Kinetics of the Reduction of Hematite Concentrate Particles by Carbon Monoxide Relevant to a Novel Flash Ironmaking Proc
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A large number of alternate ironmaking technologies have been developed or are under development with the aim to replace the blast furnace for its high energy consumption and CO2 emissions. A large portion of these problems are due to the use of coke to start with and the needs of sintering, pelletization, and cokemaking steps associated with the blast furnace operation. A novel flash ironmaking process is under development at the University of Utah,[1–7] in which iron ore concentrate is flash reduced by gaseous reductants at temperatures above about 1473 K (1200 C). This flash
FENG CHEN, formerly a Visiting Ph.D Student with the Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112, is now a Ph.D Student in the School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, P.R.China. YOUSEF MOHASSAB, Research Associate, and HONG YONG SOHN, Professor, are with the Department of Metallurgical Engineering, University of Utah. Contact e-mail: [email protected] SHENGQIN ZHANG, a Visiting Professor with the Department of Metallurgical Engineering, University of Utah, is Assistant Professor with the School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331, P.R. China. Manuscript submitted March 10, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
ironmaking process eliminates sintering, pelletization, and cokemaking steps of the blast furnace and other ironmaking processes, making it more energy efficient and drastically lowering the emissions of environmental pollutants, especially carbon dioxide. Although hydrogen is the cleanest and most efficient reductant, other gaseous reductants can be used as well. Reformed natural gas and coal gas, which are mainly composed of CO and H2, are also possible reductants in this novel process. Previous research on gaseous reduction of iron oxide by carbon monoxide has typically involved samples larger than concentrate particles, such as ore fines, sinter, and pellets. Further, the temperature range tested was substantially lower than in the new flash ironmaking process. Ray and Kundu[8] determined that hematite reduction in CO-N2 mixtures had an activation energy of 90 kJ/mol in the temperature range of 1073 K to 1273 K (800 C to 1000 C) using powder samples in a TG/DTA instrument. Dutta and Ghosh[9] studied the reduction of ‘‘blue dust’’ (44 to 100 lm, 95.7 pct Fe2O3) by CO at 1073 K to 1373 K (800 C to 1100 C), and found that Ln kc (chemical rate constant) vs 1/T plots did not yield straight lines because of the structural changes during the reduction. Piotrowski et al.[10] reduced hematite particles of 91 lm average size to wustite by carbon monoxide at 973 K to 1173 K (700 C to
900 C). The nucleation and growth kinetic model was applied to the initial stages of the reduction process, which gradually shifted to diffusion control as reduction proceeded. They determined activation energy to be 58 kJ/mol. Hematite pellets of mean diameter 1.07 and 1.24 cm w
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