1. IMPROVING COOLING SYSTEM EFFICIENCY WITH PRE-COOLING AJ Schutte 15 August 2012

2. Introduction National power network under strain Electricity price increases Mining is electricity intensive Cost effective mining Inefficient mine cooling and ventilation system

3. South African mining Reduce operational cost SA mining depth requires cooling Surface refrigeration system System components Dams and transfer pumps Heat exchange towers Refrigeration machines

4. Surface refrigeration system layout

5. Mine cooling Surface refrigeration Cooling load Mine production water Bulk air coolers (BAC) Cooling components Pre-cooling towers Refrigeration machines

6. Mine water quality Production cause water temperature increase Salts dissolve Evaporation increases solution concentration Water treatment Solid particles suspension Settlers Mine production surpass settlers and treatment

7. Pre-cool towers Layout Fan Mist eliminators Spray nozzles Fill Production water cools Crystals + solid particles

8. Case study: Replace pre-cool towers Mine production exceeding infrastructure Summer refrigeration operate at 100% Winter period maintenance High efficiency film fill used Tower fan maintenance

9. Replaced pre-cool towers Original design exceed requirement New fill specified Direct drive fans New fill vibrates

10. Results - Temperatures Inlet temperature of 30 o C Flow 340l/s Old tower outlet temperature 23 o C New tower outlet temperature 19 o C Improvement of 4 o C

11. Results - Electricity 1 MW saving through out the day

12. Conclusion Replacing mine pre-cool towers resulted in a 4 o C colder outlet temperature This resulted in 24hour average electricity saving of 1MW Fans utilisation increased Winter period pre-cooling now possible

13. The End Questions? Thank you