Porous bed materials capture volatile matter as carbon deposits during fluidized bed combustion of high-volatile fuels such as biomass and wastes. Carbon deposits burn in a dense bed mixed with bed materials; thereby enhancing horizontal dispersion of carbonaceous materials. Commercial scaling-up requires a model that simultaneously assesses carbon deposit combustion and horizontal solid dispersion. This study measured the carbon deposit combustion rate using a fluidized bed. A one-dimensional model of carbon deposit combustion in a fluidized bed is based on the carbon deposit burning rate. A two-dimensional model incorporates reactions and solid dispersion to predict the horizontal concentration profile. Experiments using a bubbling fluidized bed validated that model. (C) 2007 Elsevier Ltd. All rights reserved.