Effect of water vapour content in H 2 –H 2 O–CO– CO 2 mixtures on activity of iron oxide in slags relevant to novel flash ironmaking technology M. Yousef Mohassab-Ahmed* and H. Y. Sohn As an integral part of developing a novel flash ironmaking technology at the University of Utah, the activity of iron oxide in the slag was studied under three different gas atmospheres: H 2 /H 2 O (H 2 ), CO/CO 2 /H 2 /H 2 O (reformed natural/coal gas), and CO/CO 2 . The conditions of the slags investigated were MgO-saturated CaO–FeO–Al 2 O 3 –SiO 2 –MnO (0?2–0?8 wt-%)–P 2 O 5 (0?1–0?9 wt-%) in the temperature range 1550–1600uC with wt-% CaO/wt-% SiO 2 of 0?8 to 1?2, and under pO 2 52610 210 –2610 29 atm. Water increased the activity coefficient of FeO in the slag and accordingly lowered the FeO content. The average FeO content was found to be 10, 11 and 16 wt- % under H 2 /H 2 O (H 2 ), CO/CO 2 /H 2 /H 2 O (reformed natural/coal gas), and CO/CO 2 , respectively. An empirical correlation for c FeO in slags under H 2 /H 2 O atmospheres was formulated to give log c FeO 523?0623 X FeO 23?1421 X CaO 22?5068 X MgO z2?1957 Keywords: Green ironmaking, Flash process, Slag, Iron oxide Introduction Iron oxide plays an important role in metal–slag reactions including those involved in sulphur and phosphorus distribution. In addition, FeO in the slag is considered as a loss in ironmaking and steelmaking processes. Moreover, FeO content in the slag affects its viscosity, corrosivity, and redox potential of the slag. 1 Thus, FeO activity (a FeO ) in slag and the related thermodynamics attracted the attention of many researchers. 2–6 The present work is an integral part of a research project that aims to develop a novel green ironmaking process based on the direct gaseous reduc- tion of iron oxide fine concentrate in a flash process. The ultimate goal of this new process is to significantly reduce CO 2 emissions, energy consumption, and envir- onmental pollution in the steel industry. 7 Hydrogen, natural gas and coal gas are the proposed reducing agents in that new process. To date, only a few studies have been performed to measure FeO activities under gas atmospheres containing H 2 O and H 2 . 8–10 Thus, as part of the development of this new green ironmaking project, there was a need to investigate thoroughly the behaviour of FeO in H 2 /H 2 O and CO/CO 2 /H 2 /H 2 O atmospheres, corresponding to an oxygen partial pressure (pO 2 ) range of 10 210 –10 29 atm. In addition, the activity of FeO under CO/CO 2 was investigated for comparison. The major slag components were CaO, MgO, SiO 2 , Al 2 O 3 and FeO. The FeO activity coefficient was studied in the temperature range 1550–1650uC encompassing the expected operating temperatures in the proposed process. There are two main methods to determine FeO activity. The first method is the thermodynamic relation- ships and EMF (electromotive force) measurements. In this method, FeO activity is measured using an oxygen sensor and thermodynamic relationship between Fe (l) – FeO (slag) expressed as follows 11 Fe (l) z 1 2 O 2(g) ~FeO (l) , DG 0 FeO ~{225 460z41:26 T (J mol {1 ) (1) Using the EMF reading from an oxygen sensor, the equilibrium pO 2 can be calculated by the Nernst equation. 12 This technique was adopted by Liu et al., 12,13 Ogura et al., 14 Iwase et al., 15 and Hamm et al. 16 The second method is the thermodynamic equilibrium technique with chemical analysis. This technique is the most common one used to measure a FeO in which the slag sample is equilibrated with liquid iron or solid iron at a fixed temperature and under a stable atmosphere. In this technique, different principles could be employed to calculate the FeO or Fe t O activity in the slags. These principles are listed as follows. Slag–metal equilibrium technique This technique is based on the following reactions Fe (l) z O~FeO (slag) (2) Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT, USA *Corresponding author, email materials4ever@gmail.com ß 2014 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute Received 12 November 2013; accepted 9 January 2014 DOI 10.1179/1743281214Y.0000000180 Ironmaking and Steelmaking 2014 VOL 41 NO 9 665