Sawdust is carbonised in two round kilns via a downdraft initially created
via a small wood fire lit in the bottom of the chimney. As pyrolysis
proceeds over the perforated sheet metal bottoms of the kilns (a galvanized
iron water tank cut in two), additional sawdust is added to cover the
charring material. The white smoke (volatile gasses) are drawn down through
the bottom of the kilns and burnt in the base of the chimney with the aid
of the wood fire and additional

secondary (fresh) air injected  via two
2-inch pipes. This creates a strong flue draft through the system allowing
rapid conversion of sawdust into charcoal.

The flaring gasses burn with tremendous heat up the entire length of the
chimney. This prototype unit is capable of carbonising over 500 kg of
air-dry sawdust within 8 hours at a conversion of 23%. Further work on
increasing the size and throughput of this design continues.

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Elsen L. Karstad , P.O. Box 24371 Nairobi Kenya
elk@net2000ke.com     tel/fax (+ 254 2) 884437