Experience with grinding slag and clinker in a Loesche mill

In the spring of 1998 Akcansa, currently the largest cement producer in Turkey, commissioned a grinding and blending plant with a 35.2+2 Loesche mill in Karabuk a town located between Istanbul and Ankara. This produces blastfurnace cement and Portland slag cement complying with EN-197. The grinding and blending plant is linked to an appropriately sized loading plant and has a capacity of 250 000 t/a ground products and approx. 500 000 t/a blended products. The cement clinker is purchased from the cement industry, but the granulated blastfurnace slag is obtained from a neighbouring steel works. The efficiency of the grinding plant and the running behaviour of the mill are critically dependent on the formation of the grinding bed, and also on the current wear condition of the mill. The experience of three years of production operation has shown that the wear in the mill is lower than expected. The Loesche mill has a substantially lower specific power requirement than a ball mill. When compared with plant configurations in which high-pressure grinding rolls or vertical roller mills are used for preliminary grinding upstream of a ball mill it is also possible to achieve power savings of the order of 50%, when producing Portland slag cement. The Loesche mill at Akcansa has proved to be very reliable. It is relatively simple to operate and permits several modes of operation.