Carbothermal reduction of zinc ferrite
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I. INTRODUCTION
In the present work, the reaction of zinc ferrite with carbon black powder in an inert gas stream is studied. An X-ray diffractometer (XRD) and a wet chemical analysis are used to determine the variations in the composition of the solid sample with time. A scanning electron microscope (SEM) and a surface area meter are employed to monitor the change in the structure of the sample during reaction. A thermogravimetrical analysis system (TGA) is used to determine the reaction rate. A reaction mechanism and a reaction model are developed to account for the experimental results. Effort is also made to examine the effects of the following factors on the rate of reaction between zinc ferrite and carbon: argon flow rate, sample height, temperature, molar ratio of ZnFe2O4/C, size of carbon agglomerate, and initial bulk density. This study may help enhance the understanding of the reaction system.
ELECTRIC arc furnace (EAF) dust is produced during the steelmaking process. Toxic metals such as zinc, lead, cadmium, and nickel are present in the dust. These toxic materials are leached out by rain; they pollute both ground and underground water if the EAF dust is dumped into a landfill. Hence, the treatment of EAF dust emerges from the viewpoint of environmental protection. There are four technologies that can be applied to treat the dust:[1] (1) hydrometallurgical methods involving acidic or basic leaching,[2] (2) stabilizing techniques using cement and other additives,[3] (3) glassification,[4] and (4) pyrometallurgical treatment methods.[2] Acids or bases used in the hydrometallurgical method may pollute water. Stabilization and glassification are not only costly but also not environmentally friendly. Carbothermal reductions are the main reactions in the pyrometallurgical treatment methods. Zinc and lead can be recovered by this method. On the other hand, the byproduct, slag, can be used as construction material. Hence, pyrometallurgical treatment is the major method used in Taiwan.[1] Many reports on the carbothermal reduction of EAF dust or related topics are available and include the reduction of pure zinc oxide with carbon,[5–9] the reduction of pure lead oxide with carbon,[10] the reduction of zinc oxide with iron,[11] the reduction of EAF dust with coal, graphite, charcoal, or carbon monoxide,[12–16] and the reduction of EAF dust with iron.[17] The zinc content in EAF dust is about 20 pct,[1] while zinc in the form of zinc ferrite is approximately 20 to 50 pct, with the remainder being zinc oxide.[17] Hence, carbothermal reductions of zinc ferrite and zinc oxide occur simultaneously during the process of the reduction of the dust. Unfortunately, literature on the carbothermal reduction of zinc ferrite cannot be found except in the work of Kim and Han.[18]
A. Materials
JYH-JEN LEE, Graduate Student, and CHUN-I LIN, Professor, are with the Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 106. HSI-KUEI CHEN, Associate Professor, is with the Departm
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