Practical low-cost method to sustain mine compressed air savings

Abstract

The future of the South African mining industry is uncertain as a result of declining ore grades, reduced gold production and increasing operational costs. However, the industry remains a significant contributor to the country's economy. Efforts to ensure a sustained growth path for the mining industry are therefore vital for its survival, as well as the communities that depend on it. Mining companies in South Africa need to focus on reducing their operational costs to remain competitive. One such area offering potential is the production of compressed air, usually the largest consumer of electricity on a deep-level mine. Mines can reduce their operational costs by optimising compressed air production and curbing oversupply. Infrastructure, instrumentation and capital expenditure is limited. As a result, complex and expensive solutions are impractical, and the need for a simple, low-cost solution to match compressed air supply with the required demand is evident. A step-by-step methodology was developed that is easy and inexpensive to implement. The methodology focused on identifying cost-saving initiatives to reduce compressed air network inefficiencies. These inefficiencies were evaluated, and a suitable solution strategy was developed. Appropriate baselines were developed to determine the cost-saving impact after implementation. The methodology was implemented on the compressed air network of Mine A, located in the Free State province of South Africa. The method utilises setpoint control, effective compressor selection and compressed air prediction. The solution strategy was incorporated into an existing Energy Management System (EnMS), with no additional infrastructure costs. The EnMS platform was used to communicate the compressor running schedule to the control room operators, based on the demand requirements. This was shown visually by a message on a computer screen to either start or stop a specific compressor. The implemented solution strategy proved to have no negative effects on the production of the mine, while annual energy cost savings of R1,1-million was shown to be viable. This proves that the solution strategy can be sustainably implemented, and that compressed air savings can be achieved and sustained through practical and low-cost methods.