Thesis (M. Eng.)(Metallurgical)--University of Pretoria, 2001. / Includes bibliographic references. Available on the Internet via the World Wide Web.

Thesis ([PhDEngineeringMineralsandMaterials])--University of South Australia, 2004.

Thesis (M.Sc. 1963)--University of Adelaide. / Typewr.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1949. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [95]-103).

Thesis (Ph.D.)--University of Oklahoma, 1984. / Bibliography: leaves 130-139.

Thesis (M.S.)--Wisconsin. / Bibliography; leaves 59-60.

Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 50-[51]).

Particle fracture is the elementary process that governs comminution. In industrial machines particle breakage occurs mainly through three mechanisms: impact, abrasion and attrition. Of these mechanisms, impact breakage is known to be the most basic form of particle size reduction. Comminution devices are highly inefficient, as the energy used for particle breakage relative to that consumed by the equipment is low and reported to be between 1-2 %. As such, understanding the fundamentals of particle fracture is crucial for the development of energy efficient particle size reduction methods. Research done towards investigating particle fracture under impact loading has led to the development of several devices which include the twin pendulum device, drop weight tester, Split Hopkinson Pressure Bar, Rotary Breakage Tester and the Short Impact Load Cell. In this study the Short Impact Load Cell (SILC) was used to conduct bed breakage experiments on partially confined particles. Breakage tests using this device were conducted by vertically releasing a steel ball of known mass onto a bed of particles from a known height. The bed rested on a steel rod which was fitted with strain gauges to measure the particle response to impact loading. Tests were conducted on two ores, blue stone and UG2, to investigate the effect of three variables: steel ball mass, drop height and bed depth on the breakage behaviour of particles. The effect of each variable was investigated by evaluating the peak forces obtained, the particle fracture energy and the degree of particle breakage attained. For both ores it was found that the peak force increased linearly with increasing steel ball mass and drop height, and it was found that the drop height had a greater effect on the peak force than the steel ball mass. The maximum peak forces were obtained at one layer of particles and increasing the bed depth generally led to a reduction in the peak force. An exponential relationship was found between the peak force and bed depth, where the peak force decreased with increasing bed depth. It was found that the blue stone particles did not break at the range of input energies used in this work, therefore no fracture energy results were reported for blue stone. The fracture energy values for UG2 were low, where the maximum energy used for particle fracture was 2.7 % of the input energy. There was no direct correlation between the fracture energy and the steel ball mass, drop height and bed depth; however it was found that the bed depth had a larger effect on the fracture energy compared to both the steel ball mass and drop height. The greatest amount of energy used for fracture was generally obtained at the largest input energies using the 357 and 510 g balls. The optimum drop height which resulted in the highest fracture energy was generally found to be either 240 or 300 mm. A bed depth of five layers was found to be the optimum bed depth that allowed for the highest amount of energy to be utilized for breakage. No breakage results were obtained for blue stone due to the hardness and stiffness of the ore. For UG2, tests conducted at the same bed depth showed a trend in which the breakage initially increased greatly with increasing input energy; however at larger input energies the breakage obtained approached a constant value. Although the input energy was varied by changing both the steel ball mass and the drop height, the results showed that the degree of breakage was more dependent on the steel ball mass compared to the drop height. For all tests conducted, the maximum breakage was obtained at one layer of particles and increasing the bed depth led to a decrease in the breakage obtained. The results showed that the fracture energy and the degree of breakage were not directly related. It was found that there is an optimum amount of energy utilized for fracture that leads to the greatest breakage, where an in increase in the energy beyond the optimum point does not significantly affect the breakage obtained.

The Bushveld complex is the largest ore body in the world hosting platinum group elements (PGEs). It is a stratified orebody with three major reefs namely, the Merensky reef, UG2 reef and the Platreef. Platinum and palladium are the most abundant PGEs found in the Bushveld complex. They occur in the form of minerals/mineral phases with elements such as sulphur, tellurium, arsenic and iron. These minerals/mineral phases are associated with base metal sulphides occuring along grain boundaries. Unlike the Merensky and UG2 reef, the Platreef is almost barren of PGE sulphides and the distribution of base metals sulphides and their association with PGMs is erratic. Froth flotation targeted at the recovery of base metal sulphides is implemented in PGM concentrators to concentrate PGMs. Flotation of sulphide minerals is achieved with the use of thiol collectors to create hydrophobicity, and copper sulphate is often used to improve hydrophobicity and therefore recovery. Sodium ethyl xanthate (SEX) and sodium diethyl dithiophosphate (DTP) are commonly used as collectors on PGM concentrators. The erratic mineral variations in the Platreef ore, however, raise the question of the effectiveness of the application of sulphide mineral flotation techniques on this ore. Previous work by Shackleton, (2007) investigated the flotation of PGE tellurides, sulphides and arsenides. The study highlighted that the mechanisms with which these minerals interact with collectors and with copper sulphate was poorly understood. It is as a result of the findings of Shackleton's work that this study aims to elucidate the fundamental interactions of telluride and sulphide PGMs with thiol collectors and with copper sulphate. Subsequently this work also aims to compare the behaviour of these reagents on sulphide PGMs and telluride PGMs.

Due to the depletion of coarser grained ores, more mineralogically complex ores are being treated. These complex ores usually have finer grained valuable minerals. Liberation of these finer grained valuable minerals lies in grinding finer. Grinding to these fine sizes is energy intensive and using standard ball mills are energy inefficient at these sizes (P80 < 75μm). Therefore, stirred mills are becoming increasingly prevalent in the mineral processing industry. In order to optimize these mills, the effects and mechanisms of the significant variables need to be understood. This project investigated operating parameters against performance in a laboratory scale vertical stirred mill (Deswik mill), in an ultrafine grinding (UFG) application of MG2 reef in the bushveld igneous complex. The operating variables that were investigated are stirrer speed, solids concentration, media size and media filling. The Kwade stress energy model was tested on the grinding results. The grinding performance was quantified in two ways, i.e. grinding efficiency and grinding rate. The grinding performance for this study was also investigated through a statistical analysis. The experiments was designed using a face centred central composite design (FCCD) and the results was statistically analysed using a design of experiments (DOE) software.