Implementing energy efficiency measures on the compressed air network of old South African mines

Abstract

anthracite with the highest fixed carbon and lowest ash contents exhibited the smallest shrinkage during in situ TMA calcination. High fixed carbon, low ash type anthracites are therefore less prone to dimensional instabilities in Soderberg electrodes, as a result of poor calcination. The dimensional changes observed in the calcined anthracites were very similar to those observed for the electrode graphite samples. The expansions/shrinkages observed in the graphite samples were mostly less than 0.5%, whereas the expansions/shrinkages observed in the various calcined anthracites were approximately 0.6 to 0.9%. The difference in the magnitude of the dimensional behaviour between the calcined anthracites and the graphite can be attributed to the fact that the graphite had already undergone maximum structural ordering (having been pre–baked at 3000°C). A simulation was done to indicate the effect of underground valve control in a compressed air network. The simulation presents the effect of increased pressure by active compressed air control on each of the mining levels. A decrease in pressure will result in lowered operation of the compressors. The implementation of EE/DSM was successfully completed for this case study, which resulted in an average saving of 1.80 MW (91.6% of the target savings) for the three performance assessment months. To achieve this savings the Real–time Energy Management System (REMS) was installed to ensure automatic control on the newly installed infrastructure for the compressed air network. Due to the successful implementation of the project, the client benefitted from large financial savings. Furthermore, it was demonstrated that EE/DSM strategies could be successfully implemented on the compressed air systems of old gold mines.