Selection of Tailings Paste Thickener. 17 February Norris September / Rebecca Kirkwood

Transcription

1 Clermont Coal Mine Project Selection of Tailings Paste Thickener AusIMM Technical Meeting 17 February 2010 Norris September / Rebecca Kirkwood

2 Topics > Project Overview > Metallurgical Design Considerations > Tailings Disposal Study > Thickening Test Work (Outotec) > Current Construction Activities

3 Project Overview

4 15km north of Clermont Township 15km east of Blair Athol Mine Open cut, truck/shovel operation and in pit crushing & conveying system Planned production of 12Mtpa Expected mine life of 17 years

5 High quality coal deposit with 192 Mt of proved open cut reserves Contained within Wolfang Basin - an elongated north-south trending basin approximately 5 km long by 1.5 km wide Three major coal seams the Gowrie, Prospect and Wolfang seams Seams range from between 80 and 290 m below ground level Wolfang seam approximately 40 m thick Approximately 17% of ROM coal will need to be washed over life of Project

6 Metallurgical Design Considerations

7 Feed Rates > CHP Nominal Feed Rate 2050 tph > CHP Design Feed Rate 2500 tph > CPP Design Feed Rate 300 tph

8 CPP Equipment Utilised > DMC: mm > Spirals: mm > TBS & Spirals were consider for the mid fraction > Spirals were selected as they are better understood and appropriate for the required separating density > Paste Thickener: -0.1mm > Large proportion of the fine fraction is clay, hence disposal of the fine fraction does not compromise energy recovery

9 CPP Yields Circuitit Minimumi Nominal Maximum Dense Medium Cyclone 22% 65% 96% Spirals 47% 75% 95%

10 Tailings Disposal Study

11 Traditional Disposal Methods Conventional Tailings Dam > Require large land areas. > Environmental challenges: o o o Soil erosion; Dust pollution; Water contamination. > Dangerous Fencing required. > Approval for dam not sought in mining application for Clermont, hence alternatives were explored. Co-Disposal Dam > Disposal of coarse and fine reject combined prior to pumping. > Finer fractions fill voids created by larger fractions, thereby creating a competent structure and can be driven on in a week. > Smaller emplacement area required than conventional tailings dam. > Downsides include higher power & water consumption, pipeline wear and emplacement management.

12 Background Tailings Disposal > At FS all rejects were to be co-disposed > Co-disposal would require 636 ML / annum > Initial groundwater studies reported that this water would be available from underground sources > Later investigations found that this was incorrect > New philosophy had to be adopted Number of technologies investigated

13 Technologies Investigated > Filter Press > Vacuum Filters > Belt Press Filters > Paste Thickeners > Screen Bowl & Solid Bowl Centrifuges Rejected from study due to high maintenance and power consumption & Inability to dewater smaller fraction (-38µm) (Screen bowl only)

14 Water Consumption Water Sav ving (%) 71% 70% 69% 68% 67% 66% 65% 64% 63% 62% 61% Filter Presses Vacuum Filters Belt Press Filters Deep Cone Thickener

15 Power Saving Total Installed Power 100% 90% 80% 70% Power Sav ving (%) 60% 50% 40% 30% 20% 10% 0% Filter Presses Vacuum Filters Belt Press Filters Deep Cone Thickener CPP co-disposal design had allowed for 1456 kw which includes 3 x co-disposal pumps, 2 x return water pumps & 1 x gland water pump.

16 Capital Cost 30% 25% 20% Cap pital Cost Increa ase (%) 15% 10% 5% 0% Filter Presses Vacuum Filters Belt Press Filters Deep Cone Thickener Price comparison based on fixed plant only, does not include mobile equipment cost. Cost of Deep Cone Thickener is not much greater than a conventional thickener.

17 Maintenance > Co-Disposal Reasonably maintenance intensive due to pumping coarse material Rotation of pipeline every month and replacement 3 times per year Frequent maintenance required on pumps > Filter Presses More maintenance friendly than older models Filter bags more reliable Red Mountain CPP experienced cake discharge problems with their filter press and so replaced them with belt press filters

18 Maintenance Continued > Vacuum Filters Most common dewatering method for flotation product Most economical unit to operate Maintenance costs could possibly increase using this for tailings > Belt Press Filters Installed & commissioned in some CPPs in CQ, but experienced very high maintenance costs and much downtime Some of these units were replaced with more reliable units which dropped maintenance costs significantly > Deep Cone Thickener Least moving parts of any other option Robust and reliable By their nature should require least maintenance

19 Criteria Evaluation > Each option scored on a scale of 1-10 > Each criteria equally weighted > Scores for water and power were directly based on the savings achievable compared with co-disposal > Score for the capital cost based on the price rise expected > Maintenance score was based on expected maintenance costs > Maintenance and capital costs evaluated based on inverse

20 Comparison Matrix Water Power Capital Maintenance Total Consumption Consumption Cost Filter Presses Vacuum Filters Belt Press filters Deep Cone Thickener

21 Paste thickeners operate in a similar manner to conventional high rate thickeners but produce an underflow of paste consistency by: [Bedell et. A. UWA] > Selecting the appropriate flocculant > Using feed dilution systems > Using a deep tank for compression > Allowing for long bed residence times > Using a tank cone > Using a specially designed rake system > Using shear thinning principles > Using a high degree of instrument and control Image courtesy of FLSmidth

22 Thickening Test work

23 Test Work by Outotec > Undertaken at Rio Tinto s Technology & Innovation Laboratory in Melbourne > Test Equipment Outotec s Supaflo High Rate Thickener 94 mm Diameter 190 mm Diameter > Test Material Blair Athol Coal Tailings SG: 1.7 Quantity: 16 bulky bins

24 Test Work by Outotec > 94 mm Φ Test Method Bed Height: 220mm Rake Speed: 2.5 rpm Stock slurry: Stored in 40 L agitated, baffled tub Feed sent via variable speed peristaltic pump Underflow pumped put by positive displacement pump > Flocculant Screening (94 mm Φ Test Method) Ciba Flocculants Magnafloc X110, X125, 336, 1011 & 5250 Best settling performance by 1011, hence Magnafloc 1011 was selected for thickening test work

25 Test Work by Outotec > 190 mm Φ Test Method Bed Height: 220mm Rake Speed: 2.5 rpm Stock slurry: Stored in 2m 3 agitated tank and fed at % w/w Feed sent via variable speed peristaltic pump Underflow pumped put by positive displacement pump > To achieve an underflow solids density of 50% w/w, a solids loading rate of 0.23 t/m2h and flocculant dosage rate of 20 g/t were ideal conditions as seen in Run 2.

26 Dynamic Thickening (190 mm Φ) Results Run 1 > Solids Loading Target Rate: 0.31 t/m 2 h Actual Rate: 0.30 t/m 2 h > Underflow Density Calculated Density: 48 % w/w Actual Density: 47% w/w > Flocculant Dosing Target Rate: 30 g/t Actual Rate: 31 g/t

27 Dynamic Thickening (190 mm Φ) Results Run 2 > Solids Loading Target Rate: 0.23 t/m 2 h Actual Rate: 0.24 t/m 2 h > Underflow Density Calculated Density: 50% w/w After Feed Interruption: 57% > Flocculant Dosing Target Rate: 20 g/t Actual Rate: 19 g/t

28 Dynamic Thickening (190 mm Φ) Results Run 3 > Solids Loading Target Rate: 0.31 t/m 2 h Actual Rate: 0.32 t/m 2 h > Underflow Density Calculated Density: 47 % w/w Actual Density: 46.6% w/w > Flocculant Dosing Target Rate: 20 g/t Actual Rate: 19 g/t

29 Construction Activities

30 ST201 ( ROM Feed Bin & Apron Feeder)

31 Crushing Station ST201

32 CPP & Portion of OLC

33 CPP

34 END