AMAX wanted to dry a highly pyrophoric, water-wet, metallic zinc powder from 20% to less than 0.5% moisture as well as maintain 99.99% purity. Zinc, recovered electrolytically, requires drying before being cast into ingots for subsequent shipment or distribution. Conventional air drying techniques produce a white zinc oxide coating on the gray, sand-like particles, and in some instances, actual conflagration occurred when the dry state was approached. A TURBO-DRYER® using recirculated nitrogen was installed. The unit provides intimate drying gas contact with the zinc powder, facilitating close temperature control. The low exit gas velocities eliminate the need for dust collection. The system produces 150 Ib/hr of 99.99% zinc with no white oxide impurities and without the danger of fire.

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