A laboratory scale fluidized bed reactor was developed to investigate the combustion characteristics of selected solid fuels (wood, paper sludge, refuse derived fuel). The aims were to introduce the means of experimental determination of the solid fuel particle characteristics through the pyrolysis and combustion processes. A nearly single particle combustion condition was reproduced in a fluidized bed and the progress of reaction was observed by determining the rate of carbon conversion, the overall recovery of carbon in gas phase, and the mean conversion time, which were determined by measuring the gas phase carbon containing species, namely CO and CO2 at the exit of the combustor. For a fuel particle whose characteristic length was a few centimeter in a fluidizing environment of 600-800 ℃ sand in a thermally maintained reactor, the sub-processes of fuel drying, pyrolysis as well as the combustion of residual carbon were clearly identified. Major parameters which affect the overall and individual combustion processes were evaluated in terms of the fuel properties and the combustion environment.