An Investigation of Carburization Behavior of Molten Iron for the Flash Ironmaking Process
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IN order to reduce the energy consumption and greenhouse gas carbon dioxide emissions during the ironmaking process, many alternating technologies, such as direct-reduced iron and smelting reduction, have been proposed.[1,2] A novel, high-intensity flash ironmaking process is now under development.[3–5] During this process, the iron ore concentrate is flash reduced by gaseous reductants at temperatures above 1423 K (1150 °C). The oxygen in the iron ore concentrate can be efficiently removed, and a higher purity iron is, therefore, obtained. Since the mass transfer of the carbon between the gaseous reduction and the iron ore
QIANG WANG and YONGXIANG YANG are with The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, 430081 Hubei, P.R. China, with the Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, and also with Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands. GUANGQIANG LI and WEI ZHANG are with The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, and also with the Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology. Contact emails: [email protected]; [email protected] Manuscript submitted December 10, 2018. Article published online May 17, 2019. 2006—VOLUME 50B, AUGUST 2019
concentrate is limited, the carbon content in the reduced iron is negligible. However, the favorable carbon content in the molten iron for the converter steelmaking ranges from 3 to 4 pct.[6,7] For achieving the appropriate carbon content, a carburizing process of the reduced iron is, thus, implemented by using a coke packed bed. The reduced iron is first melted and then travels through the coke packed bed, and is finally collected. To successfully control the carburizing process, it is essential to recognize the mechanism and kinetics of the dissolution of the coke into the molten iron. Various investigations about the iron carburization have been reported.[8–13] It has been generally considered that the dissolution of carbon from the carbonaceous materials is a two-step process. The first step includes the dissociation of carbon atoms from their crystal site in the carbonaceous materials into the carbon-melt interface. The second step is the mass transfer of carbon atoms through the adjacent boundary layer into the bulk of the molten iron. Furthermore, the second step, i.e., the diffusion of the carbon within the molten iron, has been shown to be the rate-limiting step, and a first-order kinetic equation was proposed to describe the mass transfer of the carbon. The type of the carbonaceous material also influences the carbon pickup of the molten iron. The dissolution of the carbon from the coke is proved to be much slower than that from the graphite. The reduction in the dissolution rate is attrib
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