THE MANUFACTURING PROCESS
It is certain that ancient races were acquainted not only with the production of
charcoal but also with the methods of recovering various by-products from this process.
Examples are fluid wood tar and pyroligneous acid which were used by the Egyptians for
embalming their dead, as recorded in the works of ancient writers for example "Pliny"
in his "Historia Naturalis Lib 11, De Pice".
The process was originally carried out in simple open-air pits. Subsequently these pits
were replaced by more efficient Heaps. These primitive methods enabled wood to be distilled
purely for the production of charcoal. Subsequently wood was distilled in metal kilns and
retorts. In the modern day, the more highly volatile condensable and non condensable
distillation products are more easily produced from coal distillation processes;
wood is therefore almost exclusively carbonised for the production of charcoal.
In a simple kiln, a portion of the timber charge is used to create the heat which gives rise
to the carbonisation process.
The distillation of wood in such apparatus basically resolves itself into 4 different stages:
Once the charcoal has cooled in the kilns, these are opened and the charcoal is
transported to a holding area where it is allowed to weather for not less than 72 hours.
- Evaporation of the moisture present in the wood takes place as the initial phase up to an
average temperature of 170 degree Celsius. During this period scarcely any gas is produced.
- As the fire builds up inside the kiln, the temperature rises and at approximately 280
degree centigrade the exothermic reaction begins to take place. Gas consisting almost
entirely of carbon monoxide and dioxide is evolved and a certain amount of acetic acid
is formed together with small quantities of wood-naphtha and tar.
- The exothermic reaction then continues during which concentration of carbon in the
charcoal takes place. Large quantities of hydro-carbons, acetic acid and wood-naphtha
and tar are produced while the temperatures rise to 380 to 400 degree Celsius.
- No further oxygen is then allowed into the kilns and the cooling down period commences.
Under these conditions hydro-carbons are absorbed by the charcoal.
After weathering, the charcoal is then removed to a Screening & Packing Plant where
the dust and small particles are removed together with any uncarbonized pieces of wood
or foreign particles. The screened product is then prepared
for distribution to AFCHAR's customers.
This page maintained by Niels Dahnke.
Last updated on 17 September 1997.
Copyright © 1997 by Niels Dahnke.