Introduction to producing liquor
BREWHA fermenters (3-in-1 and 4-in-1) can be used for distillation and producing spirits such as whiskey— scotch (from barley), bourbon (barley and corn) and rye (from rye)—rum (cane sugar), brandy (fruit) and vodka (any sugar source). Once the sugars have been fermented, the element in the fermenter heats the fermented liquid (called 'wash') and the vapor (mixture of water, alcohol and trace amounts of other compounds) passes up out of the fermenter and into the Condensing Assembly where it cools, condenses and can be collected.
The first portion of the distillate, called foreshots contains undesirable (and sometimes poisonous) compounds which are discarded. The second portion called the heads is set aside for redistilling. The third portion, called hearts, is what is collected for consumption, and the final portion, called tails, is also set aside for redistilling.
A few methods are employed to ensure best tasting liquor. The first, is to use good brewing technique. If the fermented wash is not palatable, likely your distillate won't be either. Employing good brewing technique (good sanitation throughout, fresh ingredients, complete mash at low end of temperature range to ensure maximum amount of fermentable sugar, vigorous boiling, and strong fermenting) helps ensure the wash will be a good feedstock for distillation. The second is to remove the yeast from the bottom of the fermenter and the element before distillation (use a highly flocculant yeast and consider removing the clear beer/wash out of the fermenter, and rinsing the yeast out of the fermenter before returning the beer/wash and distilling)—this helps reduce off notes. The third is to use some copper in the distillation apparatus as copper reacts with and traps undesirable compounds keeping them out of your liquor. As is show in the picture at the top, a Yeast Harvester(s) stuffed with 100% copper scrub brushes is ideal as the scrub brushes have very high surface area for the greatest interaction with the vapor. The fourth is to use distillers carbon to clean up the distillate. The Yeast Harvester and items from the Condensing Assembly can be repurposed for scrubbing alcohol and assembled as is shown in the picture. The fifth is to be patient. Don't rush fermentation (let the yeast finish; a better tasting beer/wash makes a better tasting liquor), and don't rush distillation—allow time for the copper scrub brushes to cause reflux providing higher purity of your distillate.
As for the purification process with carbon, one Yeast Harvester full of rinsed carbon (see this document for more information on carbon) can process up to about 2L/hr of fairly clean spirit (if the raw liquor was very harsh it should be slower). This will produce a relatively neutral spirit (e.g. the peat smoke flavor from peated malt in scotch and molasses flavor in rum is mostly removed) so some of the raw spirit (from the heads) may be retained and mixed back to provide a balance of clean spirit and flavor.