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  • 1.
    Ahmadzadeh, Farzaneh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Lundberg, Jan
    Remaining useful life prediction of grinding mill liners using an artificial neural network2013Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 53, s. 1-8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 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
    LKAB, Research & Development, 983 81 Malmberget.
    Influence of charge type on measurements with an in-mill sensor2012Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 39, s. 262-267Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 3. Andersson, Tobias
    et al.
    Thurley, Matthew
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan E.
    A machine vision system for estimation of size distributions by weight of limestone particles during ship loading2012Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 25, nr 1, s. 38-46Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 4.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Control oriented modeling of flow and size distribution in cone crushers2014Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 56, s. 81-90Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 5. Awe, Samuel Ayowole
    et al.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Selective leaching of arsenic and antimony from a tetrahedrite rich complex sulphide concentrate using alkaline sulphide solution2010Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 23, nr 15, s. 1227-1236Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 6.
    Awe, Samuel Ayowole
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sundkvist, Jan-Eric
    Boliden Mineral AB.
    Bolin, Nils-Johan
    Boliden Mineral AB.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Process flowsheet development for recovering antimony from Sb-bearing copper concentrates2013Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 49, s. 45-53Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 7.
    Awe, Samuel Ayowole
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sundkvist, Jan-Eric
    Boliden Mineral AB.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Formation of sulphur oxyanions and their influence on antimony electrowinning from sulphide electrolytes2013Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 53, s. 39-47Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 8.
    Ayyala, Sekhar
    et al.
    Luleå University of Technology.
    Subrahmanyam, T.V.
    Departmento de Geologia, CCE/UFRN, Campus Universitario, Natal.
    Pugh, R.J.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Effect of corrosion inhibitors on grinding and flotation of a lead-zinc ore1993Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 6, nr 8, s. 929-935Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 9.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Traceability in iron ore processing and transports2012Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 30, s. 44-51Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 10.
    Charikinya, Edson
    et al.
    Minerals to Metals Initiative, Department of Chemical Engineering, University of Cape Town.
    Robertson, J.
    Minerals to Metals Initiative, Department of Chemical Engineering, University of Cape Town.
    Platts, A.
    Minerals to Metals Initiative, Department of Chemical Engineering, University of Cape Town.
    Becker, Megan
    Minerals to Metals Initiative, Department of Chemical Engineering, University of Cape Town.
    Lamberg, Pertti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Bradshaw, Dee J.
    Minerals to Metals Initiative, Department of Chemical Engineering, University of Cape Town.
    Integration of mineralogical attributes in evaluating sustainability indicators of a magnetic separator2017Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 107, s. 53-62Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 11.
    Chehreh Chelgani, S.
    et al.
    Surface Science Western, Research Park, University of Western Ontario, Ontario, Canada.
    Hart, B.
    Surface Science Western, Research Park, University of Western Ontario, Ontario, Canada.
    Xia, L.
    Surface Science Western, Research Park, University of Western Ontario, Ontario, Canada.
    A TOF-SIMS surface chemical analytical study of rare earth element minerals from micro-flotation tests products2013Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 45, nr May, s. 32-40Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 12.
    Chelgani, Saeed Chehreh
    et al.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    Leißner, T.
    TU Bergakademie Freiberg, Freiberg, Germany.
    Rudolph, M.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany; TU Bergakademie Freiberg, Freiberg, Germany.
    Peuker, U. A.
    TU Bergakademie Freiberg, Freiberg, Germany.
    Study of the relationship between zinnwaldite chemical composition and magnetic susceptibility2015Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 72, s. 27-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 13.
    Cunha, Maria Lucelinda
    et al.
    Departamento de Ciência dos Materiais, FCT/UNL, Caparica.
    Gahan, Chandra Sekhar
    Menad, Nourreddine
    BRGM-EPI, ECO, 3, Avenue Claude Guillemin, Orléans.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Possibilities to use oxidic by-products for precipitation of Fe/As from leaching solutions for subsequent base metal recovery2008Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 21, nr 1, s. 38-47Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 14.
    Dinkla, Inez J.T.
    et al.
    Bioclear BV.
    Gonzalez-Contreras, Paula
    Sub-department of Environmental Technology, Wageningen University.
    Gahan, Chandra Sekhar
    SRM Research Institute, SRM University, Kattankulathur, Chennai.
    Weijma, Jan
    Sub-department of Environmental Technology, Wageningen University.
    Buisman, Cees J.N.
    Sub-department of Environmental Technology, Wageningen University.
    Henssen, Maurice J.C.
    Bioclear BV.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Quantifying microorganisms during biooxidation of arsenite and bioleaching of zinc sulfide2013Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 48, s. 25-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 15. Dwari, Ranjan
    et al.
    Rao, K. Hanumantha
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Fine coal preparation using novel tribo-electrostatic separator2009Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 22, nr 2, s. 119-127Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 16.
    Engström, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Adolfsson, Daniel
    SSAB EMEA, Luleå.
    Samuelsson, Caisa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    A study of the solubility of pure slag minerals2013Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 41, s. 46-52Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 17. Fredriksson, Andreas
    et al.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    An in situ ATR-FTIR investigation of adsorption and orientation of heptyl xanthate at the lead sulphide/aqueous solution interface2008Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 21, nr 12-14, s. 1000-1004Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 18. Fredriksson, Andreas
    et al.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forsling, Willis
    Kinetics of collector adsorption on mineral surfaces2006Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 19, nr 6-8, s. 784-789Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 19. Gahan, Chandra Sekhar
    et al.
    Sundkvist, Jan-Eric
    Boliden Mineral AB.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Use of mesalime and electric arc furnace (EAF) dust as neutralising agents in biooxidation and their effects on gold recovery in subsequent cyanidation2010Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 23, nr 9, s. 731-738Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 20.
    Gibson, B.
    et al.
    University of Liberia, Monrovia, Liberia.
    Wonyen, D. G.
    University of Liberia, Monrovia, Liberia.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, USA.
    A review of pretreatment of diasporic bauxite ores by flotation separation2017Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 114, s. 64-73Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 21.
    Guntoro, Pratama Istiadi
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Tiu, Glacialle
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ghorbani, Yousef
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Lund, Cecilia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Rosenkranz, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Application of machine learning techniques in mineral phase segmentation for X-ray microcomputed tomography (µCT) data2019Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 142, artikkel-id 105882Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 22.
    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 grinding2003Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 16, nr 1, s. 13-19Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 23.
    Hamberg, Roger
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bark, Glenn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Maurice, Christian
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Alakangas, Lena
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Release of arsenic from cyanidation tailings2016Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 93, s. 57-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 24.
    Hamberg, Roger
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Maurice, Christian
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Alakangas, Lena
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lowering the water saturation level in cemented paste backfill mixtures: Effect on the release of arsenic2017Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 112, s. 84-91Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 25.
    Hamberg, Roger
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Maurice, Christian
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Alakangas, Lena
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    The use of low binder proportions in cemented paste backfill: Effects on As-leaching2015Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 78, s. 74-82Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 26. Hosseini, S. H.
    et al.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Physicochemical studies of smithsonite flotation using mixed anionic/cationic collector2007Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 20, nr 6, s. 621-624Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 27.
    Ikumapayi, Fatai
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mäkitalo, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Johansson, Björn
    Boliden Mineral AB.
    Kota, Hanumantha Rao
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Recycling of process water in sulphide flotation: effect of calcium and sulphate ions on flotation of galena2012Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 39, s. 77-88Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 28.
    Jirestig, Jan A.
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Dispersion of flotation concentrates before magnetic separation1994Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 7, nr 12, s. 1505-1516Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 29.
    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 mills2019Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 130, s. 76-84Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 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.
    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 mills2012Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 33, nr S1, s. 2-12Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 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, 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 mills2014Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 63, s. 65-72Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 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 mills2015Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 73, s. 77-84Artikkel i tidsskrift (Fagfellevurdert)
    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.
    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 mill2011Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 24, nr 3-4, s. 236-244Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 34.
    Khoshkhoo, Mohammad
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Dopson, Mark
    Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University.
    Engström, Fredrik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    New insights into the influence of redox potential on chalcopyrite leaching behaviour2017Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 100, s. 9-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chalcopyrite (CuFeS2) is the most economically important and most refractory copper mineral when treated in conventional sulphate media leaching systems. In this study, the effect of solution redox potential on leaching of a pure and a pyritic chalcopyrite concentrate was investigated using concentrates with fresh and aged surfaces. In experiments using concentrates with fresh surfaces, the response to redox potential depended on the presence of pyrite: fresh pyritic concentrate leached more effectively at low redox potential (in agreement with reductive leaching mechanisms), while the leaching efficiencies from fresh pure concentrate were similar at high and low redox potentials. The data suggested that the reductive leaching mechanism does not necessarily result in higher and faster recoveries in the absence of the galvanic interaction induced by the presence of pyrite. It was also found that exposure of chalcopyrite to atmospheric oxidation prior to leaching (ageing) had an effect on leaching behaviour in response to redox potential: copper recoveries in leaching of aged concentrates were higher at high redox potentials. This behaviour was attributed to the presence of iron–oxyhydroxides on the surface of aged concentrates. Based on the data from this investigation and previous surface studies, it is proposed that iron–oxyhydroxides play an important role in triggering the hindered dissolution of chalcopyrite.

  • 35.
    Koch, Pierre-Henri
    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.
    Rosenkranz, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Automated drill core mineralogical characterization method for texture classification and modal mineralogy estimation for geometallurgy2019Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 136, s. 99-109Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In geometallurgy, a process model operating at the mineral liberation level needs quantitative textural information about the ore. The utilization of this information within process modeling and simulation will increase the quality of the predictions.

    In this study, descriptors derived from color images and machine learning algorithms are used to group drill core intervals into textural classes and estimate mineral maps by automatic pixel classification. Different descriptors and classifiers are compared, based on their accuracy and capacity to be automated. Integration of the classifier approach with mineral processing simulation is also demonstrated. The quantification of textural information for mineral processing simulation introduced new tools towards an integrated information flow from the drill cores to a geometallurgical model.

    The approach has been verified by comparing traditional geological texture classification against the one obtained from automatic methods. The tested drill cores are sampled from a porphyry copper deposit located in Northern Sweden.

  • 36.
    Koleini, S.M. Javad
    et al.
    Department of Mineral Processing, Faculty of Engineering, Tarbiat Modares University, Tehran.
    Aghazadeh, Valeh
    Department of Mineral Processing, Faculty of Engineering, Tarbiat Modares University, Tehran.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Acidic sulphate leaching of chalcopyrite concentrates in presence of pyrite2011Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 24, nr 5, s. 381-386Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Copper concentrates with mineralogy dominated by chalcopyrite have slow leaching kinetics at atmospheric pressure in sulphate media because of the formation of passivation layer on its surface during the leaching. To enhance the leaching rate of the copper concentrate, pyrite was added to act as a catalyst. Pyrite and copper sulphide minerals then form a galvanic cell which increases both the copper leaching rate and yield. Effect of parameters such as solution redox potential, temperature, initial acid concentration, solids content, total initial iron concentration and pyrite to copper sulphide minerals mass ratio were investigated. Mineralogical analyses by XRD were performed on selected leach residues and the feed materials. A copper recovery higher than 80% in 24 h was achieved at a redox potential of 410 mV vs Ag, AgCl, a temperature of 85 °C, 15 g/L of initial acid concentration, a solid content of 7.8% (w/v), a total initial iron concentration 5 g/L and pyrite to copper sulphide minerals mass ratio 2:1. XRD patterns on leach residues showed that candidates for surface passivation, i.e. jarosite and elemental sulphur, were formed at high total initial iron concentrations

  • 37.
    Kvarnström, Björn
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Oghazi, Pejman
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Methods for traceability in continuous processes: experience from an iron ore refinement process2008Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 21, nr 10, s. 720-730Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Every production process is exposed to disturbances leading to production of defective products. The disturbances are seldom immediately discovered, and need to be traced afterwards. Traceability, or the ability to follow a product through the process, is therefore vital since it aids the localisation of the source of the disturbance. Traceability has for a long time been a possibility in part production, but in the continuous process industry it is still problematic. Examples of problems are complex flows, closed systems and large buffers. Hence, the purpose of this paper is to describe methods that can be used to achieve traceability in continuous processes, and give an example of when they may be applied. To identify suitable traceability methods, the literature search was conducted as well as discussions with researchers from the process industry. How the methods work is presented together with their advantages and disadvantages. Furthermore, an example of which traceability methods could be used for achieving traceability in a continuous iron ore refinement process is given. Seeing the diversity of available methods, achieving traceability in continuous processes should be possible.

  • 38.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gustafsson, Gustaf
    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.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental and numerical study of potassium chloride flow using smoothed particle hydrodynamics2018Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 116, s. 88-100Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Materials in granular form are widely used in industry and in the society as a whole. Granular materials can have various behaviours and properties. An accurate prediction of their flow behaviour is important to avoid handling and transportation issues. In this study, the flow behaviour of dry potassium chloride (KCl) in granular form was investigated experimentally and simulated numerically. The aim was to develop numerical tools to predict the flow of KCl in transportation and handling systems and granular material flow in various industrial applications. Two experimental setups were used to quantify the flow of KCl. In the first setup, the collapse of an axisymmetric granular column was investigated. In the second setup, digital image correlation was used to obtain velocity field measurements of KCl during the discharge of a flat-bottomed silo. The two experiments were represented numerically using two-dimensional computational domains. The smoothed particle hydrodynamics method was used for the simulations, and a pressure-dependent, elastic-plastic constitutive model was used to describe the granular materials. The numerical results were compared to the experimental observations, and an adequate qualitative and quantitative agreement was found for the granular column collapse and the silo discharge. Overall, the simulated flow patterns showed adequate agreement with the experimental results obtained in this study and with the observations reported in the literature. The experimental measurements, in combination with the numerical simulations, presented in this study adds to the knowledge of granular material flow prediction. The results of this study highlights the potential of numerical simulation as a powerful tool to increase the knowledge of granular material handling operations.

  • 39.
    Lehner, Theo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Plenary lecture on the wise production and use of metals2007Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 20, nr 9, s. 822-829Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The modern art of metal production engages a broad range of disciplines and knowledge: metallurgy and technology, environment, health and safety, economics and juris prudence, personnel and politicians, in short, a good example of modern industrial management. A historical perspective will be used to outline the author's vision. Boliden operates two smelters in Sweden as part of its integrated mining, smelting, refining and recycling business. Boliden's history includes births, learning, first love, tough decisions, and a recent marriage! The learning curve for the Rönnskär smelter just passed its 75th birthday. It well illustrates the everlasting efforts of our industries to stay on-line with the global industrial learning curve. As part of the society we live and operate in, we fulfil the task of a supplier of metals that man needs. As corporate citizens we also dare to express our concerns if things go wrong, be it in politics or in environmental matters. As the employer of choice we have to create a living organization attracting young operators and engineers as well. As a producer we have to act for the responsible use and recycling of our products. As wisdom comes of age but is about the future, challenges to be turned into opportunities will be forwarded - and hopefully discussed.

  • 40.
    Leistner, T.
    et al.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    Embrechts, M.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany; TU Bergakademie Freiberg, Freiberg, Germany.
    Leißner, T.
    TU Bergakademie Freiberg, Freiberg, Germany.
    Chelgani, Saeed Chehreh
    University of Michigan, Ann Arbor, Michigan, USA.
    Osbahr, I.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    Möckel, R.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    Peuker, U. A.
    TU Bergakademie Freiberg, Freiberg, Germany.
    Rudolph, M.
    Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
    A study of the reprocessing of fine and ultrafine cassiterite from gravity tailing residues by using various flotation techniques2016Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 96-97, s. 94-98Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigates the reprocessing of once disposed tin tailings from a historic German tin operation through different surface properties based processing techniques. Froth flotation and agglomeration flotation, by using commercially available cassiterite collectors from Clariant, were chosen as processing techniques. Isooctane as a nonpolar oil was used to promote the collection of ultrafine (−10 μm) cassiterite by selective agglomeration, and thus, size enlargement. Results indicate that by using sulfosuccinamates as a collector, around 80% of the fine (−50 μm) to very fine (−20 μm) cassiterite can be recovered (representing ∼50% of the total cassiterite in the tailings sample). Agglomeration flotation experiments showed inferior results for recovering the ultrafine cassiterite (for feed fractions in the −25 μm size range). Oil/froth interaction and increased pulp ion content are considered as the main contributing causes.

  • 41.
    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.
    Ghorbani, Yousef
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Evaluation and comparison of different machine-learning methods to integrate sparse process data into a spatial model in geometallurgy2019Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 134, s. 156-165Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A spatial model for process properties allows for improvedproduction planning in mining by considering the process variability ofthe deposit. Hitherto, machine-learning modelling methods have beenunderutilised for spatial modelling in geometallurgy. The goal of thisproject is to find an efficient way to integrate process properties (ironrecovery and mass pull of the Davis tube, iron recovery and mass pull ofthe wet low intensity magnetic separation, liberation of iron oxides, andP_80) for an iron ore case study into a spatial model using machinelearningmethods. The modelling was done in two steps. First, the processproperties were deployed into a geological database by building nonspatialprocess models. Second, the process properties estimated in thegeological database were extracted together with only their coordinates(x, y, z) and iron grades and spatial process models were built.Modelling methods were evaluated and compared in terms of relativestandard deviation (RSD). The lower RSD for decision tree methodssuggests that those methods may be preferential when modelling non-linearprocess properties.

  • 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 patterns2019Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 131, s. 325-335Artikkel i tidsskrift (Fagfellevurdert)
    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.
    Lu, Xianjun
    et al.
    Luleå tekniska universitet.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Flotation selectivity and upgrading of Woxna fine graphite concentrate: Technical note2001Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 14, nr 11, s. 1541-1543Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The present paper describes the effect of srubbing on the flotation selectivity of Woxna fine graphite concentrate and the upgrading process of the material. Results show that scrubbing in an attrition machine (with screened sand of −2.9+0.425 mm as attrition media) is an effective way to improve the flotation selectivity, and the material can be upgraded to over 94% from the feed grade of 87–88% carbon by an upgrading process consisting of scrubbing and two-step cleaning flotation.

  • 44.
    Lu, X.J.
    et al.
    Luleå tekniska universitet.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Preparation of high-purity and low-sulphur graphite from Woxna fine graphite concentrate by alkali roasting2002Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 15, nr 10, s. 755-757Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An alkali roasting process, which consists of roasting with caustic soda, water washing and sulphuric acid leaching, has been found to be an effective method for graphite purification even at low roasting temperature. With this process, a flotation fine concentrate containing 87-88% carbon could be purified to about 99.4% carbon when roasted with 25% NaOH at 250 deg C and leached by 10% H sub 2 SO sub 4 solution at room temperature. In addition to the successful removal of silicate impurities, the process was also found to be effective to eliminate sulphide impurities. For instance, the sulphur content in the end product could be reduced to below 0.05% from 0.6% by the process. Furthermore, the consumption of NaOH can be lowered by using high-grade feed. When using a feed of 95.9% carbon (upgraded by flotation), the NaOH concentration could be reduced to 10% from 25% while the product purity could reach the same purity level of over 99%.

  • 45.
    Lund, Cecilia
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Lamberg, Pertti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Lindberg, Therese
    LKAB, Research & Development, 983 81 Malmberget.
    Development of a geometallurgical framework to quantify mineral textures for process prediction2015Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 82, s. 61-77Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A geometallurgical framework was developed in three steps using the Malmberget iron ore deposit, northern Sweden, as a case study. It is based on a mineralogical-particle approach which means that the mineralogical information is the main focus. Firstly, the geological model describes quantitatively the variation in modal composition and mineral textures within the ore body. Traditional geological textural descriptions are qualitative and therefore a quantitative method that distinguishes different mineral textures that can be categorised into textural archetypes was developed.The second step of the geometallurgical framework is a particle breakage model which forecasts how ore will break in comminution and which kind of particles will be generated. A simple algorithm was developed to estimate the liberation distribution for the progenies of each textural archetype. The model enables numerical prediction of the liberation spectrum as modal mineralogy varies. The third step includes a process model describing quantitatively how particles with varying particle size and composition behave in each unit process stage. As a whole the geometallurgical framework considers the geological model in terms of modal composition and textural type. The particle breakage model forecasts the liberation distribution of the corresponding feed to the concentration process and the process model returns the metallurgical response in terms of product quality (grade) and efficacy (recovery).

  • 46.
    Lund, Cecilia
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lamberg, Pertti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Lindberg, Therese
    LKAB, Research & Development, 983 81 Malmberget.
    Practical way to quantify minerals from chemical assays at Malmberget iron ore operations: an important tool for the geometallurgical program2013Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 49, s. 7-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This is the first step in establishing a geometallurgical program for the Malmberget iron ore deposit, northern Sweden. Geometallurgy captures geological and metallurgical (processing) information into a spatially-based predictive model of mineral processing characteristics. This paper describes the development of a practical, fast and inexpensive technique to quantify minerals from routine chemical assays. Ore samples and process samples from two different orebodies were used in the process of developing this element to mineral conversion technique that involved electron microprobe (EPMA), X-ray fluorescence (XRF) and SATMAGAN analyses. The method was validated against QEMSCAN analyses. From the calculated modal mineralogy an ore classification system was established based on the iron mineralogy, iron mineral grades and gangue mineralogy to create a preliminary geological/geometallurgical model of the ore. However, in a geometallurgical context the modal composition is not sufficient and the geological model requires information on mineral textures, too.

  • 47.
    Malm, Lisa
    et al.
    Boliden Mineral, Department of Process Technology.
    Kindstedt Danielsson, Ann-Sofi
    RISE – Research Institutes of Sweden AB, Surface, Process and Pharmaceutical Development.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Rosenkranz, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Ymén, Ingvar
    RISE – Research Institutes of Sweden AB, Surface, Process and Pharmaceutical Development.
    Application of Dynamic Vapor Sorption for evaluation of hydrophobicity in industrial-scale froth flotation2018Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 127, s. 305-311Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

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

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

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

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

  • 48.
    Minz, Friederike
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bohlin, Nils-Johan
    Boliden, Division of Process Technology.
    Lamberg, Pertti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Wanhainen, Christina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Detailed characterisation of antimony mineralogy in a geometallurgical context at the Rockliden ore deposit, North-Central Sweden2013Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 52, s. 95-103Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The antimony (Sb) content of the Rockliden complex Zn–Cu massive sulphide ore lowers the quality of the Cu–Pb concentrate. The purpose of this study is to characterise the Sb mineralogy of the deposit. The Sb-bearing minerals include tetrahedrite (Cu,Fe,Ag,Zn)12Sb4S13, bournonite PbCuSbS3, gudmundite FeSbS and other sulphosalts. On a microscopic scale these minerals are complexly intergrown with base-metal sulphides in the ore. Based on these observations mineralogical controls on the distribution of Sb-bearing minerals in a standard flotation test are illustrated. Deposit-scale and rock-related variation in the Sb-content and distribution of Sb-bearing minerals were found. This underlines the importance in understanding the geological background as a basis of a 3D geometallurgical model for Rockliden. Such a model is expected to predict the Sb content of the Cu–Pb concentrate, among other process-relevant factors, and helps to forecast when the Cu–Pb concentrate has to be treated by alternative processes, such as alkaline sulphide leaching, before it is sold to the smelter.

  • 49.
    Minz, Friederike
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bolin, Nils-Johan
    Boliden Mineral AB, Luleå tekniska universitet.
    Lamberg, Pertti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Bachmann, Kai
    TU Bergakademie Freiberg, Helmholtz Zentrum Dresden-Rossendorf, Helmholtz-Institute-Freiberg for Resource Technology.
    Gutzmer, Jens
    TU Bergakademie Freiberg, Helmholtz Zentrum Dresden-Rossendorf, Helmholtz-Institute-Freiberg for Resource Technology.
    Wanhainen, Christina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Distribution of Sb minerals in the Cu and Zn flotation of Rockliden massive sulphide ore in north-central Sweden2015Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 82, s. 125-135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Rockliden massive sulphide Zn–Cu deposit contains minor amounts of Sb minerals. The Sb mineralogy is complex in terms of composition, micro textures and mineral associations. The main Sb minerals comprise tetrahedrite, bournonite, gudmundite and Sb–Pb sulphides such as meneghinite. The presence of these minerals is especially critical to the quality of the Cu–Pb concentrate. To study how they are distributed in a simplified flotation circuit and what controls their process behaviour Sb-rich drill core samples were selected from the Rockliden deposit and a standard laboratory flotation test was run on the composite samples. Scanning electron microscope-based automated mineralogy was used to measure the Sb mineralogy of the test products, and the particle tracking technique was applied to mass balance the different liberation classes to finally trace the distribution of liberated and locked Sb minerals. The mineralogical factors controlling the distribution of Sb minerals are mineral grain size, the degree of liberation, and associated minerals. Similarities in the distribution of specific particle types from the tested composites point towards systematics in the behaviour of particles and predictability of their distribution which is suggested to be used in a geometallurgical model of the deposit.

  • 50.
    Mwanga, Abdul
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Lamberg, Pertti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Rosenkranz, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Comminution test method using small drill core samples2015Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 72, s. 129-139Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Comminution tests aim to measure the comminution properties of ore samples to be used in designing and sizing the grinding circuit and to study the variation within an ore body. In the geometallurgy context this information is essential for creating a proper resource model for production planning and management and process control of the resource’s exploitation before and during production.Standard grindability tests require at least 10 kg of ore sample, which is quite a lot at early project stages. This paper deals with the development of a method for mapping the variability of comminution properties with very small sample amounts. The method uses a lab-scale jaw crusher, standard laboratory sieves and a small laboratory tumbling mill equipped with a gross energy measurement device. The method was evaluated against rock mechanics tests and standard Bond grindability test. Within this approach textural information from drill cores is used as a sample classification criterion.Experimental results show that a sample of approximate 220 g already provides relevant information about the grindability behavior of iron ores at 19% mill fillings and 91% fraction of the critical mill speed. The gross energy measured is then used to calculate an equivalent grinding energy. This equivalent energy is further used for predicting the variations in throughput for a given deposit and process.Liberation properties of the ore connected to grindability elaborates energy required for grinding and significances of it when deciding to move to higher grinding energy considering the improvement of liberation of the desired mineral. However, high energy significantly enhanced the degree of liberation of magnetite and is expected to improve the concentrate grade after downstream treatment. The higher the magnetite content the better is the liberability of magnetite and the lower the energy required to liberate the desired mineral. Liberability of magnetite is also affected by texture classes containing low magnetite content. A methodology that combines this information has been developed as a practical framework of geometallurgical modeling and simulation in order to manage technical and economic exploitation of resource at early, project stages and during mining operations.

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