It is preferred to separate the coarse particles in a hydrocyclone which is positioned so as to have its axis substantially horizontal,<a href="http://www.sellercrusher.com/solutions/stone-crushing-unit.html">stone crushing unit</a> and for this separation to use a suspension having a slightly higher specific gravity than the suspension employed for separating the fine particles. This is advantageous in that the separation of the coarse particles requires but little energy. The specific gravity of separation for the coarse particles is substantially equal to the specific gravity of separation for the fine particles, since during the washing process in a hydrocyclone, the specific gravity of separation is dependent on the particle size. Consequently, if use is made of the same separating suspension, the specific gravity of separation for the fine particles will be higher.
To reduce the magnetite losses, it is important that the fraction of non-magnetics from the first magnetic separator be treated in a second magnetic separator, and that the fraction of magnetics obtained from said second magnetic separator be supplied to a thickener and the thickened fraction obtained therefrom be reused in the separation process either for separating the coarse particles or for separating the fine particles,<a href="http://www.sellercrusher.com/solutions/hammer-mill-crusher.html">hammer mill crusher</a> or for separating both the coarse and the fine particles.The magnetic losses may be reduced still further by thickening the fractions of non-magnetics from the magnetic separators in hydrocyclones, and by subjecting the fractions thus obtained to a further de-watering process, and by subsequently supplying part ofthe liquid obtained in these treatments, which liquid may contain very fine particles, to the aforementioned thickener, where the magnetics are caused to sink and the very fine nonmagnetics are caused to flow across the overflow edge.
'It is necessary of course to control the various operations in such a way that the amount of liquid and the amount of magnetics in each circuit will remain substantially constant. One of the consequences of this condition is that the liquid with which the coarse specifically heavy particles are first sprayed oii should be obtained from the fraction of specifically heavy non-magnetics, and that the liquid with which the coarse specifically light particles are first sprayed off should be obtained from the fraction of specifically light non-magnetics.