Development of an integrated heap leach solution flow and mineral leaching model

Abstract

A 1-dimensional solution flow and mineral leaching model was developed to simulate data from leach columns and to demonstrate a dual porosity approach whereby an ore bed is divided into mobile (advective) flow and stagnant (diffusional control) regimes. Hydrodynamic properties were modelled with Richard's and van Genuchten's equations, and hydrodynamic column tests were performed to measure the parameters needed to solve these equations. The solute balance was performed using the standard advection-dispersion equation used in soil dispersion models. However, the term describing the desorption of solute (copper) from the solid into the liquid phase was replaced with a shrinking core reaction model rate term.The model shows that the proportion of the ore bed governed by diffusion increases as the diameter and height of the bed increase. The hydrodynamic properties therefore appear to have a significant effect on the copper extraction profiles and, if so, this could provide an explanation as to why large scale heaps leach slower than columns. The mass transfer coefficients for solute transfer between the mobile and stagnant regimes were of a similar order of magnitude as reported in tracer studies in literature.