Particle separation with respect to size is investigated using an air classifier based on a fluidized bed principle. The apparatus consists of a vertical rectangular chamber, conveying upward flowing air. A fluidized bed is formed by solid particles loaded onto an air distributor grid, placed in the lower part of the a classifier. This promotes increasing of the particles' residence time in the separation zone, thus raising the separation efficiency. A set-up based on the above principle was designed and constructed. It includes a laboratory scale classifier, cyclone, fan, feeder and a system for measurement of the pressure drop, air velocity and flow rate. The investigation was directed to study the influence of several important parameters on the cut size and separation efficiency, and was carried out on quartz sand composed of particles with sizes ranging from 50 to800 #mu#m. The experiment results show, that by use of the fluidized bed air classifier it is possible to regulate easily the cut size and to obtain the separation products of 85-95% cleanness at recovery values up to 94%. These values change insignificantly with the loading varying in a wide interval, which is very important for practical purposes.
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