Liquidus temperatures of ferro-nickel smelting slags

The reduction smelting of nickel laterites produces slag, consisting principally of the chemical components MgO, "FeO", SiO2, and Al2O3, and ferro-nickel alloy. Despite the fact that the phase equilibria for the ternary MgO-"FeO"-SiO2 up to 1500 C is well established limited experimental data are available in the MgO-"FeO"-SiO2-Al2O3 system, which is relevant to commercial operation of the process. A methodology has been developed for the experimental investigation of the liquidus temperatures for the multi-component system MgO-"FeO"-SiO2Al2O3-Cr2O3 in equilibrium with metallic iron. Experiments have been carried out using high temperature equilibration, quenching, followed by electron probe X-ray microanalysis (EPMA). Liquidus temperatures have been determined in the silica primary phase field in the composition ranges directly, relevant to the Cerro Matoso S.A. ferro-nickel smelting slag. Liquidus isotherms have been-determined for temperatures between 1450 to 1600degreesC. The study enables the liquidus to be described for a range of MgO/FeO ratios. It was found that liquidus temperatures in the silica primary phase field decrease significantly with the addition of Al2O3.