Novel simulations for energy management of mine cooling systems

Abstract

The South African mining industry purchased 13.8% of the electricity supplied by Eskom in 2015. Deep-level mines are some of the largest electricity consumers in the mineral extraction industry. The electricity costs of these mines contribute to approximately 20% of their operational costs. Deep-level gold mines require mine cooling systems (MCSs) to safely operate at the increasing depths and underground temperatures associated with deep-level mining. MCSs account for 41% of the electricity consumption of these mines. Various initiatives aimed at improving energy efficiency of MCSs have been implemented in the past. However, further operational improvements on these systems are still possible. Operational improvements can be identified with integrated transient response simulations. These simulations can highlight possibilities for new energy saving initiatives and could enable successful energy management. The successful implementation of these initiatives according to design will also be possible due to the forecasting ability of transient response simulations. A comprehensive review of published work revealed a need for simulations that can simulate the transient response of integrated and complex MCSs. Novel transient response simulations and an approach to energy management were developed. Procedures were also developed for new applications from the applied simulations. The models and approach were verified by comparing the actual operation of a deep-level gold mine with the simulated results. A combined accuracy of 97% was achieved. Approximately 74 combined resource hours were required to conduct the integrated MCS simulation of Mine P. A validation case study was conducted on Mine A where a simulation accuracy of 94% was obtained. The complete simulation study on Mine A required 560 combined resource hours, with 144 of those hours used for conducting the simulations. From literature, it was found that a similar approach requires an estimated 1 700 hours. By applying the new models, potential daily energy savings of 145.4 MWh were identified. Potential cost savings of R31 million per annum were identified with the new simulations and approach. In conclusion, novel transient response MCS simulations were developed and tested. The potential power demand reductions and energy savings from widespread adoption of the technologies developed in this thesis could make significant contributions towards national energy efficiency targets. The various capabilities of the novel simulations can still be expanded to optimise the ventilation processes of deep-level mines and thereby reduce the electricity consumption of these systems