Magnets designed for HGMS make efficient use of iron to concentrate the field and have coils inside the iron return path. This design, shown in Fig. 2, allows a large material throughput. The steel wool used as a matrix in HGMS to produce high gradients is self-supporting and fills the volume of the separator, taking up 3% to 5% of the volume. A stream of material which contains 40% solids or more, as is often the case in mining, passes through the separator with its 95% or so open space, almost as if it were an open pipe. Figure 3 illustrates the principle of particle capture in HGMS. For a particle traveling toward a wire magnetized transverse to the wire axis, there is a certain capture radius. A particle passing within the capture radius is trapped by the magnetic force — if outside it, it is not. There are a number of wires throughout the volume giving a statistical probability of capturing a particle on its way through the separator. If one calculates the magnetic force in cylindrical coordinates for a paramagnetic particle, there is a maximum angle 0 for which the radial force component is positive. Outside that angle it is negative. Inside 6, a particle will be drawn in along a trajectory and captured on the wire. If it happens to pass outside the capture radius, it passes into the zone where the force is outward and will be rejected, possibly to be captured by another wire. The same is true for a diamagnetic (y = - ) particle except it will be captured where the gradient dH/dx is negative. Several approaches for removing collected particles from the matrix wires are discussed in a
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