| 1. |
- Asbjörnsson, Gauti, 1985, et al.
(författare)
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A Training Simulator for Crushing Plant Operators
- 2012
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Ingår i: XXVI International Mineral Processing Congress (IMPC 2012: Innovative Processing for Sustainable Growth; New Delhi; India; 24 September 2012 through 28 September 2012). - 9788190171434 ; , s. 2164-2171
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Konferensbidrag (refereegranskat)abstract
- Crushing plants are widely used around the world as a pre-processing step in the mineral and mining industries and as standalone processing plants in the aggregates industry. Despite automation and different advanced model predictive control a lot of the process is still managed by operators. The operators affect a lot of the performance. The numbers of the improvement they can achieve are at least as big as the advanced control algorithms’, today. Therefore it is also important to train the operators so they know how to behave in different situations. Models for crushers and other production units have been developed during the years and the latest add is the different units’ dynamic behavior being brought in, which gives the crushing plants dynamic time dependant performance. This can be used as a simulator for operators training. By connecting a Human Machine Interface (HMI) to a dynamic simulator with the models incorporated, a training environment for operators can be achieved. In this paper a dynamic crushing plant simulator implemented in MATLAB/SIMULINK has been connected to an HMI via a PLC. The HMI is placed in a control room at the university and complemented with monitors showing sequences from the process connected to the simulations, thus creating a realistic control room for training. In the created training environment the operators can be trained under realistic conditions. Simple training scenarios and how they could be simulated are discussed. Apart from the increased level of knowledge and experience among the operators, the time is an important factor. While a real crushing plant is still being built, the operators to be can already be trained, saving a lot of the commissioning time.
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| 2. |
- Asbjörnsson, Gauti, 1985, et al.
(författare)
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Modelling Dynamic Behaviour of Storage Bins for Material Handling in Dynamic Simulations
- 2012
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Ingår i: XXVI International Mineral Processing Congress (IMPC 2012: Innovative Processing for Sustainable Growth; New Delhi; India; 24 September 2012 through 28 September 2012). - 9788190171434 ; , s. 258-267
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Konferensbidrag (refereegranskat)abstract
- Material handling is an essential part of the aggregate and mining industries. Mixing and blending of granular material can affect the grading and particle size distribution of the material leaving the system. Segregation and variability can cause problems in the downstream process while insufficient capacity will disturb upstream processes.Process plants utilize surge bins for handling recycle streams of material and act as a buffer for the process. The flow through the surge bin is usually controlled by a simple PID controller or PID controller in combinations with a plant-wide controller. Even though the surge bins play an important role of smoothening out the plant and creating a steady operating condition are they seldom included in plant simulations. This can lead to a number of problems in the form of decreased plant capacity, plant lockdown, and even operation units malfunctioning. The main objective of this study is to investigate the dynamic behavior in surge bins and develop a model more suitable for representing this behavior, which can occur during operation, for dynamic simulations. The proposed model adopts vertical layers which allow for flows between segments depending on the level of neighboring segments. This enables both the representing of segregation within the system and gives an indication on the effects from different inlet- and outlet placements. The proposed model was developed in Matlab/Simulink and validated against an actual bin with the total capacity of 700 m3 in platinum ore application. With the new bin model significantly higher fidelity and more accurate dynamic simulation results were achieved.
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| 3. |
- Ikumapayi, Fatai, et al.
(författare)
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Recycling process water in complex sulphide ore flotation
- 2012
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Ingår i: XXVI International Mineral Processing Congress (IMPC) 2012. - New Dehli : The Indian Institute of Metals. - 9788190171434 ; , s. 4411-4425
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Konferensbidrag (refereegranskat)abstract
- An approach to environmental sustainability and improved process economy, in sulphide minerals production is recycling of process water in flotation of complex sulphide ores, although the chemistry of process water may be a critical issue to flotation efficiency. The influence of major components of calcium and sulphate ions in process water on xanthate collector adsorption and flotation response using pure chalcopyrite, galena and sphalerite minerals were investigated by Hallimond flotation, zeta-potential measurement, FTIR and XPS spectroscopy studies, while bench scale flotation tests were also carried out using complex sulphide ores. The impact of the species in flotation was comprehended using deionised water, tap water, process water and simulated water containing equivalent amount of calcium and sulphate species in process water. Hallimond flotation results showed a decrease of chalcopyrite and galena recovery in process water and also in the presence of calcium and sulphate ions in both deionised and process waters, whereas sphalerite does not respond to flotation. The adsorption of calcium and metal ions but not sulphate ions on the minerals is evidenced by zeta-potential data. FTIR and XPS studies revealed the presence of surface oxidized sulfoxy species and surface calcium carbonates on chalcopyrite in the presence of process water and water containing calcium ions, surface oxidized sulfoxy and carbonate species on galena in the presence of deionised water, process water and water containing calcium and sulphate ions, all at flotation pH 10.5, and these surface species influenced xanthate adsorption. The presence of surface oxidized sulfoxy and carbonate species at the sphalerite flotation pH 11.5 were seen in the presence of deionised water, process water and water containing calcium and sulphate ions, but the surface species does not influence xanthate adsorption. Bench scale flotation using two different complex sulphide ores showed that chalcopyrite, galena and sphalerite recoveries are better in process water than tap water. The studies showed that the process water can be recycled in flotation with no detrimental effect on grade and recovery of sulphide minerals.
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| 4. |
- Manouchehri, Hamid-Reza, et al.
(författare)
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Effect of temperature in flotation of Zn from massive sulfide ores
- 2012
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Ingår i: XXVI International Mineral Processing Congress. - New Dehli : The Indian Institute of Metals. - 9788190171434 ; , s. 3227-3238
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Konferensbidrag (refereegranskat)abstract
- Large variations in flotation characteristics of minerals have been observed in winter and summer in plant practices as a result of changes in pulp temperature. Variations in temperature may affect the quality for pulp and related process water through changes in dissociation of different chemical species within the pulp, as well as changing in gas and metal hydroxide solubility, reagent adsorption and its stability on mineral surfaces, water/pulp viscosity, etc. All of these affect the flotation characteristics of specific mineral to some degree or another. It has been observed in Cu-Pb-Zn and/or Pb-Zn sulfides flotation that sphalerite (ZnS) flotation is strongly affected by changes in pulp temperature. Plant practices have shown that at the both low, e.g., T <10-12°C, and high, e.g., T > 60°C, the recovery for copper activated sphalerite is dramatically dropped. Within this paper the effect of pulp temperature on flotation characteristics of sphalerite is brought into considerations and laboratory flotation tests were conducted in conjunction with surface and solution chemistry analysis to understand the effect of temperature on sphalerite recovery. The effect of temperature seems to be complex since the temperature affects both the physical (hydrodynamics) and chemical phenomena in the flotation cell. In fact all sub-processes in flotation, i.e., collision, attachment and detachment, are affected by changing in temperature. Experimental results indicating that at alkaline pH values, e.g., 8.5 to 10.5, the recovery for copper-activated sphalerite is dramatically reduced when temperature is below 10-12°C, which is in agreement with plant practice at Boliden's Garpenberg plant in Sweden. However, results from other studies indicated that the zinc recovery is also considerably decreased at high pulp temperatures, i.e., 62°C and above.
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| 5. |
- Martinsson, Olof, et al.
(författare)
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Apatite for extraction - Mineralogy of apatite and ree in the kiirunavaara Fe-deposit
- 2012
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Ingår i: XXVI International Mineral Processing Congress. - New Dehli : The Indian Institute of Metals. - 9788190171434 ; , s. 3287-3297
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Konferensbidrag (refereegranskat)abstract
- The Kiruna area is an important mining province in northern Sweden, which is dominated by Fe- and Cu-Au deposits. Economically most important for the region, are the apatite iron ores with an annual production of c. 43 M ton of crude Fe-ore and a total production of more than 2000 M ton of ore the last 100 years. The apatite iron ores in the Kiruna area are dominated by either Magnetite or Haematite and contain varying amounts of apatite giving them a content of Fe and P, which varies between 30-70 % and 0.05-5 %, respectively. A typical geochemical feature of the ores is the strong enrichment of REE that is caused by a high content of REE in apatite and the occurrence of Allanite and Monazite containing 22.4 and 69.8 wt% REO, respectively. At Kiirunavaara, the content of REE in apatite varies between 0.07 to 1.57 wt% REO with a dominance for the light rare earths. The variation in REE-content of apatite depending on textural and paragenetic aspects is not known but apatite grains may display a strong LREE-depletion due to hydrothermal alteration. Monazite occurs as rod-shaped or tabular inclusions in apatite and is suggested, to have formed in response to hydrothermal alteration of apatite after the emplacement of the ore. Inclusions are mainly found in the central part of apatite grains occurring in veins and schliren, while they are rare in apatite occurring disseminated in the ore. Monazite also occurs as larger grains outside apatite and together with Allanite is found in texturally and paragenetically different settings within the ore. These occurrences of REE-minerals may largely be a product of LREE mobilized by alteration of apatite after the emplacement of the ore. However, REE-minerals including Allanite and Monazite might also have formed directly from late magmatic fluids.
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| 6. |
- Nurni, Viswanathan N., et al.
(författare)
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Model for reduction of iron oxide pellet with a C-O-H-N gas mixture considering water gas shift equilibrium in the gas while it diffuses through the product layer
- 2012
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Ingår i: XXVI International Mineral Processing Congress. - New Delhi : The Indian Institute of Metals. - 9788190171434 ; , s. 3921-3928
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Konferensbidrag (refereegranskat)abstract
- In metallurgical processes, a higher usage of hydrocarbons is encouraged to bring down carbon emissions. In this regard, numerous investigations on reduction of oxides by C-O-H-N gas mixture have been reported. Attempts to simulate these reduction processes using shrinking core model, one of the common models used for such studies, have under predicted the reduction rates. This is perhaps owing to the fact that the homogeneous reaction in the gas phase is not being considered. If the reaction temperatures are above 1000K, which is generally so for many reduction processes, the homogeneous gas reaction rates are expected to be so high that one can assume local equilibrium in the gas phase. In the present study, reduction of wustite in a C-O-H-N gas mixture has been modeled using a shrinking core model considering the water gas shift equilibrium in the gas while it diffuses through the product layer.
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| 7. |
- Pålsson, Bertil, et al.
(författare)
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Apatite for extraction- II flotation of apatite and rare earth elements from old tailings dumps
- 2012
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Ingår i: XXVI International Mineral Processing Congress. - New Delhi : The Indian Institute of Metals. - 9788190171434 ; , s. 4064-4074
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Konferensbidrag (refereegranskat)abstract
- The most common REE containing mineral that is worked today is bastnäsite. It means that mineral processes are adapted to it and that the metallurgical separation techniques for winning of individual REE are adapted to bastnäsite concentrates. For all other deposit types, suitable mineral processing methods and separation technologies need to be adapted and/or developed.Preliminary mineralogical analyses indicate that slightly less than half of the REE in the tailings dumps at LKAB/Kiruna are associated to apatite. The rest is in the minerals monazite (maybe associated to apatite) and allanite. At least allanite is probably not floatable with reagents commonly used for apatite. Mass and element distributions for the tailings sand reveal that very little apatite is present above 300 μm, and that approx. 30 % is below 20 μm. REE does not follow P2O5 completely and are also present in coarser fractions.Flotation results show that the best condition for both apatite and REE winning is pH 9, high collector addition and low dosage of water glass. Under these conditions, the lab-scale flotation gives an apatite concentrate with at least 30 % P2O5 at 70 % recovery. REE follows apatite in the cleaner steps but only partly. Its recovery is approx. half compared with apatite. The reason for the low REE recovery is likely to be that REE to a large extent is trapped in non-winnable minerals, especially allanite. The REE grades in the concentrate are expected to be in the range 3000 – 4500 g/ton.
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| 8. |
- Sand, Anders, et al.
(författare)
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Modeling of coal compaction within stamp-charged cokemaking by means of computational physics
- 2012
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Ingår i: XXVI International Mineral Processing Congress. - New Dehli : The Indian Institute of Metals. - 9788190171434 ; , s. 4696-4706
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Konferensbidrag (refereegranskat)abstract
- Within stamp-charged coke making, a large volume of coal is compacted to one single coal cake before entering the coke oven chamber. This is done by means of several falling stampers in a stamping machine having a mold nearly of the oven’s dimensions. Producing a high quality coke from inferior coals requires a cake density of approximately 80% of the coal density. Besides this, the industrial stamp-charging process demands a minimum mechanical strength of the coal cake to move it from the stamping mold into the oven chamber without failure. Densification and the build up of cake strength were investigated earlier in stamping tests using a micro-stamping device. The quantities derived from these tests (as e.g. cake density or porosity) represent average values for the entire cake. Statements describing the local compaction state at different heights are difficult to achieve without destructing the cake. In order to gain better insight into the densification process and the inner structure of the coal cake, a computational model based on the Discrete Element Method (DEM) was set up using 2 and also 3-dimensional simulation software. The stamper’s position and velocity as well as the force acting on the stamper were monitored and the model’s response was compared against measurement data from laboratory stamping tests. It was possible to reproduce the force and displacement pattern of the stamper in response to the viscoelastic properties of the cake using standard DEM bonding and contact models. Furthermore, the rearrangement of particles in response to the compaction by the stamper was tracked by calculating their displacement at the point the stamper hit the coal surface. The latter can also be used as an indicator of particle deformation or breakage. By defining control points at different heights the particle displacement, stress and strain rates, porosity could be studied at different heights.
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| 9. |
- Sandström, Åke, et al.
(författare)
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Apatite for extraction - Leaching of kiirunavaara apatite for simultaneous production of fertilizers and REE
- 2012
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Ingår i: XXVI International Mineral Processing Congress. - New Dehli : The Indian Institute of Metals. - 9788190171434 ; , s. 4707-4714
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Konferensbidrag (refereegranskat)abstract
- Loussavaara-KiirunavaaraAB's (LKAB) iron ore mine, Kiirunavaara, is of magnetite type and associated with apatite, a calcium phosphate mineral. Rare earth elements (REE) have been found in connection with the apatite but also in other minerals. An apatite concentrate was produced by flotation, in order to investigate the possibilities to extract REE from the apatite by hydrometallurgical means. The content of rare earth elements calculated as oxides (REO) was 0.44% in the concentrate. Initially, leaching was done with large excess of sulfuric acid, hydrochloric acid, and nitric acid to study the REE solubility with different acids. In sulfuric acid, the leaching recoveries of the different REE varied between 35% and 69%. The reasons for the relative low recoveries, were that the rare earth elements precipitated together with huge amounts of gypsum, that was formed during leaching. However, both hydrochloric- and nitric acid gave almost complete extraction of the REE into solution. Analysis of the small leaching residue obtained, revealed, that mainly the light REE remained in the residue indicating that a small part of the light REE were present in the concentrate, in some acid, insoluble mineral other than apatite. With the aim to separate the REE from the phosphoric acid, the solutions from hydrochloric- and nitric acid leaching were neutralized to a pH of approximately 2 with ammonia. During neutralization, REE were precipitated as phosphates with good recoveries and a concentrate of 10.5% REO suitable for further upgrading was obtained, while the remaining solution can be used for fertilizer production. In further solvent extraction studies, it was shown, that after re-dissolution the REE could be effectively extracted by Cyanex 923, thus allowing for purification from calcium and phosphate ions. The REE were finally stripped from the organic phase and a REE nitrate solution was produced.
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