Sulphuric acid pressure leaching of laterites - a comprehensive model of acontinuous autoclave

The high-temperature acid pressure leaching of nickeliferous laterites empl oys multi-compartment continuous autoclaves treating a variety of lateritic feeds. Previous work has correlated the kinetics of nickel dissolution, as well as the solubility of important metals in this process, with acid conc entration levels calculated at the temperature of leaching. This was achiev ed by a speciation analysis resulting in a universal kinetic equation for N i dissolution from limonitic feeds and from limonitic/saprolitic blends. In the present work, these findings were combined to develop a comprehensive model for a continuous multi-compartment autoclave. To this end, the kineti cs of Co, Fe, Al, and Mn was also estimated and included in the reactor mod el. The resulting model is capable of predicting Ni extraction and concentr ations of major impurities during autoclave operation for a wide variety of process conditions and feed compositions. It was implemented in a computer simulator that can be used to investigate diverse process scenarios and to select acidity levels for different types of feed. Finally, the model is c ompared with continuous mini-plant pressure acid leaching data as provided by INCO Technical Services (ITSL) during process development campaigns. (C) 2000 Elsevier Science B.V. All rights reserved.