XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1419
Seam B composites and was at 76% and 63% for the two
Seam C composites, respectively. The Seam A composites
were above 80%. Coal showed the highest liberated val-
ues in the ‘fines’ (–300µm material) for all the composites
when considering the distribution of coal and the mineral/
ash components in the different size fractions. All Seam A
and C composites showed higher than 50% overall coal
liberation in the –300µm fractions which should be recov-
erable through flotation. The strongest binary association
of coal with kaolinite was also noted in the –300µm sized
fractions and the highest values were noted in Seam B com-
posites, at 18% and 14% overall, respectively.
Coal liberation is compared against the washability
number and ash content in the clean coal in Table 5 and
correlated in Figure 10 and Figure 11. The percent liber-
ated coal and clean coal ash content are strongly correlated
at R2 of 0.84. All samples, except for Seam A sample 2,
showed a strong correlation between the percent liberated
coal and the washability number (Figure 11) with similar
trends. The ash content was confirmed by the automated
mineralogy measurements for all samples. The discrepancy
noted for Seam A sample 1 reflects a non-representative
split taken for the measurements.
CONCLUSIONS
The evaluation of washability data, coal particle size dis-
tributions, and clay characterization yielded several key
findings. The use of Wn (washability number) emerged
as a promising proxy for predicting coal washability, dem-
onstrating a 70% success rate in predicting washability
properties of raw coal. However, for the remaining 30%
of samples not conforming to Wn predictions, additional
analysis, such as particle size distribution (PSD) with clay
characterization, proved necessary for accurate washability
prediction.
The PSD study highlighted significant differences in
sheared coal from Seam B, particularly in the flotation
range (300μm and 100μm), showing higher amounts of
very fine coal. Seam B also exhibited a higher proportion
Figure 8. Coal liberation and association of the feed coal composites (at 10% tolerance). Sil =silicates (mainly quartz and
muscovite-illite-smectite) Kaol =kaolinite Phos&Carb =phosphates and carbonates Sulph =sulphides (mostly pyrite) Tern
=complex/multiple mineral particles. The washability number is shown on the secondary Y-axis
Seam B composites and was at 76% and 63% for the two
Seam C composites, respectively. The Seam A composites
were above 80%. Coal showed the highest liberated val-
ues in the ‘fines’ (–300µm material) for all the composites
when considering the distribution of coal and the mineral/
ash components in the different size fractions. All Seam A
and C composites showed higher than 50% overall coal
liberation in the –300µm fractions which should be recov-
erable through flotation. The strongest binary association
of coal with kaolinite was also noted in the –300µm sized
fractions and the highest values were noted in Seam B com-
posites, at 18% and 14% overall, respectively.
Coal liberation is compared against the washability
number and ash content in the clean coal in Table 5 and
correlated in Figure 10 and Figure 11. The percent liber-
ated coal and clean coal ash content are strongly correlated
at R2 of 0.84. All samples, except for Seam A sample 2,
showed a strong correlation between the percent liberated
coal and the washability number (Figure 11) with similar
trends. The ash content was confirmed by the automated
mineralogy measurements for all samples. The discrepancy
noted for Seam A sample 1 reflects a non-representative
split taken for the measurements.
CONCLUSIONS
The evaluation of washability data, coal particle size dis-
tributions, and clay characterization yielded several key
findings. The use of Wn (washability number) emerged
as a promising proxy for predicting coal washability, dem-
onstrating a 70% success rate in predicting washability
properties of raw coal. However, for the remaining 30%
of samples not conforming to Wn predictions, additional
analysis, such as particle size distribution (PSD) with clay
characterization, proved necessary for accurate washability
prediction.
The PSD study highlighted significant differences in
sheared coal from Seam B, particularly in the flotation
range (300μm and 100μm), showing higher amounts of
very fine coal. Seam B also exhibited a higher proportion
Figure 8. Coal liberation and association of the feed coal composites (at 10% tolerance). Sil =silicates (mainly quartz and
muscovite-illite-smectite) Kaol =kaolinite Phos&Carb =phosphates and carbonates Sulph =sulphides (mostly pyrite) Tern
=complex/multiple mineral particles. The washability number is shown on the secondary Y-axis