GB837131A - Improvements relating to pulverising plant and an improved method of pulverising solid material - Google Patents

Abstract

837,131. Pulverizing plant. BABCOCK & WILCOX Ltd. July 29, 1958 [Aug. 1, 1957], No. 24394/57. Class 59 Pulverizing plant having a plurality of pulverizing mills of the kind including a rotary casing containing a charge of free pulverizing elements, a common power device with a power output suitable for driving the mill casings at speeds within intermediate parts of their speed ranges in which the driving power decreases with increase in speed but insufficient simultaneously to drive the casings at the lowest speeds in the said speed ranges and coupling means between the power device and the casings enabling the speeds of the casings to be separately varied and enabling the power device to raise the speed of the casing of one mill to or near the highest value in its said speed range while the casing of a second mill is stationary or driven at a low speed and then, while the power device continues to rotate the casing of the first mill at that speed to raise the speed of the casing of the second mill to a speed within its said speed range. The plant shown in Fig. 1 comprises two similar tube mills I, II each having a casing 3 provided with a gear wheel 11 engaging a pinion 13. Driving means for the two mills comprise a double ended induction type electric motor 55 having two output shafts 57, 58. Output shaft 57 is connected to the driving shaft 59 of a pump unit 61 which is connected to a motor unit 83 the output shaft 87 of which carries the pinion 13 of mill I. The output shaft 58 is connected by a similar hydraulic transmission drive comprising a pump unit 235 and a motor unit 237 arranged to drive the pinion 13 associated with mill II. The pump and motor units are similar to those described in Specification 832,404. Each mill incorporates a speed control unit 111 similar to that described in Specification 832,404. With the arrangement shown in Fig. 1, the motor 55 need have a power output only as large as the sum of the powers consumed by the two mills running simultaneously at their desired operating speeds on the negative slope of their torque/speed curves.