| 1. |
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| 2. |
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| 3. |
- Alatalo, Johanna, et al.
(författare)
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Influence of charge type on measurements with an in-mill sensor
- 2012
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 39, s. 262-267
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Alatalo, Johanna, et al.
(författare)
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Influence of pebble mill operating conditions on measurements with an in-mill sensor
- 2011
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Ingår i: Minerals & metallurgical processing. - 0747-9182. ; 28:4, s. 193-197
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Alatalo, Johanna, et al.
(författare)
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Qualitative statistical analysis of simulated data from a pilot scale mill
- 2011
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Ingår i: Particle-based Methods - Fundamentals and Applications. - Barcelona : International Center for Numerical Methods in Engineering (CIMNE). - 9788489925670 ; , s. 43-51
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 6. |
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| 7. |
- Bark, Glenn, et al.
(författare)
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Textural setting of gold and its implications on mineral processing: preliminary results from three gold deposits in northern Sweden
- 2013
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Ingår i: Mineral deposit research for a high-tech world. - Uppsala : Sveriges Geologiska Undersökning. - 9789174032079 ; , s. 302-305
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 8. |
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| 9. |
- Carlert, Sara, et al.
(författare)
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Predicting intestinal precipitation : a case example for a basic BCS class II drug
- 2010
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Ingår i: Pharmaceutical research. - : Springer Science and Business Media LLC. - 0724-8741 .- 1573-904X. ; 27:10, s. 2119-2130
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To investigate the prediction accuracy of in vitro and in vitro/in silico methods for in vivo intestinal precipitation of basic BCS class II drugs in humans. METHODS: Precipitation rate of a model drug substance, AZD0865 (pKa = 6.1; log K(D) = 4.2), was investigated in vitro using simulated intestinal media, and calculations of the crystallization rates were made with a theoretical model. Human intestinal precipitation was estimated by analysis of pharmacokinetic data from clinical studies at different doses. RESULTS: All in vitro models predicted rapid drug precipitation, where the intestinal concentration of dissolved AZD0865 at the highest dose tested was expected to decrease to half after less than 20 min. However, there was no indication of precipitation in vivo in humans as there was a dose proportional increase in drug plasma exposure. The theoretical model predicted no significant precipitation within the range of expected in vivo intestinal concentrations. CONCLUSIONS: This study indicated that simple in vitro methods of in vivo precipitation of orally administered bases overpredict the intestinal crystalline precipitation in vivo in humans. Hydrodynamic conditions were identified as one important factor that needs to be better addressed in future in vivo predictive methods.
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| 10. |
- Carlson, Johan, et al.
(författare)
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In-Situ Monitoring of Particle Velocities and Solids Concentration Variations in wet Low-Intensity Magnetic Separators
- 2015
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Ingår i: 2015 IEEE International Ultrasonics Symposium, IUS 2015. - Piscataway, NJ : IEEE Communications Society. - 9781479981823
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 11. |
- Carlson, Johan, et al.
(författare)
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Monitoring local solids fraction variations in multiphase flow using pulse-echo ultrasound
- 2015
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Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3892. ; 70, s. 376-379
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 12. |
- Fjalldal, S., et al.
(författare)
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Detailed assessment of hypothalamic damage in craniopharyngioma patients with obesity
- 2019
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Ingår i: International Journal of Obesity. - : Springer Science and Business Media LLC. - 0307-0565 .- 1476-5497. ; 43:3, s. 533-544
-
Tidskriftsartikel (refereegranskat)abstract
- Background/objectives: Hypothalamic obesity (HO) occurs in 50% of patients with the pituitary tumor craniopharyngioma (CP). Attempts have been made to predict the risk of HO based on hypothalamic (HT) damage on magnetic resonance imaging (MRI), but none have included volumetry. We performed qualitative and quantitative volumetric analyses of HT damage. The results were explored in relation to feeding related peptides and body fat. Subjects/methods: A cross-sectional study of childhood onset CPs involving 3 Tesla MRI, was performed at median 22 years after first operation; 41 CPs, median age 35 (range: 17–56), of whom 23 had HT damage, were compared to 32 controls. After exclusions, 35 patients and 31 controls remained in the MRI study. Main outcome measures were the relation of metabolic parameters to HT volume and qualitative analyses of HT damage. Results: Metabolic parameters scored persistently very high in vascular risk particularly among HT damaged patients. Patients had smaller HT volumes compared to controls 769 (35–1168) mm3 vs. 879 (775–1086) mm3; P < 0.001. HT volume correlated negatively with fat mass and leptin among CP patients (rs = −0.67; P <.001; rs = −0.53; P = 0.001), and explained 39% of the variation in fat mass. For every 100 mm3 increase in HT volume fat mass decreased by 2.7 kg (95% CI: 1.5–3.9; P < 0.001). Qualitative assessments revealed HT damage in three out of six patients with normal volumetry, but HT damage according to operation records. Conclusions: A decrease in HT volume was associated with an increase in fat mass and leptin. We present a method with a high inter-rater reliability (0.94) that can be applied by nonradiologists for the assessment of HT damage. The method may be valuable in the risk assessment of diseases involving the HT.
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| 13. |
- Forssberg, Eric, et al.
(författare)
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Computer-assisted calculations of thermodynamic equilibria in the chalcopyrite-ethyl xanthate system
- 1984
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Ingår i: Reagents in the Minerals Industry. - London : The Institution of Mining and Metallurgy. - 0900488786 ; , s. 251-264
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 14. |
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| 15. |
- Forssberg, Eric, et al.
(författare)
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Study of the kinteics of flotation in a bulk flotation circuit for galena and sphalerite
- 1983
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Ingår i: International Mineral Processing Congress. - Montreal.
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 16. |
- Hahne, Roger, et al.
(författare)
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Ore characterisation for - and simulation of - primary autogenous grinding
- 2003
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Ingår i: Minerals Engineering. - 0892-6875 .- 1872-9444. ; 16:1, s. 13-19
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 17. |
- Hallén, Magnus, et al.
(författare)
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Cytogenetic abnormalities in a hemangiopericytoma of the spleen.
- 2002
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Ingår i: Cancer Genetics and Cytogenetics. - 0165-4608. ; 136:1, s. 62-65
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Tidskriftsartikel (refereegranskat)abstract
- To date, only 16 cytogenetically abnormal hemangiopericytomas (HP) have been reported. Despite this low number, some characteristic karyotypic features have already emerged: most HP are near-diploid and breakpoints in 12q13, 12q24, and 19q13 seem to be common, with t(12;19)(q13;q13) being a recurrent translocation. Here, we report the first case of a probably benign splenic HP with chromosomal abnormalities. The abnormal karyotype was 47,XX,t(5;22;11)(q31;q11;q13),+10. None of these abnormalities have previously been reported in HP, suggesting that the karyotypic pattern of splenic HP may differ from soft tissue HP.
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| 18. |
- Jonsén, Pär, et al.
(författare)
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A novel method for full-body modelling of grinding charges in tumbling mills
- 2012
-
Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 33:S1, s. 2-12
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 19. |
- Jonsén, Pär, et al.
(författare)
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A novel method for modelling of interactions between pulp, charge and mill structure in tumbling mills
- 2014
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 63, s. 65-72
-
Tidskriftsartikel (refereegranskat)abstract
- 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
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| 20. |
- Jonsén, Pär, 1971-, et al.
(författare)
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A Particle Based Modelling Approach for Predicting Charge Dynamics in Tumbling Ball Mills
- 2018
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Ingår i: ABSTRACTS. - : IACM. ; , s. 1385-1385
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 21. |
- Jonsén, Pär, et al.
(författare)
-
Charge and structure behaviour in a tumbling mill
- 2010
-
Ingår i: The Fifth International Conference on Discrete Element Methods. - London : Research Publishing Services. - 9780955117985 ; , s. 490-495
-
Konferensbidrag (refereegranskat)abstract
- 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
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| 22. |
- Jonsén, Pär, et al.
(författare)
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Development of physically based tumbling mill models
- 2014
-
Ingår i: Proceedings of XXIII International Mineral Processing Congress. - Santiago : IMPC. - 9789569393150
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 23. |
- Jonsén, Pär, et al.
(författare)
-
First attempt to do a full-body modelling of a tumbling mill based on first principles
- 2018
-
Ingår i: Conference in Minerals Engineering. ; , s. 71-84
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 24. |
- Jonsén, Pär, et al.
(författare)
-
Modelling and validation of interactions between pulp, charge and mill structure in tumbling mills
- 2013
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 25. |
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| 26. |
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| 27. |
- Jonsén, Pär, et al.
(författare)
-
Modelling of internal stresses in grinding charges
- 2011
-
Ingår i: Particle-based Methods – Fundamentals and Applications. - Barcelona : International Center for Numerical Methods in Engineering (CIMNE). - 9788489925670 ; , s. 757-768
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 28. |
- Jonsén, Pär, et al.
(författare)
-
Modelling of physical interactions between pulp, charge and mill structure in tumbling mills
- 2015
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Konferensbidrag (refereegranskat)abstract
- 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
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| 29. |
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| 30. |
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| 31. |
- Jonsén, Pär, et al.
(författare)
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Novel simulation methods for mill charges
- 2011
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Ingår i: Conference in minerals engineering. - Luleå : Luleå tekniska universitet. - 9789174392203
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 32. |
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| 33. |
- Jonsén, Pär, et al.
(författare)
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Prediction of mill structure behaviour in a tumbling mill
- 2010
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Ingår i: Conference in Minerals Engineering. - Luleå : Luleå tekniska universitet. - 9789174390971 ; , s. 85-98
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 34. |
- Jonsén, Pär, et al.
(författare)
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Prediction of mill structure behaviour in a tumbling mill
- 2011
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 24:3-4, s. 236-244
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 35. |
- Jonsén, Pär, 1971-, et al.
(författare)
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Preliminary validation of a new way to model physical interactions between pulp, charge and mill structure in tumbling mills
- 2019
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Ingår i: Minerals Engineering. - : Elsevier. - 0892-6875 .- 1872-9444. ; 130, s. 76-84
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 36. |
- Jonsén, Pär, et al.
(författare)
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Simulation of charge and structure behaviour in a tumbling mill
- 2011
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Ingår i: 8th European LD-DYNA Users Conference May 23-24, 2011, Strasbourg.
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 37. |
- Jonsén, Pär, et al.
(författare)
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Validation of a model for physical interactions between pulp, charge and mill structure in tumbling mills
- 2015
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 73, s. 77-84
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 38. |
- Jonsén, Pär, et al.
(författare)
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Validation of tumbling mill charge induced torque as predicted by simulations
- 2013
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Ingår i: 2013 SME Annual Meeting & Exhibit (SME 2013) and CMA 115th National Western Mining Conference. - Denver, CO, USA : Society for Mining, Metalurgy and Exploration. ; , s. 728-733
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 39. |
- Jonsén, Pär, et al.
(författare)
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Validation of tumbling mill charge induced torque as predicted by simulations
- 2013
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Ingår i: Minerals & metallurgical processing. - : Springer Science and Business Media LLC. - 0747-9182. ; 30:4, s. 220-225
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 40. |
- Karlkvist, Tommy, et al.
(författare)
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Novel alkyl aminodicarboxylate reagents for mineral specific flotation
- 2016
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Ingår i: 2016 SME Annual Conference and Expo. - New York : Society for Mining, Metalurgy and Exploration. - 9781510825659 ; , s. 807-810
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 41. |
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| 42. |
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| 43. |
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| 44. |
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| 45. |
- Larsson, Simon, et al.
(författare)
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A novel approach for modelling of physical interactions between slurry, grinding media and mill structure in wet stirred media mills
- 2020
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Ingår i: Minerals Engineering. - : Elsevier. - 0892-6875 .- 1872-9444. ; 148
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Tidskriftsartikel (refereegranskat)abstract
- Wet comminution is an important process in the mineral processing industry. Modelling of wet comminution in stirred media mills requires the simultaneous modelling of grinding media, a moving internal stirrer, and slurry. In the present study, a novel approach for modelling the physical interactions between slurry, grinding media and mill structure in a stirred media mill is presented. The slurry is modelled with the particle finite element method (PFEM). The grinding media is modelled using the discrete element method (DEM) and the mill structure is modelled using the finite element method (FEM). The interactions between slurry, grinding media and mill structure are modelled by two-way couplings between the PFEM, the DEM and the FEM models. The coupled model of the present study is used to predict the motion of slurry and grinding media, and to calculate the power draw during wet comminution in a pilot scale horizontal stirred media mill. Furthermore, the model is used to compare a Newtonian and a non-Newtonian model of the slurry, where the non-Newtonian model is used to capture experimentally observed shear-thinning. The coupled PFEM-DEM-FEM model preserves the robustness and efficiency of each of the methods and it gives the possibility to use large time increments for the fluid, greatly reducing the computational expense. The coupled model of the present work provide information on the complex dynamics of slurry and grinding media. The numerical model is shown to be a useful tool for increasing the knowledge and understanding of wet comminution in stirred media mills.
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| 46. |
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| 47. |
- Larsson, Simon, et al.
(författare)
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Preliminary validation of a stirred media mill model
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 48. |
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| 49. |
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| 50. |
- Lishchuk, Viktor, 1984-
(författare)
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Bringing predictability into a geometallurgical program : An iron ore case study
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The risks of starting, operating and closing mining projects have become higher than ever. In order to stay ahead of the competition, mining companies have to manage various risks: technical, environmental, legal, regulatory, political, cyber, financial and social. Some of these can be mitigated with the help of geometallurgy. Geometallurgy aims to link geological variability with responses in the beneficiation process by a wide usage of automated mineralogy, proxy metallurgical tests, and process simulation. However, traditional geometallurgy has neglected the non-technical aspects of mining. This has caused wide-spread discussion among researchers on the benefits of geometallurgy and its place in industry.In order to improve predictability in geometallurgy, such programs should cover planning, and the testing of hypotheses, and only then should there be an attempt to develop suitable technical tools. Such approach would ensure that those tools would be useful and are needed, not only from the technical point of view, but also from the users’ perspective. Therefore, this thesis introduces methodology on how to decrease uncertainty in the production planning and thus determine how much effort to put into decreasing uncertainty in geometallurgical programs.The predictability improvement of a geometallurgical program starts at the planning stage. The classification system developed here, through the survey (interviews) and literature review, indicates different ways to link geological information with metallurgical responses, and suggests areas where technical development is called for. The proposed developments can be tested before the start of the geometallurgical program with synthetic data. For the iron ore reference study (Malmberget), it was shown that implementation of geometallurgy is beneficial in terms of net present value (NPV) and internal rate of return (IRR), and building geometallurgical spatial model for the process properties (recovery and total concentrate tonnages), and that it requires fewer samples for making a reliable process prediction than concentrate quality. The new process and proxy for mineralogical characterisation models were developed as part of the geometallurgical program for the iron ore case study (Leveäniemi): an estimator of ore quality (்ܺ), a model for iron recovery in WLIMS, a model for iron-oxides liberation prediction. Additionally, it was found that DT may be applied only for studying marginal ores. The evaluation of different spatial process modelling methods showed that tree methods can be successfully employed in predicting non-additive variables (recoveries).
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