Zurich, Switzerland ---ABB has won orders for some 18 gearless mill drives (GMDs) in the past 18 months alone as mining companies strive to meet the global surge in demand for raw materials by increasing production capacity and opening new mines. This represents a fourfold increase on ABB’s usual annual order intake.
ABB mill drives are a critical component in ore and mineral processing. GMDs are large cylindrical drums, as much as 40 feet (12 meters) in diameter, which grind mineral ore into smaller pieces for further processing. A typical 40-foot mill has a power rating of 21-26 megawatts (MW)*, a speed of 9 revolutions per minute and a grinding capacity of several thousand tons of ore per hour. (*One megawatt is equivalent to the energy produced by about 10 automobile engines.)
Energy consumed in grinding can be 50% to 70% of the total energy used to recover ore. Drives are an energy-efficient way to match mill speed to the needs of the grinding process. With no moving parts between the motor and the drum, a gearless mill is also extremely strong and can reliably process vast quantities of ore.
ABB is the world’s leading supplier of gearless mill drives with more than 70 installed and ordered units worldwide.
The most powerful GMDs in the world
ABB delivered the world’s first GMD to a Lafarge cement mill in 1969 (it is still in operation to this day) and has broken the record for the world’s largest GMDs on several occasions over the past 40 years.
Size is directly related to productivity. The larger the mill, the more ore it can grind. But with greater capacity comes increased power consumption and greater risk of disturbing the power distribution network. ABB gearless mill drives provide the huge capacity needed while keeping energy consumption low and without reducing power quality.
For larger mills the alternative technology of geared drive systems is not feasible. Even for medium size mills, where ring-geared drives are available, the GMD is the preferred solution due to its high efficiency and availability as well as its low needs for maintenance.
The current world record for a GMD (held by ABB) is 21 MW at a copper mine in Chile. ABB will extend the record to 22.5 MW in 2009 when the two 38-feet mills at a Boliden copper mine in Sweden become operational. The two GMDs will drive two new grinding mills and double production capacity to 36 million tons a year. ABB is investigating the possibility of delivering drive systems of up to 34 MW for mills as large as 44 feet.
Other recent orders and installations include three drive systems for two molybdenum mines in the United States; one 22.4-MW and two 18.6-MW GMDs for a new copper, gold and silver mine in Chile; two 17.5-MW drive systems for a platinum mine in South Africa: and a 19-MW drive system for a new gold mine in Quebec. Earlier this month (June 2008) ABB completed the commissioning of a GMD at Yanacocha, Latin America’s largest gold mine.
ABB provides the full scope of products and services for gearless mill drives, including pre-engineering, large ring motors, transformers and electrical equipment, cycloconverters, and high-performance controllers.