Wash Ability Curves

Determination and use of washability curves

SACPS Vryheid Golf Club 24 May 2006

Washability curves 1. Principles 2. Sampling 3. Float & Sink 4. Analysis 5. Calculation 6. Plotting of washability curves 7. Use of washability curves

Sampling • Standard prescribes minimum of 1000 ‘particles’ per size fraction and minimum 10 ‘particles’ per relative density fraction

• Approximate formula: • Sample mass ~ 5 x Average particle size

Sampling: Minimum sample mass Nominal size (mm) - 125 + 63 - 63 + 31.5 - 31.5 + 16 -16 + 8 -8+4 -4+2 - 2 + 0.5 - 0.5 AS 1661-1979 (Figures valid for raw coal)

Minimum mass (kg) 400 100 25 7 3 1.5 1.0 0.5

Float & Sink analysis Typical ‘heavy liquids’ used in laboratory: • Zinc Chloride • Bromoform • TBE (Tetra Bromo Ethane)

Float & Sink tank

Float & Sink analysis : Procedure 1. Make up correct densities in series of containers (test with hydrometer) 2. Place sample in container (start at lowest or highest rd depending on sample) 3. Remove floats, remove sinks 4. Remove dense liquids from floats and sinks – filtering and/or washing 5. Dry samples 6. Weigh and analyse samples 7. Calculate washability and plot curves

Washability curves: Uses 1. Design of coal processing plants 2. Techno-economic evaluations 3. Reserve estimation 4. Plant efficiency testing 5. Day-to-day plant control

Near-dense material % of material within +0,10 and -0,10 interval at any specific density

Washability Analysis :

No. 5 Seam

Fractional

Cumulative

Rel.Dens. Yield F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ S@

1.30 1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.00

16.4 15.5 3.9 3.3 1.1 1.0 0.8 1.0 1.2 1.0 1.0 0.4 0.4 1.0 0.9 51.1

Ash 4.1 7.0 13.1 19.3 23.2 31.2 34.9 40.1 42.9 47.8 49.7 51.6 51.8 61.1 69.7 76.9

Yield 16.4 31.9 35.8 39.1 40.2 41.2 42.0 43.0 44.2 45.2 46.2 46.6 47.0 48.0 48.9 100.0

Ash 4.1 5.5 6.3 7.4 7.9 8.4 8.9 9.7 10.6 11.4 12.2 12.6 12.9 13.9 14.9 46.6

Washability Analysis :

No. 2 Seam

Fractional

Cumulative

Rel.Dens. Yield F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ F@ S@

1.30 1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.00

9.88 15.71 16.65 13.72 10.49 7.47 5.66 3.66 2.77 2.46 2.85 1.19 0.5 0.8 0.5 5.7

Ash 4.9 6.9 9.7 14.8 18.8 22.9 29.0 36.6 40.6 45.3 48.9 51.4 53.3 57.9 63.9 79.1

Yield 9.88 25.59 42.24 55.96 66.45 73.92 79.58 83.24 86.01 88.47 91.32 92.51 93.00 93.80 94.32 100.00

Ash 4.9 6.1 7.5 9.3 10.8 12.0 13.2 14.3 15.1 16.0 17.0 17.4 17.6 18.0 18.2 21.7

‘False’ middling

Coal

Shale

‘Liberation’ by crushing

Coal Shale

Washability data - Dolan Colliery 100.0 90.0

Cumulative Yield %

80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 0.0

5.0

10.0

15.0

20.0

Cumulative Ash % Coarse

Small

25.0

30.0

Washability data - Dolan Colliery 100.0 90.0

Cumulative Yield %

80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 0.0

5.0

10.0

15.0

20.0

Cumulative Ash % Coarse

Small

25.0

30.0

Washability data - Dolan Colliery 100.0 90.0

Cumulative Yield %

80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 0.0

5.0

10.0

15.0

20.0

Cumulative Ash % Coarse

Small

25.0

30.0

Plant Efficiency • Acceptance test • Routine checks

Plant Efficiency 1. Test procedure & sampling 2. Interpretation of results 1. Ash balance method to determine yield 2. Plotting of Tromp (Partition) curve 3. EPM,Organic Efficiency, Misplaced material

Plant Efficiency 1. Samples taken of feed, product (floats) and discards (sinks) 2. Sample mass as per standard (~ 5 x ave particle size) 3. Number of increments = 32 (raw coal feed), 16 washed coal (product & discard) 4. Determine ash content of feed, washability analysis of product and discard

Plant Efficiency Testing Feed

Product

Discard

Plant Efficiency Testing Feed

32 increments Ash content

Product

Discard

Plant Efficiency Testing Feed

16 increments

Product Washability analysis

Discard

Plant Efficiency Testing Feed

Product

16 increments

Discard

Washability analysis

Plant Efficiency (discard ash – feed ash)

Ash balance:

% Yield = -----------------------------------

x 100

(discard ash – product ash)

Calculation of ‘partition curve’ Plotting of curve

Plant Efficiency Organic efficiency = actual yield at actual ash content /theoretical yield at actual ash content x 100

Plant Efficiency Organic efficiency = actual yield at actual ash content /theoretical yield at actual ash content x 100 example: Actual yield = 61,44 % (from ash balance) Theoretical yield = 61,63 % (from reconstituted feed washability) -> Organic efficiency = 61,44/61,63*100 = 99,7 %