Pyrolysis is thermal decomposition occurring in the absence of oxygen. Lower process temperatures and longer vapour residence times favour the production of charcoal. High temperatures and longer residence times increase biomass conversion to gas, and moderate temperatures and short vapour residence time are optimum for producing liquids. Three products are always produced, but the proportions can be varied over a wide range by adjustment of the process parameters. Table 1 and Fig. 2 indicate the product distribution obtained from different modes of pyrolysis, showing the considerable flexibility achievable by changing process conditions. Fast pyrolysis for liquids production is currently of particular interest as the liquid can be stored and transported, and used for energy, chemicals or as an energy carrier
partial combustion of wood. A small fire at the bottom provided the required
heat for carbonization. The fire essentially stayed in the well-insulated closed
chamber. Carbonization allows adequate time for the condensable vapor to be
converted into char and noncondensable gases.