The mass loss and temperature history of highly wet biomass and organic waste particles have been experimentally studied under fluidized bed combustion conditions. a simplified mathematical model of the heat and mass transfer controlled coupled drying and pyrolysis was established. Analytical solutions were obtained for a sphere, an infinite cylinder and an infinite slab. The solutions account for the difference in thermal characteristics between char and virgin dry biomass. The model gives a good representation of the measurements, provided that the thermal conductivity of the particle is used as a fitting parameter. The model was shown to be applicable to both isotropic dry and anisotropic biomass particles
