Modeling the Autoclave Penetration of Gold-Bearing Refractory Ores

A number of gold-bearing concentrates are characterized by a high degree of refractoriness as a result of the strong bond between the finely dispersed gold and the crystalline lattices of pyrite (FeS2) and arsenopyrite (FeAsS). Such concentrates are broken down by a reaction that involves the oxidation of the pyrite by oxygen and is accompanied by interactions between solid, liquid, and gas phases at high temperatures and pressures. Results from studies of the kinetics of the pyrite oxidation process were used to construct a mathematical model of this process, perform a parametric identification, and evaluate the adequacy of the model. The model’s adequacy was determined based on the value of the determination coefficient (R2) and the standard error, which were respectively found to have values of 0.9948 and 0.0253. The results of the parametric identification led to values of 34 and 91 kJ, respectively, as the activation energy of pyrite in oxidation reactions with oxygen and Fe3+, respectively. Parametric identification made it possible to determine the dependence of the rate of the process on the degree of conversion of pyrite as a factor that characterizes the role which passivation of its surface plays in the oxidation process. This factor was determined to have a value of 0.72.