A control system for the efficient operation of Bulk Air Coolers on a mine

Abstract

The mining sector is a vital contributor to the economy of South Africa. This sector, however, consumes 15% of the country's electrical energy. Deep mine operations require ventilation and cooling (VC) systems, which can account for up to 25% of the mine's electricity cost. Refrigeration systems provide the cold water and air needed by the VC systems to mine at depths of over 2 km. Electricity cost savings on these refrigeration systems can be achieved by using time-dependent operating schedules. Peak-time electricity usage especially needs to be minimised to maximise these cost savings. The focus of this study was the development of a Bulk Air Cooler (BAC) controller, due to the lack of a controller to regulate these systems in the mining industry. This controller enables equipment to adapt dynamically to environmental changes by monitoring the underground temperature and adhering to input boundaries. The BAC controller was implemented on two sites, to control pumps, chillers and fans. A combined daily peak-time usage reduction of 4.3 MW was achieved on the two sites. This translates to an annual cost saving of R831 973. There is also a clear need to reduce electricity usage during the Eskom peak period. The BAC controller was therefore designed to monitor and control mine refrigeration machines. Equipment can thus be switched off during peak periods, provided the environmental parameters comply with safety regulations.