic solvents due to their excellent solubility. Acetone and methanol are the main components of hydrocarbons synthesized by the Fischer-Tropsch process. Dichloromethane is a naturally occurring compound widely used as a commercial paint stripper and degreaser and as an essential industrial solvent. This chemical is commonly used in consumer products and exposure can be fatal without adequate protection.

[0003] Since there are two binary azeotropes in the acetone-methanol-dichloromethane mixture, namely acetone-methanol (azeotropic point 55.24 °C, 77.78 wt% acetone, 22.22 wt% methanol), and methanol-dichloromethane (azeotropic point 37.6 °C, 13.87 wt% methanol, 86.13 wt% dichloromethane), it is difficult to obtain high-purity single substances by conventional distillation. Therefore, special distillation methods are required to separate the azeotrope.

[0004] The present invention uses extractive distillation with a mixed extractant to separate the azeotropic system of acetone, methanol, and dichloromethane. By taking advantage of the characteristics of simple operation, high flexibility, and high separation efficiency of extractive distillation, heat pump technology and heat integration technology are added on the basis of extractive distillation with a mixed extractant, and corresponding process schemes are designed to improve the separation performance of extractive distillation. The present invention is applicable to mixtures of acetone, methanol, and dichloromethane and can effectively separate ternary azeotropic mixtures through extractive distillation.

Summary of the Invention

[0005] [Technical Problems to be Solved]

[0006] The purpose of the present invention is to provide a method for separating a mixture of acetone, methanol, and dichloromethane by extractive distillation using a mixed extractant, and to achieve a process design for highly efficient separation of ternary azeotropic mixtures by extractive distillation.

[0007] [Technical Solutions]

[0008] The present invention proposes a method for separating acetone, methanol, and dichloromethane by extractive distillation using a mixed extractant. Extractive distillation has the characteristics of simple operation, high flexibility, and high separation efficiency. Compared with a single extractant, the mixed extractant will produce a unique effect, making the separation of azeotropes easier, and the proposed process can achieve highly efficient separation of the ternary mixture of acetone, methanol, and dichloromethane.

[0009] A method for separating acetone, methanol, and dichloromethane by extractive distillation using a mixed extractant proposed by the present invention is characterized in that the device for separating the azeotropic system of acetone, methanol, and dichloromethane mainly includes the following parts:

[0010] Distillation columns (T1), (T2), (T3), condensers (COL), top storage tanks (C1), (C2), (C3), reboilers (H1), (H2), (H3), condensers (CL1), (CL2), (CL3); The supplementary fresh mixed extractant and the recycled extractant are connected to the distillation columns (T1) and (T2) through pipelines; The distillation column (T1) is connected to the distillation column (T2) through a pipeline; The distillation column (T2) is connected to the distillation column (T3) through a pipeline; The distillation column (T3) is connected to the distillation columns (T1) and (T2) through a pipeline via the condenser (COL); The condenser (CL1) is connected to the distillation column (T1) and the top storage tank (C1), the condenser (CL2) is connected to the distillation column (T2) and the top storage tank (C2), and the condenser (CL3) is connected to the distillation column (T3) and the top storage tank (C3); The reboilers (H1), (H2), (H3) are respectively connected to the distillation columns (T1), (T2), (T3).

[0011] A method for separating acetone, methanol, and dichloromethane by extractive distillation using a mixed extractant invented mainly includes the following steps:

[0012] (1) The raw material mixture of acetone, methanol, and dichloromethane and the recycled mixed extractant are respectively added to the distillation column (T1) from the lower part and the upper part of the column. In the distillation column (T1), the separation of dichloromethane is achieved. A part of the bottom stream of the distillation column (T1) is returned to the distillation column (T1) after heat exchange in the reboiler (H1), and a part is fed into the distillation column (T2) as feed; Dichloromethane is condensed by the condenser (CL1) and then enters the top storage tank (C1). A part is refluxed, and the other part is taken out from the top of the distillation column (T1).

[0013] (2) In the distillation column (T2), the separation of acetone is achieved. A part of the bottom stream of the distillation column (T2) is returned to the distillation column (T2) after heat exchange in the reboiler (H2), and a part is fed into the distillation column (T3) as feed; Acetone is condensed by the condenser (CL2) and then enters the top storage tank (C2). A part is refluxed, and the other part is taken out from the top of the distillation column (T2).

[0014] (3) In the rectification column (T3), the separation of methanol is achieved. A part of the bottom stream of the rectification column (T3) is returned to the rectification column (T3) after heat exchange in the reboiler (H3). The bottom stream is introduced into the rectification columns (T1) and (T2) through the condenser (COL). Methanol is condensed by the condenser (CL3) and then enters the top storage tank (C3). A part of it is refluxed, and the other part is withdrawn from the top of the rectification column (T3).

[0015] According to another preferred embodiment of the present invention, it is characterized in that: the operating pressure of the rectification column (T1) is 1 atm, and the number of theoretical plates is 106 - 108; the operating pressure of the rectification column (T2) is 1 atm, and the number of theoretical plates is 64 - 66; the operating pressure of the rectification column (T3) is 1 atm, and the number of theoretical plates is 9 - 11. The feeding temperature of the extractant is 50 °C.

[0016] According to another preferred embodiment of the present invention, it is characterized in that in the mixed solution of acetone, methanol, and dichloromethane, the mole fraction of acetone is 30% - 35%, the mole fraction of methanol is 5% - 10%, and the mole fraction of dichloromethane is 55% - 60%.

[0017] According to another preferred embodiment of the present invention, it is characterized in that: by adopting this process flow, an efficient separation of the azeotropic system can be achieved. The purity of the separated acetone is greater than 99.93% (mole fraction), the purity of methanol is greater than 99.92% (mole fraction), the purity of dichloromethane is greater than 99.97% (mole fraction), and the purity of the recycled mixed extractant is greater than 99.99% (mole fraction).

[0018] [Advantageous Effects]

[0019] The present invention has the following advantageous effects:

[0020] (1) The advantageous effect of the present invention is to achieve an efficient separation of the ternary mixture of acetone, methanol, and dichloromethane by extractive distillation using a mixed extractant.

[0021] (2) The designed process can effectively achieve an efficient separation of the azeotrope.

[0022] (3) The process flow designed by the present invention has good separation effect, is economical, environmentally friendly, has a simple process, and is flexible in operation.

Description of the Drawings

[0023] Attached Figure 1 It is a schematic diagram of the method for extractive rectification separation of acetone, methanol, and dichloromethane using a mixed extractant.

[0024] In the figure, T1 - rectification column; T2 - rectification column; T3 - rectification column; CL1 - condenser; CL2 - condenser; CL3 - condenser; COL - condenser; H1 - reboiler; H2 - reboiler; H2 - reboiler; C1 - overhead storage tank; C2 - overhead storage tank; C3 - overhead storage tank; The numbers represent each material flow.

Detailed implementation manners

[0025] The following is further described in conjunction with the accompanying drawings, which does not limit the scope involved in the present invention.

[0026] Example 1:

[0027] The feed flow rate is 100 kmol / h, the feed temperature is 50 °C, the pressure is 1 atm (absolute pressure), and the mole fractions of acetone, methanol, and dichloromethane in the feed stream are 34.2%, 8.6%, and 57.2% respectively. The operating pressure of the rectification column (T1) is 1 atm (absolute pressure), the feed flow rate of the mixed extractant is 26 kmol / h, the feed temperature is 50 °C, the pressure is 2 atm (absolute pressure), the number of trays is 107, and the feed positions are the 3rd tray and the 38th tray respectively. The overhead temperature is 39.66 °C, and the bottom temperature is 66.34 °C; The operating pressure of the rectification column (T2) is 1 atm (absolute pressure), the feed flow rate of the mixed extractant is 36 kmol / h, the feed temperature is 50 °C, the pressure is 2 atm (absolute pressure), the number of trays is 65, and the feed positions are the 4th tray and the 49th tray respectively. The overhead temperature is 56.12 °C, and the bottom temperature is 135.13 °C; After separation, the concentration of the acetone product is greater than 99.93%, the concentration of the methanol product is greater than 99.96%, and the concentration of the dichloromethane product is greater than 99.97%.

[0028] Example 2:

[0029] The feed flow rate is 100 kmol / h, the feed temperature is 50 °C, the pressure is 1 atm (absolute pressure), and the mole fractions of acetone, methanol, and dichloromethane in the feed stream are 34.2%, 8.6%, and 57.2% respectively. The operating pressure of the rectification column (T1) is 1 atm (absolute pressure), the feed flow rate of the mixed extractant is 140 kmol / h, the feed temperature is 50 °C, the pressure is 2 atm (absolute pressure), the number of trays is 50, and the feed positions are the 13th tray and the 18th tray respectively. The overhead temperature is 39.65 °C, and the bottom temperature is 77.86 °C; The operating pressure of the rectification column (T2) is 1 atm (absolute pressure), the feed flow rate of the mixed extractant is 50 kmol / h, the feed temperature is 50 °C, the pressure is 2 atm (absolute pressure), the number of trays is 40, and the feed positions are the 4th tray and the 32nd tray respectively. The overhead temperature is 56.13 °C, and the bottom temperature is 165.03 °C; After separation, the concentration of the acetone product is greater than 99.98%, the concentration of the methanol product is greater than 99.92%, and the concentration of the dichloromethane product is greater than 99.98%.

Claims

1. A method for separating acetone, methanol and dichloromethane by extractive distillation using a mixed extractant, characterized in that The device for implementing the method mainly includes the following parts: Rectification tower (T1), rectification tower (T2), rectification tower (T3), condenser (COL), tower top storage tank (C1), tower top storage tank (C2), tower top storage tank (C3), reboiler (H1), reboiler (H2), reboiler (H3), condenser (CL1), condenser (CL2), condenser (CL3); wherein the bottom of rectification tower T1 enters rectification tower T2 through a pipeline; the bottom of rectification tower T2 enters rectification tower T3 through a pipeline; the extractant at the bottom of rectification tower T3 is recovered to rectification tower T1 and rectification tower T2 through condenser COL, and the components to be separated enter through the bottom of rectification tower T1; The above device is used to carry out a method for extracting and distilling acetone, methanol and dichloromethane using a mixed extractant: (1) A mixture of acetone, methanol and dichloromethane enters from the bottom of distillation tower T1, and a mixed extractant enters from the top of distillation tower T1. After effective contact extraction and separation, dichloromethane flows out from the top of distillation tower T1, and acetone, methanol and the mixed extractant flow out from the bottom of distillation tower T1 and enter distillation tower T2; (2) After a second separation in distillation tower T2, acetone is produced from the top of tower T2, and methanol and mixed extractant flow out from the bottom of distillation tower T2 and enter distillation tower T3; (3) A third separation is performed in the distillation tower T3, methanol is produced from the top of the tower T3, and the mixed extractant flows out from the bottom of the tower T3. The mixed extractant enters the cooler COL for cooling, and then enters the distillation tower T1 and the distillation tower T2 for recycling; The mixed extractant is a mixed solution of glycerol and 1,3-propylene glycol (1.8 wt % glycerol, 98.2 wt % 1,3-propylene glycol).

2. The method for separating acetone, methanol and dichloromethane by extractive distillation using a mixed extractant according to claim 1, characterized in that: The operating pressure of the distillation tower (T1) is 1 atm, and the number of theoretical plates is 106-108; the operating pressure of the distillation tower (T2) is 1 atm, and the number of theoretical plates is 64-66; the operating pressure of the distillation tower (T3) is 1 atm, and the number of theoretical plates is 9-11. The feed temperature of the extractant is 50°C.

3. The method for separating acetone, methanol and dichloromethane by extractive distillation using a mixed extractant according to claim 1, characterized in that: In the acetone, methanol and dichloromethane mixed liquid, the molar fraction of acetone is 30% to 35%, the molar fraction of methanol is 5% to 10%, and the molar fraction of dichloromethane is 55% to 60%.

4. The method for separating acetone, methanol and dichloromethane by extractive distillation using a mixed extractant according to claim 1, characterized in that: The purity of the separated acetone is greater than 99.93% (molar fraction), the purity of the methanol is greater than 99.92% (molar fraction), the purity of the dichloromethane is greater than 99.97% (molar fraction), and the purity of the recycled mixed extractant is greater than 99.99% (molar fraction).

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