Growth Characteristics of Metallic Iron Particles in the Direct Reduction of Nickel Slag
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INTRODUCTION
THE use of direct reduction iron in ironmaking helps to reduce its dependence on coal resources, cut down energy consumption, and improve the quality of steel products. The raw material for producing direct reduction iron may be various iron-containing resources. With the growing shortage of high-grade resources and the increase of secondary iron resources, using coalbased reduction–magnetic separation process to produce metallic iron from low-grade complex ore[1,2] or smelting slag is of great importance. It is an effective measure to make up for ironmaking raw materials, effectively utilize secondary resources, and solve environmental problems.[3,4]
XIAOMING LI and XIANGDONG XING are with the School of Metallurgical Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, P.R. China and also with the Research Center of Metallurgical Engineering and Technology of Shaanxi, Xi’an University of Architecture and Technology, Xi’an 710055, P.R. China. Contact e-mails: [email protected], [email protected] YI LI, XINYI ZHANG, and ZHENYU WEN are with the School of Metallurgical Engineering, Xi’an University of Architecture and Technology. Manuscript submitted June 3, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
As solid waste is produced by nickel smelting industries,[5] nickel slag contains large amounts of recoverable and valuable metals. When dumped in open air, it not only occupies vast areas of land, but also pollutes the surrounding environment. There is a growing concern over the utilization of nickel slag. Based on the direct reduction–magnetic separation technology, the recovery of valuable elements from nickel slag is not only a requirement for secondary resource utilization, but also has environmental, economic, and social benefits. Wang et al.[6,7] studied the effects of additives and base on the deep reduction recovery rate of nickel slag pellets. Gao et al.[8,9] investigated the formation and growth behavior of metallic iron particles during the direct reduction of refractory iron ore. Pan et al.[10] researched the effect of time, temperature, and amount of coal on magnetic separation and reduction of nickel slag. Kinetic studies on nickel slag by Guo et al.[11] and thermodynamics on laterite ore by Luo et al.[12] showed that the size of metallic iron particles varies greatly in the reduction process in which the larger the particle size, the easier it is to separate it from the slag and the better the magnetic separation effect. Therefore, the key to achieving more effective reduction and increasing the recovery rate of magnetic separation is to conduct in-depth research on
Table I.
Chemical Components of Nickel Slag (Mass Percent)
TFe
FeO
SiO2
MgO
CaO
Ni
Cu
Co
S
39.40
49.68
32.50
9.70
1.20
0.455
0.338
0.144
0.868
the formation of iron grains, the aggregation and growth mechanism of iron particles, and the process control during the direct reduction of nickel slag. Through high-temperature reduction experiments, the paper studies the effects of reduction
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