The pyrolysis of the three main components of most biomass types have been reviewed above. It could therefore be expected that the pyrolysis of wood would exhibit similar characteristics to the pyrolysis of its components. From TGA DTA and DSC work, rt has been concluded that the mechanism of wood pyrolysis is a linear combination of these three components (1, 9, 13, 15, 18, 20, 40, 41,42, 43, 44, 45,46). The focus of this section is fast/flash pyrolysis of wood which has been accounted for in three major proposed reaction schemes.

1. Fast Pyrolysis of Biomass Workshop, October 1980

The first comprehensive reaction scheme to account for the fast/flash pyrolysis of wood was proposed by Diebold (47). The reaction scheme was the general consensus of pyrolysis specialists attending a workshop on the Fast Pyrolysis of

Biomass, at the Solar Energy Research Institute (now National Renewable Energy Laboratory, NREL), in October 1980. This is depicted in Figure 2.3.

This was the first model to take into account the influence of heating rate, temperature and pressure with regards to biomass pyrolysis. The focus of the model is the formation of hydrocarbons, СО, C02, H2 and H2O as the interest at the time was in the production of olefins. Diebold Proposed Modified Reaction Scheme

Diebold then proposed a more simple reaction scheme in that the biomass initially decomposed to a viscous primary precursor with an elemental structure similar to wood (48). This is shown in Figure 2.4.

Figure 2.4 Diebold Modified Reaction Scheme 1985 (48)