Alcohol distillation is an integral component of turning grains into fuel alcohol for use in cars and other engines, and must be performed correctly and safely for maximum effectiveness.
After cooking the mash and adding yeast for fermentation, sugars are broken down into alcohol and carbon dioxide by bacteria in a process known as fermentation. Once complete, an 8-10% concentration of ethanol exists in what’s called the wash liquid, requiring boiling point differences to separate out.
Distillation is the process of heating and cooling liquid mixtures in a column, forcing vapors through it, and collecting condensed liquid fractions as condensable emulsions. These fractions include heads that contain unwanted contaminants like methanol or unwanted impurities as well as hearts with higher alcohol concentration that will ultimately be sold as alcoholic beverages.
Vapor-Liquid Equilibrium
When distilling at normal atmospheric pressure, the vapor-to-liquid ratio at each stage depends on temperature and column length. To reach an optimum vapor-to-liquid ratio, top temperature must be significantly lower than bottom to enable controlled sequence of evaporation and condensation.
However, as desired vapor-to-liquid ratio decreases, energy requirements to operate the distillation column increase (see Table 2). This is because at higher concentrations the azeotrope point occurs earlier and thus the reflux to product flow rate needs to be higher for efficient performance of distillation column operation.
