The mining and minerals industry presents some of the most challenging environments for production. Mine sites, mineral processing facilities, associated stockyards, and ports facilities are large-scale and often in remote locations. The industry is a major consumer of energy and is responsible for more than 40% of total industrial energy use in this country. In sub-Saharan Africa almost 50% of energy-intensive users in South Africa are the mines.
The fundamentals of AC variable frequency speed drive technology remain, but many elements are rapidly changing towards a more sustainable and environmentally friendly mining future. Increasingly, software is embedded in today’s mine processing components, offering new functionalities and enabling the AC drive to play a larger role in the processing plant.
“Conventionally, motors run at a fixed speed, regardless of actual output requirement, wasting a tremendous amount of energy. Energy output use can be reduced by 60% by controlling motors with electrical variable speed drives,” says Stephen Brown, mining accounts and business development manager, Turkey, Middle East and Africa, for Danfoss Drives.
New motor types are appearing, placing additional demands on motor-drive control. This in turn means that the AC drive needs to be able to control an expanding variety of motor types, without burdening the end user with more complexity. In addition, new energy efficiency requirements lead to more variable speed applications.
There are AC drives designed for the needs of mining and mineral processing plants, coping with extreme conditions, heavy loads and controlling equipment installed a long distance away. No matter how well the plant design has been optimised, there is always a way to drive down costs even further. AC drives are used extensively for this purpose, extending equipment lifetime, optimising processes, reducing maintenance and saving energy costs.
All Danfoss drives greater than 90 kW incorporate a back-channel cooling design, with separate cooling paths between these two paths or the power components, control electronics and an IP54 seal. This back-channel cooling removes approximately 85-90% of the power loss directly through the heatsink, leaving only 10-15% of the total loss dissipated in the switch room.
Consideration has to be given to the outside air quality. If it is suitable, the heatsink cooling fans with appropriate mounting and ducting, and filtered external air at temperatures of up to 50°C, can be used to exhaust approximately 85-90% of the heat loss from these variable speed drives (VSD) directly outside the switch room, without affecting the switch room pressurisation. The switch room air conditioning system only needs to be sized for the remaining 10-15% of losses. Utilising this feature can dramatically reduce the air conditioning requirements of the switch rooms and provide significant project cost savings compared to VSDs without such a design feature.
In response to this need for energy efficient technology, Danfoss South Africa presented a series of informative webinars in October, geared towards mining engineers, specifiers, buyers, mining houses and investors. These interactive webinars enabled mining experts and learners to think differently about their current energy usage and how the right drives can enable energy cost savings.
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