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  • 1.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    In-Situ Monitoring of Particle Velocities and Solids Concentration Variations in wet Low-Intensity Magnetic Separators2015Ingår i: 2015 IEEE International Ultrasonics Symposium, IUS 2015: Taipei, 21-24 Oct. 2015, Piscataway, NJ: IEEE Communications Society, 2015, artikel-id 7329339Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 2.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Monitoring local solids fraction variations in multiphase flow using pulse-echo ultrasound2015Ingår i: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 70, s. 376-379Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 3.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A novel method for modelling of interactions between pulp, charge and mill structure in tumbling mills2014Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 63, s. 65-72Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Modelling the pulp fluid and its interaction with both the charge and the mill structure is an interesting challenge. The interaction is normally modelled with a combination of CFD and DEM, where the DEM particles (grinding balls) create the structure through which the fluid penetrates, and in its turn creates forces on the grinding balls. However, in a tumbling mill, many free surfaces are found and that limits the use of CFD. An alternative computational approach is here necessary.The smoothed particle hydrodynamic (SPH) method has earlier been used to model a ball charge and its interaction with the mill structure. In the present contribution, a SPH description of the pulp fluid is introduced. The lifters and the lining are still modelled with the finite element method (FEM), and the grinding balls with DEM. This combined computational model makes it possible to predict pressure within the pulp fluid. It is also possible to predict how the dampening effect of the pulp liquid is affected by its viscosity and density. The charge induced torque in a laboratory-scale ball mill is used for validation, and the mechanical shock waves travelling in the mill system are described

  • 4.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling and validation of interactions between pulp, charge and mill structure in tumbling mills2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Modelling the pulp fluid and its interaction with both the charge and the mill structure is an interesting challenge. To close the gap between reality and numerical result in modelling of tumbling mills, physically realistic methods are a necessity. A problem is that tumbling mills often operate in a metastable state because of the difficulty to balance the rate of replenishment of large ore particles from the feed with the consumption in the charge. Understanding of the charge motion within the mill is of significance in mill optimisation. The comminution process is complex and to include all phenomena that occur in a single numerical model is today not possible. Therefore, limiting the modelling to the physical interaction between charge, mill structure and pulp liquid without simulating the actual crushing is the major goal in this work. The smoothed particle hydrodynamic (SPH) method has earlier been used to model a ball charge and its interaction with the mill structure. The mesh free formulation and the adaptive nature of the SPH method result in a method that handles extremely large deformations and thereby suits modelling of grinding charges and pulp liquids. In the present contribution, a SPH description of the pulp fluid is introduced. The lifters and the lining are still modelled with the finite element method (FEM), and the grinding balls with the discreet element method (DEM). This combined computational model makes it possible to predict pressure and shear stresses within the pulp fluid. It is also possible to predict how the dampening effect of the pulp liquid is affected by its viscosity and density. The charge induced torque in a laboratory-scale ball mill is used for validation, and the mechanical shock waves travelling in the mill system are described. The results from the coupled 3D SPH-DEM-FEM model show a fair estimation of the induced torque due to the charge motion in a tumbling mill. This is a good indication that the model is physically correct.

  • 5.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Berggren, Andreas
    Boliden Mineral AB, New Boliden AB.
    Development of physically based tumbling mill models2014Ingår i: Proceedings of XXIII International Mineral Processing Congress: XXVII, Santiago, Chile 20-24 October 2014, Santiago: IMPC , 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Numerical modelling of grinding in tumbling mills is traditionally done with the discrete element method (DEM). The grinding balls are then represented by DEM particles and the mill structure is considered rigid. To include more physical phenomena several numerical methods can be combined. One important improvement is to include the mill structure response, using the finite element method (FEM). The interaction between charge and lining can then be studied in detail. The pulp can also be included using a particle-based continuum method e.g. smoothed particle method (SPH). The strength of SPH lies in modelling of free surface flows and very large deformations and it is suited to model simultaneous fluid and granular flow. Still, the coarse particles (grinding balls) in the charge are suitable to be model using DEM. Each of these methods has their strength and weaknesses, but combined they can successfully mimic the main features of the charge movement. With these numerical tools the complex interaction between the different components of the grinding process; pulp, charge, lining and the mechanical behaviour of the mill, can be studied together. This work will present novel numerical approaches to model, simulate and validate charge behaviour in tumbling mills. These numerical models give possibilities to better understand the physical and mechanical behaviour of particulate material systems during grinding in a tumbling mill. This is important in order to develop and optimise future high-capacity grinding circuits and save energy.

  • 6.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Validation of a model for physical interactions between pulp, charge and mill structure in tumbling mills2015Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 73, s. 77-84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Modelling the pulp fluid and its simultaneous interactions with both the charge and the mill structure is an interesting challenge. The interactions have previously been modelled for dry grinding with a combination of discrete element method (DEM), smoothed particle hydrodynamics (SPH) and the finite element method (FEM), where the DEM particles or SPH particles represent the grinding balls and FEM is used to model the mill structure. In this work, the previous model is extended to include fluids with SPH. Wet milling with water and a magnetite pulp, for graded and mono-size charges are numerically modelled and validated. The internal working of the charge and the physical interaction between the charge and the mill structure is studied. The combined SPH–DEM–FEM model presented here can predict the classical DEM results, but can also predict responses from the mill structure, as well as the pulp liquid flow and pressure. Validation is conducted by comparing numerical results with experimental measurements from grinding in an instrumented small-scale batch ball mill equipped with an accurate torque metre. The simulated charge movement is also compared with high speed video of the charge movement for a number of cases. Numerical results are in good agreement with experimental measurements

  • 7.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Validation of tumbling mill charge induced torque as predicted by simulations2013Ingår i: SME Annual Meeting 2013, Denver, CO, USA: Society for Mining, Metalurgy and Exploration, 2013, artikel-id Pre-print 13-145Konferensbidrag (Refereegranskat)
    Abstract [en]

    Understanding mill charge motion is important. In the charge, the centre of gravity is shifted from the rotational centre of the mill system, and its motion is induced by rotation of the mill, while at the same time the charge creates a torque into the mill system. Breakage of ore particles and wear of liners/ball media are closely linked to the motion. To study these phenomena in a physically correct manner, numerical models for different parts of the mill system are needed. Validations of such models are scarce, because of the difficulty to measure in a tumbling mill. Experimental measurements in a lab mill were done for diverse load cases: varying feed materials, mill fillings, mill speeds and pulp liquids. The mill is set up to directly measure the charge-induced torque. The accuracy is good with relative uncertainty smaller than ±2% for relevant load cases. A full three dimensional numerical model of the whole mill is used to predict induced torque. Agreement between predicted and measured torque at steady-state is good. In addition, the model can accurately predict the mill start-up behaviour for torque and mill power. This proves that the model is physically correct, and can be used for full-scale mills.

  • 8.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Validation of tumbling mill charge induced torque as predicted by simulations2013Ingår i: Minerals & metallurgical processing, ISSN 0747-9182, Vol. 30, nr 4, s. 220-225Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Understanding mill charge motion is important. In the charge, the center of gravity is shifted from the rotational center of the mill system, and its motion is induced by rotation of the mill, while at the same time the charge creates a torque into the mill system. Breakage of ore particles and wear of liners/ball media are closely linked to this motion. To study these phenomena in a physically correct manner, numerical models for different parts of the mill system are needed. Validations of such models are scarce, because of the difficulty to measure inside a tumbling mill.Experimental measurements in a lab mill were done for a number of load cases: varying feed material, mill filling, mill speed and pulp liquid. The mill is set up to measure the charge-induced torque. The accuracy is good with relative uncertainty smaller than ±2% for relevant load cases.A full three dimensional numerical model of the whole mill is used to predict induced torque. Agreement between predicted and measured torque at steady-state is good. In addition, the model can accurately predict the mill start-up behavior for torque and mill power. This proves that the model is physically correct, and can be used for modeling large-scale mills.

  • 9.
    Sand, Anders
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Toivakka, Martti
    Åbo Akademi University.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    A Stokesian Dynamics Approach for Simulation of Magnetic Particle Suspensions2015Ingår i: Proceedings of Computational Modelling 2015: Minerals Engineering International, 2015Konferensbidrag (Refereegranskat)
  • 10.
    Sand, Anders
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Toivakka, Martti
    Åbo Akademi University.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    A Stokesian Dynamics Approach for Simulation of Magnetic Particle Suspensions2016Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 90, nr SI , s. 70-76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 11.
    Sand, Anders
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Toivakka, Martti
    Åbo Akademi University.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Simulation of Magnetic Particle Suspensions Using the Stokesian Dynamics Technique2015Ingår i: Proceedings of Conference in Minerals Engineering 2015, Luleå: Luleå tekniska universitet, 2015Konferensbidrag (Övrigt vetenskapligt)
  • 12.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Project: Wet LlMS - Measurements and models2013Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 13.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Ultrasonic flow measurement methods applicable to wet low intensity magnetic separation2013Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this project the internal material transport processes of wet low-intensity magnetic separation (LIMS) is studied. The aim is to use results from experiments combined with published results to create a base for further research and development. During the initial work, presented here, the focus has been to develop an experimental platform and verify that ultrasound is a viable tool for flow measurement in suspensions with solids concentrations realistic for wet magnetic separation processes. The experiments have been carried out in a purpose built flow cell equipped with ultrasonic transducers and supported by a pump, mixer and necessary data accusation electronics. In the first conference paper, ultrasonic velocity profiling is used to estimate flow velocity profiles, and initial results are presented. When applied to flows of mineral suspensions of high solids concentration, similar to those in wet LIMS, the method is unique in combining:* Non-intrusive measurements.* Operation by a single transducer element.* Relatively good spatial resolution.* Operation in opaque suspensions.* Fast sampling rate.In a second conference paper the signal processing behind the measurement method is investigated more thoroughly and focus is on robust profile estimation. The connection between solids concentration, ultrasonic transducer centre frequency and penetration depth is also investigated. In a publication the measurements are put in relation to the application of interest. It is shown that the methods are generally applicable and can be used in situations where variations in suspension flow velocity through narrow geometries are of interest.The novelty shown is that it is possible to measure flow velocity profiles through suspensions carrying at least 10 vol% solids. For solids concentrations of 5 vol% or less it is possible to get a velocity profile through at least 50 mm of suspension. Results from measurements in suspensions of such high solids concentration combined with such long penetration depth have not been published before. The measurement method has gained attention from industry since it is generally applicable to narrow channel flows reachable from only one access point.

  • 14.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Wet Low-Intensity Magnetic Separation: Measurement methods and Modelling2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In the mining industry, ferromagnetic particles (e.g. magnetite) are concentrated using wet low-intensity magnetic separation (LIMS). Mineral particles in suspension with water are pumped into the separator tank, and a magnetic concentrate is extracted by use of magnetic forces. The performance of the process is to a large extent controlled by the internal flow conditions in the separator, governed by process and machine settings. Due to the machine design these settings are not independent, and in some cases it can be difficult to reach optimal process performance. The main purpose of this work has been to find a measurement method capable of monitoring internal material transport in the wet LIMS, and use these data, together with numerical flow modelling, to get an increased understanding about the separation process.Since the mineral slurry entering the separator is essentially opaque, and the solids concentration is rather high, an ultrasound-based method was selected for the internal measurements. It is of interest to monitor both the internal flow patterns, as well as material build-up resulting from the magnetic field. The method development and evaluation proceeded in steps with increasing complexity, with later stages building on experience from the former. Initial measurements were done in model systems with simple geometries, and over a range of flow velocities corresponding to flow velocities in full-scale magnetic separators. Additional measurements were done on model systems under influence of a magnetic field of varying strength. After the measurement methods were verified in controlled laboratory conditions they were evaluated in real world conditions; in situ at the LKAB pilot plant in Malmberget, Sweden.For the pilot scale experiments a setup with two ultrasound transducers, mounted at the bottom of the separator tank, was used. The factors included in the designed experiment were the feed solids concentration, drum rotational speed, position of the concentrate weir, and the magnet assembly angle. Based on this investigation the drum rotational speed was the factor having 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 was confirmed. The factor with strongest influence on this flow is also the drum rotational speed, together with the magnet assembly angle. Using this method it is possible 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 ultrasound based measurement system resulting from this work measures particle velocity based on a cross-correlation principle. Two consecutive ultrasound pulse-echo signals are cross-correlated piece-wise, to obtain a local velocity estimate. By measuring the suspension flow from two directions, using two transducers, 2D velocity vectors can be estimated. Using the same measured data, but instead studying how the spectral contents of the signal vary with axial distance from the transducer, a qualitative measure of variations in local solids concentration can be obtained.During this work several aspects of wet LIMS have been studied, with focus on the internal material transport processes inside the separators. State-of-the-art measurement methods have been utilized to monitor the material flow inside the separators. Particle capture and entrainment have been studied on the particle level using numerical flow modelling. Measurement results have been linked to operational conditions of the separators. The insights gained, and the methods developed, have generated new possibilities to control, optimise, and develop the wet LIMS process.Keywords: Wet low-intensity magnetic separation, magnetite beneficiation, in-line process monitoring, pulse-echo ultrasound, ultrasonic velocity profiling, solids concentration, signal processing, windowed cross-correlation, power spectral density, numerical flow modelling.

  • 15.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Direct measurement of internal material flow in a bench scale wet Low-Intensity Magnetic Separator2016Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 91, s. 55-65Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 16.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Direct measurement of internal material flow in bench scale wet Low-Intensity Magnetic Separator2015Ingår i: Proceedings of Physical Separation '15, Minerals Engineering International , 2015Konferensbidrag (Övrigt vetenskapligt)
  • 17.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Evaluation of the applicability of ultrasonic velocity profiling in conditions related to wet low intensity magnetic separation2013Ingår i: Proceedings of Physical Separation '13, Minerals Engineering International , 2013Konferensbidrag (Övrigt vetenskapligt)
  • 18.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Evaluation of the applicability of ultrasonic velocity profiling in conditions related to wet low intensity magnetic separation2014Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 62, s. 2-8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 19.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Robust estimation of particle velocity profiles in high concentration magnetite suspensions2013Ingår i: Proceedings of the 2013 International Congress on Ultrasonics / [ed] Gan Woon Siong; Lim Siak Piang; Khoo Boo Cheong, Singapore: Research Publishing Services, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 20.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Ultrasonic velocity profiling of flows related to wet low intensity magnetic separation2013Ingår i: Conference in Minerals Engineering: Luleå 5-6 February 2013 / [ed] Jan Rosenkranz; Tommy Karlkvist, Luleå, 2013, s. 157-168Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    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.

  • 21.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Towards the measurement of local particle mass fractions in magnetite suspensions2014Ingår i: 2014 IEEE International Ultrasonics Symposium, IUS 2014: Chicago, Ill, 3-6 September 2014, Piscataway, NJ: IEEE Communications Society, 2014, s. 939-942Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 22.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Internal flow measurements in pilot scale wet low-intensity magnetic separation2016Ingår i: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 155, s. 55-63Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 23.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Monitoring Mineral Slurry Flow using Pulse-Echo Ultrasound2016Ingår i: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 50, s. 135-146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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

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