Iron redox equilibria in CaO-Al2O3-SiO2 and MgO-CaO-Al2O3-SiO2 slags

Abstract

Measurements have been made of the ratio of ferric to ferrous iron in CaO-Al 2 O 3 -SiO 2 and MgO-CaO-Al 2 O 3 -SiO 2 slags at oxygen activities ranging from equilibrium with pCO 2 /pCO Ϸ 0.01 to as high as air at temperatures of 1573 to 1773 K. At 1773 K, values are given byfor melts with the molar ratio of CaO/SiO 2 ϭ 0.45 to 1.52, 10 to 15 mol pct Al 2 O 3 , up to 12 mol pct MgO (at CaO/SiO 2 Ϸ 1.5), and with 3 to 10 wt pct total Fe. Available evidence suggests that, to a good approximation, these redox equilibria are independent of temperature when expressed with respect to pCO 2 /pCO, probably from about 1573 to 1873 K. Limited studies have also been carried out on melts containing about 40 mol pct Al 2 O 3 , up to 12 mol pct MgO (at CaO/SiO 2 Ϸ 1.5), and 3.6 to 4.7 wt pct Fe. These show a strongly nonideal behavior for the iron redox equilibrium, with 0.37 3+ Fe pCO 2 ϰ ͑ ͒ 2+ Fe pCOThe nonideal behavior and the effects of basicity and Al 2 O 3 concentration on the redox equilibria are discussed in terms of the charge balance model of alumino-silicates and the published structural information from Mössbauer and NMR (Nuclear Magnetic Resonance) spectroscopy of quenched melts.

Magnesia-stabilised zirconia solid electrolyte assisted electrochemical investigation of iron ions in a SiO2–CaO–MgO–Al2O3molten slag at 1723 K

“…Therefore, not only the current of the reduction peaks (C2 and C3) but also the total charging current increases with the increase in FeO concentration in the slag. Previous investigations 19,20,50 on the redox equilibrium between Fe…”

Redox equilibria and kinetics of gas-slag reactions

“…These results the subject of numerous investigations in which the slag are in good agreement with results from other investigations of iron oxide-rich slags. [13][14][15][16][17][18][19] According to Yang, [18] there is insignificant dependence of Fe 3ϩ /Fe 2ϩ ratio on the iron Fig. 3-The equilibrium M nϩ /M (nϪ1)ϩ ratio for Ti, [22] V, [20,21] and Mn [20] Fig.…”

“…The data are for FeO x -CaO (29 to 32 pct) as pCO 2 /pCO, in comparison with iron-oxide slags. at 1300 ЊC, [8] FeO x -CaO-SiO 2 (CaO/SiO 2 ϭ 2) at 1450 ЊC, [18] FeO x -CaOSiO 2 -Al 2 O 3 (CaO/SiO 2 ϳ 1) at 1350 ЊC, FeO x -CaO-SiO 2 -Al 2 O 3 (CaO/SiO 2 ϳ 0.45, 7 pct FeO x ) at 1450 ЊC [17] and FeO x -SiO 2 (30 to 40 pct SiO 2 ) at 1350 ЊC. [9] The equilibrium Fe 3ϩ /Fe 2ϩ ratio in slags as a function of oxygen activity defined as pCO 2 /pCO, in low iron slags.…”

“…[9] The equilibrium Fe 3ϩ /Fe 2ϩ ratio in slags as a function of oxygen activity defined as pCO 2 /pCO, in low iron slags. [16,17] of Tranell, [23] titanium in the slag is mostly in the quadrivalent form, with the Ti 4ϩ /Ti 3ϩ ratio much higher than for iron oxide. The dependence of the redox on the oxygen activity for slags with CaO/SiO 2 ratios close to unity and at temperatures in the range of 1350 ЊC to 1500 ЊC.…”

“…The majority of expected from the entropy change for Reaction [1]. the work reviewed here was inspired, encouraged, or directed Recent studies by Xie, [16] Yang and Belton [17] and Yang [18] by Geoffrey Belton. have aimed at quantifying the dependence of the redox equilibrium ratio on the concentration of the transition metal oxide content of the slags. In Figure 2, experimental results…”