Reducing the clinker factor without compromising quality and the rising demand for high-performance cements are great challenges for the fine grinding technology used in cement plants. As part of its green cement plant project, thyssenkrupp has expanded its product range with the polysius® booster mill. While one cement producer has already integrated the mill into an existing grinding circuit, several others have tested the mill since August 2020 and are checking results in terms of specific business cases. By Michael Wilczek and Dr Guido Kache, thyssenkrupp Industrial Solutions AG, Germany.
Some established measures are in place to reduce the clinker factor as well as increase cement quality by increasing fineness inside the existing circuit, while keeping or even increasing existing production capacity. The range of options largely depends on objectives and existing bottlenecks, but there are some obvious scenarios:
• Separator modification, either just by configuration (eg, for higher fineness), or by an upgrade/replacement (eg, for higher throughput). Advantages are the relatively low investment required and ease of implementation. Disadvantages are rather low energy efficiency, high internal mass flow (for fine grinding) and reduced plant capacity.
• Upgrade (in the case of an existing ball mill circuit) to combi-grinding with high-pressure grinding rolls (HPGR). In this case, the HPGR will be installed before the ball mill and replace the first ball mill chamber, increasing the length of the second chamber. Upsides are good energy efficiency and a high output increase. However, a high investment and long downtime are necessary, adding to a demanding installation in terms of space and tie-in.
