Evolution Of The Pore Structure And Flow In Granular Ore Heaps For Copper Oxides Acid Leaching

It is of vital importance for leach heap to maintain well-structure pore networks and high permeability.Focused on the leaching of oxide copper ore,study of evlution of pore structure and flow during heap leaching was carried out to optimize fluid flow within ore heaps and to improve leaching performance by means of laboratory experiments,numerical simulation and theoretical analyses.The work involved is summarized as follow.First,the ore particle imaging experiments during copper oxides leaching was implemented.The intra-particle pore structure change under leaching reaction was illustrated through CT imaging,3D reconstruction and computer image processing,the intra-particle pore structure evolution law was revealed.The porosity,pore size and pore number had increased by about 40%,3.5%and 25%respectively in the leaching process.Second,the ore column imaging experiments during copper oxides leaching was implemented.The inter-particles pore was obtained by CT imaging,and the pore structure characterization was achieved by computer image processing,the one-dimensional,two-dimensional and three-dimensional porosity have been used to evaluate the pore structure.The time dependency of porosity,pore dimension,and hydraulic conductivity of the granular ore column under acid leaching was investigated.Third,the evolution laws of fluid flow in the dual-pore networks for copper oxides leaching were understood.Fractal dimension change of the pore networks during leaching was explored.The relation between fractal dimension,porosity and fracture dimension and fracture amount was ascertained,and a mathematical correlation was proposed.A fluid flow model was then built based on the fractal pore network analysis.Fourth,the saturated fluid flow and velocity field in this meso pore system was explored.MRI technology was employed to imaging saturated ore columns so as to visualize the fluid velocity field in the meso pore system.Indicators including standard deviation,coefficient of variation,and coefficient of uniformity were used to evaluate the uniformity of the velocity field.A finite element fluid flow model was built based on the MRI image of the ore column,and a numerical simulation of micro-scale seepage was implemented.The velocity field estimated by the model matches the fluid velocity analysis from the MRI test.Fifth,the co-evolution of fluid flow and pore structure in granular ore heaps was clarified.With the understanding of leaching reaction kinetics,the impact of acid erosion on intra-particle pore structure was resolved.The dynamic behavior of fluid flow through the acid leached pore network was thus exhumed.Sixth,optimized regulatory strategies for fluid flow during acid leaching were proposed.With the pore structure and fluid flow co-evolution characteristics elucidated,theories for regulatory strategies were then comprehended,based on which measures to improve the ore heap permeability were put forward.Aeration was suggested to enhance the fluid flow so as to accelerate leaching progress and improve leaching performance.