Cement and Energy

... CEMENT and Vol. II No. 4 October 1998 EDITORIAL BOARD R. Partha Sarathy Dr. C. Rajkumar Dr. S.P. Ghosh P.K. Tikku V.K. Arora S.V. Joshi CONTENTS • Automatic Mill Load Control (MLC) • Effective Utilisation of Gujarat and Rajasthan Lignite • Reducing Ener-gy Costs in Ball Mills • Efficiency and Reliability • NCB on Cleaner Technologies Centre's Panel • Centre to set up Bureau of Energy Efficiency • Energy Conservation Round-up • Fmthcoming Events For Private Circulation 3 4 7 10 10 II II AUTOMATIC MILL LOAD CONTROL (MLC) \ B all mills predominate as machines for grinding in the cement industry. Although these have been in use for more than one hundred years, their design and operating control is still being improved in order to reduce grinding costs. New Control Strategy M/s Holderbank Engineering, Canada (HEC) has developed a control strategy for closed circuit ball mills, which can maintain the mill production near optimum, with little operator intervention, resulting in savings in energy consumption. The main principle of the concept is that maximum production is obtained from a ball mill when the mill motor power is at a maximum and consequently the specific energy consumption is at a minimum. The maximum .power point, in turn, is dependent upon the feed material characteristics, mill liner conditions, g rinding media charge and product size requirements. Working principle Mill Load Control strategy uses traditional signals, !>Ut:h as mill sound and recirculating bucket elevator power as well as the mill power to determine the mill load level. This load level is defined as the total of the grinding charge and the material in the mill. The control strategy attempts to keep this load level as constant as possible. This load level is compared against the set ~oint derived from the mill motor power. The concept of the mill load level helps the operator to visualise what is happening inside the mill.