Part 3: Distillation of Grain Spirit

1. Part 3: Distillation of Grain Spirit Continuous Distillation Maturation Blending and Packaging

2. Distillation of Grain Spirit • Grain spirit derived from a mash containing ~90% unmalted cereal • Produced using continuous distillation (Coffey still in Scotland) • Relatively few, but large distilleries, producing as much as 60 million litres of alcohol per annum • Highly rectified spirit (~94% abv); matured and used as a base for blending with malt whiskies • Also provides feedstock for production of neutral spirit

3. A Model Continuous Distillation Column

4. Operation of a Continuous Distillation Column • Steam sparging at the base of the column provides heat • Liquid flows across feed plate into the distillation column • Downcomer pipes permit the liquid to flow down through a series of sieve plates • Holes in the sieve plates permit vapours to pass upwards through the column • The stripping section below the feed plate separates the more volatile from the less volatile components • The rectifying section above the sieve plates concentrates the more volatile components

5. Internal Design of a Continuous Distillation Column

6. Column Design: the Sieve Plates • Sieve plates are designed so that a low level of liquid (up to 5 cm) collects on the plate area • Holes must be sufficiently small so that upward vapour velocity can prevent weepage, but sufficiently large to prevent blockage • Weirs surrounding the downcomers prevent vapours from flowing up the downcomers, and allow the level of liquid on the plate to be controlled • Vapour velocity must be sufficiently slow to allow adequate mixing of the upcoming vapour and the liquid on the plate

7. The Coffey Still

8. Operation of the Coffey Still • Wash is pre-heated through a rectifying column (30-35 plates); this also increases internal reflux of the column • Pre-heated wash is then fed into the top of a stripping column (the analyzer) • Vapours (30 to 40% abv) from the top of the analyzer are fed into the base of the rectifying column • Reflux occurs from the base of the rectifying column to the top of the analyzer • Product (~94% v/v ethanol) is drawn 5-10 plates from the top of the rectifying column

9. Changes in Vapour Composition in a Coffey Still

10. Composition of New-Make Grain and Malt Spirit(after dilution for cask filling)

11. The Barbet Still • Widely used in the production of neutral and light spirits in Europe and South America • Uses a heads removal section above the stripping column to remove some of the more volatile components before they reach the rectifying column • The heads removal section prevents CO2 build-up in the rectifier and provides better control of some congener levels in the rectifying column • Disadvantage of the Barbet system is that alcohol losses are higher (compared to Coffey still)

12. The Barbet Still