Thermal Analysis Study on the Carbothermic Reduction of Chromite Ore with the Addition of Mill Scale

• Published in: Steel research international Vol. 87; no. 5; pp. 562 - 570
• Main Authors: Hu, Xianfeng, Yang, Qixing, Sundqvist Ökvist, Lena, Björkman, Bo
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01.05.2016; Wiley Subscription Services, Inc
• Subjects: Alloying; Alloying additive; Argon atmospheres; Carbon; Carbothermal reduction; Carbothermic reactions; carbothermic reduction; Chemical industry; Chromite; Chromite deposits; chromite ore; Chromite ores; Chromium; Chromium alloying; Chromium ores; Coke; direct alloying; Fundamental studies; Iron ore reduction; Non-isothermal condition; Ore analysis; Ore reduction; Ores; Process Metallurgy; Processmetallurgi; Reduction; Scale (corrosion); Temperature; Thermo-gravimetric; Thermoanalysis; Thermodynamic activity; Thermogenesis; thermogravimetric analysis
• ISSN: 1611-3683; 1869-344X; 1869-344X
• DOI: 10.1002/srin.201500131

This paper presents a fundamental study on the carbothermic reduction of chromite ore with the addition of mill scale, which forms the basis for designing an alloying precursor, “chromite ore + mill scale + carbon,” for direct chromium alloying. The reduction of chromite ore by petroleum coke with or without the addition of mill scale is investigated by Thermogravimetric Analysis (TGA) under non‐isothermal conditions (from room temperature to 1823 K) in the argon atmosphere; the fractional reduced samples were characterized by SEM/EDS and XRD analyses. The experimental results show that the mill scale in the alloying mixture is reduced to high active iron first and disseminated around the chromite ore particles; the reduction of chromite ore is enhanced with the addition of mill scale especially at temperatures higher than 1623 K, and the enhancing effect increased with increasing mill scale addition. The enhancing effect is attributed to the presence of molten Fe–C alloy in the vicinity of chromite ore, which can decrease the thermodynamic activity of chromium by having chromium in situ dissolve into the melt. In this paper, the effect of mill scale addition on the reduction of chromite ore is investigated on the samples with three different amounts of mill scale addition (78 wt%, 38 wt%, and 0 for the samples #1b, #2b, and #3b, respectively) by thermogravimetric technique. The fractional reduced samples are characterized by SEM/EDS and XRD analyses. The mechanism of mill scale addition on the reduction of chromite ore is discussed and the industrial implications of the experimental results are also presented.