Mine cooling

Cooling the world's deepest single-shaft mine: cooling Anglogold Mponeng gold mine in Gauteng, South Africa, is a challenge - the mine is 3.68 km deep and without cooling, temperatures can reach 60°C at the mine face. Six 3.5 MW Eco-Vim refrigeration units are used to produce around 5000 t of ice/day. The system uses chilled water being pumped from the plants to a freezer vessel, in which water is subjected to pressure below triple point conditions, and where water, ice and water vapour exist simultaneously. Some water evaporates and some becomes an ice slurry. Water vapour is drawn off, while the ice slurry is separated into brine and ice on the surface, before the ice is fed to an ice dam underground. The brine is then returned to the plant, while recirculated clarified return water is used to restore the cooling capacity of the ice. Thanks to the IDE (Israeli Desalination Engineering) equipment, pumping costs are typically reduced by 80%, since the mass of water to be pumped is reduced by this amount. Other uses of this technology include combustion air cooling in gas turbines, central air conditioning and cooling in large malls and buildings, ice-based energy storage, process cooling and all-weather snow-making.