Liquidus surface of FeO-Fe 2 O 3 -SiO 2 -CaO slag containing Al 2 O 3 , MgO, and Cu 2 O at intermediate oxygen partial p
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DUCTION
THE FeO-Fe2O3-SiO2-CaO system is of special importance in general extractive metallurgy. Many existing industrial slags such as the “fayalite” slag, calcium ferrite slag, acidic and basic steelmaking slags, as well as the newly proposed “ferrous calcium silicate slags” (FCS) are nominally based on this system. The liquidus surface of this system determines the operational windows of existing slags as well as the availability of new slags for more advanced technologies. Nevertheless, the liquidus surface of this system has been studied only in equilibrium with metallic iron or in air and the data at intermediate oxygen partial pressures are missing. However, most of the industrial processes are carried out at intermediate oxygen potentials and not at limiting conditions of iron saturation or in air. For instance, most of the classical copper smelting and converting processes, especially the new modern ones such as continuous converting or white metal production, are carried out at oxygen partial pressures varying from 10⫺8 to 10⫺6 atm. The liquidus surface of these slags, however, is not known at these oxygen potentials. Metallurgists seem to have ignored the difference in the oxygen potential and its influence on the slag liquidus surface and continue to use the liquidus surface of the aforementioned system at iron saturation (oxygen partial pressures from 10⫺11 to 10⫺12 atm) in both reductive and oxidative processes. This is believed to be the reason for the confusion that exists today in the FLORIAN KONGOLI, Senior Scientist and President, is with FLOGEN Technologies, WWW.FLOGEN.COM, 5757 Decelles Ave., Suite 511, Montreal, PQ, Canada H3S 2C3. E-mail: [email protected]. AKIRA YAZAWA, Emeritus Professor, is with Tohoku University, 16-32 Niizakamachi, Aoba-ku, Sendai, 981-0934, Japan. Manuscript submitted May 9, 2000. METALLURGICAL AND MATERIALS TRANSACTIONS B
literature and industrial practice about the problem of “magnetite” precipitation, which most of the time has been only empirically explained. Most of the industrial slags also contain different amounts of minor oxides, which are introduced through the mineral concentrates, fluxes, dissolved refractories, etc. These oxides significantly affect the liquidus surface of the FeO-Fe2O3SiO2-CaO system and the operational windows of the slags. Nevertheless, the effect of minor oxides on the liquidus surface of this system has not been studied at intermediate oxygen potentials, and more confusing conclusions are found in literature even for low oxygen potentials since the difference between the reductive and oxidative conditions is not taken into account. In previous work,[1,2,3] the liquidus surface of the CaOFeO-Fe2O3-SiO2-Al2O3-MgO system has been quantified along with the effect of CaO, Al2O3, and MgO as minor oxides at predominantly low oxygen potentials through a new type of representation of multicomponent phase diagrams.[1] The purpose of this work is to quantify for the first time the liquidus surface of CaO-FeO-Fe2O3-SiO2 slag containing Al2O3, Mg
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