Improving the efficiency of dry magnetic separation in magnetite ore beneficiation

The paper presents the results of software development aimed to systematize the findings of laboratory and integrated tests of iron ore preparation characteristics using dry magnetic separation and their analysis. Systematization of the findings is based on characteristics of the studied raw materials, i.e. grain-size analysis, chemical, mineralogical and petrographic composition, with reference to the enterprises exploiting the reserves (with account of their industrial types), as well as parameters determining the modes and conditions of dry magnetic separation and technological indicators characterizing its efficiency. The material presented in this paper describes the software project and one of its modules, i.e. ‘Data Generation’, which provides the possibility of downloading, preprocessing and systematization of the test results. The first initial data for the developed software included the laboratory and integrated tests results on the preparation characteristics of the iron ore from the deposits of the Olenegorsk ore field, including the Olenegorskoye, Komsomolskoye, 15 years of October, Kirovogorskoye, Pechegubskoye, for which the efficiency of dry magnetic separation is confirmed.

The mineral and chemical composition of magnetic (tailing fraction) and non – magnetic (clean coal fraction) products from the dry magnetic separation of coal samples with high ash and sulfur contents obtained from Çanakkale Çan lignite (S1) and Manisa Kula Pabuçlu lignite (S2) were investigated in this study. The feasibility of the dry magnetic separation technique for the separation of the minerals from the coal matrix was identified as the function of coal types and particle sizes. The separation technique depends on coal fragments being weakly diamagnetic, while most of the minerals present in the coal are weakly to moderately paramagnetic. Three particle sizes (coarse-, medium-, and fine-sized) of feed lignite and their magnetic and non-magnetic fractions were separated and characterized. The influence of coal type on the magnetic separation efficiency was determined by the recovery of tailing fractions obtained from S1 and S2 lignites. The particle sizes of S1 lignite were quite lower than S2 lignite. When the fine-sized lignite samples from S1 and S2 were used, the recovery of tailing fractions was the highest compared to other sizes. The mineral compositions of S2 lignite include typically mica, smectite (clay mineral), gypsum, kaolinite (clay mineral), pyrite, quartz, and plagioclase. The results showed that the Permroll High-Intensity Magnetic Separation method for high calorific value and low ash content at the medium-sized particle was more efficient for the S2 lignite sample than the S1 lignite sample.

The authors mathematically formulate the efficiency of a magnetic separator for the recovery of magnetite and quartz and assess the effect of atmospheric humidity and consequent ore moisture on losses in efficiency in the separator. They propose a preliminary drying treatment and justify the expenditure of energy this requires by demonstrating that the overall efficiency of the drying and the consequent moisture-free separation process exceeds the efficiency of the separator when moisture is allowed to remain a factor in the process.

The research is aimed at solving the topical problem of enhancing efficiency of iron ore magnetic separation by applying ultrasonic technologies to identify optimal technological parameters of magnetic separation, improving controlled structural parameters of a magnetic separator and pretreating slurry by highenergy ultrasound to clean the ore material surface from fine-dispersed particles of minerals and slime, as well as disintegrate ore aggregates fed to the magnetic separator. The main tasks involve identifying regularities of influence of slurry pretreatment by high-energy ultrasound on properties of iron ore magnetic separation, determining regulations of improving technological and controlled structural parameters of the magnetic separator using ultrasonic methods, developing and substantiating methods to enhance efficiency of iron ore magnetic separation by applying ultrasonic technologies.

This paper describes a comprehensive study that looked at the zircon concentrate produced by Obukhovsky GOK located in Northern Kazakhstan. The study examined the elemental composition and the size distribution of the primary ore and zircon concentrate. The authors examined possible optimization of the concentrate quality, as well as the applicability of dry magnetic separation. The study proved the efficiency of dry magnetic separation for separation of magnetic impurities. The concentration of zirconium in the concentrate increased up to 39 wt.% (53 wt.% expressed as ZrO2), whereas zirconium losses were about 4%. The process of magnetic separation was carried out using the EVS-10/5 magnetic separator by Mekhanobr-Tekhnika at the magnetic induction of 1.7 Tesla and the feed rate of 5 g/min. The authors examined the applicability of the flotation process for the separation of non-magnetic components from Obukhovsky GOK’s zircon concentrate. The study was carried out on the laboratory flotation unit FML 1 by Mekhanobr-Tekhnika with oleic acid used as the flotation reagent. The elemental composition of the ore and concentrates was analyzed using the sequential X-ray fluorescence spectrometer XRF-1800. Techniques were examined that help recover zirconium dioxide from Obukhovsky GOK’s zircon concentrate. Sintering techniques were tested when zircon concentrate was sintered with alkali metal fluorides, soda ash and sodium hydroxide. Sodium hydroxide sintering proved to deliver the best recovery rate, with an almost 100% recovery of zirconium into the solution. The sodium carbonate sintering delivered a 56% recovery, while a 7.5% recovery was reached when sintering with sodium and potassium fluorides.The authors who contributed to this paper include V. I. Sachkov, R. A. Nefedov, R. O. Medvedev, A. S. Sachkova, O. V. Nefedova, D. A. Biryukov.The authors would like to thank the Tomsk Regional Centre of Shared Knowledge for their support of this research work. This research was funded by the Ministry of Education and Science of the Russian Federation under the Governmental Assignment no. FSWM-2020-0028.

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.

The effect of magnetic field strenght on the efficiency of magnetic separation

The removal of highly stable dispersed oil produced during oil recovery processes is very challenging, especially in offshore operations where the limited space does not allow use of equipment with long residence time for the required separation. Using magnetic nanoparticles (MNPs) to remove the dispersed oil from produced water is a promising way to overcome the difficulties that the current treatment technologies face, since the MNPs-attached oil droplets can be quickly and efficiently separated with application of an external magnetic field. The MNPs can be also regenerated and reused, minimizing the generation of hazardous waste. We investigated not only the optimal operating conditions, such as MNP concentration and salinity, but also the mechanisms of MNPs-oil attachment and magnetic separation.We synthesized MNPs in the laboratory with a prescribed surface coating. The MNPs were superparamagnetic with an average individual particle size of ~10 nm. Crude oil content in separated water was reduced by as much as 99.9% using MNP concentrations as low as 0.04 wt% in 5 minutes after MNPs and oil were reacted.The electrostatic attraction between negatively charged oil-in-water emulsions and positively charged MNPs controls the attachment of MNPs to the droplet surface; and the subsequent aggregation of the electrically neutral MNPs-attached oil droplets plays a critical role for accelerated and efficient magnetic separation. The particle aggregation occurred fast, generally within one minute. Thus, the total magnetic separation time was dramatically reduced to as short as 1 second, contrary to that of free, individual MNPs where it took about 36~72 hours, depending on the MNP concentrations.Model calculations of magnetic separation velocity, accounting for the MNP magnetization and viscous drag, show that the velocity of free Amine functionalized MNPs (A-MNPs) increases about 1~3 orders of magnitude as the particles get closer to the magnet depending on the particle size. The smaller the particles, the greater the effect of the magnetic field on the velocity. A typical operating condition would be when the size of the MNPs-oil droplet aggregates is grown to be greater than 360 nm. Then, the total magnetic separation time will be approximately 5 minutes.

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.

Influence of separation chamber shape in dry magnetic separator on the dispersion and separation of multiple magnetites

1. Artificial control of the magnetic properties of rocks (ferromagnetics) is efficient and can be used in industry after suitable development. 2. Cooling of rocks (ferrimagnetics) can be used in magnetic separation both to extract the useful product and for complete separation of ferrimagnetic minerals from the main product when iron is an undesirable impurity.

Image analysis data obtained from scanning electron microscopy provided data for a detailed evaluation of the separation efficiency for various processes involving the beneficiation of particulate materials. A dry magnetic separation by a drum type magnetic separator served as a case study to visualize effects of processing of a skarn ore with a high content of cassiterite as ore mineral (~4 wt%). For this material, iron oxides and silicates are the main gangue mineral groups. Based on the obtained data, partition curves were generated with the help of local regression. From the partition curves, the separation efficiency was evaluated and the relevant particle properties deduced. A detailed analysis of the bias of the quantitative mineralogical data is presented. This bias was monitored and further analyzed in detail. Thorough analysis of feed and products of magnetic separation enabled identification of the most important factors that control losses of cassiterite to the magnetic product, namely the association with iron oxides and particle sizes below ~40 µm. The introduced methodology is a general approach applicable for the optimization of different separation processes and is not limited to the presented case study.

Magnetic separation is an indispensable part of magnetic separation, and the dry magnetic separator can be selected under the condition of water shortage in China to ensure that our country can also be selected under the conditions of lack of some resources. The magnetic separator plays a role in improving the grade of ore, purifying solid and liquid materials, and recycling waste. With the application and development of magnetic separation technology, magnetic separation equipment is constantly updating and replacing, and dry magnetic separation has experienced remarkable technological progress over the past twenty years. There are many new ideas and techniques applied in magnetic separators. So far, dry magnetic separators have developed many different applications for mineral and coal processing, for induction roller magnetic separators for chromite. Cross-belt magnetic separator for removing harmful magnetic particles and paramagnetic particles. The lifting roller magnetic separator is used in the heavy mineral industry to separate garnet from monazite and rutile. Rare earth drum magnetic separator for fine feed dry magnetic separation sorting process and rare earth roller magnetic separator for zircon and rutile in heavy mineral sand industry. These magnetic separators have different applications, and the dry magnetic separator is also moving toward large-scale and easy-to-manufacture.

Mineralogy, physical characterization and magnetic separation performance were investigated for purification of a raw ilmenite concentrate. With the aid of mineral liberation analyzer (MLA) and optical microscope, it was found that (1) most of heavy minerals were distributed in the narrow size fraction, (2) clays and Ti-bearing magnetite needed to be separated prior to magnetic separation, (3) harmful elements such as Ca, P, 232Th and except Mg would’t be enriched in ilmenite concentrate, but enrichment of Mg could’t affect the concentrate quality, (4) Monazite was the main carrier mineral of Th, Ca and P. In addition, the expected yield of rejection and theoretical magnetic inductions were determined by separation tests of heavy minerals and magnetic analysis, respectively. Both the wet and dry magnetic separations were performed focusing on the examination of magnetic induction and it was found that the dry separator has an excellent selectivity against radionuclide bearing minerals. Finally, the dry magnetic separation as a core process technology was proposed to purify the raw concentrate.

ABSTRACTMineral and morphological characteristics of chromite ore strongly affect the separation efficiency while upgrading the low-grade deposits. Usually, chromite ore enrichment is carried out by using gravity separation due to high-concentration criterion between chromite and other minerals. However, chromite ore from Sukinda region, India, is a typical ore body with high iron content in the chromite spinel as well as gangue content in the form of oxide and hydroxides of iron-bearing minerals. So, the separation efficiency reduces by gravity method due to the lower value of concentration criterion. To address this, dry magnetic separation is an alternative approach to separate these iron-bearing gangue minerals from the chromite. This work investigated on the application of different dry high-intensity magnetic separators to separate the chromite grains from ferruginous chromite ore deposits of India. Prior to the separation, two different ore deposits of Sukinda region are subjected to detailed mineral, chemical, morphological, as well as magnetic properties characterization to visualize the separation. Tests confirm the effect of magnetic field strength along with other process parameters that influence the process of the separation of iron-bearing gangue minerals. The results on these separators are related to the influence of mineralogy, process parameters, and magnetic property of minerals, based on the experimental and statistical analysis of the process. Also, effect of desliming of the low-grade deposit prior to the dry magnetic separation is highlighted.