Column still
Encyclopedia
A column still, also called a continuous still, patent still or Coffey still, is a variety of still
consisting of two column
s invented in 1826 by Robert Stein, a Clackmannanshire
distiller, and it was first used at the Cameron Bridge Grain Distillery in Fife
, Scotland
. The design was enhanced and patented in 1831 by an Irishman
, Aeneas Coffey
. The first column (called the analyzer) has steam
rising and wash
descending through several levels. The second column (called the rectifier) carries the alcohol
from the wash where it circulates until it can condense at the required strength.
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 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
.
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 pre-heated 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
. Distillation by column still is the traditional method for production of Armagnac
although distillation by pot still is allowed. The use of column stills for the distillation of Cognac
is forbidden. Distillation by column stills are permitted for Calvados
A.O.C. and Calvados Domfrontais. Calvados Pays d'Auge A.O.C. is required to be distilled by pot still.
Still
A still is a permanent apparatus used to distill miscible or immiscible liquid mixtures by heating to selectively boil and then cooling to condense the vapor...
consisting of two column
Column
A column or pillar in architecture and structural engineering is a vertical structural element that transmits, through compression, the weight of the structure above to other structural elements below. For the purpose of wind or earthquake engineering, columns may be designed to resist lateral forces...
s invented in 1826 by Robert Stein, a Clackmannanshire
Clackmannanshire
Clackmannanshire, often abbreviated to Clacks is a local government council area in Scotland, and a lieutenancy area, bordering Perth and Kinross, Stirling and Fife.As Scotland's smallest historic county, it is often nicknamed 'The Wee County'....
distiller, and it was first used at the Cameron Bridge Grain Distillery in Fife
Fife
Fife is a council area and former county of Scotland. It is situated between the Firth of Tay and the Firth of Forth, with inland boundaries to Perth and Kinross and Clackmannanshire...
, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
. The design was enhanced and patented in 1831 by an Irishman
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
, Aeneas Coffey
Aeneas Coffey
-Biography:Coffey was born in Calais, France, where he spent his early years. His family returned to Dublin , where he was educated at Trinity College, Dublin. He entered the excise service around 1799–1800 as a gauger...
. The first column (called the analyzer) has steam
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...
rising and wash
Wash (distilling)
In the production of distilled beverages, the term wash is used to refer to the liquid produced by the fermentation step, which is the input to the distillation process which concentrates the alcohol.-See also:...
descending through several levels. The second column (called the rectifier) carries the alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
from the wash where it circulates until it can condense at the required strength.
Column stills behave like a series of single pot still
Pot still
A pot still is a type of still used in distilling spirits such as whisky or brandy. Heat is applied directly to the pot containing the wash or wine . This is called a batch distillation ....
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 azeotropic
Azeotrope
An azeotrope is a mixture of two or more liquids in such a ratio that its composition cannot be changed by simple distillation. This occurs because, when an azeotrope is boiled, the resulting vapor has the same ratio of constituents as the original mixture....
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
Azeotropic distillation
In chemistry, azeotropic distillation is any of a range of techniques used to break an azeotrope in distillation. In chemical engineering, azeotropic distillation usually refers to the specific technique of adding another component to generate a new, lower-boiling azeotrope that is heterogeneous...
.
A column still is an example of a fractional distillation
Fractional distillation
Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate. It is a special type of 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
Fractionating column
A fractionating column or fractionation column is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities...
.
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 pre-heated 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
Grain whisky
Grain whisky ordinarily refers to any whisky made from at least some grains other than malted barley, such as whisky made using maize , wheat or rye....
. Distillation by column still is the traditional method for production of Armagnac
Armagnac (drink)
Armagnac is a distinctive kind of brandy or eau de vie produced in the Armagnac region in Gascony, southwest France. It is distilled from wine usually made from a blend of Armagnac grapes, including Baco 22A, Colombard, and Ugni Blanc, using column stills rather than the pot stills used in the...
although distillation by pot still is allowed. The use of column stills for the distillation of Cognac
Cognac (drink)
Cognac , named after the town of Cognac in France, is a variety of brandy. It is produced in the wine-growing region surrounding the town from which it takes its name, in the French Departements of Charente and Charente-Maritime....
is forbidden. Distillation by column stills are permitted for Calvados
Calvados
The French department of Calvados is part of the region of Basse-Normandie in Normandy. It takes its name from a cluster of rocks off the English Channel coast...
A.O.C. and Calvados Domfrontais. Calvados Pays d'Auge A.O.C. is required to be distilled by pot still.
