Literature:
When the wood is dry and heated to around
280°C, it begins to
spontaneously break down to produce charcoal plus water vapor, methanol,
acetic
acid and more complex chemicals, chiefly in the form of tars and
non-condensable gas consisting mainly of hydrogen, carbon monoxide and
carbon
dioxide. Air is admitted to the carbonizing kiln or pit to allow some
wood to
be burned and the nitrogen from this air will also be present in the
gas. The
oxygen of the air is used up in burning part of the wood
charged. The spontaneous breakdown or carbonization of
the wood above a temperature of 280°C liberates energy and hence this
reaction
is said to be exothermic. This process of spontaneous breakdown
or
carbonization continues until only the carbonized residue called
charcoal
remains. Unless further external heat is provided, the process stops and
the
temperature reaches a maximum of about 400°C.
ADAM:
Comment: exothermic is still a kind of mystery for me, because I often realized that If the wood chamber of a retort already heats up to ~300°C still a lot of heat Is needed from outside to push gasification.
I am really tempted to make a laboratory experiment.
Place a piece of oven dry wood in a small container, and place it in in
electric oven by 500°C., record the temperature inside the small
container
wood, ideally the temperature should jump up more quickly above 280°C,
because
of additional exothermic heat supplied from inside the wood-charcoal
piece?
But I dont recall to have seen such a jump in a plotted
graph? Also anyone has an idea about thatamount of
that expected exothermic heat??
THANKS Chris
_______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected]
to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://stoves.bioenergylists.org/
