Re: Extraction of ethanol using butane?
- From: Fred Kasner <fkasner@xxxxxxxxxxxxx>
- Date: Sun, 08 Apr 2007 14:19:43 -0500
Gregory Bloom wrote:
It seems one of the biggest energy-sinks in ethanol production is the
heat required for distillation. This got me wondering whether it
would be possible to purify ethanol by chemical separation using a
hydrophobic solvent that has a low latent heat of vaporization, like
butane. Could we simply add a layer of liquid butane, under pressure,
over a fermented 15% EtOH wash, drain the wash from the bottom of our
big 'sep funnel', then vacuum off the butane to leave ethanol? The
latent heat of vaporization of butane is 395.42 kJ/kg, as compared
with 2260 kJ/kg for water. That should make the separation over 5
times more energy-efficient than distillation. Of course, only a
portion of the ethanol will dissolve in the butane, but so long as
this is more than 20% of the available ethanol, it still seems like a
favorable extraction. And, as a small bonus, it probably wouldn't
even kill the yeast culture, making it possible to replace the
nutrients used in producing the ethanol that was extracted, and keep
on fermenting and extracting more or less continuously.
This seems like a pretty a obvious idea. The fact that nobody's doing
it suggests it wouldn't actually work. So what prevents it from
working?
What about the considerable energy needed to liquefy the butane after each use to prepare it for another extaction?
FK
.
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- Extraction of ethanol using butane?
- From: Gregory Bloom
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