GTE Sylvania, Towanda, PA
Calcium Carbonate


Calcium carbonate is used to make phosphor powder for lamps. Dryness of product is critical. The former method of drying was batch-type rotating vacuum dryers that required maintenance of vacuum pumps and steam jacketing, both costly. Obtaining high vacuums required careful scrutiny of entire system. Operation was time consuming for personnel. The company purchased a l2-shelf rotary tray TURBO-DRYER® that operates continuously and automatically. Little operator attention is necessary. By controlling speed of tray rotation, residence time can be varied to adjust dryness of the final product. Dryer is heated with air, and a recycle system reclaims heat that would otherwise be lost. Moisture laden air from the dryer goes to a baghouse to retain any entrained fines. Air stream is then split. A percentage is exhausted; the rest goes to an electric heating coil, where it is supplemented by heated make-up air to control humidity. Moisture content of the carbonate powder has been reduced satisfactorily from about 30% to 0.0 1%. GTE now has a continuous operation that yields product at a higher rate than was previously possible.


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