Energy audit of mine refrigeration water systems by means of simulation

The workplaces in current deep-level mines are refrigerated by vast, complex, chilled water systems. These complex refrigeration systems are unique to each mine and change over time. AngloGold Ashanti realised that special methods are necessary to deal with this complexity and started collaboration with M-Tech Industrial to develop integrated simulation models of the entire thermal-fluid system. This was done using the locally developed software FLOWNEX. This paper demonstrates some of the benefits of integrated system simulation in the identification and evaluation of methods for saving energy. As case study, a mine with 7000kW refrigeration and pumping electrical load was found to present an opportunity for between 1500kW and 1800kW saving, provided the end-usage components in the system, the cooling cars, are properly maintained. Chilled water temperature optimisation presents an opportunity of around 500kW, provided the cooling car flow control functions as intended. These options would have been difficult to identify or evaluate without having an integrated simulation model of the overall system.