Hi Bruce, Those substances you mention are not--for the most part--"in" the wood in their final form. Destructive distillation implies the cracking of complex molecules into simpler substances. It's possible to do with pyrolysis alone, but most industrial processes would also employ a catalyst for better yields of a specific chemical.
Methanol, acetic acid and acetone do not form azeotropes with water or each other so a simple distillation column and reboiler can separate them according to boiling point in acetic acid, water, methanol, acetone downward order. Best, Mark -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bruce Jackson Sent: Sunday, December 19, 2010 9:55 AM To: Discussion of biomass pyrolysis and gasification Subject: [Gasification] RH brings up another question.... As fascinating as the relative humidity of the exhaust is, and the idea of drying wood with the exhaust (which is precisely what has to happen here!), it brings out another nagging question... If we were to be drying wood with superheated gases (steam, nitrogen, CO, etc.) what is the order of march for distructive distillation. I have read and reread my industrial chemistry books and they tell me that for each ton of hard wood, I'd get about 20 gallons of methanol and 20 gallons of acetone, some acetic acid, water, methane, and some other stuff I don't remember. What I can't remember from the books is the order of march. So who gets driven off first? And why? Here is why I am confused...wet wood has volatiles in the bark that will burn first, these heat the body wood hot enough to cause the steam to hiss out of butt ends. So if we tossed that example out, and simply heated wood at a gradual rate, would the distillation order be simply the boiling point of each molecule? By rights, then the methane should come out first, but I never see flames shooting out of the butt ends (or the worm hole pores) until the water is gone. What is going on? BPJ _______________________________________________ The Gasification list has moved to [email protected] - please update your email contacts to reflect the change. Please visit http://info.bioenergylists.org for more news on the list move. Thank you, Gasification Administrator _______________________________________________ The Gasification list has moved to [email protected] - please update your email contacts to reflect the change. Please visit http://info.bioenergylists.org for more news on the list move. Thank you, Gasification Administrator
