Still with 60" packed Reflux column in operation
In previous articles 10.19 190 Proof Ethanol from Scratch, and article 15.8 Ethanol Fractionating Still, I discus how to produce 190 proof Ethanol, the difference being that the latter uses a reflux column to achieve 95% 190 proof concentration, while the former uses multiple runs in a vacuum pot still and mol sieve desiccant to achieve that end.
Underneath the towels, my test still is composed of a 6” X 12” boiling pot, with 5’ of 2” sanitary tubing stuffed with stainless steel ribbon from commercial pot scrubbers.
Vacuum still assembly with 36” column showing bead bath heating
Pot scrubber column stuffing from Hong’s Restaurant Suply
The boiling pot sits in a commercial electric soup pot full of aluminum beads supplied by Cascade Sciences, and there is a thermocouple in the boiling pot attached to a PID for heat control, and a thermocouple in the column head to determine the boiling point of the fraction currently in the column head.
The thermocouples were custom 1/8” Type J made by Wilcon Industries and inserted through 1/8” Swagelok compression fittings, that I through drilled so the thermocouple could pass all the way through.
Column head with thermocouple and compound pressure gauge
I insulated the column with 1” thick closed cell foam 2 1/8” pipe insulation and all hoses are 3/8” 304 stainless steel over braided PTFE with #6 JIC connectors.
For a condenser I used a 10 pass single row copper tube heat exchanger with aluminum fins and added a blower from another double row heat exchanger.
3/8” 10 pass single row copper vapor to air heat exchanger using Derale components
For a collection jar, I used a thumper lid from Nor Cal Brewing Solutions. It is set up with a connection to the test sled vacuum pump, so the system can also be run under -23” Hg vacuum as a vacuum still.
I will be running vacuum still experiment for comparison once I establish a baseline.
Thumper lid attachment from Nor Cal Brewing Solutions
For my first run, I diluted 190 proof Ethanol 50/50 with water, to produce about a 95 proof and put it through the still with a 2” X 36” reflux column in one pass. After it cooled down, the 36” column produced 185 proof ethanol, so I added another 24” of packed reflux column to see what that would produce.
At 26C/78.8F a single pass measured 195 proof, which when adjusted for temperature above 16C/60F comes out 190 proof.
Oops, New Reflux Still Column Sizing Insights!
Sooooo, I was so elated with achieving my 190 proof azeotropic balance goal with my small still, that I failed to consider all the variables using a larger boiling pot.
Sometimes experiments verify and support pet hypothesis, and sometimes they fly in the face of them for obvious reasons, which I failed to adequately consider.
In this case I attached the same 2” X 60” packed reflux column to the 12” X 12” pot, vis a vis the 6” X 6” still base and expected similar results, despite the 4X difference in surface boiling area producing vapors.
As a result, I only achieved 180 proof in a single pass, demonstrating that I need more refluxing mass cooling down the vapors, so that only the lowest boiling point reach the column head.
I again packed my boiling pot in aluminum beads from Cascade Sciences for even heating, but this time used a 14” baking pan sitting on a Chemorec 2 hot plate, instead of an electric soup pot.
Large Pot in Bead Bath
Large Pot In Operation Insulated and Wrapped
The run was smooth and uneventful, but demonstrated the need for more reflux area, which I don’t have room for in my kitchen, so will have to wait until I can move back in my garage lab/workshop or go to a larger diameter column.