Continuous and batch high gradient magnetic filtration (HGMF) of gases.

Conventional magnetic separation is a long established
technique in mineral processing for tramp iron, and for
concentrating magnetic ores. Its use was generally restricted to the separation of strongly magnetic materials. Recently, the application of this method has been slightly modified to include the filtration of micron sized paramagnetic particles. This method is called the High Gradient Magnetic Separation (HGMS) and
maximizes the magnetic forces by using electromagnets to separate small and weakly paramagnetic particles. The main advantage is that separation is highly efficient and can be carried out at high flow rates with a minimum head loss across the filter.
In this study, tests were carried out with two types of
filters - randomly packed cylindrical wire filter matrix and well ordered woven wires. Cupric Oxide (CuO) dust with particle distribution o f less than two microns was used for the investigation. The CuO was chosen as a representative paramagnetic dust. Specific tests were carried out to determine the effects of individual operating parameters such as matrix packing fraction, magnetic field strength, and gas velocity on
filter loadability and efficiency.
The results showed that for both randomly packed and
woven wire filters, increasing packing fraction produced better load ability and sustained capture efficiency, although not in proportion to the mass of wire used. Increasing entrainment velocity produced slightly improved result for randomly packed filter unlike that obtained from woven wires.
A novel idea of applying a fluid diverter to HGMF was
introduced. The main objective was to increase the flow residence time in the filter matrix , thereby increasing the chances of more particles being captured. The results obtained from the application of fluid flow diverter showed poor collection for very small particles but good filtration for larger particles.
Prediction of theoretical collection efficiencies were
made using the single wire single particle model. The collection efficiencies of the, smallest particle range agreed with those obtained from experiments but large deviations were present for the biggest particles in the case of random wires.
Pressure drop measurements were also carried out for
the filters used over the range of operating parameters applied.
The results were plotted in two basic forms that incorporated flexibility in their interpretation and usage.