1416 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
These curves are usually used to show how easy it is to wash
to the target ash content and is an indication of coal libera-
tion. In the context of coal washability curves, liberation
specifically relates to the separation of coal from its associ-
ated impurities, such as ash-forming minerals. Achieving
high liberation is crucial for efficient coal processing. It
impacts the efficiency of separation processes like coal
washing, where the goal is to remove impurities and leave
behind a cleaner coal product. The washability curves help
identify the range of specific gravity values where the bulk
of coal and ash separation occurs. The steeper the slope of
a curve in a particular region, the more effective the sepa-
ration of coal and ash at that specific gravity. The curves
are also used to indicate the quality of the rejects in terms
of ash.
The washability data presented in Figures 5, and 6,
clearly illustrates that finer fractions are characterized by
better washability characteristics than their coarser coun-
terparts. The variability in the washing characteristics is
evident even for the coal samples from the same seam. The
difference in yield of clean coal at 10% ash could be as high
as 20% for coarse coal as shown in Figure 5.
It is difficult using classical washability curves to make
comparisons between these various coals, as there are multi-
ple parameters to consider. For this reason, other parameters
such as single Wn that could be derived from float-and-sink
are preferred for evaluation or compare just one parameter
such as clean coal curves and rejects as shown in Figure 5
and Figure 6.
Mineral Matter in Coal and Clay Minerals
Characterization
Micro-FTIR Analysis of Clays and Other Minerals
Associated With Coal
The major clay minerals, kaolinite and illite were easily
identified by XRD and FTIR and mapped for identifica-
tion on the coal surface. Kaolinite is the mineral that was
easily detected by FTIR by using the Mg/Al-OH bond
(700–686 cm–1), Al-OH bond (918 cm–1) and -OH bond
(3840 cm–1, Figure 7a). Illite was identified by the pres-
ence of Si-O-Si bond (1120, 1025 cm–1) and can be dis-
tinguished from kaolinite and calcite on the micro-FTIR
spectra (Figure 7b).
Quartz can be identified and located by the absorption
peaks at 815–805 cm–1 and 1510–1505 cm–1 where the
Si-O-Si bonds are located. Quartz can be recognized by a
doublet centered at 796 cm–1 and 778 cm–1 [Ramasamy
and Suresh, 2009]. Therefore, the υ (Si-O-Si) and the δ (Si-
O) bands confirm the presence of quartz [Nayak and Singh,
Figure 5. Clean coal curves for Seam A coarse coal baseline (orange) and other coarse coal from the same
seam (red line indicates 10% clean coal product)
These curves are usually used to show how easy it is to wash
to the target ash content and is an indication of coal libera-
tion. In the context of coal washability curves, liberation
specifically relates to the separation of coal from its associ-
ated impurities, such as ash-forming minerals. Achieving
high liberation is crucial for efficient coal processing. It
impacts the efficiency of separation processes like coal
washing, where the goal is to remove impurities and leave
behind a cleaner coal product. The washability curves help
identify the range of specific gravity values where the bulk
of coal and ash separation occurs. The steeper the slope of
a curve in a particular region, the more effective the sepa-
ration of coal and ash at that specific gravity. The curves
are also used to indicate the quality of the rejects in terms
of ash.
The washability data presented in Figures 5, and 6,
clearly illustrates that finer fractions are characterized by
better washability characteristics than their coarser coun-
terparts. The variability in the washing characteristics is
evident even for the coal samples from the same seam. The
difference in yield of clean coal at 10% ash could be as high
as 20% for coarse coal as shown in Figure 5.
It is difficult using classical washability curves to make
comparisons between these various coals, as there are multi-
ple parameters to consider. For this reason, other parameters
such as single Wn that could be derived from float-and-sink
are preferred for evaluation or compare just one parameter
such as clean coal curves and rejects as shown in Figure 5
and Figure 6.
Mineral Matter in Coal and Clay Minerals
Characterization
Micro-FTIR Analysis of Clays and Other Minerals
Associated With Coal
The major clay minerals, kaolinite and illite were easily
identified by XRD and FTIR and mapped for identifica-
tion on the coal surface. Kaolinite is the mineral that was
easily detected by FTIR by using the Mg/Al-OH bond
(700–686 cm–1), Al-OH bond (918 cm–1) and -OH bond
(3840 cm–1, Figure 7a). Illite was identified by the pres-
ence of Si-O-Si bond (1120, 1025 cm–1) and can be dis-
tinguished from kaolinite and calcite on the micro-FTIR
spectra (Figure 7b).
Quartz can be identified and located by the absorption
peaks at 815–805 cm–1 and 1510–1505 cm–1 where the
Si-O-Si bonds are located. Quartz can be recognized by a
doublet centered at 796 cm–1 and 778 cm–1 [Ramasamy
and Suresh, 2009]. Therefore, the υ (Si-O-Si) and the δ (Si-
O) bands confirm the presence of quartz [Nayak and Singh,
Figure 5. Clean coal curves for Seam A coarse coal baseline (orange) and other coarse coal from the same
seam (red line indicates 10% clean coal product)