Abstract
Glass beads were coated in a fluidized bed by atomizing the suspension of nylon or silica fine powder. Polyvinyl alcohol (PVA) was used as a binder. The influences of thermal operating conditions such as the feed rate of the atomized powder suspension, the temperature and the humidity of the inlet gas on the coating efficiency, were mainly investigated. When the moisture content in the coated layer around seed particles was kept high, high coating efficiency was obtained. An index R, which evaluates the drying condition in a fluidized bed quantitatively, was defined by the ratio of the humidity of outlet and saturated gas. The coating efficiency increased under the thermal operating conditions which corresponded to high values of R. R is useful for estimating the coating ability of the materials used and of the coating apparatus.
