Optimising gold ore transportation systems for electricity cost savings

Abstract

Electricity is an essential but limited resource in South Africa. Limited supply capacity and growing demand cause electricity prices to increase rapidly, therefore, reducing electricity consumption. Costs are critical within the mining sector. Demand-side management (DSM) is an appealing and effective initiative to reduce electricity consumption and costs. Various DSM initiatives have already been implemented on isolated components within gold ore transportation systems. Implementing such initiatives on multiple gold ore transportation systems in an integrated ore distribution network has, however, not yet been analysed, despite the large cost-saving potential. A gold-processing plant is usually supplied from multiple mineshafts and waste rock dumps within an ore distribution network. Implementing DSM on a gold ore transportation system can influence the ore distribution channels and the gold plant operation. This study focused on implementing a DSM initiative on an integrated ore distribution network without negatively influencing production. Electrical load management was recognised as the primary opportunity to deliver feasible cost savings. In-depth investigations were conducted on several mining processes, which can be categorised as mining, ore transportation and gold-processing. Within the ore transportation system, rock winders are identified as the largest electricity consumers, which is the component that has to be optimised. Although load management potential may exist, it may not be feasible for practical reasons. Simulations were developed to fully quantify the effect of implementing load management on rock winders at multiple shafts and the effect on the system as a whole. This study was implemented on two complex gold ore transportation systems as case studies. Peak period load shifting of 3.1 MW and 1 MW, respectively, were achieved on average for a single test week. This is equivalent to a total electricity cost saving of R1.1 million and R380 000 per annum, respectively. If the results of this study are extrapolated to the rest of the mining sector, the potential cost savings could amount to R37 million per annum. Large electricity cost savings were achieved without affecting the overall production negatively. Furthermore, implementing load management on an ore transportation system improved the monitoring and control of the ore supply. This creates electrical load management opportunities on gold-processing plants due to improved production planning capability.