Patent ID: 6579365
Filing Date: 2003-06-17
Classification: B01J,Y10S

Abstract:
An 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 plurality of inwardly directed discharge jets positioned along the periphery of said cylindrical product container and generally adjacent to said orifice plate; and a source of pressurized gas connected to said plurality of discharge jets for selectively providing a radially inwardly directed flow of gas through said particles of said down-bed so that said particles located adjacent to said peripheral wall of said product container are displaced radially inwardly along said orifice plate towards said nozzle and said up-bed.