Studies on the mathematical modeling of circulation rates of particles in bubbling fluidized beds

A methodology to obtain two-dimensional profiles for the particle velocities and circulation rate of solid particles in bubbling fluidized-bed is developed. The work is based on the forms presented by Soo [S.L. Soo, Powder Technology 45 (1986) 169-172; 57 (1989) 107-117], but a critical review of his treatment is made. The calculations require estimations for the particle slipping velocity at reactor wall and apparent viscosity of the bed. Relationships for those are described by several authors and sharp differences between the computed values are noticeable. Computations of average circulation rate of particles show reasonable agreement with values calculated from semi-empirical correlation for a relatively wide range of bed operational conditions. The present solution is much simpler than those which require the complete solution of momentum equations. Therefore, it allows applications to comprehensive simulation programs without sacrifices on the computational time. Circulation rate and temperature profiles for a boiler are shown. The work paves the way for a treatment where various species of particles may be present in the bed. (C) 1999 Elsevier Science S.A. All rights reserved.