Modelling cement grinding in high pressure grinding rolls

摘要

The modelling of comminution in high pressure grinding rolls has been a focal point for research and development for 30 years. In contrast to minerals processing, on which the majority of investigations have concentrated, the treatment of cement grinding has to include detailed consideration of the sub-processes of de-aeration and compaction in the roller gap because of the great fineness of the feed material. These two sub-processes have a great influence on plant throughput and process stability. For example, high feed finenesses in conjunction with high roll speeds lead to de-aeration problems in the roll gap, which can lead e.g. to strong torque oscillations (chattering) or even negative torque (gear backlash).This article first provides an overview of the underlying theoretical principles and then indicates approaches to solving the modelling of the individual processes on the basis of trials with a piston-die press and a laboratory roller mill. For this purpose, eight cement clinkers were investigated under the aspects of stressing velocity, grinding pressure and shape of the particle size distribution. The test parameters were selected in order to cover the spectrum of industrial application over a wide range.