Progress of conversion in a shrinking wet cylindrical wood particle pyrolyzing in a hot fluidized bed

A two-dimensional (2D) mathematical model in cylindrical coordinates has been formulated and used to predict the progress of conversion in a cylindrical wood particle undergoing pyrolysis in a fluidized bed. The transient model takes into account the heat consumed and shrinkage during drying and pyrolysis reactions in addition to anisotropy and changing thermal properties during the conversion. Predicted centre temperature has been compared with measurements found in the literature for validating the model. Calculations have been carried out for a 10 mm long and 10 mm diameter wooden cylinder in a bed of sand at 1107 K and fluidized by nitrogen. Developing profiles of temperature, solid-phase density, moisture content and degree of conversion at various stages have been presented. It is found that the conversion progresses faster and the gradients are steeper across the grains than along them. A comparison with a 1D model shows that thermal wave propagation predicted by the 2D model is faster than that of 1D.