Patent ID: 6692571
Filing Date: 2004-02-17
Classification: B01J,Y10S

Abstract:
The improved Wurster-type fluidized bed apparatus for applying a coating liquid onto the surface of particles, said apparatus being of the type including a vertically disposed generally cylindrical product container having a peripheral wall, at least one cylindrical partition defining a centrally located up-bed region and a peripherally located down-bed region, said product container further including an upper end connected to an expansion chamber, a lower end including an orifice plate having a plurality of openings for passage of fluidized air, a nozzle centrally located through said orifice plate and being adapted to generate a spray of said coating liquid upwardly into said up-bed, wherein said particles located within said product container circulate upwardly through said partition and said spray of coating liquid, between said up-bed and said down-bed, said improvement comprising:a central first plenum located below said orifice plate and being aligned with said up-bed and said partition, said first plenum being sized and shaped to direct gas upwardly through said orifice plate and into said up-bed; a second plenum located below said orifice plate positioned around said first plenum for directing gas upwardly through said orifice plate and into contact with particles located on said orifice plate; a first source of gas connected to said first plenum; and a second source of gas connected to said second plenum.