New grinding process Horomill
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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">

Reflections and investigations were initiated to find another grinding process based on compression in order to keep the energy performance of this process, while grinding the material in several steps to prevent a too high circulating load and grinding pressure. The principle of a cylindrical shell driven in rotation on its horizontal axis, and one or several idle rolls seemed to be a possible solution. The point that seemed to be most difficult, was the control of the material circulation for which centrifugal force had to play an important role. The construction of a 1 t/h pilot plant...

3. A new grinding process HOROMILL is essentially designed for integral grinding in conjunction with the TSV Classifier, but can be quite integrated to a grinding circuit including a ball mill. In order to develop and assess the performance of this new process, the pilot plant of the FCB Research Centre was arranged to operate with the roll press or with HOROMILLή. The pilot HOROMILL has the following technical data : Ε installed power : 45 kW shell diameter : 800 mm Օ separation circuit capacity up to 20 t/h finished product capacity up to 2.5 t/h Օ possibility of varying the grinding...

Circulating Load = 8.7 Sieve passing in % Circulating Load = 10 10 100 1 10 յ100 CRCM 8th European Symposium on Comminution , Stockholm, Sweden, May 1994 > page 5 size="-2">

4. The first industrial achievement > 4.1 The first HOROMILL grinding plant The first industrial plant was performed in co-operation with Fratelli Buzzi in the Plant of Trino, Italy. A financial aid from the EEC as part of the Thermie Programme made this achievement easier. The design and construction of this new plant began in August 1992 and the mill start up took place on the 10 September 1993. The main features of the grinding plant are as follows : Ε HOROMILL : ΢ȗ Installed power : 600 kW at variable speed ∗ Diameter : 2200 mm Circuit : բȗ nominal rate in CP42.5R production : 25 t/h at...

The first production results achieved in the manufacture of Portland Cement CP42.5R are : 3200 Blaine fineness (selected identical to the present production in ball mill) Օ finished product throughput : 25 t/h motor shaft power : 400 kW i.e. 16 kWh/t the corresponding substitution ratio with respect to the FCB-Index is 1.55, but exceeds 2.0 with respect to the existing open circuit ball mill (~ 31 kWh/t motor shaft power). The quality of the produced cements has been tested and compared with that obtained in ball mill : Օ concrete workabilities are equivalent. mortar and concrete strengths...

With respect to the roll press : designed for integral grinding ; regular operation, no vibration. Օ circulating load is smaller, and adjustable depending on the production and quality objectives. the moderate grinding pressure ensures a long lifetime of the wear parts and mechanical reliability, but also leads to a better efficiency for cements with additive. 6. Conclusions A new grinding process, the HOROPROCESS, has entered into industrial production in the Fratelli Buzzi cement works at Trino, Italy. The first results achieved in cement CP42.5R are very encouraging and allow to expect...