Siemens Drive Technologies Division has developed a new drive system for a cement mill, part of a joint project with Gebr. Pfeiffer SE.
Siemens will supply six drive modules. With an overall power rating of 11,500 kW and producing 450 metric tons of cement per hour, the vertical mill is the most powerful of its kind in the world today. The mill will be operated by the Brazilian cement producer Holcim, which will commission the plant as part of a project to expand the capacity of its Barroso works in the Brazilian state of Minas Gerais.
The modular and redundant drive system consists of six identical 1920 kW drive modules that drive the grinding table of the cement mill. Siemens is also supplying all components of the drive train: gear unit, coupling and oil supply system, as well as electric motors and frequency converters. An advantage of this concept is that the drive units are mounted on carriages, thus enabling them to be replaced quickly whenever maintenance is required and ensuring the fastest possible resumption of mill operation.
The radial arrangement of the drive units around the grinding table bearings protects the drives against grinding forces. The frequency converter allows variable speed adjustment and thus flexible adaptation of the milling process to suit the requirements of different input materials. This makes it possible to optimise, for example, throughput or energy efficiency.
With this system configuration, even higher-output drive modules can be installed for an overall power rating of up to 16,500 kW. Up till now, the mechanical engineering limit attainable by conventional plants was only 8000 kW.
"The multi-drive solution developed by Siemens is another example of how we can offer significant benefits to our customers by combining innovative mechanical drive components with suitable electronic drive systems to create an integrated drive system,” said Dr. Bernhard Hoffmann, head of drive applications at Siemens' Mechanical Drives Business Unit.
“Thanks to the modular design of the drive train, a system can deliver previously unattainable performance ratings and offer significantly more energy efficiency and availability."