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Decreasing the Temperature of the Condenser Water
Hey,
It is widely accepted that distillate should be collected straight off the condenser at 15-20°C (60-70°F). My problem is that the water coming out my tap are usually around 30°C (85°F), so there is no way I can bring the distillate down to the desired temperature.
What is the best (and least expensive) method of bringing the water temperature down before it reaches the condenser? My setup includes two alembic stills: 250L and 1,000L.
Thanks!
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11 Replies
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You need a chiller. You should contact Mike at MG Thermal Consulting:
Contact: Mike Gronski, Director (info@mgthermalconsultingco.com)
Office: 770-995-4066
Cell: 678-773-2794
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I collect at 25-30c everyday all day for years. Why is it “widely” accepted otherwise? Never seemed to be a problem for me this far. (I’m in the tropics so all my processes are at elevated temps)
If my ambient temps will warm the distillate above 20c why would I cool it during distillation if I wasn’t having product condensing problems?
the only reason I could see for this would be for gauging the spirits. To manage I just use temperature corrections most of the time.
Someone please educate me! Why is it widely accepted to collect at 15-20c? I’m not trying to be a dick. I have not heard of this before but I’m largely self educated in distilling.
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I agree. I think that this is misconstrued because tables are at 20 deg C
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The principal reason to keep the distillate temperature as low as practical (is the flash point of ethanol, and therefore the fire risk, try to keep the flash point as low as possible. The higher the temperature of a spirit, the more ethanol vapours that are liberated. Distilleries for decades saw 20C as the safe point. It has nothing to do with measurement temperatures, and virtually all measurements have to temperature corrected.
Generally I have not seen 30C as an issue, providing good handling and fire control practises are observed. In locations with higher ambient temperatures like you describe, usually have higher humidity. As the humidity goes up, the flash point goes down.
To your specific question.
Nothing can reduce the distillate temperature below the condenser water inlet temperature, fact. So you need to reduce the condenser water temperature. As suggested you need some sort of chiller, compressor based units are not cheap to purchase or own, but are highly effective. Depending on your average humidity, a simple falling water cooling tower will give you the 5-9C drop you need. A lot of smaller distilleries such as yours, use ice banks, a cheap option. 100kg of ice will chill 900L of 30C water (total 1000L) to 19C. If your final condenser needs 200L/Hr then you have 5 hours before extra ice is needed.
Remember you just need to pull down the temperature of the higher proof distillate to a level that presents an acceptable fire risk.
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You might want to think about using a dry chiller for you cooling problem. Use it in a closed loop, then maybe a chiller in another loop if you need it. Very easy problem to solve.
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Wow, Thanks for the thorough reply! In the IBD distillation studies they note 20C as the desired distillate output temp, but don’t explain why. I assumed it is because valuable congeners might evaporate if the temp is too high, but just may be because of safety concerns (like you explain). In the cognac tradition they also talk about optimal distillate temperature in terms of spirit profile outcome. See for example this tech note from the Germain Robin distillery:
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Brandy production, as above, talks a bunch about condenser temps effecting flavors, etc. I’ve never been to your place, but at least one rum distillery I have seen has a 2 stage condenser with water in the upper (1st contact with vapor) half and a mechanically-chilled section below for finishing the job ensuring no vapor loss on the hot ambient days.
If what you’re doing now works though, why worry? Not meeting flavor profile? I’m curious now
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85F city water- Do you live in AZ or Desert?
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The tropics I understand Fiji.
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OZ,
Using ice is a stop gap- cost of making ice (kw) is double that of making 55F water for cooling- a chiller is the way to go. Try a lease- monthly payment would pay for chiller in long run- a year or two.
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I’ve seen cognac producers altering their condenser temperature to change the distillate, specifically using a higher condensing temperature when dealing with wine that has elevated levels of VA to allow some of those components to offgas/volatilize back out of the spirit more easily. Similarly, I’ve experienced that a difference of 60 vs 80 F spirit out temp very much changes the aroma profile of gin, with the hotter spirit having less floral and fruit notes. There are quite a few scotch malt distilleries which have a 2nd condenser or ‘sub-cooler’, and I imagine its common in rum distilleries. It might be useful for hotter incoming water temps but the systems I’ve seen in Scotland were being used to get hotter process water out. Glenallachie was using a sub-cooler to alter the condensation point within the condenser to change the amount of copper contact the spirit was reaching, which is a very interesting concept.
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