The Sungun copper-molybdenum operation in Iran uses a typical copper-molybdenum flowsheet to produce separate copper and molybdenum concentrates through flotation and regrinding of the rougher concentrates arising from the primary circuit. This site was used as a case study limited to the feed and products of the copper-molybdenum separation circuit, in which process mineralogy might improve the quality of the molybdenum concentrate thorough diagnostic analysis of key flowsheet streams. The undesirable presence of copper in the molybdenum concentrate was identified as a key focus for the investigation by process mineralogy, which has a history of successful process diagnosis. This is because it develops information on minerals, which is far more informative than chemical assays alone. Together with the assays, the mineralogical data inform the investigator of the type and quantity of minerals present, their state of liberation and textural associations, and metal recovery.

A key finding was that the appearance of chalcopyrite in the molybdenum concentrate was due to the presence of a chalcopyrite-pyrite texture that avoided the chalcopyrite depression in the molybdenum circuit because of suitable pyrite flotation conditions. Recovery of liberated pyrite to this concentrate also diluted the molybdenum concentrate. The open-circuit format of the regrind circuit also contributed to the unnecessary production of ultrafine particles. This flaw expressed itself as ultrafine losses of molybdenite to the flotation tailings.

Knowing the remaining useful life of grinding mill liners would greatly facilitate maintenance decisions. Now, a mill must be stopped periodically so that the maintenance engineer can enter, measure the liners’ wear, and make the appropriate maintenance decision. As mill stoppage leads to heavy production losses, the main aim of this study is to develop a method which predicts the remaining useful life of the liners, without needing to stop the mill. Because of the proven ability of artificial neural networks (ANNs) to recognize complex relationships between input and output variables, as well as its adaptive and parallel information-processing structure, an ANN has been designed based on the various process parameters which influence wear of the liners. The process parameters were considered as inputs while remaining height and remaining life of the liners were outputs. The results show remarkably high degree of correlation between the input and output variables. The performance of the neural network model is very consistent for data used for training (seen) and testing (unseen).

The process of grinding is complex with many factors affecting the result. As the composition of the ore fed to the concentrator varies, implying changes in grindability, the optimal operation conditions for a pebble mill will also vary. In an attempt to increase the understanding of charge dynamics, a series of statistically planned experiments were done in a pilot-scale pebble mill with differing charge types. This pebble mill is equipped with an in-mill sensor, which measures the deflection of a single lifter as it passes through the mill charge. The experimental setup was a factorial design with two factors; two levels of magnetite pebbles content and three different size distributions. The experiments show that there is an advantage to keep the magnetite pebbles proportion as high as possible. This will increase the power consumption and maximum deflection of the lifters, but at the same time increase the production of <45 μm material, the grindability and the pebbles consumption. A pebble size fraction 10–35 mm improves the grindability the most and the amount of <45 μm material. It is strongly suggested that the 10–35 mm and 100% magnetite pebbles fraction should be tested in a larger scale pebble mill to confirm these findings.

The size distribution as a function of weight of particles is an important measure of product quality in the mining and aggregates industries. When using manual sampling and sieving, the weight of particles is readily available. However, when using a machine vision system, the particle size distributions are determined as a function of the number of particles. In this paper we first show that there can be a significant weight-transformation error when transforming from one type of size distribution to another. We also show how the problem can be overcome by training a classifier and scaling the results according to calibrated average weights of rocks. The performance of the algorithm is demonstrated with results of measurements of limestone particles on conveyor belts.

Starch is a traditional depressant for hematite beneficiation by cationic reverse flotation separation from silicates. Alkali or thermal gelatinization must be used to prepare starch and promote its dissolution in water. In industry, gelatinization is typically carried out using sodium hydroxide at room temperature at different starch/NaOH mass ratios (SNMR). Surprisingly, no investigation has systematically studied the optimum SNMR for boosting hematite depression. This work examined the influence of starch gelatinization under various SNMR (3:1, 5:1, 7:1, and 9:1) on hematite depression (at pH = 10.5, 22 °C) by exploring flotation response (R), contact angle (θ), induction time (τ), hydrodynamic diameter (dH) of starch macromolecules, total energy of interaction starch/hematite (GTOT), based on its two components: the attractive Lifshitz-van der Waals energy (GLW) and attractive/repulsive electrostatic energy (GEL). Flotation test results indicated that SNMR = 5:1 promoted the lowest hematite recovery (14.8 %), coupled with the highest induction time (τ = 55 ms) and the lowest contact angle (θ = 11°). The hydrodynamic diameter (dH) of macromolecules in solutions prepared under different SNMR was determined by Dynamic Light Scattering, showing three peaks: amylopectin (350 < dH < 420 nm), amylose (50 < dH < 100 nm) and debris from gelatinization (dH ∼ 5000 nm). Since the latter only occurred in solutions prepared under SNMR of 7:1 and 9:1, deficient hematite depression might be caused by incomplete gelatinization. As amylopectin is the starch component that is responsible for its depressant ability, larger amylopectin macromolecules (dH = 411 nm) found in solutions prepared at SNMR = 5:1 contrast with smaller macromolecules (dH = 353 nm) produced at SNMR = 3:1. Considering starch macromolecules as a sphere, and hematite&apos;s surface as a plane; GLW, GEL, and GTOT were calculated in function of the sphere/plane separation distance (2 nm < H < 20 nm). GLW was determined based on the assessment of the Hamaker constant of the starch/water/hematite system (2.9 × 10−20J < A132 < 3.3 × 10−20J), whereas GEL was determined based on the zeta potential of starch (−2mV < ζ1 < −4mV) and hematite (ζ2 = −29 mV). GTOT for starch gelatinized at SNMR = 5:1 (−502.9 × 10−21 J) is greater than GTOT for starch prepared at SNMR = 3:1 (−468.8 × 10−21 J) and SNMR = 7:1 (−469.0 × 10−21 J), at a confidence level of 95 %. These results corroborate the more intensive hematite depression by starch prepared at SNMR = 5:1 compared to the other values explored by this study.

Due to environmental issues and the restrictions imposed on mineral flotation separation, the use of biodegradable and environmentally friendly reagents has gained widespread international attention. So far, several investigations have been conducted regarding the eco-friendly flotation separation of iron oxide ores for moving toward sustainable development and cleaner production. Yet, no critical review is specified on the green and eco-friendly depression reagents through their reverse flotation beneficiation. Therefore, this study will comprehensively discuss the previously conducted works in this area and provides suggestions for future assessments and developments. This robust study explored various adsorption aspects of natural-based depressants (polysaccharide-, polyphenolic-, and lignosulfonate-based) on iron oxide minerals (mainly hematite) to create a possible universal trend for each biodegradable depressant derivative. The laboratory and industrial experiments indicated that these depressants (except lignosulfonate-based) could selectively depress hematite at alkaline pHs and enhance its reverse flotation separation from their gangue phases (especially silicates as the main gangue phases). Although these eco-friendly depressants showed promising metallurgical results, several gaps still need to be addressed, notably in surface analyses and their adsorption mechanisms.

This work presents a dynamic model for prediction of flow and output size distribution of cone crushers. The main purpose of the model is for simulation of closed-loop control using the Closed Side Setting (CSS) and the eccentric speed (ω) as manipulated variables. The idea of modeling crushers as cascaded zones is adopted throughout this work. The capacity, the length, the stroke, and the compression ratio of each zone are taken into consideration. Simulation results are presented in the form of the Crusher Performance Map (CPM) and the dynamic response for production of different size classes to steps input in ω and CSS. The simulations also include operation with recycling of oversize output, as well as the input of mixed materials. As an example, closed-loop control of the ratio of the large-size output to the total size output was simulated.

Removal of impurity elements in copper metallurgy is one of the major problems encountered today since pure copper ore reserves are becoming exhausted, and the resources of unexploited ores often contain relatively high amounts of impurity elements like antimony, arsenic, mercury and bismuth, which need to be eliminated. The present work is aimed at pre-treating a tetrahedrite rich complex sulphide concentrate by selective dissolution of the impurities, therefore, upgrading it for pyrometallurgical processing. To accomplish this, dissolution of antimony and arsenic by an alkaline sulphide lixiviant from the concentrate were investigated. The lixiviant proved selective and effective to dissolve these impurity elements from the concentrate with good recoveries. Further investigations on the factors influencing the leaching efficiency of the lixiviant were studied. The parameters considered were sulphide ion and hydroxide ion concentrations, mineral particle size, reaction temperature and leaching time. Analysis of the leach residue indicates that copper content of tetrahedrite has transformed into copper sulphides with the average chemical formula Cu1.64S. The grade and economic value of the concentrate were improved greatly after sulphide treatment, and therefore, suitable as a feedstock for smelting. The impurities have been reduced to low levels which are tolerable in the smelting furnace and consequently reduce both the treatment and environmental problem encountered when such concentrate is processed pyrometallurgically.

The technical feasibility, on laboratory scale, of hydro- and electrometallurgical processes of recovering metallic antimony from an antimony-bearing copper sulphide concentrate has been investigated. The influence of Na2S concentration, temperature and solid concentration was studied during the leaching test while the effect of current density, Na2S concentration, electrolyte temperature and NaOH concentration on antimony electrowinning from alkaline sulphide solutions was investigated. The leaching results showed that antimony dissolution is strongly dependent on the concentration of the leaching reagent as well as the leaching temperature. The antimony content in the concentrate was reduced from 1.7% to less than 0.1% Sb which is desirable for copper metallurgy. Cathode current efficiency is one of the important parameters to evaluate the performance of an electrolytic process. It is revealed in this study that current efficiency of antimony deposition from sulphide electrolytes is highly dependent on the concentration of sodium hydroxide and the current density used. The results illustrate that the combined effect of increasing anode current density (which was 10 times higher than the cathode current density) and NaOH concentration enhanced the current efficiency of the electrolytic process. It was demonstrated that excess free sulphide ions impacts the current efficiency of the process detrimentally. An integrated hydro-/electrometallurgical process flowsheet for antimony removal and recovery from a sulphide copper concentrate was developed.

Antimony electrowinning from synthetic alkaline sulphide electrolytes has been studied in a nondiaphragm electrolytic cell. The electrodes were constructed in such a way that the anode produces ten times higher current density than the cathodic current density to promote sulphide oxidation to sulphate at the anode; and simultaneously decreasing the tendency of hydrogen evolution at the cathode. The result revealed that at an anodic current density lower than 1500 A/m2, minute amounts of sulphate ions were formed but when the anode current density increased beyond 1500 A/m2, sulphate formation was promoted. The initial molar concentration ratio between hydroxide and free sulphide ions should be ≥ 10.3 to avoid thiosulphate formation at 2000 A/m2 anodic current density under the conditions used in these experiments. The highest anodic current efficiency obtained based on the amount of sulphate formed was 89%. An increase in the anode current density as well as NaOH concentration enhances the cathodic and anodic current efficiencies with respect to the antimony metal deposited and sulphate ions produced, respectively. Despite the high anodic current densities used, the specific energy of this process ranges from 0.6 to 2.3 kWh/kg which is significantly lower than values reported previously due to the prevention of undesirable sulphur species from being formed. The tests revealed that the concentration of thiosulphate formed during the electrolysis decreased with increasing anode current density and NaOH concentration. Addition of polysulphide from 0 to 30 g/L to the electrolyte decreases the current efficiency from 83% to 32% and correspondingly increases the specific energy from 1.7 to 4.8 kWh/kg. Results showed that a build-up of sulphite and sulphate ions in the solution does not have any detrimental effect on the current efficiency of antimony deposition.

Grinding and flotation experiments on a Pb-Zn ore were carried out to evaluate: 1) wear of the grinding media both in the presence and absence of an inhibitor and 2) effect of the inhibitor on the flotation of Pb---Zn minerals. The percentage reduction in the wear of the grinding media was observed to be between 25–36%, depending on the type of the inhibitor and its critical concentration. The inhibitors used in the investigation were sodium sulphite, sodium nitrite, sodium chromate and sodium silicate. The results indicate that a specific corrosion inhibitor, for example sodium sulphite, may give better recoveries and grades in flotation but is not as efficient as sodium chromate in inhibiting the wear of the grinding media. Pulp solutions (after grinding) analysed for metal ion concentrations showed low Fe. Iron released into the solution as a result of corrosion reactions subsequently forms insoluble hydroxy complexes and may coat the mineral surfaces. Such hydrophilic coatings may adversely affect the floatabilities of minerals. The particle size analysis of the ground product has been carried out and the results are discussed.

Redox potential (Eh) control plays a significant role during sulfide mineral flotation by influencing the reactions on the surface of the minerals and accordingly the flotation behaviour. In this study, the metallurgical performance of typical copper sulfide minerals, molybdenite as well as gangue minerals (e.g., pyrite, tennantite, and enargite) under different pH and Eh conditions of the flotation cell were investigated. The copper and molybdenum processing plant at the Sungun complex-Iran were selected as a case study. For this purpose, Eh of flotation cells of phases 1 and 2 of copper and molybdenum processing circuits – Sungun complex – were measured by off-line method. After performing chemical analysis, the mineralogical study of the input load and products of each of the aforementioned flotation circuits in the rougher, cleaner, re-cleaner, and scavenger stages was performed. Based on the results, the potential in cells of phases 1 and 2 of copper concentration plants is in the range of −60 to −100 mV; and for the molybdenum plant, is in the range of −500 to −700 mV. The potentials of more than −100 mV in the phases of copper concentration plants have created suitable conditions for the separation of copper sulfide and molybdenite minerals from gangue minerals, especially pyrite. Adjustment of Eh in the range of −500 to −700 mV in the molybdenum processing plant has also led to the depression of copper minerals and the flotation of molybdenite, resulting in the effective separation of these minerals. However, grade analysis and mineralogical studies indicate the misplaced copper minerals into tailings, the passage of chalcopyrite and pyrite to molybdenum concentrate, the misplaced molybdenite to copper concentrate, and also the presence of minerals containing harmful elements such as arsenic in copper concentrate. Eh fluctuations in phase 1 and 2 of copper plants, the interaction of copper sulfide minerals, especially chalcopyrite with pyrite (and the depression of pyrite in Eh more than −100 mV), are reasons for the misplaced copper minerals into tailings. The interaction of chalcopyrite and pyrite with molybdenite and the high flotation tendency of molybdenite at the potential of +600 mV is the main factor in increasing the Cu and Fe grade in molybdenite concentrate. The interaction of copper minerals with arsenic-bearing minerals and the similar flotation behavior of these minerals in the potential of the rougher cells of the molybdenum processing plant has increased the arsenic grade in the copper concentrate or molybdenum tailings.

Beneficiation of the tailings from Iron Oxide Apatite (IOA) ore has become an important topic in the field of mineral processing as phosphate rock is considered as critical raw material by the European Union. Driven by the strong call for sustainability and green technology, this paper introduces the application of novel and bio-based organosolv lignin particles (OLP) as a reagent for apatite flotation. In the artificial mineral mixture flotation tests, OLP addition or replacement to tall oil fatty acid-based collector (TOFA) was shown to improve flotation kinetics and recovery. In this study, it was demonstrated that one of the widely used commercial TOFA collectors could be replaced with OLP by 70 %. The replacement led to an increase in recovery (+2%) and only a minimal decrease in P grade (−0.3 %) for the rougher-cleaner flotation tests in one of the two feed types tested. The influence of OLP and other reagents on apatite floatability has been investigated through Hallimond tube tests and laboratory scale batch flotation tests as well as zeta potential measurements and spectroscopy tests to further understand the possible mechanism and synergism of reagents in the apatite flotation system.

Trainings play a vital role in the transference of knowledge between skilled and novice operators in the mineral industry. Evaluation is an important part of those trainings, but many trainings rely solely on the trainees’ feedback. This paper presents how technology enhancement can help produce more effective training evaluations to the mineral industry. It describes a case study involving a froth flotation simulator-based training, including details of the simulation, user interface, and the training program. The training was delivered to sixteen mining operators and evaluated by both the traditional method (trainee&apos;s feedback) and with the simulation&apos;s learning evaluation. The feedback evaluation showed a high level of satisfaction with the learning results, while the learning evaluation showed a very different training outcome, putting established evaluation methods such as Kirckpatrick&apos;s “Four levels” into question. Correlations between the learning results and the operators’ personal information such as process work, and academic experience are also presented.

There is a lack of skilled operators for mineral processing plants in the mining sector, which might be related to the challenge of creating trainings that addresses the operator’s daily work problems. In recent years, the use of simulator-based trainings as a tool to build competence has grown in many different fields. With the help of technologies like virtual reality, these tools have been demonstrated to increase awareness and the capability of workers when compared to traditional learning methods. In this paper, a review is presented on the development and application of such technologies in simulation-based training for the training of operators of the minerals industry in the last 20 years. Proposed next steps and new technologies with the potential of improving these applications are also discussed.

The ability to track and trace products in a production process and in the transportation chain from supplier to customers is important for quality control and process improvements. However, good traceability is often difficult achieve for continuous process products as well as for batch produced products where batches intermix. In this paper, guidelines for improving traceability and setting up a traceability system in the iron ore production process are presented based on two case studies. One case is using process data in a simulation approach for a pellets plant and the other is using RFID methodology to trace pellets in the distribution chain. Results show that simulations can aid short-term traceability, whereas long term traceability is possible through marking pellets with RFID transponders, where the applications are suitable.

Electric Pulse Fragmentation (EPF) is an innovative technology that uses High-Voltage Pulsed Power (HVPP) for the selective comminution of a material. This paper aims to compare a beneficiation flowsheet including an EPF treatment in the comminution circuit to a conventional pathway where the EPF step was replaced by a series of jaw crushers. Tests were performed on a skarn ore containing scheelite as the main mineral of interest. This ore is characterized by a fine-grained mineralogy and represents a challenge to conventional comminution processing, requiring fine grinding to liberate the valuable minerals. Fine grinding has high energy requirements and generates large amounts of fines which can result in losses of the target mineral due to their removal before the concentration processes, especially in this case since scheelite is a brittle material.

Comparison of EPF treatment to mechanical crushing with a similar product size P80 (i.e. 80% passing size) showed that the EPF treatment led to a significant increase in WO3 content and distribution in the 0/250 µm size fraction suggesting a pre-concentration aspect to EPF treatment. Moreover, a marked improvement of the grindability of the ore treated at a discharged energy of 9.1 kWh/t was observed with values of 10.6 kWh/t compared to 14.5 kWh/t when conventional treatment was used. Subsequent grinding and concentration steps confirmed the positive impacts of the fragmentation selectivity and pre-weakening effect of the EPF treatment. In particular, a reduction in fines production was observed after ball milling and a better concentrate grade was achieved for a similar recovery rate when an EPF treatment was included in the comminution pathway compared to the conventional one. These results confirm the potential of the EPF treatment for improving the performances of the beneficiation processes of this scheelite-bearing skarn ore.

Early integration of sustainability decisions and mineralogical attributes into the design of minerals processing units offers potential for reducing environmental impacts at mining and processing sites. The objective of this study is to demonstrate how the integration of sustainability indicators and mineralogical attributes could be achieved in developing an integrated modelling framework of a magnetic separator. A magnetic separator unit model based on existing literature was developed to include process stream mineralogical data and to output sustainability indicators. The overall sustainability of processing three ore types (low, medium and high grade iron ore) was evaluated using the developed model. Novel measures for evaluating magnetic separation (Grade Recovery Deviation Index (GRDI)) and energy efficiency (Rotational Energy Transfer Efficiency (RETE)) that incorporate the use of ore characteristics were developed in this study. These measures were used to calculate the separation and energy efficiency sustainability indicator ratings. In total eleven magnetic separator sustainability indicators were identified. Each indicator was assigned a weighting value out of 10 based on its importance. Of the 11 sustainability indicators identified; safety, reliability, Carbon dioxide (CO₂) emissions, water use, noise and job creation ratings did not vary with changing mineralogical attributes of the feed ore. GRDI, RETE, electricity cost, particle emissions and waste generation ratings were observed to be dependent on the ore characteristics and therefore their values varied with different feed ore grades. The Analytic Hierarchy Process (AHP) and Weighted Sum Method (WSM) methods were applied to the sustainability indicator ratings and weightings to evaluate an overall sustainability cardinal score of processing a particular ore feed. Results of this study demonstrate the dependence of overall process sustainability indicators on feed ore mineralogical attributes. The results also provide an indication of the effect of ore variability (typical within a single deposit) on sustainability indicators.

The Thor lake deposit is a world class resource of rare earth (REE) metals and minerals in Canada. Development work to optimize a REE mineral recovery process flow sheet is underway, however, given the ore mineralogy; the developed reagent scheme is relatively complex. As part of a research project, micro-flotation tests were conducted on a feed sample in order to examine factors affecting stream partitioning. SEM–EDX was performed to evaluate variability in grain composition between streams (concentrate and tails) and TOF-SIMS surface analysis was used to determine statistically significant differences in surface species particularly related to potential activation (or depression) of the examined mineral phases. SEM–EDX analysis reveal that the concentrate has a significantly higher proportion of REE bearing grains (carbonates and phosphates) relative to the tail (almost none were identified). Spectral fingerprinting by TOF-SIMS has allowed for the identification of all reagent species investigated. Reagent signal intensity discrimination on test stream mineral surfaces was observed by the TOF-SIMS analysis using reagents at plant concentration levels. TOF-SIMS analysis confirmed that REE bearing grains reporting to the concentrate are doing so in response to collector attachment whereas grains reporting to the tail are doing so in response to a lack of collector and/or in combination with the presence of the depressant. The surface analysis of gangue phases reveal a similar reagent discrimination; the signal intensity of collector species was significantly higher on the concentrate samples relative to the tails while depressant species were significantly enriched on the surface of the gangue phases in the tail samples. A detailed evaluation of the surface species representing the various reagents used in flotation scheme revealed a distinct competitive relationship between two of the reagents. The surface analysis identified that when used in concurrently, there appears to be a negative feedback resulting in a significant reduction in loading for several of the collectors on grains reporting to the concentrate. An evaluation of the effect of reagents on REE mineral in pilot plant is currently under way.

Flotation separation is the most important upgrading critical raw material technique. Measuring interactions within flotation variables and modeling their metallurgical responses (grade and recovery) is quite challenging on the industrial scale. These challenges are because flotation separation includes several sub-micron processes, and their monitoring won&apos;t be possible for the processing plants. Since many flotation plants are still manually operating and maintaining, understanding interactions within operational variables and their effect on the metallurgical responses would be crucial. As a unique approach, this study used the “Conscious Lab” concept for modeling flotation responses of an industrial copper upgrading plant when Potassium Amyl Xanthate substituted the secondary collector (Sodium Ethyl Xanthate) in the process. The main aim is to understand and compare interactions before and after the collector substitution. For the first time, the conscious lab was constructed based on the most advanced explainable artificial intelligence model, Shapley Additive Explanations, and Catboost. Catboost- Shapley Additive Explanations could accurately model flotation responses (less than 2% error between actual and predicted values) and illustrate variations of complex interactions through the substitution. Through a comparative study, Catboost could generate more precise outcomes than other known artificial intelligence models (Random Forest, Support Vector Regression, Extreme Gradient Boosting, and Convolutional Neural Network). In general, substituting Sodium Ethyl Xanthate by Potassium Amyl Xanthate reduced process predictability, although Potassium Amyl Xanthate could slightly increase the copper recovery.

This study investigates the relationship between chemical analyses and magnetic susceptibility of zinnwaldite through magnetic separation of various size fractions. Statistical analyses were used to increase information about magnetic properties of this mineral as a future source of lithium. Statistical modeling indicated that magnetic susceptibility (as a main factor of magnetic separation) accurately can be predicted based on cations content of zinnwaldite. However the size of particles had a significant effect on magnetic susceptibility. The small difference between the estimated and measured values for the non-linear relationship of this prediction (less than 1 (10−8 m3/kg)) shows that these accurate theoretical techniques can be also applied to estimate magnetic properties of zinnwaldite in other resources, and in-situ analysis.

In acidic biological and chemical leaching processes for base metal recovery, iron is dissolved in addition to the desired metal values. Prior to valuable metal extraction iron has to be removed. This is usually achieved through hydroxide precipitation of ferric iron by the addition of lime or limestone to a pH of approximately 3 whereby ferric hydroxide is formed. The aim of this work has been to investigate the possibility to substitute lime or limestone with oxidic industrial by-products for neutralisation and precipitation of iron from leaching solutions. The neutralisation potential for 10 selected oxidic by-products like slags, ashes and dusts were examined and compared with slaked lime.Experiments were performed by decreasing pH to 3 by additions of H2SO4 to slurry of respective by-product at an S/L ratio of 1/10 at 25 °C and continued till no changes in pH were observed during 10 days. Original samples, residues and solutions were analysed by ICP-MS and XRD in order to identify potential harmful elements for the subsequent metal recovery steps.Characterisation of the by-products revealed high concentrations of oxides such as lime, calcite and metal oxides as well as different forms of silicates in the materials which all dissolved at pH 3. The neutralising potential was found to be high for most of the by-products investigated and in the case of Ladle slag it was even higher than for slaked lime. Slags generally had higher neutralisation potential and long-term effects while the ashes had high initial reactivity which is important for continuous neutralisation in stirred tanks with limited retention times. The most reactive materials were Bioash and Mesa lime which both contained considerable amounts of calcite. Replacement of the conventional lime and limestone with oxidic by-products for neutralisation of acidic leaching solutions has the potential to save costs, environmental resources, reduce CO2 emissions and to recycle metal values like zinc contained in the by-products.

The development of molecular tools for the detection and quantification of both species as well as functional traits, aids in a better understanding and control of microbial processes. Presently, these methods can also be used to assess the activity of these organisms or functions, even in complex ecosystems and difficult matrices such as ores and low pH samples. In this paper we present the versatility of one of these tools, Q-PCR, to allow accurate and fast insight in changes in two types of microbial processes representing two ways in which microbes can interact with metals, bioleaching and bioprecipitation. Using the Q-PCR technique it was possible to identify and quantify the thermoacidophilic archaeon Acidianus sp. to be the main microbial strain responsible for biooxidation of arsenite in a low pH reactor. The method was also used to study the dynamics between the iron oxidizing and sulfur oxidizing acidophiles during bioleaching of a zinc concentrate in a batch reactor system and showed that the iron oxidizer Leptospirillum ferriphilum that dominated the starting culture disappeared upon addition of the concentrate. Gradually, bacterial activity was regained starting with growth of sulfur oxidizers and at later stage iron oxidizers started to grow. Molecular analysis can be used to direct research to the relevant organisms involved and concentrate on improving their application (in the arsenite case Acidianus sp.) or in understanding appearances and disappearances of microorganisms (during leaching of zinc concentrate the disappearance of Leptospirillum after high inoculation levels) in order to allow optimization of leaching efficiencies at the lowest (oxygen) costs.

Dry coal beneficiation has been examined by tribo-electrostatic method using Indian thermal coal sample from Ramagundam coal mines. The process of tribo-electric coal/ash cleaning is carried out with a newly built cylindrical fluidised bed tribo-charger with internal baffles, made up of copper metal. The charge transfer in coal maceral and mineral particles after repeated contact with copper plate tribo-charger is measured. Separation of particles in an electrostatic separator according to the polarity of particle charge generated during tribo-electrification is discussed with respect to gas flow rate and residence time in fluidised bed tribo-charger and the applied electric field. The coal and mineral particles charge with positive and negative polarities respectively. The magnitude of particles charge found to be relatively high illustrating greater efficiency of contact electrification in fluidised bed tribo-charger. The separation results with -300 μm size fraction of coal containing 43% ash showed that the ash content can be reduced to 18% and 33% with an yield of about 30% and 67%, respectively. These results are comparable to the maximum separation efficiency curve of washability studies on this coal sample. Since the ash percentage of coal particles collected in the bins close to positive and negative electrodes are about 70% and 20%, a better yield with low ash content can be accomplished on recycling the material.

The separation of rare earth elements (REEs) has been a persistent challenge in the industrial sector. Despite the development of numerous adsorption materials for rare earth element separation, achieving high adsorption capacity and superior separation selectivity from these materials simultaneously has proven difficult. In this study, we synthesized a nanocomposite material called CoFeM@Be_IIM by combining bentonite clay&apos;s good adsorption capacity with cobalt ferrite&apos;s superior magnetic separation performance (CoFe2O4) and ion-imprinted materials’ high target separation selectivity (IIMs). We used surface ion-imprinting technique to create the material. The ion-imprinted material has a maximum adsorption capacity of 87.6 mg/g for Gd(III), with a selectivity of Gd/La ≈ 28.6, Gd/Nd ≈ 22.6, and Gd/Y ≈ 15.2. The Gd(III)-CoFeM@Be_IIM showed good reusability for up to five cycles. Our work presents a new magnetic ion-imprinted nano-adsorbent as a reliable and effective solution for recovering and utilizing REEs from industrial wastewater.

Large amounts of oxidic by-product are annually produced by the steel industry worldwide. By far the largest in volume is slag, generated from different stages of steel production. In order to avoid landfilling, steelmakers usually try to process the slag into useful resources that can be used externally. However, leaching of different metals can sometimes be a problem. Since steel slags are a mixture of numerous types of minerals, the solubility of each mineral will affect the outcome of the leachability. The aim of this study was to investigate how six common slag minerals behave during dissolution. Mayenite (Ca12Al14O33), merwinite (Ca3MgSi2O8), akermanite (Ca2MgSi2O7), gehlenite (Ca2Al2SiO7), γ-dicalcium silicate (γ-Ca2SiO4) and tricalcium aluminate (Ca3Al2O6) were synthesized and their dissolution was evaluated through titration using HNO3 at constant pH. Acidic to alkaline pHs (4, 7 and 10) were selected to investigate the solubility of the minerals under conditions comparable to those prevailing in newly produced slags, and one pH value, representing acid conditions. It can be concluded that all six minerals behave differently when dissolving and that the rate of dissolution is generally slower at higher pH values, which are normal in the case of steelmaking slags. At pH 10, the solubility of merwinite, akermanite and gehlenite is considered low. The dissolution of γ-Ca2SiO4 is not affected in the same way as the other minerals when the pH is changed.

A lead sulphide film precipitated on a zinc sulphide layer of an ATR crystal has been used to study in situ surface reactions of heptyl xanthate adsorption. The lead sulphide film was made by the chemical bath deposition method and was analyzed by X-ray photoelectron spectroscopy. In turn deposited layers make it possible to study the PbS/aqueous solution interface in situ and open up interesting areas for attenuated total reflection spectroscopy. Monitoring the adsorption of heptyl xanthate from a 0.1 mM aqueous solution using the vibration band at 1200 cm-1 has shown the existence of adsorbed molecules on the lead sulphide surface as well as precipitated lead xanthate on the surface at bulk concentrations higher than 1 mM. At lower concentrations, the adsorbed species are dominant as is the precipitate at higher concentrations. The rate of adsorption is in accordance with pseudo first-order kinetics with a rate constant of 0.21 s-1. The Dichroic ratio for heptyl xanthate adsorbed on PbS indicates the hydrocarbon chain of the heptyl xanthate to be preferentially orientated perpendicular to the surface normal of the internal reflection element.

In the present study infrared attenuated total reflection (IR-ATR) was used to monitor the rate of in situ adsorption of heptyl xanthate on a layer of zinc sulphide synthesized on a germanium ATR crystal. The zinc sulphide surface was characterized using X-ray photoelectron spectroscopy (XPS). The absorbance of heptyl xanthate measured increased with increasing bulk concentration of the adsorbate up to an equilibrium plateau value corresponding to a fractional coverage of the surface sites of the substrate. For the adsorption from solutions of concentrations between 10−3 and 10−5 M, the rate of adsorption increased with increasing bulk concentration. At higher concentrations the measured absorbance should be corrected for the absorbance due to the concentration of xanthate in bulk solution. The present work provides a discussion of this correction. Assuming the adsorption stage to be rate-controlling and proportional both to the concentration of the adsorbing species in solution and unreacted surface area, a rate law governing this type of transient adsorption kinetics was derived. By means of absorbance data for the concentrations 0.1 and 0.01 mM, the rate constant of adsorption was calculated. From the initial part of a Langmuir adsorption isotherm, the absorbance at monolayer coverage and the equilibrium constant of adsorption could be estimated.

The cost of lime/limestone for neutralisation is the second largest operating cost in bioleaching. Therefore, these studies have been conducted with the aim to investigate the possibilities for use of by-products such as mesalime and electric arc furnace (EAF) dust for neutralisation during biooxidation of a refractory gold concentrate. Experiments were carried out using a retention time of 57 h in a one-stage reactor and the influence of two industrial by-products on the biooxidation performance was evaluated. The neutralising capacity of EAF dust was lower, while the mesalime was similar to the Ca(OH)2 reference. The arsenopyrite oxidation in experiments ranged from 85% to 90%, whereas the pyrite oxidation was 63-74%. In subsequent cyanidation, final gold recoveries of 90% were achieved in bioresidues from mesalime and Ca(OH)2, while the EAF dust bioresidue had a recovery of 85%. A comparatively high elemental sulphur content in EAF dust probably encapsulates part of the gold, which explains the lower recovery for the EAF dust bioresidue despite a longer residence time. Cyanide consumption was relatively high and ranged from 8.1 to 9.2 kg/ton feed after 24 h of cyanidation. Overall, the by-products tested here have proved to be feasible options as neutralising agents in bioleaching operations.

Tantalum, niobium, and their oxides are important precursor materials, essential for high-temperature alloys and electronic devices. The primary hydrometallurgical extraction technique to extract tantalum and niobium from minerals involves hydrofluoric acid (HF) digestion of the concentrates, followed by solvent extraction as an oxide separation and purification step. Solvent extraction, on the other hand, releases organic solvents which are lost irreversibly via natural evaporation during the process. This research demonstrates a novel chemical process for the extraction and refining of columbite and tantalite concentrates (29% Ta₂O₅ and 16% Nb₂O₅). In this process, the concentrates are reduced using carbon and alkali in the temperature range of 800–950 °C, which helps in reducing and magnetically separating the iron oxides present in the concentrates as metallic iron. The remaining residue is rich in alkali complex (e.g., sodium tantalates and niobates) formed during the roasting process which was reclaimed as a purified mixture of oxides of Nb2O5 and Ta2O5, by using oxalic acid leaching, followed by sodium bisulphate roasting.

The history of the metallurgical industry is rich with data. An enormous amount of data is generated from mining operations and industrial factories, and as deployment of new technologies such as on-line monitoring and in-situ instrumentation proliferate through the 4th industrial revolution, the quantity and quality of data will increase dramatically. The first paper (Part I), describes a range of promising technologies that integrate well with existing mineral processing plants and testing laboratories to demonstrate the enormous potential of a dry laboratory. A dry lab is a type of laboratory that includes applied or computational mathematical analyses for an extensive range of different applications. In both laboratories and mineral processing plants, integration of timely, accurate and reliable data analytics is key to leveraging data to enable data-driven plant design, optimisation and monitoring. However and despite progresses in analytical technology and increasing availability of data and sophisticated data analytics, legacy metallurgical plant and test work data are being underutilised. Understanding the insights contained within legacy metallurgical plant data is critical to the transition into a data- and analytics-driven industry. This paper (Part II) details two case studies that use legacy data to benefit metallurgical processes. One case study focuses on operational data from a gold recovery plant and provide indirect knowledge of the structure and/or composition of the feed sources, and insights to guide the optimisation of the operation. The other case study focuses on laboratory flotation tests, and demonstrates the effectiveness of aggregated data in establishing empirical guidelines that can guide the design and optimisation of new and existing processing operations.

Advancements in modern mineral processing has been driven by technology and fuelled by market economics of supply and demand. Over the last three decades, the demand for various minerals has steadily increased, while the mineral processing industry has seen an unavoidable increase in the treatment of complex ores, continuous decline in plant feed grade and poor plant performance partly due to blending of ores with dissimilar properties. Despite these challenges, production plant data that are routinely generated are usually underutilised. In this contribution and aligned with the direction of the 4th industrial revolution, we highlight the value of legacy metallurgical plant data and the concept of a dry laboratory approach. This study is presented in two parts. In the current paper (Part I), a comprehensive review of the potential for the combination of modern analytical technology with data analytics to generate a new competence for process optimisation are provided. To demonstrate the value of data within the extractive metallurgy discipline, we employ data analytics and simulation to examine gold plant performance and the flotation process in two separate case studies in the second paper (Part II). This was done with the aim of showcasing relevant plant data insights, and extract parameters that should be targeted for plant design and performance optimisation. We identify several promising technologies that integrate well with existing mineral processing plants and testing laboratories to exploit the concept of a dry laboratory, in order to enhance pre-existing mineral processing chains. It also sets the passage in terms of the value of innovative analysis of existing and simulation data as part of the new world of data analytics. Using data- and technology-driven initiatives, we propose the establishment of dry laboratories and data banks to ultimately leverage integrated data, analytics and process simulation for effective plant design and improved performance.

Dry laboratories (dry labs) are laboratories dedicated to using and creating data (they are data-centric). Several aspects of the minerals industry (e.g., exploration, extraction and beneficiation) generate multi-scale and multivariate data that are ultimately used to make decisions. Dry labs and digitalization are closely and intricately linked in the minerals industry. This paper focuses on the instrumentation and infrastructure that are required for accelerating digital transformation initiatives in the minerals sector. Specifically, we are interested in the ability of current and emerging instrumentation, sensors and infrastructure to capture relevant information, generate and transport high-quality data. We provide an essential examination of existing literature and an understanding of the 21st century minerals industry. Critical analysis of the literature and review of the current configuration of the minerals industry revealed similar data management and infrastructure needs for all segments of the minerals industry. There are, however, differences in the tools and equipment used at different stages of the mineral value chain. As demand for data-driven approaches grows, and as data resulting from each segment of the minerals industry continues to increase in abundance, diversity and dimensionality, the tools that manage and utilize such data should evolve in a way that is more transdisciplinary (e.g., data management, artificial intelligence, machine learning and data science). Ideally, data should be managed in a dry lab environment, but minerals industry data is currently and historically disaggregated. Consequently, digitalization in the minerals industry must be coupled with dry laboratories through a systematic transition. Sustained generation of high-quality data is critical to sustain the highly desirable uses of data, such as artificial intelligence-based insight generation.

The Bayer process is a conventional method for refining bauxite in the production of alumina. The Al/Si ratio in bauxite before feeding to the process must be enriched to more than eight by reducing impurities (mainly aluminosilicates). Therefore, diasporic bauxite ores (Al/Si < 6) have to be upgraded by pretreatment methods to meet the required quality for the Bayer process. Flotation separation (direct or reverse) followed by flocculation as an efficient pretreatment method is the main beneficiation technique for upgrading diaspore. Diaspore pretreatment by flotation favors several conditions and possesses certain limitations. This study has systematically explored various effective flotation factors (particle size, surface electrical charge, collectors, depressants, dispersants, flocculation and aggregation) and limitations in the pretreatment of diaspore and has compiled optimum results for its beneficiation. The summary offers various approaches for the selective flotation of diasporic ores via different conditions and suggests perspectives for further investigation.

Prediction of mineral liberation is one of the key steps in establishing a link between ore texture and its processing behavior. With the rapid development of X-ray Microcomputed Tomography (µCT), the extension of liberation modeling into 3D realms becomes possible. Liberation modeling allows for the generation of particle population from 3D texture data in a completely non-destructive manner. This study presents a novel texture-based 3D liberation model that is capable of predicting liberation from 3D drill core image acquired by µCT. The model takes preferential, phase-boundary, and random breakage into account with differing relative contributions to the liberation depending on the ore texture itself. The model was calibrated using experimental liberation data measured in 3D µCT. After calibration, the liberation model was found to be capable of explaining on average of around 84% of the variance in the experimental liberation data. The generated particle population can be used for particle-based process simulation to evaluate the process responses of various ore textures subjected to various modes of breakage.

X-ray microcomputed tomography (µCT) offers a non-destructive three-dimensional analysis of ores but its application in mineralogical analysis and mineral segmentation is relatively limited. In this study, the application of machine learning techniques for segmenting mineral phases in a µCT dataset is presented. Various techniques were implemented, including unsupervised classification as well as grayscale-based and feature-based supervised classification. A feature matching method was used to register the back-scattered electron (BSE) mineral map to its corresponding µCT slice, allowing automatic annotation of minerals in the µCT slice to create training data for the classifiers. Unsupervised classification produced satisfactory results in terms of segmenting between amphibole, plagioclase, and sulfide phases. However, the technique was not able to differentiate between sulfide phases in the case of chalcopyrite and pyrite. Using supervised classification, around 50–60% of the chalcopyrite and 97–99% of pyrite were correctly identified. Feature based classification was found to have a poorer sensitivity to chalcopyrite, but produced a better result in segmenting between the mineral grains, as it operates based on voxel regions instead of individual voxels. The mineralogical results from the 3D µCT data showed considerable difference compared to the BSE mineral map, indicating stereological error exhibited in the latter analysis. The main limitation of this approach lies in the dataset itself, in which there was a significant overlap in grayscale values between chalcopyrite and pyrite, therefore highly limiting the classifier accuracy.

In this work, the purpose was to study the impact of variations in feed ore properties on the performance of a primary autogenous grinding circuit by ore characterisation and simulation. Samples were selected to represent various points in the production system; ore faces with different drillability, grinding circuit feed, mill charges and waste rock. The investigation was carried out at the LKAB Kiruna mine in northern Sweden.The result clearly shows that self-breakage occurs ahead of the mill since the ore hardness, or resistance to breakage, increase with the distance from the mining face. Ore from a location, which by the mine is characterised as “hard to drill”, has the lowest resistance to breakage, and the surrounding rock is clearly harder than the magnetite ore. Validation of a simulation model for the primary autogenous grinding circuit reveals that the differences between simulated and experimental data are small. Therefore, the model is used to simulate the influence of variations in feed ore characteristics on the circuit performance. The simulations show that the net throughput from the circuit at a coarse–hard feed will be ≈10% higher compared to a situation when the feed is fine–soft. Moreover, a fine and soft feed results in a coarser particle size distribution of the mill discharge, compared to a coarse and hard material. However, it is the amount of coarse material in the feed, which is the most influential factor.

At a gold mine in northern Sweden, gold occurring as inclusions in pyrrhotite and arsenopyrite is leached by cyanidation of the ore. The main sulphide minerals in the ore are pyrrhotite and arsenopyrite. Effluents from the cyanidation process are treated with Fe2(SO4)3 to form Fe-precipitates suitable for the co-precipitation of As. The aim of this study was to perform static and kinetic leaching tests on the ore and tailings to define geochemical processes governing As mobility. Sequential leaching tests suggested that the majority of dissolved As deriving from the sulphide fraction in the ore was incorporated in newly formed Fe-precipitates in the tailings. The mobility of As in the tailings was therefore mainly dependent on the stability of these As-bearing Fe-precipitates. Weathering cell tests (WCT) involving 31 weekly cycles of wetting and air exposure were conducted to assess the stability of the As in the tailings under accelerated weathering conditions. The first stage of the WCT was characterized by a pH ≈ 5 and low As leaching, probably driven by the dissolution of amorphous Fe-As species. In the second stage of the WCT, leaching of Fe, S and As increased and the pH decreased to <3.5. An increase of the leachate’s molar Fe/S-ratio suggested that pyrrhotite oxidation was occurring. The falling pH destabilized As-bearing Fe-precipitates, causing further As release. The total As release during the WCT corresponded to only a small proportion of the tailings’ total As content. The accelerated As-leaching observed towards the end of the WCT could thus indicate that its release could increase progressively over time.

The Cemented Paste Backfill (CPB) method allows the mixing of dewatered tailings slurries with cementitious binders to backfill excavated underground workings. After mine closure, CPB workings are permanently flooded by rising groundwater. This flooding is considered beneficial for reducing the risk of acid generation associated with CPB containing sulphide minerals. In general, CPB workings are slowly flooded and the process may lead to regions with a low degree of water saturation to form within the CPB. This in turn, may increase oxygen ingress in the CPB, thereby prolonging oxidation of the minerals. To investigate the environmental impact of this oxidation, tailings containing elevated concentrations of arsenic (As) and pyrrhotite were handled via CPB. In this study, CPB mixtures containing 1–3 wt.% of cementitious binders and tailings was studied. The water saturation level in the CPB-mixtures was lowered as curing time extended. In mimicked flooded conditions, the mobility of As in the CPB mixtures was correlated with As-bearing cementitious phases that are sensitive to a reduction in the pH. In CPB-mixtures with lower proportions of binders, cementitious As-phases dissolved while the water saturation level decreased to form more stable As-phases. Increasing binder fractions, most of the cementitious As-phases persisted in the CPB while water saturation levels were lowered and release of As increased. Regardless of curing conditions, managing these tailings via the CPB method yielded increased mobility of As compared with that in the unmodified tailings; this resulted possibly from the formation of less acid-tolerant As species.

Gold is extracted by cyanide leaching from inclusions in arsenopyrite at a mine in the north of Sweden. The major ore mineral assemblage consists of pyrrhotite and arsenopyrite–loellingite. Arsenopyrite is assumed to be oxidized during cyanidation and the stability of secondary As-phases needs to be assessed. One way of managing such tailings is to convert them into a monolithic mass by using a method called cemented paste backfill (CPB). In CPB, tailings are traditionally mixed with water (typically 25% by weight) and small amounts (3–7%) of binders, and backfilled into excavated underground areas. To investigate the release of arsenic (As) from CPB prepared from As-rich tailings, tailings containing approx. 1000 ppm of As, mainly in the form of As-bearing iron (Fe)-precipitates (FEP), were mixed with small quantities (1–3%) of biofuel fly ash (BFA), ordinary cement, and water to produce monolithic CPB masses. CPB-recipes were designed to meet the strength demand of 200 kPa, stated by the mine operators. Tank leaching tests (TLT) and the weathering cell test (WCT) were used to compare the leaching behavior of As in unmodified tailings and CPB-materials. Results from the leaching tests (TLT and WCT) showed that the inclusion of As-rich tailings into a cementitious matrix increased leaching of As. This behavior could partially be explained by an increase of pH where As sorbed to FEPs becomes unstable. In the CPB mixtures, small (>1%) proportions of the total As in the solid material was released from less acid-tolerant species (i.e. Ca-arsenates and As bonded to cementitious phases). Unmodified tailings generated an acidic environment in flooded conditions at which As-bearing FEPs were stable. Acid was added to the crushed CPB materials during later stages of the WCTs to mimic the effects of weathering. This increased the leaching of Fe and had minor effects on that of As but did not affect S-leaching.

In this study, the flotation behaviour and surface adsorption of smithsonite were investigated using various concentration ratios of potassium amyl xanthate (KAX) and dodecylamine (DDA) in a surfactant mixture. The use of either KAX or DDA during flotation resulted in an increase in smithsonite recovery as the collector concentration increased. Further, the smithsonite recoveries were for the most part less than 40% irrespective of collector concentration However, when a mixture of KAX and DDA was used, smithsonite recovery increased dramatically. The FT-IR spectra show co-adsorption of the amine-xanthate complex using a collector mixture. The presence of KAX in the mixture decreases the electrostatic head-head repulsion between the surface and ammonium ions and increases the lateral tail-tail hydrophobic bonds.

The effects of major components of calcium and sulphate species present in recycled process water on galena flotation has been investigated through Hallimond flotation, zeta-potential, diffuse reflectance FTIR spectroscopy and XPS measurements using pure galena mineral. The significance of process water species in flotation has been understood using deionised water, process water and simulated tap water containing equivalent calcium and sulphate ions concentration as in process water.Hallimond flotation indicated marginally lower recoveries of galena in the presence of calcium and sulphate ions using potassium amyl xanthate as collector. Zeta-potential shows the adsorption of calcium ions whereby the potential are seen to increase while sulphate ions have no significant effect. FTIR and XPS studies revealed surface calcium carbonate and/or calcium sulphate species in process water which affected xanthate adsorption. Presence of surface oxidised species such as sulfoxy, hydroxyl species on galena at pH 10.5 in deionised and process water was also revealed.

Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by pyrite (FeS2), the most abundant metal sulphide on Earth, during grinding was investigated. It was found that pyrite generated H2O2 in pulp liquid during wet grinding and also the solids when placed in water immediately after dry grinding. Type of grinding medium on formation of hydrogen peroxide revealed that the mild steel produced more H2O2 than stainless steel grinding medium, where Fe2+ and/or Fe3+ ions played a key role in producing higher amounts of H2O2. The effect of grinding atmosphere of air and N2 gas showed that nitrogen environment free from oxygen generated more H2O2 than air atmosphere suggesting that the oxygen in hydrogen peroxide is derived from water molecules. In addition, the solids after dry grinding producing more H2O2 than wet grinding indicate the role of pyrite surface or its catalytic activity in producing H2O2 from water. This study highlights the necessity of relooking into the electrochemical and/or galvanic interaction mechanisms between the grinding medium and pyrite in terms of its flotation behaviour.

Laboratory HGMS and WHIMS tests on flotation concentrates proved that grade and recovery in magnetic separation is greatly affected by the particle dispersion of the head feed. In this investigation, the recovery of a spodumene flotation concentrate, floated with a fatty acid collector, was improved by 10% when the pulp pH was reduced from pH 7 to pH 2 in order to improve the particle dispersion. For a phosphine floated Pb product, carrying sphalerite and chalcopyrite, grade and recovery was optimized in a window around pH 5. Recovery was improved by approximately 5%. The carry over capacity from the non-magnetic to the magnetic product for agglomerates containing a small amount of magnetic particles can be estimated using the HGMS capture probability function and the magnetic susceptibility of the material. An estimate of the spodumene / amphibolite system indicates that as little as 3% amphibolite in an agglomerate may be sufficient for the floc to be captured in the matrix. The corresponding number for the galena / sphalerite system is about 20%.

Modelling of wet grinding in tumbling mills is an interesting challenge. A key factor is that the pulp fluid and its simultaneous interactions with both the charge and the mill structure have to be handled in a computationally efficient way. In this work, the pulp fluid is modelled with a Lagrange based method based on the particle finite element method (PFEM) that gives the opportunity to model free surface flow. This method gives robustness and stability to the fluid model and is efficient as it gives possibility to use larger time steps. The PFEM solver can be coupled to other solvers as in this case both the finite element method (FEM) solver for the mill structure and the DEM solver for the ball charge. The combined PFEM-DEM-FEM model presented here can predict charge motion and responses from the mill structure, as well as the pulp liquid flow and pressure. All cases presented here are numerically modelled and validated against experimentally measured driving torque signatures from an instrumented small-scale batch ball mill equipped with a torque meter and charge movements captured from high-speed video. Numerical results are in good agreement with experimental torque measurements and the PFEM solver also improves on efficiency and robustness for solving charge movements in wet tumbling mill systems.

The smoothed particle hydrodynamic (SPH) method is used to model a ball charge and its interaction with the mill structure, while the flexible rubber lifter and the lining are modelled with the finite element method (FEM). The adaptive nature of the SPH-method together with the non-connectivity between the particles results in a method that is able to handle very large deformations. This computational model makes it possible to predict the deflection and stresses of the lining in a pilot ball mill and the mechanical waves travelling in the mill system. It also makes it possible to predict e.g. charge pressure and von Mises’ stress within the charge and the contact forces between the charge and lining. The deflection profile of the lifters obtained from SPH–FEM simulation shows a reasonably good correspondence to pilot mill measurements as measured by an embedded strain gauge sensor.

Computational demands and the lack of detailed experimental verification have limited the value of distinct element method (DEM) modelling approaches in mill simulation studies. This paper presents the results of a study in which the deflection of a lifter bar in a pilot ball mill is measured by an embedded strain gauge sensor and compared to deflections predicted from finite element (FE) simulations. The flexible rubber lifter and the lining in a tumbling mill are modelled with the finite element method (FEM) and the grinding medium is modelled with DEM. The deflection profile obtained from DEM-FE simulation shows a reasonably good correspondence to pilot mill measurements. To study the charge impact on the mill structure two different charges are used in the simulations. The approach is a contribution to the validation of DEM-FE simulations and an introduction to the description of a bendable rubber lifter implemented in a DEM-FEM mill model. It opens up the possibility to predict contact forces for varying mill dimensions and liner combinations. FEM is especially valuable in this case, since there are readily available libraries with material models.