PARTICLE JETS IN FLUIDIZED-BEDS

When particles are fed via a nozzle into a fluidised bed beneath the bed surface, a jet will form. Apparatus was built and a probe was developed to determine velocity profiles in such jets. The probe measures the force on a sphere in the bed. To calibrate the probe, it was moved through the stagnant bed. In this way a plot of drag coefficient vs. Reynolds number was obtained. The damping of oscillations of the probe, when given an initial deflection, was measured. The experimental results were compared with theory for Newtonian liquids giving an estimate of fluidised bed viscosity. The Cd-Re relation and the damping rate agree with theory for a viscosity of 0.04 Pa s. The jet profiles agree with theory for a viscosity of 0.3 Pa s. This discrepancy indicates that application of the fluidised bed Newtonian liquid analogy is not entirely straightforward.