CN-121971870-A - Separation system and separation method of methylene dichloride, ethanol and methanol aqueous solution multielement azeotropic system

CN121971870ACN 121971870 ACN121971870 ACN 121971870ACN-121971870-A

Abstract

The invention discloses a separation system and a separation method of a multi-element azeotropic system of methylene dichloride, ethanol and methanol aqueous solution, wherein the separation system comprises three stages of rectifying towers which are connected in series, a reflux pipeline with a condenser is connected to the top extraction port of each stage of rectifying tower, a mixer for mixing the top extraction of the first stage of rectifying tower with water and a phase separator for separating oil from water in the mixer are also connected to the reflux pipeline corresponding to the first stage of rectifying tower, the water phase outlet of the phase separator and the top extraction port of the first stage of rectifying tower are respectively connected with the feed inlet of a second stage of rectifying tower, the side line of the second stage of rectifying tower is provided with a methanol extraction port, the bottom extraction port of the second stage of rectifying tower is connected with the feed inlet of a third stage of rectifying tower, and the top extraction port of the third stage of rectifying tower is connected with a device for separating ethanol and water. The method can effectively separate the multi-element azeotropic system of the methylene dichloride, the ethanol and the methanol aqueous solution, and the obtained methylene dichloride, ethanol and methanol products have high purity.

Inventors

Jian Junqi
LIAO HENGJIAN
Chang Xuyao
HE FAN
Gou Junheng

Assignees

中国电子系统工程第二建设有限公司

Dates

Publication Date: 20260505
Application Date: 20251231

Claims (10)

1. A separation system of a multi-element azeotropic system of methylene dichloride, ethanol and methanol aqueous solution is characterized by comprising three stages of rectifying towers which are connected in series, wherein a reflux pipeline with a condenser is connected to a tower top extraction port of each stage of rectifying tower, a mixer for mixing the tower top extraction product of the first stage of rectifying tower with water and a phase separator for separating oil from water in the mixer are also connected to the reflux pipeline corresponding to the first stage of rectifying tower, a water phase outlet of the phase separator and a tower bottom extraction port of the first stage of rectifying tower are respectively connected with a feed inlet of a second stage of rectifying tower, a methanol extraction port is arranged on a side line of the second stage of rectifying tower, a tower bottom extraction port of the second stage of rectifying tower is connected with a feed inlet of a third stage of rectifying tower, and a device for separating ethanol and water is connected to the tower top extraction port of the third stage of rectifying tower.
2. The separation system according to claim 1, wherein the first-stage rectifying column has a tray number of not less than 23 trays, the second-stage rectifying column has a tray number of not less than 65 trays, and the third-stage rectifying column has a tray number of not less than 20 trays.
3. The separation system of claim 1, wherein each rectifying tower kettle extraction port is connected with a tower kettle extraction pump and a tower kettle circulating pump, a reboiler is arranged on a connecting pipeline provided with the tower kettle circulating pump, and the connecting pipeline provided with the tower kettle extraction pump is connected with the next rectifying tower.
4. The separation system according to claim 1, wherein the means for separating ethanol and water comprises a membrane separation device.
5. A method of separating a multiple azeotropic system based on a separation system according to claim 1, comprising the steps of: (1) The multi-element azeotropic system enters a first-stage rectifying tower, the tower top extract is cooled and refluxed by a first-stage rectifying tower top condenser, and then the tower top extract and water of the first-stage rectifying tower enter a mixer to be fully mixed, and then enter a phase separator to carry out oil-water phase separation, wherein an oil phase is a dichloromethane product, and a water phase is water, methanol and ethanol; (2) Feeding the materials extracted from the tower bottom of the first-stage rectifying tower and the water phase separated by the phase separator into a second-stage rectifying tower, extracting methanol from the middle side line of the tower, and cooling to obtain a methanol product, wherein the extract of the tower bottom is a mixture of ethanol and water; (3) The materials extracted from the tower bottom of the second-stage rectifying tower enter a third-stage rectifying tower, the materials extracted from the tower top of the third-stage rectifying tower are azeotropes of ethanol and water, the azeotropes enter a device for separating ethanol and water, an ethanol product and a water phase are obtained, the materials extracted from the tower bottom of the third-stage rectifying tower are water, and the water can be reused as a water phase raw material of a phase separator.
6. The separation method according to claim 5, wherein in the step (1), the raw material enters the first-stage rectifying tower from the 12 th column plate, the flow rate of the overhead of the first-stage rectifying tower is 32.5-42.5% of the feeding amount of the raw material, and the reflux ratio of the overhead is 1.
7. The separation method according to claim 5, wherein in the step (2), the flow ratio of the material extracted from the first-stage rectifying tower kettle to the water phase of the phase separator is 2-3:1, and the material extracted from the first-stage rectifying tower kettle and the water phase of the phase separator enter the second-stage rectifying tower from the 55 th tower plate and the 50 th tower plate respectively.
8. The separation method according to claim 5, wherein in the step (2), the side offtake plate of the second-stage rectifying tower is a 10 th tray, and the flow ratio of the feed flow rate of the raw material of the second-stage rectifying tower to the flow rate of the side offtake is 2.9-3.8:1.
9. The separation method according to claim 5, wherein in the step (3), the material extracted from the bottom of the second-stage rectifying tower enters the third-stage rectifying tower from a 12 th tower plate, and the flow ratio of the material feeding flow of the third-stage rectifying tower to the material flow of the top distillate is 1.4-2.5:1.
10. The separation process according to claim 5, wherein in step (3), the reflux ratio of the overhead product is 2.

Description

Separation system and separation method of methylene dichloride, ethanol and methanol aqueous solution multielement azeotropic system Technical Field The invention relates to a separation system of a multi-element azeotropic system of methylene dichloride, ethanol and methanol aqueous solution, and also relates to a multi-element azeotropic system separation method based on the separation system. Background In the synthesis, extraction, concentration, crystallization and other processes of fine chemicals such as chemical raw materials and pesticides, solvents such as ethanol, methanol, methylene dichloride and the like are usually required, so that a multi-component mixed solution is often formed in the final reaction waste liquid. Because the different solvents used may have azeotropy, they cannot be effectively separated and recovered by conventional rectification. The current mode of treating multiple azeotropic systems in the fine chemical industry is usually batch distillation. The batch distillation is to separate effectively according to the boiling point difference of each component in the mixed system, and collect the fractions of different stages, such as front fraction, transition fraction, main fraction, etc. by fractional distillation to obtain corresponding single or multiple products. For a non-azeotropic system or a simple azeotropic system, the batch distillation can effectively obtain a product, but for a multicomponent multiple azeotropic system (such as a mixed solution of dichloromethane, ethanol, methanol and water, the azeotropy of water and ethanol, the azeotropy of methanol and dichloromethane, the azeotropy of ethanol and dichloromethane, the heterogeneous azeotropy of methanol, water and dichloromethane and the like) only one or a part of the product can be obtained, and the quality and the yield of the obtained product are not high due to the change of the composition in a tower along with the time and the existence of transition fractions among fractional distillation products at each stage. Therefore, the prior art has the problems of low product purity and low recovery rate when the batch rectification is adopted to separate the multi-component multi-azeotropic system. Disclosure of Invention The invention aims to provide a separation system capable of effectively separating a multi-element azeotropic system of methylene dichloride, ethanol and methanol aqueous solution, which realizes azeotropic separation of all-component products and has high purity of the obtained methylene dichloride, ethanol and methanol products, and the invention also aims to provide a multi-element azeotropic system separation method of the separation system. The separating system of the multi-element azeotropic system of the methylene dichloride, the ethanol and the methanol aqueous solution comprises three stages of rectifying towers which are connected in series, wherein a reflux pipeline with a condenser is connected to the top extraction port of each stage of rectifying tower, a mixer for mixing the top extraction of the first stage of rectifying tower with water and a phase separator for separating oil from water in the mixer are also connected to the reflux pipeline corresponding to the first stage of rectifying tower, the water phase outlet of the phase separator and the top extraction port of the first stage of rectifying tower are respectively connected with the feed inlet of a second stage of rectifying tower, the side line of the second stage of rectifying tower is provided with the methanol extraction port, the top extraction port of the second stage of rectifying tower is connected with the feed inlet of a third stage of rectifying tower, and the top extraction port of the third stage of rectifying tower is connected with a device for separating ethanol and water. The number of the tower plates of the first-stage rectifying tower is not less than 23, the number of the tower plates of the second-stage rectifying tower is not less than 65, and the number of the tower plates of the third-stage rectifying tower is not less than 20. And each stage of rectifying tower kettle extraction port is connected with a tower kettle extraction pump and a tower kettle circulating pump, a reboiler (the reboiler is used as a heat source of the rectifying tower and heats materials in the rectifying tower to evaporate) is further arranged on a connecting pipeline provided with the tower kettle extraction pump and connected with the next stage of rectifying tower or connected with a mixer. The membrane separation device of the device for separating ethanol and water adopts ‌ pervaporation membrane technology to ‌ separate ethanol and water. The multi-element azeotropic system separation method based on the separation system comprises the following steps: (1) The multi-element azeotropic system (methylene dichloride, ethanol, methanol and water) is taken as raw materials to enter a first-stage rectifying tower