Cement and Energy

Ball mi II operation requires minimum wear, highest shape stability, and breakage resistance, which together act as the scale to control the quality of grinding media over a long period of time. There are three major indicators for the qua'lity of grinding media : the cast material and its chemical composition, the production process (moulding technology, melting technology or Area of gat· ings. and 1 rises Place with lower c structure density has a lower microchardness :(.:···::::\:':·. ·· •. ··;...- Figure 2 Different reasons for deformation ofgrinding halls gatin g and rising technology) and thirdly the quality assurance which achi eves a constant level. The optimum grinding media material at minimum wear rate and high breakage resistance is defined by a high number of small homogenously distributed complex chromium carbide of complex hardness in a martensitic matrix of high strength and e lastici ty. Deformation of grinding media is due to the microstructure which is not homogeneous over the cross section (Figure 2). An unhomogeneous cross section can be identi tied by differences in hardness as well as the Cmmesy: lnlernational Cement Review -June 1998 different sizes of material crystals. Deformation could be caused by areas of gating and rising or differep.ces in hardness throughout the grinding balls. Recent examples show that there is tremendous potential for energy savings in ball mills (Figure 3). Drastic ·energy savings make it possible to finance new mill internals within one to two years. Energy costs should not, however, be the only thing taken into consideration but also the increase in production rate, as well as a reduction of operating times of the grinding plant at a constant production rate. Figure 3 Potential of optimisation ofenergy consumption and production in grinding system with ball mills. 6