Prevent over cooling, save power and increase ABV output

[Anavrin]

Hi Guys

I've just been researching building and controlling a dephlegmator, I came across a page on stilldragon.org where a guy was asking about temperature monitoring the output water, here's the link if anyone's interestested

https://www.stilldragon.org/discussion/ ... monitoring

Interestingly there's some school of thought that the output temp of the water exiting your main reflux condensor should be in the range of 82°c - 85°c to prevent over cooling of the distillate, if you think about it, even if you want 100% reflux it's important to use as little cooling water flow as possible, too much and the distilate will travel further down your packed column before heating up enough again to boiling point, this can render a portion of the top section of your packed column useless, reducing ABV output and you may be un knowingly over compensating with additional power.

I've always run my cooling through my reflux coil on full during a spirit run and never given it a second thought, despite my best efforts I've never reached above 94%

Maybe this is the cause? Do any of you guys using an LM or VM still (not a T500) monitor the temp of you cooling water output from your main condenser?

[YHB]

Yes, On my Bok I monitor the output from my reflux coil and have it as hot as I can without any vapour making it to the top of the coil.

The reflux ratio is dictated by how much I take off with the needle valve, unlike the CM systems where the one condenser dictates the temperature of the distillate and the reflux ratio.

I have in my minds eye that in a BOK, the distillate being retained in the slant plates for a short while and being reheated /re-boiled by the raising vapours before they head back down the column.

[Anavrin]

I kind of guessed if anyone was already doing this it would be you Brian, being the font of all knowledge boka and all

Just out of intrest how slow can you run your cooling water and still get full reflux? what sort of temp do you expect your cooling water to be on the output of your coil?

Seems I learn something new every day with this hobby, I wanted to add a CM coil below my boka plates to help isolate heads but I guess by controlling my cooling properly I will be better able to compress the heads, I'll try this on my next spirit run then add my CM coil for the next one.

[YHB]

Just out of intrest how slow can you run your cooling water and still get full reflux? what sort of temp do you expect your cooling water to be on the output of your coil?

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"Very slowly", and the temperature of the cooling water is "very hot", hotter than you would want to have a shower in. Sorry cannot be more technical than that but I have never measured it.

If I had measured it I think it would be a red herring. My coil is a lot bigger than it needs to be for a reflux coil, when operating at refluxing power I believe that the first few coils take care of the condensation, after that the water stays in the coil for a lot longer than it needs to, getting hotter as time progresses. So I believe the output temperature of the coil is different for each size of coil and still. Unless you get something like a T500 which are all identical and therefore temperatures can be quoted.

I am also looking to add a CM coil below the slant plates to service the bubbler plates that I am installing, CM seems the method of choice for a plated still. I don't know why but at least I will have all options to find out.

[Capt-Cudellez]

Just to echo what YHB said, there really is no need to measure the cooling output on a VM or LM still, you just want it to be very hot. (I cant get the output hot when running on low power for heads removal, so don't worry too much about that, but get it set for hearts when you ramp the power up)

You may need to consider the material you are using for your cooling hoses - I use reinforced airline, if I was using thin walled PVC tubing it would soften and potentially collapse or kink, cutting off the cooling - easily done when running just a trickle of cooling.