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1 Title of presentation Reducing energy usage through the implementation of an ice cooling system Jan du Plessis, Senior Consultant, Gold Fields Ltd, Gauteng, South Africa MRA Safety in Deep Mining 2008, Johannesburg, South Africa

2 Background ❿ Ice was harvested and stored in China before the end of the 1 st Millennium ❿ Iced liquors & frozen juices popular in France 17 th century ❿ Ice commercially shipped from New York in 1799 ❿ 35 Commercial ice plants in USA in 1879, more than 200 a decade later and 2000 in 1909 ❿ 14 to 15 million tons of ice were already consumed in 1907 ❿ Brewing was the 1 st activity to use mechanical refrigeration extensively since the 1840 s ❿ Introduced into Gold Mining industry Late 20 th century MRA Safety in Deep Mining 2008, Johannesburg, South Africa 2

3 Environmental Background ❿ Deep mine studies indicate that the thermal limit for unimpaired cognitive performance range between 28 o C and 30 o C (Wet bulb) ❿ Ability to concentrate and spatial perception decrease when wet bulb start to exceed 28 o C (Maintain speed of performance at lower accuracy) ❿ >29 o C individuals work faster, but less accurate ❿ Specific bearing on operators using joystick / lever controls MRA Safety in Deep Mining 2008, Johannesburg, South Africa 3

4 Physical Performance Reductions in performance at various wet bulb temperatures Wet bulb temperature ( o C) Physical performance decrement (relative to performance at 25,0 o C) 25,0 0% (assumed) 27,0 3,8% 29,0 14,0% 31,0 50,5% 33,0 70,2% MRA Safety in Deep Mining 2008, Johannesburg, South Africa 4

5 Workplace condition influence 30 Mean injury rate (n /1000 employees) >31 Range of stope reject wet bulb temperatures ( C) MRA Safety in Deep Mining 2008, Johannesburg, South Africa 5

6 Environmental Design Conditions within Gold Fields ❿ Average Workplace Temperature <27,50 C Wet bulb ❿ <28,5 C Wet bulb Reject temperature ❿ >300 W/m 2 Specific Cooling Power ❿ ALARA not exceeding 5 msv/year radiation ❿ <0,05 mg/m3 dust level MRA Safety in Deep Mining 2008, Johannesburg, South Africa 6

7 Environmental Design Conditions within Gold Fields ❿ Maximise Surface Bulk air cooling ❿ Cooled service water ❿ Optimise underground refrigeration installations ❿ Use of ice to make up shortfall ❿ Use of Ice allows more flexibility MRA Safety in Deep Mining 2008, Johannesburg, South Africa 7

8 Why Ice ❿ With the ever increasing demand on energy and gold mined deeper, a paradigm shift is required. ❿ Deeper areas needs more cooling at an increased cost ❿ Water is a big NO in mining and is not only expensive to get rid of, but it is also expensive to supply ❿ Ventilation and cooling is one of the biggest constraints for mining at depth (Deep Mine) ❿ Capital cost of approximately 30% ❿ Electricity cost of 22 % MRA Safety in Deep Mining 2008, Johannesburg, South Africa 8

9 Why Ice ❿ Ice systems were in general found to be the least expensive cooling medium for surface cooling generation at depths in excess of 3000m ❿ As electrical cost increases the economical depth for ice is decreasing ❿ Current economical depth at least 2500 m ❿ Ice plants are becoming less capital intensive as technology evolves and the cost of pumping is increasing ❿ Pumping energy can be reduced up to a factor of five ❿ Potential Energy Efficiency synergies with CDM and DSM MRA Safety in Deep Mining 2008, Johannesburg, South Africa 9

10 Why Ice MRA Safety in Deep Mining 2008, Johannesburg, South Africa 10

11 MRA Safety in Deep Mining 2008, Johannesburg, South Africa

12 DAILY LOAD PROFILE MRA Safety in Deep Mining 2008, Johannesburg, South Africa

13 Typical pumping layout per shaft Contribution of pumping to daily load profile Surface Pump station 4 +/ 1800KW Pump station 3 +/ 1800KW Pump station 2 +/ 1800KW Effect of saving 140 l/s over 24hr period (12 Ml/day) Estimated kw to run a pump to pump station is 140 l/s =1800 kw 4 stages pumping : 4 x 1800KW = 7,2 MW +/ 1/3 of required 10% reduction Pump station 1 +/ 1800KW MRA Safety in Deep Mining 2008, Johannesburg, South Africa

14 Item Value Unit Chiller output capacity 9.6 MW Chiller COP 5 dimensionless Chiller input capacity 1.92 MW Capacity factor of chiller 80% dimensionless Electricity consumption of chiller 13.5 GWh/yr Factor of increase in electricity consumption by conversion to ice chilling Electricity consumption of chiller in the project case Incremental electricity consumption by conversion to ice chilling 1.22 dimensionless 16.4 GWh/yr 3.0 GWh/yr Baseline pump capacity 4,968.0 MW Pump capacity factor 100% Electricity consumption by pumps in the baseline Ratio of energy saving of pumps by conversion to ice chilling 43,519.7 GWh/yr 78% Energy conservation of pumps 33,848.6 GWh/yr MRA Safety in Deep Mining 2008, Johannesburg, South Africa 14

15 Vacuum Ice ❿ The process uses the phenomenon of the triple point of water, where vapour, liquid and ice coexist. Inside the VIM (Vacuum Ice Machine), water is subjected to triple point conditions in a tank under vacuum. The flashing forces part of the water to evaporate while the remaining liquid freezes. Within this process the latent heat of crystallization causes evaporation ❿ For every kg of vapour flashed off, about 7,5kg of ice crystals are formed ❿ Produces slurry ranging between 17% to 75% ice mass fraction (IMF) MRA Safety in Deep Mining 2008, Johannesburg, South Africa 15

16 Vacuum Ice Process MRA Safety in Deep Mining 2008, Johannesburg, South Africa

17 Hard Ice ❿ Ammonia is used as refrigerant ❿ Ammonia is used to chill water on plates to form ice ❿ Gassed off ammonia is used to heat the plates to dislodge the ice ❿ Ice is harvested onto screw feeder and is conveyed to the shaft ❿ Fed down the shaft in pipe columns ❿ Ice melting dams ❿ Closed loop piping and cooling installations MRA Safety in Deep Mining 2008, Johannesburg, South Africa 17

18 Schematic of Plate Ice Maker MRA Safety in Deep Mining 2008, Johannesburg, South Africa 18

19 Vacuum vs. Hard Ice Vacuum Ice Hard Ice Cost R7000/kW R5200/kW Ice mass fraction 70% 90% Ice : Water ratio 3.8 x less pumping 5 x less pumping Technology Efficiency Still developing (Compressors surging due to high ambient temperature) High 242 tons / MW Proven (ERPM) 11MW=9MW nominal 312 tons / 70% IMF Safety Water not harmful Ammonia harmful to people Environment Salt / Brine mess up environment Ammonia not harmful to nature Risk Salt damage steelwork Ammonia could be managed safely MRA Safety in Deep Mining 2008, Johannesburg, South Africa 19

20 Modular Design ❿ Infrastructure on surface Plant to shaft ❿ 11MW (9.6 MW nominal) Two compressors ❿ Two sets of ice plates ❿ Interchangeable with compressors ❿ 1 module = 23.4 kg/s (1988 tons per day) ❿ R60m for 1 module and infrastructure to shaft ❿ Modules could then be added at R41m per module. MRA Safety in Deep Mining 2008, Johannesburg, South Africa 20

21 MRA Safety in Deep Mining 2008, Johannesburg, South Africa 21

22 Other potential projects within mining ❿ Hydrolift systems (3CPF SYSTEM) ❿ Hot water control ❿ Pumping ❿ Lighting ❿ Compressed air ❿ Hoisting ❿ Water/Compressed air shut off valves ❿ Hilti Drills MRA Safety in Deep Mining 2008, Johannesburg, South Africa 22

23 Other potential projects within mining ❿ Turbo chiller ❿ Refuge Chamber ventilation ❿ Solar Cooling ❿ Fan efficiency ❿ Ventilation optimisation ❿ Review of insulation practices ❿ Methane capture and electricity generation MRA Safety in Deep Mining 2008, Johannesburg, South Africa 23

24 Summary ❿ There are many ways to reduce the cost of mining one of them is through water management ❿ Hydrolift systems need to be looked at in conjunction with ice plants ❿ Ice should be been introduced to deep level mining ❿ Why should the fishing industry be the leader in this market? MRA Safety in Deep Mining 2008, Johannesburg, South Africa 24

25 Acknowledgments ❿ I would like to thank Gold Fields and Kloof Management for the opportunity to present this presentation. ❿ Special thank you to the following people who worked hard in putting all the background work together: Stefan van Heerden Dave Farlam Doug Foley Mike de Koker Jacques van Rensburg MRA Safety in Deep Mining 2008, Johannesburg, South Africa 25

26 Questions Have you made that paradigm shift? MRA Safety in Deep Mining 2008, Johannesburg, South Africa