Chloroform / ethanol / water system extraction pressure swing distillation process for comprehensive utilization of latent and sensible heat

Abstract

The invention discloses a chloroform / ethanol / water system extraction variable-pressure rectification process for comprehensive utilization of latent and sensible heat, which realizes efficient and comprehensive utilization of energy through three-tower operation of an extraction reduced-pressure rectification tower T1, an extraction rectification tower T2 and a solvent recovery reduced-pressure rectification tower T3. The tower top steam of the extractive distillation tower T2 is used for heating the tower bottom liquid of the extractive decompression distillation tower T1 to vaporize the tower bottom liquid, and meanwhile, the tower top steam of the solvent recovery decompression distillation tower T3 is used for carrying out heat exchange on part of the liquid phase of the middle plate of the extractive decompression distillation tower T1; the problem that the tower top temperature of the solvent recovery vacuum distillation tower T3 is between the tower top temperature of the extraction vacuum distillation tower T1 and the tower kettle temperature, and traditional heat integration cannot be achieved is solved, and latent heat utilization is achieved. In addition, the tower kettle liquid of the solvent recovery vacuum distillation tower T3 is used for heating the tower kettle liquid of the extraction distillation tower T2 and the extraction vacuum distillation tower T1, and sensible heat utilization is achieved. According to the process, heat energy is fully utilized, energy consumption is reduced, the purity and yield of chloroform, ethanol and water are improved, and the equipment cost is reduced. And the adopted extracting agent is small in dosage, relatively weak in volatility, small in loss, easy to recover and environment-friendly.

Description

Technical Field

[0001] This invention belongs to the field of chemical separation and purification, specifically involving a chloroform / ethanol / water system extraction and pressure swing distillation process that utilizes both latent and sensible heat. Background Technology

[0002] Chloroform is an important raw material and efficient solvent for organic synthesis, widely used in the synthesis of refrigerants, fluorinated polymers, and pharmaceutical products. It also has excellent solubility for oils, resins, and rubbers, making it commonly used in extraction, cleaning, and chemical production processes. Ethanol, a versatile basic chemical, is an indispensable raw material and additive in the pharmaceutical, cosmetic, and food industries. High-purity ethanol can also be used directly as a clean biofuel, helping to reduce dependence on traditional fossil fuels. Water is a crucial basic substance and industrial medium, serving as a solvent for many chemical reactions and crystallization processes, and is widely used in cooling, heating, and cleaning. In the electronics, pharmaceutical, and fine chemical industries, high-purity water is an indispensable raw material, its purity directly affecting the quality of the final product.

[0003] A mixture of chloroform, ethanol, and water forms three binary azeotropic mixtures and one ternary azeotropic mixture. At 1 atm, the chloroform-ethanol azeotropic point is 59.3℃, the chloroform-water azeotropic point is 56.1℃, the ethanol-water azeotropic point is 78.2℃, and the chloroform-ethanol-water azeotropic point is 55.5℃. Ordinary distillation methods cannot achieve effective separation, thus requiring a special distillation method. This invention not only achieves effective separation of this azeotropic system but also has lower cost and gas emissions, achieving a triple benefit in terms of technology, economy, and environmental protection.

[0004] Patent (CN223351042U) discloses a method and apparatus for separating a mixture of ethyl acetate and cyclohexane. This method achieves large-scale separation by adding a polar polyol to alter the relative volatility of the two components. Alternatively, cyclohexane containing a small amount of ethyl acetate is placed in an alkaline environment, utilizing the difference in solubility of cyclohexane, sodium acetate, and ethanol in water to improve the separation efficiency. However, this process is cumbersome, generates wastewater pollution, and increases equipment costs and workload.

[0005] Patent (CN120736955A) discloses a method for the production of polyglycol by reactive distillation of a ternary aqueous azeotropic system coupled with polyglycol production. This method achieves ethylene oxide recycling, organic component separation, and polyglycol production through a three-step integrated process. However, it does not integrate the heat during the separation process, resulting in low heat utilization.

[0006] This invention utilizes an extraction-pressure swing distillation method that combines latent and sensible heat. By leveraging the characteristics of the extractant and pressure changes affecting the relative volatility and azeotropic composition of the azeotropic system, it achieves high-purity separation and recovery of chloroform-ethanol-water azeotropic mixtures. Furthermore, the synergistic heat exchange of latent and sensible heat significantly reduces process energy consumption. This method can achieve purities of over 99.9% for chloroform, ethanol, and water, and allows for the recovery and reuse of high-purity extractants. This invention fully utilizes process heat, reduces energy consumption, improves the purity and yield of chloroform, ethanol, and water, and lowers equipment costs. The extracted agent used is present in small quantities, has low volatility, minimal loss, is easy to recover, and is environmentally friendly. Summary of the Invention

[0007] [Technical problem to be solved] The purpose of this invention is to provide a pressure swing distillation process for the extraction of a chloroform / ethanol / water system that comprehensively utilizes latent and sensible heat. By leveraging the coupled influence mechanism of extractant and pressure on the separation of the chloroform-ethanol-water azeotropic system, a significant reduction in process energy consumption can be achieved while obtaining a high-purity product.

[0008] [Technical Solution]

[0009] This invention overcomes the shortcomings of existing technologies and proposes a method for separating chloroform / ethanol / water azeotropic systems using extraction pressure swing distillation with comprehensive utilization of latent and sensible heat. This invention utilizes the characteristics of the extractant and pressure changes affecting the relative volatility and azeotropic composition of the azeotropic system, respectively. It employs a three-tower distillation method (extraction distillation column T1, extraction distillation column T2, and solvent recovery distillation column T3) to separate high-purity chloroform, ethanol, and water. The comprehensive utilization of latent and sensible heat significantly reduces energy consumption. This method solves the problems of complex processes, large extractant usage, high energy consumption, and high equipment costs in current technologies, and improves product purity.

[0010] This invention provides a method for separating a chloroform-ethanol-water azeotropic system with a raw material feed rate of 80 kmol / h-120 kmol / h, comprising chloroform molar fraction of 32%-48%, ethanol molar fraction of 24%-36%, and water molar fraction of 24%-36%.

[0011] This invention is achieved through the following technical solution: a chloroform / ethanol / water system extraction pressure swing distillation process utilizing both latent and sensible heat, characterized in that the apparatus for implementing this method mainly comprises the following parts: Extraction distillation column T1, extraction distillation column T2, solvent recovery distillation column T3, condenser C1, condenser C2, condenser C3, cooler H, reboiler R1, reboiler R2, heat exchanger E1, heat exchanger E2, heat exchanger E3, heat exchanger E4, mixer FS, centrifugal pump P1, centrifugal pump P2, centrifugal pump P3; A pressure swing distillation process for an extractive system of chloroform / ethanol / water based on the comprehensive utilization of latent and sensible heat, using the above-mentioned apparatus, includes the following steps: (1) The raw material chloroform / ethanol / water mixture enters from the middle of the extraction vacuum distillation column T1, and the extractant enters from the top of the extraction vacuum distillation column T1. After effective contact separation, the gas phase at the top of the extraction vacuum distillation column T1 passes through the condenser C1. Part of it is returned to the extraction vacuum distillation column T1, and part of it is used to collect high-purity chloroform. Part of the ethanol-water-extractant mixture at the bottom of the column passes through the heat exchanger E2 and exchanges heat with the gas phase at the top of the extraction distillation column T2. ​​Then it passes through the heat exchanger E4 and exchanges heat with the liquid phase at the bottom of the solvent recovery vacuum distillation column T3 before returning to the bottom of the column. The other part is sent to the extraction distillation column T2 by the centrifugal pump P1. Part of the liquid phase in the middle section of the extraction vacuum distillation column T1 enters the heat exchanger E1 and exchanges heat before returning to the extraction vacuum distillation column T1. (2) The ethanol-water-extractant mixture enters from the middle of the extractive distillation column T2, and the extractant enters from the top of the extractive distillation column T2. ​​The vapor phase at the top of the extractive distillation column T2 enters the heat exchanger E2 and exchanges heat with the extractive vacuum distillation column T1. After the heat exchange, the stream enters the condenser C2. Part of it is returned to the extractive distillation column T2, and part of it is used to collect high-purity product ethanol. Part of the water-extractant mixture at the bottom of the column exchanges heat with the liquid phase at the bottom of the solvent recovery vacuum distillation column T3 through the heat exchanger E3 and returns to the bottom of the column. The other part is sent to the solvent recovery vacuum distillation column T3 by the centrifugal pump P2. (3) The water-extractant mixture enters from the middle of the solvent recovery vacuum distillation column T3. The gas phase at the top of the solvent recovery vacuum distillation column T3 enters the heat exchanger E1 to exchange heat with the liquid phase in the middle section of the extraction vacuum distillation column T1. After heat exchange, the stream enters the condenser C3. Part of it flows back to the solvent recovery vacuum distillation column T3, and part of it is used to collect high-purity product water. The stream at the bottom of the solvent recovery vacuum distillation column T3 is used to collect high-purity extractant. It enters the heat exchanger E3 to exchange heat with the liquid phase at the bottom of the extraction distillation column T2. ​​Then it enters the heat exchanger E4 to exchange heat with the liquid phase at the bottom of the extraction vacuum distillation column T1. After heat exchange, the stream enters the cooler H through the centrifugal pump P3. After cooling, it is mixed with the supplementary extractant in the mixer FS and then flows back to the extraction vacuum distillation column T1 and the extraction distillation column T2. The operating pressure of the extraction vacuum distillation column T1 is 0.085 atm to 0.115 atm, with 36 trays. The feed is on the 24th tray, the extractant is on the 4th tray, the top temperature is 1.0℃ to 8.0℃, and the bottom temperature is 53.0℃ to 60.0℃. The operating pressure of the extractive distillation column T2 is 0.4 atm to 1.2 atm, with 34 trays. The ethanol-water-extractant mixture is fed onto the 24th tray, the extractant is fed onto the 5th tray, the top temperature is 57.0℃ to 83.0℃, and the bottom temperature is 128.0℃ to 135.0℃. The solvent recovery vacuum distillation column T3 operates at a pressure of 0.05 atm to 0.15 atm, has 6 trays, feeds the water-extractant mixture onto the 3rd tray, has a top temperature of 33.0℃ to 55.0℃, and a bottom temperature of 196.0℃ to 226.0℃.

[0012] According to another preferred embodiment of the present invention, the intermediate heat exchange plate of the extractive distillation column T1 is located at plate number 29-31, the heat exchange liquid flow rate is 30-34 kmol / h, the temperature of the heat exchange stream in the intermediate plate is 22.0℃~26.0℃, and the temperature after heat exchange is 32.0℃~35.0℃. The temperature of the vapor phase entering heat exchanger E2 from the top of the extractive distillation column T2 is 70.0℃~77.0℃, and the temperature after heat exchange in heat exchanger E2 is 52.0℃~59.0℃, with a vapor fraction of 27.0%~34.0%.

[0013] According to another preferred embodiment of the present invention, the temperature of the bottom stream of the solvent recovery vacuum distillation column T3 entering the heat exchanger E3 is 196.0℃~226.0℃, the temperature after heat exchange in heat exchanger E3 is 110.0℃~117.0℃, and the vapor phase fraction is 0; the temperature after heat exchange in heat exchanger E4 is 58.0℃~65.0℃, and the vapor phase fraction is 0.

[0014] According to another preferred embodiment of the present invention, the chloroform after separation has a purity greater than 99.9% and a yield greater than 99.9%, the ethanol has a purity greater than 99.9% and a yield greater than 99.9%, the water has a purity greater than 99.9% and a yield greater than 99.9%, and the extractant has a purity greater than 99.99% and a yield greater than 99.99%.

[0015] According to another preferred embodiment of the present invention, the extractant is selected from glycerol, ethylene glycol, 1,4-butanediol, dimethyl sulfoxide, dimethylacetamide, N-methylpyrrolidone, and ethyl acetate.

[0016] The method for separating the chloroform / ethanol / water azeotropic system by extraction pressure swing distillation using latent heat and sensible heat synergistic heat exchange according to the present invention is described in detail below: The chloroform-ethanol-water mixture and the extractant enter the extractive vacuum distillation column T1 from the 24th and 4th plates, respectively. After effective contact separation, the vapor phase at the top of column T1 passes through condenser C1, with part of it refluxed back to column T1 and part collected as high-purity chloroform. The liquid phase at the bottom, the ethanol-water-extractant mixture, partially exchanges heat with the vapor phase at the top of column T2 through heat exchanger E2, and then passes through heat exchanger E4 for solvent recovery vacuum distillation. After heat exchange in column T3, the liquid returns to the bottom of the column. Another portion enters the extractive distillation column T2 via centrifugal pump P1 from the 24th plate. A portion of the liquid phase from the middle plate of extractive distillation column T1 enters heat exchanger E1 for heat exchange and then flows back to extractive distillation column T1. In extractive distillation column T2, the extractant enters from the top. The vapor phase from the top of extractive distillation column T2 enters heat exchanger E2 and exchanges heat with extractive distillation column T1. The stream after heat exchange enters condenser C2, with a portion flowing back. At extractive distillation column T2, a portion of the high-purity product ethanol is collected. The bottom liquid phase, a water-extractant mixture, is partially returned to the bottom of the column after heat exchange with the solvent recovery vacuum distillation column T3 via heat exchanger E3. The other portion enters the column via centrifugal pump P2 from the third plate of the solvent recovery vacuum distillation column T3. In the solvent recovery vacuum distillation column T3, the top vapor phase enters heat exchanger E1 and exchanges heat with a portion of the liquid phase in the middle plate of the solvent recovery extractive vacuum distillation column T1 before entering condenser C3. A portion of this vapor phase is then returned to the bottom of the column. The liquid flows to the solvent recovery vacuum distillation column T3, where a portion is high-purity product water. The high-purity extractant is collected from the bottom of the solvent recovery vacuum distillation column T3 and enters heat exchanger E3 to exchange heat with the liquid phase at the bottom of the extractive distillation column T2. ​​It then enters heat exchanger E4 to exchange heat with the liquid phase at the bottom of the extractive vacuum distillation column T1. After heat exchange, the stream passes through centrifugal pump P3 and enters cooler H. After cooling, it is mixed with the supplementary extractant in mixer FS and then refluxed to extractive vacuum distillation columns T1 and T2.

[0017] In this invention, the operating pressure of the extractive distillation column T1 is 0.085~0.115 atm, with 36 trays. The chloroform-ethanol-water mixture is fed onto the 24th tray, and the extractant is fed onto the 4th tray. The top temperature is 1.0℃~8.0℃, and the bottom temperature is 53.0℃~60.0℃. The operating pressure of the extractive distillation column T2 is 0.4 atm~1.2 atm, with 34 trays. The ethanol-water-extractant mixture... The feed position for the solvent recovery distillation column T3 is on the 24th tray, the feed position for the extractant is on the 5th tray, the top temperature is 56.0℃~83.0℃, and the bottom temperature is 128.0℃~135.0℃. The operating pressure of the solvent recovery vacuum distillation column T3 is 0.05atm~0.15atm, the number of trays is 6, the feed position for the water-extractant mixture is on the 3rd tray, the top temperature is 33.0℃~54.0℃, and the bottom temperature is 196.0℃~226.0℃.

[0018] The chloroform separated using this method has a purity greater than 99.9% and a yield greater than 99.9%, the ethanol has a purity greater than 99.9% and a yield greater than 99.9%, and the water has a purity greater than 99.9% and a yield greater than 99.9%.

[0019] [Beneficial Effects]

[0020] Compared with the prior art, the present invention has the following advantages: (1) The purity of chloroform, ethanol and water separated by latent heat-sensible heat synergistic heat exchange extraction and pressure swing distillation method is improved.

[0021] (2) The latent heat of the gas phase at the top of the solvent recovery vacuum distillation column T3 can heat the liquid phase in the middle plate of the extraction vacuum distillation column T1, and the latent heat of the gas phase at the top of the extraction distillation column T2 can heat the bottom stream of the extraction vacuum distillation column T1; the sensible heat of the bottom stream of the solvent recovery vacuum distillation column T3 can heat the bottom streams of the extraction vacuum distillation column T1 and the extraction distillation column T2, thereby reducing energy consumption.

[0022] (3) The amount of extractant used is small, the equipment investment is small, the extractant used is easy to recover, has good chemical and thermal stability, and is green and pollution-free. Attached Figure Description

[0023] Appendix Figure 1 This is a schematic diagram of a method for separating a chloroform-ethanol-water azeotropic system using thermal integrated extraction and pressure swing distillation.

[0024] In the diagram, T1 is the extraction distillation column, T2 is the extraction distillation column, T3 is the solvent recovery distillation column, C1 is the condenser, C2 is the condenser, C3 is the condenser, H is the cooler, R1 is the reboiler, R2 is the reboiler, E1 is the heat exchanger, E2 is the heat exchanger, E3 is the heat exchanger, E4 is the heat exchanger, FS is the mixer, P1 is the centrifugal pump, P2 is the centrifugal pump, and P3 is the centrifugal pump. Detailed Implementation

[0025] The following description, in conjunction with the accompanying drawings, is intended to further illustrate the scope of the invention but is not intended to limit its scope.

[0026] Example 1:

[0027] The feed flow rate is 100 kmol / h, containing 40% chloroform, 30% ethanol, and 30% water (mole fraction). The extractive vacuum distillation column T1 has 36 theoretical plates and a pressure of 0.1 atm. The chloroform-ethanol-water mixture enters from the 24th plate of column T1, while the extractant enters from the 4th plate at a flow rate of 12 kmol / h. The intermediate heat exchange plate is the 30th plate, with a heat exchange flow rate of 32 kmol / h. The temperature entering heat exchanger E1 is 23.6℃ with a vapor fraction of 0%, and the temperature after heat exchange in heat exchanger E1 is 32.9℃ with a vapor fraction of 39.5%. The extractive distillation column T1 yields chloroform with a purity greater than 99.9% at the top, with a yield greater than 99.9% and a temperature of 4.8℃. The bottom stream is divided into two parts. One part enters heat exchanger E2 at a temperature of 54.3℃ with a vapor fraction of 0. After heat exchange in E2, the temperature is 55.9℃ with a vapor fraction of 30.9%, and then it enters heat exchanger E4. After heat exchange in E4, the temperature is 56.3℃ with a vapor fraction of 33.6%, and it returns to the bottom. The other part enters from the 24th plate of extractive distillation column T2 at a temperature of 56.8℃. The theoretical number of plates in extractive distillation column T2 is 34, and the pressure is 0.8 atm. The vapor temperature at the top of extractive distillation column T2 is 72.9℃, entering heat exchanger E2 at 73.2℃ with a vapor fraction of 100%. After heat exchange in heat exchanger E2, the temperature is 73.1℃ with a vapor fraction of 0%. This vapor then enters condenser C2; part of it is refluxed back to extractive distillation column T2, and the other part is collected to obtain ethanol with a purity greater than 99.9% and a yield greater than 99.9%. The bottom stream, a water-extractant mixture, enters from the third plate of solvent recovery vacuum distillation column T3 at a temperature of 131.5℃. Solvent recovery vacuum distillation column T3 theoretically has 6 plates and a pressure of 0.1 atm. The vapor temperature at the top of the solvent recovery vacuum distillation column T3 is 54.3℃. The vapor entering heat exchanger E1 is also 54.3℃ with a vapor fraction of 100%. After heat exchange in heat exchanger E1, the temperature is 46.5℃ with a vapor fraction of 66.6%. A portion of this vapor then enters condenser C3 and is refluxed back to the solvent recovery vacuum distillation column T3, while the remaining portion is collected to obtain water with a purity greater than 99.9% and a yield greater than 99.9%. The bottom of the column yields an extractant with a purity greater than 99.99% and a yield greater than 99.9%, at a temperature of 221.1℃. The extractant enters the heat exchanger E3 at a temperature of 221.1℃ with a vapor fraction of 0. After heat exchange in heat exchanger E3, the temperature is 113.1℃ with a vapor fraction of 0. It then enters the condenser heat exchanger E4, where the temperature is 61.1℃ with a vapor fraction of 0. Finally, it enters the cooler H to be cooled to 25℃ and a small amount of extractant is added through the mixer FS before being refluxed back to the extractive distillation column T1.

[0028] Example 2:

[0029] The feed flow rate is 80 kmol / h, containing 32% chloroform, 34% ethanol, and 334% water (mole fraction). The extractive vacuum distillation column T1 has 36 theoretical plates and a pressure of 0.085 atm. The chloroform-ethanol-water mixture enters from the 24th plate of extractive vacuum distillation column T1, and the extractant enters from the 4th plate of extractive vacuum distillation column T1 at a flow rate of 10.5 kmol / h. The intermediate heat exchange plate is the 29th plate, with a heat exchange flow rate of 30 kmol / h. The temperature entering heat exchanger E1 is 22.7℃ with a vapor fraction of 0, and the temperature after heat exchange in heat exchanger E1 is 32.0℃ with a vapor fraction of 37.5%. The extractive distillation column T1 yields chloroform with a purity greater than 99.9% at the top, with a yield greater than 99.9% and a temperature of 1.7℃. The bottom stream is divided into two parts. One part enters heat exchanger E2 at a temperature of 53.7℃ with a vapor fraction of 0. After heat exchange in E2, the temperature drops to 54.2℃ with a vapor fraction of 30.9%, and then enters heat exchanger E4. After heat exchange in E4, the temperature drops to 54.3℃ with a vapor fraction of 33.6%, and the stream returns to the bottom. The other part enters from the 24th plate of extractive distillation column T2 at a temperature of 53.8℃. The theoretical number of plates in extractive distillation column T2 is 34, and the pressure is 0.4 atm. The vapor temperature at the top of extractive distillation column T2 is 56.7℃, entering heat exchanger E2 at 57.0℃ with a vapor fraction of 100%. After heat exchange in heat exchanger E2, the temperature is 57.1℃ with a vapor fraction of 0%. This vapor then enters condenser C2; part of it is refluxed back to extractive distillation column T2, and the other part is collected to obtain ethanol with a purity greater than 99.9% and a yield greater than 99.9%. The bottom stream, a water-extractant mixture, enters from the third plate of solvent recovery vacuum distillation column T3 at a temperature of 128.5℃. Solvent recovery vacuum distillation column T3 theoretically has 6 plates and a pressure of 0.05 atm. The vapor temperature at the top of the solvent recovery vacuum distillation column T3 is 33.3℃. The vapor temperature entering heat exchanger E1 is also 33.3℃, ​​with a vapor fraction of 100%. After heat exchange in heat exchanger E1, the temperature is 33.3℃, ​​and the vapor fraction is 66.6%. A portion of this vapor then enters condenser C3 and is refluxed back to the solvent recovery vacuum distillation column T3. The remaining portion is collected to obtain water with a purity greater than 99.9% and a yield greater than 99.9%. The bottom of the column yields an extractant with a purity greater than 99.99% and a yield greater than 99.9%, at a temperature of 196.6℃. The extractant enters heat exchanger E3 at a temperature of 196.6℃ with a vapor fraction of 0. After heat exchange in heat exchanger E3, the temperature is 109.3℃ with a vapor fraction of 0. It then enters condenser heat exchanger E4, where the temperature is 57.6℃ with a vapor fraction of 0. Finally, it enters cooler H to be cooled to 25℃ and a small amount of extractant is added through mixer FS before being refluxed to extractive distillation column T1.

[0030] Example 3:

[0031] The feed flow rate is 120 kmol / h, containing 48% chloroform, 26% ethanol, and 26% water (mole fraction). The extractive vacuum distillation column T1 has 36 theoretical plates and a pressure of 0.115 atm. The chloroform-ethanol-water mixture enters from the 24th plate of column T1, while the extractant enters from the 4th plate at a flow rate of 13.5 kmol / h. The intermediate heat exchange plate is the 31st plate, with a heat exchange flow rate of 34 kmol / h. The temperature entering heat exchanger E1 is 25.1℃ with a vapor fraction of 0, and the temperature after heat exchange in heat exchanger E1 is 34.4℃ with a vapor fraction of 37.5%. The extractive distillation column T1 yields chloroform with a purity greater than 99.9% at the top, with a yield greater than 99.9% and a temperature of 7.6℃. The bottom stream is divided into two parts. One part enters heat exchanger E2 at a temperature of 58.3℃ with a vapor fraction of 0. After heat exchange in E2, the temperature drops to 58.9℃ with a vapor fraction of 30.9%, and then enters heat exchanger E4. After heat exchange in E4, the temperature drops to 59.8℃ with a vapor fraction of 33.6%, and the stream returns to the bottom. The other part enters from the 24th plate of extractive distillation column T2 at a temperature of 59.8℃. The theoretical number of plates in extractive distillation column T2 is 34, and the pressure is 1.2 atm. The vapor temperature at the top of extractive distillation column T2 is 83.0℃, entering heat exchanger E2 at 76.2℃ with a vapor fraction of 100%. After heat exchange in heat exchanger E2, the temperature is 76.1℃ with a vapor fraction of 0%. This vapor then enters condenser C2; part of it is refluxed back to extractive distillation column T2, and the other part is collected to obtain ethanol with a purity greater than 99.9% and a yield greater than 99.9%. The bottom stream, a water-extractant mixture, enters from the third plate of solvent recovery vacuum distillation column T3 at a temperature of 134.5℃. Solvent recovery vacuum distillation column T3 theoretically has 6 plates and a pressure of 0.15 atm. The vapor temperature at the top of the solvent recovery vacuum distillation column T3 is 54.3℃. The vapor entering heat exchanger E1 is also 54.3℃ with a vapor fraction of 100%. After heat exchange in heat exchanger E1, the temperature is 50.5℃ with a vapor fraction of 66.6%. A portion of this vapor then enters condenser C3 and is refluxed back to the solvent recovery vacuum distillation column T3, while the remaining portion is collected to obtain water with a purity greater than 99.9% and a yield greater than 99.9%. At the bottom of the column, an extractant with a purity greater than 99.99% and a yield greater than 99.9% is obtained at a temperature of 225.1℃. The extractant enters heat exchanger E3 at a temperature of 225.1℃ with a vapor fraction of 0. After heat exchange in heat exchanger E3, the temperature is 116.1℃ with a vapor fraction of 0. It then enters condenser heat exchanger E4, where the temperature is 64.1℃ with a vapor fraction of 0. Finally, it enters cooler H to be cooled to 25℃ and a small amount of extractant is added through mixer FS before being refluxed to extractive distillation column T1.

Claims

1. A pressure swing distillation process for extraction using a chloroform / ethanol / water system that utilizes both latent and sensible heat, characterized in that... The apparatus for implementing this method mainly includes the following parts: Extraction distillation column T1, extraction distillation column T2, solvent recovery distillation column T3, condenser C1, condenser C2, condenser C3, cooler H, reboiler R1, reboiler R2, heat exchanger E1, heat exchanger E2, heat exchanger E3, heat exchanger E4, mixer FS, centrifugal pump P1, centrifugal pump P2, centrifugal pump P3; A pressure swing distillation process for an extractive system of chloroform / ethanol / water based on the comprehensive utilization of latent and sensible heat, using the above-mentioned apparatus, includes the following steps: (1) The raw material chloroform / ethanol / water mixture enters from the middle of the extraction vacuum distillation column T1, and the extractant enters from the top of the extraction vacuum distillation column T1. After effective contact separation, the gas phase at the top of the extraction vacuum distillation column T1 passes through the condenser C1. Part of it is returned to the extraction vacuum distillation column T1, and part of it is used to collect high-purity chloroform. Part of the ethanol-water-extractant mixture at the bottom of the column passes through the heat exchanger E2 and exchanges heat with the gas phase at the top of the extraction distillation column T2. ​​Then it passes through the heat exchanger E4 and exchanges heat with the liquid phase at the bottom of the solvent recovery vacuum distillation column T3 before returning to the bottom of the column. The other part is sent to the extraction distillation column T2 by the centrifugal pump P1. Part of the liquid phase in the middle section of the extraction vacuum distillation column T1 enters the heat exchanger E1 and exchanges heat before returning to the extraction vacuum distillation column T1. (2) The ethanol-water-extractant mixture enters from the middle of the extractive distillation column T2, and the extractant enters from the top of the extractive distillation column T2. ​​The vapor phase at the top of the extractive distillation column T2 enters the heat exchanger E2 and exchanges heat with the extractive vacuum distillation column T1. After the heat exchange, the stream enters the condenser C2. Part of it is returned to the extractive distillation column T2, and part of it is used to collect high-purity product ethanol. Part of the water-extractant mixture at the bottom of the column exchanges heat with the liquid phase at the bottom of the solvent recovery vacuum distillation column T3 through the heat exchanger E3 and returns to the bottom of the column. The other part is sent to the solvent recovery vacuum distillation column T3 by the centrifugal pump P2. (3) The water-extractant mixture enters from the middle of the solvent recovery vacuum distillation column T3. The gas phase at the top of the solvent recovery vacuum distillation column T3 enters the heat exchanger E1 to exchange heat with the liquid phase in the middle section of the extraction vacuum distillation column T1. After heat exchange, the stream enters the condenser C3. Part of it flows back to the solvent recovery vacuum distillation column T3, and part of it is used to collect high-purity product water. The stream at the bottom of the solvent recovery vacuum distillation column T3 is used to collect high-purity extractant. It enters the heat exchanger E3 to exchange heat with the liquid phase at the bottom of the extraction distillation column T2. ​​Then it enters the heat exchanger E4 to exchange heat with the liquid phase at the bottom of the extraction vacuum distillation column T1. After heat exchange, the stream enters the cooler H through the centrifugal pump P3. After cooling, it is mixed with the supplementary extractant in the mixer FS and then flows back to the extraction vacuum distillation column T1 and the extraction distillation column T2. The operating pressure of the extraction vacuum distillation column T1 is 0.085 atm to 0.115 atm, with 36 trays. The feed is on the 24th tray, the extractant is on the 4th tray, the top temperature is 1.0℃ to 8.0℃, and the bottom temperature is 53.0℃ to 60.0℃. The operating pressure of the extractive distillation column T2 is 0.4 atm to 1.2 atm, with 34 trays. The ethanol-water-extractant mixture is fed onto the 24th tray, the extractant is fed onto the 5th tray, the top temperature is 57.0℃ to 83.0℃, and the bottom temperature is 128.0℃ to 135.0℃. The solvent recovery vacuum distillation column T3 operates at a pressure of 0.05 atm to 0.15 atm, has 6 trays, feeds the water-extractant mixture onto the 3rd tray, has a top temperature of 33.0℃ to 55.0℃, and a bottom temperature of 196.0℃ to 226.0℃.

2. According to another preferred embodiment of the present invention, the following features are characterized in that: In the extractive distillation column T1, the intermediate heat exchange plate is located at plate 29-31, with a liquid flow rate of 30-34 kmol / h. The temperature of the heat exchange stream in the intermediate plate is 22.0℃~26.0℃, and the temperature after heat exchange is 32.0℃~35.0℃. In the extractive distillation column T2, the vapor phase from the top enters heat exchanger E2 at a temperature of 70.0℃~77.0℃, and the temperature after heat exchange in heat exchanger E2 is 52.0℃~59.0℃, with a vapor fraction of 27.0%~34.0%.

3. According to another preferred embodiment of the present invention, the following features are characterized in that: The temperature of the bottom stream of the solvent recovery vacuum distillation column T3 entering heat exchanger E3 is 196.0℃~226.0℃. After heat exchange in heat exchanger E3, the temperature is 110.0℃~117.0℃ with a vapor fraction of 0. After heat exchange in heat exchanger E4, the temperature is 58.0℃~65.0℃ with a vapor fraction of 0.

4. According to another preferred embodiment of the present invention, the following features are characterized in that: The purity of the separated chloroform was greater than 99.9%, and the yield was greater than 99.9%; the purity of the ethanol was greater than 99.9%, and the yield was greater than 99.9%; the purity of the water was greater than 99.9%, and the yield was greater than 99.9%; and the purity of the extractant was greater than 99.99%, and the yield was greater than 99.99%.

5. According to another preferred embodiment of the present invention, the following features are characterized in that: The extraction solvents selected were glycerol, ethylene glycol, 1,4-butanediol, dimethyl sulfoxide, dimethylacetamide, N-methylpyrrolidone, and ethyl acetate.

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