Experimental results of a one-fifth scale cold laboratory model of a circulating fluidized-bed pilot plant for biomass gasification are reported hele. Measurements revealed that the solid circulation rate is a function of the superficial gas velocity in the riser and the total mass load in the system. A novel dimensionless scaling parameter introduced describes the dimensionless mass turnover. Experiments were carried out varying both particle diameter, 170 mum less than or equal to d less than or equal to 860 mum, and density, 1,480 kg/m(3) less than or equal to rho (S) less than or equal to 8,900 kg/m(3). An excellent prediction for the mass turnover was obtained for mass loads varying from I to 15 kg and throughout the whole particle size and density range using the equations derived Furthermore, the particle-size distribution is a scaling parameter to be matched between a model and an industrial plant.