CN111943811A - Energy-saving absolute ethyl alcohol membrane separation refining method - Google Patents
Energy-saving absolute ethyl alcohol membrane separation refining method Download PDFInfo
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Abstract
The invention provides an energy-saving absolute ethyl alcohol membrane separation refining method, which comprises the following steps: preheating a water-containing ethanol raw material by heat exchange equipment, then feeding the water-containing ethanol raw material into a separation tower, extracting steam from the tower top, performing heat exchange, then refluxing the steam to the tower top, performing primary dehydration on the steam which does not participate in the heat exchange by a primary membrane separation unit, and performing deep dehydration on retentate obtained after the primary dehydration by a secondary membrane separation unit; and (3) exchanging heat between the deeply dehydrated retentate and the materials in the tower bottom of the separation tower, conveying the heat-exchanged finished product ethanol to heat exchange equipment to preheat the raw materials, and collecting the ethanol product as an anhydrous ethanol product. The method is used for separating and refining the energy-saving absolute ethyl alcohol by the membrane, the rectification and the heat energy coupling of the steam permeable membrane device are adopted, the saturated steam is recompressed, a secondary vaporization unit is not introduced in the process of membrane separation and dehydration, the steam consumption is effectively saved, meanwhile, the finished product ethyl alcohol steam after membrane dehydration is fully recycled for the vaporization of the kettle liquid of the rectification, the consumption of primary steam is greatly saved, and the energy consumption is reduced.
Description
Technical Field
The invention belongs to the field of ethanol dehydration refining processes, and particularly relates to an energy-saving absolute ethanol membrane separation refining process.
Background
The absolute ethyl alcohol is an ethyl alcohol product with the ethyl alcohol content of more than or equal to 99.5 percent, is an important organic solvent, is widely applied to multiple industries such as medicines, fine chemicals, coatings, sanitary products, cosmetics, grease and the like, is used as an important basic chemical raw material for producing products such as acetaldehyde, ethylene diene, ethylamine, ethyl acetate, acetic acid, chloroethane and the like, and derives intermediates of a plurality of products such as medicines, dyes, coatings, spices, synthetic rubber, detergents, pesticides and the like.
In recent years, with the gradual rise of fuel ethanol gasoline, absolute ethanol has very wide application market value as the most core component of fuel ethanol.
The mass concentration of the finished product alcohol industrially obtained by a common rectification method is less than 95.57 percent, which is the composition of the azeotropic point of alcohol and water under normal pressure and is the highest ethanol concentration which can be reached by the conventional rectification process. Therefore, special methods are needed to treat the alcohol product to obtain the anhydrous alcohol product meeting the requirements. At present, technologies such as an azeotropic distillation method, an extractive distillation method, a molecular sieve adsorption method and the like are mainly applied in industrialization, and the molecular sieve membrane dehydration technology adopting a novel membrane material has great development potential due to the advantages of low energy consumption, high product quality and the like.
Azeotropic distillation is limited by its high energy consumption and low operational flexibility and is often replaced industrially by molecular sieve adsorption dehydration techniques. The molecular sieve is an aluminosilicate crystal with a framework structure, and the principle of separation is mainly a steric effect, because the diameter of water molecules is 0.28nm, the molecular diameter of ethanol is 0.44nm, the water molecules can enter the molecular sieve, and the ethanol molecules are blocked outside, so that the selective adsorption separation of water and ethanol is realized. Generally, an adsorption tower and an analysis tower are combined, azeotropic ethanol is heated by fresh steam, evaporated and vaporized to form high-temperature ethanol steam, the high-temperature ethanol steam is heated to a superheated state by high-pressure steam and enters a molecular sieve adsorption tower in a gas phase form, water molecules are trapped when the ethanol steam flows through a molecular sieve bed layer, ethanol penetrates through the molecular sieve adsorption tower, ethanol dehydration is realized, and ethanol gas discharged from a dehydration device is condensed and cooled to obtain the anhydrous ethanol. And (3) carrying out analysis operation after adsorption saturation, wherein the analysis is carried out by adopting absolute ethyl alcohol, gaseous absolute ethyl alcohol obtained by molecular sieve adsorption is used as a molecular sieve regeneration carrier after being superheated, high-pressure steam is used as a heat source, moisture in the molecular sieve is removed under the high-temperature and low-pressure state, a condenser of an analysis system is cooled by circulating water, the generated low-concentration light wine is sent to a rectifying tower at the front section, and a regeneration system is operated in vacuum. The disadvantages of this technique are evident: 1. the analysis process has high requirement and large energy consumption; 2. the resolving temperature is high, and if the operation is improper, the deterioration and the loss of the molecular sieve are increased; 3. the molecular sieve is expensive and the replacement cost is high; 4. the light wine generated by analysis also needs to enter a rectification procedure at the front section, so that the energy consumption is increased; 5. the adsorption and analysis operation is required to be frequently carried out, the requirement on automation is high, and the requirement on the reliability of an automatic switching valve is very high; 6. the molecular sieve is subjected to adsorption and desorption operation frequently, so that the molecular sieve repeatedly works under the severe temperature change working condition, and the loss of the molecular sieve is serious.
The vapor permeation membrane separation technology taking the inorganic molecular sieve membrane and the components thereof as the core is widely applied in recent years, and has the main advantages of effectively reducing energy consumption, avoiding introducing a third component, along with simple process, land occupation saving and the like compared with the traditional rectification process. But no relevant effective treatment method for energy-saving absolute ethyl alcohol deep dehydration exists at present. The traditional membrane process adopts uniform operating conditions, only the requirement of deep dehydration is realized by increasing the membrane area, but the problems of how to realize deep dehydration of ethanol while saving energy and how to realize the maximum efficiency of each dehydration unit in different dehydration stages by optimizing the configuration of the operating conditions still remain at present.
Disclosure of Invention
The invention aims to provide an energy-saving absolute ethyl alcohol membrane separation and refining method and discloses an energy-saving absolute ethyl alcohol membrane separation and refining device suitable for the method.
The method for separating and refining the energy-saving absolute ethyl alcohol by the membrane comprises the following steps: preheating a hydrous ethanol raw material to 70-90 ℃ by heat exchange equipment at a mass flow rate of 61000-65000 kg/h, then feeding the hydrous ethanol raw material into a separation tower, extracting steam from the tower top, refluxing the steam to the tower top after heat exchange, feeding the steam which does not participate in the heat exchange into a first-stage membrane separation component for primary dehydration after first-stage pressurization and temperature rise at the mass flow rate of 14100-14500 kg/h, and feeding the retentate after primary dehydration into a second-stage membrane separation component for deep dehydration after second-stage pressurization and temperature rise; the dehydrated ethanol finished product steam (namely the deeply dehydrated retentate) exchanges heat with the materials in the tower bottom of the separation tower, the finished product ethanol after heat exchange is conveyed to heat exchange equipment to preheat the raw materials, and then the finished product ethanol is collected into an anhydrous ethanol product.
In order to fully implement the energy-saving absolute ethyl alcohol membrane separation and refining method, the invention further provides a set of energy-saving absolute ethyl alcohol membrane separation and refining device suitable for the method, which comprises a rectification unit, a primary membrane separation unit and a secondary membrane separation unit, wherein: the rectification unit comprises a separation tower, a second heat exchange device and a fifth heat exchange device; the fifth heat exchange device is provided with a material inlet, a material outlet, a heat exchange medium inlet and a heat exchange medium outlet; the second-stage membrane separation unit is provided with a material inlet, a retentate outlet and a permeate outlet; and a retentate outlet of the secondary membrane separation unit is connected with a heat exchange medium inlet of the fifth heat exchange device. The method for performing energy-saving absolute ethanol membrane separation and purification by using the dehydration device comprises the following steps: preheating the hydrous ethanol raw material in first heat exchange equipment, wherein a heat source used for preheating is provided by a heat exchange medium; the preheated raw materials enter a separation tower, steam extracted from the tower top flows back to the tower top after heat exchange, the steam which does not participate in the heat exchange enters a primary membrane separation assembly for primary dehydration after temperature and pressure increase, and retentate after primary dehydration enters a secondary membrane separation assembly for deep dehydration after temperature and pressure increase; the dehydrated ethanol finished product steam (namely the deeply dehydrated retentate) exchanges heat with the materials in the tower bottom of the separation tower, the finished product ethanol after heat exchange is conveyed to heat exchange equipment to preheat the raw materials, and then the finished product ethanol is collected into an anhydrous ethanol product.
The method of the invention is used for separating and refining the energy-saving absolute ethyl alcohol, the rectification is coupled with the heat energy of the vapor permeation membrane device, the saturated vapor obtained by the rectification device is fully utilized, the saturated vapor is recompressed, a secondary vaporization unit is not introduced in the process of membrane separation and dehydration, the vapor consumption is effectively saved, meanwhile, the finished product ethanol vapor after membrane dehydration is fully recycled for the vaporization of the kettle liquid of the rectification, the consumption of primary vapor is greatly saved, and the energy consumption is reduced.
Drawings
FIG. 1 is a diagram of an energy-saving absolute ethanol membrane separation and purification apparatus of the present invention, wherein:
1. a first heat exchange device; 2. a separation column; 3. a second heat exchange device; 4. a primary pressure regulating device; 5. a third heat exchange device; 6. a primary membrane separation module; 7. a secondary pressure regulating device; 8. a fourth heat exchange device; 9. a secondary membrane separation module; 10. a primary permeate processing module; 11. a secondary membrane separation module; 12. a fifth heat exchange device.
Detailed Description
The following detailed description of the invention refers to the accompanying drawings.
The invention provides an energy-saving absolute ethyl alcohol membrane separation refining method, which comprises the steps that an aqueous ethyl alcohol raw material is preheated to 70-90 ℃ through heat exchange equipment at a mass flow rate of 61000-65000 kg/h and then enters a separation tower, steam extracted from the tower top flows back to the tower top after heat exchange, the steam which does not participate in the heat exchange enters a first-stage membrane separation component for primary dehydration after being subjected to first-stage pressurizing and temperature increasing at the mass flow rate of 14100-14500 kg/h, and retentate after primary dehydration enters a second-stage membrane separation component for deep dehydration after being subjected to second-stage pressurizing and temperature increasing; the dehydrated ethanol finished product steam (namely the deeply dehydrated retentate) exchanges heat with the tower bottom of the separation tower, the finished product ethanol after heat exchange is conveyed to heat exchange equipment to preheat the raw material, and then the finished product ethanol is collected as an anhydrous ethanol product. In order to ensure the product quality, in the energy-saving absolute ethanol membrane separation and refining method, the hydrous ethanol raw material contains 3-50 wt% of ethanol, and can be selected from but not limited to a biomass fermentation ethanol raw material, a synthesis gas ethanol raw material, an acetic acid hydrogenation ethanol raw material and a solvent recovery raw material.
In the loop design of the process, the design of the coupling loop effectively realizes the cyclic utilization of system energy, greatly reduces energy consumption and saves operation cost.
In order to better implement the method of the invention, the specific embodiment of the invention provides an energy-saving absolute ethyl alcohol membrane separation and purification device which is specially used for the method, and the method uses the device. The energy-saving absolute ethyl alcohol membrane separation refining device comprises a rectification unit, a first-stage membrane separation unit and a second-stage membrane separation unit, wherein: the rectification unit comprises a separation tower 2, a second heat exchange device 3 and a fifth heat exchange device 12; wherein the fifth heat exchange device 12 is provided with a material inlet, a material outlet, a heat exchange medium inlet and a heat exchange medium outlet; the second-stage membrane separation unit is provided with a material inlet, a retentate outlet and a permeate outlet; the retentate outlet of the secondary membrane separation unit is connected with the heat exchange medium inlet of the fifth heat exchange device 12.
The crude product of the hydrous ethanol to be treated enters a first-stage membrane separation unit through temperature rise and pressure increase, and the primary dehydration process is carried out. Water molecules penetrate through the molecular sieve membrane to form a permeate, and the permeate is discharged out of the system through the membrane separation unit. The ethanol with larger molecular size is intercepted by the molecular sieve membrane, enters a secondary membrane separation unit for continuous separation, and an ethanol product with purity meeting the requirement is separated. And in the system design, heat exchange is formed between the product and the raw materials so as to recycle the heat source of the product to realize the heating of the raw materials.
In the specific embodiment, the rectification unit comprises a separation tower 2, a second heat exchange device 3 and a fifth heat exchange device 12; the primary membrane separation unit comprises a primary pressure regulating device 4, a third heat exchange device 5 and a primary membrane separation assembly 6; the secondary membrane separation unit comprises a secondary pressure regulating device 7, a fourth heat exchange device 8 and a secondary membrane separation assembly 9; wherein, the material inlet of the separation tower 2 is connected with the first heat exchange device 1; the outlet of the permeation side of the primary membrane separation component 6 is connected with a primary permeate treatment component 10; the outlet of the permeation side of the secondary membrane separation component 9 is connected with a secondary permeate treatment component 11; the fifth heat exchange device 12 is provided with a material inlet, a material outlet, a heat exchange medium inlet and a heat exchange medium outlet; the outlet of the retentate side of the secondary membrane separation assembly 9 is connected with the heat exchange medium inlet of the second heat exchange device 11; the heat exchange medium outlet of the fifth heat exchange device 12 is connected with the first heat exchange device 1.
In the energy-saving absolute ethyl alcohol membrane separation and purification device provided by the invention:
the first heat exchange device 1 provides a place for heat exchange between the hydrous ethanol raw material and the finished ethanol, and the heat exchange medium finished ethanol steam from the fifth heat exchange device preheats the raw material, so that the hydrous ethanol raw material can enter the separation tower 2. According to the process requirements, the first heat exchange device 1 can be selected from, but not limited to, a fixed tube-plate type tube-and-tube heat exchanger, a floating head type tube-and-tube heat exchanger, a U-shaped tube-and-tube heat exchanger, a spiral plate type heat exchanger, a spiral tube wound heat exchanger and a plate type heat exchanger.
The separation tower 2 is used for realizing the concentration of the hydrous ethanol through rectification. The separation column 2 can be selected from, but not limited to, a plate column and a packed column.
The second heat exchange device 3 receives the overhead vapor from the separation tower 2, and the overhead vapor is condensed to generate reflux. The second heat exchange device 3 can be selected from, but not limited to, a fixed tube-plate type tube-and-tube heat exchanger, a floating head type tube-and-tube heat exchanger, a U-shaped tube-and-tube heat exchanger, a spiral plate type heat exchanger, a spiral tube wound heat exchanger, and a plate type heat exchanger.
The primary pressure regulating device 4 is used for increasing the pressure of the overhead vapor from the separation column 3, and the primary pressure regulating device 4 can be selected from but not limited to an organic vapor compression device, a mechanical vapor recompression device, and a vapor jet heat pump device.
The third heat exchange device 5 is used for increasing the temperature of the overhead steam from the separation tower 3, and the third heat exchange device 5 can be selected from, but is not limited to, a fixed tube-plate type tube-and-tube heat exchanger, a floating head type tube-and-tube heat exchanger, a U-shaped tube-and-tube heat exchanger, a spiral plate type heat exchanger, a spiral tube wound heat exchanger and a plate type heat exchanger.
The first-stage membrane separation unit is used for realizing the primary dehydration of the hydrous ethanol. For this purpose, the membrane separation unit is preferably an inorganic molecular sieve membrane separation unit, consisting of n (n is a positive integer) molecular sieve membrane modules 6. The membrane assembly can be a single tube pass or a plurality of tube passes, and the area of the single membrane assembly can be controlled between 5 square meters and 300 square meters. The number n of membrane modules arranged in each set is determined according to the separation purpose; when n is greater than 1, the membrane modules can be connected in series or in parallel according to the material condition, the separation target and the like. On the other hand, from the component structure, the present invention can adopt, but is not limited to, specific forms such as a thermostatic membrane component or a baffle-type membrane component. In the embodiment of the present invention, the molecular sieve membrane module may be specifically exemplified by, but not limited to, a plate-type, tubular-type, hollow fiber-type or spiral plate-type molecular sieve membrane module, preferably a tubular-type molecular sieve membrane module. Suitable types of molecular sieves include LTA, SOD, FAU, MOR, FER, MFI, PHI, BEA, CHA, ERI, and mixed crystal molecular sieve membranes thereof, preferably type A molecular sieve membranes.
The secondary pressure regulating device 7 is used for increasing the pressure of the retentate from the primary membrane separation assembly 6, and the secondary pressure regulating device 7 can be selected from but not limited to an organic vapor compression device, a mechanical vapor recompression device, and a vapor jet heat pump device.
The fourth heat exchange device 8 is used for increasing the temperature of the retentate from the primary membrane separation assembly 6. The fourth heat exchange device 8 can be selected from, but is not limited to, a fixed tube-plate type tube-and-tube heat exchanger, a floating head type tube-and-tube heat exchanger, a U-shaped tube-and-tube heat exchanger, a spiral plate type heat exchanger, a spiral tube wound heat exchanger, and a plate type heat exchanger.
The secondary membrane separation unit is used for realizing the primary dehydration of the hydrous ethanol. For this purpose, the membrane separation unit is preferably an inorganic molecular sieve membrane separation unit, consisting of n (n is a positive integer) molecular sieve membrane modules 9. The membrane assembly can be a single tube pass or a plurality of tube passes, and the area of the single membrane assembly can be controlled between 5 square meters and 300 square meters. The number n of membrane modules arranged in each set is determined according to the separation purpose; when n is greater than 1, the membrane modules can be connected in series or in parallel according to the material condition, the separation target and the like. On the other hand, from the component structure, the present invention can adopt, but is not limited to, specific forms such as a thermostatic membrane component or a baffle-type membrane component. In the embodiment of the present invention, the molecular sieve membrane module may be specifically exemplified by, but not limited to, a plate-type, tubular-type, hollow fiber-type or spiral plate-type molecular sieve membrane module, preferably a tubular-type molecular sieve membrane module. Suitable types of molecular sieves include LTA, SOD, FAU, MOR, FER, MFI, PHI, BEA, CHA, ERI, and mixed crystal molecular sieve membranes thereof, preferably type A molecular sieve membranes.
The primary permeate processing module 10 is adapted to receive permeate from the primary membrane separation module 6 and further process the permeate for direct discharge. The primary permeate processing module 10 may be selected from, but is not limited to, a vacuum unit with steam condensate recovery.
The secondary permeate processing module 11 is configured to receive the permeate from the secondary membrane separation module 9 and further process the permeate for direct discharge. The secondary permeate processing module 11 may be selected from, but not limited to, a vacuum unit with steam condensate recovery.
The fifth heat exchange device 12 is used for providing a heat exchange place for the tower bottom material and the finished product ethanol of the separation tower 2, wherein the finished product ethanol from the secondary membrane separation component 9 enters the fifth heat exchange device 12 as a heat exchange medium to exchange heat to the tower bottom material of the separation tower 2, and the latter is converted into a steam state to continuously participate in the reaction. According to the process requirements, the fifth heat exchange device 12 can be selected from, but not limited to, a fixed tube-plate type tube-and-tube heat exchanger, a floating head type tube-and-tube heat exchanger, a U-shaped tube-and-tube heat exchanger, a spiral plate type heat exchanger, a spiral tube wound heat exchanger, and a plate type heat exchanger.
In the structural description of the above-mentioned device, the components that can be determined by those skilled in the art through the prior art in this field are not described, and these components can be exemplified but not limited to: piping for connecting the various devices, feedstock storage tanks for storing and/or supplying aqueous ethanol containing solutions, product storage tanks for receiving/processing ethanol products, and the like. In addition, in combination with the above description, those skilled in the art can determine the most appropriate device selection and type according to the design requirements and requirements under the guidance of the prior art, and it is needless to describe this.
With reference to the energy-saving absolute ethanol membrane separation and purification device in the above embodiment, the energy-saving absolute ethanol membrane separation and purification method according to the present invention can be further described as the following steps:
(1) preheating a raw material containing 3-50 wt% of ethanol to 70-90 ℃ by first heat exchange equipment 1 at a mass flow rate of 61000-65000 kg/h, and then feeding the raw material into a separation tower 2, wherein the heat source used for preheating is absolute ethanol finished product steam from a secondary membrane separation unit; conveying the preheated raw materials to a separation tower 2 for rectification, wherein the tower top temperature of the separation tower 2 is 50-120 ℃, the tower bottom temperature is 80-140 ℃, and the absolute pressure of the tower top is 0.05-0.4 MPa, preferably 0.1-0.2 MPa;
(2) steam extracted from the top of the separation tower 2 is subjected to heat exchange by a second heat exchange device 3, and then returns to the top of the tower for continuous reaction, wherein the reflux ratio of the top of the tower is 0.3-3, and preferably 0.6 +/-0.2; after passing through the primary pressure regulating device 4 and the third heat exchange device 5 at a mass flow rate of 14100-14500 kg/h, the steam which does not exchange heat is conveyed to the primary membrane separation component 6 for primary dehydration, the operating pressure adopted by the primary membrane separation component 6 is greater than the absolute pressure of 0.2MPa, preferably 0.2-0.4 MPa, and the material extracted from the membrane permeation side enters the primary permeate processing component 10;
(3) the retentate extracted from the primary membrane separation component 6 passes through a secondary pressure adjusting device 7 and a fourth heat exchange device 8 and is conveyed to the secondary membrane separation component 9 for deep dehydration, the operating pressure adopted by the secondary membrane separation component 9 is greater than the absolute pressure of 0.4MPa, preferably 0.4-0.8 MPa, the material extracted from the membrane permeation side enters a secondary permeate processing component 11, the material extracted from the membrane retentate side is taken as a heat exchange medium and is conveyed to a fifth heat exchange device 12 for heat exchange with the tower bottom material of the separation tower 2, the material after heat exchange is conveyed to a first heat exchange device 1 for preheating the raw material, and then the product absolute ethyl alcohol is extracted.
The optimization of the overall solution according to the invention should take into account the influence of the combination of technical features on the overall solution in addition to the application of the above-mentioned preferred technical features. The present invention provides the specific embodiment of the above-mentioned energy-saving absolute ethanol membrane separation and purification method to specifically illustrate the implementation mode and effect of the present invention. In this embodiment, an energy-saving absolute ethanol membrane separation and purification apparatus as illustrated in fig. 1 is used in the method, and the apparatuses in the apparatus are selected as follows:
the first heat exchange device 1 is a fixed tube-plate type tubular heat exchanger.
The separation tower 2 is a packed tower.
The second heat exchange device 3 is a fixed tube-plate type tubular heat exchanger.
The first-stage pressure regulating equipment 4 is mechanical vapor recompression equipment.
The third heat exchange device 5 adopts a fixed tube-plate type tubular heat exchanger.
The first-stage membrane separation component 6 is a tubular molecular sieve membrane component; the molecular sieve membrane is an A-type molecular sieve membrane.
And the secondary pressure regulating equipment 7 is mechanical vapor recompression equipment.
The fourth heat exchange device 8 is a fixed tube-plate type tubular heat exchanger.
The secondary membrane separation component 9 is a tubular molecular sieve membrane component; the molecular sieve membrane is an A-type molecular sieve membrane.
The first-stage permeate processing assembly 10 adopts a vacuum unit with steam condensation and recovery.
The second-stage permeate processing assembly 11 is a vacuum unit.
The fifth heat exchange device 12 is a fixed tube-plate type tubular heat exchanger.
The energy-saving anhydrous ethanol membrane separation and refining method implemented by combining the device comprises the following steps:
(1) preheating a raw material containing 20 wt% of ethanol to 80 ℃ through a fixed tube plate type tubular heat exchanger 1 at a mass flow rate of 63000kg/h, and then feeding the raw material into a separation tower 2, wherein a heat source used for preheating is absolute ethanol finished product steam from a secondary membrane separation unit; conveying the preheated raw materials to a packed tower 2 for rectification, wherein the tower top temperature of the packed tower 2 is 86 ℃, the tower bottom temperature is 100 ℃, and the tower top operating pressure is 0.1 MPa;
(2) the concentrated ethanol steam extracted from the top of the packed tower 2 contains 12 wt% of water and is returned after heat exchange by the fixed tube-plate type tube-and-tube heat exchanger 3 at the temperature of 88 DEG CReturning to the tower top for continuous reaction, wherein the reflux ratio at the tower top is 0.6; after passing through mechanical vapor recompression equipment 4 and a fixed tube plate type tube-in-tube heat exchanger 5 at the mass flow rate of 14300kg/h, the steam which is not subjected to heat exchange is conveyed to a tubular molecular sieve membrane component 6 at the pressure of 0.25MPa and the temperature of 130 ℃ for primary dehydration, and the membrane area of the tubular molecular sieve membrane component 6 is 1000m2The membrane material is an A-type molecular sieve membrane, the pressure of the membrane permeation side is 1.5kPa, ethanol steam with the water content of less than 1 wt% is obtained from the membrane side, the wastewater amount measured by the membrane permeation is 1500kg/h, and the ethanol steam is condensed and cooled by a vacuum unit 10 with steam condensation recovery by adopting a low-temperature freezing carrier at 7 ℃ and then is discharged to a wastewater treatment unit;
(3) after the retentate extracted from the tubular molecular sieve membrane component 6 passes through a mechanical vapor recompression device 7 and a fixed tube plate type shell and tube heat exchanger 8, the retentate is conveyed to the tubular molecular sieve membrane component 9 at the pressure of 0.5MPa and the temperature of 140 ℃ for deep dehydration, and the membrane area adopted by the tubular molecular sieve membrane component 9 is 200m2The membrane material is an A-type molecular sieve membrane, the pressure of the membrane permeation side is 0.2kPa, ethanol steam with the water content of less than 0.01 wt% is obtained from the membrane side, the ethanol content is more than 99.99 wt%, the wastewater amount measured by membrane permeation is 50kg/h, and the ethanol steam is condensed and cooled by a vacuum unit 11 by adopting a low-temperature freezing carrier at the temperature of-10 ℃ and then is discharged to a wastewater treatment unit; and (3) extracting finished product absolute ethyl alcohol from the residual membrane seepage side, wherein the finished product absolute ethyl alcohol is 12600kg/h, the pressure is 0.48MPa, the saturation temperature is 120 ℃, the finished product absolute ethyl alcohol is in a steam state, the finished product absolute ethyl alcohol is used as a heat exchange medium and conveyed to the fixed tube plate type tubular heat exchanger 12 to exchange heat with the tower bottom material of the packed tower 2, the material after heat exchange is conveyed to the fixed tube plate type tubular heat exchanger 1 to preheat the raw material to 80 ℃, and then the finished product absolute ethyl alcohol is extracted.
The invention fully optimizes the dehydration efficiency of different dehydration units and different operation conditions, and realizes the aims of effective energy integrated utilization and compromise of cost and product quality. The heat is completely recycled, the membrane separation unit avoids steam consumed by phase change through secondary vaporization, and the consumption of primary steam in the tower kettle of the rectifying tower is greatly reduced through high-grade ethanol steam generated by at least two-stage pressurization and temperature rise, so that compared with the traditional process, the whole energy-saving benefit of the device can reach 40-60%.
Claims (9)
1. An energy-saving absolute ethyl alcohol membrane separation refining method is characterized by comprising the following steps: preheating a hydrous ethanol raw material to 70-90 ℃ by heat exchange equipment at a mass flow rate of 61000-65000 kg/h, then feeding the hydrous ethanol raw material into a separation tower, extracting steam from the tower top, refluxing the steam to the tower top after heat exchange, feeding the steam which does not participate in the heat exchange into a first-stage membrane separation component for primary dehydration after first-stage pressurization and temperature rise at the mass flow rate of 14100-14500 kg/h, and feeding the retentate after primary dehydration into a second-stage membrane separation component for deep dehydration after second-stage pressurization and temperature rise;
and (3) exchanging heat between the dehydrated ethanol finished product steam and the materials in the tower bottom of the separation tower, conveying the heat exchanged ethanol finished product to heat exchange equipment to preheat the raw materials, and collecting the ethanol finished product as an anhydrous ethanol product.
2. The method according to claim 1, wherein the aqueous ethanol feedstock comprises 3 to 50 wt% of ethanol, and is selected from the group consisting of a biomass fermentation ethanol feedstock, a syngas-to-ethanol feedstock, an acetic acid hydrogenation-to-ethanol feedstock, and a solvent recovery feedstock.
3. The method according to claim 1, wherein the temperature of the top of the separation tower is 50-120 ℃ and the temperature of the bottom of the separation tower is 80-140 ℃.
4. The method according to claim 1, wherein the overhead absolute pressure of the separation tower is 0.05-0.4 MPa, and the overhead reflux ratio is 0.3-3.
5. The process of claim 1 wherein the primary membrane separation module is operated at a pressure greater than 0.2MPa absolute.
6. The method of claim 1, wherein the secondary membrane separation module is operated at a pressure greater than 0.4MPa absolute.
7. The method according to claim 1, wherein the method uses an energy-saving absolute ethanol membrane separation and purification device, and the device comprises a rectification unit, a primary membrane separation unit and a secondary membrane separation unit, wherein: the rectification unit comprises a separation tower (2), a second heat exchange device (3) and a fifth heat exchange device (12);
wherein the fifth heat exchange device (12) is provided with a material inlet, a material outlet, a heat exchange medium inlet and a heat exchange medium outlet; the second-stage membrane separation unit is provided with a material inlet, a retentate outlet and a permeate outlet;
the retentate outlet of the secondary membrane separation unit is connected with the heat exchange medium inlet of the fifth heat exchange device (12).
8. The method according to claim 7, wherein the energy-saving absolute ethanol membrane separation refining device comprises a rectification unit, a primary membrane separation unit and a secondary membrane separation unit, wherein: the rectification unit comprises a separation tower (2), a second heat exchange device (3) and a fifth heat exchange device (12); the primary membrane separation unit comprises a primary pressure regulating device (4), a third heat exchange device (5) and a primary membrane separation assembly (6); the secondary membrane separation unit comprises a secondary pressure regulating device (7), a fourth heat exchange device (8) and a secondary membrane separation component (9);
wherein, the material inlet of the separation tower (2) is connected with a first heat exchange device (1); the outlet of the permeation side of the primary membrane separation component (6) is connected with a primary permeate treatment component (10); the outlet of the permeation side of the secondary membrane separation component (9) is connected with a secondary permeate treatment component (11);
the fifth heat exchange device (12) is provided with a material inlet, a material outlet, a heat exchange medium inlet and a heat exchange medium outlet; the outlet of the retentate side of the secondary membrane separation component (9) is connected with the heat exchange medium inlet of the second heat exchange device (11); the heat exchange medium outlet of the fifth heat exchange device (12) is connected with the first heat exchange device (1).
9. The method of claim 8, comprising the steps of:
(1) preheating 3-50 wt% of ethanol in the hydrous ethanol raw material to 70-90 ℃ by first heat exchange equipment (1) at a mass flow rate of 61000-65000 kg/h, and then feeding the ethanol raw material into a separation tower (2), wherein the heat source used for preheating is anhydrous ethanol finished product steam from a secondary membrane separation unit; conveying the preheated raw materials to a separation tower (2) for rectification, wherein the tower top temperature of the separation tower (2) is 50-120 ℃, the tower bottom temperature is 80-140 ℃, and the tower top absolute pressure is 0.05-0.4 MPa;
(2) steam extracted from the top of the separation tower (2) is subjected to heat exchange by second heat exchange equipment (3), and then returns to the top of the tower to continue reacting, wherein the reflux ratio of the top of the tower is 0.3-3; after passing through a first-stage pressure regulating device (4) and a third heat exchange device (5) at a mass flow rate of 14100-14500 kg/h, the steam which does not exchange heat is conveyed to a first-stage membrane separation component (6) for primary dehydration, the operating pressure adopted by the first-stage membrane separation component (6) is greater than the absolute pressure of 0.2MPa, and the material extracted from the membrane permeation side enters a first-stage permeate processing component (10);
(3) after the retentate extracted from the first-stage membrane separation assembly (6) passes through a second-stage pressure adjusting device (7) and a fourth heat exchange device (8), the retentate is conveyed to the second-stage membrane separation assembly (9) for deep dehydration, the operating pressure adopted by the second-stage membrane separation assembly (9) is greater than 0.4MPa, the material extracted from the membrane permeation side enters a second-stage permeate processing assembly (11), the material extracted from the membrane retentate side is used as a heat exchange medium and conveyed to a fifth heat exchange device (12) for heat exchange with the tower bottom material of the separation tower (2), the material after heat exchange is conveyed to a first heat exchange device (1) for preheating the raw material, and then the product anhydrous ethanol is extracted.
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