Originally By Tony Ackland

## Calculate the HETP for your still ...

For a full description, see Reflux ratio

 Select Packing Type(note: the values these selections generate are only approximate guesses) Material Diameter Surface Area Surface Tension Marbles 0.010 m 50 m2/m3 0.061 N/m 6 mm Raschig rings 0.006 m 140 m2/m3 0.061 N/m 13 mm Raschig rings 0.013 m 40 m2/m3 0.061 N/m Stainless Steel Wool 0.001 m 800 m2/m3 0.075 N/m or your own values ... m m2/m3 N/m Still Characteristics Column Diameter m Packing Height m Reflux Ratio Power Input W

 Estimate of Packed Column Performance Height Equivalent of Packing (HETP): m Number of Theoretical Plates :   = (height/HETP) + 1 for pot Approx Vapour Purity : %

See http://www.raschig-rings.com for more information on other column packing details. Note also that when real plates are used in a column, you also need to do a similar calculation - they are often far from ideal in operation, and you may need several to achieve one HETP.

Jan Willem experimented with this ...
I get 94% at a rate of ~ 500mL/hour. My column is 115cm long and 42mm wide Filled with potscrubbers from the undersite to just under the precooling coil. (Tony - ie its of a good design already - heaps of HETP)

At my latest distilling escapade I turned the reflux ratio up. Just as a test that would show me how pure it could get AND if there was a taste diffirence (after dilluting ofcourse) Collected the good stuff at 100mL/hour (a long wait) Then the score was initialy 95.?% and was going down a bit to 94.5% (Dunno if it was 94.3 or 94.8 so I say 94.5%) After the taste test I noticed NO difference, but I'm no expert at wodka tasting.

The improvement isn't linear either - you can halve the HETP for Stainless Steel Wool (SS below) by going from "bugger-all" reflux to "some" reflux, but there is little improvement winding it up too far past there.

SS = Stainless Steel Wool Scrubbers, RR6 = 6mm Ceramic Raschig Rings,
RR13 = 13mm Ceramic Raschig Rings, M = 10mm Marbles