Crushed Ores Research Articles

Aspects of roller press for the comminution of crushed iron ores

Aspects of roller press for the comminution of crushed iron ores

Efficient segmentation with texture in ore images based on box-supervised approach

Image segmentation methods have been utilized to determine the particle size distribution of crushed ores. Due to the complex working environment, high-powered computing equipment is difficult to deploy. At the same time, the ore distribution is stacked, and it is difficult to identify the complete features. To address this issue, an effective box-supervised technique with texture features is provided for ore image segmentation that can identify complete and independent ores. Firstly, a ghost feature pyramid network (Ghost-FPN) is proposed to process the features obtained from the backbone to reduce redundant semantic information and computation generated by complex networks. Then, an optimized detection head is proposed to obtain the feature to maintain accuracy. Finally, Lab color space (Lab) and local binary patterns (LBP) texture features are combined to form a fusion feature similarity-based loss function to improve accuracy while incurring no loss. Experiments on MS COCO have shown that the proposed fusion features are also worth studying on other types of datasets. Extensive experimental results demonstrate the effectiveness of the proposed method, which achieves over 50 frames per second with a small model size of 21.6 MB. Meanwhile, the method maintains a high level of accuracy 67.8 in AP50box and 47.7 in AP50mask compared with the state-of-the-art approaches on ore image dataset, even better than bounding box tightness prior (BBTP) by 10.4/1.3 on AP50box/ AP50maskmetrics with the ResNet50 as backbone. The source code is available at https://github.com/MVME-HBUT/OREINST.

Computational fluid dynamics investigation of bitumen residues in oil sands tailings transport in an industrial horizontal pipe

Pipeline transport is commonly used in the oil sand industry to convey crushed oil sand ores and tailings. Bitumen residues in the oil sand tailings can be a threat to the environment that separating them from tailings before disposal is crucial. However, low bitumen concentration in the tailing slurry and the complex transport characteristics of the four-phase mixture make the process difficult. This study establishes an Eulerian–Eulerian (E–E) computational fluid dynamics model for an industrial-scale oil sand tailings pipeline. A comprehensive sensitivity analysis was conducted on the selection of carrier-solid and solid-bitumen drag models. The combination of small and large particle sizes (i.e., 75 and 700 μm) and bitumen droplet size (i.e., 400 μm) provided good agreement with field data in velocity profiles and pressure drop. The validated model was subsequently extended to investigate the influence of the secondary phase (i.e., bitumen droplets and bubbles) on flow characteristics in a tailing pipeline. The investigation covered a range of bitumen droplet size (100–400 μm), bitumen fraction (0.0025–0.1), bubble size (5–1000 μm), and bubble fraction (0.0025–0.3) and their influences on the velocity, solids, and bitumen distribution are revealed. For an optimum bubble size of 500 μm, a maximum recovery of 59% from the top 50% and 83% from the top 75% of the pipe cross section was obtained. The present study demonstrates the preferential distribution of bitumen and provides valuable insight into bitumen recovery from an industrial-scale tailing pipeline.

Development and testing of a combined process based on the use of a flat-bottomed hydrocyclone and a multi-frequency screen

The article provides a brief overview of the development of technology and equipment for the preparation of finely disseminated ores of ferrous and non-ferrous metals for further processing. Fine screening processes and equipment for crushed ores are considered, including in combination with centrifugal hydraulic classification. The purpose of the work was to improve hydraulic screening performance and efficiency for crushed ores. In order to optimize the preparation of finely disseminated ores for processing, a combined preliminary hydraulic classification process was developed for crushed ores based on the use of a flat-bottomed hydrocyclone and a multi-frequency screen. A pilot plant was used to test the process. The article contains qualitative and quantitative performance indicators for the hydraulic screening of crushed chromium ore with a particle size of 300–0 μm. The total recovery of all size classes below 300 μm into the undersize of the multi-frequency screen was 86.42 % and the recovery of finer ore classes (below 150 μm) was 91.09 to 92.97 %. The resulting combined process using a flat-bottomed hydrocyclone and a multi-frequency screen improves the total equipment performance, ensures high recoveries of fine classes into the undersize, extends the service life of fine sieves and reduces water consumption for oversize irrigation. This combined process is also recommended for use in hydraulic screening of magnetite concentrates at mining and processing plants in order to improve the iron content, as well as in closed fine grinding circuits in order to prevent overgrinding of valuable minerals and reduce the circulating load on the screens.

Efficient and Lightweight Framework for Real-Time Ore Image Segmentation Based on Deep Learning

Image segmentation approaches have been utilized to determine the particle size distribution of crushed ores in the past decades. It is not possible to deploy large and high-powered computing equipment due to the complex working environment, so existing algorithms are difficult to apply in practical engineering. This article presents a novel efficient and lightweight framework for ore image segmentation to discern full and independent ores. First, a lightweight backbone is introduced for feature extraction while reducing computational complexity. Then, we propose a compact pyramid network to process the data obtained from the backbone to reduce unnecessary semantic information and computation. Finally, an optimized detection head is proposed to obtain the feature to maintain accuracy. Extensive experimental results demonstrate the effectiveness of our method, which achieves 40 frames per second on our new ore image dataset with a very small model size. Meanwhile, our method maintains a high level of accuracy—67.68% in AP50box and 46.73% in AP50mask—compared with state-of-the-art approaches.

Quantification of Lithium and Mineralogical Mapping in Crushed Ore Samples Using Laser Induced Breakdown Spectroscopy

This article reports on the quantification of lithium and mineralogical mapping in crushed lithium ore by laser-induced breakdown spectroscopy (LIBS) using two different calibration methods. Thirty crushed ore samples from a pegmatite lithium deposit were used in this study. Representative samples containing the abundant minerals were taken from these crushed ores and mixed with resin to make polished disks. These disks were first analyzed by TIMA (TESCAN Integrated Mineral Analyzer) and then by a LIBS ECORE analyzer to determine the minerals. Afterwards, each of the thirty crushed ore samples (<10 mm) were poured into rectangular containers and analyzed by the ECORE analyzer, then mineral mapping was produced on the scanned surfaces using the mineral library established on the polished sections. For the first method the lithium concentrations were inferred from the empirical mineral chemistry formula, whereas the second one consisted of building a conventional calibration curve with the crushed material to predict the lithium concentration in unknown crushed materials.

Gypsum utilization on selective reduction of limonitic laterite nickel

The world's nickel demand is increasing, especially with more countries starting to produce battery-based electric vehicles. Currently, nickel is the main element used for the fabrication of Nickel Manganese Cobalt (NMC) batteries. Nickel itself can be extracted from its ore through pyrometallurgical route. Selective reduction of nickel using a selective reducing agent is needed in order to produce nickel with appropriate grade. This study aims to study the possibility of gypsum as a selective reducing agent in the direct reduction process. In this process, laterite nickel ores with nickel content of 1.59% were crushed and classified until the feed particle size was smaller than 50 standard mesh. The crushed laterite nickel ores were then mixed with gypsum and a binder material to undergo briquetting and drying. A bed mix composed of limestone powder and coal was added into the crucible alongside the ore briquettes. Carbothermic reduction was done at 1400 °C for 6 h. The product was then crushed and separated through magnetic separation. The reduced product's chemical composition was analyzed using Scanning Electron Microscope-Energy Dispersive X-Ray and X-Ray Diffractometer. The results indicate that gypsum can provide a selective effect on the direct reduction process of laterite nickel ore. A selective effect that lowers the grade of iron can occur due to the formation of iron sulfides. The use of 12% gypsum was able to produce a product with Ni grade of 4.13%, Ni recovery of 91.81%, and selectivity factor of 5.72. Therefore, based on the results of this experiment, gypsum minerals can be used as a potential low-cost alternative as an additive for nickel selective reduction.

The plant for obtaining an aqueous radon solution

Developing indicator methods to determine the main characteristics of cores extracted from oil-bearing strata presupposes simple, radiation-safe installations of an aqueous radon solution. This study describes such an installation, comprising crushed uranium ores weighing ~45 kg. Herein, we investigated the radon concentration (RC) of water as a function of pumping rate and duration to determine the optimal pumping conditions necessary for achieving a maximum RC in water of ~3 kBq/L.

Short-wavelength infrared reflectance spectroscopy of minerals by supercontinuum illumination and speckle reduction

The advent of broadband supercontinuum (SC) light sources offers an opportunity to improve techniques such as reflectance spectroscopy. In this study, a SC laser, providing a broad spectral bandwidth and higher-intensity light than traditional halogen lamps, is used to illuminate mineral samples in the short-wavelength infrared (SWIR; 1.10–2.35 μm) spectrum. To overcome speckle interference originating from the intrinsic coherence of the SC laser illumination, a rotation-based technique is applied to achieve high signal-to-noise interference-free reflectance spectra of the three minerals studied (muscovite, kaolinite and calcite) and these spectra are compared to reference spectra obtained from the United States Geological Survey spectral library. We report a speckle magnitude, σSpk< 2×10−3 (35 times better than without rotation) resulting in a measurement time <1.6 s with a repeatability of >99%. The benefits and limitations of using SC laser illumination over halogen lamp illumination are discussed with regards to the measurement time, speckle, laser operation safety and cost. The technique described could be used for time-efficient (<1.6 s) in-lab mineral assay of minerals having distinct SWIR absorption features or developed for real-time (within few milliseconds) on-conveyor mineral assay of crushed ores.

Experimental study of sulfuric acid effects on hydro-mechanical properties of oxide copper heap soils

Several mechanisms contribute to changes in the performance of oxide copper heaps. These include physical, biological, chemical and thermal interactions between sulfuric acid and the formation of soil particles. A series of experimental studies was conducted by simulating the column leaching process in the laboratory. The leaching of selected gravel and crushed copper oxide ores from two copper mines was carried out to measure their permeability and strength. The influence of effective parameters on gravel clogging was studied and the clogging coefficient was estimated with time. Furthermore, the ratio of particle reduction (RPR) caused by acid seepage was evaluated and an equation for the internal friction angle of ore particles over time was generated. The present study shows significant reductions of gravel permeability (28% after five months leaching) and friction angle of ore particles (25% after eight months leaching). The effects of sulfuric acid flow on the hydro-mechanical properties of oxide copper heap soils could enhance the accuracy of slope stability design and drainage layers design in industrial heap leaching systems.

Effect of moisture content on the flowability of crushed ores

In many mining and industrial processes where large quantities of non-degrading bulk materials such as crushed ores are handled, silos, hoppers, stockpiles and chutes are widely used because they are economical and reliable (if properly designed and operated). However, they are not free of trouble and may experience flow problems such as arching, ratholing, erratic flow, limited storage capacity, limited discharge flow rate, caking, segregation and/or flooding. Moisture content and fine particles significantly affect the flowability of most ores, increasing their cohesive strength and turning them more prone to these problems. The purpose of this article is to highlight a proven, scientific method that can be utilized to ensure reliable storage, flow and discharge of bulk solids in these equipment based on Jenike’s flow-of-solids theory and laboratory testing. Knowledge of the flow properties of the material handled provides a design basis to ensure mass flow, avoid arching and prevent the formation of “ratholes”. The effect of an increase in water content of the ore is discussed with experimental results.

The Art of Talc Flotation for Different Industrial Applications

Talc has found a steadily increasing number of uses such as cosmetics, steatite and cordierite ceramics, for pitch control in the paper industry and as a reinforcing filler in rubber, etc. In this research, the amenability of some Egyptian carboniferous finely disseminated talc ores to beneficiation by flotation was investigated on laboratory scale. The original talc sample is characterized by low MgO content (25.40%), low SiO2 (45.71%), high CaO content (6.32%) and high L.O.I. (11.35%), indicating its low grade. Attrition scrubbing of the crushed ores was found to be an unconventional process, not only for fine talc production, but also for proper separation of the harder carbonaceous gangue. Talc pre-concentrates, less than 0.074 μm, were prepared by attrition scrubbing in the laboratory having 8.40% L.O.I. with a yield reaching 74.70%. Cleaner talc concentrate with L.O.I. content averaging 6.70% was obtained by flotation in the presence of Aerofroth 71 with a yield reaching 64.71%. This was relatively improved by the use of a selective (quaternary amine) talc collector and in presence of a selective carbonate depressant (soda ash). Flotation of the fine ground talc (less than 22 μm) produced a talc concentrate assaying 6.90% L.O.I. with a yield recovery of 62.91%. However, different talc concentrates obtained by just natural floatability or by the use of small dose of Aerofroth 71, or by the application of quaternary amine in presence of carbonate depressant, satisfy the requirement of paper coating, ceramics production, functional filler, and pharmaceuticals applications. Tailings could also be used in carpets, roofs, and tiles production industries.

Understanding the Agglomeration Behavior of Selected Copper Ores Using Statistical Design of Experiments

The drum agglomeration of two different crushed copper ores (I and II) has been optimized using Taguchi's L16 (45) orthogonal array design to determine the optimum conditions for maximizing the average agglomerate size and minimizing the amount of fines. The effects of controllable operating factors including moisture content (ore I: 9.6–11.1%; ore II: 12.8–14%), retention time (2–4 min), drum speed (15–45% critical), drum load (ore I: 13–32%; ore II: 6–24%) and acid concentration (6.5–90 g/L) on the performance of the agglomeration process were studied. For ore I, the maximum average agglomerate size and minimum percent fines (−1 mm) occurred under the conditions: drum load (22.75%), moisture (10.35%), time (4 min), drum speed (30% critical), and acid concentration (41 g/L), whereas for ore II, the same conditions occurred under the drum load (18%), moisture (13%), time (3 min), drum speed (30% critical), and acid concentration (30 g/L). Under the conditions studied for ore I, the most effective parameter for maximizing average agglomerate size and minimizing the amount of fines was found to be drum load. For ore I, time and acid concentration had a measurable effect on maximizing average agglomerate size, whereas moisture had a statistically significant effect on minimizing the amount of fines. For ore II, the most effective parameter for maximizing average agglomerate size and minimizing the amount of fines was found to be acid concentration. Time had a measurable effect on maximizing average agglomerate size, whereas the other variables did not affect the responses significantly for ore II.

Infrared thermography: An approach for iron ore gradation

There are insufficient high-grade iron ores currently being mined to meet world demand for steel production. In order to meet raw material demand in India, lower grade ores with high alumina contents are being crushed and beneficiated, mainly by gravity techniques requiring water. However, the scarcity of water in the mining areas warrants the development of some dry gradation techniques for iron ores so that the inferior ore specimens can be rejected in order to improve the grade of the concentrate. The present gradation of ores by mineralogical/chemical methods is time-consuming and cumbersome. This paper presents an Infrared (IR) thermography-based non-invasive technique for the faster gradation of iron ores, taking into account the variation in thermal absorptivity of the ore constituents. Iron ore samples from the Joda, Noamundi and Barsua mines, with Fe contents ranging from 52 to 67wt.%, were selected and crushed to around 10mm particle size. The crushed iron ores were uniformly heated using a microwave oven, for a time period sufficient to create a difference between the ore particles in the extent of their respective infrared emissions. The thermal images of the heated particles were captured by IR thermography and the peak temperature of each ore particle was obtained from the thermal profile. A computer program was developed for ore gradation based on the peak temperature of each ore particle which corresponds to its iron content. A threshold was selected through chemical verification of the ores and accordingly the ores were categorized as high-, medium- and low-grade.

Performance Quantification of Applicators for Microwave Treatment of Crushed Mineral Ore

Exposure of crushed mineral ores to microwaves at high power density (~109 to 1011 W/ m3abs) and for short exposure times (<0.1 s) induces grain boundary fracture around the grains of the value minerals at economically viable energy inputs (~1 kWh/t). In subsequent processing steps, liberation of the value minerals is enhanced, improving the efficiency of the process. In this paper the performance of transverse E-field applicators for the continuous treatment of 30 t/h of crushed ore was quantified using damage maps. These provide the amount of microwave-induced grain boundary damage and the fraction of the load treated as a function of input power and throughput. The damage maps are created by combining the outputs from thermal stress simulations (for the determination of thermal damage) with those from electromagnetic simulations (for the determination of the 3d dissipation of power in the load). The results are to be used to select the optimal applicator structure and operating parameters (bed height and speed) for a given ore. Results from two applicator configurations for a coarser and finer-grained galena-calcite ore are used to exemplify the results. It is shown high the texture of the ore significantly reduces performance in terms of achievable throughput and required energy input. It is also shown that sub-optimal electromagnetic design also results in reduced throughput and increased energy requirement.

Hydrodynamic behavior of heap leach piles: Influence of testing scale and material properties

The dynamics of solution, soluble species, and gas in increasing scales of heap leaching apparatus were quantified with tracer tests to explain differences in their gold leaching behaviors. The tracer methods included tracer injection in the feed solution and monitoring soluble species during rinsing. Hydrodynamics of the heap systems were evaluated during (1) the scale-up from a 350 kg column to a 55 tonne crib to a 6300 tonne heap, and (2) the change in ore properties from run-of-mine to crushed to agglomerated ore in 55 tonne cribs. The tracer data was interpreted by the Levenspiel compartment flow model that considers a packed bed as a black box filled with ore, air, and moisture, the latter occurring as active flow, by-pass flow, plug flow volume, well-mixed volume, and stagnant/dead volume. This model was useful as a diagnostic tool but would not be a predictive tool. It was established that gold recovery could be correlated to the amount of stagnant solution in the system. Columns and cribs that achieved excellent gold recovery had as little as 0% to 18% of the solution retained in a stagnant form. The 6300 tonne heap had poor gold recovery and contained a significant stagnant volume (57% of the total solution retained in the heap). The proportion of stagnant solution was proportional to the proportion of fines in the ore and the lack of structural support (e.g. column walls) in the heap, the latter translating into a higher bed density. In contrast to the wide distribution of particle size in the run-of-mine and crushed ores, the agglomerated ore was more uniformly-sized, which led to a lower proportion of stagnant solution. The agglomerated ore had a lower bulk density of 1.7 t/m 3 ( vs 2 t/m 3) and a lower proportion of stagnant solution 0% ( vs 88%). Gold extraction from the agglomerated ore was aided by the air available in the pores, while good solution transport out of the packed bed was attributed to the absence of stagnant zones. Tracers proved to be simple and effective to quantitatively diagnose the inner workings of heap leaching systems of various scales. A narrow particle size distribution, a low fines content, and a low bed bulk density were keys to achieving good solution, solute, and gas dynamics, hence high gold recovery.

Environmental Mineralogy of the Kursk Iron Ore Deposit

The development of new technologies is one of the most effective ways to solve environmental problems related to ore-dressing. Complex mineralogical investigations are able to help in improving this process. In collaboration with researchers from the IPKON institute, we have developed an electrochemical method to improve the properties of crushed ores prepared for the wet magnetic separation. This article studies the samples before and after application of the electrochemical method. Surfaces of mineral grains investigated by the scanning electron microscopy show differences in flocculation. Measured polarization curves showed unequal electrochemical processes on surfaces of magnetite, hematite, and martite particles. X-ray analysis and Mössbauer data also confirmed the changes in compositions of the ores before and after using the electrochemical method. Magnetic properties of the studied species to be compared before and after the application of method showed relevant increase in parameters such as magnetic viscosity (Svo), breaking saturation field (Hcr), magnetic susceptibility (χ), and specific magnetization (Is).

The history of the United States cent revealed through copper isotope fractionation

Copper isotope fractionation in United States cents traces changes in the source of copper and identifies historical events. Application of copper isotopes as a geochemical tracer requires consistent isotopic signatures of the ores and refined metals. Overlapping isotopic signatures of crushed ores, chalcocite and refined metal extracted from Morenci, Arizona indicate modern mining processes that produce distinguishable single ore deposit geochemical signatures. The coincidence of copper isotope ratios in metals and ore deposits also exists within the United States cents analyzed here. Specifically, historical records confirm two different sources for copper in cents from 1800 through 1867. The copper isotope composition of the 1828, 1830, 1836, 1838 and 1843 cents coincides with the Cornwall ores of England, and cents post 1850 (1859, 1862) correspond with the Michigan ores of the United States. Three of the thirty-six post 1867 cents measured possess fractionated copper isotope ratios and indicate the change in source of copper for the United States cent.

Techno-Economic Considerations in the Commercial Microwave Processing of Mineral Ores

Microwave heating of mineral ores had previously been shown to result in process benefits such as reduced strength and improved mineral liberation, but the economics of the process were not attractive and no attention was given to feasible scale up. This paper provides an overview of the multi-disciplinary approach that has been required to address these failings and develop the technology to pilot scale. Thermal stress simulations show that the operation at high power densities and short residence times is the optimal operating strategy. Experiments using high power densities (>109 W/m3 absorbing phase) and short residence times (˜ 0.1 s) were used to confirm that the benefits can now be achieved at economically viable microwave energy inputs (˜ 1 kWh/t). In order to design applicators, reliable measurement of effective microwave properties of crushed ores is required. A new method has been developed to extract dielectric properties when the sample thickness is a multiple of half a guide wavelength at some point in the measurement band. Finite difference time domain modelling has been used to design and simulate applicators. A transverse E field applicator with a reflection compensating step has been developed, and a unit with a capacity of > 10 tons/h is being tested. Preliminary economic analysis shows that the overall cost of the process will be between US$ 0.16–0.85 per ton of ore.

Path Generation for Autonomous Locomotion of Articulated Steering Wheel Loader

A wheel loader is the major machine that has been used in several fields for scooping, carrying, and loading of crushed ores. Recently, automation of the wheel loader task has been receiving considerable attention. This article describes a path‐generation method for autonomous locomotion of the wheel loader. From the viewpoint of locomotion stability and ease of control, it is necessary for the path to be smooth and easily calculated. In order to satisfy these conditions, a path‐generation method using a clothoid curve is proposed. The change in curvature of the clothoid curve is continuous and is proportional to the length of the curve. Therefore, the clothoid curve provides continuous change of the steering angle. Furthermore, an interpolation method between the initial and target points of the wheel loader is proposed in this study, which consists of the clothoid curve segment and a straight‐line segment. A V‐shaped curve including the backward path and the forward path is also generated, taking into account the avoidance of rapid turning.