Alumina Miniplant Operations--Influence of Reactor Design on the Attrition of Calcined Kaolin during HCl (Hydrochloric acid) Leaching

摘要

The Bureau of Mines investigated the extraction of alumina from calcined kaolin by leaching with boiling HCl in a train of three 50-gal continuous, stirred reactors. Slurry discharged from the reactors contained an excessive amount of fines, which impeded solid-liquid separation. Autogenous grinding of coarse solids that accumulated in the reactors was the source of the fines. This report describes modifications to the reactors and to the operations that led to decreased fines generation and improved solid-liquid separation. Modifications to the reactors included custom-made impellers, the addition of a baffle system, a subsurface slurry discharge system, and slower rotation of the impellers. Concurrent testing of a continuous horizontal belt filter showed that the form filtration rates were increased from 350 to almost 1,000 lb/h/sq ft when the modified reactors were used.