Copper concentrates and fluxes can contain variable levels of SiO 2 , 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-Fe 2 O 3 -SiO 2 -CaO-MgO-Al 2 O 3 system at oxygen partial pressure of 10 À8 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 2 ), wt pctCaO, wt pctMgO, and wt pctAl 2 O 3 . The positions of each of the liquidus points (wt pctFe)/(wt pctSiO 2 ) at a fixed temperatures in the tridymite primary phase field were expressed as linear functions of wt pctCaO, wt pctMgO, and wt pctAl 2 O 3 .

The cost of maintaining and eventually replacing refractories as a result of slag attack is a significant cost component in the copper industry. Converting matte to blister copper takes place in reactors lined with direct-bonded magnesia-chrome refractories, and several continuous converting operations use calcium ferrite slag. Unfortunately, the low viscosity of calcium ferrite slag makes it aggressive toward the refractories. Ferrous calcium silicate (FCS) slag has been proposed as a replacement; however, the effect of this slag on magnesia-chrome refractories has not been studied. In this work, the interactions between FCS slag and magnesia-chrome refractory at 1573 K (1300°C) with an oxygen partial pressure of 10 À6 atm were studied and compared with that experienced with calcium ferrite slag under the same conditions. Both slags penetrated the pores in the refractory and caused compositional change in the chromite spinel intergranular bonding phase through cation interdiffusion, which resulted in cracking and debonding of periclase grains. It was observed that the refractory was penetrated much more deeply by calcium ferrite slag than FCS slag because of the higher surface tension and lower viscosity of calcium ferrite slag. As a result, the refractory was attacked less by FCS slag than it was by calcium ferrite slag. It is concluded that the use of FCS slag in continuous copper converting is likely to extend refractory life.

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Molten slag foams can be considered very dynamic (non-equilibrium) systems, hence their behaviour in industrial processes can be difficult to predict and control. This paper reviews the role of physicochemical properties of molten slags, and the types of stability mechanisms likely to be operating in slag foams. The emphasis of the review relates to slag foams produced under low superficial gas velocities (such as in an electric arc furnace). Here, the 'lifetime' of bubble films in the top layer can be considered the rate limiting step for coalescence and collapse of the foam in a metallurgical reactor.

Ferrous calcium silicate (FCS) slag has been proposed as a suitable slag system for continuous copper converting. However, there is little information on the important properties of FCS slag and this must be addressed before such a slag can be properly evaluated for implementation. In this work the slag/metal distribution ratios of lead, antimony and nickel between FCS slag and copper were measured at 1300uC and an oxygen partial pressure of 10 26 atmosphere. They were found to have values of 0?93, 0?54 and 0?98 respectively. These distribution ratios were compared to reported values for calcium ferrite slag and iron silicate slags, both currently used for continuous copper converting, and predicted values for FCS slag under the same conditions. Ferrous calcium silicate slag was found to be a little more than twice as good as calcium ferrite slag at absorbing lead oxide but very similar in its ability to absorb antimony and nickel oxides. However, it was almost five times poorer than iron silicate slag for absorbing lead oxide, a little poorer for nickel oxide but almost four times better for antimony oxide. The activity coefficients of NiO, PbO and SbO 1?5 in FCS slag were also calculated and found to be 4?5, 1?4 and 0?6 respectively. In terms of minor element distribution behaviour only, it is concluded that FCS slag warrants closer examination as a replacement for calcium ferrite and iron silicate slags in continuous copper converting.