High-quality cement manufacturer and supplier United Cement Company (Unisem), of Nigeria, is using two vertical roller mills (VRMs) from export-orientated engineering company Loesche at its successfully commissioned new Cement Plant 2 at Mfamosing, in Cross River state, Nigeria.
Loesche received the order for two VRMs of the LM 60.4 type for grinding cement raw material and the LM 70.4+4 CS type, the biggest Loesche VRM, for grinding cement clinker.
The cement plant at Mfamosing, located 30 km north-east of Calabar, the capital of Cross River state, Nigeria, has been fully operational since February 2009 and is equipped with the latest technology. With a capacity of 2.5-million tons of cement a year, the Unicem plant has now been extended by this Loesche technology.
The type LM 60.4 mill for the grinding of cement raw material boasts a production rate of 500 t/h.
Mill LM 70.4+4 CS type is designed for a capacity of more than 370 t/h. In combination with this enormous capacity, a new drive, with system operating power of up to 8 800 kW, was necessary. Close cooperation between manufacturers of propulsion components and test systems RENK Augsburg and Loesche Düsseldorf, saw this development take place. Input from the end-user, global building materials and solutions company LafargeHolcim, as well as from a renowned technical university in Germany, was taken into consideration.
The innovative result of this combined input and effort is the Compact Planetary Electrical (COPE) drive. The new concept is designed for gearboxes of 4 000 kW to 12 000 kW. This results in a single and special motor, as well as the attendant risks, becoming obsolete. Further, it eliminates the failure in the fast running first-stage gear of conventional gearboxes.
Another advantage of this mill is that it has the same footprint as a standard mill gearbox for VRMs. Further, this presents the first time eight drive motors for a VRM gearbox have been used, as well as the first time multiple drives in VRMs have operated with or without variable-frequency drive.
Other benefits include the easy removal of individual mill motor units to minimise downtimes by about two hours; and an extremely compact design with motors directly attached to the gearbox housing.
Loesche points to the most important difference of this development being the fact that long standstills of months in duration to repair the mill’s conventional gearboxes, will be a matter of the past. Implementing the COPE drive requires the standard foundation. The replacement of one of the eight small motors is easily done as they are readily available and easy to install.