Thermodynamic Modeling of Arsenic in Copper Smelting Processes
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TRODUCTION
INDUSTRY interest is growing in the deportment of arsenic (As) between various phases during the processing of base metal concentrates. This interest is driven by the gradual depletion of high-grade ore with low levels of impurities such as As, the requirements to manage the emission of toxic elements to the biosphere, and a growing need to produce high-purity salable products. Current knowledge and understanding of the factors affecting the deportment of arsenic between phases during concentrate smelting, matte converting, and copper refining are limited, dispersed in literature, and often incoherent to allow the development of optimum practices readily for the efficient removal and safe disposal of arsenic. Thermodynamic modeling, based on equilibrium calculation, has been used to simulate the minor elements distribution behavior in the copper smelting process through several studies.[1–4] In these studies, the system equilibrium is calculated by using the equilibrium constant method, in which the required activity coefficient equations or the equilibrium distribution ratio of components basically are derived from the experimental data on simple systems. An issue with this approach results from the extrapolation of the empirical equation(s) of the component’s activity coefficient or distribution ratio from simple systems to complex industrial high-order systems. The second issue to consider is the possible departure from equilibrium in industrial processes and the effects of some process CHUNLIN CHEN, Senior Research Scientist, LING ZHANG, Principal Research Scientist, and SHARIF JAHANSHAHI, Theme Leader-Sustainable Processing, are with CSIRO Minerals Down Under National Research Flagship, Clayton South, VIC 3169, Australia. Contact e-mail: [email protected]. Manuscript submitted July 2, 2009. Article published online September 8, 2010. METALLURGICAL AND MATERIALS TRANSACTIONS B
variables on the degree of disequilibrium in such processes. The present work was initiated with these issues in mind and was aimed at the development of enabling tools to analyze reactions taking place in smelting and converting processes, with ongoing work focusing on factors affecting the kinetics of reactions in smelting processes. Since the early 1990s, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) has been developing a thermodynamic modeling package called Multi-Phase Equilibrium (MPE) software using the CALPHAD method[5] for the calculation of multiphase equilibrium in metallurgical systems. This software has been applied successfully in the design and/or optimization of various smelting and metal-refining processes.[6,7] A broad range of oxide components, such as SiO2, Al2O3, Cr2O3, TiO2, Ti2O3, Fe2O3, FeO, CaO, MgO, MnO, CrO, PbO, NiO, CoO, ZnO, Na2O, and Cu2O have been included in its slag and solid solution databases. One of the recent developments has been to extend the MPE model capability to cover the behavior of minor elements, such as arsenic, antimony etc. and to use this software to analyze
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