| This thesis examined the density separation of coal using a magnetic fluid separator. The yield data were consistent with the separations obtained using other dense media such as organic liquids and zinc bromide solutions. However, the ash values were consistently higher at low relative densities for separations made in magnetic fluids. The differences were explained by particle misplacement resulting from a non-uniform effective density in the separation cell which was caused by the non-uniformity of the magnetic field gradient in the air gap.; The effect of magnet pole geometries on the magnetic field distribution was investigated using finite element simulations. It was found that magnetic fields can be adequately simulated for a wide variety of pole geometries, providing an important instrument for magnet shape optimization. Furthermore, density simulations in gravity-based separators showed a good agreement with the measured density values. An evaluation of the effect of various magnet shapes on the magnetic fluid effective density demonstrated that the non-uniformity in the effective density distribution within the separation volume could be greatly reduced. This study also analyzed the effect of scaling-up the magnet poles and/or the magnet gap, demonstrating that the same effective density distributions found in smaller separators can be achieved for larger separators.; The analysis of magnetic fluid separations in a centrifuge indicates that density separations of non-magnetic particles are feasible, and that the system behaves similarly to a dense liquid-based system. In addition, the separation of paramagnetic particles can be improved using a stronger fluid magnetization than that required for the separation of non-magnetic particles. However, a further increase in the fluid magnetization showed a decrease in the separation efficiency, demonstrating that the fluid magnetization cannot be increased indefinitely.; The analysis of magnetic fluid cycloning revealed that no combination of magnetic field strength and magnetic fluid magnetization could be obtained that would give a practical effective density in the magnetic fluid using a magnet around the periphery of the cyclone, because of inherently high slurry tangential velocities in cyclones. Hence, density separation in a magnetic fluid cyclone with this magnet geometry does not appear to be feasible. |
