A study of the reduction rate of FeO in slag by solid carbon
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I.
INTRODUCTION
In view of new ironmaking concepts, iron could be produced by the smelting reduction of molten iron oxide by solid carbon and molten iron. This processing concept has the potential to utilize raw materials without pretreatments such as sintering or coking, which is why numerous smelting reduction processes have been developed.[1,2,3] The smelting reduction processes can be characterized as a reduction reaction of molten iron oxide in slag, which provides extensive interfacial area with various types of reductants.[1] It has been reported in previous literature that the smelting reduction rate of iron oxide dissolved in slag was controlled by the dissolved carbon in hot metal, the emulsified iron droplet, and the solid carbon.[1,2,3] From the analysis of an operating scale reactor, it revealed that the reaction rates at the slag/droplet and slag/carbon are equal to that of the metal/slag interface and increased with increasing FeO content and carbon in slag.[3,4] The kinetics of this reaction is one key point in understanding the productivity of the smelting reduction process. There have been numerous investigations on the reaction in question, but a review of current literature on the reduction rate and the mechanism of this reaction indicates that few conclusive studies have been carried out for FeO-containing slags.[5–11] Specifically, there is insufficient evidence on the kinetics of such reactions having wide concentration ranges of FeO in slag, which was considered to be one of D.J. MIN, Associate Professor, is with the Department of Metallurgical Engineering, Yonsei University, Seoul, Korea. J.W. HAN, Assistant Professor, is with the Department of Metallurgical Engineering, Inha University, Inchon, Korea. W.S. CHUNG, Assistant Professor, is with the Department of Metallurgical Engineering, Pusan National University, Pusan, Korea. Manuscript submitted December 16, 1996. METALLURGICAL AND MATERIALS TRANSACTIONS B
the most important factors in understanding the kinetics. The difficulty in containment and quantitative interpretation of experimental results involving the gas/liquid/solid phases provides some explanation for such a lack of investigation into the present topic at hand. The purpose of the present investigation is to understand the effects of FeO in slag on the kinetics and mechanism of this reaction. Those effects relevant to the present study will also be discussed. This article discusses the experimental results for the reaction of solid carbon with FeOcontaining slags of 1 to 70 wt pct. Fundamentals The overall reaction between carbon and iron oxide in slag can be expressed by Eq. [1]. FeOin
slag
1 C (s) 5 Fe (s) 1 CO (g)
[1]
where C (s) indicates a solid carbon such as coke or coal char in slag. In the steady state, the reaction proceeded with the gaseous intermediates between carbon and slag. This reaction meant that the overall reaction is a combination of the following sequential reactions at different interfaces:[12] (1) mass transfer of FeO to the gas/slag interface fr
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