Expanding compressed air management through cross cut isolation

Abstract

Compressed air on deep-level mines is regarded as an important source of energy for underground mining operations, as the compressed air network forms the backbone of several mining processes over a 24-hour mining cycle. Historically, compressed air networks on deep-level mines were found to have low energy efficiencies due to mismanagement of infrastructure and misappropriation of compressed air. Therefore, compressed air becomes an inefficient and costly way of supplying energy to underground mining operations, if not correctly managed. To address the low energy efficiency, several supply and demand side energy management initiatives have been implemented. However, the majority of these initiatives predominantly focus on matching compressed air supply with an artificially lowered demand, achieved through surface or level valve control. These initiatives therefore only address the symptoms of mismanagement and misappropriation, as they do not directly address the root cause of the high demand for compressed air. There is therefore still significant scope to improve the overall efficiency of compressed air networks on deep-level mines by implementing measures to directly address compressed air misappropriation and mismanagement. One such measure is the implementation of cross cut isolation valves. The primary objective of this study is to investigate the scope and requirements for implementing cross cut isolation on deep-level platinum mines. A solution strategy was developed which quantified the energy benefit of implementing both manual and automatic cross cut isolation. Thereafter, the sustainability requirements for ensuring the success of both manual and automatic cross cut isolation control strategies were identified. The solution strategy was applied to a deep-level platinum mining shaft in South Africa. It was identified that the cross cuts accounted for approximately 85% of the total wastage consumption. Thus, the energy benefit quantification of implementing cross cut isolation determined that a

potential daily energy saving of 43,3 MWh can be achieved over the 24-hour weekday mining profile as a result of a 50% demand reduction. The sustainability requirements were successfully identified for both manual and automatic cross cut isolation control strategies. The sustainability and impact of manual cross cut isolation was found to be highly dependent on the cooperation of the mining personnel and was unable to provide a sustainable solution. It was therefore concluded that this strategy comes with high project maintenance and resource management requirements when attempting to achieve sustainable energy savings. However, automatic cross cut isolation effectively eliminated the reliance on the human factor and the case study was able to obtain a sustainable energy saving as a result of this. Therefore, the implementation of an automated control philosophy is preferred to eliminate the human error in order to maximise the energy savings and the sustainability of the initiative.