Applying a benchmark method to identify utility cost-saving opportunities on a platinum mine
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South Africa’s energy and water demands are more significant than the supply thereof. This higher demand means Eskom cannot deliver enough power to South Africa. Furthermore, South Africa is a water-scarce country and water is a non-renewable resource that should be used wisely. Eskom built the Medupi power station to increase its supply. The construction cost of this power station was very high in comparison with previous power stations. High tariff increases were implemented to maintain the construction of the power station. Between 2008 and 2018, a total accumulative tariff increase of three times above inflation was implemented. As South African mines are the largest consumers of energy, these high tariff increases affected them the most and threatened their profitability. South African mines play an essential role in the economy. The reason being is that if the mines have an increase profits, more taxes are payable to the South African Revenue Services. Therefore, if the mines struggle, the economy will also start to struggle. Mines have various high energy consumers with motors up to 15 MW. By lowering its energy consumption, more profits can be made with high energy costs. Benchmarking mines can indicate where there is potential for lowering water and energy consumption. Few studies have discussed energy benchmarking on deep-level mining. No studies were found regarding the benchmarking of potable water on deep-level mining. However, there were studies that evaluated compressed air benchmarking on deep-level platinum mines. The objective of this study was to create these benchmarks on a specific platinum mine. From these benchmarks, energy and water savings opportunities were identified. For the opportunities noted, projects were implemented. The goal of these projects was to decrease the intensity benchmarks and lower the case study mine’s utility expenditures. For the study objective to be accomplished, verified benchmarks had to be created first. By obtaining data from five shafts, the benchmarks could be verified. The data included compressed air flow, surface ventilation fan power, rock winder power, potable water consumption, service water consumption, production data, active haulage length, and employee numbers. The highest correlation and lowest standard deviation for different data sets were calculated to ensure verified benchmarks were used. From the best data set comparison, benchmarks were created for different periods. These different period benchmarks revealed inefficiencies from irregularities and high intensities. The compressed air intensity was compared with production and had a total intensity benchmark of 11.29 m³/(h·ton). The surface extraction fans obtained a total benchmark intensity of 50.2 W/m compared with active haulage length. An irregularity was seen on the shafts’ benchmark, where one shaft did not stop a 1 200 kW fan and 650 kW fan on Sundays. The total intensity benchmark for underground energy was 437.5 W/ton. The Eskom peak period benchmark for the rock winders was 118 W/ton. A total intensity of 119 l/day/capita was calculated for underground potable water. The total service water pumped to the surface had a total intensity benchmark of 51 W/ton. From the benchmarks created, irregularities were noticed, which resulted in savings opportunities that were implemented to reduce the intensities. The total saving achieved for the specific case study mine was estimated to be R2.7 million per annum. It was concluded that the study objective was met as the mine’s expenses were lowered.
- Engineering