Experimental and Theoretical Study on Fluidization of Stalk-Shaped Biomass Particle in a Fluidized Bed

Abstract

Detailed knowledge of the fluidization mechanics of biomass itself, or of mixtures of biomass and inert particles is critical to successful design and operation of fluidized bed involving biomass. In this study, the fluidization behaviors of biomass alone and sand-biomass mixture were experimentally and theoretically studied. A segmented fluidized bed equipped with multiple pressure transducers was used as the experimental apparatus. The cotton stalk with a shape of stalk was employed as biomass material, and three different sizes of sand were utilized as inert particle. By mixing cotton stalk and sand, three binary systems were obtained, in which only the weight percentage of biomass particle in each mixture is different. The fluidized beds experienced the following states, depending on gas superficial velocity and initial mixture fraction: fixed, bubbling fluidization and turbulent fluidization. It is found that the additive of sand has positive influence on the fluidization of biomass and the initial arrangement of bed has influence on the development of pressure drop with the gas velocity. The developed equation for predicting the minimum fluidization velocity (Umf) of binary mixture quite satisfactorily predicts the Umf values of mixture with low biomass concentration. In addition, the correlation expressed in terms of Reynolds and Archimedes numbers to predict transition velocity (Uc) is proposed. Calculated Uc is in excellent agreement with the experimental data.