Understanding your column means managing your column!


This is a post for those running an iStill 250 or 500. And for those considering buying one. In this post I will explain the inner workings of the column, and focus on “Do’s and Don’ts”. We bring 21st Century distillation equipment to the market place. For many distillers, stepping up a few centuries in one go (by purchasing the iStill 250 or 500, for instance) it takes some understanding of what we do and how our technology works. This post will help you understand, so you can manage what goes on inside your iStill easier … and manage the column as well as possible.

Design approach

Any still basically has three operational phases:

  1. Off;
  2. Heat-up;
  3. Production.

Since the second phase, heating-up, is not producing anything, it is pretty much a waste of time. Ergo? We want to minimize the heat-up time. How? By giving the still twice the power it actually needs for the production phase. Twice the power means, you can half this unproductive heat-up phase. But there is a risk associated with that advantage: the rig –  under production – is designed to work optimally with half the power. Shorter heat-up times inherently mean that there is a risk of running the rig too fast.

How we solved that

We solved that by automating and robotizing the iStills 250 and 500. And we gave these units “eyes & ears” in the form of thermometer probes, that the computer uses to monitor what’s going on.

Heating-up automatically starts at 18 kw. When the temperature at the stabilization probe (Tst) reaches 45 degrees C, the computer understands that the boiler contents must be boiling, since the temperature in the column is slowly rising. The rising temperature inside the column is caused by rising gases. In order not to overwhelm the column with too much gas, the iStill now automatically dials the power input back to 9 kw, while opening the solenoid for water in at the same time.

If the iStill 250/500 automatically dials in the right power setting for the production phase, that is now eminent, what’s the problem? Well, usually there is no problem, but in some instances – even with the automatic power setting – the column may flood.

Column flooding, what is it?

The column management system of the iStills cools all gases, that rise up from the boiler, down to liquids. Part of these liquids are taken as product, other parts are returned down the column as “reflux”. Reflux, re-entering the column, activates the packing, so that the column contents gain in ABV. The alcohol gets stronger through multiple additional redistillations of the reflux.

Column flooding is the situation where there is too much reflux in the column. Due to the excessive amounts of reflux gases cannot enter the column freely anymore. And reflux amounts are so big that draining liquids back into the boiler becomes problematic.

We want to prevent column flooding, because it causes performance issues both in quality and in quantity of the product you are makng. We can recognize flooding by listening to the column. Does your iStill 250/500 sound as if it is mimicking a helicopter? That’s a clear signal: column flooding  is starting.

What to do?

What you need to do, if you hear your column is flooding? Easy, dial the power back by 1 kw. Give the column 5 minutes and if she is still flooding, dial back the power input some more.

But what if the column is flooding, while you are running an automated program? The iStills are supposed to dial back from heating-up power input to production power input (9 kw) automatically, right? Right. So what can be amiss, when you are running your column at the automated setting of 9 kw … but you still get column flooding? Let’s dive in deeper.

Compressed packing

Due to transport the packing in the column can be compressed. Compressed packing limits the amount of open space inside the column, hampering depleted reflux to return to the boiler.

The solution is easy. Take out the packing, remove any broken parts, then slowly poor the packing back, while holding the column at a 45 degree angle. You will find you will have some packing left, while the column is filled completely. Good!

Dirty packing

What if the copper SPP gets oxidized? Or what if you had boil up of a wash that was not well converted? Your packing becomes thicker. Again, and as above, the ability of the column to drain depleted reflux into the boiler is handicapped, making it more vulterable to column flooding.

Again, the solution is easy. You clean the packing. Go to the Search Function on the iStill Blog, search for “Cleaning” and you will get further instructions on how to do this.

Overfilled boiler

Some people fill the boiler with close to 300 liters instead of 250 liters. As a result, liquids can boil up in the column. By now, you will understand that liquids boiling up … prevent depleted reflux to be drained into the boiler.

The solution is to empty the boiler partially, and restart the run. Take into consideration that especially higher ABV boiler charges contain lots of alcohol … and that alcohol expands while heated …

Overcharged boiler

This is the situation where you maybe put just 200 liters of low wines in the boiler, but forgot to dilute it, so the ABV is like 50% (just an example). Now, the packing we use is increadibly effective. In laboratory situations we are able to create pure azeotropic alcohol in just 11 centimeters. In plain English? The columns of the iStill 250/500 can take any boiler charge to 95% with ease.

Here comes the catch: the iStill 250/500 column can take a gas that is richer in alcohol to pure azeotropic temperatures even easier!

As a result, when you charge the iStill with too high ABV boiler charges (> 35%), the column will turn the gases into pure azeotropic temperatures/percentages in just 15 to 20 centimeters from the column entrance. And since temperatures cannot drop lower than the boiling point of pure alcohol, these pure gases, meeting higher temperatures higher up in the column, will condense and block the column.

Summary? If you charge the iStill 250/500 with higher than 35% alcohol in the boiler, you are prone to develop a situation called “ethanol blockage”, where pure ethanol blocks the column.

The solution? Dilute your boiler charge. Do make sure you don’t overfill it, while watering down, though!

Manual override of power settings

If, during heat-up, you decide to alter power settings manually, the computer asumes you take control of the iStill. Instead of automatically switching down the power input from 18 to 9 kw, it will follow your command. Say, you dialed in 12 kw during the heat-up phase. The iStill will now keep on running at 12 kw, also during the production phase. And 12 kw creates a lot of power and reflux. So much, that it may start flooding the column.

The solution? Run the iStills automatically. And if you want to make power adaptions, do so at the beginning of the production phase only.

Defeating Newton (or trying to …)

Sometimes customers try to defeat Newton. For instance by collecting product in a very high container. If the result is that the liquids have to travel upwards … well, that just doesn’t happen. Simple Newtonian Science. Liquids (at least over here) travel down the stairs, not up the stairs.

Something as simple as a kinked silicone hose, or too high a collection vessel, or a needle-valve section that is attached higher instead of slightly lower than the collection spoons at the bottom of the column cooler, may cause product to be returned down the column … creating additional reflux the column has to deal with.

Too high electric power input to start with

The iStill 250/500 series is tuned for 400 volts in Europe and 208/220 volts in North America. In Europe, 400 volts is just that … 400 volts. In North America we often find that electrical specifics may vary. And sometimes they vary quite significantly.

Imagine you run your iStill 250/500 at 250 volts instead of 220 volts. That’s like throwing 15% more power at it. Someting like 10.2 kw instead of 9 kw during the production phase. More power input creates more gases. More gases result in more reflux. Too much reflux may cause column flooding.

The solution is to dial back power input during the production phase. Try setting it at 8 kw and see how things go. The proof of the pudding is in eating, so just take measurements of output per hour and ABV. If the ABV is 95% or more, in Pure Mode, you are running within set specifications. In other words: you are fine. If the output (for example on a 30% low wines charge) is above 10 liters per hour, you are fine too.

An example

Here is an example of a customer that experienced column flooding. He did so at the first alcohol run, with all automated settings.

When we talked to him via Skype, the first thing we learned is that his wash was only half way done. Instead of the 12% he had aimed for, it was at 6% only. It was still bubbling away, when he put it in the boiler. Our conclusion was that the gas rich wash boiled up into the column, so we adviced him on fermentation procedures and degasing procedures. We told him to clean out the column as well. The packing may have gotten a lot of sugars on them. And the rig being new … the packing might be overcompressed from transport.

After following up on our advice, the customer did another run with his iStill 250. He experienced column flooding again. He showed us how he had assembled the still and we quickly saw that he had put the needle-valve sections above instead of under product take-off. He was trying to outwit Newton, unintentionally. We told him how to assemble the rig correctly, and asked him to do another run.

Unfortunately, he experienced column flooding again, so I asked him to look at the power input system. The electric panel and what power he was feeding to the iStll. His electrician told us that he was feeding the iStill 250 with 250 volts instead of 208 – 220. Eureka! We found the problem and solved it. How? This customer is now running the iStill 250 at the 8 kw setting instead 9 kw, during the production phase. The higher voltage gives more power and mean that he actually runs at a total power input closer to 9.2 kw.

The results he got? An output of 96% in pure mode. At 14 liters per hour. What we got? Another happy customer.


Our rigs have new technology that no-one before us brought to the market place. New technology works differently than old technology. It therefore asks for new learning to take place, so you understand how this new technology works, how it helps you out, and how you can solve any problems you encouter.

I hope this iStill Blog post helps you to better understand the huge innovations we made. Part of being a Master Distiller is understanding what goes on inside your still. If for no other reason, because understanding improves your ability to manage the whole distillation process.

Regards, Odin.



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