Chemical vapour deposition of silicon from silane on fluidized powders is an efficient and flexible surface modification technology; however, its main drawback is the agglomeration of the fluidized particles beyond a critical initial concentration of silane. To clarify this phenomenon, we have studied the influence of operating conditions covering temperatures lower than 550 degreesC, both experimentally and theoretically using the simulation model of Kato and Wen (1969). The influence of the main operating parameters has been accurately determined not only on the process throughput but also on the thermal behaviour of the bed, which is directly linked to the solid phase motion and then to the possible agglomeration of particles.