Parametric effects of particle size and gas velocity on cluster characteristics in fast fluidized beds

An important characteristic of fast fluidized beds (FFB) is the tendency for the solid particles to aggregate into clusters. Such clusters can strongly affect operational characteristics such as particle holdup, pressure drop, wall heat transfer, and axial mixing. This paper presents results of an experimental study of cluster characteristics, as determined by capacitance-probe measurements of instantaneous local solid concentrations in a 15-cm diameter FFB. Results are presented that indicate the parametric effects of particle size (dp) and superficial gas velocity (Vg) on the duration time, occurrence frequency, time-fraction of existence, and solid concentration in clusters.