Improving mine compressed air network efficiency through demand and supply control

Abstract

Eskom is in a position where they are producing sufficient electricity, although rapid expansion and an increase in demand throughout various sections in South Africa can be expected in the future. Large electricity intensive industries such as gold and platinum mines can assist by reducing their electricity demand. Platinum mines are required to increase production output while keeping their overheads as low as possible. One of the areas that can be targeted to reduce operating expenses is mining services such as compressed air. A compressed air network is one of the most ineffective and electricity intensive systems found on a platinum mine. This provides opportunities for implementing Eskom funded demand side management initiatives to decrease the electricity consumption on mining systems, which leads to a reduction in electricity consumption costs. Demand side management initiatives were implemented on two case studies as means to provide electricity and cost savings. Control philosophies were developed, implemented and optimised to ensure a decrease in electricity consumption. A simulation was constructed for each case study and the effect of the control philosophy was simulated and quantified. Each simulation was verified using data from the respective mines’ databases. In Case Study 1, automated control valves were implemented at each compressed air user and the pressure set point was decreased in the Eskom evening peak period. The flow through the compressors were reduced and/or stopped while adhering to system and operational constraints. This resulted in electric power savings of 3.1 MW, which lead to an annual cost savings of R1.9 million. The initial calculations showed that 3.9 MW could be saved, although this was not achieved. It was determined that if repair compressed air leaks was included in this initiative, the target could be met. In Case Study 2, a theoretical initiative was simulated. The effect on electricity consumption was investigated by replacing a single large 15 MW compressor with two less electricity intensive 4 MW compressors. The investigation showed that 76 042 MWh energy efficiency savings per day could be achieved with this initiative. This possible project would have an annual cost saving of R20 million. In this study, it will be shown that a compressed air network can be optimised. These optimisations proved that electricity cost savings can be achieved for the platinum mining industry. In both case studies, it was seen that electricity consumption can be lowered.