查看更多>>摘要：? 2022 The Author(s)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.
查看更多>>摘要：? 2022 Elsevier LtdThe current study investigates hydrogen reduction of low-grade iron ore (～37 % Fe) containing dispersed bands of hematite and jasper/quartzite phases. Gaseous hydrogen reduction is carried out at isothermal conditions in a custom-made tubular furnace, followed by magnetic separation. The reduction temperature (300–600 °C), time (30–90 min), particle size (0.5–3.3 mm), and hydrogen flow rate (0.5–1.5 LPM) were optimized by statistical design of experiments to maximize the saturation magnetization, degree of reduction and metallization. Complete reduction of hematite was achieved in 2 h at 600 °C; however, the separation of quartz from reduced ferrite was inefficient evidenced by the lower saturation magnetization. The association of impurities with hematite does not affect the reduction rate; however, the trapped quartz particles in the reduced phases deteriorate the magnetic separation efficiency. Temperature and time synergize the reduction rate, improving reduction and metallization degree; meanwhile, flow rate and particle size have minimal effect. Reduction below 450 °C restricted the reduction to magnetite, and the optimal conditions; 600 °C, 60 min, 0.5 LPM H2, and 3.3 × 2 mm particle size yielded ferrite concentrate possessing saturation magnetization of 134.6 emu/g (68 % FeM) with 97.9 % DOR, 88.8 % DOM and 47.3 % yield. The reduction of hematite results in generation of micro cracks and porous morphology of the ferrite. Iron oxide reduction follows the Fe2O3 → Fe3O4 → Fe, evidenced by the absence of wustite (FeO) or fayalite (FeO.SiO2) phases in the product. The ferrite particles form a fused and porous layer trapping the silica particles.
查看更多>>摘要：? 2022 Elsevier LtdIn the mining industry, mineralogical characterization using automated mineralogical devices (scanning electron microscope and reflected optical microscope) has become inescapable, especially for geometallurgical purposes. Mineralogical characterization using these techniques requires correct sampling of the material to obtain representative polished sections. This technical note proposes a method to decide the appropriate number of polished sections which need to be prepared according to the size class considered to achieve enough representability. To illustrate this method, two sampling protocols (at grain form for textural purposes and powder form) of a theoretical typical sulfide ore including a sizing preparation, are presented with the computation method of the variance of the fundamental error related to sampling. The sampling protocols are an adaptation of safety lines derived from the sampling theory of Pierre Gy and need to be adjusted according to the intrinsic properties’ knowledge of the material considered. The method can be very useful to better anticipate the lack of representativity of mineralogical data provided by automated mineralogical devices linked to the sampling preparation.
查看更多>>摘要：? 2022 Elsevier LtdCopper–ammonium species were introduced in this work to improve the surface sulfidization and flotation performance, and the mechanism was revealed by solution composition determination and surface measurements. Results showed that copper–ammonium species exhibited superior activation performance compared to individual copper ions, and more copper ions were transferred onto the smithsonite surface to increase the mineral surface reactivity with sulfide and xanthate species. Compared with the individual activation system of copper ions, a superior sulfidization of smithsonite was obtained in the synergistic activation system of copper–ammonium species. The activation of smithsonite surfaces with copper–ammonium species not only increased the content of copper sulfide species, but also enhanced the activity of sulfidization products on the surface of smithsonite. Accordingly, a greater amount of xanthate species adsorbed on the surface of smithsonite, and the surface hydrophobicity significantly was enhanced after smithsonite was activated with copper–ammonium species. Compared with treatment in the direct sulfidization system, the flotation recovery of smithsonite increased by approximately 30% under the optimum flotation conditions after treatment in the synergistic activation system of copper–ammonium species. The research results provide a potential technology for promoting the efficient recovery of zinc oxide minerals through sulfidization xanthate flotation.
查看更多>>摘要：? 2022The recovery of chromite from the tailings streams of South African UG2 platinum concentrators adds significant financial returns to these operations. Whilst the coarser fractions are amenable to processing by physical separation, the focus is now also on the recovery of fine (typically ?75 μm) chromite by flotation. This paper describes the results of a series of physical separation, and chromite bench flotation tests that have been carried out at acidic and natural pH respectively, on UG2 tailings from Pilanesberg Platinum Mines (PPM) on the western limb of the Bushveld Complex in South Africa. The objective of the work is to find a route that would best produce, from a feed assaying around 18 % Cr2O3 and with 50 % of the chromite in the ?38 μm fraction, a concentrate of at least 40 % Cr2O3 and an overall yield of more than 13 %. Results showed that shaking tables and wet high intensity magnetic separation (WHIMS) alone were not capable of upgrading the tailings to the target grade. However, flotation tests at a pH of 2.5 on a sample that was deslimed at 10 μm by cycloning, as well as a sample that was screened at 25 μm and subjected to WHIMS, demonstrated that a product assaying 42 % Cr2O3 could be attained at yields between 8 and 11 %, with recoveries ranging between 19 and 27 %. The results highlighted the importance of desliming prior to flotation, in reducing the dosage of the Flotinor V-2711 collector by more than 60 %. Subsequent flotation tests at natural pH on hot tailings samples with two stages of cleaning showed good upgrading, where a feed grade of 16.1 % Cr2O3 after desliming was converted to a concentrate of 29.4 % Cr2O3 at a yield, based on deslimed feed, of 28.6 % and a recovery of 52.4 %. The overall upgrade ratio in this case of 1.83 was slightly lower than those of the acidic tests (i.e., 1.87 and 2.31 respectively) but also at lower yields (28.6 % vs 33 %) and recoveries (52.4 % vs 62 %). Further work is underway to investigate various flowsheet options, including the flotation of fines spiral concentrates, staged collector addition to the cleaning stages, and froth washing.
查看更多>>摘要：? 2022Mineral slurries can have very complex rheology which may not be evident in bench-scale mixing tests. On scale-up to large industrial stirred tanks, an unexpected stagnant layer sometimes forms at the surface. We hypothesize that this occurs due to build-up of yield stress when the fluid is at rest. This behavior can cause problems on scale-up, where insufficiently mixed regions of the tank contain a much larger volume of fluid and the residence time in these regions can be much longer than at the bench scale. To study this effect, a method for continuous torque measurements was developed to quantify rest time effects at the bench scale. Nickel laterite slurries (NLS) with a broad range of solids concentration (25.2–71.8 wt%) were used to test this new method. Concentric cylinder viscometry and vane rheometry were also used to measure the behavior of the test sample. Evidence for a complex mechanism of network build-up for rest times of two minutes and longer was found. Moreover, it was found that 45 wt% is the upper limit for assuming behavior which approximates Newtonian rheology in this nickel laterite slurry sample. Solids concentration greater than 60 wt% showed rapid build-up of yield stress and thixotropic behavior. The rest time experiments validated the scale-up hypothesis. The slurry concentration at which non-Newtonian behavior appears is in accordance with other rheological investigations of nickel laterite slurries.
查看更多>>摘要：? 2022 Elsevier LtdThe efficient separation of fluorite and calcite is a challenging task in the field of mineral processing because of their similar chemical and physical properties. In this research, octylamino-bis-(butanohydroxamic acid) (OBHA) was introduced as collector into a flotation system comprising fluorite and calcite, and the separation of fluorite and calcite was realized in the absence of any depressants. ζ potential, FTIR, XPS measurements and DFT calculations were performed to investigate the mechanism for the selective adsorption of OBHA. The results indicate that the hydroxamic acid group of OBHA account for the adsorption process, and the adsorption of the hydroxamic acid group on fluorite was much stronger than that on calcite surface.
查看更多>>摘要：? 2022 Elsevier LtdThis study aims to understand the agitation effect on particle dispersion and separation and provide guidance in the optimized use of the agitation effect in an agitated reflux classifier (ARC) to promote the separation performance. Two statistical models were developed to analyze differences in various factors of Sb grade and recovery of concentrate. Results indicated that the agitation effect is an excellent auxiliary factor that can replace some functions of other traditional factors to improve the Sb grade at a low cost of Sb recovery loss. Sieve analysis results of the pretreated products showed that on basis of 16 L/h fluidization rate, adding agitation of 350 rpm can increase the concentrate grade of ?0.045 + 0.023 mm particles from 2.65 % to 3.85 %, while the recovery is only reduced by 18.05 % which is much lower than the recovery loss obtained by increasing the fluidization rate. And compared with feed concentration, the agitation effect was more advantageous when dealing with coarse particles of-0.15 + 0.045 mm. In the range of 0 to 350 rpm, agitation effect could improve concentrate grade with little negative effect on the recovery of coarse particles. Fluidized bed analysis was utilized to explain these phenomena. Results showed that the agitation effect could well adjust the density distribution of the fluidized bed in the ARC. It lifted particles to a high area, reduced the density of the suspension in conical section of the ARC, improved particle dispersion, and reduced mechanical entrainments. Meanwhile, particles lifted by mechanical agitation increased the bed density of the vertical section and enhanced the ability of the fluidized bed to separate particles according to their density.
查看更多>>摘要：? 2022 Elsevier LtdAs a potential ore resource to produce alumina in industry, the complex symbiotic relationship between the aluminum-, silicon- and iron-bearing minerals in the high-silicon bauxite and severe desilication reactions during digestion process restrict its application. In this paper, a novel zero-waste process consisting of a roasting pretreatment and two-stage leaching was proposed to comprehensively utilize the high-silicon bauxite, and the phase transition mechanism and leaching properties of the roasting solid were systemically studied. When the roasting temperature is over 310 °C, the diaspore and kaolinite in the bauxite lose the crystal water, and gradually transform to alumina and metakaolin respectively. As the roasting temperature rises to above 950 °C, the metakaolin decomposes to an amorphous aluminosilicate phase and silica. The crystallinity of decomposed alumina and silica increases with the increase of roasting temperature and duration, but the excessive temperature and duration deteriorate the extraction property of the roasted bauxite. The optimal roasting conditions for the atmospheric-pressure leaching of silica and high-pressure leaching of alumina are 1050 °C for 30 min, and the corresponding extraction efficiencies of Al2O3 and SiO2 are above 94 % and 88 % respectively. The Fe2O3 and Na2O contents in the final leaching product are 55.23 % and 0.23 %, and can be directly used as iron concentrate in the ironmaking process.
查看更多>>摘要：? 2022 Elsevier LtdOnline identification and sorting for coal and gangue has always been a hot issue in the field of coal processing intelligence. Existing research has focused on materials with particle sizes below 300 mm, and its front-end algorithms are dedicated to achieving image classification or object detection. The lack of detailed shape information of materials in these methods enables them to be not suitable for sorting oversized gangue. In this work, we proposed a synchronous detection-segmentation method for oversized gangue, which was implemented as a joint network based on the multi-task learning theory. The loss function of joint network and the feature interaction channels between the shared encoding module and the parallel decoding branches were designed to efficiently achieve object detection and semantic segmentation for oversized gangue. The proposed method has been evaluated in a comprehensive manner using huge amounts of coal-gangue images taken in an actual production process. The superiority of our joint network based on multi-task learning was verified by comparing several experimental results of them with the classical single-task networks. The issue of convergence synchronization between the multi-task branches was investigated to further optimize the segmentation results. Meanwhile, the effectiveness of the proposed method in improving the sorting capability of the manipulator was explained through a qualitative analysis for a case of sorting oversized gangue.
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