Radiative pyrolysis of single moist wood particles

Radiative pyrolysis of thermally thick beech wood has been investigated through a comparison between dry and moist [11% dry basis (db)] particles, for heat fluxes in the range 27.5-80 kW/ mt. The initial moisture content has also been varied from 0 to 50% (db) for two radiative fluxes, 27.5 and 49 kW/m(2), corresponding to slow and fast external heat-transfer rates, as steady surface temperatures are about 625 and 800 K, respectively. For very slow heating, moisture evaporation precedes wood pyrolysis. As the external heating conditions are made more severe and/or the initial moisture content is increased, the two processes take place simultaneously, associated with the propagation of separate fronts along the particle radius. Spatial gradients also increase, while apparent weight loss kinetics from a single-peak rate turn into a two-peak rate. The conversion times increase almost linearly with the initial moisture content, but differences in primary product (char, gas, and liquids) yields and gas composition are negligible.