Reduction Mechanism of Iron Oxide Briquettes by Carbonaceous Materials Extracted from Blast Furnace Dust
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INTRODUCTION
BLAST furnace (BF) dust is the by-product of BF ironmaking process, with a production of about 15 to 50 kg tHM1 (kilogram per ton of hot metal). With the large requirements of iron, such amount of BF dust will cause severe environmental hazards if proper treatments are absent.[1–4] Many steel mills nowadays return the BF dust to the BF, and the harmful volatile elements are recycled in the BF process, thus causing negative impact to the blast furnace production and steel quality. BF dust generally contains a certain amount of carbon.[5] In order to make full use of the carbon element in the BF dust, the BF dust is generally selected to be a briquette containing carbon. The reducing agent particles in the briquette are in close contact with the iron-containing mineral particles, have a good kinetic conditions for reduction, and have a fast reduction rate.[6,7]
YANG LI, ZHENGJIAN LIU, GUILIN WANG, SHIQIN LI, and RONGRONG WANG are with the University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, P.R. China. Contact e-mail: [email protected] JIANLIANG ZHANG is with the University of Science and Technology Beijing and also with the School of Chemical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia. Manuscript submitted November 8, 2018. Article published online June 19, 2019. 2296—VOLUME 50B, OCTOBER 2019
Scholars have done various research on BF dust and its carbon element, and there are also some studies on reduction of the pellet containing carbon.[8–11] Zhang et al.[12] have carried out the analysis of the basic properties about metallurgical dust chemical composition and microstructure. By studying the process parameter characteristics of metallurgical dust, their result provided a reference for the selection of metallurgical dust treatment process. Mihaiescu et al.[13] used the optical microscopy to reveal the morphology of BF dust, such characterization provided useful information of dust recycling. Gupta et al.[14] used X-ray diffraction (XRD) and chemical analysis to study the carbon structure (L002) of coke in high temperature-treated coke and BF dust, and thus determined the initial temperature of coke particles in the blast furnace. Wu et al.[15] identified different carbonaceous materials in BF dust using XRD and microstructure analysis. They determined the source of carbonaceous material in BF dust, and then determined the reasonable pulverized coal injection (PCI) rate of the BF. BF dust contains many carbon element, so the utilization of BF dust-iron ore composite pellets can reduce coal consumption. However, the research on the reducibility and reduction mechanism of carbonaceous materials in iron oxide briquettes extracted from BF dust is insufficient. This research aims to fill the knowledge gap by extracting carbonaceous materials from two kinds of BF dust and comparing them with coal. First, the methodology involves studying the microstructure by SEM and XRD. The reduction reactivity of carbonaceous
METALLURGICAL AND M
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