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