Mine Water Treatment At Landau Colliery. Gerhard Stenzel- Mine Manager ordinator Environment

Transcription

1 Mine Water Treatment At Landau Colliery Gerhard Stenzel- Mine Manager Peter Günther -Divisional Co-ordinator ordinator Environment

2 Water Management & Treatment Water Management & Treatment But why treat water? This is a coal mine!!!

3 CORROSION

4 SEEPAGE

5 DECANT

6 ACID MINE DRAINAGE ACID MINE DRAINAGE

7 Nature of the Water Nature of the Water Derived from various sources : Pyrite & low calcite in coal --> acidic waters Stored water in old U/G workings Seeps and decants Polluted water generated at co-disposal discards facility Combination of both neutral / acidic waters with low / high sulphate concentrations

8 Mine Coal / Acid Water Relationship Ash (%) (Minerals Bureau) CaO MgO ph Water Quality (Coaltech) Mg 2+ (mg/l) Kromdraai South Witbank Kleinkopje Goedehoop Brandspruit

9 Water Management Policy Water Management Policy Prevent / minimise pollution Maximise clean & dirty water separation Minimise imported water Maximise re-use of polluted waters Treat water

10 Water Management Projects Water Management Projects Completed ( ) : Water management feasibility (R 6.0 m) Pollution control upgrade Phase 1 (R 14.0 m) Acid water collection & liming plant (R 18.7 m) CSIR biological sulphate removal 200 m 3 /day (R 0.8 m) Limestone plants (R 3.1 m) 3 Ml/day Delkor/Paques sulphate reduction plant (R 20 m) 0.36 Ml/day Wren sulphate reduction plant (R 5.3 m) Pollution control upgrade Phase 2 (R 10.7 m)

11 Lime Neutralisation Lime Neutralisation Process water make-up ~ Ml/day Use lime in a HDS Liming Plant to neutralise acid water for process water Remove acidity and iron, reduce aluminium & manganese & raise ph to 8.5 Lime cost ~ R / ton delivered

12 Kromdraai Liming Plant

13 Limestone Neutralisation Alternative alkali source to lime Perform similar functions to lime used in a HDS Liming Plant However, ph max ~ 7.5 & slower reaction Different handling & dosing Limestone cost ~ R 165 / ton delivered Savings to date ~ R 3.5 million / annum (> 45 % savings)

14 Limestone Plant Limestone Plant

15 Limestone Mixing & Dosing Plant Dosing Tank Dosing Pump Density Meter Mixing Tank Limestone Slab Ultra-sonic Level Indicator Recycle & Slurry Pump HP Jets

16 Gypsum Scaling Gypsum Scaling High sulphate waters neutralised with lime / limestone (calcium) ==> gypsum (CaSO 4 ) scaling Affects process equipment Not able to discharge to rivers SACE ~ 115 million m 3 of stored water in old underground workings

17 GYPSUM SCALING

18 Gypsum scale on Magnetite Gypsum scale on Magnetite Only magnetite Magnetite + Gypsum

19 Sulphate Reduction Sulphate Reduction Technologies Supplier Type of Process Final Sulphate CAPEX OPEX Water Concentration R million / R / m 3 Recovery mg/l Ml / day % Degremont SRO Membrane < Keyplan SRO Membrane < Paques Biological < CSIR Biological < Gyp-Cix Ion Exchange < SAVMIN Ettringnite < Lektratek Electrochemical < Wren Hydrothermal <

20 3 Ml/day 3 Ml/day Biological Sulphate Reduction Plant

21 Anaerobic reactor : 3 Ml/day Biological 3 Ml/day Biological Sulphate Reduction Plant Feed acid water direct Neutralise with treated recycle stream Heat feed water with coal fired boiler Use ethanol as carbon source for SRB s Sulphate reduced from 2400 mg/l to < 100 mg/l as sulphide (H 2 S) using SRB s Generate 1 mg/l alkalinity as CaCO 3 for every 1 mg/l of sulphate reduced

22 3 Ml/day Biological Sulphate Reduction Plant Aerobic reactor : H 2 S reduced to sulphur using aerobic bacteria Control reduction through redox potential Sulphur to be dewatered & co-disposed with coal discards Limestone (alkalinity) precipitated - can be used directly for neutralisation in HDS liming plant COD removed Final sulphate concentration ~ 200 mg/l

23 Future Enhancements Coal Gasification? Gasify discard coal (low CV, high ash) in a coal gasifier to produce hydrogen Hydrogen 3 times more efficient than alcohols Use excess thermal energy in SR process

24 Performance : 3 Ml/day Biological Sulphate Reduction Plant Current flow 3.0 Ml/day due to ramp up Best results : ph = 8.0 & sulphate = 180 mg/l Capital cost : R 20 million (2002) Operating cash cost (no capital redemption) : Initial (using ethanol) = R 5.87 / m 3 Present (using propanol) = R 5.09 / m 3 Future (using hydrogen) ~ R 3.50 / m 3

25 0.36 Ml/day Wren Hydrothermal Sulphate Reduction (HSR) Pilot Plant

26 Wren Hydrothermal Sulphate Wren Hydrothermal Sulphate Reduction (HSR) Technology Neutralise acid water with conventional lime / limestone neutralisation Raise ph to ~ 11 to precipitate magnesium and associated sulphates to ~ 1400 mg/l Use high temperature and high pressure to precipitate gypsum in reactor Reduce sulphates from 3000 mg/l to < 200 mg/l

27 Wren Hydrothermal Sulphate Wren Hydrothermal Sulphate Reduction (HSR) Technology Performance : 1 st Trial 2 nd Trial Best Flow (m 3 /hr) Water Recovery (%) Overall Availability (%) Final Sulphates (mg/l) Capital cost : R 5.1 million Operating cash cost : R 3.50 / m 3

28 Mine Water Resources Mine Water Resources Current water deficiency in catchment ~ 192 million m3 / annum Current estimated stored water volume ~ 195 million m 3 : SACE ~ 115 million m 3 Other adjacent mines ~ 80 million m 3 Current estimated water make ~ 11 million m 3 / annum : SACE ~ 7 million m 3 / annum Other adjacent mines ~ 4 million m 3 / annum Could supply 1 / 3 up to 1 / 2 of additional water required However, all the water is either acidic / neutral & saline with sulphates & requires treatment

29 Potential Water Users Potential Water Users Witbank / Middelburg region water users : Industry (Highveld Steel & Vanadium, Ferrobank, Columbus Steel) Mines (Anglo Coal, Ingwe, Xstrata, etc.) Witbank Municipality Require additional 50 Ml/day purified water or provide industrie Require additional 50 Ml/day purified water or provide industries s direct with lesser purified water & reduce demand Middelburg Municipality Townships, rural areas, etc. Irrigation (farmers, veggie gardens, etc.) Bottled water

30 Bottled Water S.Pellegrino ph = 7.5 S0 4 = 535 mg/l COST = R 23 / bottle (750 ml) = R 23 / bottle (750 ml) = R / m 3 Kwa Maritane ph = 7.9 S0 4 = 20 mg/l COST = R 8.50 / bottle (250 ml) = R 8.50 / bottle (250 ml) = R / m 3 Valpre ph = 6.8 S0 = < 5 mg/l 4 = < 5 mg/l COST = R 4.50 / bottle (500 ml) = R 4.50 / bottle (500 ml) = R / m 3

31 Compared to? Compared to? Tap Water ph = 7.3 S0 4 = 220 mg/l COST = R 3-5 / m 3

32 Future Opportunities / Future Opportunities / Challenges? Acid Mine Water ph = 3.0 S0 4 = 2470 mg/l Treated Mine Water ph = 7.9 S0 = ~ COST = R 3.50 / m 3 = ~ mg/l COST = R 3.50 / m

33 Or why not this.? Or why not this.?

34 Delivery to your front door!! Delivery to your front door!!

35 Questions? Questions?