In previous work, we have shown how an ultrasound pulse-echo setup can be used to simultaneously measure particle velocity profiles and local solids concentration variations in solid/liquid particle suspensions. In this paper, we demonstrate a real-world case where the system is installed in a wet low-intensity magnetic separator, a process in which magnetic material is separated from gangue. The method was evaluated at LKAB's R&D facilities in Malmberget, Sweden, on one of their pilot scale separators. The results show that it is possible to detect changes in the flow velocity patterns and the local solids concentration, as the operational conditions of the separator are varied.

This paper presents an ultrasonic pulse-echo technique for on-line monitoring of variations in solids concentrations in particlesuspensions. The method is based on time-frequency analysis of the backscatter signals, exploring variations in spectral content ofthe backscatter as function of depth in the suspension. Experiments on a settling of magnetite particles in water, at varying solidsconcentrations, show that the settling process can be followed by studying the energy of backscattered ultrasound.

The particle surface properties are essential for understanding froth flotation, particularly for the evaluation of various chemical or reagent effects.

Dynamic Vapor Sorption (DVS) is used in the pharmaceutical industry for the evaluation of surface properties and has to the knowledge of the authors not been used for applications in mineral processing. This paper describes an evaluation of industrial ore samples using DVS.

Four samples (feed, CuPb concentrate, Cu concentrate and Pb concentrate) from each of the Cu – Pb flotation processes in the Boliden and Garpenberg concentrators, Sweden, were analyzed by DVS in order to investigate if this technique could be used to estimate differences in their hydrophilicity. The DVS measures the water uptake as a function of the relative humidity (%RH) at constant temperature.

For both series of four samples, it was found that the DVS-data are in precise agreement with the flotation theory on hydrophobicity (indicated by differences in water uptake). The feed material, without any collectors, adsorbed more water compared to the CuPb bulk concentrate, which in turn adsorbed more water than the Cu concentrate. The lead concentrate on the other hand, which had been depressed by dichromate and should be more hydrophilic, showed a higher adsorbance of water than that of the CuPb concentrate.

The repeated measurements of three sub samples from one of the ore samples gave a mean value and an estimated standard deviation of 0.13 ± 0.01%. This shows that the method gives highly reproducible results and that the differences between the samples had high significance. This also shows that the DVS method can serve as a useful complement to traditionally used contact angle or capillary absorption-based measurement methods, especially when screening for new flotation reagents on industrial ore samples.

The understanding of particle surface properties is essential for the study and evaluation of froth flotation phenomena, particularly in the investigation of various chemical or reagent effects. Dynamic Vapor Sorption (DVS) is a method used for the analysis of surface properties of powders for instance in the pharmaceutical industry. To the knowledge of the authors, it has however not been used before in applications related to mineral processing. The DVS technique involves measurement of the water uptake of a relatively small amount of sample as a function of the relative humidity (% RH) in a temperature-controlled environment. The purpose of this work was to evaluate the method and investigate how it can complement existing techniques for surface characterization in mineral processing. Four samples (feed, CuPb concentrate, Cu concentrate and Pb concentrate) from the Cu – Pb flotation process in the Garpenberg concentrator, Sweden, were analyzed by DVS and the traditional capillary absorption technique (Washburn capillary rise). This enabled comparison between the two methods and evaluation of their respective advantages and disadvantages. Both methods give the expected ranking of the hydrophobicity for CuPb concentrate, Cu concentrate and Pb concentrate, but a discrepancy was observed for the feed. Washburn gave a value for the contact angle which was in the same range as for the CuPb concentrate, whereas DVS gave a value for the moisture uptake which was much higher than for the CuPb concentrate. Thus, DVS ranks all samples correctly, but with an unexpectedly high value for the feed whereas Washburn gives good ranking for three samples out of four. Potential reasons for the discrepancies are discussed.

Der Trend in der Entwicklung der Flotationstechnologie geht weiterhin in Richtung sehr großer Zellen. Ein Scale-up von Flotationszellen wird zumeist unter Beibehaltung ähnlicher geometrischer Proportionen vorgenommen, d. h. das Verhältnis von Durchmesser zu Höhe wird bei Vergrößerung des Volumens häufig konstant gehalten. Zudem werden bei dem Entwurf von Flotationsanlagen zumeist mehrere Zellen mit identischer Geometrie innerhalb einer Flotationsbank verwendet. Die Verwendung weniger Standardgrößen in einer Flotationsanlage vereinfacht einerseits Entwurf, Herstellung und Wartung der Flotationsapparate. Andererseits werden hierdurch Leistungsfähigkeit und Selektivität des Flotationsprozesses nicht notwendigerweise sichergestellt. Der Geometrieparameter, der bei gegebenem Zellenvolumen die Leistungsfähigkeit bestimmt, ist die Zellenhöhe. Sie hat Einfluss auf den hydrostatischen Druck und die Hydrodynamik der Trübe, die Wegstrecke, die Partikel-Blase-Agglomerate zurücklegen müssen, sowie die Homogenität der Durchmischung. Auch die Dicke der Schaumschicht hängt vom Durchmesser-Höhe-Verhältnis ab. Ziel der Forschungsarbeiten ist es, ein besseres Verständnis der Materialverteilung und der Suspensionseigenschaften innerhalb einer Flotationszelle zu erlangen und anhand dieser Informationen aufzuklären, wie Veränderungen der Zellengeometrie die Trennleistung beeinflussen können. Zu diesem Zweck wurden erste systematische Messungen und Analysen der räumlichen Verteilung der verschiedenen Phasen innerhalb einer 160 m³ Flotationszelle im Rahmen der industriellen Anreicherung eines armen Kupfererzes durchgeführt. Die Konzepte für die Probenahme an verschiedenen vertikalen und seitlichen Positionen der Flotationszelle werden vorgestellt. Die Ergebnisse der experimentellen Arbeiten geben einen Einblick in die räumliche Verteilung der Trübe innerhalb der Flotationszelle. Auf der Grundlage der gemessenen Phasenverteilung und Konzentrationen sowie der Partikeleigenschaften an verschiedenen Positionen innerhalb der Zelle werden Implikationen für einen optimierten Entwurf von Flotationszelle und -anlage diskutiert.

Social acceptance has emerged as a topic of outmost importance for the mining and metals industry. Recently, Luleå University of Technology has been involved in a number of EU-projects aimed at addressing issues related to social acceptance, wider society awareness building and education, as well as exploring the relation between policymaking and mining industry innovations towards more sustainable production. In this respect, the FAME project (funded by the EU through Horizon 2020) has a strong focus on developing processes and technologies towards minimal impact on environment, while at the same time considering health and safety aspects and being socio-politically acceptable.   

This presentation reflects on social acceptance issues, with particular focus on the Nordic and European context. The relevance of good working conditions, community involvement and trust-building as well as consideration for the environment are mentioned as key factors for a successful mining project. The mining industry is constantly working on process and raw material efficiency, water and energy savings, safer and better residue handling as well as remediation and protective actions at end of life. This work needs, however, to be complemented with public information and knowledge sharing both on local and on wider society level.

It is concluded that continuous efforts are needed for promoting social acceptance of the mining industry. On the local level, it is the responsibility of industry to build trust with the surrounding community. On wider society level a combination of stakeholder dialogue meetings and education initiatives are needed in order to generate understanding of the role of the mining and metals industry in society, possibilities and constraints of the circular economy, and other issues related to raw materials. In this respect, multiplier organisations such as NGOs, industry branch organisations and academia play a key role for successful outreach.

A 2-dimensional computational model based on the discrete element method (DEM) is utilized for modeling of stamp-charged coke making. In this process, a large volume of coal is compacted to one single coal cake before entering the coke oven. Cake densification and mechanical strength development are key factors for the subsequent production of a high-quality coke. An approach is introduced for model calibration utilizing multiple control parameters obtained from a laboratory-scale stamping device. Experimental data on stamper rebound amplitude, attenuation and peak force are compared with simulation output in a pairwise manner by constructing a criteria space, which allows identification of model settings best satisfying the control parameters. The calibration procedure carried out by multiple criteria comparison aided model parameter selection for reproducing stamper behavior in response to the properties of the cake subjected to compaction. This modeling and calibration procedure offers possibilities for numerically studying the densification and mechanical strength development of coal cakes. However, the approach is also more widely applicable to other compaction processes.

Particle dynamics simulation has been established as an accepted and integral part of research and development in various fields of engineering. Simulation offers benefits in predicting particle system behaviour, geometry optimisation in equipment design and in deepening the understanding of particle-level phenomena. In this paper, methods for studying particle-based problems are reviewed and linked to applications relevant to the minerals industry. The current state of models is discussed and guidelines are given regarding current problems and future potential of particle simulation in mineral processing.

Within stamp-charged coke making a large volume of coal is compacted to one single coal cake before entering the coke oven chamber. This is done by means of several falling stampers in a stamping machine having a mould nearly of the oven’s dimensions. Producing a high quality coke also from inferior coals requires a cake density of approximately 80% of the coal density. Besides that the industrial stamp-charging process demands a minimum mechanical strength of the coal cake to move it from the stamping mould into the oven chamber without failure. Densification and the build up of cake strength were investigated earlier in stamping tests using a micro-stamping device [1-2]. The quantities derived from these tests (as e.g. cake density or porosity) represent average values for the entire cake. Statements describing the local compaction state at different heights are difficult to achieve without destructing the cake.In order to gain better insight into the densification process and the inner structure of the coal cake a computational model based on the discrete element method, DEM, has been set up using 2 and 3-dimensional simulation software. The stamper’s position and velocity as well as the force acting on the stamper were monitored and the model’s response was compared against measurement data from laboratory stamping tests.It was possible to reproduce the force and displacement pattern of the stamper in response to the visco-elastic properties of the cake using standard DEM bonding and contact models. Furthermore, the rearrangement of particles in response to the compaction by the stamper was tracked by calculating their displacement at the point the stamper hit the coal surface. The latter can also be used as indicators of particle deformation or breakage. By defining control points at different heights the particle displacement, stress and strain rates, porosity could be studied at different heights.

Within stamp-charged coke making, a large volume of coal is compacted to one single coal cake before entering the coke oven chamber. This is done by means of several falling stampers in a stamping machine having a mold nearly of the oven’s dimensions. Producing a high quality coke from inferior coals requires a cake density of approximately 80% of the coal density. Besides this, the industrial stamp-charging process demands a minimum mechanical strength of the coal cake to move it from the stamping mold into the oven chamber without failure. Densification and the build up of cake strength were investigated earlier in stamping tests using a micro-stamping device. The quantities derived from these tests (as e.g. cake density or porosity) represent average values for the entire cake. Statements describing the local compaction state at different heights are difficult to achieve without destructing the cake. In order to gain better insight into the densification process and the inner structure of the coal cake, a computational model based on the Discrete Element Method (DEM) was set up using 2 and also 3-dimensional simulation software. The stamper’s position and velocity as well as the force acting on the stamper were monitored and the model’s response was compared against measurement data from laboratory stamping tests. It was possible to reproduce the force and displacement pattern of the stamper in response to the viscoelastic properties of the cake using standard DEM bonding and contact models. Furthermore, the rearrangement of particles in response to the compaction by the stamper was tracked by calculating their displacement at the point the stamper hit the coal surface. The latter can also be used as an indicator of particle deformation or breakage. By defining control points at different heights the particle displacement, stress and strain rates, porosity could be studied at different heights.

Coking of coal blends using high-volatile coals with poor caking properties can be achieved by densifying the coal prior to carbonisation. In stamp-charged coke making, the coal charge is compacted to one large cake before entering the coke oven. A coal cake density of approximately 80% of the coal solid density is needed to produce a high-quality coke. Also, sufficient mechanical strength is required when transferring the cake from the stamping machine to the oven. To gain insight into the densification process and cake structure a 2-dimensional computational model based on the discrete element method (DEM) was set up.The model was validated against force and displacement patterns from laboratory stamping tests. Stamper movement in response to cake properties could be reproduced. The approach also enables tracking of cake porosity, particle rearrangement, stress and strain rates, etc. This offers additional possibilities for studying the densification process and understanding mechanical strength development.

A 3-dimensional modified Stokesian dynamics-based technique for simulating mineral particle suspensions is presented. Stokesian dynamics is a mesh free particle approach, which resembles the discrete element method. It includes hydrodynamic interactions and other interparticle forces. Expressions for the hydrodynamic interactions were modified based on results from finite element (FE) calculation. The modifications allow for broader particle size distributions than captured by traditional analytical expressions describing hydrodynamic interactions. In addition, models are presented for colloidal interactions, steric repulsion caused by polymer adsorbed onto mineral particles and the Brownian motion. These models expand the applicability down to μm and nm size particles. Comparison between governing forces can be made by generation of dimensionless expressions such as the particle Reynolds and Peclét numbers. Numerical simulations performed using this technique enable the study of microscopic scale mechanisms and the characterisation of particle systems. This allows for appreciation of microstructure development in time and the prediction of macroscopic level properties of particle suspensions and consolidating systems. This paper reports on both model development and results utilising the above-described approach. In conclusion, the method is put into context by discussion of the applicability of the method in various wet-state mineral processing applications.

The dynamic behaviour of μm-scale ferromagnetic particles in suspension is of interest for various mineral beneficiation processes. It is, however, difficult to experimentally study such processes at the particle-level. In these instances it can be advantageous to resort to suitable particle simulation methods.Stokesian dynamics is a mesh-free numerical technique developed for suspensions of nm to mm size particles. The method inherently considers hydrodynamic interactions, but additional interaction models can be included depending on the system under investigation. We here present a Stokesian dynamics (SD) implementation, which allows for simulation of the motion of suspended magnetic particles in presence of an external magnetic field. The magnetic interaction model includes particle-field interactions as well as pairwise interactions between magnetised particles.Simulations are compared with experiments using a laboratory-scale flow cell. The method is shown to be realistic for studying ferromagnetic suspensions in mineral processing applications, and can be useful in understanding and predicting the efficiency of mineral separation processes.

In this work an ultrasound-based measurement method is used formonitoring suspension velocity and build-up of magnetic material inside awet Low-Intensity Magnetic Separator, a process used e.g. inbeneficiation of magnetite ores. Today the only available option is tomonitor material transport between unit operations; i.e. flow rate,solids concentration, and particle size distribution of suspension flowin pipes are measured online using standard equipment.An Acoustic Backscatter System is fitted to the tank of a separator, andused to monitor the internal flow. A method called Ultrasonic VelocityProfiling is used to capture internal velocity profiles. Simultaneously,the backscatter signal intensity is used to get indications about localsolids concentration of the flow, and build-up of magnetic material. Themethods are evaluated in realistic conditions, where the effect ofvarying factors relevant to machine performance is investigated. Theincluded factors are; the slurry feed rate, the slurry solidsconcentration, the magnet assembly angle, and the drum rotational speed.The presented method gives useful information about the internal materialflow inside the separator. The velocity measurements capture the,sometimes complex, internal flow patterns, for example the presence andvelocity of a recirculating flow in the dewatering zone. Additionally,keeping a balanced material loading in the concentrate dewatering zone isimportant to separator performance. Using the signal backscatterintensity it is possible to qualitatively monitor this material loading.Generally these direct measurements can aid in improvements to machinedesign, process optimization, and process control.

The internal material transport and selection processes of the wet low-intensity magnetic separators (LIMS) are poorly understood; this calls for improved measurement techniques. In this work an ultrasonic velocity profiling (UVP) technique for measuring how material flow velocity varies with penetration depth is presented. A measurement depth of just a couple of centimetres would greatly improve the understanding of the separation process in a LIMS.When applied to flows of mineral suspensions with high volumetric solids concentration, similar to those in the separators, UVP is unique in combining:•Non-intrusive measurements.•Operates using just one sensor element (transducer).•Relatively good spatial resolution.•Penetrates opaque suspensions.•Fast sampling rate.Here, flows are studied in a rectangular duct (50 × 75 mm). Using magnetite suspensions, measurement through the whole depth of 50 mm is made with good accuracy. Velocity profiles are presented for solids concentrations of 5% and 9% solids by volume (20% and 36% by weight). Even at 9 vol% solids it is possible to reach a penetration depth of more than 25 mm.

In the mining industry magnetite particles are transported in aqueous suspension through different stages of the process. In some stages it is of interest to monitor both the concentration and particle velocity profiles over a cross-section of the flow. In this paper an ultrasonic flow meter method based on cross-correlation of backscattered sound is presented. High solid particle content (e.g. 20-40 wt%) makes this challenging and therefore the emphasis lies on developing robust signal processing techniques for particle velocity estimation. The developed method is evaluated in laboratory experiments on flows in a rectangular duct. Transducers with centre frequency 1, 2, 4 and 5 MHz are evaluated in flows with a solid content of 20% by weight (4.7 vol% solids). Using the 2 MHz transducer a penetration depth of 50 mm is reached.

The internal workings of wet Low Intensity Magnetic Separators (LIMS) are poorly understood. In this work an Ultrasonic Velocity Profiling (UVP) technique for measuring material flow speed at varying depth. A measurement depth of just a couple of centimetres will greatly improve our understanding of the separation process.When applied to flows of high density mineral suspensions, similar to those in wet LIMS, UVP is unique in combining:• Non-intrusive measurements.• A single transceiver element is sufficient.• Relatively good spatial resolution.• Penetrates opaque suspensions.• Fast sampling rate.Here, flows are studied in a simple rectangular geometry (50x75 mm), using dilute magnetite suspensions; measurement through the whole depth of 50 mm is made with good accuracy. Velocity profiles are presented for different sensors at solids concentrations of 5 vol% solids.

In the mining industry, magnetite particles are transported in suspensions with water through different stages of the process. In some of these stages, it is of interest to monitor both the concentration and particle velocity over a cross-section of the flow. High particle concentration makes development of flow measurement techniques challenging. An additional challenge is that the flow is often accessible from one side only, which further limits the selection of applicable techniques. Previous work by the authors focused on using pulse-echo ultrasound for flow velocity profile estimation. In this paper the same setup is used to simultaneously study local variations in solids concentration. Ultrasound pulses are transmitted into the suspension, and the resulting backscatter is recorded. The statistics of the backscatter depend on solids concentration, particle size distribution, particle density, etc. We demonstrate how a short-time (windowed) Power Spectral Density (PSD) estimate can be used to obtain qualitative information about local solids concentration variations. For demonstration, a magnetite suspension carrying up to 7.5 vol% particles (29 wt%, mean particle size 34 μm) is pumped through a closed rectangular channel. When the pump is stopped, pulse-echo ultrasound (with a center frequency of 2.25 or 3.5 MHz) is used to monitor the sedimentation process. Nine snapshots of the process are included. These show a time lapse of the sedimentation, with 5 s between each image. It is clear that the short-time PSD is a good indicator of local mass fraction variations.

In the mining industry, ferromagnetic particles (e.g. magnetite) are concentrated using wet low-intensity magnetic separation (LIMS). The performance is to a large extent controlled by the internal flow conditions in the separator. In previous work, it was shown how an ultrasound pulse-echo setup can be used to simultaneously measure particle velocity profiles and local solids concentration variations in laboratory conditions. In this paper, a real-world case is demonstrated where the system is installed on one of the wet LIMS at the LKAB R&D facilities in Malmberget, Sweden. For the pilot scale experiments a setup with two ultrasound transducers, mounted at the bottom of the separator tank, is used. The design of experiments method is used to study the effects of the feed solids concentration, drum rotational speed, position of the concentrate weir, and the magnet assembly angle on the measured flow patterns. The results show that it is possible to detect changes in the flow velocity patterns and the local solids concentration, as the operational conditions of the separator are varied. Of the factors studied, the drum rotational speed has the strongest influence on the overall flow velocity in the dewatering zone. Also, the presence of a recirculating flow transporting gangue particles away from the concentrate is confirmed. The factor with the strongest influence on this recirculating flow is also the drum rotational speed, together with the magnet assembly angle. Using this method it is possible to make high quality measurements of internal flow velocity profiles. It is also possible to monitor material build-up on the separator drum, and e.g. detect overload of magnetic material. The insights gained, and the methods developed, have generated new possibilities to control, optimise, and develop the wet LIMS process.

Ultrasound based flow measurement methods have a large potential for the mining industry and its processing plants. Ultrasound travel through dense suspensions and is not affected by the magnetic fields sometimes present in this type of equipment.A cross-correlation based method is used for localized particle velocity measurements in one and two dimensions. Simultaneously, using the same data, information about local particle concentration is extracted from the power spectral density of the backscattered signal. Experiments are carried out both in simplified geometry and in full scale equipment in an iron ore pilot benefication plant.In the simple geometry it is possible to assess the precision of the methods by comparing the measurements to theory and numerical simulations. The results from the pilot plant experiments show that these methods can be applied to real world processes

ObjectivesThe aim of WP4 “Innovative Processing” is to elaborate how innovations in mineral and metallurgical processing are generated or taken up in different EU Member States and on EU‐level and how this is either facilitated or inhibited by policies and legislation on national or European level. The purpose oft he deliverable 4.3 is to complement the findings of D4.1 and D4.2 by carrying out additional interviews with representatives from different stakeholder groups (academia, industry, NGO’s and policymakers). The topics and questions of the questionnaire addressed the respondents’ perception of national and EU‐ and EU MS level mineral policies, gaps and needs with respect to innovation in mineral‐ and metallurgical processing. Questions for the questionnaire focus on previously identified innovations in mineral processing, metallurgical processing and metal recycling. Based on the input both from previous deliverables and from findings through the additional interviews and innovation cases, an analysis of needs and gaps as well as a SWOT analysis has been conducted. Recommendations for future development of mineral and metallurgical processing sector were evaluated.

Main FindingsConclusions and recommendations for future policy development for innovation in mineral and metallurgical processing were developed based on a survey and a SWOT analysis.

• Most of the mineral policies are addressing the entire mineral value chain. Several statutory provisions are related to mineral and metallurgical processing. National mineral policies are not very much addressing the mineral and metallurgical processing, while recycling is dislocated from mining/mineral legislation.
• The sentiment amongst policy makers towards the raw materials industry has improved on EU level through a number of strategic policy initiatives (e.g. the Strategic Implementation Plan for Raw materials, the revised EU Industrial Policy Strategy, the Raw Materials Initiative).
• The use of raw materials from secondary sources has been identified as being an integral part of the life cycle of materials.
• Innovations in mineral and metallurgical processing are not supported at strategic and economic/investment level. The policy is neutral or inhibiting through long and uncertain permitting procedure, or is indifferent to innovation as to mineral and metallurgical processing.
• The European knowledge and skills base in mineral and metallurgical processing has diminished during the past 20 years.