Modeling of the devolatilization of nonspherical wet pine wood particles in fluidized beds

The release of volatiles of pine wood particles was analyzed by means of continuous measurements of the CO2 and O-2 concentrations obtained after the complete combustion of the volatiles and from flame extinction times. A relatively simple mathematical model was used to predict the O-2 consumed, as a function of time, during the devolatilization and further volatiles combustion of wood. chips in fluidized beds. In this model, the drying and pyrolysis of wood particles is considered as a coupled process controlled by the kinetics of devolatilization as well as heat transfer to and through the particles. A distributed activation energy model is adopted for the kinetics of devolatilization of the wood particles. The wood chips are characterized by an equivalent particle diameter and a shape factor and transformed into spherical shape. The model was in satisfactory agreement with experimental data over a wide range of operating conditions, particle sizes and shapes, and particle moisture contents of practical importance for wood combustion in fluidized beds.