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The working principle of distillation tower:
In fermented mature mash, not only does it contain alcohol, but also dozens of other substances. If water is added, the content of these substances far exceeds that of alcohol. The alcohol content in mature mash is only about 7-11% (by volume), while impurities including water, alcohols, aldehydes, acids, and lipids account for almost 90%. To obtain pure alcohol, a certain method must be used to separate the alcohol from the mature mash. In production, the method of heating distillation is used to separate various substances with different boiling points, densities, and volatiles from different equipment, thereby obtaining higher purity alcohol.
The working principle of the crude distillation tower is that the fermented mature mash is preheated and enters the upper part of the crude distillation tower. Heating steam is continuously and uniformly introduced into the bottom of the tower. At this time, the liquid alcohol in the mature mash can be converted into alcohol gas due to the heating effect. At the same time, other low boiling and volatile impurities become gaseous and enter the formaldehyde removal tower together with the alcohol (or directly enter the distillation tower). The bottom of the tower discharges the distilled waste mash outside the tower.
When the crude distillation tower is running normally, the top temperature of the tower should not be lower than 93 ℃, but it should not be too high. Excessive top temperature is not conducive to separation and consumes a large amount of steam. Generally controlled at 95-96 ℃. The temperature is too low, and the awakened alcohol has not completely evaporated, resulting in a significant increase in alcohol escape rate. The boiling point of pure alcohol is 78.3 ℃, but the boiling point of mixed liquids containing water and other components is much higher than 78.3 ℃. Therefore, the bottom temperature of the crude distillation tower should not be lower than 105 ℃, generally between 105 ℃ and 109 ℃. Before entering the crude distillation tower, mature mash must be preheated to reduce temperature differences, which is beneficial for the stable operation of the crude distillation tower. Generally, the preheating temperature of the mash should be controlled between 60-70 ℃, but some production units may lower it by 5-10 ℃ due to the influence of equipment performance.
The working principle of the formaldehyde removal tower is that the alcohol in the mature mash is roughly distilled and enters the tower from the top of the crude distillation tower in a gaseous state. Through appropriate heating, condensation, and reflux in the formaldehyde removal tower, low boiling point and volatile impurities such as aldehydes and esters contained in the crude alcohol are discharged from the formaldehyde discharge pipe. The formaldehyde removed alcohol enters the liquid-phase distillation tower from the bottom of the aldehyde tower, and some of the liquor heads enter the fermentation tank or mature mash from the liquor head pipe.
Under normal circumstances, the bottom temperature of the formaldehyde removal tower is 86-89 ℃, and the top temperature is controlled at 79 ℃. The water temperature of the 1 * condenser on the formaldehyde removal tower should not be lower than 60 ℃, and the temperature of the last condenser should not be lower than 25 ℃.
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