The theory and application of permanently magnetised materials to fine particle processing

Boorman, Christopher Hugh (1987) The theory and application of permanently magnetised materials to fine particle processing. University of Southampton, Doctoral Thesis.

Abstract

This thesis reports on the use of permanently magnetised matrix materials for filtration in the processing industry, with particular emphasis towards applications in the nuclear Industry. A prototype filter was designed and tested both in the laboratory and in-situ at nuclear testing facilities. The results obtained showed that an efficient filter, conforming to the rigid specifications imposed by the nuclear Industry, could be constructed utilising permanently magnetised materials. Theoretical models have been developed to look at both the trajectories of weakly magnetic particles in the vicinity of the capturing surfaces and the optimum build-up configuration on the surfaces of the collector. The trajectory model indicated that particles would be captured in a similar fashion to that observed in High Gradient Magnetic Separation processes - although the attractive and repulsive quadrants were interchanged. This is in agreement with experimental results. These results also show a high efficiency of capture within the filter. However, when considering gravitational effects the theoretical model indicates a smaller build-up of particles than that observed in experiment. It is postulated that this is due to the presence of other forces, such as van der Waals forces and frictional forces, that bind the particles together. This model also suggests that there is an optimum field for which capture is a maximum. Experiment also shows that magnetic fluids can be used effectively to wash captured particles from the matrix.

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