Method and apparatus for processing abrasive material

DETAILED DESCRIPTION The apparatus illustrated in FIG.
1 comprises a spring roller mill 1, an air separator 2 and a mechanical raising means 5 which connects the mill discharge 3 to the separator entrance 4 and which in this case is formed by a bucket elevator.
The spring roller mill 1 and the air separator 2 each form in the apparatus according to the invention a separate constructional unit, the two constructional units being connected together.
In the apparatus illustrated in FIG.
1 a spring roller mill 1 is used which comprises an undivided annular grinding path 6 on which in known manner two diametrically opposite spring roller pairs 7 roll.
In the center of the grinding path 6 there is a material distributing cone 8 above which opens a substantially centrally disposed vertical drop tube 9 which forms substantially the mill material entry.
In the region below the grinding path 6 a discharge plate 10 rotates, preferably together with the grinding path, and supplies the comminuted material collected by a lower annular dish 11 to the discharge 3.
The roller pairs 7 are urged downwardly by spring means 70 which can comprise coil springs or hydraulic cylinders.
The spring means 70 straddle each pair of rollers and are anchored on opposite sides of the grinding path.
The spring roller mill 1 includes a housing 12 with a detachable cover 13 covering the entire mill top in which the vertical drop tube 9 is centrally mounted.
As further apparent from FIG.
1, the cover 13 comprises an eccentrically disposed air discharge conduit 14 via which used cooling air is carried off (for example to a filter not shown) which is supplied in the region beneath the outer grinding path periphery to the mill, for example via an annular member 15.
The air separator 2 is of the general type for separating two material fractions and is similar to the air separator described in U.
S.
Pat.
No.
3,901,794 and comprises a coarse material discharge constructed as tube 16 and a fine material discharge 17 from which the fine material is withdrawn as finished material (arrow 18) for example via a conveyor screw 19