Three-tower distillation system for anhydrous ethanol production

Abstract

The invention provides a three-tower distillation system for producing anhydrous ethanol, which is used for distilling fermented mature mash. The system comprises a mash tower, a combination tower and a distillation tower. The mash tower degases the fermented mature mash entering the tower to obtain degassed mash, and removes formaldehyde from the degassed mash to obtain crude alcohol. The combination tower performs positive-pressure crude distillation on the degassed mash entering the tower to obtain alcohol vapor with an alcohol content of more than 95%. The distillation tower extracts and rectifies the crude alcohol entering the tower, and dehydrates it through a molecular sieve to obtain anhydrous ethanol with an alcohol content of more than 99.5%. A double-crude-tower three-effect thermal coupling distillation technology is adopted, and steam in a steam main pipe is heated by a reboiler through heat exchange. At the same time, through the cooperation of the reboiler and the heat exchanger, the alcohol vapor at the top of the distillation tower supplies heat to the combination tower, and the wine vapor at the top of the combination tower supplies heat to the mash tower, so that energy is fully reused, which greatly reduces the energy consumption in the ethanol distillation process.

Description

Technical Field

[0001] The invention relates to the field of fuel ethanol production, in particular to a three-tower distillation system for anhydrous ethanol production. Background Art

[0002] As energy conservation and emission reduction become mainstream environmental slogans worldwide, ethanol gasoline is increasingly being used to replace traditional gasoline. Ethanol gasoline is a new generation of clean, environmentally friendly automotive fuel, blended by a specific volumetric ratio of denatured fuel ethanol to a specialized gasoline component oil without MTBE oxygenated additives. This blend is made by designated automotive ethanol gasoline blending centers using a specialized process in accordance with the quality requirements of the national standard GB18351-2004. Energy restructuring and efforts to reduce environmental pollution are driving the development of ethanol fuel. Current grain-to-ethanol processes produce ethanol of low purity and consume significant energy. Summary of the Invention

[0003] The technical problem to be solved by the present invention is that in the current process for preparing ethanol from grain, the purity of the ethanol produced is low and the energy consumption is high. The present invention provides a three-tower distillation system for producing anhydrous ethanol to solve the above problems.

[0004] The technical solution adopted by the present invention to solve its technical problems is: a three-tower distillation system for producing anhydrous ethanol, which is used for distilling fermented mature mash, comprising a mash tower, a combination tower and a distillation tower, wherein the mash tower, the combination tower and the distillation tower are all connected to a reboiler for providing heat required for distillation, and the fermented mature mash is gradually distilled through the mash tower, the combination tower and the distillation tower, the mash tower degases the fermented mature mash entering the tower to obtain degassed mash, and removes formaldehyde from the degassed mash to obtain crude alcohol; the combination tower performs positive pressure crude distillation on the degassed mash entering the tower to obtain alcohol vapor with an alcohol content of more than 95%; the distillation tower extracts and distills the crude alcohol entering the tower, and dehydrates it through a molecular sieve to obtain anhydrous ethanol with an alcohol content of more than 99.5%.

[0005] Furthermore: the mash tower is in a negative pressure state, and the mash tower is provided with a dealdehyde section, a degassing section and a coarse distillation section from top to bottom in sequence, the top of the degassing section is provided with a material inlet, and the bottom of the degassing section is connected to the top of the coarse distillation section through a gravity pipe; a first feed pump is provided between the degassing section and the combined tower, and the first feed pump pumps the fermented mash degassed in the degassing section into the combined tower; a first liquid outlet is provided at the bottom of the coarse distillation section; a first air outlet is provided at the top of the degassing section, and the mash tower is also provided with a first heat exchanger, a second heat exchanger and a mash tower reflux tank, the tube side of the first heat exchanger is connected to the material inlet and the tube side outlet of the second heat exchanger, the tube side inlet of the second heat exchanger is connected to the fermented mash feed pump, and the shell side of the first heat exchanger is respectively connected to the first air outlet and the inlet of the mash tower reflux tank.

[0006] Furthermore: a second air outlet is provided at the top of the crude distillation section, and a third air inlet connected to the second air outlet is provided at the bottom of the dealdehyde section; a third liquid outlet is provided in the middle of the dealdehyde section, and a third air outlet is provided at the top of the dealdehyde section, and the shell side of the second heat exchanger is respectively connected to the third air outlet and the inlet of the mash tower reflux tank.

[0007] Furthermore: the reboiler includes a mash tower reboiler, a combination tower reboiler and a distillation tower reboiler, the three-tower distillation system is also provided with a first preheater, a second preheater and a combination tower reflux tank, the combination tower is provided with a fourth air inlet and a fourth liquid inlet, the pipe side of the first preheater is respectively connected to the first feed pump and the pipe side inlet of the second preheater, the pipe side outlet of the second preheater is connected to the fourth liquid inlet, a fourth air outlet is provided at the top of the combination tower, the fourth air outlet is connected to the inlet of the mash tower reboiler, the outlet of the mash tower reboiler is connected to the combination tower reflux tank, the liquid outlet of the combination tower reflux tank is connected to the combination tower through the combination tower reflux pump, and the mash tower reboiler can heat the mash tower; the bottom of the combination tower is provided with a fourth liquid outlet.

[0008] Furthermore: the fourth liquid outlet is connected to the shell side inlet of the second preheater through the combined tower lees pump, and the shell side outlet of the second preheater is connected to the crude distillation part.

[0009] Furthermore: the three-tower distillation system also includes an auxiliary tower and a crude wine preheater, the pipe side of the crude wine preheater is respectively connected to the third liquid outlet and the liquid inlet of the auxiliary tower; the top of the auxiliary tower is provided with a fifth air outlet, and the fifth air outlet is connected to the fourth air inlet; the tower bottom of the auxiliary tower is provided with a fifth liquid outlet, and the fifth liquid outlet is connected to the distillation tower feed pump.

[0010] Furthermore: the distillation tower is provided with a sixth liquid inlet, a distillation tower preheater is provided between the sixth liquid inlet and the distillation tower feed pump, the pipe side of the distillation tower preheater is respectively connected to the sixth liquid inlet and the outlet of the distillation tower feed pump, the distillation tower is provided with a fusel oil outlet, and the top of the distillation tower is provided with a sixth gas outlet, and the sixth gas outlet is connected to the molecular sieve.

[0011] Furthermore: the sixth gas outlet is connected to the inlet of the combination tower reboiler, the outlet of the combination tower reboiler is connected to the distillation tower reflux tank, the liquid inlet of the distillation tower reflux tank is connected to the liquid outlet of the combination tower reflux tank, and the liquid outlet of the distillation tower reflux tank is connected to the distillation tower through a distillation tower reflux pump.

[0012] Furthermore: the distillation tower reboiler is connected to a steam main pipe, the steam main pipe provides steam with heat required for distillation, and the auxiliary tower is provided with an auxiliary tower reboiler.

[0013] Furthermore: a liquid level controller and an alarm are provided at the bottom of the mash tower, combination tower, auxiliary tower and distillation tower. The liquid level controller is electrically connected to the alarm, and the alarm can receive the signal from the liquid level controller and issue an alarm.

[0014] The beneficial effects of the present invention are as follows: the three-tower distillation system for producing anhydrous ethanol of the present invention prepares anhydrous ethanol with an alcohol content of more than 99.5% through the cooperation of a mash tower, a combination tower, a distillation tower and a molecular sieve; the double-crude tower three-effect thermal coupling distillation technology is adopted; the steam in the steam main pipe heats the distillation tower through heat exchange in a reboiler; at the same time, through the cooperation of the reboiler and the heat exchanger, the alcohol vapor at the top of the distillation tower heats the combination tower, and the wine vapor at the top of the combination tower heats the mash tower, so that energy is fully reused, thereby greatly reducing the energy consumption in ethanol distillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below with reference to the accompanying drawings and examples.

[0016] Figure 1 is a process flow diagram of a three-tower distillation system for producing anhydrous ethanol according to the present invention;

[0017] Figure 2 Yes, the structural diagram of the mash tower;

[0018] Figure 3 It is a structural diagram of the combined tower;

[0019] Figure 4 It is a structural diagram of a distillation tower.

[0020] In the figure, 1, mash tower, 2, combination tower, 3, distillation tower, 4, steam main, 5, auxiliary tower, 10, material inlet, 11, gravity pipe, 12, first feed pump, 13, first liquid outlet, 14, first gas outlet, 15, first heat exchanger, 16, second heat exchanger, 17, mash tower reflux tank, 20, second gas outlet, 21, third gas inlet, 22, third liquid outlet, 23, third gas outlet, 24, first preheater, 25, second preheater, 26, combination tower reflux tank, 30 , mash tower reboiler, 31. combination tower reboiler, 32. distillation tower reboiler, 33. auxiliary tower reboiler, 40. fourth air inlet, 41. fourth liquid inlet, 42. fourth air outlet, 43. fourth liquid outlet, 44. combination tower lees pump, 50. crude wine preheater, 51. fifth air outlet, 52. fifth liquid outlet, 60. distillation tower feed pump, 61. sixth liquid inlet, 62. distillation tower preheater, 63. fusel oil outlet, 64. sixth air outlet, 65. distillation tower reflux tank. DETAILED DESCRIPTION

[0021] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention. On the contrary, the embodiments of the present invention include all variations, modifications, and equivalents that fall within the spirit and scope of the appended claims.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0023] In addition, the terms "first", "second", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0024] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention pertain.

[0025] like Figure 1As shown, the present invention provides a three-tower distillation system for the production of anhydrous ethanol, which is used for distilling fermented mature mash, comprising a mash tower 1, a combination tower 2 and a distillation tower 3, wherein the mash tower 1, the combination tower 2 and the distillation tower 3 are all connected with a reboiler for providing heat required for distillation, and the fermented mature mash is gradually distilled through the mash tower 1, the combination tower 2 and the distillation tower 3, the mash tower 1 degases the fermented mash entering the tower to obtain degassed mash, and removes formaldehyde from the degassed mash to obtain crude alcohol; the combination tower 2 performs positive pressure crude distillation on the degassed mash entering the tower to obtain alcohol vapor with an alcohol content of more than 95%; the distillation tower 3 extracts and distills the crude alcohol entering the tower, and dehydrates it through a molecular sieve to obtain anhydrous ethanol with an alcohol content of more than 99.5%.

[0026] Combine Figure 2 、 Figure 3 and Figure 4 As shown, the mash tower 1 is in a negative pressure state, and the mash tower 1 is provided with a dealdehyde section, a degassing section and a crude distillation section from top to bottom. The top of the degassing section is provided with a material inlet 10, and the bottom of the degassing section is connected to the top of the crude distillation section through a gravity pipe 11; a first feed pump 12 is provided between the degassing section and the combined tower 2, and the first feed pump 12 pumps the fermented mash degassed in the degassing section into the combined tower 2; the bottom of the crude distillation section is provided with a first feed pump 12; A liquid outlet 13; a first gas outlet 14 is provided on the top of the degassing section, and a first heat exchanger 15, a second heat exchanger 16 and a mash tower reflux tank 17 are also provided on the mash tower 1. The tube side of the first heat exchanger 15 is connected to the material inlet 10 and the tube side outlet of the second heat exchanger 16, the tube side inlet of the second heat exchanger 16 is connected to the fermentation mash feed pump, and the shell side of the first heat exchanger 15 is respectively connected to the first gas outlet 14 and the inlet of the mash tower reflux tank 17.

[0027] The fermentation mash feed pump pumps the fermentation mash into the mash tower 1, and the fermentation mash flows through the second heat exchanger 16 and the first heat exchanger 15 and enters the degassing part of the mash tower 1 from the material inlet 10. After entering the tower, the carbon dioxide, volatile acids and low-boiling impurities in the fermentation mash are separated from the fermentation mash under the action of negative pressure to form steam. The steam rises in the degassing part and is discharged from the first gas outlet 14, and flows through the first heat exchanger 15 to heat the fermentation mash and then condenses into condensate and flows into the mash tower reflux tank 17; the fermentation mash without gas is degassed mash, and part of the degassed mash is pumped into the combined tower 2 through the first feed pump 12, and the rest of the degassed mash flows into the coarse distillation part through the gravity pipe 11 and descends, and is heated by the steam rising from the bottom of the tower. The wine vapor rises and separates from the waste mash to form wine vapor containing alcohol and waste mash without alcohol content, and the waste mash is discharged from the first liquid outlet 13.

[0028] A second gas outlet 20 is provided at the top of the crude distillation section, and a third gas inlet 21 connected to the second gas outlet 20 is provided at the bottom of the dealdehyde section; a third liquid outlet 22 is provided in the middle of the dealdehyde section, and a third gas outlet 23 is provided at the top of the dealdehyde section, and the shell side of the second heat exchanger 16 is respectively connected to the third gas outlet 23 and the inlet of the mash tower reflux tank 17.

[0029] The wine vapor ascends into the formaldehyde removal section for formaldehyde removal, and the formaldehyde-free crude alcohol is discharged from the third liquid outlet 22; the higher concentration of alcohol vapor containing volatile acids and low-boiling point impurities is discharged from the third gas outlet 23, flows through the second heat exchanger 16 to heat the fermentation mash, and then condenses into condensate and flows into the mash tower reflux tank 17.

[0030] The reboiler includes a mash tower reboiler 30, a combination tower reboiler 31 and a distillation tower reboiler 32. The three-tower distillation system is also provided with a first preheater 24, a second preheater 25 and a combination tower reflux tank 26. The combination tower 2 is provided with a fourth air inlet 40 and a fourth liquid inlet 41. The pipe side of the first preheater 24 is respectively connected to the first feed pump 12 and the pipe side inlet of the second preheater 25, and the pipe side outlet of the second preheater 25 is connected to the fourth liquid inlet 41. A fourth air outlet 42 is provided at the top of the combination tower 2. The fourth air outlet 42 is connected to the inlet of the mash tower reboiler 30. The outlet of the mash tower reboiler 30 is connected to the combination tower reflux tank 26. The liquid outlet of the combination tower reflux tank 26 is connected to the combination tower 2 through the combination tower reflux pump. The mash tower reboiler 30 can heat the mash tower 1; the bottom of the combination tower 2 is provided with a fourth liquid outlet 43.

[0031] Partially degassed mash is pumped into the combination tower 2 through the first feed pump 12, and after being preheated by the first preheater 24 and the second preheater 25, it enters the combination tower 2 from the fourth liquid inlet 41. The degassed mash descends in the combination tower 2 and is heated by the rising steam to form separated ascending wine vapor and alcohol-free waste mash, which is discharged from the fourth liquid outlet 43; the wine vapor ascends and enters the concentration section of the combination tower, and the wine vapor gradually concentrates until the alcohol concentration of the wine vapor at the top of the tower reaches more than 95%; the wine vapor enters the mash tower reboiler 30 through the fourth gas outlet 42 and is condensed into condensate, which flows into the combination tower reflux tank 26. The combination tower reflux pump pumps the condensate in the combination tower reflux tank 26 into the combination tower 2, and at the same time, the mash tower reboiler 30 heats the mash tower 1.

[0032] The fourth liquid outlet 43 is connected to the shell side inlet of the second preheater 25 through the combined tower lees pump 44. The combined tower lees pump 44 pumps the waste mash from the fourth liquid outlet 43 into the second preheater 25. The shell side outlet of the second preheater 25 is connected to the crude distillation section.

[0033] The combined tower lees pump 44 pumps the waste mash from the fourth liquid outlet 43 into the second preheater 25 , where the waste mash is preheated to deaerated mash and then discharged into the coarse distillation section of the mash tower 1 for flash evaporation, with the flash steam serving as a partial heat source for the mash tower 1 .

[0034] The three-tower distillation system also includes an auxiliary tower 5 and a crude wine preheater 50, and the pipe side of the crude wine preheater 50 is respectively connected to the third liquid outlet 22 and the liquid inlet of the auxiliary tower 5; the top of the auxiliary tower 5 is provided with a fifth gas outlet 51, and the fifth gas outlet 51 is connected to the fourth gas inlet 40; the tower bottom of the auxiliary tower 5 is provided with a fifth liquid outlet 52, and the fifth liquid outlet 52 is connected to the distillation tower feed pump 60.

[0035] The crude alcohol discharged from the dealdehyde section of the mash tower 1 is preheated by the crude alcohol preheater 50 and then enters the top of the auxiliary tower 5. Part of the alcohol vapor ascends through the fifth gas outlet 51 and enters the combined tower 2. The remaining crude alcohol enters the bottom of the auxiliary tower 5 and is pumped to the distillation tower 3 through the distillation tower feed pump 60.

[0036] The distillation tower 3 is provided with a sixth liquid inlet 61, and a distillation tower preheater 62 is provided between the sixth liquid inlet 61 and the distillation tower feed pump 60. The pipe side of the distillation tower preheater 62 is respectively connected to the sixth liquid inlet 61 and the outlet of the distillation tower feed pump 60. The distillation tower 3 is provided with a fusel oil outlet 63, and the top of the distillation tower 3 is provided with a sixth gas outlet 64, and the sixth gas outlet 64 is connected to the molecular sieve dehydration layer.

[0037] The crude alcohol is heated in the distillation tower preheater 62 and then enters the distillation tower 3. While gradually concentrating, low-boiling-point impurities such as methanol rise to the top of the tower along with the alcohol vapor. The light alcohol containing fusel oil flows out from the fusel oil outlet 63, and is cooled in the cooler and then sent to the separator to separate the fusel oil. The alcohol vapor with an alcohol content of more than 95% is extracted from the sixth gas outlet 64 and sent to the molecular sieve dehydration layer for dehydration to obtain anhydrous ethanol with an alcohol content of more than 99.5%.

[0038] The sixth gas outlet 64 is connected to the inlet of the combination tower reboiler 31, the outlet of the combination tower reboiler 31 is connected to the distillation tower reflux tank 65, the liquid inlet of the distillation tower reflux tank 65 is connected to the liquid outlet of the combination tower reflux tank 26, and the liquid outlet of the distillation tower reflux tank 65 is connected to the distillation tower 3 through the distillation tower reflux pump, and the distillation tower reflux pump pumps the alcohol liquid at the bottom of the distillation tower reflux tank 65 into the distillation tower 3.

[0039] Part of the alcohol vapor discharged from the sixth gas outlet 64 enters the combination tower reboiler 31 to heat the combination tower 2, condenses into condensate and refluxes into the distillation tower reflux tank 65. At the same time, part of the condensate in the combination tower reflux tank 26 enters the distillation tower reflux tank 65 and is pumped to the distillation tower 3 through the distillation tower reflux pump.

[0040] The distillation tower reboiler 32 is connected to a steam main 4, which provides steam for the heat required for distillation. The auxiliary tower 5 is provided with an auxiliary tower reboiler 33. The distillation tower 3 is heated by passing steam from the steam main into the distillation tower reboiler 32 for heat exchange, while the auxiliary tower 5 is heated by the auxiliary tower reboiler 33.

[0041] The mash tower 1, combination tower 2, auxiliary tower 5, and distillation tower 3 are each equipped with a liquid level controller and an alarm at the bottom. The liquid level controller is electrically connected to the alarm, and the alarm is capable of receiving signals from the liquid level controller and issuing an alarm. The liquid level controller maintains a constant liquid level at the bottom of the tower. When the liquid level at the bottom of the tower exceeds a preset level, the alarm is capable of receiving signals from the liquid level controller and issuing an alarm, facilitating the timely detection and resolution of abnormalities. Both the liquid level controller and the alarm are well-known products in the prior art.

[0042] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0043] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A three-tower distillation system for anhydrous ethanol production, used for distilling fermented mature mash, comprising a mash tower, a combination tower, and a rectification tower, characterized in that: The mash tower, the combination tower and the distillation tower are all connected with a reboiler for providing the heat required for distillation. The fermented mature mash is gradually distilled through the mash tower, the combination tower and the distillation tower. The mash tower degases the fermented mature mash entering the tower to obtain degassed mash, and removes formaldehyde from the degassed mash to obtain crude alcohol; The combined tower performs positive pressure crude distillation on the degassed mash entering the tower to obtain alcohol vapor with a wine content of more than 95%; The distillation tower extracts and distills the crude alcohol entering the tower, and dehydrates it through molecular sieves to obtain anhydrous ethanol with an alcohol content of more than 99.5%; The mash tower is in a negative pressure state, and is provided with a dealdehyde section, a degassing section, and a crude distillation section from top to bottom. The top of the degassing section is provided with a material inlet, and the bottom of the degassing section is connected to the top of the crude distillation section through a gravity pipe; a first feed pump is provided between the degassing section and the combined tower, and the first feed pump pumps the fermented mash degassed in the degassing section into the combined tower; the bottom of the crude distillation section is provided with a first liquid outlet; A first gas outlet is provided on the top of the degassing section, and a first heat exchanger, a second heat exchanger and a mash tower reflux tank are further provided on the mash tower. The tube side of the first heat exchanger is connected to the material inlet and the tube side outlet of the second heat exchanger, the tube side inlet of the second heat exchanger is connected to the fermentation mash feed pump, and the shell side of the first heat exchanger is respectively connected to the first gas outlet and the inlet of the mash tower reflux tank; A second gas outlet is provided at the top of the crude distillation section, and a third gas inlet connected to the second gas outlet is provided at the bottom of the dealdehyde removal section; a third liquid outlet is provided at the middle of the dealdehyde removal section, and a third gas outlet is provided at the top of the dealdehyde removal section, and the shell side of the second heat exchanger is respectively connected to the third gas outlet and the inlet of the mash tower reflux tank; The combined tower is provided with a fourth air inlet and a fourth liquid inlet. The three-tower distillation system also includes an auxiliary tower and a crude wine preheater. The pipe side of the crude wine preheater is respectively connected to the third liquid outlet and the liquid inlet of the auxiliary tower; the top of the auxiliary tower is provided with a fifth air outlet, and the fifth air outlet is connected to the fourth air inlet; the tower bottom of the auxiliary tower is provided with a fifth liquid outlet, and the fifth liquid outlet is connected to the distillation tower feed pump.

2. The three-tower distillation system for producing anhydrous ethanol as claimed in claim 1, wherein: The reboiler includes a mash tower reboiler, a combination tower reboiler and a distillation tower reboiler. The three-tower distillation system is also provided with a first preheater, a second preheater and a combination tower reflux tank. The pipe side of the first preheater is respectively connected to the first feed pump and the pipe side inlet of the second preheater, and the pipe side outlet of the second preheater is connected to the fourth liquid inlet. A fourth air outlet is provided at the top of the combination tower, and the fourth air outlet is connected to the inlet of the mash tower reboiler. The outlet of the mash tower reboiler is connected to the combination tower reflux tank. The liquid outlet of the combination tower reflux tank is connected to the combination tower through the combination tower reflux pump. The mash tower reboiler can heat the mash tower; and a fourth liquid outlet is provided at the bottom of the combination tower.

3. The three-tower distillation system for producing anhydrous ethanol as claimed in claim 2, wherein: The fourth liquid outlet is connected to the shell side inlet of the second preheater through the combined tower lees pump, and the shell side outlet of the second preheater is connected to the crude distillation part.

4. The three-tower distillation system for producing anhydrous ethanol as claimed in claim 1, wherein: The distillation tower is provided with a sixth liquid inlet, a distillation tower preheater is provided between the sixth liquid inlet and the distillation tower feed pump, the pipe side of the distillation tower preheater is respectively connected to the sixth liquid inlet and the outlet of the distillation tower feed pump, the distillation tower is provided with a fusel oil outlet, and the top of the distillation tower is provided with a sixth gas outlet, and the sixth gas outlet is connected to the molecular sieve.

5. The three-tower distillation system for producing anhydrous ethanol as claimed in claim 4, wherein: The sixth gas outlet is connected to the inlet of the combination tower reboiler, the outlet of the combination tower reboiler is connected to the distillation tower reflux tank, the liquid inlet of the distillation tower reflux tank is connected to the liquid outlet of the combination tower reflux tank, and the liquid outlet of the distillation tower reflux tank is connected to the distillation tower through a distillation tower reflux pump.

6. The three-tower distillation system for producing anhydrous ethanol as claimed in claim 2, wherein: The distillation tower reboiler is connected to a steam main pipe, and the steam main pipe provides steam with heat required for distillation. The auxiliary tower is provided with an auxiliary tower reboiler.

7. The three-tower distillation system for producing anhydrous ethanol as claimed in claim 1, wherein: The bottoms of the mash tower, combination tower, auxiliary tower and distillation tower are all provided with a liquid level controller and an alarm. The liquid level controller is electrically connected to the alarm, and the alarm can receive signals from the liquid level controller and issue an alarm.

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