Improving deep-level mining refrigeration through increasing pre-cooling efficiency

As the development of deep-level mines expands further into the earth, underground temperatures rise to uncomfortable and unsafe highs. Therefore, the deeper mines become, increased cooling is required. Some mines have refrigeration systems on surface and underground. Due to the costs involved with the installation of underground refrigeration systems, most of the cooling takes place on surface. Due to losses encountered with the transfer of cool air and water from surface, it is important to keep the supply temperatures as cool as possible. Refrigeration systems consist of large, electricity intensive machines along with their auxiliaries. Several studies have focussed on the larger refrigeration machines to increase the efficiency of such a system. The effect that pre-cooling auxiliaries have on a mine refrigeration system will be further analysed in this article. These auxiliaries are inexpensive to run and contribute to the efficiency of the larger machines. A strategy to improved the pre-cooling efficiency was implemented on mine A's surface refrigeration system as a case study. An efficiency increase of 24.4% was observed on the pre-cooling towers. This resulted in the average chill dam temperature decreasing by 10.3°C through increased effectiveness of the mine's fridge plants. The lower system temperatures also added potential for load management that could amount to R 500 000 in additional electricity cost savings annually. This article presents the positive effect that improving pre-cooling efficiency can have on a mine's surface refrigeration system.