Fuel alcohol preparation system combining MVR (mechanical vapor recompression) and three-tower differential pressure distillation

Abstract

The utility model relates to a fuel alcohol preparation system combining MVR and three-tower differential pressure distillation, and relates to the technical field of fuel alcohol preparation. The fuel alcohol preparation system comprises a negative-pressure mash tower system, a normal-pressure mash tower system and a pressurized fine tower system, the negative-pressure mash tower system comprises a negative-pressure mash tower, mash preheating equipment, negative-pressure mash tower reboiling equipment, a negative-pressure mash tower MVR (mechanical vapor recompression) and flash buffer equipment; the normal-pressure mash tower system comprises a normal-pressure mash tower, normal-pressure mash tower reboiling equipment and a normal-pressure mash tower MVR (mechanical vapor recompression); the pressurized rectifying tower system comprises a pressurized rectifying tower, pressurized rectifying tower reboiling equipment, a pressurized rectifying tower MVR (mechanical vapor recompression) and adsorption equipment. The fuel alcohol preparation system needs less steam consumption and circulating water consumption for preparing unit weight of fuel alcohol, and the whole system needs less equipment, so that the fuel alcohol preparation system is more energy-saving and more friendly.

Description

Technical Field

[0001] This utility model relates to the field of fuel ethanol preparation technology, and in particular to a fuel ethanol preparation system that combines MVR with three-tower differential pressure distillation. Background Technology

[0002] Fuel ethanol, as a renewable energy source, not only provides energy as an excellent fuel but also serves as an antiknock agent for gasoline. By 2023, my country's demand for fuel ethanol was approximately 12 million tons, with fermentation accounting for about 97% of production (the synthesis method using direct ethylene hydration accounted for about 3%), making it the mainstream fuel ethanol production process. However, existing systems and methods for producing fuel ethanol based on fermented mash mostly suffer from the following drawbacks: 1. High steam consumption, circulating water consumption, and electricity consumption per unit weight of product; 2. When using gradient distillation, the entire production system requires a large number of equipment and has a complex process flow. Utility Model Content

[0003] To address the aforementioned issues, this invention provides a fuel ethanol preparation system that combines MVR with three-tower differential pressure distillation. This system requires less steam and circulating water to produce a unit weight of fuel ethanol, and the number of devices required is also reduced, making it more energy-efficient.

[0004] To achieve the above objectives, this utility model provides a fuel alcohol preparation system that combines MVR with three-tower differential pressure distillation, including a negative pressure mashing tower system, an atmospheric pressure mashing tower system, and a pressurized refining tower system;

[0005] The negative pressure mash tower system includes: a negative pressure mash tower, a mash preheating device, a negative pressure mash tower reboiling device, a negative pressure mash tower MVR, and a flash buffer device;

[0006] The atmospheric pressure mash tower system includes: an atmospheric pressure mash tower, an atmospheric pressure mash tower reboiler, and an atmospheric pressure mash tower MVR;

[0007] The pressurized purification tower system includes: a pressurized purification tower, a pressurized purification tower reboiler, a pressurized purification tower MVR, and an adsorption device.

[0008] In one embodiment, the mash preheating device, the negative pressure mash tower, and the negative pressure mash tower MVR are sequentially fluidly connected; the negative pressure mash tower MVR is connected to the atmospheric pressure mash tower reboiling device and the pressurized refining tower reboiling device, respectively; the flash evaporation buffer device is connected to the pressurized refining tower reboiling device, the negative pressure mash tower reboiling device, and the atmospheric pressure mash tower, respectively; the mash preheating device is used to gradually increase the temperature of the fermented and mature mash; the negative pressure mash tower reboiling device is used to heat the negative pressure mash tower.

[0009] In one embodiment, the atmospheric pressure mash tower reboiler is used to heat the atmospheric pressure mash tower, which is connected to the pressurized refiner tower via the atmospheric pressure mash tower MVR.

[0010] In one embodiment, the pressurized purification tower, the pressurized purification tower MVR, and the adsorption device are sequentially fluidly connected. The adsorption device and the pressurized purification tower are respectively connected to the negative pressure mash tower reboiling device. The pressurized purification tower reboiling device is used to heat the pressurized purification tower.

[0011] In one embodiment, the mash preheating equipment includes: a primary mash preheater, a secondary mash preheater, and a tertiary mash preheater connected in sequence in fluid communication; the negative pressure mash tower reboiling equipment includes: a first set of negative pressure mash tower reboilers, a second set of negative pressure mash tower reboilers, and a third set of negative pressure mash tower reboilers; the flash evaporation buffer equipment includes: a negative pressure mash tower flash tank, a negative pressure mash tower buffer tank, and a negative pressure mash tower pressurization pump.

[0012] In one embodiment, the atmospheric pressure mash reboiler includes an atmospheric pressure mash reboiler.

[0013] In one embodiment, the pressurized reboiler equipment includes: a first set of pressurized reboilers and a second set of pressurized reboilers; the adsorption equipment includes: a plurality of molecular sieve adsorption devices.

[0014] In one embodiment, the three-stage preheater of mash is connected to the negative pressure mash tower, and the bottom of the negative pressure mash tower is connected to the first-stage preheater of mash.

[0015] The negative pressure mash tower MVR, the pressurized refining tower with one set of reboilers, and the flash tank are sequentially fluidly connected. The flash tank is connected to the buffer tank and the three sets of reboilers of the negative pressure mash tower. The three sets of reboilers of the negative pressure mash tower are connected to the buffer tank. The buffer tank, the pressurized pump, and the atmospheric pressure mash tower are sequentially fluidly connected.

[0016] The bottom of the atmospheric pressure mash tower and the bottom of the pressurized refining tower are connected to the three-stage preheater of the mash.

[0017] In one embodiment, the pressurized distillation column is connected to the second set of reboilers of the pressurized distillation column, and steam provides a heat source for the pressurized distillation column through the second set of reboilers.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention relates to a fuel ethanol preparation system that combines MVR (Mechanical Vapor Reduction) with three-tower differential pressure distillation. This system requires less steam and circulating water to produce a unit weight of fuel ethanol, and requires fewer pieces of equipment, making it more energy-efficient. The system cleverly utilizes the alcohol vapor generated by MVR compression at each stage and the temperature gradient at each node. While producing fuel ethanol, it also utilizes the heat energy contained within the vapor to provide a heat source for the negative pressure mashing tower, the atmospheric pressure mashing tower, and the pressurized refining tower. Furthermore, through optimized design, the high-temperature, high-pressure steam provided by the MVR at each stage is precisely matched to the reboiler requirements of each tower. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the fuel alcohol preparation system of the present invention, which combines MVR with three-tower differential pressure distillation. In the diagram, 1 is a negative pressure mashing tower, 2 is an atmospheric pressure mashing tower, 3 is a pressurized refining tower, 4 is a primary preheater for the mash, 5 is a secondary preheater for the mash, 6 is a tertiary preheater for the mash, 7 is a first-stage reboiler for the negative pressure mashing tower, 8 is a second-stage reboiler for the negative pressure mashing tower, 9 is a third-stage reboiler for the negative pressure mashing tower, 10 is a pressurization pump for the negative pressure mashing tower, 11 is a reboiler for the atmospheric pressure mashing tower, and 12 is a pressurized... 13 is a reboiler for the refining tower, 14 is a flash tank for the negative pressure mash tower, 15 is a buffer tank for the negative pressure mash tower, 16 is a negative pressure mash tower MVR, 17 is an atmospheric pressure mash tower MVR, 18 is a fusel oil separator, 19 is a pressurized refining tower MVR, 20 is a molecular sieve adsorption device, 21 is the source of fermentation mash, 22 is the lees treatment system, 23 is the finished alcohol storage tank, 24 is the wastewater treatment system, 25 is the condensate return system, and 26 is the source of steam. Detailed Implementation

[0021] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0022] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0024] source:

[0025] Unless otherwise specified, all materials and parts used in this embodiment are commercially available; unless otherwise specified, all experimental methods are conventional experimental methods in this field.

[0026] Example 1

[0027] A fuel alcohol preparation system that combines MVR with three-tower differential pressure distillation.

[0028] The fuel ethanol production system is as follows Figure 1 As shown, it includes a negative pressure mashing tower system, an atmospheric pressure mashing tower system, and a pressurized refining tower system.

[0029] The negative pressure mash tower system includes: a negative pressure mash tower, mash preheating equipment, a negative pressure mash tower reboiling equipment, a negative pressure mash tower MVR (Medium-Volume Recirculation) system, and a flash buffer system. In this embodiment, the aforementioned mash preheating equipment includes: a primary mash preheater, a secondary mash preheater, and a tertiary mash preheater connected in sequence in fluid communication; the aforementioned negative pressure mash tower reboiling equipment includes: a first set of reboilers, a second set of reboilers, and a third set of reboilers; and the aforementioned flash buffer system includes: a negative pressure mash tower flash tank, a negative pressure mash tower buffer tank, and a negative pressure mash tower pressurization pump.

[0030] The atmospheric mash tower system includes: an atmospheric mash tower, an atmospheric mash tower reboiler, and an atmospheric mash tower MVR. In this embodiment, the atmospheric mash tower reboiler includes: an atmospheric mash tower reboiler.

[0031] The pressurized purification tower system includes: a pressurized purification tower, a pressurized purification tower reboiler, a pressurized purification tower MVR, and an adsorption device. In this embodiment, the pressurized purification tower reboiler includes: one set of pressurized purification tower reboilers and two sets of pressurized purification tower reboilers; the adsorption device includes: two sets of molecular sieve adsorption devices connected in parallel.

[0032] The mash preheating equipment, negative pressure mash tower, and negative pressure mash tower MVR are sequentially fluidly connected. The bottom of the negative pressure mash tower is connected to the first-stage mash preheater. The negative pressure mash tower MVR is connected to the reboiler of the atmospheric pressure mash tower and a set of reboilers in the pressurized refining tower. The flash evaporator, buffer tank, pressurized pump, and atmospheric pressure mash tower are sequentially fluidly connected. Simultaneously, the flash evaporator is connected to a set of reboilers in the pressurized refining tower and three sets of reboilers in the negative pressure mash tower, and the buffer tank is connected to the three sets of reboilers in the negative pressure mash tower.

[0033] The atmospheric pressure mash tower is connected to the pressurized refining tower via the atmospheric pressure mash tower MVR, and the bottom of the atmospheric pressure mash tower is connected to the three-stage preheater of the mash liquid.

[0034] The pressurized refining tower, the pressurized refining tower MVR, and the adsorption unit are sequentially fluidly connected. The adsorption unit is connected to the first set of reboilers in the negative pressure mash tower, and the pressurized refining tower is connected to the second set of reboilers in the negative pressure mash tower. The second set of reboilers in the pressurized refining tower is connected to the first set of reboilers to heat the pressurized refining tower. Steam enters the second set of reboilers to provide a heat source for the pressurized refining tower, and then forms condensate for reflux. The bottom of the pressurized refining tower is connected to the three-stage preheater of the mash.

[0035] Example 2

[0036] A method for preparing fuel alcohol by combining MVR with three-tower differential pressure distillation.

[0037] I. Negative pressure distillation.

[0038] The fermented mash (material temperature 32℃) passes through a 4-stage preheater (material temperature rises to 61℃), a 5-stage preheater (material temperature rises to 64℃), and a 6-stage preheater (material temperature rises to 68.6℃). Then, it enters a 1-negative pressure mash column (top pressure: 30kPa, temperature 63.4℃; bottom pressure: 45kPa, temperature 78.7℃) for negative pressure distillation to separate the fermented mash. In the negative pressure mash column... The bottom material is heated by three reboilers: 7-1 (heat source: latent heat of the material outlet from the 20-molecular sieve adsorption device (116℃)), 8-2 (heat source: latent heat of the refluxed alcohol vapor from the top of the 3-pressurized refiner (85℃)), and 9-3 (heat source: latent heat of the material outlet from the 16-negative pressure mash tower MVR (94.9℃)). The alcohol vapor rises and separates from the mash, resulting in negative pressure alcohol vapor and negative pressure waste. The negative pressure waste (i.e., waste mash) is discharged from the bottom of the 1-negative pressure mash tower, and after heat exchange in the 4-mash primary preheater, it enters the distiller's grains treatment system. The rising negative pressure alcohol vapor enters the 16-negative pressure mash tower MVR for compression, resulting in negative pressure compressed alcohol vapor. The negative pressure alcohol gas generated by the 1-negative pressure mashing tower enters the 16-negative pressure mashing tower MVR for compression, which increases the material pressure of the negative pressure compressed alcohol gas from 30kPa to 290kPa and the temperature from 63.4℃ to 135.4℃.

[0039] II. Atmospheric pressure distillation.

[0040] The compressed alcohol vapor after MVR compression enters the reboiler of the 11-atmospheric pressure mash tower and the first set of reboilers of the 12-pressurized refiner tower respectively to heat the bottom materials of the 2-atmospheric pressure mash tower and the 3-pressurized refiner tower. Then, it enters the flash tank to reduce the material pressure to 150 kPa and the temperature to 94.9℃, resulting in flash liquid and flash steam. The flash liquid enters the buffer tank of the 15-negative pressure mash tower, and the flash steam enters the three sets of reboilers of the 9-negative pressure mash tower for heat exchange before entering the buffer tank of the 15-negative pressure mash tower. The materials in the buffer tank of the 15-negative pressure mash tower are pumped together into the 2-atmospheric pressure mash tower for separation.

[0041] 2-Ambient pressure mash tower (top pressure: 100kPa, temperature 82.5℃; bottom pressure: 130kPa, temperature 107.2℃) The bottom material is heated by a portion of the crude alcohol gas compressed by the 16-negative pressure mash tower MVR. The alcohol gas rises, resulting in higher concentrations of atmospheric pressure alcohol gas and atmospheric pressure waste.

[0042] 2. Atmospheric pressure alcohol vapor from the top of the atmospheric pressure mash tower is compressed into atmospheric pressure compressed alcohol vapor via MVR compression in the 17-atmospheric pressure mash tower. This increases the material pressure of the compressed alcohol vapor from 100 kPa to 160 kPa and the temperature from 82.5℃ to 108.3℃ before entering the 3-pressurized refining tower. The atmospheric pressure waste at the bottom of the tower, along with the pressurized waste at the bottom of the 3-pressurized refining tower, enters the 6-mash liquor three-stage preheater. After exchanging heat with the fermentation mash liquor, it enters the wastewater treatment system for further processing.

[0043] III. Pressure distillation.

[0044] 3-Pressurized Refining Column (Top pressure: 135 kPa, temperature 85.5℃; Bottom pressure: 165 kPa, temperature 110.5℃) The bottom material is heated by the latent heat of the crude alcohol vapor and the latent heat of the vapor after compression by the MVR in the 16-Negative Pressure Mashing Column. The alcohol vapor at the top of the column enters the second set of reboilers in the 8-Negative Pressure Mashing Column for condensation and reflux. The alcohol is gradually concentrated in the 3-Pressurized Refining Column. When the alcohol reaches a concentration of 95% (v / v), it enters the 19-Pressurized Refining Column MVR for compression (from alcohol vapor at absolute pressure of 135 kPa and temperature of 85.5℃ to alcohol vapor at 260 kPa and temperature of 116℃) to obtain pressurized compressed alcohol vapor. Then it enters the 20-Molecular sieve adsorption device for adsorption and dehydration. The pressurized waste material at the bottom of the column and the atmospheric waste material at the bottom of the 2-Atmospheric Pressure Mashing Column enter the 6-Mashing Liquid Three-Stage Preheater to exchange heat with the fermentation mashing liquid and then enter the wastewater treatment system for treatment.

[0045] The pressurized alcohol vapor enters a 20-molecular sieve adsorption device for adsorption and dehydration. After passing through a 7-negative pressure mash tower with a set of reboilers and a 5-mash liquid primary preheater for heat exchange, it enters the finished alcohol storage for sale.

[0046] Experimental Example

[0047] Similarly, in response to various shortcomings of traditional three-tower, three-effect distillation equipment and processes, such as: excessively high temperature at the bottom of the combined tower leading to denaturation of the lees protein and coking of the material causing equipment blockage; and low pressure at the top of the combined tower resulting in poor dehydration of the alcohol vapor entering the molecular sieve, thus leading to a high water content in the fuel alcohol, some researchers have proposed a double-coarse, double-refining, four-tower, four-effect energy-saving distillation equipment and process for producing fuel alcohol (see CN108558602A for details).

[0048] This case takes a different approach, using MVR combined with three-tower differential pressure distillation technology as a foundation. It cleverly utilizes the alcohol vapor generated by MVR compression at each stage and the temperature gradients at each node to simultaneously produce fuel ethanol and provide a heat source for the negative pressure mashing tower, atmospheric pressure mashing tower, and pressurized refining tower. Furthermore, through optimized design of the fuel ethanol production system, the high-temperature, high-pressure steam provided by the MVR at each stage is precisely matched with the reboiler requirements of each tower, achieving efficient heat transfer and utilization and overcoming technical challenges related to heat balance and distribution, and pressure and temperature matching.

[0049] The technical effects of this case are compared with those of the publicly disclosed double-roughening, double-refining, four-tower, four-effect energy-saving distillation apparatus, as detailed below:

[0050] Table 1 Comparison of Technical Effects

[0051]

[0052] It is evident that, compared to the publicly disclosed dual-coarse, dual-refining, four-tower, four-effect energy-saving distillation apparatus and process, this invention also solves the problems existing in the traditional three-tower, three-effect distillation process. The bottom temperature of the atmospheric pressure crude distillation tower in this invention is 107.2℃, lower than the 120℃ in the traditional three-tower, three-effect distillation process; the vapor pressure of the molecular sieve adsorber is higher, reducing the water content of the fuel ethanol. Furthermore, this invention reduces the steam consumption per ton of product (reduced to 0.35t / t, significantly lower than the traditional process) and the circulating water consumption per ton of product (reduced to 60t / t, saving water resources). Although the electricity consumption per ton of product increases, this increased electricity cost can be completely covered by the savings in steam and condensate costs, with a surplus. Compared to the four-tower, four-effect distillation process, MVR and three-tower differential pressure distillation perform better in terms of steam and circulating water consumption.

[0053] Furthermore, combining MVR technology with a three-tower differential pressure distillation system creates a more streamlined production process. By reducing the number of towers and lowering the pressure and temperature of each tower, it is more energy-efficient and reduces investment costs and operational risks.

[0054] Specifically, this invention reduces the number of distillation towers (to three), and the operating conditions of each tower are lower than those in existing three-tower differential pressure distillation technologies, with lower top pressure, top temperature, and bottom temperature. For example, in Example 1, the negative pressure mash tower has an absolute pressure of 30 kPa, a top temperature of 63.4°C, and a bottom temperature of 78.7°C; the atmospheric pressure mash tower has an absolute pressure of 100 kPa, a top temperature of 82.5°C, and a bottom temperature of 107.2°C; and the pressurized refining tower has an absolute pressure of 135 kPa, a top temperature of 85.5°C, and a bottom temperature of 110.5°C.

[0055] Meanwhile, this invention utilizes multiple heat sources, including MVR steam, vapor from the top of the pressurized refiner, and finished fuel alcohol vapor, to heat the negative-pressure mash tower, atmospheric-pressure mash tower, and pressurized refiner. The crude alcohol vapor compressed by the MVR in the negative-pressure mash tower prioritizes the heat source needs of the negative-pressure and atmospheric-pressure mash towers. The insufficient heat source in the pressurized refiner is regulated by steam, thus achieving a multi-heat source heating and thermal coupling system. Furthermore, the lees and waste liquid at the bottom of the negative-pressure, atmospheric-pressure, and pressurized refiner towers are used to preheat the fermentation mash, significantly improving energy utilization efficiency. The flash evaporator in the negative-pressure mash tower flashes the steam after MVR compression and heat exchange, recovering some heat energy for use in the reboiler of the negative-pressure mash tower, further optimizing heat energy utilization. The pressurized purification tower uses MVR compression to increase the temperature and pressure of the alcohol vapor, replacing fresh steam and meeting the requirements of molecular sieve adsorption equipment. Given the global energy system's transition from fossil fuels to renewable energy and the significant changes in the energy use patterns of the processing industry, the adoption of electricity instead of steam in this section is of positive significance.

[0056] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A fuel ethanol preparation system combining MVR and three-tower differential pressure distillation, characterized in that, This includes negative pressure mashing tower systems, atmospheric pressure mashing tower systems, and pressurized refining tower systems; The negative pressure mash tower system includes: a negative pressure mash tower, a mash preheating device, a negative pressure mash tower reboiling device, a negative pressure mash tower MVR, and a flash buffer device; The atmospheric pressure mash tower system includes: an atmospheric pressure mash tower, an atmospheric pressure mash tower reboiler, and an atmospheric pressure mash tower MVR; The pressurized purification tower system includes: a pressurized purification tower, a pressurized purification tower reboiler, a pressurized purification tower MVR, and an adsorption device.

2. The fuel ethanol preparation system according to claim 1, characterized in that, The mash preheating device, the negative pressure mash tower, and the negative pressure mash tower MVR are sequentially fluidly connected; the negative pressure mash tower MVR is connected to the atmospheric pressure mash tower reboiling device and the pressurized refining tower reboiling device respectively; the flash evaporation buffer device is connected to the pressurized refining tower reboiling device, the negative pressure mash tower reboiling device, and the atmospheric pressure mash tower respectively; the mash preheating device is used to gradually increase the temperature of the fermented and mature mash; the negative pressure mash tower reboiling device is used to heat the negative pressure mash tower.

3. The fuel ethanol preparation system according to claim 1, characterized in that, The atmospheric pressure mash tower reboiler is used to heat the atmospheric pressure mash tower, and the atmospheric pressure mash tower is connected to the pressurized refining tower through the atmospheric pressure mash tower MVR.

4. The fuel ethanol preparation system according to claim 1, characterized in that, The pressurized purification tower, the pressurized purification tower MVR, and the adsorption device are sequentially fluidly connected. The adsorption device and the pressurized purification tower are respectively connected to the negative pressure mash tower reboiling device. The pressurized purification tower reboiling device is used to heat the pressurized purification tower.

5. The fuel ethanol preparation system according to any one of claims 1-4, characterized in that, The mash preheating equipment includes: a primary mash preheater, a secondary mash preheater, and a tertiary mash preheater connected in sequence; the negative pressure mash tower reboiling equipment includes: a first set of negative pressure mash tower reboilers, a second set of negative pressure mash tower reboilers, and a third set of negative pressure mash tower reboilers; the flash evaporation buffer equipment includes: a negative pressure mash tower flash tank, a negative pressure mash tower buffer tank, and a negative pressure mash tower pressurization pump.

6. The fuel ethanol preparation system according to claim 5, characterized in that, The atmospheric pressure mash reboiler equipment includes: an atmospheric pressure mash reboiler.

7. The fuel ethanol preparation system according to claim 6, characterized in that, The pressurized reboiler equipment includes: a first set of pressurized reboilers and a second set of pressurized reboilers; the adsorption equipment includes: several molecular sieve adsorption devices.

8. The fuel ethanol preparation system according to claim 7, characterized in that, The three-stage preheater for mash is connected to the negative pressure mash tower, and the bottom of the negative pressure mash tower is connected to the first-stage preheater for mash. The negative pressure mash tower MVR, the pressurized refining tower with one set of reboilers, and the flash tank are sequentially fluidly connected. The flash tank is connected to the buffer tank and the three sets of reboilers of the negative pressure mash tower. The three sets of reboilers of the negative pressure mash tower are connected to the buffer tank. The buffer tank, the pressurized pump, and the atmospheric pressure mash tower are sequentially fluidly connected. The bottom of the atmospheric pressure mash tower and the bottom of the pressurized refining tower are connected to the three-stage preheater of the mash.

9. The fuel ethanol preparation system according to claim 7, characterized in that, The pressurized purification tower is connected to the second set of reboilers of the pressurized purification tower, and steam provides a heat source for the pressurized purification tower through the second set of reboilers.

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