Phosphorus Migration During Direct Reduction of Coal Composite High-Phosphorus Iron Ore Pellets
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INTRODUCTION
IRON ores, raw materials commonly utilized in the iron and steel industry, are depleting rapidly worldwide. Of course, this poses a serious issue. China has begun to explore applications which involve high-phosphorus iron ores as a potential solution. There exists a wealth of high-phosphorus iron ore deposits in China, up to 7.45 billion tons distributed primarily in Hubei, Hunan, Yunnan, and Sichuan provinces.[1] As of now, because of the high temperature of blast furnace process, the P content can be increased to a great extent, and almost all P are absorbed by liquid iron; therefore, high P-bearing minerals are not suitable for the blast furnace process.[2,3] To this effect, it is urgently necessary to develop novel iron-making processes for high-phosphorus iron ores, in order to make the world’s iron ores more secure in future and assist long-term, stable development within the global iron and steel industry. Direct reduction is one of the most commonly utilized existing methods of high-phosphorus iron ore dephosphorization. In a relevant study, Matinde[4,5] treated a high-phosphorus iron ore by pre-reduction and screening combined with mechanical crushing or air jet milling. Yin et al.[6] proposed a reduction process combined with microwave and magnetic separation. Sun et al.[7] used the
CHENG CHENG, Master, QINGGUO XUE and JINGSONG WANG, Professors, and GUANG WANG and YUANYUAN ZHANG, Doctors, are with the State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China. Contact e-mail: [email protected] Manuscript submitted April 24, 2015. Article published online October 20, 2015. 154—VOLUME 47B, FEBRUARY 2016
process of direct reduction-magnetic separation to treat high-phosphorus iron ore in order to obtain direct reduction iron (DRI). Yu et al.[8] also employed coal-based direct reduction followed by magnetic separation technique to produce DRI from a high-phosphorus oolitic hematite, and investigated the effects of type and particle size of coal and C/O mole ratio on this process. Sasabe Minoru et al.[9] reduced iron ore containing higher concentration of phosphorus and removed 13 pct phosphorus using hydrogen gas containing water vapor. Li et al.[10] researched the mineralogical phase changes and structural changes of iron oxides and phosphorus-bearing minerals during the direct reduction roasting process. Our laboratory also proposed a direct reduction method assisted by rapid melting technology with rotary hearth furnace (RHF) process to obtain low-P nuggets, which can be directly used as raw material for steel-making. Generally speaking, scientists widely accept that direct reduction is highly efficient, and very effectively facilitates dephosphorization in high-phosphorus iron ores. That said, as of now, research on high-phosphorus iron ore direct reduction mechanisms focuses solely on raw ores.[11,12] Due to the complex nature of high-phosphorus iron ore chemical composition and the complicated interactive relationships between g
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