A superconducting magnetic separator with magnetically balanced matrix

In a magnetic separator, the field gradients around magnetized fibers (the matrix) are used to capture particles. To remove the particles from the fibers the background magnetic field must be reduced to zero. The large superconducting magnets which are used to produce the background field cannot be de-energized quickly. As the separator is fully loaded in approximately 1000 s, a way was sought to reduce the cleaning time significantly. It is reported that cleaning time was reduced by balancing the magnetic forces (which hold the matrix in the magnetic field) with a counter force generated by subsidiary coils attached to the matrix. The position of the matrix is then determined by the magnitude and direction of the current in the subsidiary coils. Theoretical and initial experimental results are presented indicating that removal times of less than 5 s can be achieved, which is sufficient to give reasonable cycle times for dry coal desulphurization when the magnetic separator is part of the milling circuit.