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Using Steam Wands to bring Fermentations to a Boil faster
First published on Distillique's website in 2015 by GM Bosman
In an earlier article we discussed the use of jacketed boilers and the inherent problems of transferring heat from the jacket to the mash.
This jacketed type (also called Bain Marie) boilers have a jacket around it that is partially filled with water and heating elements in this water jacket to create steam to heat the full jacket. However, if you would like to get even faster "bring to boil" times, it may seem impossible.
If you increase the wattage (energy output) of the heating elements, you will create more steam in the jacket but the heat transfer to the mash will not increase. This is because the heat transfer between the water/steam jacket and the mash becomes less and less as the mash reaches boiling point and the heat transfer through the stainless steel (from the steam to the mash) is limited by the temperature difference between the steam and the mash temperatures.
You can up the heating in the jacket, but the mash will not boil faster. Only more and more steam will be created. This steam, off-course, needs to escape from the jacket to prevent the pressure in the jacket to increase (Think BIG explosion!) and is wasted energy.
The above is a problem experienced by bigger water jacketed or steam heated boilers.
A very simple solution is luckily at hand. Use a "steam wand". The steam wand will solve the heating problem and bring your mash to the boil much faster without any dangers involved to burn the mash or increase the pressures in your boiler to dangerous levels.
The excess steam from the jacket is guided through the steam wand into the pot and steam bubbles from the bottom of the steam wand, directly into the mash. (We’ll discuss the dilution a little bit later) The Steam Wand is simply a copper pipe guiding steam from the steam filled jacket directly into the mash.
The horizontal part of the steam wand contains slits at the bottom of the pipe that allows the steam to escape into the mash. As a steam bubble escapes, it immediately starts transferring heat to the mash and becomes smaller and smaller as it loses heat until it finally collapses. The more and the smaller the starting bubbles, the more heat can be transferred.
The question now arises: "But what about the steam that collapses into water in the mash?”
If steam through the steam wand is used only to bring the mash faster to a boil (for example in spirit runs), the mash volume will increase by about 3-5% (and in effect gets diluted a little).
If the steam wand is used continuously during the distilling process (such as when doing a stripping run) as well, a total amount of about 15-20% (of the original mash volume) of water is added to the boiler. This is however a small price to pay for a much improved heating solution. When considering the reduced "bring to boil" and faster stripping times, it just makes economic sense.
In practice: During Trail Runs the above steam wand system reduced the "bring to boil" time with about 55% allowing a total of 12kW heat input to the mash versus about 5.5kW without the steam wand without any real negative effects on the spirit quality.
If the slight dilution of the mash creates problems, then the solution is to use a calandria which is a closed circuit heat exchanger inserted into the mash.
However, special precaution should be taken to prevent excessive pressure build due to condensate in the calandria and it is not as effective as the steam wand (suffering again from the heat transfer limitations through the calandria walls into the mash).