Three dimensional CFD modelling of the effect of some operating parameters on particle trajectories in a rotating fluidised bed combustors

Abstract

The objective of the research was to investigate the trajectories of particles in a horizontal rotating fluidised bed (RFB) combustor. Due to the conservation of momentum, the gases in a RFB are imparted a tangential velocity component which accelerates as they converge to the exit. Dependent upon the type and size of particle, this unique feature causes particles in the RFB to be returned to be bed, be captured and remained in circular orbit in the freeboard region of the primary chamber or be blown out of the combustor. Hence, computational fluid dynamics (CFD) modelling had been performed using the FLUENT program code to chart the trajectory of rice husk ash particles of various sizes in a RFB operated at different rotating speeds and air feed rates. It was found that, in general, particles of size less than 5um were rapidly blown out of the combustor while particles in the range of 10-50um were retained in the primary chamber. Larger-sized particles (>50um) tended to move towards the distributor due to higher momentum.