In the design of processes involving exothermic reactions, as is the case of several sulfide leaching systems, it is desirable to utilize the energy liberated by the reaction to drive the reactor toward autogenous operation. For optimal reactor design, models which couple leaching kinetics and heat effects are needed. In this paper, the principles of modeling exothermic leaching reactions are outlined. The system investigated is the high-temperature (160 °C to 200 °C) pressure (O2) oxidation of arsenopyrite (FeAsS). The reaction system is characterized by three consecutive reactions: (1) heterogeneous dissolution of arsenopyrite particles, (2) homogeneous oxidation of iron(II) to iron(III), and (3) precipitation of scorodite (FeAsO4-2H2O). The overall kinetics is controlled by the arsenopyrite surface reaction. There was good agreement between laboratory-scale batch tests and model predictions. The model was expanded to simulate the performance of large-scale batch and single-stage continuous stirred tank reactor (CSTR) for the same rate-limiting regime. Emphasis is given to the identification of steady-state temperatures for autogenous processing. The effects of operating variables, such as feed temperature, slurry density, and retention time, on reactor operation and yield of leaching products are discussed. © 1990 The Minerals, Metals & Material Society.
