The Furnace
The first step in carbonization in the oven, the wood is dried at 100 ° C or less up to a zero moisture content is increased then the temperature of the oven-dried wood to about 280 ° C. The energy for these stages comes from the partial combustion of wood loaded in the oven or in the pit, and is a reaction that absorbs energy or endotherms.

When the wood is dried and heated to about 280 ° C, spontaneously starts to split, producing more coal steam, mornings, acetic acid and more complex chemical compounds, primarily in the form of tar and non-condensable gases, which consist primarily hydrogen, carbon monoxide and carbon dioxide. Allow air to enter into the oven or pit so that part of charring wood burns, nitrogen and this air is also present in the gas. The oxygen from the air will be spent in the burning of wood, above the temperature of 280 ° C. releases energy, so it is said that this reaction is exothermic.

This process of splitting spontaneous or charring, continues until it is only the charred residue called charcoal. Unless otherwise provide additional external heat, the process is stopped and the temperature reaches a maximum of approximately 400 ° C. However, this coal still contains significant amounts of tar waste, along with the ashes of the original wood.

The ash content in coal is about 30% by weight, and the balance is fixed carbon, about 67-70%. A further warming increases carbon fixed by removing decomposing and even more tars. A temperature of 500 ° C gives a typical fixed carbon content of about 85% and volatile matter content of about 10%. At this temperature, the performance of coal is about 33% of the weight of the charred oven-dried wood, not counting the wood has been burned to carbonize the remainder. Therefore, the theoretical performance of charcoal varies with the temperature charring, due to changing content of material volatile alquitranado (24, 26, 31).

Low temperatures carbonizaci6n give higher yields in charcoal, but that is of poor quality, which is corrosive, containing tar acids, and not a flame burning with clean smokeless. A good commercial charcoal should contain carbon fixed by about 75% which requires a final temperature of carbonizaci6n of around 500 ° C.