What kinds of stills are there and what are the differences?
Not all stills are made to produce alcohol, some are used to remove essential oils and fragrances from plants, some to separate components of naturally blended substances (such as gas and oil); the stills we are concerned with are for removing and collecting alcohol from a beer obtained from fermenting a mash of grain or other bio-source.
The pot still: The oldest and best known of the kinds of stills; it consists of a boiling pot and a lid with some form of condenser attached to cool down the vaporized alcohol.
A reflux still: A tall column which houses some form of barriers which slow down the vapors and allow them to concentrate by temperature. The barriers can be bubble plates, marbles, rasching rings, copper or stainless steel scrubbers, bits of broken glass ect.
A fractioning still: A form of reflux still that allows you to remove vapors or condensed alcohol at different stages of separation.
Reflux and Fraction stills are further classified by what method they use to control refluxing.
Liquid management: or LM is where a portion of the condensed alcohol is re-introduced into the column to clean and concentrate the rising vapors.
Vapor management: or VM is where the vapors rising in the column are cooled at a controlled rate causing water to prematurely condense and drop out of the alcohol / water blend. This reduces the height of the column.
Batch vs. Continuous: Batch stills are stills which are charged with a set amount of beer which is to be distilled. Continuous stills are designed to be fed a flow of beer which is distilled and replenished constantly.
Vacuum stills: Any still which is run under a negative pressure, this allows for lower boiling temperatures and used when either conserving energy or when heat can destroy the materials being processed.