Fluidization of binary mixtures of biomass and coal with sand: an experimental study

The aim of this work was to characterize the fluid dynamic behavior of mixtures of biomass with sand as inert material and to determine the fluidization curves of each mixture. For comparison purposes, mixtures of coal with sand were also studied. Biomasses investigated were eucalyptus bark ( Eucalyptus sp.), pine bark ( Pinus elliottii ), and pine wood chips. The experiment was performed in a scaled cold reactor with internal diameter of 94 mm and 1200 mm in height. Samples had average particle sizes of 0.537 mm (eucalyptus bark), 0.579 mm (pine bark), 0.729 mm (pine chip) and 0.680 mm (coal). The mixtures with sand were made in proportions between 20 and 60% of biomass or coal in volume. Fluidization curves were analyzed, and the minimum fluidization velocity ( u mf ) was determined. The minimum fluidization velocity was highly affected by biomass concentration and type, meaning that even for similar density and particle size, biomass morphology and composition are influential features in the process of fluidization. The experimental results of the minimum fluidization velocity were compared with empirical correlations from literature. The errors were very large, suggesting the need to develop specific correlations for these types of biomasses.