A new fine-coal cleaning circuit, with potential near-term applications, has been evaluated for treating fine coal (i.e., 28 mesh x 0). This circuit combines a surface-based separator known as Microcel™ column flotation with an enhanced gravity separator known as the Multi-Gravity Separator (MGS). The synergistic effect of combining both processes in a single circuit resulted in improved ash and pyritic sulfur rejection with minimal losses in energy recovery. In addition, technical and economic analyses of this processing scheme suggest it compares favorably with existing post-combustion desulfurization techniques. A detailed study of the MGS included the development of a model based on fundamental principles of fluid mechanics and mineral processing. The theoretical analyses identified drum speed as the most important MGS operating parameter. To validate these findings, a detailed parametric test program was conducted using coal samples from the Pittsburgh No. 8 and Illinois No. 6 seams. A statistical analysis of the test data also showed that drum speed was the most important variable in controlling the performance of the MGS. The other controlling parameters, i.e., feed percent solids, feed rate and wash-water addition rate, were found to be of lesser importance. The experimental test results were found to be in good agreement with the theoretical predictions obtained using the model. / Ph. D.

Asphaltite is petroleum originated substance and formed by metamorphism. Turkey has 82 million tons of asphaltite reserves in Sirnak and Silopi region of Southeastern part of Anatolia. The proximate analysis of Sirnak Karatepe asphaltite sample indicated that the ash and sulfur content were 46.86 % and 5.56 %, respectively. In this study, Sirnak Karatepe asphaltite sample was concentrated by gravity separation and flotation methods. The aim of this research was to decrease the ash and sulfur content below 20% and 2%, respectively, which are the requirements of Sirnak Municipality. Gravity based cleaning equipments such as multi gravity separator, shaking table and Falcon concentrator gave no satisfactory results in terms of ash and sulfur removal. The products with lowest ash content were obtained with Falcon concentrator after two stage cleaning of -100 micrometer feed. Flotation parameters of Karatepe asphaltite were also examined during the study. As a result of multi-stage flotation with stage addition of Collector Accoal 9630 and depressant Na2SiO3 , ash content of asphaltite was decreased to 17.59 % with 15.31 % combustible recovery. Even though the ash content specification met by flotation, the sulfur content of cleaned asphaltite (6.68 % S) was more than the sulfur limit of Sirnak Municipality.

This project was specifically aimed at using increased acceleration separation, as a method to optimize the recovery of gold in an ore body mainly consisting of hematite. The specific gravity of gold is much higher in comparison to the carrying material, making it possible to separate gold from other materials such as silica, base metals and their oxides, usually associated with gravitation–gold–recovery processes. The ore body investigated in this project originated from a mined gold reef containing a large proportion of gold locked inside the gold pyrite complexes. In the mine's processing plant a gold pyrite concentrate was produced by means of a flotation process. The roasting process that followed, oxidized the pyrite to iron oxide (hematite) and sulphur dioxide. The gold particles which were locked up inside the pyrite gold complex were exposed or liberated, allowing the chemicals to penetrate the complex and dissolve the gold. After the cyanide gold extraction process, the material was pumped on to a mine reserve dump, referred to as tailings or tailings reserve dump. The tailings usually contain iron oxides, free gold, gold associated with iron oxides and gold associated with silica, and free silica, commonly referred to as calcine. The gold content on the calcine dump was significantly lower than the flotation concentrate before the extraction of the gold and it was no longer viable for the mine to process the tailings further. As the volume of the mine reserve dump increased over the years, it became viable to recover the gold in a high volume low grade plant. Several attempts were made to recover the gold in this dump, but due to the high cost of processing and milling the material, it was not done. The norm in the mining industry is that it is impossible to concentrate the gold by means of gravity separation techniques where the average particle sizes are smaller than 50 um in diameter and upgrading with inexpensive gravity separation techniques was ruled out by the mine, because the average particle sizes were too small. The dump investigated in this project differed from other reserve dumps in that the main phase of material in this dump was hematite and not silica. A suspension of this material would have different fall–out properties than other mine reserve dumps, because of the hematite's high specific gravity compared to silica. This property of the material birthed the idea that the material will respond positively to high acceleration separation, although the particle sizes were too small for effective upgrading according to the norm in the mining industry. Using acceleration concentration as a first stage in the gold recovery process the production cost per gram of gold produced could be reduced significantly. Firstly, the volume of concentrated material to be treated in the chemical extraction process was reduced ninety percent and secondly, the gold concentration was increased significantly. If the gold could be concentrated to more than twenty grams of gold per ton, it could be extracted economically with an aggressive chemical processes. This was not possible with low grade material contained in the dump. The theoretical principle, on which this project was based, was to make use of high acceleration separation to establish separation between the particles associated with the gold, and the particles not associated with gold. Applying a high gravitational force would have an influence on the velocity by which the particles would fall–out in a suspension. As the acceleration force increased the fall–out velocity would also be increased and the particles with higher specific gravity would be affected more. A factor that was equally important was the particle size and weight distribution. A large hematite particle would compete with a small gold particle due to the similarity in weight. This could cause loss in small gold particles or retention of hematite particles with no gold content. Very little scientific information was available on the material investigated and in order to assemble a concentration plant setup, the head grade and particle size distribution for both the dump and bulk sample were determined accurately. Thereafter, chemical analyses and mineralogical examination were done on a representative sample of the bulk sample, determining the chemical composition of the material. The results obtained thereof were evaluated and used to configure a pilot plant. A large bulk sample was processed in the pilot plant and from the analytical results the efficiency could be evaluated. The results at optimum acceleration forces applied, resulted in a recovery of 5% of the mass, with a gold concentrate of 90 g/t Au, which represented 58% recovery of the gold. The hematite with high specific gravity as main phase positively influenced the high acceleration separation process. It proved that if the specific gravity of particles in a suspension were increased, high acceleration separation could be applied effectively to separate much smaller particle sizes. / Thesis (M.Sc. Engineering Sciences (Chemical and Minerals Engineering))--North-West University, Potchefstroom Campus, 2012.

This project was specifically aimed at using increased acceleration separation, as a method to optimize the recovery of gold in an ore body mainly consisting of hematite. The specific gravity of gold is much higher in comparison to the carrying material, making it possible to separate gold from other materials such as silica, base metals and their oxides, usually associated with gravitation–gold–recovery processes. The ore body investigated in this project originated from a mined gold reef containing a large proportion of gold locked inside the gold pyrite complexes. In the mine's processing plant a gold pyrite concentrate was produced by means of a flotation process. The roasting process that followed, oxidized the pyrite to iron oxide (hematite) and sulphur dioxide. The gold particles which were locked up inside the pyrite gold complex were exposed or liberated, allowing the chemicals to penetrate the complex and dissolve the gold. After the cyanide gold extraction process, the material was pumped on to a mine reserve dump, referred to as tailings or tailings reserve dump. The tailings usually contain iron oxides, free gold, gold associated with iron oxides and gold associated with silica, and free silica, commonly referred to as calcine. The gold content on the calcine dump was significantly lower than the flotation concentrate before the extraction of the gold and it was no longer viable for the mine to process the tailings further. As the volume of the mine reserve dump increased over the years, it became viable to recover the gold in a high volume low grade plant. Several attempts were made to recover the gold in this dump, but due to the high cost of processing and milling the material, it was not done. The norm in the mining industry is that it is impossible to concentrate the gold by means of gravity separation techniques where the average particle sizes are smaller than 50 um in diameter and upgrading with inexpensive gravity separation techniques was ruled out by the mine, because the average particle sizes were too small. The dump investigated in this project differed from other reserve dumps in that the main phase of material in this dump was hematite and not silica. A suspension of this material would have different fall–out properties than other mine reserve dumps, because of the hematite's high specific gravity compared to silica. This property of the material birthed the idea that the material will respond positively to high acceleration separation, although the particle sizes were too small for effective upgrading according to the norm in the mining industry. Using acceleration concentration as a first stage in the gold recovery process the production cost per gram of gold produced could be reduced significantly. Firstly, the volume of concentrated material to be treated in the chemical extraction process was reduced ninety percent and secondly, the gold concentration was increased significantly. If the gold could be concentrated to more than twenty grams of gold per ton, it could be extracted economically with an aggressive chemical processes. This was not possible with low grade material contained in the dump. The theoretical principle, on which this project was based, was to make use of high acceleration separation to establish separation between the particles associated with the gold, and the particles not associated with gold. Applying a high gravitational force would have an influence on the velocity by which the particles would fall–out in a suspension. As the acceleration force increased the fall–out velocity would also be increased and the particles with higher specific gravity would be affected more. A factor that was equally important was the particle size and weight distribution. A large hematite particle would compete with a small gold particle due to the similarity in weight. This could cause loss in small gold particles or retention of hematite particles with no gold content. Very little scientific information was available on the material investigated and in order to assemble a concentration plant setup, the head grade and particle size distribution for both the dump and bulk sample were determined accurately. Thereafter, chemical analyses and mineralogical examination were done on a representative sample of the bulk sample, determining the chemical composition of the material. The results obtained thereof were evaluated and used to configure a pilot plant. A large bulk sample was processed in the pilot plant and from the analytical results the efficiency could be evaluated. The results at optimum acceleration forces applied, resulted in a recovery of 5% of the mass, with a gold concentrate of 90 g/t Au, which represented 58% recovery of the gold. The hematite with high specific gravity as main phase positively influenced the high acceleration separation process. It proved that if the specific gravity of particles in a suspension were increased, high acceleration separation could be applied effectively to separate much smaller particle sizes. / Thesis (M.Sc. Engineering Sciences (Chemical and Minerals Engineering))--North-West University, Potchefstroom Campus, 2012.

Tungsten (W) is listed among the European Union (EU) critical raw materials (CRMs) for its supply risk and economic importance. Primarily, tungsten is produced from scheelite and wolframite mineral ores with 0.08-1.5% tungsten trioxide (WO3) grade. However, as primary deposits for these resources are becoming less or lower in grade, alternative sources need to be explored. These alternative tungsten sources include scrap from end-of-life products, mine waste and rejects from the ore beneficiation processes (tailings). The latter alternative source is the focus within this thesis. Historical tailings repositories often pose environmental risks but may also become secondary sources of CRMs. This is because of relatively high minerals and metals content due to less efficient extraction methods and/or relatively low metal prices at the time of active mining. Therefore, reprocessing of such tailings is not only a supply risk-reducing measure but also an approach to remediation that contributes to the mining industry’s aim of moving towards a circular economy. The aim of this thesis has been to develop efficient methods for separating valuable minerals from the tailings in order to leave behind a stable and environmentally safe residue. Geometallurgical studies were conducted by collecting drill core samples from the Smaltjärnen tailings repository in Yxsjöberg, Sweden, for evaluating the potential of this repository for further processing. The tailings were originally produced from the ore that was mined by Yxsjö Mines while it was in operation from 1935 to 1963, with average ore grades of 0.3-0.4 wt.% WO3, 0.2 wt.% Cu and 5-6 wt.% fluorspar. The exploited minerals were scheelite for W, chalcopyrite for Cu and fluorspar. The tailings repository is estimated to have about 2.2 million tons of tailings covering an area of 26 hectares, with elemental concentrations of 1-2 wt.% S, 0.02-0.2 wt.% Cu, 0.02-0.3 wt.% W, 0.02-0.04 wt.% Sn and 0.02-0.03 wt.% Be. Sampling and characterization of the historical tailings were conducted based on geometallurgical units (i.e. a distinction between different layers and locations in the repository), followed by metallurgical test work. The tailings were characterized with regard to color and granulometry, particle size distribution, chemical composition, scheelite mineral occurrence, texture and mineral liberation, as well as mineralogical composition. Based on a comprehensive literature survey, tailings characteristics, and assessment of the earlier processes from which the Yxsjöberg tailings were produced, feasible separation methods were pre-selected involving dry low-intensity magnetic separation (LIMS) and high intensity magnetic separation (HIMS), enhanced gravity separation (EGS) using a Knelson concentrator, and batch froth flotation. The average WO3 and Cu concentration in these tailings based on the sampled locations was 0.15 % and 0.11 % respectively. Applying them to the estimated 2.2 million tons of tailings in this repository gives approximately 3300 tons of WO3 and 2512 tons of Cu. From the metallurgical test work, several feasible processing routes have been identified that need to be further assessed based on the economic and environmental criteria. / REMinE (Improve Resource Efficiency and Minimize Environmental Footprint)