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:

  1. 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.
  2. 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.
  3. 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.
  4. 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.
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.

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.


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