No description available.

No description available.

No description available.

The processing of nickeliferous laterites to produce nickel metal is both complex and energy intensive. Since most laterites are found in remote regions, the capital costs for the infrastructure can exceed those for the process itself. The low temperature sulphidation of lateritic ores to produce an intermediate nickel concentrate for further processing offers a number of potential advantages, such as lower energy consumption and a relatively simple flowsheet. In this research, the sulphidation of a nickeliferous lateritic ore was investigated between the temperatures of 450-1100oC and sulphur additions of between 25-1000 kg of sulphur per tonne of ore. The experiments demonstrated that the nickel oxide within the ore can be selectively sulphidized to a nickel-iron sulphide. It was found that both the grade and the sulphidation degree largely depended upon the temperature and the sulphur additions, with temperatures above 550oC exhibiting the highest nickel sulphidation extents and grades. A DTA/TGA with mass spectrometer was used to further elucidate the nature of the phase transformations that occur upon heating of the ore, in the presence of sulphur. It was found that the Fe-Ni-S phase formed at low temperatures was submicron in nature and heating to temperatures of 1050oC-1100oC allowed for the growth of the sulphides to a d80 of up to 14 µm due to increased sulphide mobility, associated with the formation of a liquid sulphide matte with dissolved oxygen. Flotation studies conducted on 60 g samples showed that the sulphides formed respond to flotation with maximum grades of up to 6-7 wt% nickel being achieved and average grades of between 4-5 wt% nickel. Recoveries were approximately 50% on a sulphide basis and it was determined that the low nickel grades were due to the entrainment of magnetite fines. / Thesis (Ph.D, Mining Engineering) -- Queen's University, 2012-01-29 14:14:18.704

No description available.

No description available.

Thesis (PhD)--University of South Australia, 2004.

Thesis (PhD)--University of South Australia, 1994

Thesis (PhD) -- University of South Australia, 1994

A simplified froth model is proposed, which describes the froth transportation characteristics in three different regions of a flotation froth. In the stagnant region, new froth arrives at the same rate as froth collapses and returns to the pulp, so there is no net exchange between this region and other regions. In the second region, the froth rises vertically from the pulp-froth interface until it reaches the concentrate launder weir level. Then, the froth moves horizontally towards the launders in the surface froth region. Based on the mass balance of air passing through the froth phase, a mathematical model of froth transportation is developed for a cylindrical flotation cell. The model describes froth transportation time from the point of entry at the pulp-froth interface to the concentrate launder as a function of the geometrical dimensions of the flotation cell, the concentrate launder and froth crowder designs, as well as cell operating conditions and froth properties. The model was validated in two industrial scale flotation cells, viz. an Outokumpu 3 m3 tank cell at the Western Metals Hellyer concentrator and an Outokumpu 50 m3 tank cell at the Anglo Platinum Bafokeng-Rasimone concentrator, under various cell operating conditions and concentrate launder/froth crowder configurations. The results show that the model in general fits the experimental data well. Model fitting can be improved by taking into account the actual air dispersion profile in the flotation cell. Although the current form of froth transportation model does not explicitly relate the surface froth velocity to the pulp level setting, it was found during the plant test work that froth height can affect froth transportation and that the effect is associated with ore type and froth viscosity. A preliminary investigation into froth rheology was carried out separately in the Oukokumput 3 m3 tank cell at the Xstrata Mt Isa copper concentrator. The results are included in this thesis for future reference. In addition to not accounting for the froth height effect (pulp level setting), the current froth transportation also has some limitations when used for prediction purposes. There are three parameters in the model related to the froth properties – the air hold-up in the froth (f), the froth height above the concentrate launder (hf) and the froth instability factor (). These parameters depend on the ore and the cell operating conditions as well as the cell design, and cannot be modelled at present. Nevertheless, they can be measured directly in an existing flotation cell, which allows the model to be used for process control. Experimental measurement procedures and measured results from the industrial flotation cells are given in this thesis. The effect of the cell operating conditions is discussed. Finally, this thesis proposes a number of potential model applications, including the modelling of froth recovery of attached particles, the modelling of water recovery and entrainment, criteria for concentrate launder and froth crowder design, and a model for flotation process control based on froth images.