Reflux Still Design

To increase the purity of the alcohol, and hence reduce the amount of "off-flavours" in it, you need to use a taller column, packed with something which has a large surface area (scrubbers are best), and have some of the vapour condensing and being returned back down over the packing as a liquid (reflux).

For a certain height of packing (called the HETP), the purity will improve - roughly 1x = approx 85% purity, 3x = 90%, 5x = 93%, and 7-9xfor 95%+. Just make it as high as what you want pure. For scrubbers the HETP is about 10cm (4 inches), whereas it is 24-38 cm (10-16 inches) for raschig rings or marbles.

See my Detail of the Equations used if you want to get into the detail of this.

Purity is improved during distillation by allowing the rising vapour to mingle with some liquid at a slightly cooler temperature. In doing so, some of the water rich vapour will condense, supplying a bit of energy to allow some alcohol rich vapour to form from the liquid , and join the existing vapour. Each time this "mingling" is sufficient to reach equilibrium, the purity takes a "step" on the graph below:     This page last modified Tue, 20 Jan 2015 20:51:05 -0800