One way of speeding up the operation of an existing still is to increase the boiler power. As long as you do not get into channeling or choking, this will work very well. Many people have reported being able to run a 50mm (2") column at 2 kW, and a 75mm (3") one at 4 kW. We would not recommend trying power levels any higher than these!
Your condenser(s) must be able to handle the vapor load created at higher power. The standard reflux coil can easily handle 2000 to 3000 Watts, depending upon cooling water temperature and flow rate. You should test this by distilling some water to make sure yours is adequate (see Chapters 3 and 4 where we discuss matching boiler and condenser performance).
If you are using electric heating and know the power being applied, you can calculate the new rate of vapor production and hence the amount of product to capture to maintain the desired reflux ratio. If you don't know the exact power you are using, you will need to determine the new rate of production by temporarily reducing the reflux to zero (best done with just water in the still) and collecting 100% of the condensate. When you know how many ml/min of condensate are being produced, you will know how to set the still to achieve the desired ratio. However, if using liquid management, please remember that the reflux ratio will vary with the composition of the vapor because you are drawing off liquid at a constant rate. If you draw off 4 ml of water every minute when testing, then you need to compensate for the lower density of ethanol, and draw off 4 ^ 0.8 = 5 ml of 96% ethanol every minute to maintain the same reflux ratio.
If you are using a vapor management still head then matters are simplified, because the valve settings are much simpler than with a needle valve and, once set, the reflux ratio will not vary. You can calibrate your valve once, and your settings will be good under all operating conditions.
The closer you operate to the edge of channeling or choking, the more watchful you will have to be in operating your still. We have talked about the tradeoff between time and quality - this tradeoff is between time and effort.
Once you are familiar and comfortable with the maximum operating power for your column, then you can increase the speed of a run by reducing the reflux ratio. You must do this very carefully, because the reflux ratio can have a direct impact on quality. It is possible in some stills to produce 95% ethanol with reflux ratios as low as 35-40%, but it will not necessarily be as "clean" as ethanol produced at 90% reflux. The only way to know the capabilities of your still is to experiment.
The best way to do this experiment is to establish a run at 90% reflux and collect some product. Then switch collecting bottles and reduce the reflux ratio to 80%. Allow the still to operate for ten or fifteen minutes to stabilize under the new conditions, switch bottles again, and collect some 80% reflux product. Repeat the process for 70%, 60%, etc. It is important to let the still stabilize at each reflux ratio before collecting sample that you will test. Watch the temperature of the vapor like a hawk! As soon as it starts to rise, you are no longer making 95% ethanol, and have entered the regime of a fractionating still instead of a compound still.
You can continue the experiments in the fractionating regime, but you will now be making product more suitable for aging into a whiskey or brandy than pure ethanol.
After collecting all the samples, compare the samples taken under stable conditions at each reflux ratio for taste and smell. If you can tell no difference at all, you might be able to safely operate at lower than 90% reflux. Every still and every operator are different, and only you can make this decision.
Before you make a firm commitment to a lower reflux ratio, the final test is to invite friends to carry out an independent test to see if their palate can detect any differences between the samples. If you do lower your reflux ratios, the final test is whether the product produces a headache the next day. Congeners are the primary source of hangovers, and removing them completely is the main purpose of the compound still.
Was this article helpful?
Discover How To Become Your Own Brew Master, With Brew Your Own Beer. It takes more than a recipe to make a great beer. Just using the right ingredients doesn't mean your beer will taste like it was meant to. Most of the time it’s the way a beer is made and served that makes it either an exceptional beer or one that gets dumped into the nearest flower pot.