distilling

Distillation is a widely-used separation technique which uses heat to vaporise liquid mixtures before condensing them back down, isolating their individual components by applying heat. Volatile components are separated from non-volatile ones through this process; typically the volatile fraction is known as heads and the rest hearts and tails (head being highest volume component and tail as lowest). Distillate runs can contain one or both heads or hearts or tails containing low boiling point compounds with undesirable impurities which must be eliminated prior to creating their final spirit product.

Distillation operates under the assumption that all components in a liquid at a given temperature have their own individual boiling point, and can therefore be separated based on these. Unfortunately, however, liquid mixtures often comprise different azeotropes with differing boiling points which form bands overlapping one another; to create ultra-pure products more chemical separation processes must be used in addition to distillation to remove impurities from distillate.

There are various techniques for breaking an azeotrope and producing pure distillates, including increasing or decreasing pressure, adding or subtracting components from its composition, or physically separating it.

Hybrid processes that use solvent extraction and absorption require considerable amounts of energy to reach high temperatures necessary for volatiles to vaporise from compounds, as well as maintaining suitable pressure in these processes. Achieveing this may present additional challenges for plants.

Distillation of alcohol is relatively straightforward. The key is that more volatile alcohol has a lower boiling point than water, meaning it evaporates faster and separates from other components in solution faster than usual – leading to collection and condensation into liquid form with much higher concentrations of alcohol than previously present in original mix. This process forms the basis of all forms of distillation including beer brewing and whiskey distilling.

Raoult’s law and Dalton’s law both dictate that in an ideal system at constant pressure, Raoult’s and Dalton’s laws dictate that the ratio of liquid-to-vapor composition will remain unchanged – an equilibrium state. Unfortunately, distillation does not work this way in practice: lighter volatile components (like fruity esters) always vaporize before heavier ones, so mixture will never become completely clean.

Distillation alone cannot guarantee ultra-pure products, so additional chemical separation methods must also be utilized. Batch distillation and fractionation are two proven ways of reaching this goal.

Distillation takes place in a still, or pot. Fermented mash is transferred into the still and heated to low temperatures until alcohol begins evaporating from its molecules, then collected and condensed back into liquid form with much higher alcohol concentration than was present initially in its mixture.

Step Two entails repeating this sequence to achieve increasingly pure product. In order to do this, a distiller must constantly monitor the ratio of vapor-to-liquid flow in the column, the reflux-to-product flow rate to control discharge temperature and alcohol vapor concentration, and how much heat is being applied to reboiler.