Evaluating water supply control at a centralised hydro-powered mine

Abstract

Deep-level mines face economic challenges which comprise reducing operating costs while increasing production. Hydro-powered mining was developed as an alternative mining method to conventional pneumatically-powered mining due to the inefficient energy usage of pneumatic systems. Hydro-powered mining technology offers the benefit of relying largely on water for mining activities, presenting opportunities for improved energy efficiency. Various optimisation solutions have been implemented on water systems of pneumatically-powered mines. These solutions were aimed at reductions in operating costs due to the energy consumption of water systems; however, no literature was found on the implementation of these solutions on a centralised hydro-powered mine. The first step taken in optimising a mine water system is controlling the water supply which allows for the optimisation of further water systems. The existing method of water-supply control is valve control. The applicability of proven valve-control methods must be examined on a centralised hydro-powered mine due to the lack of research available on hydro-powered mine. The main objective of this study is to evaluate how valve control can be used on a centralised hydro-powered mine, as well as to determine the impact of this solution. To this end, a manual test of valve operation was performed on an implementation site. The test illustrated that existing valve control methods cannot be implemented in the same manner on a centralised hydro-powered mine. Additional control over valves supplying water to mining levels is required. The magnitude of water-supply pressure requires dynamic control while charging the supply line. This entails incremental opening of the valve, which cannot remain in an intermediate open position. Closing the valve does not compromise system-supply properties either upstream or downstream of the control location. A controlled daily water supply on-site reduced the daily average flow supply by 27 L/s, which comprises 9.89% of the mine’s average supply. There was a reduction in the energy consumption of pumping operations due to the decrease in daily water usage; however, refrigeration systems were not affected. The cost-saving impact of the solution related to reduced energy consumption is an estimated R7.35 million per annum. The reduction in energy consumption on the mine due to the controlled water supply resulted in a 1.35% decrease of the mine’s monthly energy intensity. Both the cost and energy reductions seen on the mine do not make the site a competitive model when compared to a pneumatically-powered mine. The study objective was met through the investigation of valve operation and consequent implementation of WSO. The solution impacted the mine’s energy efficiency as anticipated.