Re: [Distillers] Reflux equilibrium
- David, Pete from Brewers barn here. We have found that an element up to 1000w is sufficient for volumes up to 20litres,( for the distillation process), however we once put a 1380w element into a 20litre brew,(the 1380w element was designed for a 25 litre brew), and found it to be toostrong , causing surges in the pot. This lead to the vapours lifting the lid and "puffing".
Hope that these details are of help.
kind regards Pete at Brewers Barn
DAVID REID wrote:
Tom, You ask: is there a formula for how long it should take to achieve equililbrium. Basically no as far as I am aware as the variables are too many especially as regards outside ambient temperature and inside the column conditions. With small stills such as we are using you should ideally leave it at least 2 hours so not only are they separated in the column but to a reasonable degree in the boiler. This last aspect is almost impossible to achieve with a lot of stills and is one of the things that separate the better stills from the majority. The secret here is to bring the wash up to temperature and then to have very even constant temperature so the true separations occur. The story here is to leave the controls alone (NOT TO KEEP CONSTANTLY FIDDLING WITH THE SYSTEM AND TO BE CONSTANTLY TWEAKING THE CONTROLS and consequently stuffing up the separations that have occurred and are occurring). A booster element here to bring the wash up to temperature (77 to 79 degrees, max:80) helps considerably to shorten the initial warmup time. Your main element can then be more along the lines of what it should be; from 650 to 750w for loads from say 15 to 25 litres (and up to 30 lites), and 1000 to 1200w for up to 50 litres. I personally disregard this and dont equilibriate for this amount of time (largely because of energy costs and this is one aspect where I am a bit lasy and dont make the time) and use a slightly larger element which is where I fall down but know if I came back to these figures that I would see an improvement. Once you bring the wash up to temperature you need to get to get the input temperature just right. Somewhere between a gentle simmer and a rolling boil. I find it is just past a gentle simmer rather than closer to a rolling boil. Some people classify these two as the same but I see them as quite different. This is where a sightglass helps tremendously. If you equilibriate for the proper amount of time you will find that almost all the ethanol comes off in one hit with virtually no other components. The story here is to establish equilibrium and then first bleed your methanol off. This may suprisingly take 2 or 3 minor bleeds as if you open the needle valve too much and/or leave it open for too long you begin too mix the ethanol in with it and to also start stuffing your separations up. Once this is done you then need to equilibriate again and let the system settle down so the separations are correct. Once this is correct and you have proper separation you can then commence takeoff. The secret here is to get your takeoff ratio correct. Too little and you are wasting energy and time; too much and you quickly stuff your separations up and mix other components in. Most of the time it is far too easy to over correct than to under correct. Ninety % of distillation problems are a result of this rather than other problems. As they say there is no substitute for experience. While virtually anyone can learn to distill quite quickly and learn the basics in no time at all only experience will get it perfect every time.B.r., David