For stripping you should feed the mash to the top to use the column at it's full effect. With well balanced stripper high 80s or even 90s ABV is possible while leaving most of the tails to the boiler. I don't know if that's enough for fuel use though. If you want to build something continuous I'd suggest keeping it simple and adding those efficiency improving heat exchangers once you have the rig up and working.
--- In Distillers@yahoogroups.com, "Stillton" <stillton@...> wrote:
> continuous distillation is probably the concept you are looking for. you should probably start with getting one of these concepts running before you try them together.
> in continuous distillation you should have a small reboiler in the bottom of the column and feed the mash half way up (well, as a general rule, but it will depend on your setup, and what you are trying to achieve).
> to give you a basic idea.. put a 1500W small boiler under a 2 meter (7 feet) 2" LM column with packing. feed mash into it halfway up. pull of "water" from the boiler at 98-99C. use the waste water to preheat the mash for better efficiency.
> you now have a continuous stripper that gets rid of most water and tails.
> to achieve azeotropic ethanol, you will (probably) need a second column that draws tails from the bottom, and heads and ethanol in the top. then a third column that gives ethanol in the bottom and heads in the top.
> to get this working in balance is not a simple task but can save you some energy if done correctly. (this is how the "big boys" vodka factories produce there ethanol).
> but since you are trying to get rid of the water, im guessing you might be trying to produce fuel, and not drinking alcohol?
> in this case you could use the first column as a stripper, and apply vacuum to the second column, your car will run fine on heads and ethanol, even if it doesn't taste well.