GB401115A - Improvements in pulverizing mills - Google Patents

Abstract

401,115. Ball-and-ring mills. BABCOCK & WILCOX, Ltd., Babcock House, Farringdon Street, London. Nov. 16, 1932, No. 32449. Convention date, Nov. 16, 1931. [Class 59.] In a pulverizing-mill the sifting air current passes to the inside of the lower row of balls and then divides into streams which pass between the balls 13 and through orifices 14a in the rotating ring to the outside of the upper rows of balls and through a screen 43 past the inner row of the upper rows of balls. As shown a ring 14, perforated with air passages 14a and fixed to a rotary shaft 16, drives a lower row of balls 13 on a stationary track 12 and two upper rows of balls 17, 18 retained by independent non- rotary tracks 19, 20, the track 19 being pressed downwardly by springs 21 and the track 20 by springs 22. A conical shelf 42 extends from the side 10 of the mill to the top of the track 19, the free edge being adjustable to vary the space for the passage of air and fines to the outlet 26. The outlet 26 is provided with an adjustable extension, flanged inwardly at the end and extending into an open-ended cone 44 in which coarse material is deposited and returned to the row of balls 18. Material to be ground enters the mill through an inlet 11 and passes to the balls 18 and after being partly ground proceeds to the balls 17. The track of the balls 17 is higher than that of the balls 18 so that coarse material tends to remain in the track 18. According to the material to be pulverized the flow may be accelerated by reducing, omitting or reversing the elevation of the outer track of the balls 17. An annular adjustable baffle 24 surrounds the balls 17 and the material passes this baffle and falls to the lower ring of balls 13. Air which may be heated is drawn into the mill through an orifice 25 and through passages 25c to the inside of the balls 13 where it divides into two streams, one passing through the balls to the outside of the baffle 24 and the other passing outwardly through the gaps 14a and through a bar screen 43. The air passing outside the baffle 24 carries the fines between the cone 42 and track ring 19 to the inside of the cone 44 and thence to the outlet 26. The coarse material which does not pass the screen 43 returns to the lower row of balls 13. The air carries the ground material to a pair of cyclone separators, the residual materials being discharged by a fan to a second pair of separators.