Reaction mechanism on the smelting reduction of iron ore by solid carbon
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INTRODUCTION
FOR the past 100 years, blast furnaces have played a major part in producing pig iron because of their high heat efficiency, mass production, and high degree of gas utilization. However, the present coke oven-blast furnace process has some inevitable problems, such as environmental pollution by the coke plant, lower production flexibility, and pretreating of raw materials. To cope with these problems, several new processes called ‘‘smelting reduction processes’’ are being developed in some industrialized countries, which can use coal and ultimately pulverized ore instead of coke and lumpy ore. They also may have a higher productivity per unit volume than a blast furnace, and the capital cost seems to be significantly lower than the current process.[1,2] Until now, the corex process was the most fully developed process, producing 300,000 tons of pig iron annually without any problems. In this process, coal is charged into the melter-gasifier and is combusted to CO and H2 to produce the heat to melt the iron pellets. Then the off-gas is used to reduce iron ore to more than 90 pct metalization in the shaft-type prereduce.[3] Recently, however, the bath smelting process has gained more attention and is thought to be more economical. This process uses in-bath smelting and partial postcombustion of CO and H2. These gases are postcombusted above the bath with oxygen or air, and the heat from postcombustion is transferred back to the bath. The partially oxidized off-gas is used for the preheating and prereduction of iron ore. In the bath smelter, the next three reduction reactions are considered to be possible reactions between slag and carbon in slag, slag and carbon in Fe-C JAE-CHEOL LEE, is Senior Researcher with the Process Metallurgy Research Team, Research Institute of Industrial Science and Technology, Pohang 790-600, Korea. DONG-JOON MIN, Professor, is with the Department of Metallurgical Engineering, Yonsei University, Seoul 120-749, Korea. SUNG-SOO KIM, Professor, is with the Department of Metallurgical Engineering, Yeungnam University, Kyung Pook 713-749, Korea. Manuscript submitted August 30, 1995. METALLURGICAL AND MATERIALS TRANSACTIONS B
droplet, FeO and carbon in the Fe-C bath. Much research on bath smelting has been carried out, including that by Fruehan.[4] The lab-scale fundamental research on the smelting reduction of iron ore was started first by Dancy in 195.[5] Since then, research has been conducted primarily in Japan and Russia, but most of this research concerned with the reduction of molten slag containing low FeO concentration,[6–9] has been and relatively little work at the high FeO concentration range has been done to present.[10,11] Therefore, it cannot be said that the mechanism of the smelting reduction of iron ore is fully understood. Considering the practical importance of the smelting reduction technology as a next generation direct ironmaking process, more research is needed. In the present study, the kinetics of the smelting reduction of iron ore by carbon in the gra
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