News Date:2016-06-16 16:36:54
In the finish grinding, clinker is mixed with gypsum and other minerals, such as blast furnace slag, according to the specifications of desired end products and are ground, or milled, to achieve required particle fineness. Finish grinding accounts for nearly 40% of the electricity use in cement production line.
Ball mills continue to be the dominating choice for finish grinding, although their share has decreased from 59% in 2000 to 49% in 2007. On the other hand,vertical roller mills (VRM) are increasingly used for finish grinding (having a share or 39% in 2007). Combined share of roller presses and horizontal rollers for finish grinding is 12% A significant reduction of the specific energy demand for cement grinding can be achieved either by combining VRMs or high pressure grinding rolls with existing ball mills or by a complete replacement of ball mills by these technologies. Saving potentials are, however, limited by the quality requirements of the final product and the specific system layout as well as auxiliary equipment installed. Whereas required grain sizes up to 4500 to 5500 Blaine can be achieved in VRM and HPGR, the resulting particle size distribution of the cement and thus cement performance can vary in the different systems raising the need for product quality control plans.
In contrast, combined grinding layouts, being the most common systems installed, set the standard for product quality and do not have to face quality problems. These multi-stage configurations are, however, more complex to operate. Their saving potentials approach to 30% with an additional 80% increase in throughput as compared to single-stage grinding in ball mills. Despite such savings, it has to be taken into account that the application of VRM and HPGR is connected to higher capital costs and requires additional maintenance efforts.
