Reconfiguring mine cooling auxiliaries for optimal operation

Abstract

Deep level gold mines utilise energy intensive cooling systems to maintain an acceptable underground working environment. The majority of these cooling systems are old as they were installed a few years after the mines’ inception. The outdated cooling equipment and inadequate maintenance thereof resulted in reduced efficiencies. Identifying the inefficient cooling subsystems and reconfiguring them for optimal operation will be beneficial for mines. The optimised system will ensure the cooling systems’ service delivery is improved, allowing electricity and cost savings during certain periods of the day. Through investigation, mine A’s cooling system was identified as inefficient and required reconfiguration to ensure optimal operation. A universal methodology was developed to obtain the optimal operation for the mine’s cooling subsystem. Theoretical simulations were developed to predict the effect the subsystem reconfiguration will have on the cooling system’s performance. The simulation proved that improved service delivery is possible by re-configuring the mine’s cooling system. The re-configurations were suggested to mine A. Implementation thereof was done on some of the cooling subsystems. The implemented re-configurations were used to validate the simulation model, from where the effect of the other re-configurations could be predicted. For each of the new desired chilled water temperatures a baseline simulation was done to determine the savings that could be realised when compared to the original chill dam temperature. Implementing the suggested re-configurations on mine A’s cooling subsystem will realise a power saving of 10.4% on the mine’s total power usage (close to 9 MW) whilst delivering a chilled water temperature of 5°C. With a chilled water set point of 4°C the baseline total power usage will increase with 4.8%. The cooling system will be able to maintain a chilled outlet water temperature of 4°C whilst obtaining a power saving of 11% on the new baseline. When the chilled water set point is set to 3°C the baseline simulation power usage will increase with 9%. The chilled water will have an average outlet water temperature of 3.2°C whilst realising in a power saving of 7.8% on the baseline power usage. Due to the successful implementation of some of the reconfiguration initiative strategies and validation of the simulation model, it is safe to state that the mines’ cooling systems can be optimised through reconfiguration of their cooling sub systems.