Fusel side draw experiment

[Edwin Croissant]

For a theoretical background for this experiment see ABV dependent volatility of fusel oils

ketel3 and I did an experiment with the objective to test cheap peristaltic pumps as a substitute for a needle valve and to find out the effect of removing the fusel alcohols (tails) oil through side drawing from the column at approximately 10 cm from the bottom. I will not discuss the benefits of these pumps as distillate pump as they contain about 15 cm of silicone tubing and are therefore against the rules of this forum. As long as the fusel draw is not consummated (I can't imagine that anyone will be tempted to do so) or is reused, the use of such pump is a cost effective way to control the flow rate.

Ketel3 adapted his column with a side connection for the withdrawal of the fusel alcohols and placed a temperature sensor in the middle.

I made a test box that controlled the two peristaltic pumps, record the temperature value in the middle of the column, and record the flow and volume of the fusel alcohols and the distillate. To measure the last two parameters little magnets were mounted inside the rollers of the pumps and Hall sensors were used to detect the passing of those magnets while the pump was running. An Arduino was used to display the quantity and flowrate of the distillate and fusel oil en to show the temperature in the mid of the column. The sensor used was a SMT172 TO18 with a resolution of 0.01 ºC The collected data was stored on a SD card. At the start of the test the fusel alcohols were withdrawn at a rate of about 10 cc/min, later during the run this was lowered to 5 cc/min.

The still was a 50 liter keg with a 50mm column. During the run power was about 1600 watt. Packing was loosely packed stainless scrubbers. Distillate and fusel alcohols were collected in jars.

Most of the fusel jars developed a 1 cm thick milky colored layer on top within a couple of minutes.

One of ketel3’s girlfriends works in the perfume industry and is equipped with a very good nose. Se sampled all of the distillate and fusel jars:

Wash was based on a of 11% sugar wash with a couple of cans of grape concentrate:
Distillate (5536 cc total ABV > 92%):
jar one: nail polish
jar two: not bad
jar three: sweet and useful
rest of the jars: excellent
last jar: faint hint of something but still acceptable. (200cc jar containing the very last of the ethanol in the boiler, ABV probably below 90%).

This batch was much better then previous ones distilled without the fusel alcohols side streaming.

Fusel oil (866cc total about 12% ABV)

All of the fusel jars had a very disagreeable odor, first one smelled like cognac, and one (jar 5 or so) had a rum caramel smell. Most of the jars made her nearly faint. Last fusel jar was tasteless water.

Fusel pump was a INTLLAB peristaltic pump, sold on AliExpress for about €5 including shipping. Pump tubing was changed to 4x2mm silicone tubing, interconnecting tubing was PTFE 3x2mm tubing.
Pump is 12V and can be controlled with a DC motor controller that cost less then €2 as sold on AliExpress. (The digital ones I used (about €4) are overkill but chosen as I was not sure if I could program the Arduino to display the flow rate at time of ordering) Fusel must be below 40C before entering the pump. (tape PTFE tube to cold coolant line for some distance)

After the test the conclusion was that the operation of the still was stable, the pumps operated flawlessly and the removal of the fusel alcohols at the bottom of the column gave a huge distillate quality improvement. Even the last jar that we squeezed out of the boiler was of acceptable quality. We also got the feeling that, based on the temperature reading of the mid sensor, the top part of the packing could be removed and the column could be shorted accordingly.

We know that this report lacks a lot of details as we had no idea what to expect but hope that this report is of some use.