1. Copyright © M-Tech Industrial, 2011 Energy audit of mine refrigeration water systems by means of simulation 16 August 2012 Dr. Herman van Antwerpen Pr.Eng M-Tech Industrial

2. Copyright © M-Tech Industrial, 2011 Introduction Purpose of this paper: Demonstrate the benefits of integrated system simulation, Its use in energy assessment of a mine refrigeration system. Type of simulation: Conservation of mass, energy and momentum at system level, i.e. flow rates, temperatures and pressures

3. Copyright © M-Tech Industrial, 2011 Mine cooling water network

4. Copyright © M-Tech Industrial, 2011 Motivations for simulating a system On a new design: Do component sizing Verify component selection, control philosophies, etc. On an existing plant: Compile the data set that describes system operation Develop good understanding of system operation Check instrumentation consistency / high-level fault finding Assess changes at a system-level Identify savings opportunities: survival of deep mines

5. Copyright © M-Tech Industrial, 2011 Classification of loads and savings Energy efficiency “DSM valves” Baseload Peak load

6. Copyright © M-Tech Industrial, 2011 Basic refrigeration loop

7. Copyright © M-Tech Industrial, 2011 Water distribution system Manos Engineering, Welkom

8. Copyright © M-Tech Industrial, 2011 Network for level

9. Copyright © M-Tech Industrial, 2011

10. Required phenomena Elevation differences Cooling car characteristics Heat pickup along pipes in haulages

11. Copyright © M-Tech Industrial, 2011 Cooling car characteristics

12. Copyright © M-Tech Industrial, 2011 Chilled water heating along haulages Journal of the SA Institute of Mining and Metallurgy: Rawlins, C.A. (2007) “Mine cooling and insulation of chilled water transport pipes” Jones, M.Q.W. (2003) “Thermal properties of stratified rocks from Witwatersrand gold mining areas”

13. Copyright © M-Tech Industrial, 2011 25ºC Reference data With thermostatic control Cooling car control

14. Copyright © M-Tech Industrial, 2011 Power consumption

15. Copyright © M-Tech Industrial, 2011 Conclusions Regarding mine refrigeration Opportunity: “Mine-proof” cooling car flow control. For some mine layouts: Minimum refrigeration cost: highest possible chilled water temperature. Constraint: cooling car inlet pressure. Regarding simulation Industrial Energy Efficiency projects or system-level optimisation requires integrated simulation: flow rate, temperature and pressure.

16. Copyright © M-Tech Industrial, 2011 Questions? Acknowledgements