The newly developed MVR mill has the following main components (Fig.1):

• 4 to 6 grinding rollers with a cylindrical wear part geometry
• flat grinding table , with its outer diameter in mm appearing in the name of the mill
• housing for gas conveying, with nozzle ring and classifier
• new modular drive unit “MultiDrive” or alternatively conventional drive with planetary gear

A roller module consists of the roller with cylindrical roller tire, roller axle, roller arm, bearing stand, and transmission of hydraulic force. Due to this type of roller suspension in combination with the flat grinding table geometry, the grinding gap between the rollers and table remains parallel which in case of rollers guided motion ensures smooth run and has a positive effect on transmission of energy onto the grinding bed. Adjacent roller modules sit two by two on so-called twin supports that connect them to the foundation. This concept provides more space between the supports for better access and plant layout with regard to the arrangement of hot gas ductings, external material recirculation, and ancillaries. The machine parts which are relevant in terms of flow technology, such as hot gas channel, nozzle ring, SLS high-efficiency classifier, and central material feed, have the same design as the parts that have proven successful in the Pfeiffer MPS mills.
For repair purposes, the roller modules can be swung out separately with the same hydraulic system used in operation for producing the grinding force. In case a drive with planetary gear is provided, production may be continued at reduced capacity after having swung out/lifted two opposite rollers. With the MultiDrive and its several drive modules, operation may continue with only one roller lifted/swung out. Prior to restarting the mill after having swung out one roller, only this roller needs to be secured mechanically for safety reasons and the housing has to be closed.
With the new MultiDrive, there are up to six identical drive modules with roughly 2,000 kW each, driving the grinding table via a girth gear. Each module consists of an electric motor, coupling, and bevel spur gear arranged on a base frame with slide rails (Fig. 2). Load distribution of the individual electric motors is performed by controlling the frequency converter provided for each drive module. As a result the grinding table speed can be adapted as a parameter for process optimization.
The grinding forces are transmitted from the grinding bed via a conventional sliding bearing into the foundation without causing a load on the bevel spur gearboxes. In case of an outage of a drive module, this can be disengaged and the MVR mill may continue to run, however, with a reduced throughput.
Thanks to the active redundancy concept, the Pfeiffer roller mill MVR with MultiDrive is in a position to maintain production even when problems occur both on the rollers and drive. Moreover, only a total of 5 roller modules and 3 drive units are used for the entire series of mills up to 12,000 kW drive power, relying upon individual components that have proven successful in operation. This ensures a significant improvement of spare parts keeping, especially as far as complex components with long delivery times are concerned, such as roller bearings and gear parts.

At the Pfeiffer test station, extensive test series with the mill type MVR 400 were run for the grinding of cement raw material, cement clinker, granulated blast-furnace slag, and other additives to determine the basic rating data (Fig. 3). So we now have a pilot plant with an operation which is close to that of industrial plants and can be used for the determination of raw material characteristics and project-related data, i.e. specific power consumption, gas volume requirements, specific wear rate and the like. For each test, we need the related components to prepare 1 ton of test material.
Since the year 2008, a grinding plant located in southwestern Germany with an MVR 1800 (Fig. 4) has been producing about 15 t/h of binder with a cement clinker portion of about 60% and a specific surface of up to 6,000 cm2/g Blaine.
Since 2009, an MVR-R 3750 with a 1,600 kW installed power (Fig. 5) has been operating in the cement works Lukavac in Bosnia-Herzegovina for the combined grinding and drying of cement raw material. Depending on the raw material, throughput varies between 130 and 170 t/h. For the operating time run so far, which is 6,000 hours, specific wear measured on the wear parts of the grinding table and grinding rollers reached a total 1.3 g/t.
In the Holcim owned grinding plant in Val de Seine/France (Fig. 6), a MultiDrive with 3 modules of 1,450 kW each has been operating since 2009 on a Pfeiffer vertical roller mill of the type MPS 4750 BC which produces 120 t/h of CEM I 52.5 and 130 t/h, respectively, of granulated blast-furnace slag with a specific surface of 5,000 cm2/g Blaine.
A cement mill of the type MVR 5600 C-4 with 4 rollers (Fig. 7) to be installed in Balaji/India is at the order processing stage at Gebr. Pfeiffer SE. The guaranteed throughput is 310 t/h for Portland cement with a specific surface of 3,000 cm2/g Blaine and 320 t/h for a cement with a 30% fly ash portion, with a specific surface of 3,500 cm2/g Blaine. The guaranteed specific power consumption at the counters for mill, classifier, and mill fan is a total 30.9 kWh/t for fly ash cement production.
This mill will be driven by a 6,600 kW MultiDrive with 4 modules of 1,650 kW each, with frequency converters. The weight of one module comprising motor, coupling, gearbox, and base frame is 22 tons which is much less than the weight of a comparable conventional planetary gear. To be noted that the drive modules in the above mentioned Holcim works in France and the works to be set up in Balaji are identical, reflecting the aim of standardization which is a practical advantage of the modular design of this drive concept.
Gebr. Pfeiffer SE will supply the machinery for the Balaji plant, starting from the feed metering system and ending with finished product handling. Delivery is scheduled for autumn 2010, with commissioning to be carried out in the first half of 2011.