A devolatilization model based on simplification of the earlier model has been developed for fluidized bed conditions. It is simple and computationally fast enough to be incorporated as a submodel into a CFD code, but accurate enough to be suitable for different fuels including biomass with varying particle size, moisture, reactivity and shape. In this new model, the partial differential equation describing heat and mass transfer inside the particle is approximately converted to two differential equations. Drying is described to take place on a shrinking core and pyrolysis, which can take place simultaneously with drying, is described to take place at a specific "characteristic pyrolysis temperature". The dependence of this temperature on parameters for the kinetics of pyrolysis, bed temperature and particle size can be determined. The model can be extended to include the case, where pyrolysis is considered to consist of parallel reactions of different components. (c) 2006 Elsevier Ltd. All rights reserved.