Magnetic Separation Experiments Research Articles

Effect of eddy currents on metal fine particles in high gradient magnetic separation using a superconducting magnet

Abstract Dry high gradient magnetic separation is one of the key technologies expected in removing magnetic metal fine particles as contaminations in the production process of various powders. However, the effect of eddy currents on such metal fine particles in dry high gradient magnetic separation has not been adequately explored in previous research. In order to understand this phenomenon more comprehensively, we conducted particle trajectory simulations using a finite element analysis with numerical methods and actual magnetic separation experiments to investigate the influence of eddy currents on magnetic separation efficiency. The results show that for both paramagnetic and diamagnetic metal particles, eddy currents can favourably influence the capture efficiency. Furthermore, these effects depend on the particle size, electrical conductivity, and the rate of change in the magnetic field. Therefore, by taking eddy currents into account, magnetic separation systems can be better optimized and their performance further improved.

Effect of blunging process on purification of halloysite ore from ferrous impurities by dry magnetic separation

The objective of this research is to study the effects of feed particle size, splitter angle, and washing process on Fe<sub>2</sub>O<sub>3</sub> removal efficiency in the separation of ferrous impurities from halloysite ore by dry magnetic separation in order to increase the purity of halloysite sample after crushing and blunging processes separately. Firstly, after crushing ore in a jaw crusher and sizing to -2+1 mm, -1+0.5 mm, and -0.5+0.212 mm fractions, the sized materials were fed to REMS-type dry magnetic separator at a constant belt speed of 300 rpm with the splitter angles of 0, 15, 30º separately. Maximum Fe<sub>2</sub>O<sub>3</sub> removal efficiency (FRE) (97.1%) was obtained in the nonmagnetic product at -0.5+0.212 mm size fraction and 0º splitter angle. The minimum Fe<sub>2</sub>O<sub>3</sub> content (1.3%) was reached in the nonmagnetic product obtained in the experiment with the feed size of -2+1 mm and a splitter angle of 0º. Secondly, dry magnetic separation was applied to the washed -2+0.212 mm size fraction after drying at room temperature to evaluate the coarse particle-sized halloysite ore that was gained by mechanical dispersion in the aqueous medium towards sodium hexametaphosphate (SHMP), while a significant part of the clay minerals went into fine size after the dispersion process. In the experiment performed with a 0º splitter angle after washing, it was determined that halloysite concentrate of 0.4% Fe<sub>2</sub>O<sub>3</sub> content could be obtained with 98.8% Fe<sub>2</sub>O<sub>3</sub> removal efficiency. As a result of dry magnetic separation experiments, it was seen that Fe<sub>2</sub>O<sub>3</sub> removal efficiency decreased as the splitter angle increased, while Fe<sub>2</sub>O<sub>3</sub> content in magnetic and nonmagnetic products increased. It was determined that washing and cleaning of fine-sized minerals plastered on particle surfaces after mechanical dispersion and particle release of minerals with different magnetic properties increased the dry magnetic separation efficiency, and nonmagnetic products with very low Fe<sub>2</sub>O<sub>3</sub> (0.4%) and high Al<sub>2</sub>O<sub>3</sub> (31.9%) content was obtained. The blunging process in the presence of dispersant caused the dispersion of clay minerals and allowed to liberating of the ferrous minerals from the halloysite ore, hence the increase in the FRE for the magnetic separation.

Fundamental Study on Recovery of Spilled Oil by Magnetic Pickering Emulsification

Heavy oil spills from stranded oil tankers are a global problem. The recovery of spilled oil must have a low environmental impact and must be capable of processing large quantities at high speeds. In this study, we investigated the application of magnetic separation for the recovery of spilled oil. Pickering emulsions were formed by heavy oil and magnetite, and recovery was carried out using a drum‐type permanent magnet. Pickering emulsions were successfully formed by stirring heavy oil A and magnetite, and magnetic separation experiments showed that up to 90% of the heavy oil A could be recovered. To recycle magnetite, a small amount of heavy oil was added to the recovered Pickering emulsions, and then a strong magnetic field of a superconducting bulk magnet was applied, which resulted in easy solid–liquid separation. The possibility of recycling magnetite after separation was also demonstrated. Finally, a small‐scale system using drum‐type permanent magnets was developed, and magnetic separation experiments were performed. The results showed that approximately 77% of the heavy oil A could be recovered. Particle trajectory simulations also demonstrated the recoverability of heavy oil at the sea surface. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Iron, copper, and rare earth minerals beneficiation in an IOCG type deposit

ABSTRACT The sample of the Sineqan mine (Arak, Iran), containing 16.5% Fe, 0.13% Cu, 475 ppm Ce, 446 ppm La, and 134 ppm Nd, was characterised and processed to investigate the possibility of separating iron, copper, and REE minerals. Microscopic studies showed that the main minerals in the sample include magnetite, hematite, goethite, specularite, pyrite, and chalcopyrite, while the gangue minerals consist of quartz, clay minerals, and carbonate minerals. The results of heavy liquid studies using Bromoform showed that by reducing the particle size from 1180 to 300 micrometre, 76.6% of iron and 72.76% of copper went into the heavy section, while 77.9% of REEs entered the light section. The magnetic separation experiments revealed that higher magnetic field intensity increased the recovery of iron, copper, and REEs with no separation between them. In summary, the results indicate that REEs are primarily present in the light section due to their association with sphene silicate mineral, and gravity separation demonstrated superior performance in terms of both recovery and selectivity. The results of this research are significant for the processing of iron oxide-type deposits that contain copper and REEs.

Advancing iron ore slimes magnetic separation with functionalized Nanoparticles: Molecular insights from free energy simulations

Magnetic nanoparticles have diverse scientific and technological applications, as their properties can be tuned accordingly. An example is the selective magnetic coating technique for the selective adsorption of these colloidal particles on the surface of iron minerals to improve recovery of fines by magnetic separation. Thus, fundamental physicochemical knowledge of such systems is of paramount importance. Herein, we investigate the adsorption of magnetite nanoparticles on mineral surfaces and the impact of hydrophobic coating on the adsorption process and magnetic separation. We present structural and thermodynamic characterizations from molecular dynamics and free energy simulations to rationalize the differences in association process in both native and coated particle conditions. We demonstrate that hydrophobic coating of both nanoparticle and target iron oxide surfaces is essential for selective adhesion, revealed by ΔG. Also, tuning the degree of surface coverage by oleate leads to better interactions then simply establishing a monolayer coating, because of interdigitation of adsorption layers allowing higher contact area, shorter interparticle distance and less oleate consumption. Magnetic separation experiments of ultrafine iron ore particles under different oleate and colloidal magnetite concentrations validated the molecular level analyses, thus achieving successful experiment–theory nexus based on a sound theoretical background explored beforehand by computational simulations.

Removal of SUS304 fine particles transformed into martensite by the high gradient magnetic separation under dry condition

The interfusion of impurities such as metallic wear debris has been a major issue in the manufacturing process of foods, medicines and industrial products. Such debris originates with wearing of stainless-steel pipe joints or mechanical moving parts. Since the debris shows ferromagnetic properties by undergoing the strain-induced martensitic transformation of non-magnetic SUS304 (X5CrNi18-10), the magnetic separation system is much efficient to remove such debris from raw materials. In order to study the magnetic separation properties for the martensitic transformation fine particles, the several kinds of magnetic powder with different magnetization were prepared by controlling the amount of martensitic transformation by heat-treating SUS304 powders. The magnetic separation performance was evaluated by the high gradient magnetic separation (HGMS) experiments using the multilayer unidirectional magnetic wire filter under dry condition. The experimental results and FEM particle trajectory simulations revealed that the SUS304 powders transformed into martensite were removed at high speed of 0.1 m/s by the superconducting HGMS in a relatively low magnetic field.

Structure design and separation test of a conical AC magnetic separator for recovering magnetite powder

ABSTRACT In the dense-medium coal preparation process magnetite powder is used, however, due to poor recovery of the magnetite, the consumption of magnetite increases which ultimately reflects in the economics. In order to continuously and efficiently recover the magnetite, a novel three-phase conical magnetic separator based on the principle of an alternating magnetic field generated by a three-phase linear motor, was developed. The distribution law of the magnetic field in the separation chamber was studied, and the magnetic separator’s basic structure and parameters were determined. By varying the feed rate, coil current, coil turns, and particle size, magnetic separation experiments were conducted and compared with traditional magnetic separators. The results confirmed the excellent sorting performance of the conical AC magnetic separator.

DEMİR ÇELİK TESİS ATIKLARININ GERİ DÖNÜŞÜMÜ

As a result of the processes applied in the steel production, approximately 400 kg of waste is generated for every one ton of steel products. According to environmental regulations, these wastes must be disposed or stored in waste dams, which imposes a serious financial burden on iron and steel enterprises. In recent years, wastes with a high iron content has been recovered and returned to the steelmaking processes, replacing ore and contributing to a more efficient use of resources. However, despite the high iron content, it is not possible to use high sulphur content wastes as raw material in steel production. In this study, it is aimed to increase the utilization possibilities of these wastes as secondary raw material by reducing the content of sulphur in the concentrate by magnetic separation. It was shown that 33.34% of the wastes can be recycled with 54.90% iron recovery and 74.43% sulphur removal after dry magnetic separation experiments while 14.66% of the wastes can be recycled with 28.60% iron recovery and 89.93% sulphur removal after wet magnetic separation experiments. These removals correspond to 0.03% and 0.01% sulphur contents in the concentrates after dry and wet magnetic separations, respectively, and the concentrates can be blended back into the main raw material.

Removal of Magnetic Fine Particles From Carbon Black Powder by High Gradient Magnetic Separation Under Dry Condition

Removal of magnetic fine particles from carbon-black powder by utilizing the high gradient magnetic separation with a newly developed magnetic wire filter under dry condition was studied. The developed magnetic filtering system has magnetic thin wires arranged in one direction with a regular interval and the rotating layered structure perpendicular to the magnetic field direction. This makes it possible to capture the magnetic fine particles without clogging the filter under dry condition. The capture rate in the magnetic filter was investigated in detail by both magnetic separation experiments and three-dimensional FEM particle trajectory simulations. With reducing both the magnetic wire size and the wire spacing, and with increasing the number of layers, the capture rate increased significantly. By optimizing the filter design, we succeeded in removing 100% of iron particles with a size of 48 microns in carbon black powder under low magnetic fields without clogging the filter. Consequently, it became clear that the newly developed filter is very effective in removing magnetic particles in the powder under dry condition.

Capture effect of dry magnetic separator on biotite in fine aggregates: Experimental results and numerical simulations

In this paper, a series of magnetic separation experiments and FEM-DEM simulations were carried to study the dynamic capture behavior of a dry magnetic separator (DMS) for biotite in fine aggregates. Experimental results show that the capture effect of a DMS on biotite in fine aggregates is greatly affected by the particle size. Coarse particles (2 mm–4.75 mm) and ultrafine particles (0–0.075 mm) are difficult to be captured by the DMS, while fine particles (0.075 mm–2 mm) are easy to be captured. Numerical simulations show that the effect of a DMS on the captured morphology of biotite in fine aggregates comes from the arrangement of magnetic system structure. Compared with magnetic induction, the magnetic induction gradient produced by the extruded magnetic system has a more profound effect on the capture process of biotite. Based on the comprehensive analysis results of experiment and simulation, we conclude that the capture mechanism of DMS on biotite can be divided into four processes: magnetization, extrusion, entraining and separation. This study provides a theoretical basis for evaluating the effectiveness of DMS in sorting biotite from fine aggregates and designing high-performance DMS. • Capture mechanism of biotite by DMS was revealed through experiments and simulations. • A coupled FEM-DEM simulation program is developed. • Captured morphology of DMS on biotite in fine aggregates was demonstrated.

Zero valent iron or Fe3O4-loaded biochar for remediation of Pb contaminated sandy soil: Sequential extraction, magnetic separation, XAFS and ryegrass growth

In this study, the feasibility of using zero-valent iron (ZVI) and Fe3O4-loaded biochar for Pb immobilization in contaminated sandy soil was investigated. A 180-day incubation study, combined with dry magnetic separation, chemical extraction, mineralogical characterization, and model plant (ryegrass, namely the Lilium perenne L.) growth experiment was conducted to verify the performance of these two materials. The results showed that both amendments significantly transferred the available Pb (the exchangeable and carbonates fraction) into more stable fractions (mainly Fe/Mn oxides-bound Pb), and ZVI alone showed a better performance than the magnetic biochar alone. The magnetic separation and extended X-ray absorption fine structure (EXAFS) analysis proved that Fe (oxyhydr)oxides on aged ZVI particles were the major scavengers of Pb in ZVI-amended soils. In comparison, the reduced Pb availability in magnetic biochar-amended soil could be explained by the association of Pb with Fe/Mn (oxyhydr)oxides in aged magnetic biochar, also the possible precipitation of soil Pb with soluble anions (e.g. OH−, PO43−, and SO42−) released from magnetic biochar. ZVI increased ryegrass production while Fe3O4-loaded biochar had a negative effect on the ryegrass growth. Moreover, both markedly decreased the Pb accumulation in aboveground and root tissues. The simple dry magnetic separation presents opportunities for the removal of Pb from soils, even though the efficiencies were not high (17.5% and 12.9% of total Pb from ZVI and biochar-treated soils, respectively). However, it should be noted that the ageing process easily result in the loss of magnetism of ZVI while the magnetic biochar tends to be more stable and has high retrievability during the dry magnetic separation application.

Material manipulation and separation using the horizontal magneto-Archimedes effect

We have studied the manipulation and the separation of substances using the horizontal magneto-Archimedes effect. By ingenerating a high magnetic field gradient in the horizontal direction, it is possible to move the target substance to a designated position in the horizontal direction. We attempted to separate several kinds of valuable metals by applying the horizontal magnetic force to the metals falling vertically into a paramagnetic medium. In order to enhance the magnetic force, we set up the ferromagnetic core array in magnetic fields. According to the trajectory analysis for the metal particles and the magnetic separation experiments, we succeeded in dynamically separating the metal mixture dropped to the vertical direction due to the strong horizontal magnetic force in relatively low magnetic fields. It is expected that this method creates a new device for the separation of substances.

Multiphysics Modeling Simulation and Optimization of Aerodynamic Drum Magnetic Separator

Aerodynamic Drum Magnetic Separator (ADMS) uses an adjustable air flow to enhance the separation of magnetic particles from gangue. In order to explore the matching relationship between the magnetic field, the flow field, and the gravity field, as well as the capture and separation behavior of particles under the action of multi-physics, a related simulation model is established using the finite element software COMSOL Multiphysics and the accuracy of the simulation results is verified by measurement, formula calculation, and magnetic separation experiment. The trajectories and capture probabilities of particles in different magnetic fields and flow fields are calculated, as well as the critical airflow velocity corresponding to a specific capture probability. In addition, the magnetic field characteristics and particle capture effect of N-S alternate arrangement and N-N homopolar arrangement are compared by optimizing the permutation of magnetic poles. This model may provide a reference for the accurate control of magnetic separation enhanced by a coupling force field.

Development of impurities removal process for low-grade Sanje iron ore using mineral processing technologies

In this study, the impurities removal process for low-grade Sanje iron ore was developed using Wet High-intensity magnetic separation (WHIMS) and Reverse flotation (RF). Sanje Iron Ore is the low-grade hematite ores found in Nampundwe area of Zambia from which Iron is to be extracted and used as the feed in the steelmaking process. The ore contains 34.18 mass per cent Iron grade, 31.10 mass% of Silica (SiO2) and 7.65 mass per cent Alumina (Al2O3). Magnetic Separation experiments were done using Series L Model 4 laboratory magnetic Separator (L-4 Machine) as the first stage impurity removal process and the effect of various magnetic separation parameters such as magnetic flux density, particle size density and pulp density of the feed were studied. The results showed that 10 T was optimal magnetic flux density which enhanced the recovery of 93 per cent of iron with 53.22 mass per cent grade. The iron concentrate produced from magnetic separation contained 12.04 massper cent Silica and 3.94 massper cent Alumna and therefore, it was further treated using Reverse flotation. In reverse flotation, various parameters such as pH, collector dosage, Iron depressant dosage and quartz activator dosage were investigated. The results showed that 81.94 per cent was recovered at the concentrate’s pH of 6.8 using 200 g/T of 0.1 per cent calcium oxide (CaO) as silica activator and one kg/T of 0.1 per cent causticised starch as Iron depressant. Sodium Oleate (NaOL) and Dodceylamine Acetate (DAA) each with discrete dosage, were used as Anionic and Cationic collectors respectively. Alumina was consequently reduced to 1.04 mass per cent and Silica to 2.04 mass per cent at optimum respective collector’s dosage of 0.250 kg/T using 0.02 kg/T of Methyl Isobutyl Carbinol (MIBC) frother. Additionally, phosphorous was also observed to be reduced from 0.05 mass per cent to 0.01 mass per cent. The designed multi-stage process involving feeding the concentrate from WHIMS into RF process therefore produced a high-grade iron concentrate iron with 67.27 mass per cent grade, 2.04 mass per cent silica, 1.04 mass per cent alumina.

Removal of Iron Oxide Scale From Feed-Water in Thermal Power Plant by High-Gradient Magnetic Separation: Scale-Up Effect

In the boiler feed-water system of thermal power plants, iron oxide scale is generated due to the corrosion of piping, which decreases the effectiveness of the heat exchanger in the boiler and contributes to reduced power generation efficiency. Scale removal can prevent this phenomenon, which consequently results in decreased carbon dioxide emission. In a previous study, an iron scale removal system was developed using superconducting magnets, and high-gradient magnetic separation (HGMS) experiments were conducted using the height difference between the inflow and outflow tanks. As a result, particles were intensively captured by the filters at the inflow side. We succeeded in eliminating this capture by properly controlling the applied magnetic field. However, because the suspension also flowed due to the height difference in this experiment, the problems of partial blockage of the filter and the resulting decrease in the flow rate were not resolved even under the controlled magnetic field. In this study, HGMS experiments were conducted under a constant flow rate with a large pump in a large-scale system having a filter diameter of 300 mm to simulate a boiler feed-water system or chemical cleaning line. Furthermore, we investigated the feasibility of the large-scale HGMS system and elucidated the scale-up effect on the amount captured and the spatial distribution of the captured particles on the filters. Based on these results, a plant-scale HGMS system (800 mm filter diameter) was designed.

Microwave-assisted reduction roasting—magnetic separation studies of two mineralogically different low-grade iron ores

The microwave-assisted reduction behaviours of two low-grade iron ores having a similar Fe content of 49wt% but distinctly different mineralogical and liberation characteristics were studied. Their performances in terms of the iron grade and recovery as obtained from statistically designed microwave (MW) roasting followed by low-intensity magnetic separation (LIMS) experiments were compared. At respective optimum conditions, the titano-magnetite ore (O1) could yield an iron concentrate of 62.57% Fe grade and 60.01% Fe recovery, while the goethitic ore (O2) could be upgraded to a concentrate of 64.4% Fe grade and 33.3% Fe recovery. Compared with the goethitic ore, the titano-magnetite ore responded better to MW heating. The characterization studies of the feed and roasted products obtained at different power and time conditions using X-ray diffraction, optical microscopy, vibrating-sample magnetometry, and electron-probe microanalysis explain the sequential reduction in the iron oxide phases. Finally, taking advantage of the MW absorbing character of the titano-magnetite ore, a blend of the same with the goethite-rich ore at a weight ratio of 60:40 (O2: O1) was subjected to MW roasting that resulted in a concentrate of 61.57% Fe grade with a Fe recovery of 64.47%.

Dry magnetic separation technology for the recovery of iron minerals in fine-grained steel slag

Using the MagNet software package, a permanent magnetic circuit was simulated and a sectorially-spliced magnetic system was designed. Consequently, a new roller permanent magnetic separator with different magnetic field intensities in each roller was developed. The modular structural design allows fine-grained minerals with different magnetic susceptibility to be separated in one pass, according to their different processing characteristic. Steel slag, selected from a factory, was crushed, ground and sieved into different particle size ranges for the single-factor magnetic separation experiments. It was determined that the optimum value ranges for the particle size, magnetic separation distance and rotating frequency were 0.15 mm-0.3 mm, 10 mm-12 mm, 40 Hz～60Hz, respectively; using the chosen parameter values of 0.2mm, 11mm, and 40Hz, the concentrate recovery and concentrate grade of the new separation technology reached up to 52.78% and 64.74%, in comparisson with the existing technology. Thus, it was demonstrated that the self-developed separation technology has the potential to improve the iron recovery of the fine-grained steel slag.

Removal of Scale from Feed-water in Thermal Power Plant by Magnetic Separation -Analysis of Oxygenated Treatment Scale-

One of the reasons of the deterioration of the power generation efficiency of the thermal power generation is the adhesion of the iron scale generated by the corrosion of the pipe to the inner wall of the feed-water system. Focusing on the magnetic property of scale, we studied on the removal of scales in the feed-water system by high gradient magnetic separation (HGMS) using the superconducting magnet. In this study, we targeted the thermal power plants adopting oxygenated treatment (OT). In order to determine the installation site and the magnetic separation condition of the HGMS system, we analyzed the OT scale and then clarified the aggregation/composite states by magnetic separation experiment. It is concluded that low-pressure feed-water heater drain is suitable for installation site of HGMS system. In addition, it was clarified that homogeneous aggregation particles existed in the OT scale.

Comparison of iron ores upgraded with Falcon concentrator and magnetic separators assisted by coal reduction-conversion process

This study investigated the effects of iron ore roasting on iron ore beneficiation. Hematite-magnetite conversion was comprehensively investigated and characterized by XRD, SEM, and M–H analyses. The magnetic susceptibilities of the materials were shown by Honda–Owen plots. The optimum magnetite transformation conditions were found as 800°C temperature, 10 wt.% coal and 10 min reaction time. Preliminary tests with the unroasted ores were conducted before the optimization and comparison tests. The Box Behnken test design was used for modeling the falcon concentrator separation tests. High-intensity wet magnetic, low-intensity dry magnetic and falcon gravity separators were applied to the roasted and unroasted ores at the optimum test conditions. After conversion, the iron concentrations in the grade that could be sold (>56% Fe) were obtained by the wet magnetic separator and the falcon gravity separator with the recovery yields of 90.87 and 81.72%, respectively. The positive effects of roasting were observed in terms of concentrate yields for the wet magnetic separation and gravity separation methods. However, desired saleable iron concentrates were not achieved by dry magnetic separation experiments, although the recovery yields were raised above 80% after the conversion process.

Investigation of Efficiency of Magnetic Separation Methods for Processing of Low-Grade Iron Pigments Ore (RED Ochre)

In this research, the efficiency of magnetic separation methods for processing of a low-grade iron pigments ore (red ochre) has been studied. Based on the mineralogical analyses (XRD), thin section and polish studies, the reserve is an iron sedimentary deposit with an average Fe grade of %31.3. The most valuable minerals are Hematite and Goethite and main gangue minerals are Calcite and Quartz. Wet and dry high-intensity magnetic separation methods were applied for processing. The full factorial design was implemented for all of the wet high-intensity magnetic separation (WHIMS) experiments. Factors of magnetic field intensity, rotor speed and feed water flowrate were considered for design. In optimal conditions in rougher stage, WHIMS produced a concentrate with grade %42.92 Fe and recovery %62.23 in magnetic field intensity 1.7 Tesla, feed water flowrate 5 liter per minute and speed of rotor 3 rounds per minute; also after two stage cleaning WHIMS produced a concentrate with Fe grade and Fe recovery of %56.12 and %38.56, respectively. The results of the dry high-intensity magnetic separation for the two coarser fractions showed that size fraction of coarser than 1000 micron produced a concentrate with Fe grade %40.32 and relative Fe recovery %95.11 and size fraction of -1000+150 micron with Fe grade %45. 04 and relative Fe recovery %75.14. The results of experiments show that there is a low capability for improving quality and grade of this ore. Achieved concentrate from experiments could be used as an initial feed of producing pigment.