We had a successful Drinktec 2022 in Munich. Hundreds of brewers and distillers visited our booth, asked questions, and expressed their interest in our disruptive technology. But what did they ask? What were the questions on their mind, as they saw the iStills? In a series of posts called “Questions & Answers” we will summarize the questions that were asked most as well as our answers.
Why are your boilers square instead of round?
Depending on the type of spirit you produce, agitation is needed, so that the boiler contents are well-mixed. In a round boiler the boiler contents will start to move with the agitator system. As the speed differential between the agitator and the boiler contents drops, so does the actual mixing energy that is applied. Therefore, mixing in a round boiler is not very effective and the goal of optimal dispersal of grains or herbs or grapes is not achieved.
As a result, still manufacturers, that do add agitators to round boilers, often have to resort to over-mixing the boiler contents. The now very fast turning agitator throws boiler contents into the gas bed above the liquid bath. This disruption of the gas bed, from which the riser or column harvests its gasses, leads to fluctuations in vapor speeds in that riser or column, hampering flavor consistency and cuts management. Boiler and agitator longevity will be comprised too, as both are over-worked in order to create a higher degree of mixing.
Also, as the boiler contents start to move with the agitator – in a round boiler – a vortex is created. The vortex sucks gasses downwards, competing with the riser or column. This interferes with the riser or column doing its work properly. As with over-agitating the boiler contents, a vortex hampers production speed as well as flavor consistency and cuts management. What essentially happens, in both cases, is that micro burst of over- and under-pressure influence the vapor speeds inside the distillation system, resulting in unwanted smearing of heads and tails flavors into hearts.
The vortex has a secondary negative effect. As the vortex reaches downwards, more boiler contents are pushed upwards, via the sides of the boiler, limiting the fill-grade of that boiler. Especially in combination with over-mixing, this can result in a big difference in gross vs. net boiler capacity. In a round boiler with a gross content of 650 liters, the maximum net filling will be 350 to 400 liters only. The choice for a round boiler severely limits your production capacity, as you have to do more yet smaller runs.
How a square boiler with flush corners helps? Well, first of all the boiler contents cannot start to spin with the agitator. The moment the wash start to move with the agitator, the corners – that are further away – generate a counter rotational movement, keeping the boiler contents in place and thus maximizing the speed differential between agitator and wash. As a result all the energy put in by the agitator translates into actual mixing and perfect particle distribution.
Since no vortex is created – in a flush-square boiler, that is – and no over-mixing needs to take place, the gas bed above the boiler contents is very stable. The riser and column can do their work under optimal conditions, which results in higher production rates, better quality spirits, and recipes that are reproducible from one run to another.
Finally, our 630 liter gross capacity iStill 500 has a net fill rate of 500 liters. That’s about 30% more than an equally sized round boiler. The benefit? You get more still for your buck. You can process bigger batches. Your yield – and therefore your income – is significantly increased.
What reactions did we get, when answering the question of why we have flush-square boilers? The reactions ranged from “that makes total sense” to people being flabbergasted.
At your service!
The iStill Team
Square boilers matter …