Winegrowers Supplies  -  alcohol and temperature, and the danger of ignition.


Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable colourless liquid with the structural formula CH3CH2OH, often abbreviated as C2H5OH or C2H6O.

The boiling point of ethanol at atmospheric pressure (which is 1 bar at sea level) is 78.37 C.

The boiling point depends on the atmospheric pressure, decreasing as atmospheric pressure decreases.
Atmospheric pressure decreases with height above sea level, so the boiling point will be slightly lower than 78.37 C according to height above sea level.

The flash points of ethanol solutions from 10% abv (alcohol by volume) to 96% abv are:-

  10% 49 C  (another source says 52 C for wine containing 12.5% ethanol)
  20% 36 C
  30% 29 C
  40% 26 C
  50% 24 C
  60% 22 C
  70% 21 C
  80% 20 C
  90% 17 C
  96% 17 C
 100% 16.60 C

So, for example, an ethanol-water solution that contains 40% abv has the potential (if an ignition source is applied, such as an electric spark or a flame) to catch fire if heated above its 'flash point' of about 26 C.

Distillation in a Still can produce from 70% abv up to 96% abv, hence there is a high potential danger of ignition with explosive effect. It's essential to take every precaution against this occurring.

Practice varies throughout the industry.
Firstly, it is very rare that alcohol comes off the still at 96% abv; only vodka distillers achieve that. The collection tanks are enclosed and usually vented to atmosphere outside. Some producers continue to store at this strength to save on tank volumes, others dilute to about 50% soon after production.

Most gin distillers buy in their base alcohol. Legally this has to be at 96% abv but it will be diluted to around 50% before being put into the still. Smaller distilleries buy it in drums of 205 litres. These smaller, fully enclosed sizes are not considered to be so hazardous. Very large distilleries have it delivered in tanker loads and usually dilute soon after delivery.
Whiskies, brandies, schnapps etc are distilled to a lower abv.

Potential sources of ignition must be minimised, any equipment with an electric motor must be kept well away from the immediate vicinity.

Suitable pumps must be ATEX rated, these are air-diaphragm pumps which are powered by compressed air from a compressor located in another room.


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