The Coffey still

Figure 13. The Coffey still of 1830 for distilling alcohol from fermented mash, using perforated plates. 1, Boiler. 3, Stripping column. 4, Rectifying column. 6, Feed. 8, Condenser.

Figure 13). In such a still 85% ethanol could be produced from an initial 5% of ethanol. The Coffey still was the forerunner of the modem column, and its efficiency in separating close-boiling fractions led later to its adoption for hydrocarbon separations, e.g. Coupiers benzole still (1863) for purifying benzene from toluene. Partial condensation also improved the separation achieved in the Coupier still.

Figure 6.1 The Coffey still for the separation of ethanol from a fermented beer mash 1, boiler 2, spent mash chamber 3, stripping column (analyser) 4, rectifying column 5, residual mash (stillage) outlet 6, fermented mash (feed) 7 feed pump 8, condenser 9, product tank. From Packowski, G. I. (1978), in Encyclopedia of Chemical Technology, Vol. 3, 851... 

In many of the still-heads employed on the large scale, for example the Coffey still (Fig. 58, p. 202) the condensed liquid is made, by means of suitable obstructions, to collect into shallow pools, and the ascending vapour has to force its way through these pools very good contact is thus brought about at definite intervals between vapour and liquid. The excess of liquid is carried back from pool to pool, and finally to the still by suitable reflux tubes. It is convenient to reserve the term dephlegmator for this particular class of still-head. 

Continuous Distillation on Large Seale.—Continuous distillation of wort has long been carried out on the large scale by means of the Coffey still (p. 202) but it is only quite recently that any attempt has been made to devise a process of the kind suitable for laboratory purposes. 

The Coffey Still.—Various alterations in the still have been made in order to make the process of distillation a continuous one. In this country very strong spirit is... 

The first successful attempt on continuous distillation and improved efficiency as well as profitability was the Coffey Still in 1831. It was used to produce Whisky. The Coffey Still consists of two columns called analyser and rectifier. The fermented feedstock is preheated against condensing vapours in the rectifier and fed at the top of the analyser. The liquid flows over a copper plate with openings and from there into a down-comer leading onto another, underlying plate, and so on. More than 10 perforated plates (called trays) are typically installed in the analyser. 

Low Wines. Low wines is the term for the initial product obtained by separating (in a pot or Coffey still) the beverage spirits and congeners from the wash. Low wines are subjected to at least one more pot still distillation to attain a greater degree of refinement in the malt whiskey. 

There are two kinds of Scotch whislg malt whisky, which is made by the pot still process, and grain whisky, which is made by the patent still (or Coffey still) process. Malt whislq is made from malted barley only, whereas grain whislg is made from malted barley together with unmalted barley and other cereals. 

Feints. Feints are the third fraction of the distillation cycle derived from the distillation of low wines in a pot still. This scotch term is also used to describe the undesirable constituents of the wash that are removed during the distillation of grain whiskey in a continuous patent still (Coffey). These are... 

Distillation is an ancient unit operation, and has been widely practiced for thousands of years. Early applicetions used crude vaporization and condensation equipment, often for concentrating the alcoholic content of beverages, The first vertical columnar continuous distillation still was developed by Cellier-Blumenthal in France in 1813. Perrier introduced an early version of the bubble-cep tray in England in 1822, Packings were used as early as 1820 by a technologist named Clement who used glass balls in an alcohol still. Coffey developed the first sieve tray column in 1830. The first book on fundamentals of distillation was La Rectification de I alcohol by Ernest Sorel in 1893. 

Patent Stills,—By far the greater quantity of ordinary alcohol is distilled in a patent still, the invention of Aeneas Coffey. In this process the alcohol is expelled by blowing steam through the wash which is spread in layers over a considerable surface. The wash enters at the top of the still and passes downwards over a series of perforated copper plates in which are small orifices, where the liquid is... 

In 1830 Aeneas Coffey of Dublin designed a still which operated continuously and gave good alcohol separation (31). He fed the preheated mixture of water and alcohol (from fermentation) into a vertical series of shallow chambers placed one on top of the other, separated from each other by perforated plates, heated by live steam, and using refiux see... 

The alchemists of the Middle East were familiar as early as the first century AD with the technique of distillation which was necessary to separate the ethanol from the water. Indeed, developments of their simple pot stills were used to prepare concentrated spirits with a high ethanol content (say 500 g 1 well before the Industrial Revolution. Yet the true industrial production of ethanol directly from a crude fermentaion broth with its high solids content became possible only after Aeneas Coffey, working in Dublin, developed his multistage continuous still in 1830 (Figure 6.1). The last traces of water in the azeotrope which the still produced were removed with a drying agent. 

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