Continuous multicell process and apparatus for particle coating including particle recirculation

An apparatus for applying coatings to discrete particles comprising:

• means defining a substantially closed chamber;
• a plurality of partitions disposed on longitudinal spacing throughout said chamber dividing said chamber into a plurality of cells;
• substantially vertically extending conduit means defined by a hollow duct disposed in each of said cells, said conduit means having open upper and lower ends spaced vertically from adjacent upper and lower surfaces of said chamber;
• gas distribution means for supplying operating gas to the bottom of each cell and for directing it in vertical streams to the top thereof, said means including devices for directing a first gas flow through the interior of a said conduit means to develop a gas flow therein having a first velocity and a second flow of gas externally of said conduit means at a second velocity, which is less than that of said first gas flow;
• means for supplying coating material in a diffused spray to the interior of said conduit means;
• means for supplying discrete particles to be coated to a cell at one end of said chamber whereby said particles are entrained in operating gas for controlled circulation through said cell in an upward direction through the interior of said vertically extending conduit means in contact with the spray of coating material therein and in a downward direction in a subsidence zone exteriorly of said conduit means;
• means for discharging coated product from a cell at the other end of said chamber;
• means for discharging operating gas from an upper region of said chamber;
• and
• means forming openings in each of said partitions for effecting the flow of particles into succeeding cells, whereby said particles are selectively recirculated a predetermined number of times through said conduit means for contact with said coating material.