Optimising production through improving the efficiency of mine compressed air networks with limited infrastructure
Abstract
The global gold mining industry is currently on a growing trend, while the local gold mining industry in South Africa has been experiencing a decline in gold production. This is due to a unique set of production challenges faced by this industry of which production cost increases are one of the major concerns. This encourages deep-level mines to implement cost saving initiatives in the form of effectively using existing infrastructure.
One such area offering large potential for optimisation is addressing deep-level gold mine compressed air network inefficiencies. These inefficiencies include low service delivery pressure supplied to pneumatically operated drill rigs in the working areas. Lower service delivery results in an increase in drilling time and an increase in compressed air usage which contributes to operational costs. Through addressing these inefficiencies an increase in rock penetration rate can be achieved on the pneumatically operated drill rigs, leading to reduced drilling times.
A need was evident to optimise these compressed air networks with the aim of improving the total amount of drilling time. A methodology was developed with the aim to identify, evaluate and address these compressed air network inefficiencies. This methodology incorporated root cause analysis as well as guidelines for effective boundary selection procedures.
An investigation performed on Mine A indicated that a specific compressed air network inefficiency contributed to a pressure drop of approximately 87 kPa during peak drilling periods. The pressure drop was measured from the compressed air supply to the working areas of the main production levels. The developed methodology was applied and a solution was developed to address this inefficiency. It was simulated that replacing specific undersized pipe sections with the correct sized pipes would reduce the pressure drop by at least 45 kPa during daily operation.
The solution was implemented on the compressed air network of Mine A. Nearly 400 m of incorrectly sized pipe sections and line restrictions were replaced with correctly sized pipe sections. This resulted in a minimum measured pressure drop of 14 kPa during off-peak drilling periods and decreased the peak drilling pressure drop to approximately 25 kPa. Validating these results with the predictions through simulation yielded an error of less than 2%. The improved service delivery pressure was used to calculate the improvement in the drilling rate of rock penetration. The selected model indicated a 20% increase in drilling rate because of the increase in supply pressure. This improved penetration rate was translated into a production increase of approximately R 11-million per annum. This resulted in a potential financial benefit of 3% increase in terms of production profit for the presented case study
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