The pyrolysis of a freely moving cellulosic particle inside a 41.7 mg s(-1) continuously fed fluid bed reactor subjected to convective heat transfer is modelled. The Lagrangian approach is adopted for the particle tracking inside the reactor, while the flow of the inert gas is treated with the standard Eulerian method for gases. The model incorporates the thermal degradation of cellulose to char with simultaneous evolution of gases and vapours from discrete cellulosic particles. The reaction kinetics is represented according to the Broido-Shafizadeh scheme. The convective heat transfer to the surface of the particle is solved by two means, namely the Ranz-Marshall correlation and the limit case of infinitely fast external heat transfer rates. The results from both approaches are compared and discussed. The effect of the different heat transfer rates on the discrete phase trajectory is also considered. (C) 2008 Elsevier Ltd. All rights reserved.