Wash Ability Curves

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Determination and use of washability curves

SACPS Vryheid Golf Club 24 May 2006

Washability curves1. 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 massNominal size (mm) - 125 + 63 - 63 + 31.5 - 31.5 + 16 -16 + 8 -8+4 -4+2 - 2 + 0.5 - 0.5AS 1661-1979 (Figures valid for raw coal)

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

Float & Sink analysisTypical heavy liquids used in laboratory: Zinc Chloride Bromoform TBE (Tetra Bromo Ethane)

Float & Sink tank

Float & Sink analysis : Procedure1. 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: Uses1. 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 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

Cumulative 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 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

Cumulative 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 Colliery100.0 90.0 80.0

Cumulative Yield %

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 25.0 30.0

Cumulative Ash %Coarse Small

Washability data - Dolan Colliery100.0 90.0 80.0

Cumulative Yield %

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 25.0 30.0

Cumulative Ash %Coarse Small

Washability data - Dolan Colliery100.0 90.0 80.0

Cumulative Yield %

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 25.0 30.0

Cumulative Ash %Coarse Small

Plant Efficiency Acceptance test Routine checks

Plant Efficiency1. 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 Efficiency1. 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 TestingFeed

Product

Discard

Plant Efficiency TestingFeed

32 increments Ash content Product

Discard

Plant Efficiency TestingFeed

16 increments

Product Washability analysis

Discard

Plant Efficiency TestingFeed

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 EfficiencyOrganic efficiency = actual yield at actual ash content /theoretical yield at actual ash content x 100

Plant EfficiencyOrganic 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 %