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Determination
and use of
washability curves
SACPSSACPS
Vryheid Golf ClubVryheid Golf Club
24 May 200624 May 2006
1. Principles
2. Sampling
3. Float & Sink
4. Analysis
5. Calculation
6. Plotting of washability curves
7. Use of washability curves
Washability curves
• 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
Sampling: Minimum sample mass
0.5- 0.51.0- 2 + 0.51.5- 4 + 23- 8 + 47-16 + 8
25- 31.5 + 16100- 63 + 31.5400- 125 + 63
Minimum mass (kg)Nominal size (mm)
AS 1661-1979 (Figures valid for raw coal)
Float & Sink analysis
Typical ‘heavy liquids’ used in laboratory:
• Zinc Chloride
• Bromoform
• TBE (Tetra Bromo Ethane)
Float & Sink tank
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
Float & Sink analysis : Procedure
1. Design of coal processing plants
2. Techno-economic evaluations
3. Reserve estimation
4. Plant efficiency testing
5. Day-to-day plant control
Washability curves: Uses
% of material within +0,10 and -0,10 interval
at any specific density
Near-dense material
Washability Analysis : No. 5 Seam
Fractional Cumulative Rel.Dens.
Yield Ash Yield Ash
F @ 1.30 16.4 4.1 16.4 4.1F @ 1.35 15.5 7.0 31.9 5.5F @ 1.40 3.9 13.1 35.8 6.3F @ 1.45 3.3 19.3 39.1 7.4F @ 1.50 1.1 23.2 40.2 7.9F @ 1.55 1.0 31.2 41.2 8.4F @ 1.60 0.8 34.9 42.0 8.9F @ 1.65 1.0 40.1 43.0 9.7F @ 1.70 1.2 42.9 44.2 10.6F @ 1.75 1.0 47.8 45.2 11.4F @ 1.80 1.0 49.7 46.2 12.2F @ 1.85 0.4 51.6 46.6 12.6F @ 1.90 0.4 51.8 47.0 12.9F @ 1.95 1.0 61.1 48.0 13.9F @ 2.00 0.9 69.7 48.9 14.9S @ 2.00 51.1 76.9 100.0 46.6
Washability Analysis : No. 2 Seam
Fractional CumulativeRel.Dens.
Yield Ash Yield Ash
F @ 1.30 9.88 4.9 9.88 4.9F @ 1.35 15.71 6.9 25.59 6.1F @ 1.40 16.65 9.7 42.24 7.5F @ 1.45 13.72 14.8 55.96 9.3F @ 1.50 10.49 18.8 66.45 10.8F @ 1.55 7.47 22.9 73.92 12.0F @ 1.60 5.66 29.0 79.58 13.2F @ 1.65 3.66 36.6 83.24 14.3F @ 1.70 2.77 40.6 86.01 15.1F @ 1.75 2.46 45.3 88.47 16.0F @ 1.80 2.85 48.9 91.32 17.0F @ 1.85 1.19 51.4 92.51 17.4F @ 1.90 0.5 53.3 93.00 17.6F @ 1.95 0.8 57.9 93.80 18.0F @ 2.00 0.5 63.9 94.32 18.2
S @ 2.00 5.7 79.1 100.00 21.7
‘False’ middling
Coal
Shale
‘Liberation’ by crushing
CoalShale
Washability data - Dolan Colliery
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Cumulative Ash %
Cum
ulat
ive
Yie
ld %
Coarse Small
Washability data - Dolan Colliery
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Cumulative Ash %
Cum
ulat
ive
Yie
ld %
Coarse Small
Washability data - Dolan Colliery
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Cumulative Ash %
Cum
ulat
ive
Yie
ld %
Coarse Small
Plant Efficiency
• Acceptance test
• Routine checks
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
Feed
Product
Discard
Plant Efficiency Testing
Feed
Product
Discard
Plant Efficiency Testing
32 increments
Ash content
Feed
Product
Discard
Plant Efficiency Testing
16 increments
Washability
analysis
Feed
Product
Discard
Plant Efficiency Testing
16 increments
Washability
analysis
(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 %
Plant Efficiency
