Danfoss Drives South Africa recently concluded a campaign of webinars, with energy efficiency as the main topic, in the mining energy and extraction sector.
According to Energy Minister, Jeff Radebe, the mining industry is a major consumer of energy and is responsible for more than 40% of the total industrial energy use. In sub-Saharan Africa, the energy-intensive users group alone consumes over 40% of electricity produced in South Africa, while just less than 50% of the energy-intensive users in South Africa are mines.
“Energy consumption patterns need to be addressed in earnest in a bid to ensure that all industries de-carbonise towards a greener and sustainable future,” said Emre Goren, regional sales director, Danfoss Drives, Turkey, Middle East and Africa. “With an ever increasing demand to increase energy supply in a globally carbon constrained environment, the mining sector needs to improve its energy efficient technologies, such as electrical variable speed drives, which could drastically reduce energy consumption.
“The recently concluded series of Danfoss ‘Energy Efficiency in Mining’ webinars, demonstrated that the fundamentals of AC variable frequency speed drive technology persist, but many elements are changing in a move towards a more sustainable and environmentally friendly mining future. Increasingly, software embedded in today’s processing components offers new functionality, which enables the AC drive to play a larger role in the processing plant.”
The content of the webinars clearly demonstrated that conventional motors run at a fixed speed, regardless of actual output requirement, wasting a tremendous amount of energy, but that energy output use can be reduced by 60% by controlling motors with electrical variable speed drives (VSDs).
New motor types are making their appearance all the time, placing additional demands on motor drive and 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.
Certain AC drives are designed for exactly the needs of mining and mineral processing plants, coping with extreme conditions, heavy loading and controlling equipment, sometimes installed a long distance away.
No matter how well the plant design is optimised, there is always a way to drive down costs even further. AC drives which are robust to extend durability are used extensively for this purpose, optimising processes, reducing maintenance and saving energy costs. The mining and minerals industry presents some of the most challenging environments for production. Mine sites, mineral processing facilities, associated stockyards and port facilities are large scale and often in remote locations.
All Danfoss drives above 90 kW incorporate a back-channel cooling design, with separate cooling paths for the power components, control electronics, and an IP54 seal between these two paths. 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, but if it is suitable, using the heatsink cooling fans and appropriate mounting and ducting, filtered external air at temperatures of up to 50°C can be used to exhaust approximately 85-90% of the heat loss from these VSDs 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, along with ongoing operational cost savings, compared to VSDs without such a design feature.
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