Modelling of the nickel and cobalt kinetics during pressure acid leaching of laterites using Aspen Plus 11.1(TM) and OLI

The sulphuric acid pressure leaching process of lateritic ores employs an autoclave reactor operating at 230 to 270°C under vapour pressure. During this process, sulphuric acid selectively leaches nickel and cobalt values into the aqueous solution. The process has been commercially employed because it gives high nickel and cobalt extractions. In this thesis, the autoclave leaching process was simulated using commercial software, namely: Aspen Plus 11.1, Mathematica 5.0 and OLI. Kinetic parameters of acid-driven metal dissolution and precipitation reactions were determined from published experimental data using Mathematica 5.0. A dedicated thermodynamic database previously developed at the UofT was also used. Modelling accounted for hydrogen ion concentration at temperature as calculated by a full speciation via the OLI software. Mass balances were handled by Aspen Plus. It was found that the model gave very satisfactory predictions on nickel under industrial leaching conditions. Cobalt predictions fell below the experimental error for limonite leaching experiments.