New grinding process Horomill0 pages

A New Grinding Process

A. CORDONNIER FCB , >
CRCM C entre de R echerches C imenterie et M inΩralurgie Lille, France Abstract: FCB has just developed a new mill, HOROMILL, for grinding cement , raw meal and minerals. This new grinding process is designed for finish grinding and also for pregrinding. The energy saving is similar as roll press, roughly 30% to 50% in respect to the ball mill, but with a moderate circulating load and grinding pressure. After a research phase on a 1 t/h pilot plant, a first 25 t/h industrial plant was achieved in co-operation with Fratelli Buzzi at Trino, Italy. The performances and the cement quality, strength and workability, were checked on this industrial size. 1. Historical account on HOROMILL >
ή The development of the roll presses in pregrinding has shown the interest of compression grinding from the power consumption point of view with respect to the ball mill. The FCB Research Centre has carried out many works in this domain and has particularly studied the interest of this process in finish grinding. The results of these researches conducted on a pilot plant with a throughput of one tonne per hour can be summarised as follows : For reasons related to the nip dynamics, the grinding speed is limited. Close to this maximum speed, vibration problems are frequent. Օ The substitution ratio increases with the fineness roughly proportionally to the square root of the Blaine value ; on the other hand, the nip becomes more difficult and less stable and the circulating load increases proportionally to the fineness. It must be noted that the increase of the circulating load is accompanied by an important modification of the finished product size distribution curve. The grinding pressure is high so as to perform a maximum grinding work in only one pass and limit the circulating load, but does not always correspond to the optimal value. In general, grinding efficiency increases with pressure reduction (cements with limestone or pozzolana addition, cement raw mix). Furthermore, the use of high pressures causes lifetime and reliability problems. Օ The compression grinding process leads to specific energy values markedly lower than those obtained in a ball mill, even under optimal conditions. The substitution ratios (ratio of the specific energy required by the ball mill to that required by the roll press at the same fineness) vary between 1.4 and 1.8 for cement. These figures obtained by means of the FCB-Index correspond to grinding energy values of ball mills under optimal conditions and therefore are minimum values. For industrial plants, the substitution ratios would rather be in the order of 1.6 - 2.0 in average, under assumption of an average efficiency of 0.9 with respect to the FCB-Index. FCB >
CRCM 8th European Symposium on Comminution , Stockholm, Sweden, May 1994 page 1 size="-4">