A MATHEMATICAL-MODEL FOR HEAP LEACHING OF ONE OR MORE SOLID REACTANTSFROM POROUS ORE PELLETS

A mathematical model is derived in dimensionless form for heap leachin g of one or more solid reactants from nonreactive, porous, spherical o re particles. The model is for the interpretation of column and heap l eaching data and for use in the design and scaleup of heap leaching pr ocesses. Data from experimental column leaching tests are presented wh ich validate the model. The scope of the present study is limited to t he case where the rate-controlling reagent is a component of the lixiv iant solution only and not of the gas phase. The effects of particle-s cale kinetic factors, heap scale and operating variables, competition between multiple solid reactants, and particle size distribution are e xamined using the concept of the heap effectiveness factor. It is show n that heaps operate either 'homogeneously,'' with distribution of rea gent throughout the heap at all times, or in a ''zone-wise'' manner, d epending mostly on a single parameter. The observed value of this para meter deviates from the predicted value in inverse proportion to the d egree of contact effectiveness between the lixiviant solution and the ore particles. A rough correlation between the contact effectiveness a nd Reynolds number is generated from the simulation of column test res ults.