If you spray the bio into the top of a sealed IBC (1000litre tote); recirculating it for hours; add a small positive air flow from a fan or aquariom pump; add a condensor; then could you recover the meth from evaporation alone without heat?

Since you posted this in two places, I will ass-u-me that nobody answered you on in other topic.

I will go out on a limb and say...hmmm...yes. BUT, it will probably be ungodly slow.

AND, I think the condenser would have to be colder than it otherwise would have to be...or maybe not.

You still (excuse unintentional pun) have got to have some heat from somewhere, even if it is only from the surroundings at ambient temperature. The methanol has a latent heat of evaporation (energy required to turn 1 gram of liquid into 1 gram of vapour at the same temperature) and this still has to be supplied. If you don't put energy in by heating then the net result will be to refrigerate your biodiesel until the point that the heat from the surroundings balances the energy required to vapourise the methanol.

Yes, I think it would work, and yes, I agree it would be fairly slow. And yes, the condenser would need a way to dump the latent heat of condensation somehow.

All the best

Pete

If there is an air stream with a little methanol in it, as would be the case in "evaporation", you would need a very cold condenser - perhaps dry ice might do it.

However there is an easier way: have no air stream. Then all you need is a temperature difference and the methanol will migrate from the warmer to the cooler region. You still need something to create the temp difference. The sun can help.

Have a search for solar stills. The sun shines through glass (greenhouse effect) and warms the liquid. The glass is not warmed by the sun as much as it is transparent to light. The glass is on a slope and the water collects there and runs down to a collection channel. It should work for methanol.

Hi Ant,

With air as the carrier, the condenser will need to be cooled to below the dewpoint of the methanol in air.

The dewpoint gets lower as the concentration gets lower, so you will carry off much of the methanol in the airstream at lower vapour concentrations.

In addition, unless you are using dry air, you will also condense water out of the feed air, which will degrade purity.

Hope that helps.

Hello Ant

Though I've yet to recovery any methanol being a newbie, according to some other threads there might be a concern with oxidation. I am in-experienced but your method would seem to put the your BD in contact with a lot of air for a long time. I'm not really sure if my thoughts are even valid but I would like to know what everybody else thinks. How fast does oxidation occur? Some spray BD and some bubble. Which is best for minimal oxidation?

Food for thought?? Anyone??

ALay

quote:

Originally posted by ALAY:

...
How fast does oxidation occur?
...

ALay

In real life, dunno. In my Dr Pepper batches, one from new rape seed oil and one from a 25/75 mix of used palm oil and used light fryer oil, both exhibit a tendency to absorb the air left in the bottle over a period of a week or two - I assume the oxygen is being absorbed and the nitrogen left behind. The relative volumes of BD to air are roughly one to one. One day I might try to test that hypothesis.

All the best

Pete