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Optimising energy recovery in mine dewatering systems

Mines in South Africa face many challenges, chief among these are rising production costs. One of the main reasons for the inflated costs is a rise in energy costs. Mines are, therefore, continuously looking for innovative ways to reduce energy usage, especially during peak tariff periods. Hydraulic energy recovery devices such as turbine pumps and three-chamber pipe feeder systems, are often used to save energy. These devices use chilled water required for mining activities and underground cooling to aid in the resulting dewatering process. Previous studies investigated the optimal integration of energy recovery devices into dewatering systems. However, these studies overlooked certain difficulties associated with controlling these systems. It was also found that certain technologies used in older studies were outdated. A strategy was, therefore, developed to optimally integrate modern energy recovery devices into existing dewatering systems. Before being implemented, the strategy was modelled using integrated dynamic simulation software. On a practical case study, a load of 1.5 MW could be shifted from the Eskom evening peak and 2.5 MW from the morning peak. For this case study, the potential energy cost savings in the dewatering system resulting from these initiatives was R1.7 million p.a. The new strategy proved to be successful when all equipment was available, and posed as a practical solution to save energy cost in mine dewatering systems.