Abstract The Reflux Classifier (RC) is an innovative device offering advantages both in separating particles according to size and density, and in solid–liquid separations. The system combines a conventional rectilinear fluidized bed with sets of parallel inclined plates. Our previous work shows that the inclined plates within the fluidized bed provide a simple means for increasing the particle classification, sedimentation and liquid clarification throughput. This paper discusses the virtues of the Reflux Classifier by examining the synergy of the interactions produced by the inclined plates and the fluidized bed. New and published experimental data are reviewed to demonstrate the potential of this system for a range of industrial applications in solid–liquid processing.