Improvements in or relating to producing solid particles for heavy separation media

摘要

A method for producing solid particles, e.g. of Fe/Si for use in mineral separation, includes the steps of spraying molten material from its melt into discrete solid particles separating a coarse and a fine fraction of the solid particles; comminuting particles of the separated coarse fraction into particles substantially smaller than the average size of the particles in the separated fine fraction; flame spheroidizing at least part of the comminuted particles by passing them through a high temperature flame to melt them at least at their surfaces and allowing the particles to pass from the flame into a cooling zone; and mixing flame spheroidized particles in predetermined proportion with the separated fine fraction of the sprayed particles. The Fe/Si may comprise 8-23% Si and up to 10% Cu, e.g. 14-16% Si and up to 3% Cu. As shown in Fig. 1, molten Fe/Si is atomized at 1 and screened at 2. The coarse fraction is comminuted in a ball or other mill 3, flame spheroidized at 4 and then mixed in suitable proportion, e.g. between 40% and 85% by weight of the flame spheroidized particles, with the fines from the screen. The spraying is illustrated in Fig. 3. Molten Fe/Si from a tundish 5 falls through a central passage 8 and is disintegrated by conical jets of water A, B, C issuing from nozzles 9, 10, 11 at successively increased speeds. The water temperature may be controlled. Four or more jets may be used, at least one of the jets may be of gas, e.g. N2, and at least one may be of a liquid-gas mixture. The flame spheroidizing is illustrated in Fig. 4. Irregularly shaped Fe/Si particles and heated air are fed to an inner tube 32. Fuel gas is fed tangentially at 39 to a surrounding chamber 40. Cooling water is fed to the nozzle at 50 and a surrounding sheath of reducing gas is supplied at 47. The spheroidal particles fall into a cooling chamber 51 having a curtain of cooling medium directed down its inner periphery 53 from an annular inlet 52. Cooling of spheroidized particles may be as described in Specification 842,284.