THE LOESCHE MILL FOR COMMINUTION OF CEMENT CLINKER AND INTERGROUND ADDITIVES IN PRACTICAL OPERATION

The Loesche mill has proved to be a grinding system with high levels of efficiency and availability and a significantly lower energy consumption than tube mill systems for grinding coal, limestone and cement raw material Until now not all the quality features of a tube mill cement have been achieved when finish-grinding cement in roller grinding mills. Cement grinding trials with modified raw meal roller grinding mills with four rollers have led to a new design concept of the Loesche mill for cement. While retaining the familiar horizontal grinding track. the Loesche cement mills have 4 conical rollers of which, however 2 work as grinding rollers and 2 as so-called preparation rollers for pre-compacting the grinding bed. This has meant that the specific grinding pressures of the grinding rollers can be greatly increased. A single-stage comminution of clinker and interground additives takes place at high grinding speeds in the parallel gap between the grinding elements with internal recirculation of coarse material. These simple design measures mean that the required cement quality can be achieved with low-vibration mill operation. A closed mill building is not necessary. Service lives of the grinding elements of more than 10000 hours ensure a uniform product quality with high mill availability The simple plant arrangement allows a simple control concept to be used. In recent years Loesche 4-roller mills for grinding clinker and granulated blast furnace slags in several works have been optimized and throughput capacities of up to 140 t/h have been a chieved with tube mill cement quality of 3400 Blaine. The specific energy consumption lies significantly below that of tube mills and is also better than with a plant with a tube mill preceded by high-pressure grinding rolls.