Dual Pore-system Ore Aggregates Characterisation And Leaching Behaviours Modelling

By means of micro-computed tomography(?CT),three dimensional image processing and numerical simulation,the micro-/macro-structure and the hydraulic properties of ore aggregates was studied,a framework for ore aggregates characterisation was proposed,a pore-scale leaching model that couples the fluid flow,mass transport,reaction and heat transfer sub-processes was established as well;numerical simulation of the copper oxide leaching process using the suggested model was carried out to unveil the dynamic interaction of these sub-processes.This entire work covers the following five aspects.First,the ore column and two ore particles were scanned on a ?CT machine,and the morphology of individual particles and the aggregates was analysed utilising three dimensional image processing algorithms.A framework for ore aggregates characterisation by particle size distribution,sphericity,particle alignment,minerals distribution,and for pore network characterisation by length of pore throat,area and perimeter of pore throat cross-section was proposed.The validity of the three dimensional image processing algorithms were then verified by the results of conventional lab tests.Second,two approaches for image based hydraulic properties predictions were put forward.One is formulated according to the Carman-Kozeny empirical equation that makes use of the ore aggregates image based granular structure characteristics;another is based on Navier-Stokes flow simulation in direct pore(image)geometry.Seepage tests for the ore aggregates were implemented to evaluate the reliability of the prediction of permeability.From a large dataset of pore throat cross-section images,both the multi-parameter(circularity-convexity-elongation)shape factor and the dimensionless conductance were calculated;a simplified relation between dimensionless conductance and shape factor was established using an optimised Backpropagation Neural Network.Third,a dual pore-system granular geometry based on CT ore aggregates was constructed in the light of recognised micro_/macro-structure difference.A two-domain flow model was built based on the Navier-Stokes equation and Brinkman's equation couplings.The two-stage flow during heap leaching was simulated employing the two-domain flow model;meanwhile,the preferential flow was visualised.The importance of the micro-pore system was addressed through the two-stage flow simulation.Fourth,an advanced dual pore-system granular geometry comprised of macro-pore,gangue and malachite domains was set up to build a pore-scale leaching model that features thermal-hydraulic-chemical coupling processes.Theoretical formulations were developed on the basis of the two-domain flow model,a two-domain convection-diffusion mass transport equation set for the macro pore and gangue domains,a three-phase convection-conduction heat transfer equation set for all three domains,a volumetric reaction equation for gangue dissolution,and a modified-shrinking-core-model surface reaction equation for malachite dissolution were incorporated,and then interlinked.At the end,the copper oxide leaching process was simulated deploying the dual pore-system leaching model.The profiles of velocity field,ions(H+,Cu2+ and Ca/Mg2+)concentration,temperature and leaching rate of Ca/Mg oxides and malachite were revealed;the change of ions concentration,temperature and leaching rate over time was illustrated;key factors influencing leaching efficiency were analysed.A mini-scale column leaching experiment was launched to validate the model.Leachate H+ concentration,Cu and Ca/Mg leach rate were monitored and compared with simulation results.Possible causes leading to the inconsistency between experimental and simulational results were investigated.