High efficiency grinding of blast furnace slag (vertical mill and pre-grinding)

The tube mill with dryer for blast furnace slag requires higher power consumption. Improvements in the grinding process for fine granulated slag was achieved with cement manufacturing technology such as the following:

1. The installation of vertical mill. In a vertical mill, drying, grinding, and separating/classifying of ground material are done simultaneously. The hot air used for drying is supplied with a hot wind generator. Slag contains iron grain, which could damage the rotating table and aggravate grinding efficiency. Hence, the removal of these iron grains before commencing the grinding process, using an external circulation system with a magnetic-separator device, is crucial.
2. The installation of pre-grinding equipment. A vertical mill for pre-grinding is installed in the upstream of the existing tube mill. With this, pre-grinding and finishing grinding processes are performed separately. Reduction in the size of balls used in the tube mill is expected to improve grinding efficiency.