I think you may be near the correct answer for a mixture only of water and methanol. The boiling point of mixtures can be calculated, but are easier to find experimentally. However, in recovering methanol from biodiesel byproduct we have a much more complex mixture. Any water in the mix is either tied up in soap or, at the very least, heavy in dissolved catalyst. Either will make the water much more difficult to boil. I haven't taken my rig up to high enough temperature to after methanol recovery to recover any water, so I can't be sure at what temperature and pressure water recovery would begin, but suspect it would be at a very high temp or low pressure.
Dale --- In [EMAIL PROTECTED], Keith Addison <[EMAIL PROTECTED]> wrote: > > ><snip> > > Hi Dale > > Thanks, good info. > > >I don't think water can be > >recovered from the byproduct at anywhere near the boiling point of > >methanol. > > Now let's see if I can get this right. If it's a mixture of methanol > and water that's being boiled, the boiling point of the mixture will > be somewhere between the two boiling points, depending on the > proportion of the mix. Of course vapours come off before boiling > point is reached, but the methanol component won't boil off at the > boiling point of pure methanol (64.7 deg C), while the water > component remains unboiled until the temperature reaches 100 deg C. > If you evaporate a liquid mixture, the vapour has a higher proportion > of the more volatile components than the liquid it evaporated from. > Alcohol is more volatile than water (it takes less energy to vaporise > alcohol than to vaporise water). So when you boil a mix of the two, > the vapour contains more alcohol - not because the alcohol component > of the mix is boiling first, but because the alcohol is more > volatile. So the proportion of alcohol in the boiling liquid steadily > goes down, and the boiling point of the mixture steadily goes up. In > a 50-50 mix the boiling point will start off being halfway between > the boiling points of the two components - more alcohol lowers the > boiling point, more water raises it. If you boil a mix of methanol > and water, you'll get vapours of both. > > (How did I do, O Silent One?) > > If I screwed up, Dale, I'll no doubt be hearing about it and will > post a correction. > > Thanks again. > > Keith Addison > Journey to Forever > Handmade Projects > Tokyo > http://journeytoforever.org/ Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Please do NOT send "unsubscribe" messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
