Developing an electrical cost saving methodology for platinum plant auxiliary systems

Abstract

The mining of platinum group metals (PGMs) contributes significantly to the South African economy. In 2020, the revenue generated from PGM mining accounted for 2.3% of the country’s total gross domestic product (GDP) (R 101.3 billion). Despite this, the platinum mining industry is struggling to remain profitable and, as a result, unprofitable mining operations are closing. To remain profitable, mining operations have had to undertake cost saving measures. It has been found that reducing electricity costs through load management and energy efficiency initiatives is an effective means of reducing operational costs. Such initiatives have been widely implemented on platinum mining operations. Implementation of such initiatives has, however, been limited on platinum processing plants despite the significant amount of energy consumed by this section. In this study, a methodology was developed to identify feasible electricity cost saving opportunities on platinum processing plant auxiliary systems. The methodology was developed by combining and adapting existing benchmarking methodologies as well as energy audit procedures such as load inventory development, baseline analysis, and intensity analysis. The adapted methodology allowed for plants with large auxiliary system energy intensities to be identified through high-level benchmarking. These plants were then analysed through a combination of baseline and intensity analysis. Baseline analysis was used to identify variable

auxiliary system loads suitable for load management whilst intensity analysis was used to identify auxiliary system energy efficiency opportunities. The methodology was applied to three different platinum processing plants, namely a concentrator, tailings treatment plant, and smelter converter plant. This application was successful in identifying both load management and energy efficiency initiatives across all three plants. Of the identified initiatives, five energy efficiency initiatives were implemented across the three platinum processing plants. In these initiatives, pumping and compressed air systems were optimised by stopping unnecessary equipment from running, which resulted in a combined estimated yearly electricity cost and consumption saving of R6.23 million and 5.44 GWh, respectively. These savings were achieved without negatively affecting plant production. Results from the three case studies are an indication of the potential to obtain electricity cost savings on all South African platinum processing plants. It is estimated that, if the developed methodology were to be applied to all South African platinum processing plants, estimated yearly cost and energy savings of R80 million and 79 GWh could be achieved.