1410 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
BACKGROUND
One metallurgical coal producer faced challenges regarding
coal quality when mining certain seams. This predicament
has adversely impacted the processing of fine coal, starting
from the pit to the final stages of coal drying. Despite oper-
ational success in blending difficult-to-process coal with
easier-to-clean counterparts, the process remains largely
trial-and-error, leading to inconsistencies in plant perfor-
mance and product quality.
Coal processing at coal operations is typically initi-
ated with blending and crushing in the rotary breaker, then
progresses through wet screens, gravity separation in heavy
media cyclones, and water-only cyclones, and then the fine
coal is treated in flotation cells. The presence of oxidized
or difficult-to-wash coal, along with clay-like minerals, can
impede the flotation process, resulting in thickener over-
loading and discarding clean coal to tailings. These chal-
lenges contribute to an array of plant performance issues,
including high ash content in the various products, incon-
sistent operation, and difficulties in achieving desired yield
targets and ash quality in the final product. Coal yield refers
to the percentage of coal recovered from the raw coal feed
after undergoing a washing or cleaning process. Coal wash-
ing is a method used to remove impurities such as ash, sul-
phur, and rock, from raw coal to improve its quality and
meet specific market requirements. The coal yield is calcu-
lated by dividing the mass of the cleaned coal product by
the mass of the raw coal feed and then multiplying by 100
to express the result as a percentage.
The need for proactive measures was recognized and
thus a research project was initiated with the primary goal
to allow prediction of coal seam quality well before it enters
the processing plant. The project aimed to develop tools or
methodologies to efficiently identify difficult-to-wash coal
seams during the exploration stage to aid geologists in mine
planning. The ultimate objective was to prevent the trial-
and-error blending approach and its consequential impact
on processing plant operations. The project also explored
alternative solutions, considering the possibility of under-
standing and mitigating the effects of poor-quality coal
immediately before entering the processing plant, empha-
sizing a comprehensive examination of critical circuits like
flotation. The sub-objectives and milestones of the project
were designed to delve into the washability characteristics
of challenging seams, seeking insights to predict coal qual-
ity before processing, ultimately enhancing the efficiency
and reliability of coal processing.
OBJECTIVES
The focus of the study consisted of a comprehensive char-
acterization of challenging coal seams with several key sub-
objectives including:
Study washability data from exploration-stage reverse
circulation drilling (RC) chip samples
Investigate coal size distribution for ultrafine coal
content
Identify and characterize the types and occurrences
of clays in problematic seams
Development of predictive tools for more difficult-
to-wash coal
The initial phase of the project addressed the first three sub-
objectives, presenting results on washability data from bulk
and RC chip samples, particle size distribution data, and
identification of clay minerals using novel approaches. The
methodologies employed during the study will be reviewed
with sub-objectives that include a review on clay identifica-
tion methodologies by Fourier Transform Infrared (FTIR)
spectroscopy and data analysis provided by the geology
team. Based on the results from the characterization part
of the project, the development of the predictive tools set is
also elaborated on.
INTRODUCTION
The coal processing procedure involves cleaning raw coal
through physical separation methods, primarily gravity-
based techniques. It addresses essential factors like mineral
content, particle size, and moisture by employing processes
such as breaking, crushing, classification, gravity separation
for larger sizes, and flotation for fine coal cleaning. Western
Canadian coals, especially metallurgical coal, often contain
a high percentage of fines due to their friable nature.
This study emphasizes that excessive fines can result
from inherent coal characteristics or degradation during
mining or processing. Washability, a measure of how eas-
ily coal can be washed, is crucial for predicting clean coal
yield and ash content, indicating coal quality. It involves
float-and-sink analysis at different separation densities for
various size ranges, providing insights into the theoretical
outcomes of gravity-based cleaning processes.
The ease of coal washing is influenced by the quantity,
type, and association of minerals with coal. Coal petrogra-
phy and associated mineralogy affect both coal washability
and floatability. Flotation, influenced by coal’s hydropho-
bicity, is more effective for higher-rank coals. Clays and
sheared coal strata can complicate washability and float-
ability, impacting clean coal quality. Shearing refers to areas
of coal seams affected by faulting or structural deformation.
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1410 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
BACKGROUND
One metallurgical coal producer faced challenges regarding
coal quality when mining certain seams. This predicament
has adversely impacted the processing of fine coal, starting
from the pit to the final stages of coal drying. Despite oper-
ational success in blending difficult-to-process coal with
easier-to-clean counterparts, the process remains largely
trial-and-error, leading to inconsistencies in plant perfor-
mance and product quality.
Coal processing at coal operations is typically initi-
ated with blending and crushing in the rotary breaker, then
progresses through wet screens, gravity separation in heavy
media cyclones, and water-only cyclones, and then the fine
coal is treated in flotation cells. The presence of oxidized
or difficult-to-wash coal, along with clay-like minerals, can
impede the flotation process, resulting in thickener over-
loading and discarding clean coal to tailings. These chal-
lenges contribute to an array of plant performance issues,
including high ash content in the various products, incon-
sistent operation, and difficulties in achieving desired yield
targets and ash quality in the final product. Coal yield refers
to the percentage of coal recovered from the raw coal feed
after undergoing a washing or cleaning process. Coal wash-
ing is a method used to remove impurities such as ash, sul-
phur, and rock, from raw coal to improve its quality and
meet specific market requirements. The coal yield is calcu-
lated by dividing the mass of the cleaned coal product by
the mass of the raw coal feed and then multiplying by 100
to express the result as a percentage.
The need for proactive measures was recognized and
thus a research project was initiated with the primary goal
to allow prediction of coal seam quality well before it enters
the processing plant. The project aimed to develop tools or
methodologies to efficiently identify difficult-to-wash coal
seams during the exploration stage to aid geologists in mine
planning. The ultimate objective was to prevent the trial-
and-error blending approach and its consequential impact
on processing plant operations. The project also explored
alternative solutions, considering the possibility of under-
standing and mitigating the effects of poor-quality coal
immediately before entering the processing plant, empha-
sizing a comprehensive examination of critical circuits like
flotation. The sub-objectives and milestones of the project
were designed to delve into the washability characteristics
of challenging seams, seeking insights to predict coal qual-
ity before processing, ultimately enhancing the efficiency
and reliability of coal processing.
OBJECTIVES
The focus of the study consisted of a comprehensive char-
acterization of challenging coal seams with several key sub-
objectives including:
Study washability data from exploration-stage reverse
circulation drilling (RC) chip samples
Investigate coal size distribution for ultrafine coal
content
Identify and characterize the types and occurrences
of clays in problematic seams
Development of predictive tools for more difficult-
to-wash coal
The initial phase of the project addressed the first three sub-
objectives, presenting results on washability data from bulk
and RC chip samples, particle size distribution data, and
identification of clay minerals using novel approaches. The
methodologies employed during the study will be reviewed
with sub-objectives that include a review on clay identifica-
tion methodologies by Fourier Transform Infrared (FTIR)
spectroscopy and data analysis provided by the geology
team. Based on the results from the characterization part
of the project, the development of the predictive tools set is
also elaborated on.
INTRODUCTION
The coal processing procedure involves cleaning raw coal
through physical separation methods, primarily gravity-
based techniques. It addresses essential factors like mineral
content, particle size, and moisture by employing processes
such as breaking, crushing, classification, gravity separation
for larger sizes, and flotation for fine coal cleaning. Western
Canadian coals, especially metallurgical coal, often contain
a high percentage of fines due to their friable nature.
This study emphasizes that excessive fines can result
from inherent coal characteristics or degradation during
mining or processing. Washability, a measure of how eas-
ily coal can be washed, is crucial for predicting clean coal
yield and ash content, indicating coal quality. It involves
float-and-sink analysis at different separation densities for
various size ranges, providing insights into the theoretical
outcomes of gravity-based cleaning processes.
The ease of coal washing is influenced by the quantity,
type, and association of minerals with coal. Coal petrogra-
phy and associated mineralogy affect both coal washability
and floatability. Flotation, influenced by coal’s hydropho-
bicity, is more effective for higher-rank coals. Clays and
sheared coal strata can complicate washability and float-
ability, impacting clean coal quality. Shearing refers to areas
of coal seams affected by faulting or structural deformation.

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