Patent ID: 7563325
Filing Date: 2009-07-21
Classification: B01J,B05C

Abstract:
1. In a Wurster fluidized-bed particle coating apparatus, said apparatus including a bowl having a lower peripheral flange, a plenum beneath said bowl, a gas source of conditioned fluidizing gas for pressurizing said plenum, a perforated gas distribution plate having an upper surface separating said plenum from said bowl, and at least one Wurster tube within said bowl and spaced above said perforated gas distribution plate, said Wurster tube defining a central up-bed particle flow region and a surrounding down-bed particle flow region and having spray nozzle means for directing a spray of coating liquid into said up-bed particle flow region for coating said particles, the improvement comprising: a) an annular bypass gas cavity underlying said bowl lower peripheral flange, and b) flow redirection means for supplying a bypass flow of conditioned fluidizing gas directly from said plenum through said annular bypass cavity and inwardly across the upper surface of said perforated gas distribution plate, whereby particles accumulating at said bowl lower peripheral flange are swept toward said at least one Wurster tube.