XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1411
On a microscopic scale, coal lithotypes correlate
with mineral matter distribution, influencing washability
(Figure 12). The composition, texture, and particle size dis-
tribution are crucial microscopic characteristics affecting
coal quality.
In the context of coal, mineral content, expressed as
ash content, affects overall coal quality and performance as
a fuel. Macroscopic characteristics such as density, porosity,
hardness, and wettability also influence washability. Coal
washing relies on density differences, and hydrophobic
fine coal may be less responsive to water-based separation
methods.
According to the study on washability in South East
British Columbia (SE BC) coals seams in 1994 (Holuszko,
1994), the variation of washability characteristics is highly
variable depending on the stratigraphy of the seam. Raw ash
content of the 33 seams from SE BC studied in 1994 var-
ied from 8.37% to 51.12% for run-of-mine coal while the
yield of clean coal at 10% ash (final product ash%) ranged
from 23.9% to 100%. The average near-gravity material at
separation for 10% ash clean coal product was on average
8.92%, which indicated easy-to-clean coals. Near-gravity
material represents particles with specific gravities or densi-
ties (SG) close to that of coal.
In the context of coal, mineral content can also be
expressed as “ash content” and refers to the inorganic residue
left behind after the combustion or burning of coal. During
combustion, the organic part (carbon) combusts and leaves
behind the inorganic minerals and impurities. Coal’s ash
content is a critical parameter as it affects its quality and
performance when used as a fuel. The ash content is usually
expressed as a percentage of the weight of the coal sample.
Higher ash content implies a greater amount of inorganic
minerals, which can have several implications.
Holuszko (1994) demonstrated that variability in
washability characteristics is influenced by lateral and
stratigraphic differences, with seam lithology playing a
crucial role. The bright lithotype (B) layers exhibit optimal
washability, while the Banded Dull (BD) lithotype, charac-
terized by high ash content, shows the lowest washability.
Sheared coal, despite its high ash content, displays better
washability than the BD lithotype with high ash content.
The seam’s composition becomes a significant factor in
determining washability outcomes. Lithotypes also differ
in hardness based on petrographic composition, mineral
content, and shearing degree.
Bright coals, rich in vitrinite, contribute to high fines
quantities due to their friability, with vitrain being the most
friable. The seam lithology affects the particle size distri-
bution of mined coal. Particle size distribution along with
washability, particularly for coarse and coarser fine coal,
are crucial factors influencing the ease of washing at the
Figure 1. Correlation between Seam lithology, lithotypes and mineral and maceral
composition (reproduced from Holuszko, 1994)
On a microscopic scale, coal lithotypes correlate
with mineral matter distribution, influencing washability
(Figure 12). The composition, texture, and particle size dis-
tribution are crucial microscopic characteristics affecting
coal quality.
In the context of coal, mineral content, expressed as
ash content, affects overall coal quality and performance as
a fuel. Macroscopic characteristics such as density, porosity,
hardness, and wettability also influence washability. Coal
washing relies on density differences, and hydrophobic
fine coal may be less responsive to water-based separation
methods.
According to the study on washability in South East
British Columbia (SE BC) coals seams in 1994 (Holuszko,
1994), the variation of washability characteristics is highly
variable depending on the stratigraphy of the seam. Raw ash
content of the 33 seams from SE BC studied in 1994 var-
ied from 8.37% to 51.12% for run-of-mine coal while the
yield of clean coal at 10% ash (final product ash%) ranged
from 23.9% to 100%. The average near-gravity material at
separation for 10% ash clean coal product was on average
8.92%, which indicated easy-to-clean coals. Near-gravity
material represents particles with specific gravities or densi-
ties (SG) close to that of coal.
In the context of coal, mineral content can also be
expressed as “ash content” and refers to the inorganic residue
left behind after the combustion or burning of coal. During
combustion, the organic part (carbon) combusts and leaves
behind the inorganic minerals and impurities. Coal’s ash
content is a critical parameter as it affects its quality and
performance when used as a fuel. The ash content is usually
expressed as a percentage of the weight of the coal sample.
Higher ash content implies a greater amount of inorganic
minerals, which can have several implications.
Holuszko (1994) demonstrated that variability in
washability characteristics is influenced by lateral and
stratigraphic differences, with seam lithology playing a
crucial role. The bright lithotype (B) layers exhibit optimal
washability, while the Banded Dull (BD) lithotype, charac-
terized by high ash content, shows the lowest washability.
Sheared coal, despite its high ash content, displays better
washability than the BD lithotype with high ash content.
The seam’s composition becomes a significant factor in
determining washability outcomes. Lithotypes also differ
in hardness based on petrographic composition, mineral
content, and shearing degree.
Bright coals, rich in vitrinite, contribute to high fines
quantities due to their friability, with vitrain being the most
friable. The seam lithology affects the particle size distri-
bution of mined coal. Particle size distribution along with
washability, particularly for coarse and coarser fine coal,
are crucial factors influencing the ease of washing at the
Figure 1. Correlation between Seam lithology, lithotypes and mineral and maceral
composition (reproduced from Holuszko, 1994)