Hydrodynamic and heat transfer characteristics of bubble columns involving fine powders

Abstract

A 10.8-cm diameter slurry bubble column facility is described and experimental data for air hold-ups and heat transfer coefficients for two- and three-phase systems as a function of air velocity are presented. Fine red iron oxide powders of mean diameter 1.02 and 2.38 μm, and magnetite of mean diameter 43.6 μm are used as a solid phase, while water comprises the liquid phase. Solids concentrations in the slurry are varied in the range 0 – 404 kg/m 3 and air velocities in the range 0.108 – 0.362 m/s. Characteristic variations of air hold-up and heat transfer coefficients are observed as a function of air velocity, solids concentration and particle size. To shed some light on the mechanistic details of the heat transfer process, the temperature history of a heat transfer probe is monitored for slurries of different concentrations and different particle sizes as a function of air velocity.