Investigation of Liquidus Temperatures and Phase Equilibria of Copper Smelting Slags in the FeO-Fe2O3-SiO2-CaO-MgO-Al2O3 System at PO2 10 -8 atm

Copper concentrates and fluxes can contain variable levels of SiO , CaO, and MgO in addition to main components Cu, Fe, and S. Metal recovery, slag tapping, and furnace wall integrity all are dependent on phase equilibria and other properties of the phases and are functions of slag composition and operational temperature. Optimal control of the slag chemistry in the copper smelting, therefore, is essential for high recovery and productivity; this, in turn, requires detailed knowledge of the slag phase equilibria. The present work provides new phase equilibrium experimental data in the FeO-FeO-SiO-CaO-MgO-Al O system at oxygen partial pressure of 10 atm within the range of temperatures and compositions directly relevant to copper smelting. For the range of conditions relevant to the Kennecott Utah Copper (South Magna, UT) smelting furnace, it was confirmed experimentally that increasing concentrations of MgO or CaO resulted in significant decreases of the tridymite liquidus temperature and in changes in the position of the tridymite liquidus in the direction of higher silica concentration; in contrast, the spinel liquidus temperatures increase significantly with the increase of MgO or CaO. Olivine and clinopyroxene precipitates appeared at high MgO concentrations in the liquid slag. The liquidus temperature in the spinel primary phase field was expressed as a linear function of 1/(wt pctFe/wt pctSiO), wt pctCaO, wt pctMgO, and wt pctAlO. The positions of each of the liquidus points (wt pctFe)/(wt pctSiO) at a fixed temperatures in the tridymite primary phase field were expressed as linear functions of wt pctCaO, wt pctMgO, and wt pctAlO

Phase equilibria in the system Fe-Zn-O at intermediate conditions between metallic-iron saturation and air

The phase equilibria in the FeO-Fe2O3-ZnO system have been experimentally investigated at oxygen partial pressures between metallic iron saturation and air using a specially developed quenching technique, followed by electron probe X-ray microanalysis (EPMA) and then wet chemistry for determination of ferrous and ferric iron concentrations. Gas mixtures of H-2, N-2, and CO2 or CO and CO2 controlled the atmosphere in the furnace. The determined metal cation ratios in phases at equilibrium were used for the construction of the 1200 degrees C isothermal section of the Fe-Zn-O system. The univariant equilibria between the gas phase, spinel, wustite, and zincite was found to be close to pO(2) = 1 center dot 10(-8) atm at 1200 degrees C. The ferric and ferrous iron concentrations in zincite and spinel at equilibrium were also determined at temperatures from 1200 degrees C to 1400 degrees C at pO(2) = 1 center dot 10(-6) atm and at 1200 degrees C at pO(2) values ranging from 1 center dot 10(-4) to 1 center dot 10(-8) atm. Implications of the phase equilibria in the Fe-Zn-O system for the formation of the platelike zincite, especially important for the Imperial Smelting Process (ISP), are discussed

Experimental liquidus in the PbO-ZnO-"Fe2O3"-(CaO+SiO2) system in air, with CaO/SiO2=0.35 and PbO/(CaO+SiO2)=3.2

Experimental studies on phase equilibria in the multicomponent system PbO-ZnO-CaO-SiO2-FeO-Fe2O3 in air have been conducted to characterize the phase relations of a complex slag system used in lead and zinc smelting. The liquidus in the pseudoternary section ZnO-"Fe2O3"-(PbO + CaO + SiO2) with a CaO/SiO2 weight ratio of 0.35 and a PbO/(CaO + SiO2) weight ratio of 3.2 has been constructed to describe liquidus temperatures as a function of composition in the range of commercial operating conditions employed by the Lead Isasmelt smelting process. The section contains the primary phase fields of spinel (zinc ferrite, ZnxFe3-xO4+z), zincite (ZnuFe1-uO), melilite (PbvCa2-vZnwFe1-wSi2O7), hematite (Fe2O3), magnetoplumbite (PbFe10O16), and wollastonite (CaSiO3)