freezing causes the yeast's cell wall to rupture,killing
them and therefore stopping further ethanol production.
regards,roger
> The relationship of pressure to yeast viability is an unknown to me but if
> the liquid column is deep enough that should establish a viability zone and
> a piece of filter (plastic or plasticized paper?) could keep all the
> yeasties happy below that barrier. As to vapor pressure I think you are
> asking what it boils at.
> Perhaps you can find that on the web or in the library.
>
> You will probably use less energy purifying by freezing rather than
> vaporizing
> The depression in degrees C for ethanol/water is
> % ethanol depression degrees C
> 5 2.09
> 10 4.47
> 15 7.36
> 20 10.92
> 30 20.47
> 40 29.26
> 50 37.67
> 60 44.93
> 68 49.52
>
> I think freezing H2O only uses 1/3 as much energy as evaporating. Better
> check that as my memory isn't what it used to be.
>
> Another way, since it can be slow, is a cold trap in a sealed system. The
> alcohol will transport faster than the water.
> Vacuum systems where you pressurize the output of the pump in a cold trap
> have the product going through a pump and contamination is a given. If not
> for human consumption I suppose it doesn't matter but the energy
> requirements are higher than just a trap using ambient heat to transport the
> product. It doesn't have to boil and the cold trap condenser heat can be put
> back in the source vessel if using a refrigeration system.
>
> If your tank is at 125 F I would think 75F would get condensate at a good
> enough rate to keep concentration below yeast toxicity.
> Could get 75F probably by running household water through a tank and then to
> house. Most water is 55F or so I would think. I assume you use the sun to
> heat your tank. Slowest process of all but uses the least energy.
>
> Just some meandering round Robin Hood's barn but I think there is a seed or
> two in there.
>
> Kirk
>
>
> -----Original Message-----
> From: motie_d [mailto:[EMAIL PROTECTED]
> Sent: Friday, February 08, 2002 3:34 PM
> To: biofuel@yahoogroups.com
> Subject: [biofuel] Re: ethanol distillation
>
>
> --- In [EMAIL PROTECTED], "kirk" <[EMAIL PROTECTED]> wrote:
> > I think yeast croak or really slow down at 14% or higher.(14%
> =28proof)
> >
> That is also my understanding. The alcohol starts to kill the Yeast
> above 10%, and they are nearly all dead by 14%.
> On the temp side, 140F kills them off.
> That brings me back to the basis of my question. If I heat my
> fermentation tanks to (?)125F, so the yeast are still alive, how much
> vacuum will I need to apply to the tank, to start removing some of
> the Ethanol to keep the level below 10%?
> How much vacuum to do the same task at 100F? I would like to keep the
> Yeast alive and actively producing, without having to heat the
> massive quantities of water to do a traditional distillation.
>
> I'm trying to look ahead, at the whole process, and solve as many
> potential problems as I can see, before I start investing meager
> assets to it. I can overcome the heating problem rather economically.
> It's disposing of the heat after I've used it, that will be my
> shortcoming. I am trying to remove the heat disposal problem, by
> simply not putting the heat in to start with.
> I welcome any thoughts and commentary on my approach.
>
> Motie
>
>
>
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