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Modelling External Magnetic Fields of Magnetite Particles: From Micro- to Macro-Scale

1
School of Zijin Mine, Fuzhou University, Fuzhou 350116, China
2
Natural Magnetism Group, Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK
*
Author to whom correspondence should be addressed.
Geosciences 2019, 9(3), 133; https://doi.org/10.3390/geosciences9030133
Received: 10 December 2018 / Revised: 22 January 2019 / Accepted: 14 March 2019 / Published: 19 March 2019
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Abstract

We determine the role of particle shape in the type of magnetic extraction processes used in mining. We use a micromagnetic finite element method (FEM) to analyze the effect of external magnetic fields on the magnetic structures of sub-micron magnetite particles. In non-saturating fields, the magnetite particles contain multiple possible non-uniform magnetization states. The non-uniformity was found to gradually disappear with increasing applied field strength; at 100 mT the domain structure became near uniform; at 300 mT the magnetic structure saturates and the magnetization direction aligned with the field. In magnetic separation techniques, we suggest that 100 mT is the optimal field for magnetite to maximize the magnetic field with the lowest energy transfer; larger particles, i.e., >1 µm, will likely saturate in smaller fields than this. We also examined the effect of external magnetic fields on a much larger irregular particle (L × W × H = 179.5 × 113 × 103 μm) that was too large to be examined using micromagnetics. To do this we used COMSOL. The results show the relative difference between the magnitude of magnetic flux density of the particle and that of a corresponding sphere of the same volume is <5% when the distance to the particle geometry center is more than five times the sphere radius. The ideas developed in this paper have the potential to improve magnetic mineral extraction yield. View Full-Text
Keywords: micromagnetic modelling; mineral extraction; irregular shaped particle micromagnetic modelling; mineral extraction; irregular shaped particle
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Ku, J.; Valdez-Grijalva, M.A.; Deng, R.; Zuo, W.; Chen, Q.; Lin, H.; Muxworthy, A.R. Modelling External Magnetic Fields of Magnetite Particles: From Micro- to Macro-Scale. Geosciences 2019, 9, 133.

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