The iStill’s computer display

The iStill 50 is a fully automated Liquid Management still, it is computer operated (or at least controlled)  and has a display. But what does that display tell us? An explanation.


“Production process” means just that: the iStill is producing product.

“Opening : 21” tells us that the needle valve is set at opening position 21. All open would read “24” and all closed would be shown as “0”. This tells us that the iStill is drawing off at a pretty fast rate. At about 85 to 90% of maximum speed.

“POT: 48” tells us the potentio meters controlling the automated stepper motor are working correctly and get feed back. It is the one number we don’t have to look at acutally.

“T_in: 88.0” means that the temperature of the refluxing distilate in the lower parts of the column is 88.0 degrees Centigrade. The T_in is the temperature measurement at the bottom of the column. In this case, this tells me that the lower parts of the column are being bled off of pure ethanol. How I know this? Because in the beginning of a product draw off, the temperature at the bottom of the column is very close to azeotropic temperatures. Think 80, maybe 81 degrees Centigrade.

“T_pe: 21” means that cooling water temperature is 21 degrees. If it would rise to above 35 degrees due to cooling problems (cooling water supply), the iStill shuts down automatically.

“T_da: 78.3” informs us about the actual, pressure corrected, boiling point of pure azeotropic ethanol. It sets a base line for product collection. This base line tells us what, given the weather conditions and how high up you live, is the current azeotropic temperature.

“T_st: 78.5” is the reading of the temperature probe higher up in the column. It is situated about 25 centimeters (10 inches) under the product take-off point. In this case a temperature tolerance of 0.3 degrees was chosen. That means that the iStill will collect product when the temperature 25 centimeters under the take-off point is between 78.3 (T_da) and 78.6 degrees Centigrade. This way, you will always be collecting at azeotropic temperatures and ABV.

When the T_st reaches 78.6 degrees, the iStill stops collecting. All rising gasses are refluxed down the column. The temperature at the bottom of the column, T_in will start dropping again, and so will the temperature closer to the top of the column.

When the T_st is at around 78.3 or 78.4 degrees again, the stepper motor will automatically re-open the needle valve. The automation will probably tell the iStill to chose a smaller opening, like 18 instead of 21. That way, the reflux ratio is upped, to correct for slowly depleting alcohol levels in the boiler.

Lower alcohol amounts in the boiler mean lower ABV gasses are fed into the column. In order to take off product at 96% all the time, the reflux is upped and the amount drawn of as product is decreased. This way the iStill can collect 96% strong alcohol all the time. Even when T_in is like 99.5 degrees.

We had some visitors to our showroom a week ago. We did a run together. I stopped the iStill when the T_in was like 97.5 degrees. The needle valve setting showed “11”. My guests asked me why I stopped. I told them I thought it was not worth collecting anymore at such a slow speed. The response I got?

“Slow speed!?!”, one of our visitors cried out, “it still pisses out product much faster than my own LM does at any given time!”

I guess “slowing down” is relative in this case. And it also taught me that it is very, very easy to grow accustomed to working with an iStill. And that it would not be very easy to move back to working with the rigs I ran before. Luckily there is no need for that!

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