Magnetic preconcentration and process mineralogical study of the Kiviniemi Sc-enriched ferrodiorite

Abstract Scandium is classified as a critical raw material by the European Union. Its beneficiation from various primary and secondary sources is currently being studied under several research and development projects. Due to the geochemical characteristics of Sc, its enrichment to ore grades by geological processes is scarce. Potential new sources are investigated to respond to the expected increasing demand for this rare earth metal. The recently discovered Kiviniemi Sc deposit in Finland represents an igneous occurrence with estimated total resources of 13.4 Mt and an average Sc grade of 163 g/t. The deposit consists of relatively homogeneous ferrodioritic intrusive body with its main unit with ~2.5 ha surface extension. Scandium is mainly incorporated into the lattice of clinopyroxene and amphibole within the main unit. Composite samples from three drill cores from various parts of the main unit were concentrated with a combination of low-intensity and high-gradient magnetic separation. Depending on the feed characteristics, high-gradient magnetic separation reached recoveries between 87% and 92% with 230–310 ppm Sc while removing 35–49 mass percent of gangue minerals, mainly plagioclase and potassium feldspar. Our study provides information on the magnetic preconcentration conditions with process mineralogical details and produced concentrates for further testing according to the suggested processing scheme

Mineralogical and surface chemical characterization of flotation feed and products after wet and dry grinding

Abstract Wet processing after crushing is common practice in mineral processing circuits involving flotation but the need for more efficient water management has increased interest towards dry processing. In this study the effects of both wet and dry grinding on flotation of one sulphidic and one non-sulphidic ore were compared. Bench scale flotation tests were carried out and various microscopic and spectroscopic methods such as FESEM and XPS were used in characterization of flotation feeds and products. Bulk surface charge properties were tested with mass titration. Clear differences in surface properties and flotation results were observed from the wet and dry grinding methods, which encourages further research. Wet grinding was beneficial for the energy efficiency for both ores and promoted the selectivity of flotation particularly with sulphidic ore. The wear of the mill and grinding media seemed more extensive in wet grinding. Dry grinding produced more fine particles tightly attached to the surfaces, caused by the higher surface charge of the dry ground ore especially with non-sulphidic ore

The effect of hydrodynamic conditions on the selective flotation of fully liberated low grade copper-nickel ore

Abstract Low grade sulfide ores are difficult to process due to their composite mineralogy and their fine grained dissemination with gangue minerals. Therefore, fine grinding of such ores becomes essential to liberate valuable minerals. In this research, selective flotation was carried out using two pitched blade turbine impellers with diameters of 6 cm and 7 cm to float copper and nickel. The main focus of this research was to generate optimum hydrodynamic conditions that can effectively separate nickel and copper from gangue minerals. In addition, we investigated the effects of superficial gas velocity, impeller speed, bubble size distribution, and bubble surface area flux on the flotation recovery and rate constant. The results demonstrated that a 7 cm impeller comparatively produced optimum hydrodynamic conditions that improved Cu-Ni recovery and the rate constant. The maximum copper and nickel recoveries in the 7 cm impeller tests were observed at 93.1% and 72.5%, respectively. However, a significant decrease in the flotation rate of nickel was observed, due to entrainment of nickel in copper concentrate and the slime coating of gangue minerals on the nickel particle surfaces

Reduction of fragment size from mining to mineral processing:a review

Abstract The worldwide mining industry consumes a vast amount of energy in reduction of fragment size from mining to mineral processing with an extremely low-energy efficiency, particularly in ore crushing and grinding. Regarding such a situation, this article describes the effects of rock fragmentation by blasting on the energy consumption, productivity, minerals’ recovery, operational costs in the whole size reduction chain from mining to mineral processing, and the sustainability of mining industry. The main factors that influence rock fragmentation are analysed such as explosive, initiator, rock, and energy distribution including blast design, and the models for predicting rock fragmentation are briefly introduced. In addition, two important issues—fines and ore blending—are shortly presented. Furthermore, the feasibility of achieving an optimum fragmentation (satisfied by a minimum cost from drilling-blasting to crushing-grinding, maximum ore recovery ratio, high productivity, and minimum negative impact on safety and environment) is analysed. The analysis indicates that this feasibility is high. Finally, the measures and challenges for achieving optimum fragmentation are discussed

Towards waterless operations from mine to mill

Abstract To respond to the increased demand for commodities, increased volumes of primary ores need to be mined. This could lead to major challenges with water and tailings management since ore grades are low and many mining operations take place in high water stress areas. The current mineral processing methods used are highly water intensive and, consequently, there is increasing interest in finding alternative solutions to produce raw material concentrates using little or no water. Dry separation technologies capable of efficient recovery of commodities are relatively rare and highly dependent on the materials to be separated. Low-grade complex ores require energy-efficient solutions for liberating material. Controlled optimisation of the rock fragmentation chain from blasting to comminution can be seen as a viable option to reduce the need for energy-intensive grinding. Application of pre-concentration methods to remove barren waste prior to grinding, developing cost-efficient and energy-efficient methods for comminution, use of mechanical or chemical pre-treatment methods for modifying the mineral surfaces and replacing water with solvents for leaching are all good tools when considering the change from wet to non-aqueous processing. Nevertheless, considerable multidisciplinary research, along with many new methods and holistic, innovative solutions are required to enable the change

Properties of flash roasted products from low-grade refractory iron tailings and improvement method for their magnetic separation index

Abstract The properties of flash-roasted products from low-grade refractory iron tailings (IGRIT) and the improved method for their magnetic separation index were investigated by the MLA, XRD, iron phase analysis, and magnetic separation test. The results show the siderite and hematite in the IGRIT have been converted to magnetic iron after the flash roasting treatment with a time of 3‐5 s; magnetic iron in roasted products has a monomeric dissociation of 37.20%, and a 75‐100% exposed area of contiguous bodies as rich intergrowth was 29.83%, and that a 32.97 poor intergrowth; moreover, magnetic iron is mainly associated with muscovite and quartz. It is also found that the regrinding-magnetic separation (1500 Oe) treatment of the middling was beneficial to obtain more qualified iron concentrate products. Therefore, roasted products magnetic separation process in the absence/ presence of the middling regrinding-magnetic separation treatment obtains an iron concentrate with 60.10%/ 60.12% iron grade and 72.04%/81.13% iron recovery. The iron concentrate from the magnetic separation process with middling regrinding-magnetic separation can have a 9% higher recovery than the process without middling regrinding-magnetic separation. The work is significant for helping to improve the utilization of IGRIT

Recovering iron concentrate from low-grade siderite tailings based on the process mineralogy characteristics

Abstract Refractory iron ore is often discarded as tailings. This causes a great waste of iron resources. In this paper, the flash roasting-magnetic separation process was designed by combining the magnetic separation process of magnetite and the process mineralogy of iron tailings. The flash suspension roasting effects with 3–4 s roasting time were evaluated by magnetic separation. The MLA results show that the tailings are ground to a fineness of P90 −75 μm, where the distribution of siderite and M/H in the −75 μm particle size is 85.37% and 92.75%, respectively. Moreover, M/H and siderite are mainly associated with muscovite and quartz. This indicates that regrinding for contiguous bodies of M/H and siderite is beneficial for improving the grade and recovery of iron concentrates. The results of the flash roasting-magnetic separation process show that a mixed iron concentrate containing 60.10% Fe with an iron recovery of 81.13% would be achieved after selective grinding and staged magnetic separation of the roasted ore. The result indicates that the flash suspension roasting effects with 3–4 s roasting time are achievable. The study provides an efficient approach for recovering refractory iron from tailings

Reduction characteristics of Kiviniemi ferrous scandium concentrate

Abstract Scandium provides technological advantages particularly in solid oxide fuel cells and aluminum alloys. Potential new sources are investigated to respond to the expected increasing demand of this rare earth metal, which is currently classified as a critical raw material for the European Union. The recently discovered Kiviniemi mafic intrusion in Finland has been estimated to contain a total resource of 13.4 Mt of Sc with an average grade of 163 g/t. At Kiviniemi, Sc is incorporated within the lattices of ferrous silicates. Magnetic separation has been proposed as the first processing step to lower the amount of alkali-bearing diamagnetic minerals in Kiviniemi concentrates. Pyrometallurgical processing is suggested as the second step to decrease the amount of the ferrous oxide component from the concentrate prior hydrometallurgical processing. This study presents the first results of thermogravimetric experiments on pyrometallurgical reduction of the Kiviniemi concentrate up to temperatures of 1350–1500 °C. The aim of the study was to investigate the progression and extent of ferrous oxide reduction in the concentrate and to characterize the properties of resulting Sc-enriched slag and metal. The main reduction stage is initiated at ∼ 950 °C with a sharp increase in the derivative conversion rates between 1050 and 1170 °C and high rates until ∼ 1250 °C. Although complete reduction of FeO is achieved, the segregation of metal from the highly viscous slag will need to be promoted by adjusting the viscosity of the slag prior hydrometallurgical experiments

Slag modification in reduction of Kiviniemi ferrous scandium concentrates

Abstract Several research projects are currently focused on the search for new sources of scandium due to its expected increasing demand in advanced technology applications. The Kiviniemi Fe-Sc-enriched mafic intrusion is a potential primary source for Sc. According to the recent investigations on the FeO component reduction in the Kiviniemi magnetic Sc concentrate at various end temperatures, complete FeO reduction is achieved at the highest experimental temperature (1500 °C). However, efficient separation of metal from the Sc₂O₃-enriched slag is hindered by the high viscosity of the slag. In this study, investigations of the Kiviniemi-type concentrate reduction characteristics are complemented from three perspectives: (1) slag modification with CaF₂ and/or CaO to promote the reduction of the FeO component and metal separation, (2) reduction characteristics of the concentrates with a slightly different modal mineralogy and chemical composition, and (3) description of the main features of the progression of reduction at selected temperatures (950, 1050, 1150, 1250, and 1350 °C) with CaO addition. Both CaF₂ and CaO increase conversion rates at a lower temperature region and promote the separation of metal from the slag. High-temperature behavior of the concentrates used in this study is essentially similar, although the main reduction stage is initiated at a slightly higher temperature for concentrates with less amphibole and a higher amount of nonferrous gangue minerals. Only after the complete decomposition and melting of clinopyroxene and nonferrous minerals of the concentrate, the final reduction of the FeO component from the slag can take place