[Stoves] Distillation and oxidation Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh TLUD )

[Crispin Pemberton-Pigott]

Dear Tom

What Hirendra described in the quote Paul and I traded is the updraft version of:

“The visible migration of the flame front was heating wood pellets and generating pyrolysis gases as it advanced. In that case suction drew the gases down through the unreacted fuel.”

It is exactly like that, but upwards. I heard there was steam applied sometimes because Anton Soedjarwo at YDD uses steam in his version of that same process, with the difference that he has a fluidised ceramic sand bed at the bottom which converts all the carbon into gases. He developed that with the Japanese for IC engines powered by empty palm bunches.

Regards
Crispin


Since we’re digging out textbooks I go back to my text from graduate school, “The Chemical Technology of Wood” by Hermann Wenzl, translated from German in 1970. Wenzl credits his mentor, Carl Gustav Schwalbe (1971-1938), who established the Chair for Cellulose Chemistry at the Technical University in Darmstadt in 1906 and who headed Wood Research at the Forestry School in Eberswalde until he retired in 1933.  After describing acid hydrolysis Wenzl describes pyrolysis as “Further Destructive Processing of Wood” along with other processes in which the fiber structure of wood is completely destroyed. At the time (1938) pyrolysis was also known as carbonization or dry distillation. He included pressure oxidation and “hydrogenolysis” as destructive processes.

Hydrogen formed in a downdraft gasifier is probably consumed in the oxidation that is driving the gasification by heating the biomass. A typical downdraft gasifier will make producer gas with ~20% H2 and ~20% CO. Increase the air and you get 10% H2 and 20% CO. Are we making less H2 or consuming more of it?

Tom Reed demonstrated his “flaming pyrolysis” in a gold plated transparent gasifier in his lab in 1982. At the time he was developing an oxygen blown down draft gasifier to make synthesis gas. The visible migration of the flame front was heating wood pellets and generating pyrolysis gases as it advanced. In that case suction drew the gases down through the unreacted fuel. “Stratified Downdraft” and “Top Lit Updraft” came later.

Tom
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