Editing Column still (section)

==Description==
The first column (called the analyzer) in a column still has [[steam]] rising and [[Wash (distilling)|wash]] descending through several levels.<ref>{{cite book | url=https://books.google.com/books?id=0aWR3fuA7QIC&q=Coffey+still+analyzer%29+in+a+column&pg=PA276 | title=Fermented Beverage Production |edition=2nd | publisher=Kluwer Academic/Plenum Publishers |author1=Andrew G. H. Lea |author2=John Raymond Piggott |author3=John R. Piggott | year=2003 | location=New York | page=276 | isbn=978-0306477065}}</ref> The second column (called the rectifier) carries the [[Ethanol|alcohol]] from the wash,<ref>{{cite web | url=http://www.hmrc.gov.uk/manuals/spirmanual/spir4110.htm | title=SPIR4110 - Technical guidance: Stages of production: Continuous Distillation | publisher=Hmrc.gov.uk | accessdate=24 March 2014}}</ref> where it circulates until it can condense at the required strength.

A column still is an example of a [[fractional distillation]], in that it yields a narrow fraction of the distillable components. This technique is frequently employed in chemical synthesis; in this case, the component of the still responsible for the separation is a [[fractionating column]].

A continuous still can, as its name suggests, sustain a constant process of distillation. This, along with the ability to produce a higher concentration of alcohol in the final distillate, is its main advantage over a pot still, which can only work in batches. Continuous stills are charged with preheated feed liquor at some point in the column. Heat (usually in the form of steam) is supplied to the base of the column. Stripped (approximately alcohol-free) liquid is drawn off at the base, while alcoholic spirits are condensed after migrating to the top of the column.

Column stills are frequently used in the production of [[grain whisky]] and are the most commonly used type of still in the production of [[Bourbon whiskey|bourbon]] and other American whiskeys. Distillation by column still is the traditional method for production of [[Armagnac (drink)|Armagnac]], although distillation by pot still is allowed. The use of column stills for the distillation of [[Cognac (drink)|Cognac]] is forbidden, although they may be used for other types of [[brandy]], likewise malt [[Scotch Whisky|Scotch Whiskies]] must be distilled in a pot still.  Distillation by column stills is permitted for [[Calvados (brandy)|Calvados]] AOC and Calvados Domfrontais.  Calvados Pays d'Auge AOC is required to be distilled by pot still.

===Difference between pot still and column still===
Column stills behave like a series of single [[pot still]]s, formed in a long vertical tube. The tube is filled with either porous packing or bubble plates. The rising vapour, which is low in alcohol, starts to condense in the cooler, higher level of the column.  The temperature of each successively higher stage is slightly lower than the previous stage, so the vapour in equilibrium with the liquid at each stage is progressively more enriched with alcohol. Whereas a single pot still charged with wine might yield a vapour enriched to 40–50% alcohol, a column still can achieve a vapour alcohol content of 96%; an [[azeotrope|azeotropic]] mixture of alcohol and water. Further enrichment is only possible by absorbing the remaining water using other means, such as hydrophilic chemicals or [[azeotropic distillation]], or a column of 3A [[molecular sieve]]s, like 3A [[zeolite]].<ref>{{cite journal |last1=Burfield |first1=David R. |last2=Hefter |first2=Glenn T. |last3=Koh |first3=Donald S. P. |title=Desiccant efficiency in solvent and reagent drying 8. molecular sieve column drying of 95% ethanol: An application of hygrometry to the assay of solvent water content |journal=Journal of Chemical Technology and Biotechnology. Chemical Technology |volume=34 |issue=4 |pages=187–194 |language=en |doi=10.1002/jctb.5040340408 |date=1984|bibcode=1984JCTBC..34..187B }}</ref><ref>{{cite journal |last1=Simo |first1=Marian |last2=Sivashanmugam |first2=Siddharth |last3=Brown |first3=Christopher J. |last4=Hlavacek |first4=Vladimir |title=Adsorption/Desorption of Water and Ethanol on 3A Zeolite in Near-Adiabatic Fixed Bed |journal=Industrial & Engineering Chemistry Research |volume=48 |issue=20 |pages=9247–9260 |doi=10.1021/ie900446v |date=21 October 2009}}</ref>