Energy-saving process for separating ethanol from water by coupling extraction rectification and pervaporation in ethylene glycol side draw

Abstract

The invention discloses an energy-saving process for separating ethanol from water by coupling extractive distillation and pervaporation in ethylene glycol side draw, and relates to the technical field of chemical separation and purification. Compared with a traditional distillation method, the pervaporation energy consumption is reduced by 30%-50%, high temperature and high pressure are not needed, and energy conservation and consumption reduction are achieved; the concentration of inhibitory components (such as butanol) in fermentation liquor is reduced through membrane separation, the overall yield is improved, and the inhibition effect is reduced; the method can be expanded to separation of other low-boiling-point substances (such as benzene-ethanol), the regulation and control range of process parameters (temperature and pressure) is wide, and the process is flexible; the equipment cost is reduced: three-component separation can be completed by a single tower, and the investment of double-tower equipment is reduced; energy consumption optimization: the energy consumption is reduced by accurately controlling the side line extraction position and the operation condition; impurities can be removed synchronously, and the product purity is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical separation and purification, and particularly relates to an energy-saving process for separating ethanol-water by extractive distillation-pervaporation coupling with side-line extraction of ethylene glycol. Background Technique

[0002] Ethylene glycol is also known as "glycol", "1,2-ethylene glycol", abbreviated as EG. Its chemical formula is C2H6O2, which is the simplest diol. Ethylene glycol is a colorless, odorless, sweet liquid, toxic to animals, and the lethal dose for humans is about 1.6 g / kg. Ethylene glycol is miscible with water and acetone, but has a relatively low solubility in ethers. It is used as a solvent, antifreeze, and raw material for synthesizing polyester. The high polymer of ethylene glycol, polyethylene glycol (PEG), is a phase transfer catalyst and is also used for cell fusion.

[0003] It is difficult to obtain high-purity ethanol by ordinary distillation. At present, the industrial production mostly adopts the whole set of membrane separation technology and the separate extractive distillation process to obtain anhydrous ethanol. The separate extractive distillation process not only increases equipment investment but also has very high operating energy consumption. Therefore, we propose an energy-saving process for separating ethanol-water by extractive distillation-pervaporation coupling with side-line extraction of ethylene glycol. Summary of the Invention

[0004] The purpose of the present invention is to provide an energy-saving process for separating ethanol-water by extractive distillation-pervaporation coupling with side-line extraction of ethylene glycol to solve the problems mentioned in the above background technique.

[0005] The present invention specifically adopts the following technical solutions to achieve the above purpose:

[0006] An energy-saving process for separating ethanol-water by extractive distillation-pervaporation coupling with side-line extraction of ethylene glycol, comprising:

[0007] Step 1, extractive distillation: introducing an extractant to break the azeotropic state of ethanol-water;

[0008] Step 2, pervaporation: using the selective permeation characteristics of a semi-permeable membrane to separate the mixture by steam drive. Ethanol molecules in the low-concentration ethanol aqueous solution are easily permeable through the membrane layer, while water molecules are intercepted due to their larger volume or weaker polarity;

[0009] Step 3, coupling: coupling pervaporation with the fermentation process, using the steam generated by fermentation as the driving force required for pervaporation, achieving rough separation through membrane retention, and further purification by combining with distillation;

[0010] Step 4, shunting: introducing the separated ethanol and water into different storage containers for packaging and storage.

[0011] Furthermore, the extractant is selected as ethylene glycol.

[0012] Furthermore, the extractive distillation includes the following steps:

[0013] Step 11, process simulation: perform ordinary distillation simulation through software to determine the concentration distribution of the target components in the tower and the optimal side draw position;

[0014] Step 12, determination of side draw position: select the tray with the highest concentration of the target components as the side draw point and set the draw rate;

[0015] Step 13, multi-component separation: intercept the target components at specific positions in the distillation column through side draw, and achieve efficient separation by utilizing the boiling point differences of different components;

[0016] Step 14, condensation and reflux regulation: the extracted steam needs to be condensed by a condenser before being drawn out, and the gas-liquid equilibrium is maintained by adjusting the heating amount, reflux rate and pressure in the tower;

[0017] Step 15, process optimization: adjust the operating parameters in real time according to the side draw situation to ensure the stability of the separation effect.

[0018] Furthermore, in the condensation and reflux regulation, an H-type industrial condenser is selected as the condenser.

[0019] Furthermore, in the condensation and reflux regulation, a reboiler or a temperature sensor and a controller are built in the distillation column.

[0020] Furthermore, in the condensation and reflux regulation, the reflux rate is monitored in real time by an on-line instrument for the concentration of butanediol at the top of the tower, and a trend prediction model is established.

[0021] Furthermore, in the condensation and reflux regulation, the pressure of the extraction is 15 kPa to 20 kPa.

[0022] Furthermore, the pervaporation includes the following steps:

[0023] Step 21, selection of membrane material: select one of polydimethylsiloxane (PDMS) and composite membrane (PDMS / chitosan);

[0024] Step 22, equipment composition: includes a fermentation tank, a pervaporation membrane module and a distillation device.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. Compared with traditional distillation methods, the pervaporation energy consumption of the present invention is reduced by 30%-50%, and there is no need for high temperature and high pressure, achieving energy conservation and consumption reduction; by membrane separation, the concentration of inhibitory components (such as butanol) in the fermentation broth is reduced, the overall yield is increased, and the inhibitory effect is reduced; it can be extended to the separation of other low-boiling substances (such as benzene-ethanol), and the process parameters (temperature, pressure) have a wide regulation range, and the process flexibility is high.

[0027] 2. The equipment cost of the present invention is reduced: a single tower can complete the separation of three components, reducing the investment in double-tower equipment; energy consumption is optimized: by precisely controlling the side-draw position and operating conditions, the energy consumption is reduced; impurities are removed: impurities can be removed synchronously to improve the product purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the working flow chart of the present invention;

[0029] Figure 2 is the working flow chart of extractive distillation in the present invention;

[0030] Figure 3 is the working flow chart of pervaporation in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0032] Please refer to Figure 1 - Figure 3 , the present invention provides an energy-saving process for coupling extractive distillation and pervaporation with side-draw of ethylene glycol to separate ethanol-water, including:

[0033] Step 1, extractive distillation, introducing an extractant to break the azeotropic state of ethanol-water.

[0034] Step 2, pervaporation, using the selective permeation characteristics of the semi-permeable membrane for different substances to achieve separation of the mixture through steam drive. Ethanol molecules in the low-concentration ethanol aqueous solution are easily permeable through the membrane layer, while water molecules are intercepted due to their larger volume or weaker polarity; compared with traditional distillation methods, the pervaporation energy consumption is reduced by 30% to 50%, and there is no need for high temperature and high pressure, achieving energy conservation and consumption reduction; by membrane separation, the concentration of inhibitory components (such as butanol) in the fermentation broth is reduced, the overall yield is increased, and the inhibitory effect is reduced; it can be extended to the separation of other low-boiling substances (such as benzene-ethanol), and the process parameters (temperature, pressure) have a wide regulation range, and the process flexibility is high.

[0035] Step 3, Coupling: Couple the pervaporation process with the fermentation process. The steam generated by fermentation serves as the driving force required for pervaporation, reducing energy consumption and improving overall efficiency. Coarse separation is achieved through membrane retention, and further purification is carried out in combination with rectification.

[0036] Step 4, Shunting: Introduce the separated ethanol and water into different storage containers for packaging and storage.

[0037] In this embodiment, preferably, the extractant is ethylene glycol. As an ionic liquid extractant, ethylene glycol has the characteristics of low toxicity, easy recovery, environmental protection, etc., and is suitable for industrial applications. By using ethylene glycol itself as the extractant and heat coupling, the heating and cooling requirements are reduced, energy consumption can be reduced, no new extractant needs to be introduced, the equipment complexity is reduced, the operation stability is improved, the maintenance cost is reduced, and the operation is simple.

[0038] In this embodiment, preferably, the extractive distillation includes the following steps:

[0039] Step 11, Process simulation: Conduct ordinary distillation simulation through software to determine the concentration distribution of the target components in the tower and the optimal side stream draw position.

[0040] Step 12, Determination of side stream draw position: Select the tray with the highest concentration of the target component as the side stream draw point and set the draw rate.

[0041] Step 13, Multi-component separation: Intercept the target components at specific positions in the distillation column through side stream draw, and achieve efficient separation by utilizing the boiling point differences of different components. Equipment cost reduction: A single tower can complete the separation of three components, reducing the investment in double tower equipment; Energy consumption optimization: By precisely controlling the side stream draw position and operating conditions, energy consumption is reduced; Impurity removal: Impurities can be removed simultaneously to improve the product purity.

[0042] Step 14, Condensation and reflux regulation: The extracted steam needs to be condensed by a condenser before being drawn out, and the gas-liquid equilibrium is maintained by adjusting the heating amount, reflux rate, and pressure in the tower.

[0043] Step 15, Process optimization: Adjust the operating parameters in real time according to the side stream draw situation to ensure the stability of the separation effect.

[0044] In this embodiment, preferably, an H-type industrial condenser is selected for condensation and reflux regulation; The H-type condenser adopts a split structure and is composed of components such as tube bundles, shells, and fans, which is convenient for disassembly and maintenance. The optimized flow channel design reduces the flow resistance and energy consumption. The outer shell is made of high-quality steel plates and surface sprayed plastic treatment, with strong corrosion resistance and extended service life.

[0045] In this embodiment, preferably, a reboiler or a temperature sensor and a controller are built into the distillation column during condensation and reflux regulation; the heating amount in the column can be adjusted through the reboiler or the temperature sensor and the controller to ensure the separation effect and product quality, and the vapor-liquid equilibrium in the column can be guaranteed, thereby ensuring the purity and yield of the product.

[0046] In this embodiment, preferably, during condensation and reflux regulation, the reflux flow rate is monitored in real time by an on-line instrument for the concentration of butanediol at the top of the column, and a trend prediction model is established to ensure the separation effect and product quality, thereby ensuring the purity and yield of the product.

[0047] In this embodiment, preferably, the pressure for extraction during condensation and reflux regulation is 15 kPa to 20 kPa to ensure the separation effect and product quality, thereby ensuring the purity and yield of the product.

[0048] In this embodiment, preferably, pervaporation comprises the following steps:

[0049] Step 21, selecting a membrane material: selecting one of polydimethylsiloxane (PDMS) and a composite membrane (PDMS / chitosan); the high permeability and chemical stability of polydimethylsiloxane (PDMS) to ethanol.

[0050] Step 22, equipment composition: including a fermentation tank, a pervaporation membrane module and a distillation device, which can realize continuous material flow and heat integration.

[0051] The working principle and usage process of the present invention:

[0052] Step 1, extractive distillation, introducing an extractant to break the azeotropic state of ethanol-water; the extractant is selected as ethylene glycol; ethylene glycol as an ionic liquid extractant has the characteristics of low toxicity, easy recovery, environmental protection, etc., is suitable for industrial applications, and through ethylene glycol itself as an extractant and heat coupling, the heating and cooling requirements are reduced, the energy consumption can be reduced, no new extractant needs to be introduced, the equipment complexity is reduced, the operation stability is improved, the maintenance cost is reduced, and the operation is simple.

[0053] The extractive distillation comprises the following steps:

[0054] Step 11, process simulation, performing ordinary distillation simulation through software to determine the concentration distribution of the target component in the column and the optimal side draw position;

[0055] Step 12, determining the side draw position, selecting the tray with the highest concentration of the target component as the side draw point and setting the draw amount;

[0056] Step 13. Multi-component separation: The target component is intercepted at a specific position in the distillation column through side-stream withdrawal, and efficient separation is achieved by utilizing the boiling point differences of different components. Equipment cost reduction: A single column can complete the separation of three components, reducing the investment in double-column equipment; Energy consumption optimization: By precisely controlling the side-stream withdrawal position and operating conditions, energy consumption is reduced; Impurity removal: Impurities can be removed simultaneously to improve product purity;

[0057] Step 14. Condensation and reflux regulation: The extracted steam needs to be condensed by a condenser before being withdrawn. The gas-liquid equilibrium is maintained by adjusting the heating amount, reflux amount, and pressure inside the column; The H-type industrial condenser is selected; The H-type condenser adopts a split structure, consisting of components such as tube bundles, shells, and fans, which is convenient for disassembly and maintenance. The optimized flow channel design reduces flow resistance and energy consumption. The outer shell is made of high-quality steel plates and surface spray-treated, with strong corrosion resistance and extended service life. A reboiler or temperature sensor and controller are installed inside the distillation column; The heating amount inside the column can be adjusted through the reboiler or temperature sensor and controller to ensure the separation effect and product quality, and the gas-liquid equilibrium inside the column can be ensured, thereby ensuring the purity and yield of the product. The reflux amount is monitored in real-time by an on-line instrument for the butanediol concentration at the top of the column, and a trend prediction model is established to ensure the separation effect and product quality, thereby ensuring the purity and yield of the product. The pressure for extraction is 15 kPa - 20 kPa to ensure the separation effect and product quality, thereby ensuring the purity and yield of the product.

[0058] Step 15. Process optimization: The operating parameters are adjusted in real-time according to the side-stream withdrawal situation to ensure the stability of the separation effect.

[0059] Step 2. Pervaporation: Utilizing the selective permeation characteristics of the semi-permeable membrane for different substances, the mixture separation is achieved through steam drive. Ethanol molecules in the low-concentration ethanol aqueous solution are easily permeable through the membrane layer, while water molecules are intercepted due to their larger volume or weaker polarity; Compared with traditional distillation methods, pervaporation reduces energy consumption by 30% - 50%, and there is no need for high temperature and high pressure, achieving energy conservation and consumption reduction; The concentration of inhibitory components (such as butanol) in the fermentation broth is reduced through membrane separation, improving the overall yield and reducing the inhibitory effect; It can be extended to the separation of other low-boiling substances (such as benzene-ethanol), with a wide range of process parameter (temperature, pressure) regulation and process flexibility.

[0060] Pervaporation includes the following steps:

[0061] Step 21. Selection of membrane material: Select one of polydimethylsiloxane (PDMS) and composite membrane (PDMS / chitosan); The high permeability and chemical stability of polydimethylsiloxane (PDMS) to ethanol,

[0062] Step 22. Equipment composition: It includes a fermentation tank, a pervaporation membrane module, and a distillation device, which can realize continuous material flow and heat integration.

[0063] Step 3, coupling: Couple the pervaporation with the fermentation process. Use the steam generated by fermentation as the driving force required for pervaporation to reduce energy consumption and improve the overall efficiency. Coarse separation is achieved through membrane retention, and then further purification is carried out in combination with rectification.

[0064] Step 4, shunting: Introduce the separated ethanol and water into different storage containers for packaging and storage.

[0065] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An energy-saving process for separating ethanol and water by extractive distillation-pervaporation coupling with ethylene glycol side-line extraction, characterized in that: include: Step 1: extractive distillation, introducing an extractant to destroy the azeotropic state of ethanol-water; Step 2, pervaporation, using the selective permeability of the semipermeable membrane to different substances, the mixture is separated by steam drive. The ethanol molecules in the low-concentration ethanol aqueous solution easily pass through the membrane layer, while the water molecules are retained due to their large volume or weak polarity; Step 3: coupling, coupling the pervaporation with the fermentation process, using the steam generated by the fermentation as the driving force for the pervaporation, achieving rough separation through membrane interception, and further purification by distillation; Step 4: splitting, introducing the separated ethanol and water into different storage containers for packaging and storage.

2. The energy-saving process for separating ethanol and water by extractive distillation-pervaporation coupling of ethylene glycol side-line extraction according to claim 1, characterized in that: The extractant is ethylene glycol.

3. The energy-saving process for separating ethanol and water by extractive distillation-pervaporation coupling with ethylene glycol side-line extraction according to claim 1, characterized in that: The extractive distillation comprises the following steps: Step 11: Process simulation: perform ordinary distillation simulation through software to determine the concentration distribution of the target component in the tower and the optimal side line extraction position; Step 12: Determine the side line extraction position, select the tray with the highest concentration of the target component as the side line extraction point, and set the extraction volume; Step 13: Multi-component separation: intercept the target component at a specific position of the distillation tower through side-line extraction, and use the difference in boiling points of different components to achieve efficient separation; Step 14: Condensation and reflux adjustment: the produced steam needs to be condensed in the condenser before being produced, and the gas-liquid balance is maintained by adjusting the heating amount, reflux amount and pressure in the tower; Step 15: Process optimization: adjust the operating parameters in real time according to the side line production situation to ensure the stability of the separation effect.

4. The energy-saving process for separating ethanol and water by extractive distillation-pervaporation coupling with ethylene glycol side-line extraction according to claim 3, characterized in that: The condenser used in the condensation and reflux regulation is an H-type industrial condenser.

5. The energy-saving process for separating ethanol and water by extractive distillation-pervaporation coupling with ethylene glycol side-line extraction according to claim 3, characterized in that: The distillation tower in the condensation and reflux regulation is equipped with a reboiler or a temperature sensor and a controller.

6. The energy-saving process for separating ethanol and water by extractive distillation-pervaporation coupling with ethylene glycol side-line extraction according to claim 3, characterized in that: The reflux amount in the condensation and reflux regulation is monitored in real time by an online instrument for the concentration of butanediol at the top of the tower, and a trend prediction model is established.

7. The energy-saving process for separating ethanol and water by extractive distillation-pervaporation coupling with ethylene glycol side-line extraction according to claim 3, characterized in that: The extraction pressure in the condensation and reflux adjustment is 15 kPa to 20 kPa.

8. The energy-saving process for separating ethanol and water by extractive distillation-pervaporation coupling with ethylene glycol side-line extraction according to claim 1, characterized in that: The pervaporation process comprises the following steps: Step 21, selecting a membrane material: selecting one of polydimethylsiloxane (PDMS) and composite membrane (PDMS / chitosan); Step 22, equipment composition: including a fermentation tank, a pervaporation membrane module and a distillation device.

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