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  • 51.
    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.

  • 52.
    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.

  • 53.
    Mwanga, Abdul
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Parian, Mehdi
    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 modeling using mineralogical properties of iron ores2017Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 111, s. 182-197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Comminution modeling aims to predict the size and liberation distribution of mineral particles and the required comminution energy. The current state-of-the-art comminution models provide a calculation of neither particle size distribution, grinding energy and throughput dependency with neither a broad understanding of how the mineral grade varies by size nor the liberation distribution of the product. The underlying breakage mechanisms affect the liberation of mineral grains and are dependent on modal mineralogy and mineral texture (micro structure). It has also been a challenge to model comminution systems to predict the optimal energy and size for better mineral liberation because of the variability of the mineral particle properties i.e. grains arrangement and composition. A detailed mineralogical study was carried out in order to broaden the understanding of the nature and distribution of comminuted particles in a ball mill product. Focusing on iron ore samples the study showed how the particle breakage rate decreases when the particles reach the grain size of the main mineral component. Below that size, comminution does not increase mineral liberation and therefore in most of the cases passing over that boundary is only a waste of energy. The study involving iron ores from Malmberget and Kiruna, Northern Sweden, showed that certain shortcuts can be applied to empirically model the mineral liberation distribution of the particles in a ball mill based on the mineral grade-by-size pattern from a geometallurgical program. In Malmberget and Kiruna the mineral grade-by-size pattern is depending on the mineral distribution and grain size of gangue as well as magnetite or hematite minerals. A significant difference between mineral breakage of the same grade and gangue minerals can be observed due to texture differences.

  • 54.
    Mwanga, Abdul
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Rosenkranz, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Lamberg, Pertti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Development and experimental validation of the Geometallurgical Comminution Test (GCT)2017Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 108, s. 109-114Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Based on the requirements and available sample amounts in geometallurgical studies of ore variability, a small scale batch grindability test has been developed, the Geometallurgical Comminution Test (GCT). The test requires 220 g of sample material and can be conducted within 2.5–3 h. Test results are evaluated using a modified Bond equation together with a linear correlation factor. The test and evaluation method have been validated against several ore types.

  • 55.
    Nellros, Frida
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Thurley, Matthew
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Automated image analysis of iron-ore pellet structure using optical microscopy2011Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 24, nr 14, s. 1525-1531Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Knowledge about pellet microstructure such as porosity and oxidation degree is essential in improving the pellet macro-behavior such as structural integrity and reduction properties. Manual optical microscopy is commonly used to find such information but is both highly time consuming and operator dependent. This paper presents research to automate image capture and analysis of entire cross-sections of baked iron ore pellets to characterize proportions of magnetite, hematite, and other components.The presented results cover: semi-automated image acquisition of entire pellets, separation of pellet and epoxy and calculation of total percentages of magnetite, hematite and pores. Using the Leica Qwin microscope software and a segmentation method based on Otsu thresholding these three objectives have been achieved with the phases labeled as magnetite, hematite and pores and additives. Furthermore, spatial distributions of magnetite, hematite and pores and additives are produced for each pellet, graphing proportions in relation to the distance to the pellet surface. The results are not directly comparable to a chemical analysis but comparisons with manual segmentation of images validates the method. Different types of pellets have been tested and the system has produced robust results for varying cases.

  • 56.
    Nilsson, Leif K.
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Solubility of radionuclide species from uranium mill tailings1988Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 1, nr 4, s. 295-310Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Present report describes solubility of different radionuclides, especially Ra-226, from uranium mill tailings. The solubility in water has been studied in both column and shake flask leaching tests. The test material used came from a uranium deposit at Lilljuthatten in the Swedish province of Jamtland. -The results of the study show that neutralization sludge and/or fine particles have an adsorbing capacity on Ra-226. Furthermore, by adding barium sulphate to the tailings pile a substantial decrease of Ra-226 in the water could be observed.

  • 57.
    Nooshabadi, Alireza Javadi
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Larsson, Anna-Carin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kota, Hanumantha Rao
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Formation of hydrogen peroxide by pyrite and its influence on flotation2013Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 49, s. 128-134Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by pyrite (FeS2), the most abundant metal sulphide on Earth, during grinding was investigated. It was found that pyrite generated H2O2 in pulp liquid during wet grinding and also the solids when placed in water immediately after dry grinding. Type of grinding medium on formation of hydrogen peroxide revealed that the mild steel produced more H2O2 than stainless steel grinding medium, where Fe2+ and/or Fe3+ ions played a key role in producing higher amounts of H2O2. The effect of grinding atmosphere of air and N2 gas showed that nitrogen environment free from oxygen generated more H2O2 than air atmosphere suggesting that the oxygen in hydrogen peroxide is derived from water molecules. In addition, the solids after dry grinding producing more H2O2 than wet grinding indicate the role of pyrite surface or its catalytic activity in producing H2O2 from water. This study highlights the necessity of relooking into the electrochemical and/or galvanic interaction mechanisms between the grinding medium and pyrite in terms of its flotation behaviour.

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

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

  • 59.
    Parian, Mehdi
    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.
    Möckel, Robert
    Helmholtz-Zentrum Dresden – Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Halsbruecker Straße 34, 09599 Freiberg.
    Rosenkranz, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Analysis of mineral grades for geometallurgy: Combined element-to-mineral conversion and quantitative X-ray diffraction2015Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 82, s. 25-35Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Knowledge of the grade of valuable elements and its variation is not sufficient for geometallurgy. Minerals define not only the value of the deposit, but also the method of extraction and concentration. A number of methods for obtaining mineral grades were evaluated with a focus on geometallurgical applicability, precision and trueness. For a geometallurgical program, the number of samples to be analyzed is large, therefore a method for obtaining mineral grades needs to be cost-efficient, relatively fast, and reliable. Automated mineralogy based on scanning electron microscopy is generally regarded as the most reliable method for analyzing mineral grades. However, the method is time demanding and expensive. Quantitative X-ray diffraction has a relatively high detection limit, 0.5%, while the method is not suitable for some base and precious metal ores, it still provides significant details on gangue mineral grades. The application of the element-to-mineral conversion has been limited to the simple mineralogy because the number of elements analyzed limits the number of calculable mineral grades. This study investigates a new method for the estimation of mineral grades applicable for geometallurgy by combining both the element-to-mineral conversion method and quantitative X-ray diffraction with Rietveld refinement. The proposed method not only delivers the required turnover for geometallurgy, but also overcomes the shortcomings if quantitative X-ray diffraction or element-to-mineral is used alone

  • 60.
    Potapova, Elisaveta
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Yang, Xiaofang
    Westerstrand, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Interfacial properties of natural magnetite particles compared with their synthetic analogue2012Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 36-38, nr S1, s. 187-194Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Understanding of the interactions between iron oxides and flotation reagents is important both for flotation and agglomeration of iron ore. Model systems comprising synthetic iron oxides and pure chemical reagents are commonly applied in experimental work in order to obtain high quality data and to ease the interpretation of the empirical data. Whether the results obtained using model systems are valid for iron ore minerals and commercial reagents is a question seldom addressed in the literature. It is shown in this work that previously reported results obtained from a model system, concerning adsorption of a carboxylate surfactant and sodium metasilicate onto synthetic magnetite nanoparticles, as obtained by in situ ATR-FTIR spectroscopy and contact angle measurements, are applicable to adsorption of flotation reagents on magnetite concentrate. Additionally, the problem of restoring magnetite wetting after flotation is addressed since good wetting of a magnetite concentrate is required to produce iron ore pellets by wet agglomeration. The results from the present work indicate that the wettability of both synthetic magnetite coated with surfactant and magnetite concentrate after flotation can be improved by adsorbing a hydrophilizing agent such as silicate or polyacrylate.

  • 61.
    Prabhakar, S
    et al.
    National Metallurgical Laboratory Madras Centre, Taramani, Chennai.
    Rao, Hanumantha
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forsling, Willis
    Dissolution of wollastonite and its flotation and surface interactions with tallow-1,3-diaminopropane (duomeen T)2005Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 18, nr 7, s. 691-700Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wollastonite finds an important place among industrial minerals due to its high chemical and thermal resistance and also as a substitute for asbestos. With the depletion of high-grade ores and increased demand, it becomes inevitable to process low-grade ores. Flotation can be employed effectively for processing these ores. Flotation behavior of wollastonite was studied using tallow-1,3-diaminopropane as collector in the Hallimond micro-flotation cell. The flotation recoveries obtained were correlated with contact angle measurements. Dissolution studies clearly bring out the incongruent dissolution of wollastonite, resulting in a silica rich layer on the surface of the mineral. The release rates of calcium and silicon decrease with the particle size. Maximum flotation obtained at 1 x 10[-][5] M diamine concentration. DRIFT studies indicate that the intensity of alkyl chain bands increases with increasing diamine concentration, thus corroborating increased presence of diamine on wollastonite resulting in maximum contact angle and flotation recovery. Surface free energy values of wollastonite were determined by different approaches using contact angle data of well-defined components of polar and apolar liquids. An attempt has been made to correlate between the flotation response and the surface free energy values of wollastonite in the presence diamine.

  • 62.
    Pålsson, Bertil
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Persson, H.
    Luleå tekniska universitet.
    Redox control in a pilot flotation column1996Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 9, nr 1, s. 73-83Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results from pilot-column flotation tests on a lead-zinc ore show that it is possible to control the redox potential of the column pulp by varying the oxygen activity of the flotation gas fed to the spargers. As a result, the process changes so that the fine zinc minerals are more actively floating in an oxidising environment, at the same time xanthate and frother consumptions increase.The placement of electrodes in the column does change the redox potential readings but only as a result of a change in the oxygen concentration of the pulp. However, the values from a Glassy-Carbon (GC) electrode are consistently lower than those from a Pt foil electrode at the same location. Actual positions of operating points as measured by GCelectrodes fall within the theoretical area for precipitation of lead xanthate.

  • 63.
    Rao, K. Hanumantha
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forssberg, Eric
    Mechanism of fatty acid adsorption in salt-type mineral flotation1991Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 4, nr 7, s. 879-890Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Our recent studies on the interaction of oleate with salt-type mineral surfaces have been summarized based on adsorption, infrared and zeta-potential measurements. Monolayer coverage in the case of calcite and a bilayer formation in the cases of fluorite, apatite and scheelite, preceding the precipitation of calcium soap has been suggested for the adsorption mechanism of oleate on these minerals. The monolayer coverage is shown to correspond to a condensed state of oleate with a molecular coverage area of 33 A2 (liquid-crystal state). Depending on the surface potential and its magnitude at basic pH values, oleate is either chemisorbed on the surface calcium or monocoordinated through counter sodium and calcium ions for the monolayer filling.

  • 64.
    Rincon, Jonathan
    et al.
    University of Liege, GeMMe – Minerals Engineering and Recycling, Sart-Tilman Campus-B52, Liège, Belgium.
    Gaydardzhiev, Stoyan
    University of Liege, GeMMe – Minerals Engineering and Recycling, Sart-Tilman Campus-B52, Liège, Belgium.
    Stamenov, Lachezar
    Dundee Precious Metals Chelopech, Village of Chelopech, Bulgaria.
    Coupling comminution indices and mineralogical features as an approach to a geometallurgical characterization of a copper ore2019Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 130, s. 57-66Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A production block of the underground mine exploiting the Chelopech high sulphidation epithermal copper-gold deposit was subjected to geometallurgical modelling. This study details the procedure used based on traditional comminution and mineralogical indices. Drop weight and batch grinding tests were performed on representative samples to yield parameters related to Axb and operating work OWi indices. These were further correlated with the ore mineralogical features using principal component analysis. Modal mineralogy data processed by a set of linear equations enabled the estimation of the aforementioned indices with a deviation of ±2.4 for Axb and ±9.08 kWh/t for OWi respectively. Based on ore textural characteristics and non-sulphide gangue (NSG) minerals content, two geometallurgical domains were identified as a first approach to modelling of the studied block.

  • 65.
    Rincon, Jonathan
    et al.
    University of Liege, GeMMe – Minerals Engineering and Recycling, Sart-Tilman Campus-B52, Liège, 4000, Belgium.
    Gaydardzhiev, Stoyan
    University of Liege, GeMMe – Minerals Engineering and Recycling, Sart-Tilman Campus-B52, Liège, 4000, Belgium.
    Stamenov, Lachezar
    Dundee Precious Metals Chelopech, Village of Chelopech, 2087, Bulgaria.
    Investigation on the flotation recovery of copper sulphosalts through an integrated mineralogical approach2019Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 130, s. 36-47Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Investigation on the flotation behaviour of enargite (Cu3AsS4) and tennantite ((Cu, Fe)12As4S13) during selective copper flotation was performed using an integrated mineralogical approach. To this end, samples taken from a production block at the Chelopech mine were subjected to a laboratory scale flotation and products characterized through multi-element chemical analyses and mineral mapping using a SEM-based automated mineralogy. Chemistry, modal mineralogy, copper-sulphosalts’ liberation and associations were quantified. Principal component analysis (PCA) was employed to look for relationships between mineralogical features and flotation recovery. High variability in head copper grade was observed in the studied block, with deportment results attributing it to the varied content of enargite and tennantite. Chalcopyrite content was low in the majority of the samples. The close association and the frequently observed interlocking of pyrite and Cu-sulphosalt grains can explain pyrite (and gold) recovery during copper cleaner flotation. Linear equations based on PCA results allow the prediction of Cu-sulphosalts’ recovery with a root mean square error of ±1.32%.

  • 66.
    Sand, Anders
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Toivakka, Martti
    Åbo Akademi University.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    A Stokesian Dynamics Approach for Simulation of Magnetic Particle Suspensions2016Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 90, nr SI , s. 70-76Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 67.
    Sandström, Åke
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Shchukarev, Andrei
    Umeå universitet.
    Paul, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    XPS characterisation of chalcopyrite chemically and bio-leached at high and low potential2005Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 18, nr 5, s. 505-515Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Leaching of chalcopyrite in sulphuric acid media has been investigated under constant redox potential conditions in solution. The leaching residues were analysed by X-ray diffraction and X-ray photoelectron spectroscopy. The leaching was performed at two different levels of redox potential, 420 mV and 600 mV (Pt vs. Ag, AgCl), at 65 °C. Both bioleaching and chemical leaching were investigated. The bioleaching was continuous, with a culture of the extremely thermophilic microorganism Sulfolobus metallicus. The high redox potential experiment was a "normal" bioleaching experiment; i.e., normal air flow, etc., the redox potential obtained at steady state was 600 mV and the low redox condition was achieved by a reduced airflow and additions of a sodium sulphite solution. The chemical leaching was done as a redox titration with potassium permanganate as oxidising agent to maintain the redox potential at 600 mV and 420 mV, respectively. Chalcopyrite leaching was greatly enhanced at the lower redox potential for both types of leaching, but especially during chemical leaching, which also resulted in large amounts of elemental sulphur. Passivation of the leaching at high redox potential was followed by a concomitant precipitation of large amounts of jarosite. Bioleaching resulted in a more complete sulphur oxidation to sulphate, even at low redox potential. It is thus concluded that passivation during chalcopyrite leaching is caused by jarosite and not elemental sulphur.

  • 68.
    Semsari, Parisa
    et al.
    Department of Mining and Metallurgical Eng., Amirkabir University of Technology, Tehran, Iran.
    Irannajad, Mehdi
    Department of Mining and Metallurgical Eng., Amirkabir University of Technology, Tehran, Iran.
    Mehdilo, Akbar
    Department of Mining and Metallurgical Eng., Amirkabir University of Technology, Tehran, Iran.
    Modification of ilmenite surface properties by superficial dissolution method2016Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 92, s. 160-167Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Acid surface dissolution as a pretreatment method converts Fe2+ ions on the ilmenite surface to Fe3+ ions. XPS analysis showed that the content of Fe3+ increases from 48.5% to 59.8% after surface dissolution for 15 min in a solution of sulfuric acid with a concentration of 10%. This conversion, without any phase transformation, decreases the zeta potential of ilmenite in a wide pH range, resulting in a shift in IEP (Iso-Electric Point) from a pH of 5.4 to 2.3. FTIR spectra and zeta potential measurements showed that the increase of oleate ions adsorption on the ilmenite surface, resulting from the surface dissolution process, is insignificant. After surface dissolution, the formation of more ferric iron oleate species (Ksp = 10−29.7) being more stable than ferrous iron oleate (Ksp = 10−15.5) compounds yields an increase of ilmenite hydrophobicity and floatability in a wide pH range. Using 3.65 × 10−4 M sodium oleate at a pH of 6.3, the maximum flotation recoveries are obtained as 73.5% and 92% for non-treated and acid pretreated ilmenite, respectively.

  • 69.
    Seppälä, Pirjo
    et al.
    Control Engineering, University of Oulu.
    Sorsa, Aki
    Control Engineering, University of Oulu.
    Paavola, Marko
    Control Engineering, University of Oulu.
    Ruuska, Jari
    Uleåborg universitet, Control Engineering, University of Oulu.
    Remes, Antti
    Outotec Oyj.
    Kumar, Haresh
    Oulu Mining School, University of Oulu.
    Lamberg, Pertti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Leviskä, Kauko J.
    Uleåborg universitet, Control Engineering, University of Oulu.
    Development and calibration of a dynamic flotation circuit model2016Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 96-97, s. 168-176Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Monitoring of mineral beneficiation processes is difficult due to lack of reliable measurements and hazardous environment. Therefore robust models describing steady-state and dynamic behaviour of the processes are needed when aiming for improved monitoring and control. Specific characteristics of models used in mineral processes are that they require spatial mineralogical information of raw material. In this study, a dynamic simulator combining ore characteristic physical data, process operating parameters and mineralogical properties is developed for the Oulu Mining School (OMS) mini-pilot scale mineral beneficiation plant. The mini-pilot process, theoretical part of the model and the model development are described. Open and closed flotation circuit experiments were carried out in mini-pilot research environment for model identification. Experimental and simulated results of ore type variation and pH change are presented. Based on the results the effects of the aforementioned factors on flotation performance are predicted.

  • 70.
    Sivamohan, Rajaratnam
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Electronic sorting and other preconcentration methods1991Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 4, nr 7, s. 797-814Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The literature involving the practival aspects of electronic sorting in the 70s and 80s is reviewed. The areas covered are radiometric sorting, X-ray sorting, optical sorting, sorting based on electrical conductivity and sorting based on microwave heating.In addition, the capacity of heavy media separation as a preconcentration method for sulphide ores is highlighted.Other methods, such as magnetohydrostatics and eddy-current separation, are also discussed.The article also contains hitherto unpublished experimental results on the preconcentration of various Swedish sulphide ores by various methods of electronic sorting, as well as heavy media separation.

  • 71.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Direct measurement of internal material flow in a bench scale wet Low-Intensity Magnetic Separator2016Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 91, s. 55-65Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 72.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Evaluation of the applicability of ultrasonic velocity profiling in conditions related to wet low intensity magnetic separation2014Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 62, s. 2-8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 73.
    Subrahmanyam, T.V.
    et al.
    CCE/UFRN, Natal.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Froth characteristics and grade-recovery relationships in the flotation of lead-zinc and copper ores1988Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 1, nr 1, s. 41-52Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Froth forms an important phase in flotation upon which the final yield parameters are dependent. Flotation froths are three-phase froths and the solid particles exercise an influence in stabilizing or destabilizing the froths depending on the degree of hydrophobicity, size and concentration of fines. This paper deals with froth characteristics in flotation tests carried out on lead-zinc and copper ores with four different frothers. The results are analysed by grade-recovery relationships.

  • 74.
    Subrahmanyam, T.V.
    et al.
    Departmento de Geologia, CCE/UFRN, Campus Universitario, Natal.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mineral solution-interface chemistry in minerals engineering1993Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 6, nr 5, s. 439-454Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the treatment of sulphide ores, the reactions occurring in several processes like wet grinding, flotation, collectorless flotation, leaching/bioleaching and in adsorption mechanisms, for example the interaction of thiol collectors with oxidation-reduction reactions, play a dominant role. To optimize the conditions for metallurgical yield (grinding, flotation, leaching) or to combat a problem (acid mine drainage) understanding of the mechanisms involved in the process is needed. In broad terms this is mineral/solution interface chemistry. These mechanisms are discussed in this paper with emphasis on galvanic interactions.

  • 75.
    Sun, Zhongxi
    et al.
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Degradation kinetics of ethyl-xanthate as a function of pH in aqueous solution1997Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 10, nr 4, s. 389-400Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Xanthate degradation kinetics plays an important role in sulfide mineral flotation and in the treatment of flotation tailings. Increasing environmental concern about consequences of flotation tailings makes this information even more important. In this paper, the degradation kinetics of xanthate in homogeneous solution as a function of pH at 5 °C, 20 °C and 40 °C is systematically studied by UV-Visible spectrophotometric measurements. The results indicate that the degradation of ethyl xanthate is rapidly increased with decreasing pH at pH<7. At pH 7-8, the maximum half-life of the xanthate appears. The degradation was faster at pH 9-10, but at pHgt;10 the half-lives of xanthate once again increase. The investigations are also extended to different media other than pure water, such as, 0.1 M NaClO4, 0.1 M NaNO3 0.1 M NaCl as well as in the supernatants of flotation tailings of sulfide minerals. The rate constants of xanthate degradation are calculated and presented together with half-lives and activation energies of xanthate degradation. The degradation products and reaction mechanisms are discussed based on experimental results

  • 76.
    Tan, Su Nee
    et al.
    Ian Wark Research Institute, University of South Australia.
    Pugh, R.J.
    Fornasiero, D.
    Ian Wark Research Institute, University of South Australia.
    Sedev, R.
    Ian Wark Research Institute, University of South Australia.
    Ralston, J.
    Ian Wark Research Institute, University of South Australia.
    Foaming of polypropylene glycols and glycol/MIBC mixture2005Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 18, nr 2, s. 179-188Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The surface tension and foamability of a series of polypropylene glycols (PPG) with average molecular weights (MW) ranging from 200 to 2000 g mol-1 and hydrophilic-lipophilic balance (HLB) values ranging from 10.4 to 5.8 were compared to methyl isobutyl carbinol (MIBC), 4-methyl-2-pentanol (MW102 g mol-1 and HLB 6.1). Experiments were carried out using a modified Bikermann column in which the foam heights were determined at a range of gas flow rates and retention times were calculated at different foamer concentrations. These studies show the six-carbon polypropylene glycol (PPG400) with HLB value of 9.7 is an unusually strong frother. Since many industrial foamers/frothers commonly contain a mixture of chemical types, we have also studied the foaming behaviour of mixed systems of PPGs and MIBC at a range of concentrations. The foaming data indicated that a synergistic effect occurred for several of the mixed systems with differences in HLB values, which resulted in an increase in foam height compared to the performance of the individual systems. Dynamic surface tension measurements, determined in the short time span range of 0.1-10 s, correlated with the synergistic effect and it was found that the blended systems gave a higher dynamic surface tension gradient compared to the individual PPGs. It could be suggested that the mixed foamer (containing high HLB and low HLB value components) produce closed packed, molecular cohesive films at the air/solution interface giving greater surface elasticity, which appeared to increase foamability

  • 77.
    Tano, Kent
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sellgren, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    On-line lifter deflection measurements showing flow resistance effects in grinding mills2005Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 18, nr 11, s. 1077-1085Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The deflection that a lifter bar is subjected to when passing through a grinding charge was measured using an embedded strain gauge sensor. The obtained signal profile is analysed and interpreted in relation to charge properties such as toe and charge angle for the grinding charge. The current work has focused on the charge and slurry flow behaviour when solids content is changed and how well the sensor reflects this. Bench scale measurements with a vane type viscometer, roughly evaluated in terms of apparent viscosity is used as a character for the resistance to motion of the slurry. The slurry flow resistance is strongly influenced by solids content and obviously by the addition of a dispersant. The strain gauge sensor reflected this change well, showing that toe and shoulder region of the charge varied in a systematic way. Results obtained also shows that change of slurry flow resistance exert an influence on grinding performance. A multivariate statistical method, partial least squares regression, is applied to the sensor data producing a model that can predict the change in slurry flow resistance. The output from the model also shows good properties to be used as a process-monitoring tool. The predictive capability of the model is believed to be of such quality that it can be used for process control.

  • 78.
    Thurley, Matthew
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Andersson, Tobias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    An industrial 3D vision system for size measurement of iron ore green pellets using morphological image segmentation2008Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 21, nr 5, s. 405-415Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An industrial prototype 3D imaging and analysis system has been developed that measures the pellet sieve size distribution into 9 sieve size classes between 5mm and 16+mm. The system is installed and operational at a pellet production plant capturing and analysing 3D surface data of piled pellets on the conveyor belt. It provides fast, frequent, non-contact, consistent measurement of the pellet sieve size distribution and opens the door to autonomous closed loop control of the pellet balling disk or drum in the future. Segmentation methods based on mathematical morphology are applied to the 3D surface data to identify individual pellets. Determination of the entirely visible pellets is made using a new two feature classification, the advantage being that this system eliminates the resulting bias due to sizing partially visible (overlapped) particles based on their limited visible profile. Literature review highlights that in the area of size measurement of pellets and rocks, no other researchers make this distinction between entirely and partially visible particles. Sizing is performed based on best-fit-rectangle, classified into size classes based on one quarter of the measured sieving samples, and then compared against the remaining sieve samples.

  • 79.
    Tranvik, Elin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. Minerals to Metals Initiative, Department of Chemical Engineering, University of Cape Town, Rondebosch, South Africa.
    Becker, Megan
    Chemical Engineering, University of Cape Town, South Africa.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Franzidis, Jean-Paul
    Chemical Engineering, University of Cape Town, South Africa.
    Bradshaw, Dee J.
    Chemical Engineering, University of Cape Town, South Africa.
    Towards cleaner production: Using flotation to recover monazite from a heavy mineral sands zircon waste stream2017Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 101, s. 30-39Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In line with the principles of cleaner production, the removal of monazite via reverse flotation was investigated with a view to reducing the radioactivity of a heavy mineral sands waste stream. Another benefit was to create a potential REE by-product from the Namakwa Sands operation in South Africa. Understanding the mineralogy of the zircon waste stream was essential owing to the cemented nature of the deposit and the potential impact of surface coatings on the flotation performance. SEM, QEMSCAN and optical microscopy showed that amorphous SiO2 was the most abundant surface coating associated with both monazite and zircon, which is likely to constitute a major challenge in achieving flotation selectivity. A D-optimal statistical screening design was applied to find the most relevant flotation parameters and a full factorial design to find the optimal flotation conditions. The most promising results showed that monazite could be successfully removed from the zircon waste with an oleate collector at pH 10. The selectivity was found to be highly dependent on pH, with no selectivity at pH 9 and no mineral flotation at pH 11. Further work is recommended to confirm and optimise these conditions and test them on a larger scale.

  • 80.
    Wang, X-H
    et al.
    Department of Mining Engineering and Center for Applied Energy Research, University of Kentucky, Lexington.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    The solution electrochemistry of sulfide-xanthate-cyanide systems in sulfide mineral flotation1996Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 9, nr 5, s. 527-546Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Extensive thermodynamic calculations have been performed for a number of flotation systems of metal sulfide minerals using cyanide as a depressant to investigate the physicochemical principles underlying the effective depression processes. It has been shown that selective depression of the flotation of sulfide minerals by cyanide is achieved through the one or more of the following processes: (A) cyanide dissolves the metal xanthates to form metal-cyanide complexes or combines with surface metal ions to prevent the formation of metal-xanthates; (B) cyanide reduces the redox potential of the flotation pulp and consumes oxygen in the flotation pulp to prevent the chemisorption and oxidation of xanthate; (C) cyanide is preferentially adsorbed on the sulphide mineral surfaces as cyanometal complexes to inhibit the adsorption of xanthate and the oxidation of xanthate on mineral surface; (D) cyanide reacts with elemental sulfur and polysulfides to form thiocyanate, thereby removing the surface hydrophobic entity. Electrochemical studies on the pyrite electrode have confirmed the above solution chemistry calculations. It has been found that in cyanide solutions, the surface oxidation of pyrite is greatly enhanced. The initial oxidation step involves the electrochemical adsorption of cyanide on pyrite. This inhibits the adsorption of xanthate on the pyrite surface and minimizes the flotation of pyrite. Furthermore, xanthate adsorbed on pyrite surfaces is readily replaced by cyanide when cyanide is added into the pyrite flotation system.

  • 81. Wang, Yanmin
    et al.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Aggregation between magnetite and hematite ultrafines utilizing remanent magnetization1992Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 5, nr 8, s. 895-905Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is indicated that hematite ultrafines (<10 μm) in a well-dispersed surry are selectively aggregated with magnetite ultrafines in the absence of aggregating agents, high shear rates or an external magnetic field. The formation of the aggregates is attributed to the presence of their remanent magnetizations, mainly to that of magnetite. The mechanism of an aggregation of this type is discussed.

  • 82. Wang, Yanmin
    et al.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Pugh, Robert
    Hydrophobic magnetite seeding of hematite ultrafines in high gradient magnetic separation1993Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 6, nr 5, s. 537-546Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The application of hydrophobic magnetite seeding to concentrate hematite ultrafines (< 10 μm) in slimes using a high gradient magnetic separator (HGMS) with coarse expanded metal matrices was investigated. It was shown that the selective aggregation at high shear rate of the seeded hematite particles (produced by surface treatment with sodium oleate and colloidal magnetite) could significantly enhance the HGMS capture of hematite ultrafines. The mechanism of selective aggregation was discussed in terms of the combination of hydrophobic and magnetic interactions.

  • 83. Yanmin, Wang
    et al.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Product size distribution in stirred media mills: Technical note2000Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 13, nr 4, s. 459-465Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A study on the control of particle size distribution (PSD) of the ground carbonate product in stirred media mills (wet Drais stirred bead mill and dry Sala Agitated Mill) is presented in this paper. The results indicated that the slope of product size distribution can be controlled by altering some operating parameters, such as size of grinding media and tip or peripheral speed. The profile of product size distribution from the stirred media mills was found to follow most closely the Rosin-Rammler-Bennett (RRB) model.

  • 84.
    Yuan, Xuemin
    et al.
    Luleå tekniska universitet.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forssberg, Eric
    Statistical interpretation of flotation kinetics for a complex sulphide ore1996Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 9, nr 4, s. 429-442Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Kinetic flotation models were applied to data from tests with reactive gases (hydrogen and sulphur dioxide) on a complex sulphide ore. The models were evaluated by statistical techniques, after non-linear regression on the model parameters. It is found that a first order model with rectangular distribution of floatability fits the test data very well. Statistical tests on copper, silver and lead kinetic data show that reactive gases have a greater influence on silver mineral flotation compared to copper-lead minerals. Sulphur dioxide generally gives higher ultimate silver recoveries than sodium bisulphite, and the magnitudes depend on the interactions between the modifiers and theflotation gases (5% H2 N2 and air). Correlation analysis suggests that silver flotation is probably determined by the floatability of a separate mineral such as tetrahedrite. Multivariate analysis on pulp chemistry data reveals that the pulp pH is the most significant variable among the pulp chemistry data, provided the grinding is iron free. The pH effect is attributed to the addition of sulphur dioxide. After autogenous or non-reducing grinding, the naturally-occurring variations in redox levels are too small to influence the flotation results, despite the tests being made with a complex sulphide ore.

  • 85.
    Zeng, Yigen
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Effects of mill feed size on product fineness and energy consumption in coarse grinding1991Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 4, nr 5-6, s. 599-609Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of some grinding parameters on the product fineness and the energy consumption under dry batchwise coarse grinding conditions are studied on rod and ball mills. A parabolic-sine equation is suitable to describe the particle size distribution. The constants in the equation are related to the grinding parameters, which permits a mathematical analysis. A relation between energy consumption and grinding parameters is also established, and the grinding effects in the rod and ball mills are compared.

  • 86.
    Zeng, Yigen
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Monitoring grinding parameters by vibration signal measurement: a primary application1994Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 7, nr 4, s. 495-501Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Grinding plays an important role on energy consumption and subsequent separation stage in a mineral processing plant. To maintain higher grinding efficieny, the operating parameters must be continuously monitored and adjusted close to the setup of the optimal operating conditions. It is difficult and expensive to trace the frequent variations of the grinding parameters by traditional methods in commercial scale operation. Since mechanical grinding emits strong vibration signals, it can be picked up commercially available instrument in the form of time-domain waveform. The variations of the vibration signals were governed by the changes of the grinding state. A primary application was studied based on the industrial scale measurements, where the mechanical vibration was picked up by an accelerometer and acoustic pressure changes by a microphone. The digitised time-domain source signals were processed by digital signal processing technique. The variable grinding parameters were the power draw, the feed rate, the pulp density, and the particle sizes of the mill feed and the ground product. By principle component analysis and parameter identification, the variations of the grinding parameters were related to the changes of the source vibration signals. By vibration measurement, a new alternative could be developed for monitoring the operating parameters in grinding.

  • 87.
    Zeng, Yigen
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Multivariate statistical analysis of vibration signals from industrial scale ball grinding1995Inngår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 8, nr 4-5, s. 389-399Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multivariate statistical modelling based on vibration signal analysis was performed at commercial scale grinding. The source digital signals consist of three channels of mechanical vibrations obtained at the axial, horizontal and vertical directions. The feed rate, power draw, pulp temperature were collected automatically by the control system while samples of the feed material and ground product of the ball mill were manually taken to determine the particle size distributions and pulp densities. Using projection to the latent structure (PLS) and/or principle component regression (PCR), empirical models between grinding parameters of interests and the vibration signals were built based on the training data set collected in two weeks, thus the new grinding parameters could be automatically predicted whenever the vibration signals were known. The modelling results show that both the PCR and PLS model can be used to predict grinding parameters online.

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