COPPER POT STILL
Pot stills form the basis of batch distillation. This means a specified amount of liquid goes into the still and gets distilled into spirit.
Malt Whisky is distilled twice - although a few distilleries may undertake a third distillation - in Pot Stills which resemble huge copper kettles. The spirit is driven off from the fermented liquid as a vapour and is then condensed back to a liquid.
In the first distillation the fermented liquid, or wash, is put into the Wash Still. This is heated either directly by fire or by steam-heated coils. At this stage the wash contains yeast, crude alcohol, some unfermentable matter and the by-products of fermentation.
Copper is used because of its good malleability and heat conduction but also for its catalytic properties and the ability to neutralize some of the sulphur compounds and off-notes. The stills can be heated either directly by burning gas, peat or coal or indirectly by steam coils running inside the still.
As the wash boils, vapours pass up the neck of the still and then pass through a water-cooled condenser or a worm, a coiled copper pipe of decreasing diameter enclosed in a water jacket through which cold water circulates. This condenses the vapours and the resulting distillate, known as low wines, is collected for re-distilling.
The low wines are distilled again in the Spirit Still, similar in appearance and construction to the Wash Still but smaller because the bulk of liquid to be dealt with is less. Three fractions are obtained from the distillation in the Spirit Still. The first is termed foreshots, the second constitutes the potable spirit, and the third is called feints. The foreshots and feints are returned to the process and redistilled in the Spirit Still with the succeeding charge of low wines. The residue in the still. Called spent lees, is run to waste.
In the case of the Spirit Still, the design of the still, the height of the head (or top) of the still and the angle of the wide-diameter pipe or Lyne arm, connecting the head to the condensing unit, are all very important and have an effect on the distillate.
Copper removes most of the sulphur, cereal, feint and meaty aromas during distillation. Especially the copper contact of the first wash still distillation is important. Total removal of copper contact in the spirit still has surprisingly minimal effect on the mentioned off-notes.
- Design as per Good Engineering Practices.
- MOC: Copper.
- Internals: Heating Coils (Steam)
- Internals:(Copper / SS-304 /SS-316).
- Pot Still Dimensions: Dia up to 3500 mm of Bottom Shell with Hemispherical / Conical Top with Goose Neck (as per requirement).