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  • 1. Alatalo, Johanna
    et al.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Qualitative statistical analysis of simulated data from a pilot scale mill2011Ingår i: Particle-based Methods - Fundamentals and Applications / [ed] Eugenio Oñate; D.R.J. Owen, Barcelona: International Center for Numerical Methods in Engineering (CIMNE), 2011, s. 43-51Konferensbidrag (Refereegranskat)
    Abstract [en]

    Grinding is the process of reducing a particle size distribution of an extracted ore and is commonly performed in a tumbling mill. It is a complex procedure and there is a lack of knowledge of what really happens inside the mill. A number of pilot-scale experiments were done at LKAB's pilot plant at Malmberget, Sweden [1]. In this particular pilot mill, a continuous charge measurement system is installed in one of the lifters and it gives a deflection signal produced by the mill charge. From this signal it is possible to detect features correlated to the settings of the mill. Large, real experiments are very difficult to control and are of course, very costly and time consuming. A 10 cm slice of the mill was simulated with discrete element method (DEM) for different mill operating conditions. From the simulations a deflection signal was extracted and validated against real data. There is a difference in the signal, mainly due to the lack of slurry in the simulations, but the behaviour when the mills operating conditions changes seems to be the same in both the simulated and the measured signals. To analyse the data from the simulation a statistical analysis on a full factorial design was done. Two levels of degree of filling of the mill, two different rotational speeds, two levels of friction and different types of particles were selected as factors. The response data are two angles: toe and shoulder angle. The toe angle is when the lifter hits the charge and the shoulder angle is when the lifter leaves the charge. The analysis show that the toe angle increases when the degree of filling is low and the rotational speed is high. It is also clear that the particle shape influences the charge behaviour. The simulated changes correspond to changes detected in pilot mill runs. This is important since it validates the DEM model. In essence, mill simulations are easily done and the changes of factor levels cause the simulated mill to react in similar manner as in real cases. One advantage is that in simulations one factor can be isolated and changed while the others are kept at constant values, which in turn creates the possibility to investigate one factor at a time. In real experiments, the factors are more dependent on each other and there is a very high disturbance from noise.

  • 2.
    Alatalo, Johanna
    et al.
    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.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Comparing experimental measurements of mill lifter deflections with 2D and 3D DEM predictions2010Ingår i: Discrete element methods: simulations of discontinua : theory and applications / [ed] Antonio Munjiza, London: School of Advanced Study, University of London, 2010Konferensbidrag (Refereegranskat)
  • 3.
    Alatalo, Johanna
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Evaluation of data from a pilot scale pebble mill2011Ingår i: Conference in minerals engineering: Luleå, 8-9 February 2011 / [ed] Johanna Alatalo, Luleå: Luleå tekniska universitet, 2011Konferensbidrag (Övrigt vetenskapligt)
  • 4.
    Alatalo, Johanna
    et al.
    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.
    Tano, Kent
    LKAB, Research & Development, 983 81 Malmberget.
    Influence of charge type on measurements with an in-mill sensor2012Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 39, s. 262-267Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 5.
    Alatalo, Johanna
    et al.
    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.
    Tano, Kent
    LKAB.
    Influence of pebble mill operating conditions on measurements with an in-mill sensor2011Ingår i: Minerals & metallurgical processing, ISSN 0747-9182, Vol. 28, nr 4, s. 193-197Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Autogenous grinding is a process of reducing the particle size distribution of an extracted ore by using the ore itself as the grinding media. It is a process that is difficult to control and there is a lack of knowledge of the events occurring inside the mill. To find out more about how the mill behaves under different processing conditions, a full factorial test was performed with iron ore in a pilot-scale pebble mill at the LKAB R&D facility in Malmberget. To complement this work, a strain gauge detector was embedded in one of the mill’s rubber lifters, the Metso Minerals continuous charge measurement (CCM) system, and was used to get more information about the charge dynamics. The data from the experiments has been analyzed. For production purposes, an increase in the number of particles smaller than 45 μm can be regarded as a probable increase in the production rate. The analysis shows that there will be an increase in fines at 65% of critical speed, especially when the mill is 45% full. This setting will also increase the power consumption, but improves the grindability of the ore even more. The deflection of the lifters is smaller for lower critical speeds. A higher degree of filling also gives a smaller toe angle and a higher shoulder angle as expected.

  • 6. Alatalo, Johanna
    et al.
    Öberg, Eva
    LKAB.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Verifierig av datorsimulerad kapacitetsökning vid anrikningsverket i Malmberget2006Ingår i: Konferens i mineralteknik / [ed] Marianne Thomaeus; Eric Forssberg, Föreningen Mineralteknisk Forskning / Swedish Mineral Processing Research Association , 2006Konferensbidrag (Övrigt vetenskapligt)
  • 7.
    Bark, Glenn
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Wanhainen, Christina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Textural setting of gold and its implications on mineral processing: preliminary results from three gold deposits in northern Sweden2013Ingår i: Mineral deposit research for a high-tech world: Proceedings of the 12th Biennial SGA Meeting, 12–15 August 2013, Uppsala, Sweden, Uppsala: Sveriges Geologiska Undersökning , 2013, s. 302-305Konferensbidrag (Refereegranskat)
    Abstract [en]

    Within the European Union (EU27) the two most important gold producers are Finland and Sweden, covering more than two thirds of the European market. Due to the high gold prize mining companies are looking to extract more of the metal by improving recovery. We have done textural analysis on three gold-bearing deposits to better understand how the gold-textures seen in drill cores might affect the processing of different gold-ore types. In the Nautanen IOCG deposit, gold deportment is different whether gold is associated with pyrite or magnetite, and this must be considered when optimising the future mine and process planning. In the VMS-type Kristineberg deposit, the gold is associated with pyrite, sphalerite, and galena. Low gold recoveries from flotation could be explained by the occurrence of gold-inclusions in the pyrite. In the epigenetic Svartliden lode gold deposit, the gold is rather coarse-grained and associated with arsenopyrite-löllingite, and silicates. The relatively large grain size of gold can result in incomplete breakdown of the largest gold grains in the cyanide leaching process. To properly understand gold deportment in ores and to be able to improve mine planning and predict metal recoveries a comprehensive textural analysis of gold in drill core-samples is essential.

  • 8. Berglund, Gun
    et al.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Praktisk och teoretisk utvärdering av minipilotförsök på Laisvallmalm1989Ingår i: Konferens i mineralteknik: Luleå 14-16 februari 1989 / [ed] Börje Sköld; Eric Forssberg, MinFo , 1989, s. 97-109Konferensbidrag (Övrigt vetenskapligt)
  • 9.
    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.

  • 10.
    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.

  • 11.
    Forssberg, Eric
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Antti, Britt-Marie
    Luleå University of Technology.
    Pålsson, Bertil
    Computer-assisted calculations of thermodynamic equilibria in the chalcopyrite-ethyl xanthate system1984Ingår i: Reagents in the Minerals Industry: papers presented in Rome, Italy, from 18 to 21 September, 1984 / [ed] Michael J. Jones; R. Oblatt, London: The Institution of Mining and Metallurgy , 1984, s. 251-264Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Calculations show that thermodynamic data can be used to construct pulp chemistry models that satisfactorily describe events in mineral pulps. The usefulness of such models can be enhanced by the insertion of kinetic restrictions derived from analyses of mineral pulps from commercial-scale operations. A number of interesting findings concerning the chalcopyrite-ethyl xanthate system are demonstrated. As it is possible to calculate an operating line for any given flotation system, the calculation results can be compared at all times with practical experience and measurements of flotation processes.

  • 12.
    Forssberg, Eric
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Frykfors, Carl-Otto
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Study of the kinteics of flotation in a bulk flotation circuit for galena and sphalerite1983Ingår i: International Mineral Processing Congress: IMPC 14, Montreal, 1983Konferensbidrag (Refereegranskat)
    Abstract [en]

    This project involved detailed sampling from an individual flotation cell as well as sampling of concentrates and middlings from cells in the rougher and scavenger flotation stages. The study shows how the total mass distribution and the distribution of galena and sphalerite change in the course of rougher and scavenger flotation. These changes have been evaluated in terms of flotation kinetics, and the residual quantity functions for galena and sphalerite in rougher and scavenger flotation are given. The frequency distribution of flotation activity has also been obtained for galena and sphalerite in rougher and scavenger flotation.

  • 13.
    Forssberg, Eric
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Jönsson, H.R.
    LKAB, Research & Development, 983 81 Malmberget.
    Pålsson, Bertil
    Full scale test of process water reuse in a complex sulphide ore circuit1985Ingår i: Flotation of sulphide minerals / [ed] Eric Forssberg, Elsevier, 1985, s. 197-217Konferensbidrag (Refereegranskat)
  • 14.
    Hahne, Roger
    et al.
    LKAB.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Samskog, Per-Olof
    Ore characterisation for - and simulation of - primary autogenous grinding2003Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 16, nr 1, s. 13-19Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 15.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Alatalo, Johanna
    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.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Prediction of contact forces between a grinding charge and mill lifters2009Ingår i: 12th European Symposium on Comminution and Classification ESCC 2009, 2009Konferensbidrag (Refereegranskat)
  • 16.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Hammarberg, Samuel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Lindkvist, Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Preliminary validation of a new way to model physical interactions between pulp, charge and mill structure in tumbling mills2019Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 130, s. 76-84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 17.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Modelling of fluid, particle and structure interactions in a tumbling ball mill for grinding of minerals2014Konferensbidrag (Refereegranskat)
  • 18.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Hammarberg, Samuel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindkvist, Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A Particle Based Modelling Approach for Predicting Charge Dynamics in Tumbling Ball Mills2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wet grinding of minerals in tumbling mills is a highly important process in the mining industry. During grinding in tumbling mills, lifters submerge into the charge and create motions in the ball charge, the lifters is exposed for impacts and shear loads that will wear down the lifters. Increased loading can accelerate the wear and the lining has to be replaced. Replacing the lining is an expensive and time consuming operation that is preferred to be done within planned maintenance stops. Prediction of the charge motion and wear rate for different grinding operations and linings are therefore desirable to predict the lining life.

     

    Modelling of wet grinding in tumbling mills that include pulp fluid and its interaction with both the grinding balls and the mill structure is an interesting challenge and some different approaches have been suggested, see [1-2]. For an effective and successful prediction, the numerical model has to be able to handle the pulp fluid and its simultaneous interactions with both the ball charge and the mill structure, in a computationally efficient approach. In this work, the pulp fluids are modelled with a Lagrange based method called incompressible computational fluid dynamics, (ICFD), which 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 than the conventional CFD. The ICFD solver can be coupled to other solvers as in this case the finite element method, (FEM) solver for the mill structure and the discrete element method (DEM) solver for the ball charge. The combined ICFD-DEM-FEM model can predict both charge motion and responses from the mill structure, as well as the pulp liquid flow and pressure. The numerical grinding case presented here is validated against experimentally measured driving torque signatures from an instrumented small-scale batch ball mill, see [3]. This approach opens up the possible to predict the volume of the high-energy zone and optimise lifter design and operating conditions. The ICFD solver improve efficiency and robustness for studying wet grinding in tumbling mill systems and can predict the charge dynamics and the wear distribution in such systems.

     

    References

    [1]   Jonsén, P. et al., (2018). Preliminary validation of a new way to model physical interactions between pulp, charge and mill structure in tumbling mills. Minerals Enginering. Accepted for publication

    [2]   Jonsén, P., Stener, J.F., Pålsson, B.I. and Häggblad, H.-Å., (2015). Validation of a model for physical interactions between pulp, charge and mill structure in tumbling mills. Minerals Engineering, Vol. 73, 77–84.

    [3]   Jonsén, P. Stener, J. F. Pålsson, B. I. and Häggblad, H.-Å., (2013). Validation of tumbling mill charge induced torque as predicted by simulations. Minerals and Metallurgical Processing, vol. 30, No. 4, 220-225.

  • 19.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindkvist, Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Hammarberg, Samuel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    First attempt to do a full-body modelling of a tumbling mill based on first principles2018Ingår i: Conference in Minerals Engineering / [ed] Jan Rosenkranz, Bertil Pålsson, Tommy Karlkvist, 2018, s. 71-84Konferensbidrag (Refereegranskat)
    Abstract [en]

    To efficiently model wet grinding in tumbling mills is a difficult task. Because of the complex behaviour of the pulp with free surfaces and large deformations, the difficulty is usually that the method to represent and reproduce its movements is demanding and time consuming. In this work, an investigation of the possibility to efficiently model and simulate the whole mill body, including the pulp and the charge, and its simultaneous interactions with both the charge and the mill structure is presented. This is done by the ICFD method, which is a Lagrange based method that gives the opportunity to efficiently model the pulp free surface flow, and its interaction with grinding balls and mill structure. Validation is done against experimentally measured driving torque signatures from an instrumented small-scale batch ball mill equipped with an accurate torque meter, and charge movements captured from high-speed video. Numerical results are in good agreement with experimental torque measurements.  

  • 20.
    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.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A novel method for full-body modelling of grinding charges in tumbling mills2012Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 33, nr S1, s. 2-12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 21.
    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.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling of internal stresses in grinding charges2011Ingår i: Particle-based Methods – Fundamentals and Applications / [ed] E. Oñate; D.R.J. Owen, Barcelona: International Center for Numerical Methods in Engineering (CIMNE), 2011, s. 757-768Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Physically realistic methods are a necessity to close the gap between reality and numerical result in modelling of tumbling mills. 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. Both the breakage of ore particles and the wear of liners/ball media are closely linked to the charge motion. In this work, a ball charge and its interaction with the mill structure is modelled with the smoothed particle hydrodynamic (SPH) method. 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. The flexible rubber lifter and the lining are modelled with the finite element method (FEM). A hyper-elastic model governs the elastic behaviour of the rubber. The comminution process is complex and to include all phenomena that occur in a single numerical model is today not possible. Therefore, modelling the physical interaction between charge, mill structure and pulp liquid is the major goal in this work. The SPH-FEM model can predict responses of the mill structure e.g. stress and strain. All parts of the mill system will affect its response and the model gives the opportunity to study the influence of the mill structure and e.g. pressure and shear stresses in the charge. This computational model also makes it possible to predict, the contact forces for varying mill dimensions, liner combinations and pulp densities. By comparing numerical results with experimental measurement from grinding in a pilot mill equipped with an instrumented rubber lifter a validation is done. 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. This model gives information on the grinding process in tumbling mills and better correlation with experimental measurements

  • 22.
    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.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling of physical interactions between pulp, charge and mill structure in tumbling mills2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    To develop a tumbling mill model that includes 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) or smoothedparticle hydrodynamics (SPH) together with the finite element method (FEM). In such combination 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 using SPH. Wet milling with water and a magnetite pulp, for graded and mono-size charges are numerically modelled and validated. The charge behaviour and its interaction with the mill structure are studied. An important part of the model is the coupling between DEM and SPH elements. Sliding and impact along the contacting interfaces are important for the response of the model. In the present work, the contact between the grinding balls and the pulp is realized using a penalty based “nodes to node” contact. The combined SPH-DEM-FEM model presented here can 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 millequipped with an accurate torque meter. The simulated charge movement is also compared with high speed video of the charge movement for a number of cases. In conclusion, the SPH-DEM-FEM can predict the charge movement and driving torque with good agreement compared to experimental measurement for a wet tumbling mill process. In addition, the presented methodology is generic and can as well be applied to dry or wet stirred media mills of various configurations

  • 23.
    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.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Berggren, Andreas
    Technology and Development, Boliden Minerals, SE-93681 Boliden, Sweden.
    Modelling of the interaction between charge and lining in tumbling mills: Combination of numerical methods2011Konferensbidrag (Övrigt vetenskapligt)
  • 24.
    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.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Berggren, Andreas
    Boliden Mineral AB.
    Novel simulation methods for mill charges2011Ingår i: Conference in minerals engineering: Luleå, 8-9 February 2011 / [ed] Johanna Alatalo, Luleå: Luleå tekniska universitet, 2011Konferensbidrag (Övrigt vetenskapligt)
  • 25.
    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.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Berggren, Andreas
    Technology and Development, Boliden Minerals, SE-93681 Boliden, Sweden.
    Simulation of charge and structure behaviour in a tumbling mill2011Ingår i: 8th European LD-DYNA Users Conference May 23-24, 2011, Strasbourg, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    For a long time discrete element methods (DEM) has been used as simulation tools to gain insight into particulate flow processes. The mechanical behaviour in tumbling mills is complex. To include all phenomena that occur in a single numerical model is today not possible. A common approach is to model milling charges using the DEM assuming a rigid mill structure. To close the gap between reality and numerical models in milling, more physically realistic methods have to be used. In this work, the finite element method (FEM) and the smoothed particle hydrodynamic (SPH) method are used together to model a ball mill charge in a tumbling mill. The mesh free formulation and the adaptive nature of the SPH method result in a method that handles extremely large deformations and thereby suits for modelling of grinding charges. The flexible rubber lifter and the lining are modelled with the finite element method. The mill structure consists of rubber lifter and liners and a mantel made of solid steel. For the elastic behaviour of the rubber, a Blatz-Ko hyper-elastic model is used. The supplier of the lining provided experimental data for the rubber. 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. This computational model makes it possible to predict charge pressure and shear stresses within the charge. It is also possible to predict contact forces for varying mill dimensions and liner combinations.

  • 26.
    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

  • 27.
    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.

  • 28.
    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.

  • 29.
    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.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Berggren, Andreas
    Technology and Development, Boliden Minerals, SE-93681 Boliden, Sweden.
    Charge and structure behaviour in a tumbling mill2010Ingår i: The Fifth International Conference on Discrete Element Methods: Proceedings / [ed] Antonio Munjiza, London: Research Publishing Services, 2010, s. 490-495Konferensbidrag (Refereegranskat)
    Abstract [en]

    The grinding process in tumbling mills is complex and to include all phenomena that occur in a single numerical model is today not possi-ble. 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 ele-ment (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 modelled with the distinct element method (DEM). The deflection profile obtained from DEM-FE simulation shows a reasonably good correspondence to pilot mill measurements. The approach presented here is a contribution to the validation of DEM-FE simulations and an introduction to the description of a bend-able 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. This is a fol-low-up work to previous preliminary result from a mono-size ball charge interaction study

  • 30.
    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.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Berggren, Andreas
    Technology and Development, Boliden Minerals, SE-93681 Boliden, Sweden.
    Modelling of the interaction between charge and lining in tumbling mills2010Ingår i: Bergforsk 2010: Mineral Supply - a Grand Challange and Opportunity / [ed] Göran Bäckblom, 2010, s. 18-20Konferensbidrag (Övrigt vetenskapligt)
  • 31.
    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.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Berggren, Andreas
    Technology and Development, Boliden Minerals, SE-93681 Boliden, Sweden.
    Prediction of mill structure behaviour in a tumbling mill2010Ingår i: Conference in Minerals Engineering: Luleå, 2 -3 februari 2010 / [ed] Johanna Alatalo, Luleå: Luleå tekniska universitet, 2010, s. 85-98Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    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 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 presented here 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. This is a follow-up work to previous preliminary result from a mono-size ball charge interaction study.

  • 32.
    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

  • 33.
    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.

  • 34.
    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.

  • 35.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Tano, Kent
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Berggren, Andreas
    Boliden Mineral AB.
    Prediction of mill structure behaviour in a tumbling mill2011Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 24, nr 3-4, s. 236-244Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 36.
    Karlkvist, Tommy
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Fredriksson, Andreas
    R&D Mineral Processing, LKAB.
    Rao, Hanumantha
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Novel alkyl aminodicarboxylate reagents for mineral specific flotation2016Ingår i: 2016 SME Annual Conference and Expo: The Future for Mining in a Data-Driven World, Phoenix, United States, 21 - 24 February 2016, New York: Society for Mining, Metalurgy and Exploration, 2016, s. 807-810Konferensbidrag (Refereegranskat)
    Abstract [en]

    Separation of different calcium minerals have long been an interesting and challenging problem. In this investigation calcium mineral separation is examined by: microflotation, zeta potential measurement and adsorption, using novel collectors having two functional groups instead of one. In theory, by varying the distance between the functional groups, it could be possible to preferentially target one calcium mineral by matching the spatial distance between the sites on the mineral surface. In this investigation two new surfactants have been tested to estimate their ability to float apatite and/or calcite.Preliminary findings show that an increase in distance between the functional groups favors one mineral over the other, and this might be due to differences in the mineral surface structure.

  • 37. Kimmehed, Lennart
    et al.
    Nilsson, Elisabeth
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Alternativa användningsområden för grafit-skiffer från Vittangi1976Rapport (Övrigt vetenskapligt)
  • 38.
    Larsson, Cecilia
    et al.
    LKAB.
    Adolfsson, Göran
    LKAB.
    Siikavaara, Johan
    LKAB.
    Tano, Kent
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Fraktionerad autogenmalning vid LKAB Kiruna: bättre malning?2004Ingår i: Konferens i mineralteknik / [ed] Marianne Thomaeus; Eric Forssberg, Föreningen Mineralteknisk Forskning / Swedish Mineral Processing Research Association , 2004Konferensbidrag (Övrigt vetenskapligt)
  • 39.
    Larsson, Simon
    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.
    Parian, Mehdi
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Preliminary validation of a stirred media mill model2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wet fine grinding is an important process in the minerals industry. Modelling of wet grinding in stirred media mills is challenging since it requires the simultaneous modelling of grinding media consisting of a huge number of small grinding bodies, moving internal stirrer, and the pulp fluid. All of them in interaction with each other. In the present study, wet grinding in a stirred media mill is studied using coupled incompressible computational fluid dynamics (ICFD) and discrete element method (DEM) and finite element method (FEM) simulations. The DEM is used to model the grinding media, and the pulp fluid flow is modelled using the ICFD. Moreover, the FEM is used to model the structure of the mill body and is in combination with DEM used to estimate the wear rate in the system. The present implementation of the coupled ICFD-DEM-FEM preserves the robustness and efficiency of both methods, and it gives the possibility to use large time steps for the fluid with very low computation times.

  • 40.
    Lindvall, Manfred
    et al.
    Boliden Mineral AB.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Studie av möjligheterna till källtermsbegränsning av vittringspotential: avskiljning av tunga mineral ur restproduktströmmar2004Rapport (Övrigt vetenskapligt)
  • 41.
    Lindvall, Manfred
    et al.
    Boliden Mineral AB.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Studie av möjligheterna till källtermsbegränsning av vittringspotential: datafångst vid prospektering och drift. State-of-the-art-rapport2004Rapport (Övrigt vetenskapligt)
  • 42.
    Lishchuk, Viktor
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Lund, Cecilia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Koch, Pierre-Henri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Mattias, Gustafsson
    LKAB.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Geometallurgical characterisation of Leveäniemi iron ore: Unlocking the patterns2019Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 131, s. 325-335Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As part of a geometallurgical program for the Leveänimei iron ore mine, the Davis tube was used as proxy to classify ore types, predict iron recoveries in wet low-intensity magnetic separation (WLIMS), and to estimate liberation of mixed particles. The study was conducted by testing 13 iron ore samples with a Davis tube and a laboratory WLIMS. Ore feed was studied for modal mineralogy and liberation distribution with Automated Scanning Electron Microscopy. Data analyses to detect the patterns and data dependencies were done with multivariate statistics: principal component analysis, and projection to latent structures regression. Results show that a simple index (XLTU) based on mass pull (yield) in the Davis tube is capable of easy classification of magnetite ores. Using Davis tube mass pull and iron recovery, together with iron and Satmagan head grades may predict iron recovery in WLIMS. Also, the variability in Fe-oxides liberation pattern for magnetite semi-massive ores can be explained with the chemical composition of the Davis tube concentrate. It is concluded that the Davis tube test is better used only for marginal ores, since iron oxide minerals tend to be fully liberated in high-grade magnetite massive ores after grinding. The developed models may be used in populating a production block model.

  • 43.
    Lishchuk, Viktor
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Lund, Cecilia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Koch, Pierre-Henri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Mattias, Gustafsson
    LKAB.
    Geometallurgical characterisation of Leveäniemi iron ore: unlocking the patterns2018Ingår i: Conference in Minerals Engineering / [ed] Jan Rosenkranz, Bertil Pålsson, Tommy Karlkvist, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Geometallurgy of iron ores aims at linking geological variability and responses in the beneficiation process by a wide usage of automated mineralogy, proxy metallurgical tests (e.g., Davis tube) and process simulation.

    In this study several patterns from iron ore processing, in context of their textural description, are revealed and modelling is attempted. The first one is an ore classification method with a novel quality estimator XLTU. The second one is an algorithm for predicting iron recovery in wet low intensity magnetic separator (WLIMS). The last one is predicting liberation distribution of iron oxides. Process variables are generated with a Davis tube and a WLIMS test. All streams are chemically characterised. Ore feed was studied for modal mineralogy and liberation distribution with QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy). Post-processing for detecting the patterns and data dependencies was done with multivariate statistics: principal component analysis (PCA), and projection to latent structures regression (PLS). The study was done on 13 apatite iron ore type samples from the Leveäniemi mine (LKAB).

    It is concluded that Davis tube test is better used only for marginal ores, since iron oxide minerals tend to be fully liberated in high grade magnetite massive ores after grinding. In addition, they will give high recovery and high mass pull in a Davis tube test.

    The developed models can be used in populating a production block model in the future. Furthermore, future work should cover larger variability of marginal ores in terms of Fe grades and modal mineralogy (e.g. feldspar, amphibole, apatite dominated). Variability of grain size distribution ought to be included into future studies.

  • 44. Oghazi, Pejman
    et al.
    Lund, Cecilia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Applying traceability in a mine-to-mill context by using particle texture analysis2010Ingår i: SME Annual Meeting and Exhibit 2010: Phoenix, Arizona, USA, 28 February - 3 March 2010, Red Hook, NY: Curran Associates, Inc., 2010, s. 7-11Konferensbidrag (Refereegranskat)
    Abstract [en]

    It is possible to have traceability in the mining industry, by parameters and signatures like particle mineralogy, mineral association, texture and mineral liberation. The study is on an apatite-iron ore deposit at Malmberget, Sweden, and characterises an ore body both mineralogically and texturally in a quantitative manner by using analytical methods like optical microscopy, microprobe (EMPA) and an automatic SEM based system, Particle Texture Analysis (PTA). The mineralogy was evaluated by PTA and characterized by modal mineralogy, mineral liberation and mineral associations. Magnetite has a simple outline and straight grain boundaries and the gangue minerals have a finer particle size with a more complicated texture. The PTA analysis also shows that apatite is associated to magnetite as mixed particles, while smaller grains of magnetite are inclusions in feldspar. Result from particle texture analysis shows that there is a connection which link to the mine-to-mill context, and it may be used to create traceability. This link is not the associations of the main ore mineral magnetite, nor the modal mineralogy. Instead, it is the mineral associations of contaminating minerals (apatite and feldspar) that appear to be most promising since they survive from mine to mill. The modal mineralogy may be used to understand how contaminating minerals break into or out of particle size fraction during grinding.

  • 45.
    Oghazi, Pejman
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Comparing the mineralogical characterization of iron ore by using QEMSCAN and PTA2011Ingår i: 10th International Congress for Applied Mineralogy (ICAM): Trondheim, August 2011 / [ed] Maarten A.T.M. Broekmans, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Automatic scanning systems can be used to detect valuable minerals in polished sections. These instruments have now reached a maturity level for the actual analysis, but since they generate a lot of information the bottleneck is now the interpretation of the data flow to get quantitative information. For example, today most industries are interested to use automated scanning system to achieve better products or to simplify the process by having better knowledge of the material that they are using in production. In this case two methods: Particle Texture Analysis (PTA) and QEMSCAN are checked for differences. Measured properties were modal mineralogy, mineral associations and mineral liberations in several samples over the same size fraction 38-53μm. The difference is the largest for the degree of liberations, probably since this measure is sensitive for the computational assumptions made.

  • 46. Oghazi, Pejman
    et al.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    An attempt to apply traceability to grinding circuits2007Ingår i: Conference in Mineral Processing, Luleå, Sweden, February 6-7, 2007, 2007, s. 169-183Konferensbidrag (Övrigt vetenskapligt)
  • 47. Oghazi, Pejman
    et al.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Applying traceability to grinding circuits by using Particle Texture Analysis (PTA)2008Ingår i: Proceedings of Communion 08: Falmouth, UK, June 17-20 2008, Minerals Engineering International , 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    LKAB has started a new pelletizing plant at Malmberget, where the raw material will be a mix of ores from Kiruna and Malmberget. The new plant necessitated an investment in a new grinding section in the concentrator. As usual, the new section has larger mills. It also lacks the wet cobbing stage present in the old sections.Comparing the results from the new section with the old sections show that they give similar results. There are slight variations; the older mills produce a steeper final particle size distribution. Also, it appears that the new mills are more efficient, since they have higher calculated grindability indices.To better understand the differences between the sections, and the process implications of the new grinding section, a combination of Particle Texture Analysis (PTA) and the statistical method Multivariate Analysis (MVA) is used. It shows that it is possible to identify and follow systematic changes in the particle morphology of the mill products. Also, that there are differences between the old and new grinding sections.

  • 48. Oghazi, Pejman
    et al.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Tano, Kent
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Applying traceability to grinding circuits by using Particle Texture Analysis (PTA)2009Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 22, nr 7-8, s. 710-718Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    LKAB has started a new pelletizing plant at Malmberget, where the raw material will be a mix of ores from Kiruna and Malmberget. The new plant necessitated an investment in a new grinding section in the concentrator. As usual, the new section has larger mills. It also lacks the wet cobbing stage present in the old sections.Comparing the analysis data from the new grinding section with the old grinding sections it shows that they give similar results. There are slight variations; the older mills produce a steeper final particle size distribution. Also, it appears that the new mills are more efficient, since they have higher calculated grindability indices.To better understand the differences between the sections, and the process implications of the new grinding section, a combination of Particle Texture Analysis (PTA) and the statistical method multivariate data analysis (MVDA) is used. It shows that it is possible to identify and follow systematic changes in the particle morphology of the mill products. Also, that there are differences in process mineralogical aspect between the old and new grinding sections.

  • 49.
    Oghazi, Pejman
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Tano, Kent
    Classifying best access points for return of external flows into flowsheets2011Ingår i: Open Mineral Processing Journal, ISSN 1874-8414, E-ISSN 1874-8414, Vol. 4, s. 1-6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    External flows are process streams that come from auxiliary processes or events. They are re-routed into the ordinary flowsheet since they are thought to be too valuable to be sent to any tailings pond. External flows come from multiple sources, e.g. drainage sumps, spillage thickeners, depleted products etc. Therefore, external flows may fit or notfit into an existing flowsheet depending on several factors like, flow rate frequency, dilution ratio variation, chemical and mineralogical composition, particle size or particle morphology. By using Particle Texture Analysis to investigate external flows and compare them with existing ordinary flows it is possible to pinpoint from a process mineralogy via point to what extent the external flow fits into the ordinary processing flowsheet. Results from this information category helps to reach a higher quality of process knowledge and control for every step in the concentrator. Results show that some recycled flows reconnected to the main flow are not connected to the best point. A side effect of the analysis is that some flows may be sent to later grinding stages. Thus, decreasing the load on the primary mill, and increasing the retention time.

  • 50. Oghazi, Pejman
    et al.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Tano, Kent
    LKAB, Research & Development, 983 81 Malmberget.
    Classifying best access points for return of external flows into flowsheets2010Ingår i: Comminution '10: Cape Town, South Africa, April 13-16, 2010, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    External flows are process streams that come from auxiliary processes or events. They are re-routed into the ordinary flowsheet, since they are thought to be too valuable to be sent to any tailings pond. External flows come from multiple sources, e.g., drainage sumps, spillage thickeners, depleted products etc. Therefore, external flows may fit or not fit into an existing flowsheet depending on several factors like, flow rate frequency, dilution ratio variation, chemical and mineralogical composition, particle size or particle morphology. By using Particle Texture Analysis (PTA) to investigate external flows and compare them with existing ordinary flows, it is possible to pin-point from a process mineralogy point of view to what extent the external flow in question fits into the ordinary processing flowsheet. Results from this category of information helps to reach a higher quality of process knowledge and control for every step in the concentrator. Result from analyses show that some re-routed flows that are reconnected to the main flow are not connected to the best point. A side effect of the analysis is that it indicates that some flows may be sent to later grinding stages. Thus, decreasing the load on the primary mill, and increasing its retention time

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