Low-intensity Magnetic Separation Research Articles

Evaluation and comparison of different machine-learning methods to integrate sparse process data into a spatial model in geometallurgy

A spatial model for process properties allows for improved production planning in mining by considering the process variability of the deposit. Hitherto, machine-learning modelling methods have been underutilised for spatial modelling in geometallurgy. The goal of this project is to find an efficient way to integrate process properties (iron recovery and mass pull of the Davis tube, iron recovery and mass pull of the wet low intensity magnetic separation, liberation of iron oxides, and P80) for an iron ore case study into a spatial model using machine-learning methods. The modelling was done in two steps. First, the process properties were deployed into a geological database by building non-spatial process models. Second, the process properties estimated in the geological database were extracted together with only their coordinates (x, y, z) and iron grades and spatial process models were built. Modelling methods were evaluated and compared in terms of relative standard deviation (RSD). The lower RSD for decision tree methods suggests that those methods may be preferential when modelling non-linear process properties.

Upgrading iron and removing phosphorus of high phosphorus oolitic iron ore by segregation roasting with calcium chloride and calcium hypochlorite

The iron-bearing ore, existing in the form of oolite, was mainly composed of hematite, limonite, daphnite, and collophane. The harmful element phosphorus content was 1.56%, belonging to high phosphorus ooliticiron ore in western Hubei. In this study, segregation roasting and low intensity magnetic separation techniques were applied for upgrading iron and removing phosphorus. The ores, the chlorinating agent, and the reducing agent were mixed into the roasting furnace for segregation roasting. After being transferred from the weak magnetic minerals to the strong ones, the iron was recovered by low intensity magnetic separation. During segregation roasting, new ore phases, metallic iron (Fe), a small amount of ferroferric oxide (Fe3O4), and ferrous oxide (FeO) could be observed. The results showed that the iron concentrate with the Fe content of 90.3%, the phosphorus content of 0.15%, and the iron recovery of 92.9% were obtained under the segregation roasting temperature of 1273 K, and the roasting time of 90 min, CaCl2 (calcium chloride) 20%, Ca (ClO)2 (calcium hypochlorite) 3%, the dosage of coke 20%, and low intensity magnetic separation field intensity 0.12 T.

Beneficiation of a low-grade iron ore by combination of wet low-intensity magnetic separation and reverse flotation methods

Beneficiation of a low-grade iron ore was investigated by combination of the low-intensity magnetic separation and reverse flotation methods. The main constituents of the representative sample were 36.86% Fe, 8.1% FeO, 14.2% CaO, 13.6% SiO2, and 0.12% S based on the X-ray fluorescence, titration, and Leco analysis methods. The mineralogical studies by the X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron probe micro-analyzer, and Fe/FeO titration methods showed that the ore minerals present in the representative sample were magnetite, hematite, and goethite, and the main gangue minerals were calcite and quartz. The effects of the operating parameters including the feed size, solid content, and drum rotation speed were investigated on the performance of the wet low-intensity magnetic separation (WLIMS). The optimum operating conditions of WLIMS were determined to be feed size = 135 μm, solid content = 40%, and drum rotation speed = 50 rpm. Under these conditions, a concentrate of 62.69% Fe grade and 55.99% recovery was produced. The tailing of WLIMS with an iron grade of 28.75% was upgraded by reverse flotation with fatty acids as the collector. The effects of five parameters on two levels were investigated using the 25-1 fractional factorial design in 16 experiments. The optimum flotation conditions were determined to be pH = 12; dosage of collector, 1 kg/t; dosage of Ca2+ as activator, 4 kg/t; and dosage of starch as depressant, 1 kg/t. Under these conditions, a concentrate of 53.4% Fe grade and 79.91% recovery was produced.

Beneficiation Studies of a Rare Earth Ore from the Olserum Deposit

The Olserum deposit located in Sweden hosts an indicated mineral resource of 4.5 million tonnes at 0.6% total rare earth oxides (TREO), exhibiting a relatively high proportion of heavy rare earth elements (HREE). The mineralogy and beneficiation of a composite drill core sample from the Olserum deposit were studied. Monazite and xenotime were found by the mineralogical analyses to be the target minerals for beneficiation of REEs and most (96.9%) of REEs in the ore are carried by monazite (68.5%) and xenotime (28.4%). Because xenotime carries 84.7% of heavy REEs (Y, Gd, Dy) in the ore it is more valuable mineral than monazite. A beneficiation process was developed which includes grinding, wet low intensity magnetic separation (WLIMS) for removal of magnetite and REEs flotation consisting of one stage of roughing and two stages of cleaning. Selective flotation collector of REE minerals and suitable grinding size of feed material were determined by testwork. The REE concentrate and tailings were chemically and mineralogically characterized. The studies of process mineralogy showed that the REE-bearing minerals, monazite and xenotime, and apatite were successfully enriched from the concentrations of 0.6%, 0.31% and 2.6% in the feed to those of 17.0%, 8.9% and 65.0% in the concentrate with the recoveries of 79.0%, 81.3% and 71.0%, respectively.

Geometallurgical characterisation of Leveäniemi iron ore – Unlocking the patterns

As part of a geometallurgical program for the Leveäniemi iron ore mine, the Davis tube was used as proxy to classify ore types, predict iron recoveries in wet low-intensity magnetic separation (WLIMS), and to estimate liberation of mixed particles. The study was conducted by testing 13 iron ore samples with a Davis tube and a laboratory WLIMS. Ore feed was studied for modal mineralogy and liberation distribution with Automated Scanning Electron Microscopy. Data analyses to detect the patterns and data dependencies were done with multivariate statistics: principal component analysis, and projection to latent structures regression. Results show that a simple index (XLTU) based on mass pull in the Davis tube is capable of easy classification of magnetite ores. Using Davis tube mass pull and iron recovery, together with iron and Satmagan head grades may predict iron recovery in WLIMS. Also, the variability in Fe-oxides liberation pattern for magnetite semi-massive ores can be explained with the chemical composition of the Davis tube concentrate. It is concluded that the Davis tube test is better used only for marginal ores, since iron oxide minerals tend to be fully liberated in high-grade magnetite massive ores after grinding. The developed models may be used in populating a production block model.

Characterization vis-á-vis utilization of blast furnace flue dust in the roast reduction of banded iron ore

Abstract The present study explores the process of simultaneous roast-reduction and magnetic separation of blast furnace flue dust (BFD) and a low grade banded iron ore without using any extra reductant. The optical microscopic studies on the BFD sample revealed the presence of hematite, magnetite, silicates and unburnt carbon while the elemental mapping using Electron Probe Micro Analysis (EPMA) indicated the close association of silicates with Ca, K and Na bearing phases. The studies using the Scanning Electron Microscopy coupled with an Energy Dispersive X-ray Spectroscope (SEM-EDS) confirmed the presence of carbon both as an individual entity and in association with other phases as carbonates. The iron ore used was banded in nature and mostly consisted of hematite and quartz. Under statistically optimized conditions such as temperature: 850 °C, time: 90 min and BFD to ore ratio: 0.4, the process of reduction roasting followed by low intensity magnetic separation (LIMS) could yield an iron ore concentrate of ∼63% Fe at an iron recovery of ∼68% from the BFD with 32% Fe and banded iron ore with 47.2% Fe. Similar results were also obtained using the same BFD to ore ratio for a roasting temperature of 950 °C and a time period of 30 min. The products roasted at a high temperature of 1050 °C or at a temperature of 950 °C with a higher residence time of 120 min showed poor iron recovery and high grade in the LIMS magnetic fraction, which was attributed to the formation of feebly magnetic phases like wustite and fayalite.

Optimisation of a Multi-Gravity Separator with Novel Modifications for the Recovery of Ferberite

Tungsten is considered by the European Union as a critical raw material for future development due to its expected demand and scarcity of resource within Europe. It is therefore, critical to optimize European tungsten operations and maximise recoveries. The role of enhanced gravity/centrifugal concentrators in recovering tungsten from ultra-fine fractions should form an important part of this aim. Reported herein are the results of investigations to improve efficiency of Wolf Minerals’ Draklends mine, a major European tungsten mine, by recovering saleable material from a magnetic waste stream of a low-intensity magnetic separator using an enhanced gravity concentrator. The mine hosts wolframite and ferberite as the main tungsten bearing mineral species. A Mozley multi-gravity separator (MGS) C-900 was selected as it is suited to exploiting small variations in mineral density to affect a separation. Working with a current manufacturer, a novel scraping blade system was tested. To assess the MGS in a statistically valid manner, a response surface methodology was followed to determine optimal test conditions. The test programme showed that the most important parameters were drum speed and wash water rate. Under optimal conditions the model predicted that 40% of the tungsten could be recovered above the required grade of 43% WO3.

Fully coupled multi-physics modeling of the multi-type magnetic particles dynamic behavior in low intensity magnetic separator

Fully coupled multi-physics modeling of the multi-type magnetic particles dynamic behavior in low intensity magnetic separator

Investigation into recovery of iron values from red mud dumps

ABSTRACTThe waste generated during the alumina production by Bayer’s process is popularly called red mud. This red mud is a rich source of iron values. Generally, the iron content in the red mud varies between 20% and 45% depending on the bauxite source. The present investigation was carried out to recover iron values from red mud. Red mud contains ultrafine particles and is highly alkaline in nature because of which it is difficult to recover the iron values from it using conventional beneficiation techniques. In the present investigation, the iron values were successfully recovered by reduction roasting followed by magnetic separation. During the process, the hematitic and goethitic iron-phase minerals present in the red mud sample are converted into magnetite and metallic irons, which are subsequently recovered using low-intensity magnetic separator. The results showed that an iron recovery of 61.85% with an iron content of 65.93% of iron concentrate could be obtained at roasting temperature of 1150°C, roasting time of 60 min, and magnetic field intensity of 0.18 Tesla.

Recovery of iron and lead from a secondary lead smelter matte by magnetic separation

A secondary Pb smelter matte with a total Fe grade of ca. 50% (as FeS, Fe3O4, FeO and metallic Fe), shows good potential for being used as a secondary Fe source. However, requirements for Fe ore are: a total Fe grade >60% and a sulphur content as low as possible. Therefore, further treatment steps are necessary to increase the Fe content in the matte. Dry low intensity, wet low intensity and wet high intensity magnetic separation experiments were performed on different particle size fractions of the matte. Mineral liberation analysis (MLA) was performed to explain different behaviours of Pb in the different size fractions during magnetic separation. Moreover, oxidizing roasting at 600 °C was carried out to transform FeS to Fe2O3, which is the more prefered form of Fe for pig iron production. Results show that by combining low and high intensity magnetic separation and oxidizing roasting, material with a total Fe grade of 61% (as oxide) can be recovered in the magnetic fraction representing circa 50% of the initial weight of the sample. Moreover, the sulphur content was reduced from initial 20 to 4% in the final magnetic fraction. Further reduction in sulphur content would require an additional desulphurization step.

Up-gradation of banded iron ores for pellet grade concentrate

As per national steel policy vision 2030, around 500 million tons of quality iron ore is required to produce 300 million tons of steel. In this context, the use of low grade banded iron ores (Fe∼ 30-45%, 40-50% silica) is inevitable. Reduction roasting followed by magnetic separation technique is employed to treat such ore. In this work, banded iron ore with 32% Fe is enriched to a concentrate of ∼53-57% Fe using reduction roasting followed by low-intensity magnetic separation technique. A concentrate of 35% recovery with 53% Fe grade was achieved using Wet High-Intensity Magnetic separator at 12000 Gauss. In case of microwave reduction roasting a concentrate of 57.19% Fe grade and 17.82%wt. recovery is obtained at optimum conditions (540W, 3 minutes and 7% charcoal). Whereas, in muffle furnace reduction roasting 52.95%Fe grade and 47.38%wt. recovery concentrate is obtained at 900°C, 8% charcoal and 30 minutes time.

Investigation on beneficiation of goethite-rich iron ores using reduction roasting followed by magnetic separation

ABSTRACTIn this study, reductive roasting followed by low-intensity magnetic separation were used to upgrade iron ore from Gua mines in Jharkhand. The work aimed to maximise the recovery of iron values by upgrading to a high-grade product suitable for pelletisation and sintering. The received ore contains 58% Fe, 7.82% silica, 4.26% alumina and 4.97% loss on ignition. Reductive roasting experiments were conducted at times of 10, 20 and 30 min at 600°C, 700°C and 900°C using coal as a reducing agent. Roasted samples were processed using a low-intensity magnetic separator. Best results were obtained at 800°C for 30 min using 10% coal in the charge. Using these conditions a product containing 66.6% Fe was produced at 90.4% recovery. The roasted samples were characterised by XRD which confirms the hematite to magnetite transformation and by SEM which highlighted the porous nature of the upgraded ore.

Dolochar as a reductant in the reduction roasting of iron ore slimes

The present investigation examines the viability of dolochar, a sponge iron industry waste material, as a reductant in the reduction roasting of iron ore slimes, which are another waste generated by iron ore beneficiation plants. Under statistically determined optimum conditions, which include a temperature of 900°C, a reductant-to-feed mass ratio of 0.35, and a reduction time of 30–45 min, the roasted mass, after being subjected to low-intensity magnetic separation, yielded an iron ore concentrate of approximately 64wt% Fe at a mass recovery of approximately 71% from the feed iron ore slime assaying 56.2wt% Fe. X-ray diffraction analyses indicated that the magnetic products contain magnetite and hematite as the major phases, whereas the nonmagnetic fractions contain quartz and hematite.

Characterization and Reduction Roasting Studies of an Iron Rich Manganese Ore

The article presents the reduction roasting followed by low intensity magnetic separation studies of a low grade Mn ore assaying 27.7% Mn and 26.1% Fe in order to obtain a Mn rich non-magnetic concentrate. The reflected light microscopic studies followed by the liberation studies of the as-received sample using quantitative mineralogical evaluation by scanning electron microscope suggested a poor liberation pattern of the constituent Mn and Fe minerals owing to a complex association of the different phases present. The reduction roasting studies carried out while varying different process parameters such as ore particle size, temperature, reductant content and residence time ended up with products containing 45–48% Mn with a Mn/Fe ratio of 5–6 at a yield of ~ 60% with the optimum level of conditions such as temperature: 800–850 °C, time: 90–120 min and charcoal: 10–12%. The scanning electron microscopy–energy dispersive X-ray spectroscopy studies of the roasted product reported manganite as the major Mn bearing phase while magnetite was found to be the major iron bearing phase.

Phase transformation during roasting process and magnetic beneficiation of oolitic-iron ores

Oolitic-iron ore material is one of the most important iron resources in China. However, due to its low grade of Fe, poor liberation of iron minerals and high impurities, no satisfactory processing method has been developed to effectively utilize it for the practical applications. In this work, a coal-based reductive roasting method was applied, where the detail mineral phase transformation and reduction area during magnetic roasting process was quantitatively investigated. Then, low intensity magnetic separation was performed. The results showed that roasting time significantly affected Fe recovery, with a minor influence on Fe content of concentrate. Fe recovery increased from 10 to 60 min before starting to decrease slightly. This may result from the formation of weakly magnetic FeO or Fe3O4-FO (solid-melt-body), where the reduction degree increased gradually from 10 to 50 min. During the roasting process, the mineral phase Fe2O3 changed to Fe3O4, but the original oolitic structure and mineral embedding relation were hardly evolved. This research could enhance our understanding regarding the microscopic view of magnetic phase transformation, and provide help for commercial development of such refractory iron ores.

Increasing Silicate Grade in Crude Ore

Luossavaara-Kiirunavaara AB (LKAB) operates an iron ore mine, three concentration plants and three pelletising plants in Kiruna, Sweden. The current methods of separation at the beneficiation plants are low intensity magnetic separation (LIMS) and reverse flotation (i. e., apatite is floated and magnetite depressed), where the wet LIMS stage is regarded as the crucial part of the separation of silica from the ore. It is increasingly important to understand the Kiirunavaara high-grade iron ore deposit from a mineral processing perspective as well as from a mineralogical and geochemical perspective as the production in the mine is advancing towards deeper levels with higher concentrations of SiO2 in the ore. The mineral processing parameters such as the natural breaking characteristics, specific energy consumption and degree of liberation of magnetite and silicate minerals are equally important. The intergrowth of magnetite with actinolite is of particular importance for understanding the processes in the processing plants in Kiruna and the flotation behaviour of silicate minerals. The iron ore deposit at Kiirunavaara consists mainly of magnetite and apatite, with an average grade of 63.8% Fe and 0.4% P (estimated from the 3D resource model, LKAB) and with varying, but mostly small, amounts of gangue minerals, mostly silicates and carbonates. Based on mineralogical investigations, actinolite and phlogopite and in many cases also chlorite, titanite, quartz and albite are the most significant SiO2-bearing minerals in the ore. Currently, the high-grade iron ore deposit of Kiirunavaara has in situ a low grade of silica of approximately 3% SiO2. However, the SiO2 grade is expected to increase in the deeper parts of the deposit. It can be assumed that the silicate mineralogy and the SiO2 grade in the crude ore undoubtedly impact the SiO2 content of the final products, i. e. the iron ore pellets and/or iron ore fines. This results in new challenges and requirements for the production at LKAB. Within the framework of the completed “Silica in the Mine” project, which was an important research and development area for LKAB for several years, the entire production chain from “the mine to the mill” and from “the mill to the final product” was evaluated in several subprojects. Important information was gained from the results of these subprojects in order to better understand the problem of the increasing and fluctuating SiO2 grades in the crude ore and magnetite concentrate. To study the reduction of the SiO2 content additionally in the magnetite concentrate obtained by WLIMS, a reverse cationic flotation laboratory test programme was initiated in the early spring of 2016. This flotation test work was based on the investigation carried out at the mineral processing laboratory at the Geological Survey of Finland (GTK). To obtain additional information about the problem of SiO2 and the behaviour of individual silicates during mineral processing, an extensive large-scale sampling programme will be carried out at the different stages of the process at the beneficiation plants (KA1, KA2, KA3) at the Kiirunavaara site.

Separation and recovery of iron from a low-grade carbonate-bearing iron ore using magnetizing roasting followed by magnetic separation

ABSTRACTIn this study, a process of magnetizing roasting followed by low-intensity magnetic separation (MR-LMS), which is used to separate and recover iron from a low-grade carbonate-bearing iron ore (containing 34.6 wt.% Fe), was investigated. A magnetic concentrate containing 65.4 wt.% Fe with an iron recovery rate of 92.6 wt.% was obtained under optimal conditions: roasting temperature of 800°C, roasting time of 8 min, bitumite ratio of 10:100, grinding fineness of around 85 wt.% passing 38 µm, and magnetic intensity of 0.12 T. In addition, the phase transformation and magnetic properties were analyzed by X-ray diffraction (XRD) and vibrating sample magnetometry (VSM) to reveal the mechanism.

Sulphur removal of iron ore tailings by flotation

ABSTRACTIron ore tailings have become one kind of the most hazardous solid waste. Beneficiation of iron ore tailings is a significant issue in the world steel industries, from the point of view of both pollution control and secondary resources. This investigation addressed the processing of tailings with high sulphur content from an iron ore concentrator to produce pellet feed fines and to prevent acid mine drainage. This study was the lab-scale testing of an integrated method consisting of froth flotation combined with gravity and magnetic separation. Reverse flotation located at the end of the primary treatment circuit (high- and low-intensity magnetic separation) will lower a large amount of the sulphur from magnetic separator concentrate. The effects of various operating parameters such as concentrations of collector, frother, depressant and activator, pH, solid-in-pulp concentration have been studied on the sulphur removal using reverse flotation. According to the data presented in this study, the maximum recovery of total sulphur was obtained when the operational parameters were set to the PAX dosage160 gr/t, MIBC dosage 140 gr/t, CuSo4 100 gr/t, air flow rate 10 l/min, pH 8.5, and pulp density 30%. With these optimum parameters, final concentrate with the grade of 63.7% Fe and 0.085% S was obtained. The results of this study indicated that, with this method, a great amount of iron concentrate is produced and, simultaneously, the sulphidic fraction is separated that can later be managed more easily owing to the reduced volume.

PREPARATION AND SEM-EDX-XRD CHARACTERIZATION OF MAGNETIC ZEOLITIC MATERIALS OBTAINEDFROM COAL FLY ASH

A low-cost magnetic zeolitic material was synthesized from coal fly ash by means of a new, simple method involving alkaline hydrothermal zeolitization of fly ash (FA) followed by low-intensity wet magnetic separation. Scanning electron microscopy with energy-dispersive X-ray analysis was applied to characterize the composition, microstructure, and morphology of the material. The mineral and synthetic zeolite phases were identified by powder X-ray diffraction. The obtained magnetic zeolitic material (about 53 wt% of the raw fly ash) consisted predominantly of fly ash particles with moderate to high Fe content (10 - 60 wt%), covered with 2-3 m thick shell of zeolite A crystals with fine crystals of zeolite P on them. Small iron oxide particles captured in larger iron-lean (< 2 wt%) zeolitized FA particles were also present in the product. Occasionally, uncovered iron oxide particles were detected, as well. The obtained magnetic zeolitic material could be easily manipulated in water suspension by means of low-intensity magnetic field and has potential application as an adsorbent for the removal of water contaminants from large volume effluents.

Innovative methodology for recovering titanium and chromium from a raw ilmenite concentrate by magnetic separation after modifying magnetic properties

Raw ilmenite concentrate containing Cr can be either as a resource or as one kind of the most hazardous solid waste. In order to recover titanium and chromium from the raw concentrate which was separated from the Promenade deposit, Gaza province, Mozambique, an innovative technology using modification of magnetic property followed by magnetic separation was proposed. Magnetic property, phase and surface morphology of the sample before and after oxidizing roasting were firstly characterized by magnetism, chemistry, XRD and MLA analyses to interpret the mechanism of oxidizing roasting of the ilmenite. Then, these factors such as oxidizing roasting temperature, residence time and magnetic induction affecting on magnetic separation performance were examined and the optimum process parameters were determined. A commercial concentrate containing 47.94% TiO2 and 0.23% Cr2O3 was obtained and the recovery of TiO2 and Cr2O3 was 78.52% and 5.42%, respectively. The tailing obtained was preliminarily concentrated by a high-intensity magnetic separator and a rough chromite concentrate was gained. In order to further purify the rough one, reducing roasting was carried out to transform the minerals containing hematite into the minerals containing magnetite, followed by a low-intensity magnetic separation. The effects of these parameters such as temperature, carbon powder dosage, holding time and magnetic induction on magnetic separation performance were investigated and the optimal conditions were determined. A concentrate containing 28.65% Cr2O3 was obtained and the total recovery of Cr2O3 was 84.18%.