Development of Dry type Fluidized High Gradient Magnetic Separation Device for Coal Powder Beneficiation

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A novel dry type high gradient magnetic separation (HGMS) device comprized with a fluidized-bed has been developed for the purpose of coal powder beneficiation for the electric power plant. Three types of FHGMS have been tested. The basic type A consisting of parallel and straight ferro-magnetic wires was examined with parameters of wire size, number of wires, coal particle size range, magnetic flux density, carrier gas velocity, amount of feed (processed coal) and so on. The carrier gas velocity where weight of mags (trapped part on wires) is maximum, and the gas velocity where the ash reduction ratio is maximum, are found to be different. That is, the optimum gas velocity for good separation process is slightly larger than that of mags peak indicating good and characteristic separation performance of fluidization. The optimum wire size was not defined exactly, but in general, a rather thick wire ( for example, 0.8 mm in diameter) is better than a small wire ( 0.1 or 0.3 mm in diamter ), contrary to the theoretical estimation where a small wire has relatively large capturing cross section normalized with the wire cross section. From the view point of technological reason, thick and hard wire or other mechanism is desirable. New devices of FHGMS with slotted steel plates (types B and C) in place of ferro-magnetic wires were also tested. Type B with horizontally slotted steel plates shows large ash reduction, however, the coal loss factor is also very large, resulting the worst separation performance among three types. Vertically slotted steel plates type C are very well with high ash reduction ratio where coal loss is as mostly small as type A. More large scale was also tested, for example, movable long steel plates were inserted and were moved to check the semi-continuous mode operation. It was found that the gas flow inside must be examined more to realize good separation performance.