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Field Applications
Published in Ahmad Shahid Khan, Saurabh Kumar Mukerji, Electromagnetic Fields, 2020
Ahmad Shahid Khan, Saurabh Kumar Mukerji
Magnetic separation is a process in which magnetically susceptible material is extracted from a mixture using a magnetic force. This technique is useful in mining iron as it is attracted to a magnet. It is also used in electromagnetic cranes that separate magnetic material from scraps. Magnetic separators that used permanent magnets generate fields of low intensity only. High-intensity magnetic separators which employ electromagnets are found more effective in the collection of very fine paramagnetic particles
Magnetic Separation
Published in S. Komar Kawatra, Advanced Coal Preparation and Beyond, 2020
High-intensity magnetic separators, particularly those using powerful superconducting magnets, have tremendous potential for use directly following coal pulverizers at electrical utility companies. These separators can remove pyrite from the coal while it is entrained in the air stream, allowing the coal sulfur content to be reduced without introducing additional complexities such as dewatering.
Pre-treatment, Concentration, and Enrichment of Precious Metals from Urban Mine Resources
Published in Sadia Ilyas, Hyunjung Kim, Rajiv Ranjan Srivastava, Sustainable Urban Mining of Precious Metals, 2021
Hyunjung Kim, Sadia Ilyas, Rajiv Ranjan Srivastava
Materials are classified into two broad groups according to whether they are attracted or repelled by a magnet. Non-/diamagnetics are repelled from and ferromagnetics/paramagnetics are attracted to a magnet. Ferromagnetic substances are strongly magnetic and have a large and positive magnetism. The magnetic moments in ferromagnetic material are ordered and are of the same magnitude in the absence of an applied magnetic field. Paramagnetic substances are weakly magnetic and have a small and positive magnetism. The magnetic moments in a paramagnetic material are disordered in the absence of an applied magnetic field and ordered in the presence of an applied magnetic field. In diamagnetic materials, a magnetic field is opposite to the applied field. Magnetisms are small and negative. Nonmagnetic material has zero magnetism. These materials are not attracted to a magnet. Ferromagnetism is the basic mechanism by which certain materials (such as Fe) form permanent magnets or are attracted to magnets. Ferromagnetism (including ferrimagnetism) is the strongest type. Ferromagnetic materials can be separated by a low-intensity magnetic separator at lower than 2T magnetic intensity. Paramagnetic materials can be separated by dry or wet high-intensity magnetic separators at 10–20 T magnetic intensities. Diamagnetic materials create an induced magnetic field in a direction opposite to an externally applied magnetic field and are repelled by the applied magnetic field. Nonmagnetic substances have little reaction to magnetic fields and show net zero magnetic moment due to random alignment of the magnetic field of individual atoms. Strongly magnetic materials can be recovered by a magnetic separator with the use of relatively weak magnetic induction, up to 0.15 T (1,500 Gauss). Weakly magnetic materials can be recovered by a high-intensity magnetic separator generating induction up to 0.8T(8,000 Gauss) with modest values for the gradient of the magnetic field. Induced roll separators with field intensities up to 2.2 T and Perm roll separators can be used for both coarse and dry materials (>75 μm). Fine materials reduce separation efficiency due to particle–rotor and particle–particle adhesion/ agglomeration. For wet high-intensity magnetic separators, Gill and Jones separators are used at a maximum field of 1.4 and 1.5 T, respectively, at -150 μm size (Bentli et al., 2017).
Beneficiation Strategies for Removal of Silica and Alumina from Low-Grade Hematite-Goethite Iron Ores
Published in Mineral Processing and Extractive Metallurgy Review, 2022
V. Nunna, S. P. Suthers, M. I. Pownceby, G. J. Sparrow
To beneficiate ores that contain minerals with strong magnetic properties (e.g. magnetite and maghemite), wet low-intensity magnetic drum separators (drum LIMS) are usually used. This may be achieved with several stages of separation, or the drum may be used in combination with flotation as shown in flowsheets given by Xiong, Lu and Holmes (2015). The development of wet high-intensity magnetic separators (WHIMS) and wet high-gradient magnetic separators (HGMS), with a matrix in a ring of magnets (Jones 1960; Yang et al. 2018), have enabled iron minerals and admixtures that were considered too fine and too weakly magnetic (e.g. hematite, goethite, siderite, and limonite) to be separated from gangue minerals such as aluminum silicates, quartz, ferruginous clay, and shale that are predominantly non-magnetic in nature. Jena et al. (2015) used hydrocyclones and WHIMS to beneficiate hematite-goethite iron ore slimes containing quartz, kaolinite and gibbsite as gangue minerals. From slimes assaying 57.1 wt% Fe, 5.2 wt% SiO2, 6.3 wt% Al2O3, and 6.3 wt% LOI, a concentrate of 62.5 wt% Fe, 2.3 wt% SiO2, 3.4 wt% Al2O3, and 4.4 wt% LOI was obtained with an iron recovery of 79% and rejection of 68% of the silica and 65% of the alumina.
Beneficiation of Low-grade Iron Ore Fines by Using a Circulating-type Air Classifier
Published in Mineral Processing and Extractive Metallurgy Review, 2019
Venkata Nunna, Sarath Hapugoda, Sreedhar Gaekwad Eswarappa, Shiva Kumar Raparla, Rajan Kumar, Narendra Kumar Nanda
To assess the effective method of dry separation using circulating-type air classifier, present study of low-grade iron ore fines helped and the test work showed that there was a marginal improvement in the iron grade at the feed size tested (Table 9). Further, mineralogy study indicated that there is a possibility of separation of difficult to beneficiate weathered ochreous goethite iron minerals and liberated clayey minerals into fines product. With the removal of ultrafine size, the coarse size product will enhance the downstream dry magnetic separation efficiency (Jang et al. 2014; Tripathy et al. 2016). Application of dry magnetic separation such as induced roll high-intensity magnetic separator (IRMS) requires coarse (>45 µm) size product. So further study using combination downstream beneficiation options using circulating-type air classifier with reduction roasting followed by dry magnetic separation/electrostatic separation/finer grind sizes to liberate iron minerals and recover on the coarse product is recommended for future work.
Formation of pyrite in the process of fine coal desulfurization by microwave enhanced magnetic separation
Published in International Journal of Coal Preparation and Utilization, 2023
Zhenxing Zhang, Xinyu Wei, Guanghui Yan, Junwei Guo, Pengfei Zhao, Fan Yang, Hongyu Zhao, Bo Zhang
A DVMF 50–4 dry-type high gradient high-intensity magnetic separator (ERIZE company, USA) was selected for this test. The equipment of dry-type high-gradient magnetic separator includes a control cabinet, an electromagnetic coil, a blanking pipe, a magnetic medium, a material distribution device, an air supply device, a vibration system, and a cooling system. The equipment controls the operation of the instrument through the control cabinet, displaying the magnetic field strength, vibration intensity, output current, and output voltage.