Development of a local benchmarking strategy to identify inefficient compressed air usage in deep-level mines

Abstract

South African mines can be up to four kilometres deep, and they are continually extending to keep up with production targets as mining resources get depleted. High electricity costs and additional resources required to mine at greater depths are influencing the profitability of deep-level mines. Furthermore, as deep-level mines mature, the efficiency of compressed air networks deteriorate at a significant pace. The compressed air required to produce one tonne of ore has more than doubled in the past decade. Additionally, neglected compressed air networks result in pressure drops of up to 30%, which adversely effects production. Comprehensive manual audits are usually conducted to identify causes of compressed air inefficiency. However, these audits are not practical in an extensive underground network. This study suggests a novel localised benchmarking methodology to locate and manage factors that contribute to the deterioration of the compressed air network efficiency. The developed methodology was implemented on South African deep-level mines for validation purposes. The proposed methodology was able to identify underground sections with sizeable compressed air inefficiencies. The results were compared with those of conventional audit methods. It was found that the newly developed methodology was able to identify 80% of the operational improvement opportunities identified by auditing the entire underground network. The value of the newly developed methodology is evident when one considers that inefficiencies were located in less than 20% of the time it takes to conduct comprehensive audits. Systematically implementing the methodology on a case study resulted in highlighted electricity cost savings of R7.4 million per annum while a 19% increase in production was observed. The newly developed methodology can have a significant effect on the way underground compressed air networks are maintained. The methodology developed in this study was successfully published as a research article in the journal Sustainable Production and Consumption. The addition to the knowledge base greatly reduced audit times which will serve as a motivation for mine managers to audit underground sections more frequently. Frequent audits will result in improved service delivery and electricity cost savings of the compressed air system.