Seven-column three-effect distillation dehydration system and method for preparing anhydrous ethanol from industrial off-gas fermentation broth

Abstract

The application discloses a seven-tower three-effect distillation dehydration system and method for preparing anhydrous ethanol from industrial tail gas fermentation mash. The system comprises a thick mash tower, a clear mash tower A, a clear mash tower B, a de-aldehyde tower, a water washing tower, a rectification tower and a de-methanol tower. The preheated industrial tail gas fermentation thick mash liquid is introduced into the thick mash tower after removing most of the non-condensable gas through a thick liquid degassing tank, and the crude wine obtained after treatment is introduced into the de-aldehyde tower, the water washing tower, the rectification tower and the de-methanol tower in sequence. The preheated industrial tail gas fermentation clear mash liquid is introduced into the clear mash tower A and the clear mash tower B after removing most of the non-condensable gas through a clear liquid degassing tank, and the crude wine obtained after treatment is introduced into the de-aldehyde tower, the water washing tower, the rectification tower and the de-methanol tower in sequence. The de-methanol tower is introduced into a molecular sieve dehydration device after treatment, and anhydrous ethanol of superior grade is obtained through condensation and cooling. The application forms a distillation dehydration system and process route for preparing anhydrous ethanol from industrial tail gas fermentation mash, has high product recovery rate, and the prepared anhydrous ethanol has high purity.

Description

Technical Field

[0001] This invention belongs to the field of ethanol distillation preparation technology. It uses industrial waste gas from steel and other industries to prepare high-grade anhydrous ethanol through biological fermentation. In particular, it relates to a seven-tower triple-effect distillation and dehydration system and method for preparing anhydrous ethanol from industrial waste gas fermentation broth. Background Technology

[0002] Industries such as steel, metallurgy, and calcium carbide generate large amounts of CO / CO2-rich industrial waste gas during production. Currently, the main methods for utilizing this waste gas are combustion heating or power generation, which are inefficient and have low economic value. Furthermore, the combustion of waste gas produces significant amounts of CO2 and NOx pollutants, resulting in high pollution control costs. Therefore, finding a new and economically viable way to utilize industrial waste gas effectively reduces CO2 emissions.

[0003] Ethanol, as an important basic chemical raw material, is also a globally recognized renewable energy source that can replace traditional fossil fuels. Most domestic bioethanol companies still use first-generation technology to produce grain-based ethanol, which relies heavily on grain and limits ethanol production growth. Summary of the Invention

[0004] According to one embodiment of the present invention, the object is to provide a novel system (seven-tower triple-effect distillation and dehydration system) and method for preparing anhydrous ethanol using industrial tail gas fermentation mash, so as to overcome the limitations of existing ethanol preparation technologies.

[0005] The above objective can be achieved through the following technical solutions:

[0006] According to one aspect of the present invention, a seven-tower triple-effect distillation and dehydration system for preparing anhydrous ethanol from industrial tail gas fermentation mash is provided, comprising: a concentrated mash tower, a clarified mash tower A, a clarified mash tower B, a dealdehyde tower, a water washing tower, a rectification tower, and a methanol removal tower; wherein,

[0007] The concentrated mash tower is connected in sequence to a concentrated liquid degassing tank and a two-stage concentrated liquid heat exchanger before the feed inlet. After preheating, the industrial tail gas fermentation concentrated mash enters the concentrated mash tower after most of the non-condensable gases are removed by the concentrated liquid degassing tank. The top of the concentrated mash tower is connected to the heat source inlet of the first-stage concentrated liquid heat exchanger, and the heat source outlet of the first-stage concentrated liquid heat exchanger is connected to two condensers in sequence. The crude liquor after heat exchange and condensation of the top vapor enters the concentrated mash tower reflux tank and then enters the crude alcohol tank from the concentrated mash tower reflux tank. The non-condensable gases are pumped out of the device by a vacuum pump.

[0008] The feed inlets of the fermentation towers A and B are connected to a degassing tank for the clear liquid and a two-stage clear liquid heat exchanger. After preheating, the fermented industrial tail gas clear mash is degassed by the clear liquid degassing tank to remove most of the non-condensable gases before entering the fermentation towers A and B respectively. The top of the fermentation tower A is connected to a three-stage condenser. The crude liquor after condensation of the top vapor enters the reflux tank of the fermentation tower A and then enters the crude alcohol tank from the reflux tank of the fermentation tower A. The non-condensable gases are pumped out by a vacuum pump. The top vapor of the fermentation tower B heats the reboiler of the fermentation tower A. The condensed crude liquor then enters the reflux tank of the fermentation tower B and then enters the crude alcohol tank from the reflux tank of the fermentation tower B.

[0009] The crude alcohol tank is connected before the inlet of the aldehyde removal tower, which receives the crude alcohol from the tank and removes acetaldehyde and other low-boiling-point light components. The inlet of the water washing tower is connected to the bottom of the aldehyde removal tower and receives the crude alcohol from the bottom of the aldehyde removal tower, removing medium and low-boiling-point impurities. Two heat exchangers are connected in sequence before the inlet of the distillation tower. The diluted alcohol from the bottom of the water washing tower is preheated in two stages before entering the distillation tower for processing. The inlet of the methanol removal tower is connected to the top of the distillation tower and receives the alcohol from the top of the distillation tower, removing methanol and low-boiling-point light components. The bottom of the methanol removal tower is also connected to a molecular sieve dehydration device, which receives the methanol-removed alcohol from the bottom of the tower and dehydrates it, condensing and cooling it to obtain anhydrous ethanol.

[0010] Optionally, each column bottom is equipped with a reboiler; each column is equipped with a reflux tank, after which the crude wine is refluxed into the reflux tank and then collected into the crude alcohol tank, and the steam from the top of each column is heated and then refluxed into the corresponding reflux tank.

[0011] Optionally, the reboiler of the distillation column is heated by steam; the reboiler of the clear mash column A is connected to the top of the clear mash column B, and is used to heat the column by the steam from the top of the clear mash column B, and the heated steam then flows to the reflux tank of the clear mash column B; the reboiler of the clear mash column B and the reboiler of the methanol removal column are respectively connected to the top of the distillation column, and are used to heat the column by the steam from the top of the distillation column, and the heated steam then flows back to the reflux tank of the distillation column; the reboiler of the aldehyde removal column, the reboiler of the water washing column, and the reboiler of the concentrated mash column are respectively connected to the top of the methanol removal column, and are used to heat the column by the steam from the top of the methanol removal column, and the heated steam then flows back to the reflux tank of the methanol removal column.

[0012] Optionally, the distillation column is provided with multiple fusel oil collection outlets at the upper and lower trays near the feed inlet. The fusel oil collection outlets are connected in sequence to a condenser and an oil-water separator. The top of the oil-water separator is connected to a fusel oil tank for storing the oil phase after chromatography. The bottom of the oil-water separator 25 is connected to a crude alcohol tank to return the aqueous phase to the crude alcohol tank.

[0013] Optionally, the molecular sieve dehydration device is also connected to a crude alcohol tank to condense the crude ethanol desorbed from the molecular sieve and return it to the crude alcohol tank.

[0014] Optionally, the secondary heat exchanger before the feed inlet of the distillation column uses steam condensate as a heat source.

[0015] Optionally, the distillation column bottom is connected to a flash tank, the bottom of the flash tank is connected to the heat source inlet of the first-stage heat exchanger before the feed inlet of the distillation column, and the heat source outlet of the first-stage heat exchanger is connected to the water inlet of the washing tower and the sewage treatment system respectively; the top of the flash tank is connected to the flash steam inlet of the bottom section of the clear mash column B.

[0016] Optionally, the outlets of the concentrated liquid degassing tank and the clear liquid degassing tank are also connected to condensers; the top of the formaldehyde removal tower and the top of the water washing tower are respectively connected to condensers; in the system, each condenser is also connected to a corresponding reflux tank, and after condensation by each condenser, the condensate flows back to its respective reflux tank, and the non-condensable gas is pumped out by a vacuum pump.

[0017] Optionally, the heat source inlet of the primary heat exchanger for concentrated liquid is connected to the top of the concentrated mash tower; the bottom of the concentrated mash tower is connected to the heat source inlet of the secondary heat exchanger for concentrated liquid, and the heat source outlet is connected to the protein system.

[0018] Optionally, the bottom of the clear mash tower A is connected to the heat source inlet of the first-stage clear liquid heat exchanger, the bottom of the clear mash tower B is connected to the heat source inlet of the second-stage clear liquid heat exchanger, and the heat source outlets of both the first-stage and second-stage clear liquid heat exchangers are connected to the wastewater treatment system.

[0019] According to another aspect of the present invention, the present invention provides a method for preparing anhydrous ethanol from industrial tail gas fermentation mash, wherein the method is carried out using a seven-tower triple-effect distillation and dehydration system for preparing anhydrous ethanol from industrial tail gas fermentation mash, the method comprising:

[0020] After two stages of preheating, the concentrated mash from industrial tail gas fermentation enters the concentrated liquid degassing tank. After removing most of the non-condensable gases, it enters the concentrated mash tower. The alcoholic gas distilled from the top of the concentrated mash tower undergoes one stage of heat exchange and two stages of condensation. The condensate goes to the concentrated mash tower reflux tank, and the crude liquor is taken from the concentrated mash tower reflux tank and sent to the crude alcohol tank. The non-condensable gases are pumped out of the device by a vacuum pump.

[0021] After two stages of preheating, the fermented mash from industrial tail gas enters the degassing tank to remove most of the non-condensable gases, and then enters mash towers A and B respectively. The alcohol vapor distilled from the top of mash tower A undergoes three stages of condensation. The condensate goes to the reflux tank of mash tower A, and the crude liquor is collected from the reflux tank of mash tower A and sent to the crude alcohol tank. The non-condensable gases are pumped out of the device by a vacuum pump. The alcohol vapor distilled from the top of mash tower B is condensed and sent to the reflux tank of mash tower B, and the crude liquor is collected from the reflux tank of mash tower B and sent to the crude alcohol tank.

[0022] The crude liquor in the crude alcohol tank enters the dealdehyde removal tower to remove acetaldehyde and other low-boiling-point light components. The crude liquor collected from the bottom of the tower is sent to the water washing tower. Water is added to the water washing tower to remove medium and low-boiling-point light components by increasing the distillation coefficient of impurities and ethanol. The light liquor collected from the bottom of the tower is preheated in two stages and then sent to the rectification tower. The rectification tower removes tail-stage impurities and a large amount of water from the light liquor. The alcohol collected from the reflux tank of the rectification tower is sent to the methanol removal tower. The methanol removal tower removes methanol and low-boiling-point light components from the alcohol. The methanol-removed alcohol collected from the bottom of the tower is sent to the molecular sieve dehydration unit. After dehydration, it is condensed and cooled to obtain superior grade anhydrous ethanol.

[0023] Optionally, the concentrated mash tower is under negative pressure, the clear mash tower A is under negative pressure, the clear mash tower B is under normal pressure, the dealdehyde tower is under negative pressure, the water washing tower is under negative pressure, the distillation tower is under positive pressure, and the methanol removal tower is under positive pressure.

[0024] Optionally, it also includes: using steam to heat the reboiler of the distillation column; using the overhead steam from the clear mash column B to heat the reboiler of the clear mash column A, and after heating, the steam is refluxed to the reflux tank of the clear mash column B, with the liquid phase portion refluxed back to the top of the clear mash column B and the portion collected into the crude alcohol tank; using the overhead steam from the distillation column to heat the reboiler of the clear mash column B and the reboiler of the methanol removal column, and after heating, the steam is refluxed back to the reflux tank of the distillation column, with the portion refluxed back to the top of the distillation column and the portion collected into the methanol removal column; using the overhead steam from the methanol removal column to heat the reboiler of the aldehyde removal column, the reboiler of the water washing column, and the reboiler of the concentrated mash column, and after heating, the steam is refluxed back to the reflux tank of the methanol removal column, with the portion refluxed back to the top of the methanol removal column and the portion collected.

[0025] Optionally, it also includes: collecting fusel oil from the upper and lower trays near the feed inlet of the distillation column, condensing and chromatography it, sending the chromatographically separated oil phase fusel oil to the fusel oil tank for storage, and sending the chromatographically separated aqueous phase to the crude alcohol tank for recovery.

[0026] Optionally, the crude ethanol desorbed from the molecular sieve dehydration device can be condensed and returned to the crude ethanol tank for recycling.

[0027] Optionally, it also includes: flash evaporating the wastewater from the bottom of the distillation column under reduced pressure; sending the flash-evaporated wastewater as a heat source to the first-stage heat exchanger of the distillation column feed before the feed inlet to heat it; sending a portion of the heated wastewater to the washing column as the extraction water for the washing column, and sending a portion of the wastewater to the wastewater treatment system for wastewater treatment; and sending the flash vapor from the flash-evaporated wastewater to the clear mash column B as flash vapor to provide some heat to the clear mash column B.

[0028] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0029] 1) This invention establishes a distillation and dehydration system and process route for preparing anhydrous ethanol from industrial tail gas fermentation mash, which has a high product recovery rate and high purity of the prepared anhydrous ethanol.

[0030] This invention uses mature mash from the fermentation stage of the process tail gas as raw material, and divides it into two types according to the process source: concentrated mash and clear mash. Although the ethanol concentration in the two fermentation mash is basically the same, the protein particles and processing capacity are very different. This invention takes into full account the impurities contained in each mash and designs a process to address the differences in protein particles and processing capacity in the two fermentation mash. It establishes a process path with material balance and energy balance, and effectively utilizes the components in the two mash.

[0031] Unlike traditional alcohol fermentation processes, this invention uses industrial waste gas as raw material to produce ethanol, completely avoiding dependence on land for raw materials and truly achieving the development requirement of "not competing with people for food and not competing with food for land".

[0032] Unlike the traditional distillation process that uses fermentation mash from grains, fibers, etc. to prepare anhydrous ethanol, this invention uses industrial tail gas fermentation mash as raw material. The impurity components and contents in industrial tail gas fermentation and grain fermentation mash are not the same, and the process design parameters cannot be completely replicated.

[0033] 2) In this system, one distillation column is heated by steam, and the heat of the other six columns is coupled within the system, which greatly improves distillation efficiency, reduces steam consumption, and saves process energy.

[0034] Through the use of seven towers—a concentrated mash tower, a clear mash tower A, a clear mash tower B, a dealdehyde tower, a water washing tower, a distillation tower, and a methanol removal tower—the feasibility, energy consumption, and operating costs of this invention were continuously improved and optimized through process modeling and practical operation. This resulted in the development of a process for preparing anhydrous ethanol from industrial tail gas fermentation mash and a seven-tower triple-effect distillation and dehydration system.

[0035] 3) Install deaerators before the concentrated mash tower, clear mash tower A and clear mash tower B. The deaerators use negative pressure, which can remove non-condensable gases in the mash first, which is more conducive to subsequent processing.

[0036] The aldehyde removal tower, water washing tower, distillation tower, and methanol removal tower are set up sequentially. First, the aldehyde removal tower removes low-boiling-point light components (i.e., first-stage impurities) such as acetaldehyde and ethyl acetate. The water washing tower reduces the alcohol concentration by adding water. At a low alcohol concentration, the volatility coefficient of medium and low-boiling-point impurities increases. Therefore, water extraction in the water washing tower can more effectively remove medium and low-boiling-point impurities (i.e., intermediate-stage impurities) such as isopropanol. Next, the distillation tower dehydrates and removes tail-stage impurities such as butanol, pentanol, and hexanol. The high-concentration alcohol after treatment is sent to the methanol removal tower. At a high alcohol concentration, the volatility coefficient of low-boiling-point impurities such as methanol increases. The methanol removal tower removes methanol and also removes some low-boiling-point light components (i.e., first-stage impurities).

[0037] 4) Superior grade anhydrous ethanol can be prepared from industrial tail gas fermentation mash, and even extra-superior grade anhydrous ethanol can be prepared. The distillation and dehydration process of this superior grade anhydrous ethanol has not been reported at home and abroad. This invention belongs to the latest process technology and fills the technological gap at home and abroad.

[0038] 5) Fusel oil was collected near the feed inlet of the distillation column, cooled, and subjected to chromatography to obtain fusel oil. The aqueous phase after chromatography was returned to the crude alcohol tank to further improve the yield. Additionally, the crude ethanol from the molecular sieve dehydration unit was condensed and returned to the crude alcohol tank to further improve the yield.

[0039] 6) The system establishes and optimizes the heat exchange network, and the heat source for the heat exchangers is provided by the heat material inside the system, which saves energy consumption. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of a seven-tower triple-effect distillation and dehydration system for preparing anhydrous ethanol from industrial tail gas fermentation mash in one embodiment of the present invention.

[0041] Figure 2 This is a process flow diagram of preparing anhydrous ethanol from industrial tail gas fermentation mash in one embodiment of the present invention.

[0042] Figure label:

[0043] 1. Concentrated liquid primary heat exchanger, 2. Concentrated liquid secondary heat exchanger, 3. Condenser, 4. Clear liquid primary heat exchanger, 5. Clear liquid secondary heat exchanger, 6. Distillation column feed primary heat exchanger, 7. Distillation column feed secondary heat exchanger, 8. Concentrated mash column reboiler, 9. Clear mash column A reboiler, 10. Clear mash column B reboiler, 11. Dealdehyde removal column reboiler, 12. Water washing column reboiler, 13. Distillation column reboiler, 14. Demethanol removal column reboiler, 15. Concentrated mash column reflux tank, 16. Clear mash column A reflux tank, 17. Clear mash column B reflux tank, 18. Dealdehyde removal column reflux tank, 19. Water washing column reflux tank, 20. Distillation column reflux tank, 21. Demethanol removal column reflux tank, 22. Flash vapor inlet, 23. Concentrated liquid degassing tank, 24. Clear liquid degassing tank, 25. Oil-water separator. Detailed Implementation

[0044] The technical solution of the present invention will be clearly and completely described below with reference to embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0045] The raw materials for the distillation section of this invention are concentrated mash and clear mash obtained from industrial tail gas fermentation. Using these two types of mash as raw materials, and employing the seven-tower distillation and dehydration system of this invention, non-condensable gases are first removed through a degassing tank. Then, the concentrated liquid enters the concentrated mash tower, while the clear liquid enters clear mash towers A and B respectively. The treated crude liquor enters the dealdehyde removal tower to remove low-boiling-point light components such as acetaldehyde. After treatment in the dealdehyde removal tower, the crude liquor enters the water washing tower, where water is added to lower the alcohol concentration. At lower alcohol concentrations, the volatility coefficient of medium and low-boiling-point impurities increases, and the water washing tower more effectively removes these impurities. Next, it enters the rectification tower for dehydration to remove some tail-stage impurities. The high-concentration alcohol after rectification is sent to the methanol removal tower. At high alcohol concentrations, the volatility coefficient of low-boiling-point impurities such as methanol increases, removing methanol while also removing some low-boiling-point light components. Finally, superior grade anhydrous ethanol, or even extra-superior grade anhydrous ethanol far exceeding the superior grade, can be prepared. In the system of this invention, one distillation column supplies steam while seven columns operate, which greatly improves distillation efficiency and saves energy.

[0046] Figure 1 The illustration schematically depicts a seven-tower triple-effect distillation and dehydration system for preparing anhydrous ethanol from industrial waste gas fermentation mash, provided in one embodiment of the present invention. Figure 2 The diagram illustrates a process flow chart for preparing anhydrous ethanol from industrial tail gas fermentation mash in one embodiment of the present invention.

[0047] like Figure 1 As shown in the figure, the seven-tower, three-effect (distillation and thermal integration) distillation and dehydration system for preparing anhydrous ethanol from industrial tail gas fermentation mash provided in this embodiment includes: a concentrated mash tower, a clear mash tower A, a clear mash tower B, an aldehyde removal tower, a water washing tower, a distillation tower, and a methanol removal tower.

[0048] The following is combined Figure 1 and Figure 2 The system structure and method flow of this embodiment will be further explained in the order of the tower:

[0049] 1) The concentrated mash tower is connected in sequence to the concentrated liquid deaerator 23 and a two-stage concentrated liquid heat exchanger before the feed inlet. The two-stage heat exchangers are the concentrated liquid primary heat exchanger 1 and the concentrated liquid secondary heat exchanger 2. After being preheated by the alcohol vapor and mash liquid in the two-stage heat exchangers, the concentrated mash enters the concentrated liquid deaerator 23. The concentrated liquid deaerator 23 adopts negative pressure to remove most of the non-condensable gases in the mash. After deaeration, it enters the concentrated mash tower.

[0050] The top of the concentrated mash tower is connected to the heat source inlet of the first-stage concentrated liquid heat exchanger 1. The heat source outlet of the first-stage concentrated liquid heat exchanger 1 is connected to two stages of condensers 3 in sequence. Both condensers 3 are connected to the concentrated mash tower reflux tank 15. The concentrated mash tower reflux tank 15 is connected to the concentrated mash tower and the crude alcohol tank.

[0051] The concentrated mash tower operates under negative pressure. Ethanol vapor with a concentration of about 50% is distilled out from the top of the tower. After the ethanol vapor is heated by the first-stage heat exchanger, the alcohol and low-boiling-point components enter the condenser 3 for two-stage condensation. The non-condensable gas after condensation is pumped out by the vacuum pump. All the condensate is returned to the concentrated mash tower reflux tank 15. A portion of the reflux tank 15 is returned to the top of the concentrated mash tower, and the rest is taken out as crude liquor (ethanol content of about 50%) and sent to the crude alcohol tank.

[0052] In addition, the outlet of the concentrated liquid degassing tank 23 is also connected to a condenser 3, which condenses and returns the ethanol carried in the concentrated liquid degassing tank 23 to the concentrated mash tower return tank 15, and the non-condensable gas is pumped out of the device by a vacuum pump.

[0053] The inlet of the concentrated mash tower is connected to the heat source inlet of the secondary heat exchanger 2, and the heat source outlet is connected to the protein system. The mash liquid (containing microbial mash) collected from the tower is heated by the secondary heat exchanger 2 and then sent to the next stage, namely the protein stage.

[0054] The concentrated mash tower bottom is connected to the concentrated mash tower reboiler 8, which is connected to the top of the demethanol tower. The concentrated mash reboiler is heated by the heat from the top steam of the demethanol tower, and the top steam of the demethanol tower is condensed and sent to the demethanol tower reflux tank 21.

[0055] 2) The feed inlets of the clear mash towers A and B are connected to a clear liquid degassing tank 24 and a two-stage clear liquid heat exchanger, namely a first-stage clear liquid heat exchanger 4 and a second-stage clear liquid heat exchanger 5. After being preheated with alcohol vapor and lees by the two-stage heat exchangers, the clear mash enters the clear liquid degassing tank 24. The clear liquid degassing tank 24 operates under negative pressure. After most of the non-condensable gases are removed by the clear liquid degassing tank 24, the mash is sent to clear mash towers A and B respectively.

[0056] 3) The top of the clear mash tower A is connected to a three-stage condenser 3 in sequence. Alcohol and low-boiling-point components enter the condenser 3 for condensation. Non-condensable gases are discharged by a vacuum pump. All three-stage condensers 3 are connected to the clear mash tower A reflux tank 16. All the condensate enters the clear mash tower A reflux tank 16. The clear mash tower A reflux tank 16 is connected to the clear mash tower A and the crude alcohol tank.

[0057] The clear mash tower A operates under negative pressure. At the top of clear mash tower A, approximately 50% ethanol vapor is distilled out. After three stages of condensation, it enters the clear mash tower A reflux tank 16. A portion of the vapor is collected from the reflux tank 16 and returned to the top of clear mash tower A, while the remaining portion is collected as crude liquor (approximately 50% ethanol) and sent to the crude alcohol tank.

[0058] The bottom of the clear mash tower A is connected to the reboiler 9 of the clear mash tower A. The reboiler 9 of the clear mash tower A is connected to the top of the clear mash tower B. The reboiler 9 of the clear mash tower A is heated by the heat of the steam at the top of the clear mash tower B, and the steam at the top of the tower is condensed and refluxed back to the reflux tank 17 of the clear mash tower B after being heated.

[0059] The bottom of the fermentation tower A is connected to the heat source inlet of the primary heat exchanger 4 for the clear liquid, and the heat source outlet of the primary heat exchanger 4 for the clear liquid is connected to the sewage treatment system. The wastewater collected from the bottom of the fermentation tower A exchanges heat with the clear liquid through the primary heat exchanger 4 for the clear liquid and then goes to the next stage, namely the sewage treatment stage. Some of it can be reused in the fermentation system.

[0060] 4) The top of the clear mash tower B is connected to the reboiler 9 of the clear mash tower A, and is connected to the reflux tank 17 of the clear mash tower B. The reflux tank 17 of the clear mash tower B is connected to the clear mash tower B and the crude alcohol tank.

[0061] The clear mash tower B operates at atmospheric pressure. At the top of clear mash tower B, approximately 50% ethanol vapor is distilled out, providing heat to the reboiler 9 of clear mash tower A while simultaneously condensing and cooling it. The condensate enters the reflux tank 17 of clear mash tower B. A portion of the reflux from clear mash tower B is returned to the top of clear mash tower B, while the remainder is collected as crude liquor (approximately 50% ethanol) and sent to the crude alcohol tank.

[0062] The reboiler 10 of the clear mash tower B is connected to the top of the distillation tower and is heated by the heat of the steam at the top of the distillation tower; and the heated steam at the top of the tower enters the reflux tank 20 of the distillation tower.

[0063] The bottom of the clear mash tower B is connected to the heat source inlet of the clear liquid secondary heat exchanger 5, and the heat source outlet of the clear liquid secondary heat exchanger 5 is connected to the sewage treatment system. The wastewater collected from the tower bottom exchanges heat with the clear mash feed through the clear liquid secondary heat exchanger 5 and then goes to the next stage, namely the sewage treatment stage.

[0064] 5) The reflux tanks corresponding to the concentrated mash tower, clear mash tower A, and clear mash tower B are all connected to the crude alcohol tank. A portion of the crude alcohol from the concentrated mash tower, clear mash tower A, and clear mash tower B is collected and sent to the crude alcohol tank.

[0065] The crude alcohol tank is connected to the feed inlet of the aldehyde removal tower. The crude alcohol from the crude alcohol tank is fed into the aldehyde removal tower. Low-boiling-point light components such as acetaldehyde are collected from the top of the tower, and the crude alcohol from the bottom of the tower is sent to the water washing tower. The aldehyde removal tower operates under negative pressure, which is beneficial for both the removal of light components and the balance of heat.

[0066] Two condensers 3 are connected in series at the top of the formaldehyde removal tower. The condensed liquid phase enters the formaldehyde removal tower reflux tank 18, and the non-condensable gas is pumped out of the device by a vacuum pump. A portion of the formaldehyde removal tower reflux tank 18 is collected and returned to the top of the formaldehyde removal tower, and the remainder is collected as first-stage impurities (i.e., acetaldehyde and some other low-boiling-point light components). The formaldehyde removal ethanol collected from the bottom of the tower is sent to the water washing tower.

[0067] The bottom of the dealdehyde removal tower is connected to a dealdehyde removal reboiler 11, which is connected to the top of the demethanol removal tower. The dealdehyde removal reboiler 11 is heated by the heat from the top steam of the demethanol removal tower, and the top steam is condensed and enters the demethanol removal tower reflux tank 21 after being heated.

[0068] 6) The feed inlet of the water washing tower is connected to the bottom of the dealdehyde removal tower. Two condensers 3 are connected in series at the top of the water washing tower. The condensed liquid phase enters the water washing tower reflux tank 19. The non-condensable gas is pumped out by a vacuum pump and a portion is collected from the water washing tower reflux tank 19 and returned to the top of the water washing tower. The remaining portion is used to collect intermediate impurities.

[0069] Process water is added to the top of the washing tower; the distillation column bottom wastewater (wastewater after flash steam in the bottom wastewater has been heated by a heat exchanger) is used as the extraction water for washing. A spare pipe can be reserved to connect the water inlet of the washing tower to the heat source outlet of the secondary heat exchanger 7 of the distillation column feed, and the condensate after heat exchange is used as the extraction water.

[0070] The function of the water washing tower is to extract some intermediate impurities (i.e., low-to-medium boiling point light components) by adding water. These intermediate impurities have a rectification coefficient greater than 1 at low ethanol concentrations and are collected at the top of the tower. At low ethanol concentrations, the volatility coefficient of low-to-medium boiling point impurities increases, which facilitates the separation of ethanol from impurities. The alcohol vapor at the top of the tower enters condenser 3 for condensation, and most of the condensate is refluxed. The water washing tower operates under negative pressure, which is more conducive to the removal of intermediate impurities and also further promotes heat integration.

[0071] The bottom of the water washing tower is connected to the reboiler 12, which is connected to the top of the methanol removal tower. The reboiler 12 is heated by the heat from the overhead steam of the methanol removal tower, and the heated steam condenses and enters the reflux tank 21 of the methanol removal tower. The distillate from the bottom of the tower is sent to the distillation tower.

[0072] 7) Two heat exchangers are connected sequentially before the feed inlet of the distillation column: a primary feed heat exchanger (6) and a secondary feed heat exchanger (7). The diluted liquor (approximately 15% ethanol content) taken from the bottom of the water washing column is preheated by the two heat exchangers before entering the distillation column for processing. The function of the distillation column is to dehydrate and remove tailings impurities. The positive pressure operation of the distillation column further facilitates impurity removal.

[0073] The top of the distillation column is connected to the reboiler 10 of the clear mash column B and the reboiler 14 of the methanol removal column, providing a heat source for these two units. After heating, the condensate enters the distillation column reflux tank 20. Part of the reflux is collected from the reflux tank 20 and returned to the top of the distillation column, while the remaining portion enters the methanol removal column. The distillation column reboiler 13 is heated by steam. The secondary heat exchanger 7 for the distillation column feed uses steam condensate as a heat source.

[0074] Furthermore, the distillation column is equipped with multiple fusel oil collection outlets near the feed inlet on the upper and lower trays. These outlets are sequentially connected to a condenser 3 and an oil-water separator 25. The top of the oil-water separator 25 is connected to a fusel oil tank, and the bottom is connected to a crude alcohol tank. Fusel oil is collected from different locations above and below the feed inlet of the distillation column. After being cooled by the condenser 3, the collected fusel oil is subjected to water chromatography in the oil-water separator 25. The oil phase after chromatography is sent to the fusel oil tank for storage, while the aqueous phase is returned to the crude alcohol tank, further improving the yield.

[0075] Wastewater discharged from the distillation column bottom enters a flash tank for depressurized flash evaporation. The bottom of the flash tank is connected to the heat source inlet of the first-stage heat exchanger 6 of the distillation column feed before the feed inlet of the distillation column. The heat source outlet of the first-stage heat exchanger 6 of the distillation column feed is connected to the water inlet of the washing tower and the wastewater treatment system, respectively. The top of the flash tank is connected to the flash steam inlet 22 of the clear mash tower B, thereby effectively utilizing thermal energy and reducing process energy consumption.

[0076] 8) The feed inlet of the methanol removal tower is connected to the reflux tank 20 of the distillation tower. The methanol removal tower operates under positive pressure. Its function, as the name suggests, is to remove methanol. At the same time as removing methanol, the top of the tower can also remove some of the first-stage impurities.

[0077] High-concentration alcohol (ethanol content approximately 91%) enters the methanol removal tower. At this high alcohol concentration, the volatility of low-boiling-point impurities such as methanol increases. The methanol-removed alcohol (ethanol content approximately 91.5%) is then taken from the tower bottom and fed into a dehydration unit. In this embodiment, a molecular sieve dehydration unit is used.

[0078] The bottom of the methanol stripping column is connected to the reboiler 14, which is connected to the top of the distillation column. Heat is supplied by the overhead vapor from the distillation column, and the heated vapor is then refluxed back to the distillation column reflux tank 20. High-concentration ethanol is collected from the bottom of the column and sent to the molecular sieve dehydration unit.

[0079] 9) The molecular sieve dehydration unit is connected to the bottom of the methanol removal tower to receive and process the methanol-removed ethanol from the bottom of the tower, obtaining anhydrous ethanol. The ethanol vapor after molecular sieve dehydration is condensed and cooled before being stored in a finished product tank. The quality of the obtained finished product is far superior to that of premium-grade anhydrous ethanol, reaching the level of daily chemical grade anhydrous ethanol, and the product recovery rate is greatly optimized.

[0080] The gas enters a molecular sieve dehydration device, is evaporated into alcohol vapor by an evaporator, and then superheated to 145°C before entering an adsorption tower for adsorption and dehydration. The dehydrated anhydrous alcohol vapor is then condensed and cooled before entering an anhydrous alcohol storage tank.

[0081] In addition, the molecular sieve dehydration device is also connected to a crude alcohol tank to condense the crude ethanol (i.e., the diluted liquor) desorbed from the molecular sieve and return it to the crude alcohol tank, thereby further improving the yield.

[0082] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A seven-tower triple-effect distillation and dehydration system for preparing anhydrous ethanol from industrial tail gas fermentation mash, characterized in that, include: The mash tower includes a concentrated mash tower, a clear mash tower A, a clear mash tower B, a formaldehyde removal tower, a water washing tower, a distillation tower, and a methanol removal tower; among them, The concentrated mash tower is connected in sequence to a concentrated liquid degassing tank and a two-stage concentrated liquid heat exchanger before the feed inlet. After preheating, the industrial tail gas fermentation concentrated mash enters the concentrated mash tower after most of the non-condensable gases are removed by the concentrated liquid degassing tank. The top of the concentrated mash tower is connected to the heat source inlet of the first-stage concentrated liquid heat exchanger, and the heat source outlet of the first-stage concentrated liquid heat exchanger is connected in sequence to two-stage condensers. The crude liquor after heat exchange and condensation of the top vapor enters the concentrated mash tower reflux tank and then enters the crude alcohol tank from the concentrated mash tower reflux tank. The non-condensable gases are pumped out of the device by a vacuum pump. The feed inlets of the fermentation towers A and B are connected to a degassing tank for the clear liquid and a two-stage clear liquid heat exchanger. After preheating, the fermented industrial tail gas clear mash is degassed by the clear liquid degassing tank to remove most of the non-condensable gases before entering the fermentation towers A and B respectively. The top of the fermentation tower A is connected to a three-stage condenser. The crude liquor after condensation of the top vapor enters the reflux tank of the fermentation tower A and then enters the crude alcohol tank from the reflux tank of the fermentation tower A. The non-condensable gases are pumped out by a vacuum pump. The top vapor of the fermentation tower B heats the reboiler of the fermentation tower A. The crude liquor after condensation enters the reflux tank of the fermentation tower B and then enters the crude alcohol tank from the reflux tank of the fermentation tower B. The crude alcohol tank is connected before the inlet of the aldehyde removal tower, which receives the crude alcohol from the tank and removes acetaldehyde and other low-boiling-point light components. The inlet of the water washing tower is connected to the bottom of the aldehyde removal tower and receives the crude alcohol from the bottom of the aldehyde removal tower, removing medium and low-boiling-point impurities. Two heat exchangers are connected in sequence before the inlet of the distillation tower. The diluted alcohol from the bottom of the water washing tower is preheated in two stages before entering the distillation tower for processing. The inlet of the methanol removal tower is connected to the top of the distillation tower and receives the alcohol from the top of the distillation tower, removing methanol and low-boiling-point light components. The bottom of the methanol removal tower is also connected to a molecular sieve dehydration device, which receives the methanol-removed alcohol from the bottom of the tower and dehydrates it, condensing and cooling it to obtain anhydrous ethanol.

2. The seven-tower triple-effect distillation and dehydration system for preparing anhydrous ethanol from industrial tail gas fermentation mash according to claim 1, characterized in that, Each column is equipped with a reboiler; each column is equipped with a reflux tank. After condensation, the crude wine is refluxed into the reflux tank and then collected into the crude alcohol tank. The steam from the top of each column is heated and then refluxed into the corresponding reflux tank. The distillation column reboiler is heated by steam; the clear mash column A reboiler is connected to the top of the clear mash column B, and is used to heat the column by the steam from the top of the clear mash column B, which then flows back to the reflux tank of the clear mash column B; the clear mash column B reboiler and the methanol removal column reboiler are respectively connected to the top of the distillation column, and are used to heat the column by the steam from the top of the distillation column, which then flows back to the reflux tank of the distillation column; the aldehyde removal column reboiler, the water washing column reboiler, and the concentrated mash column reboiler are respectively connected to the top of the methanol removal column, and are used to heat the column by the steam from the top of the methanol removal column, which then flows back to the reflux tank of the methanol removal column.

3. The seven-tower triple-effect distillation and dehydration system for preparing anhydrous ethanol from industrial tail gas fermentation mash according to any one of claims 1-2, characterized in that, The distillation column has multiple fusel oil collection outlets near the feed inlet on the upper and lower trays. Each fusel oil collection outlet is connected in sequence to a condenser and an oil-water separator. The top of the oil-water separator is connected to a fusel oil tank to store the oil phase after chromatography. The bottom of the oil-water separator is connected to a crude alcohol tank to return the aqueous phase to the crude alcohol tank. The molecular sieve dehydration device is also connected to a crude alcohol tank to condense the crude ethanol desorbed from the molecular sieve and return it to the crude alcohol tank.

4. The seven-tower triple-effect distillation and dehydration system for preparing anhydrous ethanol from industrial tail gas fermentation mash according to any one of claims 1-2, characterized in that, The secondary heat exchanger before the feed inlet of the distillation column uses steam condensate as a heat source. The distillation column bottom is connected to a flash tank, the bottom of which is connected to the heat source inlet of the first-stage heat exchanger before the feed inlet of the distillation column, and the heat source outlet of the first-stage heat exchanger is connected to the water inlet of the washing column and the wastewater treatment system, respectively; the top of the flash tank is connected to the flash steam inlet of the bottom section of the clear mash column B.

5. The seven-tower triple-effect distillation and dehydration system for preparing anhydrous ethanol from industrial tail gas fermentation mash according to any one of claims 1-2, characterized in that, The outlets of the concentrated liquid degassing tank and the clear liquid degassing tank are also connected to the condenser; the top of the formaldehyde removal tower and the top of the water washing tower are respectively connected to the condenser; in the system, each condenser is also connected to the corresponding reflux tank. After condensation by each condenser, the condensate flows back to its respective reflux tank, and the non-condensable gas is pumped out by the vacuum pump. The heat source inlet of the primary heat exchanger for concentrated liquid is connected to the top of the concentrated mash tower; the bottom of the concentrated mash tower is connected to the heat source inlet of the secondary heat exchanger for concentrated liquid, and the heat source outlet is connected to the protein system; The bottom of the clear mash tower A is connected to the heat source inlet of the first-stage clear liquid heat exchanger, and the bottom of the clear mash tower B is connected to the heat source inlet of the second-stage clear liquid heat exchanger. The heat source outlets of both the first-stage and second-stage clear liquid heat exchangers are connected to the wastewater treatment system.

6. A method for preparing anhydrous ethanol from industrial waste gas fermentation mash, characterized in that, The preparation of anhydrous ethanol is carried out using the seven-tower triple-effect distillation and dehydration system for preparing anhydrous ethanol from industrial tail gas fermentation mash as described in any one of claims 1-5, the method comprising: After two stages of preheating, the concentrated mash from industrial tail gas fermentation enters the concentrated liquid degassing tank. After removing most of the non-condensable gases, it enters the concentrated mash tower. The alcoholic gas distilled from the top of the concentrated mash tower undergoes one stage of heat exchange and two stages of condensation. The condensate goes to the concentrated mash tower reflux tank, and the crude liquor is taken from the concentrated mash tower reflux tank and sent to the crude alcohol tank. The non-condensable gases are pumped out of the device by a vacuum pump. After two stages of preheating, the fermented mash from industrial tail gas enters the degassing tank to remove most of the non-condensable gases, and then enters mash towers A and B respectively. The alcohol vapor distilled from the top of mash tower A undergoes three stages of condensation. The condensate goes to the reflux tank of mash tower A, and the crude liquor is collected from the reflux tank of mash tower A and sent to the crude alcohol tank. The non-condensable gases are pumped out of the device by a vacuum pump. The alcohol vapor distilled from the top of mash tower B is condensed and sent to the reflux tank of mash tower B, and the crude liquor is collected from the reflux tank of mash tower B and sent to the crude alcohol tank. The crude liquor in the crude alcohol tank enters the dealdehyde removal tower to remove acetaldehyde and other low-boiling-point light components. The crude liquor collected from the bottom of the tower is sent to the water washing tower. Water is added to the water washing tower to remove medium and low-boiling-point light components by increasing the distillation coefficient of impurities and ethanol. The light liquor collected from the bottom of the tower is preheated in two stages and then sent to the rectification tower. The rectification tower removes tail-stage impurities and a large amount of water from the light liquor. The alcohol collected from the reflux tank of the rectification tower is sent to the methanol removal tower. The methanol removal tower removes methanol and low-boiling-point light components from the alcohol. The methanol-removed alcohol collected from the bottom of the tower is sent to the molecular sieve dehydration unit. After dehydration, it is condensed and cooled to obtain superior grade anhydrous ethanol.

7. The method for preparing anhydrous ethanol from industrial tail gas fermentation mash according to claim 6, characterized in that, The concentrated mash tower is under negative pressure, the clear mash tower A is under negative pressure, the clear mash tower B is under normal pressure, the aldehyde removal tower is under negative pressure, the water washing tower is under negative pressure, the distillation tower is under positive pressure, and the methanol removal tower is under positive pressure.

8. The method for preparing anhydrous ethanol from industrial tail gas fermentation mash according to claim 6, characterized in that, This also includes: using steam to heat the reboiler of the distillation column; using the overhead steam from the clear mash column B to heat the reboiler of the clear mash column A, and after heating, the steam is refluxed to the reflux tank of the clear mash column B, with the liquid phase portion refluxed back to the top of the clear mash column B and the portion collected into the crude alcohol removal tank; using the overhead steam from the distillation column to heat the reboilers of the clear mash column B and the methanol removal column, and after heating, the steam is refluxed back to the distillation column reflux tank, with the portion refluxed back to the top of the distillation column and the portion collected into the methanol removal column; using the overhead steam from the methanol removal column to heat the reboilers of the aldehyde removal column, the water washing column, and the concentrated mash column, and after heating, the steam is refluxed back to the methanol removal column reflux tank, with the portion refluxed back to the top of the methanol removal column and the portion collected.

9. The method for preparing anhydrous ethanol from industrial tail gas fermentation mash according to claim 6, characterized in that, Also includes: Fusel oil is collected from the upper and lower trays near the feed inlet of the distillation column, and then condensed and chromatographically separated. The oil phase of the chromatographically separated fusel oil is sent to the fusel oil tank for storage, and the aqueous phase after chromatography is sent to the crude alcohol tank for recovery. The crude ethanol decomposed by the molecular sieve dehydration device is condensed and returned to the crude ethanol tank for recycling.

10. The method for preparing anhydrous ethanol from industrial tail gas fermentation mash according to claim 6, characterized in that, Also includes: The wastewater in the bottom of the distillation column is subjected to reduced pressure flash evaporation; the flash evaporation wastewater is then used as a heat source to supply heat to the first-stage heat exchanger of the distillation column feed before the feed inlet. After heating, part of the wastewater is sent to the water washing tower as the extraction water for the water washing tower, and part of the wastewater is sent to the sewage treatment system for sewage treatment. The flash steam from the wastewater after flash evaporation is sent to the clear mash tower B as flash steam to provide some heat to the clear mash tower B.

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