Unit 5 - Continuous Distillation - School of Life Sciences

Unit 5: Continuous distillationFigure 1. Coffey StillThe feeds into the still are wash entering the top of the rectifier andsteam entering the base of the analyser. The stills are divided into anumber of rectangular sections, separated by perforated trays, orplates,and in each of them there is countercurrent flow.The wash, at about 34°C, enters the top of the rectifier in a coppertube, which winds its way between the trays and moves from onesection to another via bends, which protrude from the still. In itsdescent the wash temperature rises as it contacts hot vapour fromthe analyser and by the time it reaches the bottom its temperature isabout 94°C. It is then directed to the top of the analyser and flows outof the pipe and cascades down the trays. It passes from tray to traythrough a series of downpipes,which create a flow across the trays,and at each tray it meets vapour forcing itself upwards through theperforations.The wash is stripped of its alcohol gradually as it descends andconversely the vapour becomes progressively richer in alcohol as it© 2001 The International Centre for Brewing and Distilling 6