Method and system for preparing fuel alcohol by combining MVR (mechanical vapor recompression) and three-tower differential pressure distillation

Abstract

The invention relates to a fuel alcohol preparation method and 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] The invention relates to the technical field of fuel alcohol preparation, and in particular to a fuel alcohol preparation method and system using MVR combined with three-tower differential pressure distillation. Background Art

[0002] As a renewable energy source, fuel alcohol can not only be used as an excellent fuel to provide energy, but also as a gasoline anti-knock agent. By 2023, my country's demand for fuel alcohol will be about 12 million tons, and the fermentation method will account for about 97% of the fuel alcohol production (mainly using the synthesis method of ethylene direct hydration process, accounting for about 3%), becoming the mainstream of fuel alcohol preparation technology. However, most of the existing systems and methods for preparing fuel alcohol based on fermented mature mash have the following defects: 1. The steam consumption, circulating water consumption, and electricity consumption per unit weight of product are high; 2. When using the gradient distillation method for preparation, the entire production system needs to introduce a large number of equipment and the system flow is complicated. Summary of the invention

[0003] In view of the above problems, the present invention provides a fuel alcohol preparation system combining MVR and three-tower differential pressure distillation. The fuel alcohol preparation system requires less steam consumption and circulating water consumption to prepare unit weight of fuel alcohol, and the number of equipment required to be introduced into the entire system is relatively small, which is more friendly to energy saving.

[0004] In order to achieve the above object, the present invention provides a fuel alcohol preparation system combining MVR with three-tower differential pressure distillation, comprising a negative pressure mash tower system, a normal pressure mash tower system, and a pressurized finishing 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 mash tower system comprises: an atmospheric mash tower, an atmospheric mash tower reboiler, and an atmospheric mash tower MVR;

[0007] The pressurized refinement tower system includes: a pressurized refinement tower, a pressurized refinement tower reboiler, a pressurized refinement 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 fluidically connected in sequence; the negative pressure mash tower MVR is respectively connected to the atmospheric pressure mash tower reboiling device and the pressurized fine tower reboiling device; the flash buffer device is respectively connected to the pressurized fine tower reboiling device, the negative pressure mash tower reboiling device, and the atmospheric pressure mash tower; the mash preheating device is used to increase the temperature of the fermented mature mash by gradient; the negative pressure mash tower reboiling device is used to heat the negative pressure mash tower;

[0009] The atmospheric mash tower reboiling device is used to heat the atmospheric mash tower, and the atmospheric mash tower is connected to the pressurized finishing tower through the atmospheric mash tower MVR;

[0010] The pressurized finishing tower, pressurized finishing tower MVR, and adsorption equipment are fluidically connected in sequence, and the adsorption equipment and the pressurized finishing tower are respectively connected to the negative pressure mash tower reboiling equipment, and the pressurized finishing tower reboiling equipment is used to heat the pressurized finishing tower.

[0011] In one embodiment, the mash preheating equipment includes: a mash primary preheater, a mash secondary preheater, and a mash tertiary preheater which are fluidly connected in sequence; the negative pressure mash tower reboiler equipment includes: a negative pressure mash tower group 1 reboiler, a negative pressure mash tower group 2 reboiler, and a negative pressure mash tower group 3 reboiler; the flash buffer equipment includes: a negative pressure mash tower flash tank, a negative pressure mash tower buffer tank, and a negative pressure mash tower booster pump;

[0012] The atmospheric pressure mash tower reboiler equipment comprises: an atmospheric pressure mash tower reboiler;

[0013] The pressurized refinement tower reboiler equipment includes: a first group of pressurized refinement tower reboilers and a second group of pressurized refinement tower reboilers; the adsorption equipment includes: a plurality of molecular sieve adsorption equipment.

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

[0015] The negative pressure mash tower MVR, a group of reboilers of the pressure finishing tower, and the flash tank are sequentially fluidly connected, the flash tank is respectively connected with the buffer tank and the three groups of reboilers of the negative pressure mash tower, the three groups of reboilers of the negative pressure mash tower are connected with the buffer tank, the buffer tank, the pressure 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 finishing tower are connected to the three-stage mash preheater.

[0017] The present invention also provides a method for preparing fuel alcohol by combining MVR with three-tower differential pressure distillation, and the method adopts the fuel alcohol preparation system, comprising the following steps:

[0018] Negative pressure distillation: After the fermented mature mash is subjected to gradient temperature increase by the mash preheating equipment, it enters the negative pressure mash tower for negative pressure distillation to obtain negative pressure wine gas and negative pressure waste; the negative pressure wine gas enters the negative pressure mash tower MVR for compression to obtain negative pressure compressed wine gas, and the negative pressure waste is discharged from the negative pressure mash tower, undergoes heat exchange with the mash preheating equipment, and is discharged into the lees treatment system;

[0019] Atmospheric distillation: Part of the negative pressure compressed wine gas enters the atmospheric pressure mash tower reboiling equipment to provide a heat source for the atmospheric pressure mash tower, and the remaining negative pressure compressed wine gas enters the pressure refinement tower reboiling equipment to provide a heat source for the pressure refinement tower, and then merges into the flash buffer equipment and is sent to the atmospheric pressure mash tower for atmospheric distillation to obtain atmospheric pressure wine gas and atmospheric pressure waste; the atmospheric pressure wine gas enters the atmospheric pressure mash tower MVR for compression to obtain atmospheric pressure compressed wine gas; the atmospheric pressure waste is discharged from the atmospheric pressure mash tower, undergoes heat exchange with the mash preheating equipment, and is discharged into the sewage treatment system;

[0020] Pressurized distillation: the compressed wine vapor at normal pressure enters the pressurized refining tower for pressurized distillation to obtain pressurized wine vapor and pressurized waste; the pressurized wine vapor enters the negative pressure mash tower reboiling equipment for heat exchange to obtain condensed wine vapor, which flows back to the pressurized refining tower, enters the adsorption equipment for dehydration after concentration, enters the pressurized refining tower MVR for compression to obtain pressurized compressed wine vapor, and performs heat exchange with the negative pressure mash tower reboiling equipment and the mash preheating equipment in sequence to obtain fuel alcohol; the pressurized waste is discharged from the pressurized refining tower, performs heat exchange with the mash preheating equipment, and is discharged into the sewage treatment system.

[0021] In one of the embodiments, in the negative pressure distillation step, the temperature of the fermented mature mash is 65-70°C after gradient temperature increase; the top pressure of the negative pressure mash tower is 28-32kPa, the top temperature is 60-65°C, the bottom pressure is 43-48kPa, and the bottom temperature is 75-80°C; the pressure of the negative pressure compressed wine gas is 280-300kPa, and the temperature is 130-140°C.

[0022] In one embodiment, in the atmospheric pressure finishing step, the merging into the flash buffer device includes: merging into a flash tank, the pressure of the negative pressure compressed wine gas is reduced to 140-160 kPa, and the temperature is reduced to 92-96 ° C, to obtain flash liquid and flash steam, the flash liquid enters the negative pressure mash tower buffer tank, the flash steam enters the negative pressure mash tower buffer tank after heat exchange with the negative pressure mash tower reboiler, and is combined with the flash liquid, and is pumped into the atmospheric pressure mash tower by the negative pressure mash tower booster pump;

[0023] The top pressure of the atmospheric pressure mash tower is 95-100 kPa, the top temperature is 80-85°C, the bottom pressure is 120-140 kPa, and the bottom temperature is 105-109°C;

[0024] The pressure of the normal pressure compressed wine gas is 155-160 kPa, and the temperature is 105-110°C.

[0025] In one embodiment, the flash steam enters the negative pressure mash tower buffer tank after heat exchange with the three sets of reboilers in the mash tower.

[0026] In one embodiment, in the pressure distillation step, the top pressure of the pressure rectification tower is 133-138 kPa, the top temperature is 83-88°C, the bottom pressure is 165-170°C, and the bottom temperature is 110-115°C;

[0027] The pressure of the pressurized compressed wine gas is 255-265kPa, and the temperature is 114-118°C.

[0028] In one embodiment, in the negative pressure distillation step, the negative pressure waste is discharged from the negative pressure mash tower, heat exchanged with the first-level mash preheater, and discharged into the lees treatment system;

[0029] In the atmospheric distillation step, the remaining negative pressure compressed wine gas enters a group of reboilers in the pressure rectification tower to provide a heat source for the pressure rectification tower; the atmospheric waste is discharged from the atmospheric mash tower, heat exchanged with the mash three-stage preheater, and discharged into the sewage treatment system;

[0030] In the pressurized distillation step, the pressurized wine gas enters the second group of reboilers of the negative pressure mash tower for heat exchange to obtain condensed wine gas, which is refluxed to the pressurized refinement tower, and after concentration, it enters the adsorption equipment for dehydration, and enters the pressurized refinement tower MVR for compression to obtain pressurized compressed wine gas, which is heat exchanged with the first group of reboilers of the negative pressure mash tower and the second-stage preheater of the mash in sequence to obtain fuel alcohol; the pressurized waste is heat exchanged with the third-stage preheater of the mash.

[0031] In one of the embodiments, the pressurized refinement tower is connected to the second set of reboilers of the pressurized refinement tower, and in the pressurized distillation step, steam passes through the second set of reboilers of the pressurized refinement tower to provide a heat source for the pressurized refinement tower.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The fuel alcohol preparation method and system of the MVR and three-tower differential pressure distillation of the present invention, the fuel alcohol preparation system has less steam consumption and circulating water consumption required for preparing unit weight of fuel alcohol, and the number of equipment required to be introduced in the whole system is less, which is more friendly to energy saving. The fuel alcohol preparation method cleverly uses the alcohol vapor formed by compression of each link MVR and the temperature gradient of each node. While preparing fuel alcohol, the heat energy contained therein is also used to provide a heat source for the negative pressure mash tower, the normal pressure mash tower, and the pressurized fine tower. And through the optimized design of the fuel alcohol preparation system, the high-temperature and high-pressure steam provided by the MVR in each link is accurately matched with the reboiler requirements of each tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1It is a structural schematic diagram of a fuel alcohol preparation system of the present invention using MVR and three-tower differential pressure distillation, wherein 1 is a negative pressure mash tower, 2 is an atmospheric pressure mash tower, 3 is a pressure finishing tower, 4 is a first-stage mash preheater, 5 is a second-stage mash preheater, 6 is a third-stage mash preheater, 7 is a group of reboilers in the negative pressure mash tower, 8 is a second group of reboilers in the negative pressure mash tower, 9 is a third group of reboilers in the negative pressure mash tower, 10 is a negative pressure mash tower pressure pump, 11 is an atmospheric pressure mash tower reboiler, 12 is a pressure finishing tower, 13 is a pressure finishing tower, 14 is a pressure finishing tower, 15 is a pressure finishing tower, 16 is a pressure finishing tower, 17 is a pressure finishing tower, 18 is a pressure finishing tower, 19 is a pressure finishing tower, 20 is a pressure finishing tower, 21 is a pressure finishing tower, 22 is a pressure finishing tower, 23 is a pressure finishing tower, 24 is a pressure finishing tower, 25 is a pressure finishing tower, 26 is a pressure finishing tower, 27 is a pressure finishing tower, 28 is a pressure finishing tower, 29 is a pressure finishing tower, 30 is a pressure finishing tower, 31 is a pressure finishing tower, 32 is a pressure finishing tower, 33 is a pressure finishing tower, 34 is a pressure finishing tower, 35 is a pressure finishing tower, 36 is a pressure finishing tower, 37 is a pressure finishing tower, 38 is a pressure finishing tower, 39 is a pressure finishing tower, 40 is a pressure finishing tower, 41 is a pressure finishing tower, 42 is a pressure finishing tower, 43 is a pressure finishing tower, 44 is a pressure finishing tower, 45 is a pressure finishing tower, 46 is a pressure finishing tower, 47 is a pressure finishing tower, 48 is a The first group of reboilers for the refinement tower, 13 is the second group of reboilers for the pressure refinement tower, 14 is the flash tank for the negative pressure mash tower, 15 is the buffer tank for the negative pressure mash tower, 16 is the negative pressure mash tower MVR, 17 is the atmospheric pressure mash tower MVR, 18 is the fusel alcohol separator, 19 is the pressure refinement tower MVR, 20 is the molecular sieve adsorption equipment, 21 is the fermentation mash, 22 is the lees treatment system, 23 is the finished alcohol storage tank, 24 is the sewage treatment system, 25 is the condensate return, and 26 is the steam. DETAILED DESCRIPTION

[0035] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0036] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0038] source:

[0039] Unless otherwise specified, the materials and parts used in this embodiment are all commercially available; the experimental methods are all conventional experimental methods in the art unless otherwise specified.

[0040] Example 1

[0041] A fuel alcohol preparation system combining MVR and three-tower differential pressure distillation.

[0042] The fuel alcohol preparation system is as follows Figure 1 As shown, it includes a negative pressure mash tower system, a normal pressure mash tower system, and a pressurized finishing tower system.

[0043] 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. In this embodiment, the above-mentioned mash preheating device includes: a mash first-stage preheater, a mash second-stage preheater, and a mash third-stage preheater that are fluidly connected in sequence, the above-mentioned negative pressure mash tower reboiler includes: a negative pressure mash tower group 1 reboiler, a negative pressure mash tower group 2 reboiler, and a negative pressure mash tower group 3 reboiler, and the above-mentioned flash buffer device includes: a negative pressure mash tower flash tank, a negative pressure mash tower buffer tank, and a negative pressure mash tower booster pump.

[0044] 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.

[0045] The pressurized fine tower system includes: a pressurized fine tower, a pressurized fine tower reboiler, a pressurized fine tower MVR, and an adsorption device. In this embodiment, the pressurized fine tower reboiler includes: a first group of pressurized fine tower reboilers and a second group of pressurized fine tower reboilers; the adsorption device includes: two groups of parallel molecular sieve adsorption devices.

[0046] The mash preheating equipment, negative pressure mash tower, and negative pressure mash tower MVR are fluidly connected in sequence. The bottom of the negative pressure mash tower is connected to the first-level mash preheater, and the negative pressure mash tower MVR is respectively connected to the reboiler of the atmospheric pressure mash tower and a group of reboilers of the pressurized finishing tower. The negative pressure mash tower flash tank, negative pressure mash tower buffer tank, negative pressure mash tower booster pump, and atmospheric pressure mash tower are fluidly connected in sequence. At the same time, the flash tank is respectively connected to a group of reboilers of the pressurized finishing tower and three groups of reboilers of the negative pressure mash tower, and the buffer tank is connected to the three groups of reboilers of the negative pressure mash tower.

[0047] The atmospheric mash tower is connected with the pressurized finishing tower through the atmospheric mash tower MVR, and the bottom of the atmospheric mash tower is connected with the three-stage mash preheater.

[0048] The pressurized finishing tower, the pressurized finishing tower MVR, and the adsorption equipment are fluidly connected in sequence. The adsorption equipment is connected to the first group of reboilers of the negative pressure mash tower, and the pressurized finishing tower is connected to the second group of reboilers of the negative pressure mash tower. The second group of reboilers of the pressurized finishing tower and the first group of reboilers of the pressurized finishing tower are used to heat the above-mentioned pressurized finishing tower. Steam enters the second group of reboilers of the pressurized finishing tower to provide a heat source for the pressurized finishing tower, and then forms condensed water reflux. The bottom of the pressurized finishing tower is connected to the three-stage preheater of the mash.

[0049] Example 2

[0050] A method for preparing fuel alcohol by combining MVR with three-tower differential pressure distillation.

[0051] 1. Negative pressure distillation.

[0052] The fermented mature mash (material temperature is 32°C) passes through 4-mash first-stage preheater (material temperature rises to 61°C), 5-mash second-stage preheater (material temperature rises to 64°C) and 6-mash third-stage preheater (material temperature rises to 68.6°C), and then enters 1-negative pressure mash tower (tower top pressure: 30kPa, temperature 63.4°C; tower bottom pressure: 45kPa, temperature 78.7°C) for negative pressure distillation to separate the fermented mash. In the negative pressure mash tower, the tower The bottom material is heated by the first group of reboilers of the 7-negative pressure mash tower (the heat source is the latent heat of the outlet material (116℃) of the 20-molecular sieve adsorption equipment), the second group of reboilers of the 8-negative pressure mash tower (the heat source is the latent heat of the part of the wine gas (85℃) refluxed from the top of the 3-pressurized fine tower) and the third group of reboilers of the 9-negative pressure mash tower (the heat source is the latent heat of the part of the outlet material (94.9℃) of the 16-negative pressure mash tower MVR). The wine gas rises and separates from the mash to obtain negative pressure wine gas 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 lees treatment system for treatment. The rising negative pressure wine gas enters the 16-negative pressure mash tower MVR for compression to obtain negative pressure compressed wine gas. The negative pressure wine gas generated by the 1-negative pressure mash tower enters the 16-negative pressure mash tower MVR for compression, so that the material pressure of the negative pressure compressed wine gas increases from 30 kPa to 290 kPa, and the temperature increases from 63.4 ° C to 135.4 ° C.

[0053] 2. Atmospheric pressure distillation.

[0054] The negative pressure compressed wine gas after MVR compression enters the 11-normal pressure mash tower reboiler and the 12-pressurized fine tower. A group of reboilers heat the bottom materials of the 2-normal pressure mash tower and the 3-pressurized fine tower respectively, and then enters the flash tank to reduce the material pressure to 150kPa and the temperature to 94.9℃ to obtain flash liquid and flash steam. The flash liquid enters the 15-negative pressure mash tower buffer tank, and the flash steam enters the 9-negative pressure mash tower three groups of reboilers for heat exchange and then enters the 15-negative pressure mash tower buffer tank. The materials in the 15-negative pressure mash tower buffer tank are pumped into the 2-normal pressure mash tower for separation.

[0055] 2-normal pressure mash tower (tower top pressure: 100kPa, temperature 82.5℃; tower bottom pressure: 130kPa, temperature 107.2℃) The bottom material is heated by part of the crude wine gas compressed by 16-negative pressure mash tower MVR, and the wine gas rises to obtain higher concentration of normal pressure wine gas and normal pressure waste;

[0056] The atmospheric pressure wine gas at the top of the 2-atmospheric pressure mash tower is compressed by the 17-atmospheric pressure mash tower MVR to obtain atmospheric pressure compressed wine gas, so that the material pressure of the atmospheric pressure compressed wine gas rises from 100kPa to 160kPa, and the temperature rises from 82.5℃ to 108.3℃, and enters the 3-pressure refinement tower. The atmospheric pressure waste at the bottom of the tower and the pressurized waste at the bottom of the 3-pressure refinement tower enter the 6-mash three-stage preheater together, and after heat exchange with the fermented mash, enter the sewage treatment system for treatment.

[0057] 3. Pressure distillation.

[0058] 3-pressure finishing tower (tower top pressure: 135kPa, temperature 85.5℃; tower bottom pressure: 165kPa, temperature 110.5℃) The bottom material relies on the latent heat of part of the crude wine gas and the latent heat of steam after compression by 16-negative pressure mash tower MVR. The top wine gas part enters the second group of reboilers of 8-negative pressure mash tower for condensation and then refluxes. The alcohol is gradually concentrated in the 3-pressure finishing tower. When the alcohol reaches a concentration of 95% (v / v), it enters the 19-pressure finishing tower MVR for compression (from the alcohol vapor with an absolute pressure of 135kPa and a temperature of 85.5℃ to the alcohol vapor with a temperature of 260kPa and a temperature of 116℃) to obtain pressurized compressed wine gas, and then enters the 20-molecular sieve adsorption equipment for adsorption and dehydration. The pressurized waste at the bottom of the tower and the normal pressure waste at the bottom of the 2-normal pressure mash tower enter the 6-mash three-stage preheater together with the fermented mash to be heat-exchanged and then enter the sewage treatment system for treatment;

[0059] The above-mentioned pressurized and compressed wine vapor enters the 20-molecular sieve adsorption equipment for adsorption and dehydration, and then passes through a set of reboilers in a 7-negative pressure mash tower and a 5-mash primary preheater for heat exchange before entering the finished alcohol storage for sale.

[0060] Experimental example

[0061] Similarly, in response to the various shortcomings of the traditional three-tower three-effect distillation process equipment and process methods, for example: the temperature at the bottom of the combined tower is too high, resulting in denaturation of the grains protein and coking of the materials causing equipment blockage; the pressure at the top of the combined tower is relatively low, resulting in poor dehydration effect of the alcohol vapor at the top of the tower entering the molecular sieve, which in turn leads to a higher water content in the fuel alcohol. Some researchers have proposed a double-crude and double-fine four-tower four-effect energy-saving distillation equipment and process method for producing fuel alcohol (see CN108558602A for details).

[0062] This case starts from a different perspective. Based on the combined technology of MVR and three-tower differential pressure distillation, it cleverly utilizes the alcohol vapor formed by MVR compression in each link and the temperature gradient of each node. While preparing fuel alcohol, it also uses the heat energy contained in it to provide heat sources for the negative pressure mash tower, atmospheric pressure mash tower, and pressurized fine tower. And through the optimized design of the fuel alcohol preparation system, the high-temperature and high-pressure steam provided by the MVR in each link is accurately matched with the reboiler requirements of each tower, realizing the efficient transfer and utilization of heat energy, and overcoming the technical difficulties in heat balance and distribution, and pressure and temperature matching.

[0063] The technical effects of this case are compared with the disclosed double-crude double-fine four-tower four-effect energy-saving distillation device, as shown below:

[0064] Table 1 Comparison of technical effects

[0065]

[0066] It can be seen that compared with the disclosed double-crude double-fine four-tower four-effect energy-saving distillation device and process method, this case can also solve the problems of the traditional three-tower three-effect distillation process device and process method. The bottom temperature of the atmospheric pressure crude distillation tower in this case is 107.2℃, which is lower than 120℃ in the traditional three-tower three-effect distillation process; the alcohol vapor pressure of the molecular sieve adsorber is relatively high, which reduces the water content of the fuel alcohol. In addition, the steam consumption per ton of product in this case is reduced (reduced to 0.35t / t, which is significantly reduced compared with the traditional process), and the circulating water volume per ton of product is reduced (reduced to 60t / t, saving water resources). Although the electricity consumption per ton of product increases, this part of the increased electricity consumption cost can be completely covered by the saved steam and condensed water costs, and there is a surplus. Compared with the four-tower four-effect distillation process, MVR and three-tower differential pressure distillation perform better in steam and circulating water consumption.

[0067] In addition, the combination of MVR technology and the three-tower differential pressure distillation system forms a more simplified production process. By reducing the number of towers and lowering the pressure and temperature of each tower, it is more energy-friendly and reduces investment costs and operating risks.

[0068] Specifically, this case reduces the number of towers (the number of towers is 3), and the operating conditions of each tower in this case are lower than the tower top pressure, tower top temperature, and tower bottom temperature of each tower in the existing three-tower differential pressure distillation technology. For example, in Example 1, the tower top pressure of the negative pressure mash tower is 30 kPa absolute pressure, the tower top temperature is 63.4 ° C, and the tower bottom temperature is 78.7 ° C; the tower top pressure of the atmospheric pressure mash tower is 100 kPa absolute pressure, the tower top temperature is 82.5 ° C, and the tower bottom temperature is 107.2 ° C; the tower top pressure of the pressurized fine tower is 135 kPa absolute pressure, the tower top temperature is 85.5 ° C, and the tower bottom temperature is 110.5 ° C.

[0069] At the same time, the present invention adopts multiple heat sources such as MVR steam, wine vapor at the top of the pressurized refinement tower and finished fuel alcohol vapor to heat the negative pressure mash tower, normal pressure mash tower and pressurized refinement tower. The crude wine vapor compressed by the MVR of the negative pressure mash tower gives priority to the heat source requirements of the negative pressure mash tower and the normal pressure mash tower. The insufficient heat source of the pressurized refinement tower is regulated by steam, realizing multi-heat source heating and thermal coupling system; and the wine lees and waste liquid at the bottom of the negative pressure mash tower, normal pressure mash tower and pressurized refinement tower are used to preheat the fermented mash, which significantly improves the energy utilization efficiency. The flash tank of the negative pressure mash tower flashes the steam after the MVR is compressed and heat exchanged, and recovers part of the heat energy for the negative pressure mash tower reboiler, further optimizing the utilization of heat energy. The alcohol vapor in the pressurized refinement tower is compressed by MVR to increase the temperature and pressure, replacing fresh steam to meet the needs of molecular sieve adsorption equipment. Under the premise that the global energy system is transforming from fossil fuels to renewable energy and the energy use model of the processing industry will usher in major changes, it is of positive significance to use electricity instead of steam in this section.

[0070] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0071] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A fuel alcohol preparation system combining MVR and three-tower differential pressure distillation, characterized in that: Including negative pressure mash tower system, normal pressure mash tower system, pressurized finishing tower system; 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 mash tower system comprises: an atmospheric mash tower, an atmospheric mash tower reboiler, and an atmospheric mash tower MVR; The pressurized refinement tower system includes: a pressurized refinement tower, a pressurized refinement tower reboiler, a pressurized refinement tower MVR, and an adsorption device.

2. The fuel alcohol preparation system according to claim 1, characterized in that: The mash preheating equipment, the negative pressure mash tower, and the negative pressure mash tower MVR are fluidly connected in sequence; the negative pressure mash tower MVR is respectively connected with the atmospheric pressure mash tower reboiling equipment and the pressurized refinement tower reboiling equipment; the flash buffer equipment is respectively connected with the pressurized refinement tower reboiling equipment, the negative pressure mash tower reboiling equipment, and the atmospheric pressure mash tower; the mash preheating equipment is used to increase the temperature of the fermented mature mash by gradient; the negative pressure mash tower reboiling equipment is used to heat the negative pressure mash tower; The atmospheric mash tower reboiling device is used to heat the atmospheric mash tower, and the atmospheric mash tower is connected to the pressurized finishing tower through the atmospheric mash tower MVR; The pressurized finishing tower, pressurized finishing tower MVR, and adsorption equipment are fluidically connected in sequence, and the adsorption equipment and the pressurized finishing tower are respectively connected to the negative pressure mash tower reboiling equipment, and the pressurized finishing tower reboiling equipment is used to heat the pressurized finishing tower.

3. The fuel alcohol preparation system according to claim 2, characterized in that: The mash preheating equipment includes: a mash primary preheater, a mash secondary preheater, and a mash tertiary preheater which are fluidly connected in sequence; the negative pressure mash tower reboiler equipment includes: a negative pressure mash tower group 1 reboiler, a negative pressure mash tower group 2 reboiler, and a negative pressure mash tower group 3 reboiler; the flash buffer equipment includes: a negative pressure mash tower flash tank, a negative pressure mash tower buffer tank, and a negative pressure mash tower pressure pump; The atmospheric pressure mash tower reboiler equipment comprises: an atmospheric pressure mash tower reboiler; The pressurized refinement tower reboiler equipment includes: a first group of pressurized refinement tower reboilers and a second group of pressurized refinement tower reboilers; the adsorption equipment includes: a plurality of molecular sieve adsorption equipment.

4. The fuel alcohol preparation system according to claim 3, characterized in that: The three-stage mash preheater is connected to the negative pressure mash tower, and the bottom of the negative pressure mash tower is connected to the first-stage mash preheater; The negative pressure mash tower MVR, a group of reboilers of the pressure finishing tower, and the flash tank are sequentially fluidly connected, the flash tank is respectively connected with the buffer tank and the three groups of reboilers of the negative pressure mash tower, the three groups of reboilers of the negative pressure mash tower are connected with the buffer tank, the buffer tank, the pressure 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 finishing tower are connected to the three-stage mash preheater.

5. A method for preparing fuel alcohol by combining MVR with three-tower differential pressure distillation, characterized in that: Using the fuel alcohol preparation system according to any one of claims 1 to 4, The following steps are involved: Negative pressure distillation: After the fermented mature mash is subjected to gradient temperature increase by the mash preheating equipment, it enters the negative pressure mash tower for negative pressure distillation to obtain negative pressure wine gas and negative pressure waste; the negative pressure wine gas enters the negative pressure mash tower MVR for compression to obtain negative pressure compressed wine gas, and the negative pressure waste is discharged from the negative pressure mash tower, undergoes heat exchange with the mash preheating equipment, and is discharged into the lees treatment system; Atmospheric distillation: Part of the negative pressure compressed wine gas enters the atmospheric pressure mash tower reboiling equipment to provide a heat source for the atmospheric pressure mash tower, and the remaining negative pressure compressed wine gas enters the pressure refinement tower reboiling equipment to provide a heat source for the pressure refinement tower, and then merges into the flash buffer equipment and is sent to the atmospheric pressure mash tower for atmospheric distillation to obtain atmospheric pressure wine gas and atmospheric pressure waste; the atmospheric pressure wine gas enters the atmospheric pressure mash tower MVR for compression to obtain atmospheric pressure compressed wine gas; the atmospheric pressure waste is discharged from the atmospheric pressure mash tower, undergoes heat exchange with the mash preheating equipment, and is discharged into the sewage treatment system; Pressurized distillation: the compressed wine vapor at normal pressure enters the pressurized refining tower for pressurized distillation to obtain pressurized wine vapor and pressurized waste; the pressurized wine vapor enters the negative pressure mash tower reboiling equipment for heat exchange to obtain condensed wine vapor, which flows back to the pressurized refining tower, enters the adsorption equipment for dehydration after concentration, enters the pressurized refining tower MVR for compression to obtain pressurized compressed wine vapor, and performs heat exchange with the negative pressure mash tower reboiling equipment and the mash preheating equipment in sequence to obtain fuel alcohol; the pressurized waste is discharged from the pressurized refining tower, performs heat exchange with the mash preheating equipment, and is discharged into the sewage treatment system.

6. The method for preparing fuel alcohol according to claim 5, characterized in that: In the negative pressure distillation step, the temperature of the fermented mature mash is 65-70°C after gradient temperature increase; the top pressure of the negative pressure mash tower is 28-32kPa, the top temperature is 60-65°C, the bottom pressure is 43-48kPa, and the bottom temperature is 75-80°C; the pressure of the negative pressure compressed wine gas is 280-300kPa, and the temperature is 130-140°C.

7. The method for preparing fuel alcohol according to claim 5, characterized in that: In the normal pressure finishing step, the merging into the flash buffer device includes: merging into the flash tank, the pressure of the negative pressure compressed wine gas is reduced to 140-160kPa, and the temperature is reduced to 92-96°C to obtain flash liquid and flash steam, the flash liquid enters the negative pressure mash tower buffer tank, the flash steam enters the negative pressure mash tower buffer tank after heat exchange with the negative pressure mash tower reboiler, and is combined with the flash liquid, and is pumped into the normal pressure mash tower by the negative pressure mash tower booster pump; The top pressure of the atmospheric pressure mash tower is 95-100 kPa, the top temperature is 80-85°C, the bottom pressure is 120-140 kPa, and the bottom temperature is 105-109°C; The pressure of the normal pressure compressed wine gas is 155-160 kPa, and the temperature is 105-110°C.

8. The method for preparing fuel alcohol according to claim 7, characterized in that: The flash steam enters the negative pressure mash tower buffer tank after heat exchange with the three groups of reboilers in the mash tower.

9. The method for preparing fuel alcohol according to claim 5, characterized in that: In the pressure distillation step, the top pressure of the pressure rectification tower is 133-138 kPa, the top temperature is 83-88°C, the bottom pressure is 165-170°C, and the bottom temperature is 110-115°C; The pressure of the pressurized compressed wine gas is 255-265kPa, and the temperature is 114-118°C.

10. The method for preparing fuel alcohol according to claim 5, characterized in that: In the negative pressure distillation step, the negative pressure waste is discharged from the negative pressure mash tower, undergoes heat exchange with the first-level mash preheater, and is discharged into the lees treatment system; In the atmospheric distillation step, the remaining negative pressure compressed wine gas enters a group of reboilers in the pressure rectification tower to provide a heat source for the pressure rectification tower; the atmospheric waste is discharged from the atmospheric mash tower, heat exchanged with the mash three-stage preheater, and discharged into the sewage treatment system; In the pressurized distillation step, the pressurized wine gas enters the second group of reboilers of the negative pressure mash tower for heat exchange to obtain condensed wine gas, which is refluxed to the pressurized refinement tower, and after concentration, it enters the adsorption equipment for dehydration, and enters the pressurized refinement tower MVR for compression to obtain pressurized compressed wine gas, which is heat exchanged with the first group of reboilers of the negative pressure mash tower and the second-stage preheater of the mash in sequence to obtain fuel alcohol; the pressurized waste is heat exchanged with the third-stage preheater of the mash.

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