Abstract
The slags generated in the conventional copper conversion process are mainly composed of Cu2O–Fe2O3–SiO2 with CaO, Al2O3, and MgO compounds—in concentrations up to 10 wt %. The present work contributes to the knowledge of the conversion process, generating experimental data for the phase diagrams of the Cu2O–Fe2O3–SiO2–Al2O3 and Cu2O–Fe2O3–SiO2–CaO systems. The experiments were carried out in a tubular furnace at temperatures of 1150 °C and 1200 °C, under a condition of saturation with tridymite and spinel. Once the equilibrium was reached, the samples were immediately quenched in water. The phases in the samples were observed through a scanning electron microscope (SEM) and the elemental composition of the phases were analyzed by means of energy-dispersive X-ray spectroscopy (EDS) detectors. The addition of Al2O3 and CaO into the Cu2O–Fe2O3–SiO2 system resulted in an appreciable displacement of the liquidus lines, corresponding to an expansion of the liquid in the tridymite primary phase field. The addition of CaO and Al2O3 combined was evaluated on industrial slags and from samples obtained in a Peirce–Smith furnace, with increasing amounts of CaO in the flux.
Highlights
In most Chilean smelters, conversion Peirce–Smith Furnaces are loaded with high copper matte (70–75 wt % Cu) [1]
This fact explains the observed formation of solid phases during the conversion process and the reported ejection of materials from the furnace, the generation of slags with high viscosity that are difficult to remove from the furnace, and the buildup of accretions in the furnace [1]
The results showed that all the phases studied were homogeneous and that experiments performed for 3 h were enough to reach equilibrium
Summary
In most Chilean smelters, conversion Peirce–Smith Furnaces are loaded with high copper matte (70–75 wt % Cu) [1]. The process is carried out in a single stage and the generated slag is reported to contain a large proportion of solid phases and relatively high concentrations of copper The reported phase diagram indicates an appreciable reduction of the liquid area at temperatures below 1250 ◦ C and Cu2 O concentrations between 15 and 20 wt %. This fact explains the observed formation of solid phases during the conversion process and the reported ejection of materials from the furnace, the generation of slags with high viscosity that are difficult to remove from the furnace, and the buildup of accretions in the furnace [1]
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