The development of efficient operation and control of a biomass boiler requires extensive knowledge of the combustion process inside the boiler furnace However, it is not possible to obtain the required knowledge through process measurements because the high temperatures and aggressive environment inside the furnace prevent taking accurate sensor readings. Instead, the process can be studied with the help of mathematical modeling. This paper describes dynamic modeling of bed combustion in a BioGrate boiler furnace. The developed dynamic model is heterogeneous, including solid and gas phases and corresponding reactions. The model is used for process phenomena investigation; the results are presented and discussed. (C) 2011 Elsevier Ltd. All rights reserved.