A mathematical model for the solution mining of primary copper ore: Part I. leaching by oxygen-saturated solution contai
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INTRODUCTION
D U R I N G the last decade, the feasibility of applying solution mining technology to the recovery of copper from deeply buried deposits containing chalcopyrite has received much attention. ~-4 The major incentive for using this technology is that under certain circumstances, copper in deep underground deposits, which cannot be mined economically by conventional means, can be recovered economically. Basically, this technology involves rubblization of the deeply buried copper ore body followed by in-place leaching of the rubblized copper ores. Rubblization of the ore can be achieved by some suitable method such as explosive fracturing or the use of block caving mining. The rubblized chimney is then filled with water until the original water level is reached. Leaching occurs when the water saturated with oxygen is introduced into the chimney, flows through the fractured rock masses, and fills available pore space within the rocks. At the beginning some acid may have to be added to the water. As the dissolved oxygen oxidizes the primary sulfides, heat as well as acid is generated. Because of low conductivity of the surrounding rocks, the generated heat is able to raise the temperature of the chimney. The increase in the temperature of the chimney and the relatively high content of dissolved oxygen in the leach solution under high hydrostatic pressure will result in an enhanced dissolution of the primary sulfide minerals. To ensure a successful application of the in situ leaching technology, a complete understanding of the effects of the ore particle size distribution, ore grade mineralogy, temperature, pressure, lixiviant concentration, pH, etc. on the rate of copper recovery is necessary so that copper can be
H. W. GAO, Postdoctoral Associate, and H. Y. SOHN, Professor, are with the Department of Metallurgy and Metallurgical Engineering, University of Utah. M.E. WADSWORTH is Professor of Metallurgy and Metallurgical Engineering and Dean of College of Mines and Mineral Industries, University of Utah, Salt Lake City, UT 84112-1183. Manuscript submitted March 22, 1982. METALLURGICALTRANSACTIONS B
recovered efficiently and the amount of copper extracted can be predicted. This objective can be achieved through mathematical modeling of the in situ leaching process and conducting laboratory tests. In this paper we will present a mathematical model that simulates the in situ leaching process as depicted in Figure 1. To model this process properly, not only the kinetic and thermodynamic aspects of leaching chemistry must be known, but the effects of heat generation, the physical aspect of fluid flow, and other related multicomponent transport phenomena must be considered. Furthermore, since most factors involved in the leaching process change with time, a leaching system can best be described using unsteady-state equations. Laboratory studies of the leaching of primary copper sulfide ores conducted by Braun et al. 2'5 have provided the necessary leaching chemistry and kinetics for the in situ copper leach
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