High-yield low-energy-consumption ethanol rectification system capable of realizing zero discharge of wastewater

Abstract

The invention relates to the technical field of ethanol rectification separation, and discloses a high-yield low-energy-consumption ethanol rectification system capable of realizing zero discharge of wastewater, which comprises a light component removal rectification unit, an ethanol pressurization tower, an ethanol decompression tower and an ethanol rectification tower. By strictly controlling the operation pressure of the light component removal rectifying tower, the ethanol pressurizing tower and the ethanol vacuum tower, the rectifying wastewater can meet the recycling index requirement of a fermentation unit, and zero discharge of the wastewater in the ethanol refining process is realized. And under a low-pressure condition, a multi-effect thermal coupling energy-saving rectification process and a light component removal rectification tower reflux tank extraction structure are designed, so that the operation energy consumption is greatly reduced, and meanwhile, the ethanol yield is improved. The method has the technical characteristics of low energy consumption, high yield and zero wastewater discharge, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of ethanol rectification and separation, and specifically to a high-yield and low-energy-consumption ethanol rectification system capable of achieving zero wastewater discharge. Background Art

[0002] At present, most ethanol industrial production relies on the grain fermentation route, and commonly used crops such as corn are used as the main raw materials. Although the process is mature, the grain resources themselves are in short supply, and large-scale consumption in the long term is not sustainable. At the same time, the process route of using syngas or industrial tail gas for biological fermentation to produce ethanol has gradually become an alternative solution, with lower raw material costs, more stable sources, and more in line with the future industrial direction.

[0003] However, the properties of the syngas biological fermentation broth are very different from those of the traditional grain fermentation broth. The ethanol content is low and the water content exceeds 96%. This characteristic determines that the entire purification process not only has relatively high energy consumption, but also generates a large amount of high-temperature rectification wastewater, with high cooling and post-treatment costs, and there are also environmental protection risks.

[0004] In addition, the fermentation broth also contains impurities such as esters that azeotrope with ethanol, and it is difficult to completely separate them by conventional rectification methods. It is necessary to draw out a part of ethanol to ensure the qualification of the final ethanol product, resulting in a large loss of ethanol and difficulty in improving the yield. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a high-yield and low-energy-consumption ethanol rectification system capable of achieving zero wastewater discharge, which solves the problems of high energy consumption and difficult wastewater treatment in the process of producing ethanol by syngas microbial fermentation, and improves the ethanol recovery rate.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A high-yield and low-energy-consumption ethanol rectification system capable of achieving zero wastewater discharge, comprising:

[0007] A light-component removal rectification unit, which consists of a flash tank, an ethanol light-component removal tower, a light-component removal tower condenser, a light-component removal tower reflux extraction tank, a light-component removal tower after-cooler, a light-component removal tower reboiler, and a light-component removal tower condensate reboiler. The raw material fermentation broth enters the flash tank for flashing through three-stage preheating. The gas phase at the top of the flash tank is combined with the gas phase at the top of the ethanol light-component removal tower and then enters the light-component removal tower condenser, and the liquid phase at the bottom is sent to the ethanol light-component removal tower;

[0008] An ethanol pressurization tower, which is used to receive the light-component-removed ethanol from the light-component removal rectification unit. The crude ethanol gas phase is drawn from the top of the tower, and is used as a heat source to heat the ethanol vacuum tower reboiler and the light-component removal tower reboiler, and at the same time, it is condensed by itself and enters the ethanol pressurization tower reflux tank;

[0009] The ethanol vacuum tower is used to receive the light - removed ethanol from the light - removal rectification unit. The crude ethanol is drawn from the top of the tower, combined with the crude ethanol from the reflux drum of the pressurized tower, and sent to the ethanol rectification tower after two - stage pre - heating.

[0010] The ethanol rectification tower operates under pressure. The gas phase at the top of the tower serves as the heat source for the reboiler of the ethanol pressurized tower. After heat exchange, the top - tower gas is condensed and enters the reflux drum of the ethanol rectification tower. Part of it is refluxed, and the other part is drawn as fuel alcohol. A steam reboiler is installed on the ethanol rectification tower, and the heat source is medium - pressure steam.

[0011] The heat - exchange network is used to reduce the operating load of each tower. The waste water at the bottom of the tower and other high - temperature logistics in the system are used to heat the reboiler, or multiple - stage heat exchange is carried out with the low - temperature feed materials to heat the feed temperature to near the bubble - point temperature, further reducing the system energy consumption.

[0012] Preferably, the ethanol light - removal tower operates under vacuum. The gas phase at the top of the tower is combined with the gas phase of the flash tank and then enters the light - removal tower condenser. The condensed material flows by gravity to the light - removal tower reflux extraction tank. Under the action of extraction water, the water phase and the oil phase are separated. The water phase flows back to the ethanol light - removal tower, and the oil phase overflows to the other side of the baffle. After accumulating to the set liquid level, it is drawn out. The post - cooler of the light - removal tower further cools the non - condensable components in the light - removal tower reflux extraction tank to deeply recover ethanol.

[0013] Specifically, in the light - removal tower reflux extraction tank, the water phase and the oil phase are naturally separated. The oil phase, which mainly contains low - boiling impurities (such as ethyl acetate, etc.), is on the upper layer. As the liquid level accumulates and crosses the baffle to the other side, ethanol dissolves in the water phase and flows back to the ethanol light - removal tower with the water phase, avoiding excessive extraction of ethanol during the process of removing azeotropic impurities, improving the ethanol recovery rate. The oil phase is drawn out after accumulating to the set liquid level, ensuring the stable operation of the system.

[0014] In addition, the post - cooler of the light - removal tower further deeply cools the non - condensable components in the reflux extraction tank, enabling full recovery of the remaining ethanol therein, reducing ethanol loss, and at the same time reducing the burden of subsequent waste - gas treatment. This series of optimization measures ensure that the system maximizes resource recovery, reduces energy consumption, improves overall economic efficiency and environmental benefits while efficiently separating ethanol.

[0015] Preferably, two reboilers are installed on the ethanol pressurized tower, including:

[0016] The steam reboiler of the ethanol pressurized tower, which uses low - pressure steam as the heat source;

[0017] The reboiler of the ethanol pressurized tower, which uses the top - tower gas of the ethanol rectification tower as the heat source.

[0018] Specifically, the ethanol pressurized tower steam reboiler uses low-pressure steam to provide initial heat. The ethanol pressurized tower reboiler cleverly utilizes the top gas of the ethanol rectification tower as a heat source, filling the heat gap that originally needed external supply, reducing additional energy input, and optimizing the energy utilization rate of the system.

[0019] In addition, the operating pressure of the ethanol pressurized tower is strictly controlled below 170 kPa to ensure that the wastewater at the bottom of the tower can be recycled back to the fermentation unit without causing microbial inactivation due to high temperature. This not only reduces the use of fresh water in the fermentation unit, lowers production costs, but also avoids the pollution of wastewater discharge, truly achieving zero wastewater discharge.

[0020] Preferably, two reboilers are provided for the ethanol vacuum tower, including:

[0021] The ethanol vacuum tower reboiler uses the top gas of the ethanol pressurized tower as a heat source.

[0022] The ethanol vacuum tower product gas reboiler uses the ethanol gas from the molecular sieve unit as a heat source.

[0023] Specifically, the ethanol vacuum tower reboiler uses the top gas of the ethanol pressurized tower as a heat source, relying on heat coupling technology to achieve internal energy recovery and reduce dependence on external steam. The ethanol vacuum tower product gas reboiler further utilizes the heat of the ethanol gas from the molecular sieve unit, enabling effective utilization of the thermal energy that should have been condensed and cooled.

[0024] Preferably, a part of the top condensate of the ethanol rectification tower is refluxed to the ethanol rectification tower, and the other part is taken out as fuel alcohol. 95% ethanol gas is taken out from the side line of the rectifying section and sent to the molecular sieve dehydration unit. The fusel oil is taken out from the side line of the stripping section, and the wastewater at the bottom of the tower is recycled to the fermentation unit after heat exchange.

[0025] Specifically, fuel alcohol is taken out from the top of the tower, which contains flammable components such as methanol and ethanol and can be used as energy or chemical fuel. This design optimizes the material separation in the ethanol rectification process, making the rectification products purer.

[0026] In the stripping section of the ethanol rectification tower, fusel oil is taken out from the side line, effectively separating high-boiling impurities in the raw materials, ensuring that the purity of the ethanol product meets the standards and meets the requirements for the fusel content in the recycled rectification wastewater.

[0027] Preferably, the heat exchange network includes:

[0028] The wastewater at the bottom of the ethanol pressurized tower heats the ethanol pressurized tower feed preheater;

[0029] The wastewater at the bottom of the ethanol rectification column preheats the feed in the ethanol rectification column feed preheater II at the second stage. After mixing all the bottom wastewater, it sequentially passes through the de-light tower feed preheater III and the de-light tower feed preheater I for the third and first stage preheating of the raw materials;

[0030] The feed stream of the ethanol vacuum tower is preheated at the second stage in the de-light tower feed preheater II.

[0031] Specifically, the heat exchange network of this system realizes the efficient utilization of energy through precise heat recovery and multi-stage heat exchange strategies. The waste heat of the wastewater at the bottom of the ethanol pressurization tower is used to heat the ethanol pressurization tower feed preheater, enabling the feed to reach a temperature close to the bubble point before entering the tower, which can directly reduce the load of the ethanol pressurization tower. At the same time, the wastewater at the bottom of the ethanol rectification column is preheated at the second stage in the ethanol rectification column feed preheater II, increasing the feed temperature and reducing the overall energy consumption of the ethanol rectification column. Subsequently, all the bottom wastewater is mixed and flows through the de-light tower feed preheater III and the de-light tower feed preheater I in sequence, respectively completing the third and first stage preheating of the raw materials and realizing the cascade utilization of energy.

[0032] In addition, the feed stream of the ethanol vacuum tower completes the second stage preheating of the raw materials in the de-light tower feed preheater II, further reducing the load of the ethanol de-light tower.

[0033] Preferably, the steam condensate generated by the ethanol pressurization tower steam reboiler and the ethanol rectification tower steam reboiler is mixed and used as the heat source of the de-light tower condensate reboiler and the heat source of the ethanol rectification column feed preheater I.

[0034] Specifically, the waste heat of the steam condensate is used in the de-light tower condensate reboiler to provide part of the heat energy, reducing the reboiler load. Subsequently, the remaining heat is further used in the ethanol rectification column feed preheater I to perform the first stage heating on the feed entering the rectification column, reducing the total energy consumption required for the operation of the rectification column.

[0035] The present invention provides a high-yield and low-energy-consumption ethanol rectification system that can achieve zero wastewater discharge. It has the following beneficial effects:

[0036] 1. By precisely controlling the operating pressure of each tower and strictly limiting the operating temperature, the present invention enables the wastewater temperature to meet the survival requirements of microorganisms, and the wastewater is recycled to the fermentation unit to achieve zero wastewater discharge. Compared with the existing high-temperature and high-pressure process route, it eliminates the problems of strain inactivation and circulation obstacles caused by high-temperature wastewater, avoids the environmental pressure brought by wastewater discharge, and also reduces the wastewater treatment burden.

[0037] 2. With the help of the multi-tower heat coupling design and the coordinated operation of the heat exchange network, the present invention significantly reduces steam consumption and dependence on external heat sources, providing a reliable guarantee for reducing production costs.

[0038] 3. By designing a reflux extraction tank structure at the top of the light removal rectification column, the present invention uses water as an extraction agent to extract ethanol, and at the same time, with the condensation treatment of the after-cooler, it realizes the effective separation of azeotropic impurities such as ethyl acetate and the deep recovery of ethanol. Different from the traditional process that only relies on the way of extracting more ethanol to take away the azeotrope, the ethanol loss is significantly reduced, and the ethanol purity and recovery rate are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic diagram of the overall structure of the system of the present invention;

[0040] Figure 2 is a schematic diagram of the structure of the three-stage preheater of the present invention;

[0041] Figure 3 is a schematic diagram of the structure of the ethanol pressurizing column of the present invention;

[0042] Figure 4 is a schematic diagram of the structure of the ethanol depressurizing column of the present invention;

[0043] Figure 5 is a schematic diagram of the structure of the ethanol rectification column of the present invention.

[0044] Among them, 1. Light removal tower feed preheater I; 2. Light removal tower feed preheater II; 3. Light removal tower feed preheater III; 4. Flash tank; 5. Ethanol light removal tower; 6. Light removal tower condenser; 7. Light removal tower reflux extraction tank; 8. Light removal tower after-cooler; 9. Light removal tower condensate reboiler; 10. Light removal tower reboiler; 11. Ethanol pressurizing column feed preheater; 12. Ethanol pressurizing column; 13. Ethanol pressurizing column reflux tank; 14. Ethanol pressurizing column steam reboiler; 15. Ethanol pressurizing column reboiler; 16. Ethanol depressurizing column; 17. Ethanol depressurizing column condenser; 18. Ethanol depressurizing column reflux tank; 19. Ethanol depressurizing column reboiler; 20. Ethanol depressurizing column product gas reboiler; 21. Ethanol rectification column feed preheater I; 22. Ethanol rectification column feed preheater II; 23. Ethanol rectification column; 24. Ethanol rectification column reflux tank; 25. Ethanol rectification column steam reboiler. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0046] Embodiment 1:

[0047] Please refer to the attached Figure 1 - attached Figure 5, an embodiment of the present invention provides a high-yield and low-energy-consumption ethanol rectification system capable of achieving zero wastewater discharge, comprising:

[0048] The raw material fermentation broth is pumped to the ethanol rectification unit, preheated to about 70°C through the de-light tower feed preheater I 1, the de-light tower feed preheater II 2, and the de-light tower feed preheater III 3 in three stages, and then enters the flash tank 4 for flashing. The gas phase at the top of the flash tank 4 and the gas phase at the top of the de-light rectification tower 5 are combined, and the liquid phase at the bottom of the tank is sent to the de-light rectification tower 5 as the feed.

[0049] The de-light rectification tower 5 operates under reduced pressure, with an operating pressure of 40 kPa - 60 kPa. The gas phase at the top of the tower and the gas phase of the flash tank 4 are combined and enter the de-light tower condenser 6. After condensation, the material flows by gravity to the de-light tower reflux extraction tank 7, and at the same time, extraction water is added to the tank to make ethanol reflux with the water phase, and the azeotropic components are taken out with the oil phase. A de-light tower after-cooler 8 is provided to further cool the non-condensable components in the de-light tower reflux extraction tank 7 for deep recovery of ethanol. The de-light ethanol is taken out from the side line and divided into two streams. One stream is preheated by the ethanol pressurization tower feed preheater 11 and then sent to the ethanol pressurization tower 12, and the other stream is sent to the ethanol vacuum tower 16 after heat exchange with the de-light tower feed preheater II 2. The wastewater is taken out from the bottom of the tower and combined with the wastewater from other tower bottoms.

[0050] The ethanol pressurization tower 12 operates under pressure, and the operating pressure is controlled not to be higher than 170 kPa. The crude ethanol gas at the top of the tower is used to heat the ethanol vacuum tower reboiler 19 and the de-light tower reboiler 10 in sequence. The condensed crude ethanol enters the ethanol pressurization tower reflux tank 13, part of it is refluxed, and the other part is taken out and mixed with the crude ethanol at the top of the ethanol vacuum tower. The wastewater is taken out from the bottom of the tower, and the waste heat of the wastewater is used to preheat the ethanol pressurization tower feed preheater 11, and then combined with the wastewater from other tower bottoms.

[0051] The ethanol vacuum tower 16 operates under reduced pressure, with an operating pressure of 30 kPa - 50 kPa. The crude ethanol gas at the top of the tower is condensed by the ethanol vacuum tower condenser 17 and sent to the ethanol vacuum tower reflux tank 18. Part of the crude ethanol is refluxed, and part of it is taken out and mixed with the crude ethanol at the top of the ethanol pressurization tower 12. After being preheated by the ethanol rectification tower feed preheater I 21 and the ethanol rectification tower feed preheater II 22, it is sent to the ethanol rectification tower 23. The wastewater is taken out from the bottom of the tower and combined with the wastewater at the bottom of the ethanol pressurization tower 12, the wastewater at the bottom of the ethanol de-light tower 5, and the wastewater at the bottom of the ethanol rectification tower 23. It heats the de-light tower feed preheater III 3 and the de-light tower feed preheater I 1 in sequence, and finally is sent back to the fermentation unit for reuse.

[0052] The ethanol rectification column 23 operates under pressure, with an operating pressure of 470 kPa to 520 kPa. The overhead gas of the column serves as the heat source for the reboiler 15 of the ethanol pressurizing column. After heat exchange, it enters the reflux drum 24 of the ethanol rectification column. Part of the liquid phase is refluxed, and part is taken out as the main components of fuel alcohol, which are methanol and ethanol products. The 95% ethanol gas is taken out from the side line of the rectifying section and sent to the molecular sieve dehydration system for purification to 99.9% of high-quality industrial ethanol or fuel ethanol. The fusel oil is taken out from the side line of the stripping section. The wastewater is taken out from the bottom of the column. After preheating the feed preheater II 22 of the ethanol rectification column, it is combined with the wastewater from other column bottoms.

[0053] Both the steam reboiler 25 of the ethanol rectification column and the steam reboiler 14 of the ethanol pressurizing column are heated by steam. The two streams of steam condensate after heating are combined and used to heat the condensate reboiler 9 of the light component removal column and the feed preheater I 21 of the ethanol rectification column.

[0054] In order to further save energy, the product gas reboiler 20 of the ethanol vacuum column is heated by the ethanol product gas from the molecular sieve system.

[0055]

[0056] Summary: In this embodiment, the process flow of "a high-yield and low-energy-consumption ethanol rectification system capable of achieving zero wastewater discharge" is adopted to treat the raw material fermentation broth with an ethanol content of about 2.50%. Through multi-stage rectification and heat integration operations such as the light component removal column 5, the ethanol pressurizing column 12, the ethanol vacuum column 16, and the ethanol rectification column 23, anhydrous ethanol products are successfully produced.

[0057] Finally, high-quality anhydrous ethanol products with an ethanol purity of ≥99.9%, a water content of ≤0.1%, a methanol content of ≤50 mg / L, and other fusel alcohols of ≤250 mg / L are obtained. The ethanol recovery rate reaches ≥97.5%, and the steam consumption is 3.4 t / t ethanol. The entire process realizes the reuse of wastewater, the cascaded utilization of energy, and the effective separation of azeotropes, and has the advantages of high ethanol recovery rate, low energy consumption, and good environmental protection effect.

[0058] Example 2:

[0059] The process flow of "a high-yield and low-energy-consumption ethanol rectification system capable of achieving zero wastewater discharge" in Example 1 is adopted. When the ethanol content in the raw material fermentation broth is low, fuel ethanol is produced. The specific relevant parameters are as follows:

[0060]

[0061] Summary: In this embodiment, the above-mentioned rectification process is also adopted. For the raw material fermentation broth with a low ethanol content (about 2.00%), the operating parameters are optimized to produce fuel ethanol.

[0062] Finally, fuel ethanol products with ethanol purity ≥ 99.5%, water content ≤ 0.8%, methanol ≤ 0.5%, and solvent-washed gum ≤ 5 mg / 100 mL are obtained. The ethanol recovery rate reaches ≥ 98.8%, and the steam consumption is 3.9 t / t ethanol.

[0063] This process also realizes zero wastewater discharge and comprehensive utilization of heat energy, is applicable to the production of fuel ethanol from low-concentration ethanol fermentation broth, and ensures a high ethanol recovery rate.

[0064] Example 3:

[0065] Adopt the process flow of "a high-yield and low-energy-consumption ethanol rectification system capable of realizing zero wastewater discharge" in Example 1. When the ethanol content in the raw material fermentation broth is relatively high, anhydrous ethanol is produced. The specific relevant parameters are as follows:

[0066]

[0067] Summary: In this example, using the fermentation broth with a relatively high ethanol content (about 10.00%) as the raw material, anhydrous ethanol is produced through optimized production by the same rectification process flow.

[0068] Finally, high-purity anhydrous ethanol products with ethanol purity ≥ 99.9%, water content ≤ 0.1%, methanol ≤ 50 mg / L, and other higher alcohols ≤ 250 mg / L are obtained. The ethanol recovery rate reaches ≥ 98%, and the steam consumption is reduced to 2.9 t / t ethanol.

[0069] Benefiting from the increase in the concentration of raw material ethanol, this process significantly reduces energy consumption on the basis of ensuring product quality, further improves the efficiency of heat energy recovery and utilization, and is an optimal process plan for rectifying high-concentration fermentation broth.

[0070] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-yield and low-energy ethanol rectification system capable of achieving zero discharge of wastewater, characterized in that Comprising: A light component removal rectification unit, which consists of a flash tank (4), an ethanol light component removal tower (5), a light component removal tower condenser (6), a light component removal tower reflux extraction tank (7), a light component removal tower after-cooler (8), a light component removal tower reboiler (10) and a light component removal tower condensate reboiler (9). The raw fermentation broth enters the flash tank (4) for flash evaporation through three-stage preheating. The gas phase at the top of the flash tank (4) is combined with the gas phase at the top of the ethanol light component removal tower (5) and sent to the light component removal tower condenser (6) for condensation. The liquid phase at the bottom is sent to the ethanol light component removal tower (5). An ethanol pressurization tower (12), which is used to receive the light component removed ethanol from the light component removal rectification unit. The crude ethanol gas is drawn from the top of the tower and used as a heat source to heat the ethanol vacuum tower reboiler (19) and the light component removal tower reboiler (10), and at the same time, it is condensed by itself and enters the ethanol pressurization tower reflux tank (13). An ethanol vacuum tower (16), which is used to receive the light component removed ethanol from the light component removal rectification unit. The crude ethanol is drawn from the top of the tower and combined with the crude ethanol from the pressurization tower reflux tank (13). After two-stage preheating, it is sent to the ethanol rectification tower (23). An ethanol rectification tower (23), which through pressurized operation, the gas phase at the top of the tower is used as the heat source for the ethanol pressurization tower reboiler (15). After heat exchange, the gas at the top of the tower is condensed and enters the ethanol rectification tower reflux tank (24). Part of it is refluxed, and the other part is drawn as fuel alcohol. A heat exchange network, which is used to reduce the operation load of each tower. The reboiler is heated by the waste water at the bottom of the tower and other high-temperature logistics in the system, or undergoes multi-stage heat exchange with the low-temperature incoming tower materials to heat the feed temperature to near the bubble point temperature, so as to further reduce the system energy consumption.

2. A high-yield and low-energy ethanol rectification system capable of achieving zero wastewater discharge according to claim 1, characterized in that, The ethanol light component removal tower (5) adopts vacuum operation. The gas phase at the top of the tower is combined with the gas phase of the flash tank (4) and then enters the light component removal tower condenser (6). The condensed material flows by gravity to the light component removal tower reflux extraction tank (7). Under the action of extraction water, the water phase and the oil phase are separated. The water phase is refluxed to the ethanol light component removal tower (5), and the oil phase overflows to the other side of the partition plate and is drawn out after accumulating to the set liquid level. The light component removal tower after-cooler (8) further cools the non-condensable components in the light component removal tower reflux extraction tank (7) to deeply recover ethanol.

3. A high-yield and low-energy ethanol rectification system capable of achieving zero wastewater discharge according to claim 1, characterized in that, The operating pressure of the ethanol pressurization tower (12) does not exceed 170 kPa to ensure that the microorganisms in the waste water are not inactivated.

4. A high-yield and low-energy ethanol rectification system capable of achieving zero wastewater discharge according to claim 1, characterized in that, The ethanol pressurization tower (12) is provided with two reboilers, which include: An ethanol pressurization tower steam reboiler (14), which uses low-pressure steam as the heat source; An ethanol pressurization tower reboiler (15), which uses the gas phase at the top of the ethanol rectification tower (23) as the heat source.

5. A high-yield and low-energy ethanol rectification system capable of achieving zero wastewater discharge according to claim 1, characterized in that, The crude ethanol gas at the top of the ethanol vacuum tower (16) is condensed by the ethanol vacuum tower condenser (17) and sent to the ethanol vacuum tower reflux tank (18). Part of the crude ethanol is refluxed, and the other part is drawn out and mixed with the crude ethanol at the top of the ethanol pressurization tower (12). After being preheated by the ethanol rectification tower feed preheater I (21) and the ethanol rectification tower feed preheater II (22), it is sent to the ethanol rectification tower (23).

6. A high-yield and low-energy ethanol rectification system capable of achieving zero wastewater discharge according to claim 1, characterized in that, The ethanol vacuum tower (16) is provided with two reboilers, which include: An ethanol vacuum tower reboiler (19), which uses the gas phase at the top of the ethanol pressurization tower (12) as the heat source, An ethanol vacuum tower product gas reboiler (20), which uses the ethanol gas from the molecular sieve unit as the heat source.

7. A high-yield and low-energy ethanol rectification system capable of achieving zero wastewater discharge according to claim 1, characterized in that, The side line of the rectifying section of the ethanol rectification column (23) extracts 95% ethanol gas, which is sent to the molecular sieve dehydration unit, and the side line of the stripping section extracts fusel oil.

8. A high-yield and low-energy-consumption ethanol rectification system capable of achieving zero wastewater discharge according to claim 1, characterized in that, A steam reboiler (25) is provided on the ethanol rectification column (23), and the heat source is medium-pressure steam.

9. A high-yield and low-energy ethanol rectification system capable of achieving zero wastewater discharge according to claim 1, characterized in that, The heat exchange network includes: The wastewater at the bottom of the ethanol pressurization column (12) heats the ethanol pressurization column feed preheater (11); The wastewater at the bottom of the ethanol rectification column (23) performs secondary preheating on the feed in the ethanol rectification column feed preheater II (22). After mixing all the bottom wastewater, it sequentially passes through the de-light tower feed preheater III (3) and the de-light tower feed preheater I (1) for the third and first stages of raw material preheating; The feed stream of the ethanol vacuum column (16) is preheated at the second stage of the raw material in the de-light tower feed preheater II (2).

10. A high-yield and low-energy-consumption ethanol rectification system capable of achieving zero wastewater discharge according to claim 1, characterized in that, The steam condensate generated by the ethanol pressurization column steam reboiler (14) and the ethanol rectification column steam reboiler (25) is mixed and used as the heat source of the de-light tower condensate reboiler (9) and the heat source of the ethanol rectification column feed preheater I (21).

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