In the last four years, a further 100 mills were sold.
At this time the cement industry also wanted to produce cement with the help of roller comminution which required less energy. And even though the entire cement manufacturing process was being constantly optimised, the energy-intensive clinker brick grinding process had long since been ruled out.
The reason: The requirement for the high fineness of particles led to a dust/air mixture in the vertical roller mill, which made the grinding bed formation in the rollers difficult. For this reason, in conventional plants, each roller had to not only provide the actual communition but also the preparation of the internal grinding beds using pre de-aeration and precompaction. This caused the mill to vibrate significantly due to inadequate grinding bed formation, causing disrupted mill operation and unreliable variations in the fineness of the particles, so that the high quality requirements of the end product could not be adhered to.
With the M+S technology developed by Loesche, these mills separate the preparation and grinding stages of the process and establish an entirely new grinding-roller concept. Technically, a corresponding number of preparation or support rollers (S) are implemented in the grinding or master rollers (M), that take over the grinding bed preparation (the 2+2, 3+3 or 4+4 technology depending on the throughput). As a result, the specific properties of the very fine material can be reliably controlled. With this invention, Loesche has, for decades, been in the position to replace conventional grinding technology in the cement industry with vertical air-swept grinding mills. This technology is also used in the grinding of steel slag.
The 2+2, 3+3 and 4+4 technology in the M+S system offers a great range of advantages in comparison with conventional grinding systems:
variable grinding pressure while the grinding plant is running and thus is quickly able to adapt to grinding material changes
very low differential speed between the grinding track and the conical, friction-driven roller
lower specific wear during pulverization
compact construction due to the combination of the crushing, grinding, sorting, drying and classification process stages
noticable energy saving in comparison to alternative/conventional grinding systems
Further advantages result from the grinding of blast furnace slag:
avoidance of ineffective product overgrinding
The fact that the development of the vertical roller mill from the Loesche LM-CS series has still not reached its end after such a long time is today proven by one of the largest cement mills in Hub/Pakistan, with a grinding track diameter of 7.2 m.
The Loesche mill type LM 72.4+4 CS with a drive power of 10000 kW has been sold for an OPC capacity of 445 t/h and a CEM II capacity (with 10 % limestone) of 485 t/h at 3400 Blaine. On the grinding track, four support and four rollers cater for the projected capacity.