Cement, Energy and Environment July-Sep 2002

r the same time, the rollers are set above it to produce the grinding action. If the friction between the rollers and the clinker on the table is weakened, the roller slips and vibration occurs, resulting in a fal l in the grindin g performance. Hence, preventing roller slippage is of paramount importance for maintaining stab le operation and increased capacity; this is achieved by adding grooves to the spherical rollers. The g rooved spherical rollers used in the VRPM improve performance and efficiency by trapping the clinker in the grooves and rotating in perfect synchrony with the table , thus reducing vibrat ion and enab ling stable operation. Umform g:·inding As spherical rollers have a higher periphery, a wider and uniform g rindin g layer is formed; thi s increases the grinding efficiency. Coping with quality and quantity fluctuations - Fluctuations in clinker quali ty and feed rate can easily be accommodated. Versat ility Seve ral configurations using VRPMs arc possible, such as open-circuit mill, c losed-ci rcuit mill and the pre– grinding mill feeding more than one ball mill. In fact, VRPM can sui t even customers with little extra space since the VRPM is very compact. Experience in India The first VRPM (Model 230- 3 11 00 kW) was installed at ACC– Chanda Cement Works, where the ball mill outp ut (open circuit) has increased by approximately 65 per cent and power consumpt ion Table 1 reduced by approximate ly 17 per cent. Th is mill has been operating satisfactori ly for the last four years. A second VRPM (Model 230 1200 kW) was insta lled at ACC Kymore, for feed ing two cement mill s grindi ng portland pozzolana cement. Th is mill too has been operati ng satisfactorily for the last two years. The actua l resu lts are reported in Tab le I. /\long with the installation of the VRPM, the ba ll mil ls were converted to closed– circuit from open-c ircuit. and the pneumatic con vey ing system changed to mechanical. The output of th e cemen t mi lls has s ince increased by 80 per cent and the power consumption reduced by approximately 20 per cent, a major part of which both is attributable to the installation of VRPM. lmprovemcnt in performance of grinding of portland pozzolana cement after installation of a common VRPM for two cement mills Equipment Running kW Before installing VRPM After insta lling VRPM VRPM- Main - 950.00 Auxi Iiaries - 70 .00 CM# 1 - Main 1550.00 1435 .00 CM # - Aux 320.00 298 .00 CM # 8-Main 1550.00 1475 .00 CM # -8 Aux 330.00 320.00 Fly ash handling 240.00 332.00 Total kW 3990.00 4880.00 Total mill output, tph 112.00 200.00 Specific power consumption 35.63* 24.40* kWh/t *Note : Before installation of VRPM the cement mills were open-circuit with pneumatic conveying syste111. These were then changed to closed-circuit and mechanical conveying One more VRPM (Model 230- 3 1200 k W) for Madras Cements Ltd, R R Nagar was successfully commiss ioned approximately a year ago. Others under various stages of installation are : (i) One number (Model 180-3 750 kW) for the Rai Barelli Cement Grinding Unit of Birla Corporation Ltd (ii )Two numbers (Model 230-3 1200 k W) for Mai har and Century Cement.