3 - Phase Equilibria in Ferrous Calcium Silicate Slags:...

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Phase Equilibria in Ferrous Calcium Silicate Slags: Part I. Intermediate Oxygen Partial Pressures in the Temperature Range 1200 ° C to 1350 ° C STANKO NIKOLIC, PETER C. HAYES, and EVGUENI JAK Ferrous calcium silicate slags are used in primary and secondary metallurgical processes (described by the FeO-Fe 2 O 3 -CaO-SiO 2 system). Despite the industrial and scientifc impor- tance o± this system, the phase equilibria have not been ±ully investigated. Characterization o± this slag system is necessary to improve the design and optimization o± new and existing met- allurgical processes, particularly in relation to fluxing practice and operating temperatures. Experimental methods have been developed to investigate the phase equilibria o± these slags involving the equilibration o± samples at fxed oxygen partial pressures, rapid quenching, and the analysis o± the compositions o± solid and liquid phases using electron probe X-ray micro- analysis (EPMA) with wavelength dispersive detectors. Liquidus and solidus data are reported ±or the primary phase felds o± spinel, pseudo-wollastonite, and tridymite in the temperature range o± 1200 ° C to 1350 ° C at an oxygen partial pressure o± 10 - 6 atm, and at 1250 ° Ca tan oxygen partial pressure o± 10 - 5 atm. The resulting data have been used to construct liquidus and solidus isotherms in the ‘‘FeO’’-CaO-SiO 2 system directly relevant to industrial processes. DOI: 10.1007/s11663-008-9130-1 Ó The Minerals, Metals & Materials Society and ASM International 2008 I. INTRODUCTION F ERROUS calcium silicate slags, described by the FeO-Fe 2 O 3 -CaO-SiO 2 system, ±orm the basis ±or a number o± metallurgical slag systems used in non±errous smelting. Despite the industrial importance o± the phase equilibria o± this system, the conditions relevant to industrial processes have not been ±ully investigated. The phase relations at intermediate oxygen partial pressures, relevant to such processes as copper convert- ing, are o± particular interest. Characterization o± this slag system at these conditions is necessary to ±acilitate improvements in the design, development, and optimi- zation o± process conditions ±or existing and new metallurgical processes, such as the ISACONVERT* process. [ 1 , 2 ] The phase equilibria o± the FeO-Fe 2 O 3 -CaO-SiO 2 system has been investigated experimentally in air [ 3 , 4 ] and at iron saturation. [ 5 8 ] Timucin and Morris [ 9 ] defned the liquidus and oxygen isobars in the liquid phase in the FeO-Fe 2 O 3 -CaO-SiO 2 system at fxed oxygen partial pressures by chemically analyzing the composition o± liquid samples equilibrated at varying oxygen partial pressures in the range o± 1 atm o± oxygen to iron saturation, including the Fe 2+ /Fe 3+ ratio o± the slag, with silica concentrations o± 0, 5, 10, 20, and 30wt pct at 1450 ° C and 1550 ° C. Shigaki et al.
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This note was uploaded on 05/13/2011 for the course METALLURGY 1107 taught by Professor Hegurange during the Three '10 term at Murdoch.

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3 - Phase Equilibria in Ferrous Calcium Silicate Slags:...

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