Column still
A column still, also called a continuous still, patent still or Coffey still, is a variety of still consisting of two columns.
History
Sir Anthony Perrier
Sir Anthony Perrier (1770–1845) was operator of the Spring Lane distillery (Glen distillery) in Cork, Ireland from 1806. In 1822 he patented one of Europe's first continuous whiskey stills, a method that during distillation allowed the mash to flow gradually and continuously over the heat through a labyrinth of partitions. This meant small portions of fermented "wash" received the greatest amount of heat, thereby increasing the amount of potable alcohol that was collected.[1]
Robert Stein
In 1828, Perrier's invention inspired a Scotsman, Robert Stein, to create a still that fed the "wash" through a column of partitions. He called it a "patent still". It was first used at the Cameron Bridge Grain Distillery in Fife, Scotland. Despite numerous presentations in the British Isles and in Europe, he never got the financial support needed to get his project off the ground and into the distilleries. However, a demonstration of Stein's still observed by a Dublin excise tax collector (or "gauger") yielded the greatest result.[2]
Aeneas Coffey
The design was to be improved and patented by an Irishman, Aeneas Coffey. Educated at Dublin's Trinity College, Coffey had ample opportunities to observe all manner of still designs because he had worked for a quarter of a century as an excise tax collector. He knew how much could be produced in a given period of time. He also knew that the new continuous stills had a flaw. To obtain a higher proof spirit, receiving vessels had to be changed so multiple distillations could take place.[3]
Coffey opened the Dock Distillery on Grand Canal Street in Dublin. The main feature of his operation was a customised still of his own design—or rather Stein’s design with a minor modification. Coffey inserted two pipes into Stein’s column still that allowed a greater portion of the vapours to re-circulate into the still instead of flowing into the receiver with the spirit. This eliminated the need for multi-distillation and produced a spirit with a higher proof and lighter character. In 1830, he was granted Patent #5974 for his design, a two-column continuous still.
Nearly every liquor producer in Europe and the Americas embraced Coffey's new continuous column still. Cuban rum, gin, vodka, blended Scotch whisky, and blended Irish whiskey all gained new stature as output went through the roof and the character of the spirit became smoother and generally more palatable. Within five years of receiving his patent, Coffey had enough orders to warrant the establishment of Aeneas Coffey & Sons in London, a company that remains in operation today under the name John Dore & Co Limited. He closed Dock Distillery four years later and devoted all of his time to building and installing stills in distilleries owned by others. At the time, Irish distillers were the dominant force in global whiskey production. Unfortunately for Coffey, his invention was shunned by the Irish who considered the whiskey produced from his still as bland and tasteless. They decided to persevere with their famous pot still whiskey and Coffey was forced to look overseas and to Scotland in particular.
Description
The first column (called the analyzer) in a column still has steam rising and wash descending through several levels.[4] The second column (called the rectifier) carries the alcohol from the wash,[5] where it circulates until it can condense at the required strength.
Column stills behave like a series of single pot stills, formed in a long vertical tube. The tube is filled with either porous packing or bubble plates. The rising vapor, 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 vapor 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 vapor enriched to 40–50% alcohol, a column still can achieve a vapor 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 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 and other American whiskeys. 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 AOC and Calvados Domfrontais. Calvados Pays d'Auge AOC is required to be distilled by pot still.
References
- ↑ Anthony Perriers Patent Submission- Improved Distillation Apparatus (P.10)
- ↑ December 1828 Patent for Stein
- ↑ Kerr, J. J. (December 1946 – February 1947). "Aeneas Coffey and His Patent Still". Dublin Historical Record. 9 (1): 29–36. JSTOR 30079327.
- ↑ Andrew G. H. Lea; John Raymond Piggott; John R. Piggott (2003). Fermented Beverage Production (2nd ed.). New York: Kluwer Academic/Plenum Publishers. p. 276. ISBN 0306477068.
- ↑ "SPIR4110 - Technical guidance: Stages of production: Continuous Distillation". Hmrc.gov.uk. Retrieved 24 March 2014.
