Coating Pellets on a VIBROSCREEN
More than 20 years of experience show that Kason separators serve well for classifying, scalping and other screening operations. With slight modifications, the same gyrator that helps the on-spec material get through the screen helps coat sticky pellets with powder. Several companies who contacted us with problem materials that required a powder coating have found that Kason engineers have the answers. Because shipping sticky material is difficult, many companies prefer to ship it in the form of coated pellets.
A manufacturer of adhesive pellets used for rubber processing couldn't ship pellets without their becoming congealed into multi-pellet conglomerations. His customers complained, and the company determined that by coating the pellets with nonreactive powder, the pellets would remain discrete during shipping. Typically , a 30 inch diameter VIBROSCREEN can coat about 2000 pounds per hour of sticky pellets with 25 to 50 pounds per hour (1-2% of weight of pellets) of nonreactive powder.
Co-inventors Peter Dickson of Separator Engineering in Scarborough, Ontario, and Kason engineer, Gary Datta, found that by placing a 12 inch diameter plastic chamber on the screen of a VIBROSCREEN separator and feeding a small percentage of nonreactive powder to the chamber, non-sticky pellets could be produced continuously. The only modification to the VIBROSCREEN is to set the lead angle slightly higher to increase the residence time of the pellet in the coating chamber.
Similarly, a manufacturer of dough balls used for fishing faced the same problem of keeping balls discrete. Although powders may vary from one application to another , the process is proven. The pellets can be fed by augur or inclined chute, the powder is fed into the coating chamber where it is fluidized by the vibratory motion imparted by the gyrator. The pellets become coated as they roll from near the center of the chamber out over the edge. After the pellets leave the chamber and land on the screen, excess powder falls off the pellets, passes through the screen, and collects for recycling while the coated pellets roll off to the oversize discharge spout.
Screen Tips - Volume 4, Number 3 FALL 1989