GB687026A - Improvements in or relating to pulverisers - Google Patents

Abstract

687,026. Ball-and-ring mills. BABCOCK & WILCOX, Ltd. Oct. 31, 1950 [Nov. 1, 1949], No. 26552/50. Class 59 A pulverizer comprising a rotary grinding ring 18, a circular row of grinding balls 20 rolling on this ring, a non-rotary upper grinding ring 21 supported on the balls, and an annular passage 42 for directing a stream of gaseous fluid upwardly around the outer side of the row of balls in order to sweep the pulverized material away from the latter, has the upper grinding ring so formed that oversize particles are able to return to the grinding zone by downward movement over major portions of the upper outer quadrants of the balls. As shown, the ring 18 is carried by a yoke 17 mounted on a driven shaft 14. An upstanding ledge 40 on the ring 18 is of sufficient height to maintain the desired bed of material in the grinding track. The upper ring 21 is pressed on to the balls by four springs 25 attached between the ring and adjustable bolts 27 mounted in the top plate 29 of the housing 10. The shape and arrangement of the ring 20 is such that it leaves substantially the whole of the upper outer quadrants of the balls uncovered so as to permit the recirculation of over-size particles to the grinding zone. The pulverized material is removed from the grinding zone by a gaseous medium which is forced into a wind box 37 and passes therefrom to the lower edge of the ring 18 through openings which are provided in the housing 10 and have vanes 38 whereby the gas stream is given a swirling motion. The stream then passes upwardly through an outwardly-inclined annular orifice 42 formed by plates 43, 44, 45, 48, Fig. 3, secured to the ring 18 and housing, and the pulverized material flowing over the plate 45 is carried upwardly in suspension to a classifier 60. Blades 66 project inwardly from the housing 10 and slope upwardly in the direction of rotation of the ring 18 for the purpose of deflecting the larger oversize particles back into the grinding zone. Small particles of unpulverizable material drop through the orifice 42 into a trap 51 controlled by a slidable gate 50, and large pieces of such material are discharged through a counterweighted relief gate 68 pivoted in one wall of the orifice. The classifier 60, which is carried on the yoke 17 so as to rotate therewith, has outlets 65 and Z-shaped deflectors 61 for returning over-size particles to the grinding zone. Specifications 523,753 and 646,686 are referred to.