Practical determination of heat loads for existing deep level gold mines

Abstract

Deep-level gold mines in South Africa (SA) are faced with immense challenges regarding profitability. Optimising these mines is a pivotal step to prolong the current lifespan of the gold-mining sector in SA. As these mines constantly reach new depths, the challenge of increased working temperatures arises as a result of the geothermal gradient. Excessive heat exposure leads to production loss, directly reducing the industry's profit margins. To ensure that adequate cooling is supplied, with the aim of reducing production losses, heat load studies are conducted. Various approaches have been developed over the past seven decades to assist in determining the actual heat load of a mine. Most of these methods were developed to assist mines during their initial planning phase. Many of these approaches consist of empirical data sets developed in the late 1980s. However, deep-level gold mines are constantly changing, and over the past two decades, have reached record depths and have also seen an increase in mine mechanisation. This study focuses on developing a new approach to determine mine heat loads by using an energy balance. This approach aims to determine all the various heat sinks, heat sources and the geothermal heat source from an energy balance. Two case studies were evaluated using this energy balance approach through simulation and compared to well-known heat-prediction graphs commonly used by industry. From these studies, it was shown that in mines not adhering to the typical mine layout and mining strategy, as was used for developing these heat-prediction graphs, large errors can be made when determining heat loads through using such approaches. Alternatively, it was proven that the energy balance approach can easily be applied to various cases studies. Focus was also placed on the industry application of such an energy balance approach through evaluating an Industry 4.0 roll-out strategy. This strategy is aimed at evaluating the dynamic nature of mine heat loads with greater accuracy and increased frequency. This has also led to the SAJIE publication titled "Industry 4.0 roll-out strategy for dynamic mine heat load management".