Existing mill capacity doubled developments in grinding process

The tube mill is still the most common machine in the cement industry for grinding clinker. Large scale production upgrades of tube mills have been available since 1990, when the roller press has been set up for semi-finish-grinding. The major reasons for upgradings are: production increase, lower energy consumption and the market demand for higher cement qualities. All three arguments should be fulfilled for the cement mill conversion, introduced in the paper. A pregrinding circuit, consisting of a roller press and a separator has been selected, to more than double the capacity of the existing tube mill. While this project was one of the first of its nature, a number of problems have been encountered. Finally, a second upgrading step had to follow the first one, partly replacing major equipment. A new process, even new machines have been introduced, giving satisfactory results. Finally, it has become a new standard for todays applications. The project introduced is an example for a number of grinding plants that still need the second step of upgrade.