Particle Coherent Structures in Confined Oscillatory Switching Centrifugation

A small spherical rigid particle in a cylindrical cavity is considered. The harmonic rotation of the cavity wall drives the background flow characterized by the Strouhal number Str, assumed as the first parameter of our investigation. The particle immersed in the flow (assumed Stokesian) has a Stokes number St=1 and a particle-to-fluid density ratio ϱ which is assumed as the second parameter of this study. Building on the theoretical understanding of the recently discovered oscillatory switching centrifugation for inertial particles in unbounded flows, we investigate the effect of a confinement. For the first time we study how the presence of a wall affects the particle trajectory in oscillatory switching centrifugation dynamics. The emergence of two qualitatively different particle attractors is characterized for particles centrifuged towards the cavity wall. The implication of two such classes of attractors is discussed focusing on the application to microfluidics. We propose some strategies for exploiting the confined oscillatory switching centrifugation for selective particle segregation and for the enhancement of particle interaction events.

Study of The Biomass, Sand, and Biochar Fluidization in A Typical Bed of Fast Pyrolysis

Biomass pyrolysis usually occurs in a fluidized bed reactor formed by sand, biomass, and biochar. Dynamics this fluidization differs from that of literature because the biomass is converted continually in biochar. In this study, a series of experiments have been carried out for ternary mixtures of sand, sisal residue, and biochar, varying the compositions and particle size. The tests were based on two simplification hypotheses (steady state and room temperature) due to fast biomass transformation in bed and low Van der Waals force to large particles. The dynamic characteristics determined included the bed pressure drop and bed fluctuation. The single and combined effects of particle size and composition on the final fluidization velocity (Uff) and particle segregation (S) have been analyzed using response surface (RSM). The Uff and S minimum values were found when the variables were in the smallest particle size and composition levels. New correlations were developed for predicting the values of Uff. The error from measured values when using the new correlation was 7.6%, while the literature equation was 9.7%. The present correlations predicted reasonably well predicted the Uff of ternary mixtures in the fast pyrolysis bed.