Pre feasibility study in hydrometallurgical treatment of low-grade chalcopyrite ores from Sarcheshmeh copper mine

Abstract

Chalcopyrite heap leaching is not yet a commercial reality, not just because of its lower recovery or slower kinetics, but rather, because of the economic impacts lower recovery and slower kinetics impose to the operating cost of the process. Considering the importance of the financial analysis on the economics of the operation, in this research, the economics of hydrometallurgical treatment of low-grade chalcopyrite deposit at Sarcheshmeh mine as a function of ore grade and extraction recovery were investigated. First, a brief history and theory of chalcopyrite ore leaching has been reviewed, showing that bio heap leaching at a possibly higher temperature with forced aeration is the only viable technique in treatment of low-grade chalcopyrite ores. In the economic feasibility study section, an operating cost estimate, capital cost estimate and economic analysis for a plant with 7000 tons per year copper cathode production capacity as a function of ore grades, acid consumption and heap leaching recoveries were investigated. Preliminary capital cost and operating cost estimates were made within two scenarios for a plant utilizing bio heap leaching, solvent extraction and electrowinning of low-grade chalcopyrite ore. The operating cost, for instance, was shown to be between US$5.99/kg to US$4.29/kg of copper cathode for extraction recoveries of 30% to 50% in a scenario where the construction of new SX and EW plants are required (Scenario 1). The operating cost was shown to reduce to US$5.36/kg to US$3.66/kg, for a similar recovery range, if the current SX and EW facility can absorb the bio heap leaching solution (Scenario 2). Using the operating cost data and the current copper selling price, the ore cut-off grade as a function of copper extraction efficiency was identified. The economic analysis showed that for an ore containing 0.28% copper, 7000 tons per year of copper cathode production requires a total investment of 38 million US dollar. The internal rate of return for such a plant was shown to vary between −2% to 27% for copper extraction efficiencies between 30% to 50% (Scenario 1). The sensitivity analysis of the similar plant showed that a copper selling price of US$5/kg, for instance, can even make the 50% copper extraction efficiency economically unacceptable for scenario 1.