This work analyzes and discusses the general features of biomass pyrolysis, both on the basis of a new set of experiments and by using a detailed kinetic model of biomass devolatilization that includes also successive gas phase reactions of the released species and is therefore able to predict the main gases composition. Experiments are performed in a lab-scale Entrained Flow Reactor (EFR) to investigate biomass pyrolysis under high temperatures (1073-1273 K) and high heating fluxes (10-100 kWm_2). The influence of particle dimensions and temperature has been tested versus solid residence time in the reactor. The particle size appeared as the most crucial parameter. The pyrolysis of 0.4 mm particles is nearly finished under this range of temperatures after a reactor length of 0.3 m, withmore than 75 wt% of gas release, whereas the conversion is still under evolution until the end of the reactor for larger particles up to 1.1 mm, due to internal heat transfer limitations. The preliminary comparisons between themodel and the experimental data are encouraging and show the ability of this model to contribute to a better design and understanding of biomass pyrolysis process under severe conditions of temperature and heating fluxes typically found in industrial gasifiers.