1. Energy savings on mining compressed air networks through dedicated process plant compressors Rudi Joubert 16 August 2012

2. Introduction Compressed air networks Line friction Air losses through leaks Reducing system pressure Benefit of dedicated compressors Installing a dedicated compressor Conclusion

3. Compressed air networks Compressors Large installed capacities End users Mining shafts Process plants Different time of use

4. Losses through leaks  Volumetric flow rate - V f [m 3 /h];  Number of air leaks – NL [dimensionless];  Atmospheric air temperature - T i [ o C];  Line air temperature – T l [ o C];  Line pressure - P l [kPa];  Atmospheric pressure - P i [kPa];  Isentropic sonic volumetric flow constant – C 1 [7.3587m/s K 0.5 ];  Conversion constant – C 2 [3600s/h];  Isentropic coefficient of discharge for square edged orifice - C d [0.8];  Leak diameter – D [mm]; and  Conversion constant – C 3 [10 6 mm 2 /m 2 ].

5. Line friction Unique to each network Pipe length Pipe diameter Wall roughness Air flow speed Line pressure

6. Reducing system pressure Reduced losses over transfer lines Reduced air lost through leaks Supply reduction of 14kPa result in an average power saving of 1%

7. Benefit of dedicated compressors Dedicated high pressure supply Eliminate long transfer line Reduce losses through leaks Relatively easy to install Cleaner air

8. Installing dedicated a compressor Installed a dedicated compressor Isolate gold plant Reduce system pressure

9. Installing dedicated compressors

10. Conclusion Dedicated plant compressor permits unchanged pressure delivery where high pressure is required Reduced system pressure result in energy savings Sum of total electrical load on network still lower than before intervention

11. Questions?