Visualization and characterization of thermo-physical behaviour of wood during devolatilization in a hot fluidized bed using X-ray radiography technique

It is found that the “true” CFT inferred from DXR technique is 12% and 26% lower than that obtained by the Flame Extinction Time (FET) technique for a 10 and 15 mm particle, respectively. The terminal mean longitudinal, transverse and volumetric shrinkage are found to be in the range of 12-17%, 22-23% and 44-47%, respectively for all the particle sizes studied. The terminal volumetric shrinkage falls well within the range of 40-65% reported in the published literature. In contrast to the popular assumption in the devolatilization models, the variation of shrinkage with conversion is found to be non-linear in along-the-grain direction. From the present study it is verified/established experimentally (visually) for the first time the difference in rate of propagation of char front across and along the grain direction of the wood particle. The predictions of the 3-D model on progress of conversion compare well with the experimental findings of DXR technique. This technique can also be applied to other solid fuels.