Analysing the impact of refurbishing precooling towers on a deep-level mine

Abstract

The challenges faced by South African gold mines are increasing operating costs, resulting in a decreased profit margin. Increased mining depths are one of the highlighted challenges but is required to remain competitive within the global industry. However, the increased depths generate higher working area temperatures. Refrigeration systems are used to cool underground working areas. They are also one of the most energy intensive systems on a deep-level gold mine. Eskom electricity costing increased by 13.82% for 2019/20, necessitating strategies to mitigate costs. Optimising the refrigeration system by lowering the inlet water temperature is one strategy to mitigate cost. Service water is precooled before entering the refrigeration cycle, making precooling towers a crucial component to the refrigeration network. High precooling tower performance will result in a lower outlet water temperature and an increase refrigeration network performance. To maintain optimal precooling tower performance, timely refurbishment is required. This study focused on evaluating the impact of deep-level gold mine precooling tower refurbishment. This was done by developing a refurbishment strategy and analysing the impact thereof. A five-step methodology process was developed to evaluate the impact of precooling tower refurbishment. In the first step a feasible location is identified. Step 2 continued by evaluating the identified precooling tower through a developed evaluation checklist. The checklist is used to identify and recommend solutions to common problems associated with induced draft precooling towers. The recommendation will form the refurbishment solution to be implemented in Step 3. In Step 4, the precooling tower performance is re-assessed. If the performance is satisfactory, the impact is evaluated in Step 5 by analysing the changes to the refrigeration network. The methodology strategy was validated through a case study. The evaluation checklist was used to identify precooling problems and develop a refurbishment solution. Precooling tower efficiency increased by 29.5% after refurbishment, which resulted in an annual cost saving of R6.86 million. The cost saving amount was quantified by evaluating the impact of precooling tower refurbishment.