Physical modelling and hydrodynamic characterization of an internally circulating fluidized bed for biomass fast pyrolysis

This study investigates the hydrodynamics of the cold flow model (CFM) of an internally circulating fluidized bed (ICFB) finalized to biomass fast pyrolysis. The ICFB, basically consisting of a bubbling fluidized bed interconnected with a moving bed, is designed aiming at high fuel particles heating rates, efficient solids mixing and low gas residence times. Experimental techniques such as basket collection, solids and gas tracing are adopted to determine solids circulation rates, gas bypassing and particles residence times, consequently a compartment model of the CFM is proposed. The influence of operating conditions such as bed inventory and superficial gas velocity is investigated together with the effect of the opening ratio between the two interconnected beds. Results highlight that different operation regimes can occur and an optimization of operating and design parameters allows high solids circulation rates, low gas bypass and residence times lower than 1 s, as pursued in fast pyrolysis.