Another Tuesday Tech Talk post! This time about … steady state distilling. What is it? Yes, some explaining is needed, especially since steady state distilling is not something that’s standard procedure. In fact, it is a terminology that I introduce here and now, to describe a certain approach to designing stills. A quite interesting one, that we will put to practice on the iStill 100 NextGen we are about to launch.
iStill 100 NextGen design challenges
When I started designing the iStill 100 NextGen, I wanted it to be an affordable unit that the Craft Distiller can use for small scale production or product development. At the same time I wanted it to be a still we can use ourselves to train our customers in the basics of distilling, prior to them taking the next step: automated and robotized distilling.
For the unit to be both “affordable” and “educational”, I wanted to start with a unit that had only very limited automation and robotization. That beefs up the learning experiences, while cutting costs dramatically on the smaller unit the i100 NG is.
The focus then became something like this: “Yes, we can make a unit that is operated via a manual needle-valve … but how can we design a unit that – given its size, column diameter, packing, power settings – can make both taste rich and pure product in the easiest way possible?”
The answer? Steady state distilling!
Steady State Distilling
Without all the automation and robotization in place to control and manage the iStill 100 NextGen, I had to come up with a solution that would make the unit as easy to manage and as good as running itself as possible. And that’s where steady state distilling comes in …
“Steady state distilling” is the situation where the rig, by structural design decisions, runs perfectly balanced as is, without any control action having to be undertaken, both when making taste rich and pure product. With the manual needle-valve now operating as a mere selector of the amount of taste versus purity the Craft Distiller wants.
What I needed to balance out, in order to achieve that steady state situation for the non-robotized iStill 100 NextGen, were quite a few parameters:
- Boiler size;
- Column diameter;
- Packing efficiency;
- Power input;
- Standard needle-valve opening.
The solution, I found, had to have the following specifications:
- Net boiler content of 100 liter;
- Column diameter of 3 inch;
- A newly designed, slightly bigger SPP as column packing;
- A steady power input of 3.5 kW;
- A newly designed manual needle-valve with a certain maximum diameter and full 1080 degrees (3 full turns) rotational control.
The 3.5 kW heating element heats up a 100 liter boiler charge in 2 hours. That’s a great number. Long enough for some additional Maillardization to take place, not so long that it makes a total distillation run take longer than a working day of 8 hours.
Also, the chosen power input perfectly feeds the 3 inch column. It allows for a low HETP (Height Equivalent of Theoretical Plates), so that making a pure product like vodka or neutral is perfectly achievable.
So the power setting, column diameter, and everything else work perfectly well when making pure product, but how about taste rich product, like whiskey, brandy, or rum? How about stripping and finishing those?
Stay with me, because this is where the challenge became interesting. Why? Well, because 3.5 kW energy input is actually a bit too low for ultrafast stripping. On a 3 inch diameter column, I’d rather strip at 4.5 to 5.5 kW for faster production rates. But beefing up the power would mean that customers or Craft Distillers buying the iStill 100 NextGen all of a sudden have to invest in special power plugs and probably heavy duty electrical wiring. A standard 210 volt (USA) to 230 volt (Europe) / 16 amp (Europe) to 20 amp (USA) household socket/grid would not cut it anymore. And that was a no go.
Now, for finishing, 3.5 kW isn’t ideal either. In a sort of potstill configuration, a 3 inch diameter column, while finishing, is best fed by some 2.5 kW, not 3.5 kW. More power isn’t bad, but it will create more smearing and may mean your product has to age a bit longer.
Steady state distilling in practice
The solution was found by applying the steady state design principle. In more laymen’s terms? With the iStill NextGen, if you want to make taste rich product, you can stop stripping and finishing all together. Instead, the NextGen line-up offers you a one distillation approach for more taste transfer, for better taste transfer, and for a more efficient total operation (hey, you skip one complete distillation cycle)!
Practically, this is what we did. I designed a needle-valve that at its standard opening would still create some reflux. Reflux that is sent back down the column for redistillation. In such a way that an 8 to 10% beer or wine charge results in a 60 to 65% Hearts cut. Right: the column now gives you two distillations in one go! Ideal for aging, for maximum taste transfer, and for total efficiency.
Do you want to make vodka after all? Use the Hearts cut and dilute it to 30%. Now rerun it with the needle-valve half closed and you collect at 95% instead of 60 to 65%. It’s as simple as that!
By carefully designing the iStill NextGen according to our Steady State Design Principle, we have created an afforable and easy to run 100 liter size rig. In standard setting, it will create perfect strength Hearts cuts for whiskey, rum, and brandy with the needle valve in its standard setting. It will help you create pure vodka by simply closing the needle valve a notch.
iStill 100 NextGen
Interested in the iStill 100 NextGen? Please know we are buidling the first batch of 3 units right now. More information on its specifications? Please follow the iStill Blog. We’ll post more on the iStill 100 NextGen the day after tomorrow.