Insights from simulation of CIL/CIP circuit Part 1 – model development

A semi-empirical model was developed to represent a carbon in leach/carbon in pulp (CIL/CIP) circuit for recovery of gold and silver. The model uses a simple two rate representation of the leaching kinetics. Parameters for the leaching kinetics may be obtained by sampling the feed to a circuit and the tailings from each tank and assaying the solids for both gold and silver to obtain the assay profiles of the solids down the tanks. The parameters in such a leaching model would be expected to be a function of the ore type, the grind, cyanide concentration, whether oxygen was used and the general chemical environment. The leaching parameters are primary inputs to the model for any simulation. Standard power law relationships are used express the practical equilibrium between the gold and silver cyanides adsorbed on the active carbon and the tenor of the solution. There is an underlying assumption that the residence of time of carbon in the tanks is sufficient for the carbon loading and solution concentration to be close to equilibrium. The parameters for this relationship are also derived from plant data. The model was constructed by writing a mass balance for gold and silver in and out of each tank in the train and for the circuit overall. Other inputs to any simulation are the feedrate of ore, per cent solids of the slurry in the tanks, gold and silver loadings of the input ‘barren’ carbon and the rate of movement of carbon through the circuit counter current to the slurry. With appropriate practical parameters, the simulation is able to reproduce typical tank profiles.