2048 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
to achieve full dissociation, which is an effective means to
improve the clean coal yield and achieve the rational use of
coal.
The work mainly take Shendong long-flame coal with
low metamorphic degree as the research object, studied the
distribution and dissociation law of the coal and macerals
at different grinding time under the rod milling condition,
analyzed and determined the optimal grinding time of the
macerals, and its enrichment characteristics of the macerals
under the enhanced gravity field.
EXPERIMENTAL
Materials
Coal Sample
The raw coal below 50 mm came from Shenhua Group,
and the coal type is low-rank bituminous coal, which has
the characteristics of low ash, low sulphur, high volatile, and
high liquefaction activity. The coal samples were roughly
crushed to –3 mm by jaw crusher, screened by 1 mm sieve,
and crushed to 1 mm again by sealed hammer crusher. The
industrial, elemental, and macerals analyses of the coal sam-
ple are shown in Table 1.The coal sample has an ash content
of 9.26%, a sulphur content of 0.33%, a volatile content of
37.60%, and a hydrogen to carbon atom ratio of 0.71. The
macerals were dominated by vitrinite and inertinite, with
vitrinite content of being 41.88% and inertinite content
of being 50.63%. Minerals are dominated by clay groups
and pyrite. It is necessary to further separate and enrich the
macerals to meet the coal quality requirements for coal-to-
oil production.
Particle Size and Density Composition
The particle size and density composition are shown in
Table 2 and Table 3respectively.From Table 2, the ash con-
tent is gradually reduced with the increase of particle size,
the particle size distribution of raw coal shows “two big
ends and small middle” trend, and the content of inter-
mediate particle size level is relatively less. The content of
coarse particle size of +0.125 mm accounted for half of the
raw coal yield, with a yield of 51.78% and a lower ash con-
tent of 6.98%. The yield and ash content of –0.045 mm are
Table 1. Industrial, elemental, and maceral analyses
Industrial Analysis, %Elemental Analysis, %Maceral Analysis, %
M
ad A
ad V
daf FC
daf C
daf H
daf O
daf N
daf S
daf Vitrinite Inertinite Exinite Mineral
3.21 9.26 37.60 62.40 78.30 4.65 15.73 0.99 0.33 41.88 50.63 1.25 6.25
Table 2. Particle size composition of raw coal
Size, mm Yield, %Ash, %
Cumulative on Sieve Cumulative Under Sieve
Yield, %Ash, %Yield, %Ash, %
0.5–0.25 27.89 6.64 27.89 6.64 100.00 9.26
0.25–0.125 23.90 7.37 51.78 6.98 72.11 10.27
0.125–0.074 9.54 7.92 61.33 7.13 48.22 11.71
0.074–0.045 10.54 8.45 71.87 7.32 38.67 12.65
–0.045 28.13 14.22 100.00 9.26 28.13 14.22
Total 100 9.26
Table 3. Density composition of raw coal
Density (g/cm3) Yield, %Ash, %
Cumulative on Sieve Cumulative Under Sieve
Yield, %Ash, %Yield, %Ash, %
–1.30 23.22 1.64 23.22 1.64 100.00 9.55
1.30–1.33 8.09 1.63 31.31 1.64 76.78 11.94
1.33–1.35 10.75 1.99 42.06 1.73 68.69 13.15
1.35–1.40 20.03 3.39 62.09 2.27 57.94 15.23
1.40–1.45 17.78 4.10 79.87 2.68 37.91 21.48
1.45–1.50 4.60 6.97 84.47 2.91 20.13 36.83
1.50–1.55 3.87 9.52 88.34 3.20 15.53 45.68
+1.55 11.66 57.47 100.00 9.55 11.66 57.67
Total 100.00 9.29

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Extracted Text (may have errors)

2048 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
to achieve full dissociation, which is an effective means to
improve the clean coal yield and achieve the rational use of
coal.
The work mainly take Shendong long-flame coal with
low metamorphic degree as the research object, studied the
distribution and dissociation law of the coal and macerals
at different grinding time under the rod milling condition,
analyzed and determined the optimal grinding time of the
macerals, and its enrichment characteristics of the macerals
under the enhanced gravity field.
EXPERIMENTAL
Materials
Coal Sample
The raw coal below 50 mm came from Shenhua Group,
and the coal type is low-rank bituminous coal, which has
the characteristics of low ash, low sulphur, high volatile, and
high liquefaction activity. The coal samples were roughly
crushed to –3 mm by jaw crusher, screened by 1 mm sieve,
and crushed to 1 mm again by sealed hammer crusher. The
industrial, elemental, and macerals analyses of the coal sam-
ple are shown in Table 1.The coal sample has an ash content
of 9.26%, a sulphur content of 0.33%, a volatile content of
37.60%, and a hydrogen to carbon atom ratio of 0.71. The
macerals were dominated by vitrinite and inertinite, with
vitrinite content of being 41.88% and inertinite content
of being 50.63%. Minerals are dominated by clay groups
and pyrite. It is necessary to further separate and enrich the
macerals to meet the coal quality requirements for coal-to-
oil production.
Particle Size and Density Composition
The particle size and density composition are shown in
Table 2 and Table 3respectively.From Table 2, the ash con-
tent is gradually reduced with the increase of particle size,
the particle size distribution of raw coal shows “two big
ends and small middle” trend, and the content of inter-
mediate particle size level is relatively less. The content of
coarse particle size of +0.125 mm accounted for half of the
raw coal yield, with a yield of 51.78% and a lower ash con-
tent of 6.98%. The yield and ash content of –0.045 mm are
Table 1. Industrial, elemental, and maceral analyses
Industrial Analysis, %Elemental Analysis, %Maceral Analysis, %
M
ad A
ad V
daf FC
daf C
daf H
daf O
daf N
daf S
daf Vitrinite Inertinite Exinite Mineral
3.21 9.26 37.60 62.40 78.30 4.65 15.73 0.99 0.33 41.88 50.63 1.25 6.25
Table 2. Particle size composition of raw coal
Size, mm Yield, %Ash, %
Cumulative on Sieve Cumulative Under Sieve
Yield, %Ash, %Yield, %Ash, %
0.5–0.25 27.89 6.64 27.89 6.64 100.00 9.26
0.25–0.125 23.90 7.37 51.78 6.98 72.11 10.27
0.125–0.074 9.54 7.92 61.33 7.13 48.22 11.71
0.074–0.045 10.54 8.45 71.87 7.32 38.67 12.65
–0.045 28.13 14.22 100.00 9.26 28.13 14.22
Total 100 9.26
Table 3. Density composition of raw coal
Density (g/cm3) Yield, %Ash, %
Cumulative on Sieve Cumulative Under Sieve
Yield, %Ash, %Yield, %Ash, %
–1.30 23.22 1.64 23.22 1.64 100.00 9.55
1.30–1.33 8.09 1.63 31.31 1.64 76.78 11.94
1.33–1.35 10.75 1.99 42.06 1.73 68.69 13.15
1.35–1.40 20.03 3.39 62.09 2.27 57.94 15.23
1.40–1.45 17.78 4.10 79.87 2.68 37.91 21.48
1.45–1.50 4.60 6.97 84.47 2.91 20.13 36.83
1.50–1.55 3.87 9.52 88.34 3.20 15.53 45.68
+1.55 11.66 57.47 100.00 9.55 11.66 57.67
Total 100.00 9.29

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2047
Study on the Dissociation Characteristics of Low-rank Coal
Macerals and Enhanced Gravity Separation
Youjun Tao, Xuebin Zhang, Zhongxian Wu
Key Laboratory of Coal Processing and Efficient Utilization of Ministry of Education, China University of Mining and
Technology, Xuzhou, Jiangsu, China
School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, Jiangsu, China
ABSTRACT: The work carried out grinding tests using rod mill and enhanced gravity separation experiments
on the Shenhua low-rank coal macerals. With the increase of grinding time, the amount of 0.5–0.25 mm
particle size gradually decreases, while the amount of 0.25–0.125 mm particle size increases in a certain period
of time. When the grinding time tends to 30 min, the 0.5–0.25 mm particle size gradually disappears. The ash
of grinding product gradually decreases with the decreasing particle size, among which the ash of –0.045 mm
particle size shows the most reduction. When the grinding time is 10 min, the differences of yield and ash
content between the two density levels of –1.35 and +1.40g/cm3are the largest, which is conducive to the
enhanced gravity separation of the low-rank coal macerals. The enhanced gravity separation results of the low-
rank coal macerals after grinding show that under the optimal test conditions, the average vitrinite recovery
and enrichment ratio can reach 71.61% and 1.15, respectively, which provides a low-cost and high-efficiency
separation technology.
Keywords: Low-rank bituminous coal Macerals Rod milling Dissociation characteristics Enhanced gravity
separation
INTRODUCTION
China’s coal-dominated energy structure determines the
clean use of coal is the key to achieve a low-carbon econ-
omy (He et al., 2019), coal-to-oil is an important direction
of the clean use of coal (Ge et al., 2018).In the current
research of coal liquefaction technology, how to improve
the conversion rate of coal-to-oil and reduce the energy
consumption is the key (Chang et al., 2021).The macerals
composition has a huge impact on the oil recovery rate, and
it is generally agreed that the exinitehas the best reactiv-
ity, the vitrinite is in the middle, and inertiniteis the worst
(Onifade et al., 2021).
Generally speaking, vitrinite content in coal is the high-
est, reaching 40–80%,inertinitecontent is the next highest,
reaching 30–50%, and exinite content is the lowest, gener-
ally below 10%. Macerals are the basic constituent units of
coal, and various macerals have their special process char-
acteristics (Xian, Tao, and Ma 2021). To achieve efficient
and clean use of coal, it is necessary to make macerals effec-
tively separated and enriched. Crushing and dissociation of
macerals is the premise of separation and enrichment, and
only in the case of full dissociation of macerals, it is pos-
sible to maximize the enrichment (Yang et al., 2018). And
the method of grinding can make the coal and minerals

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Extracted Text (may have errors)

2047
Study on the Dissociation Characteristics of Low-rank Coal
Macerals and Enhanced Gravity Separation
Youjun Tao, Xuebin Zhang, Zhongxian Wu
Key Laboratory of Coal Processing and Efficient Utilization of Ministry of Education, China University of Mining and
Technology, Xuzhou, Jiangsu, China
School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, Jiangsu, China
ABSTRACT: The work carried out grinding tests using rod mill and enhanced gravity separation experiments
on the Shenhua low-rank coal macerals. With the increase of grinding time, the amount of 0.5–0.25 mm
particle size gradually decreases, while the amount of 0.25–0.125 mm particle size increases in a certain period
of time. When the grinding time tends to 30 min, the 0.5–0.25 mm particle size gradually disappears. The ash
of grinding product gradually decreases with the decreasing particle size, among which the ash of –0.045 mm
particle size shows the most reduction. When the grinding time is 10 min, the differences of yield and ash
content between the two density levels of –1.35 and +1.40g/cm3are the largest, which is conducive to the
enhanced gravity separation of the low-rank coal macerals. The enhanced gravity separation results of the low-
rank coal macerals after grinding show that under the optimal test conditions, the average vitrinite recovery
and enrichment ratio can reach 71.61% and 1.15, respectively, which provides a low-cost and high-efficiency
separation technology.
Keywords: Low-rank bituminous coal Macerals Rod milling Dissociation characteristics Enhanced gravity
separation
INTRODUCTION
China’s coal-dominated energy structure determines the
clean use of coal is the key to achieve a low-carbon econ-
omy (He et al., 2019), coal-to-oil is an important direction
of the clean use of coal (Ge et al., 2018).In the current
research of coal liquefaction technology, how to improve
the conversion rate of coal-to-oil and reduce the energy
consumption is the key (Chang et al., 2021).The macerals
composition has a huge impact on the oil recovery rate, and
it is generally agreed that the exinitehas the best reactiv-
ity, the vitrinite is in the middle, and inertiniteis the worst
(Onifade et al., 2021).
Generally speaking, vitrinite content in coal is the high-
est, reaching 40–80%,inertinitecontent is the next highest,
reaching 30–50%, and exinite content is the lowest, gener-
ally below 10%. Macerals are the basic constituent units of
coal, and various macerals have their special process char-
acteristics (Xian, Tao, and Ma 2021). To achieve efficient
and clean use of coal, it is necessary to make macerals effec-
tively separated and enriched. Crushing and dissociation of
macerals is the premise of separation and enrichment, and
only in the case of full dissociation of macerals, it is pos-
sible to maximize the enrichment (Yang et al., 2018). And
the method of grinding can make the coal and minerals

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2049
highest, which are 28.13 and 14.22% respectively, indicat-
ing that the raw coal has relatively more high ash and fine
mud content, which will affect the subsequent sorting of
macerals. From Table 3, the raw coal has more content of
low density grade material, and there are five density grades
with ash less than 5%, which are –1.30, 1.30–1.33, 1.33–
1.35, 1.35–1.40, and 1.4–1.45 g/cm3, and the sum of the
yields is 79.87%, of which +1.55 g/cm3 density grade con-
tent accounted for a larger proportion and higher ash con-
tent of 57.67%.
Analyses of Macerals Composition
BA310Pol type polarising microscope was used to deter-
mine the microscopic composition of low-rank bituminous
coal macerals. From Table 4, it can be seen that the macer-
als are dominated by the vitrinite and inertinite, with the
vitrinite content of being 41.88% and inertinite content
of being 50.63%, and the exinite has a low mass fraction
content of only 1.25%. Mineral mass fraction content is
6.25%, of which clay group accounts for 5% and sulphide
accounts for 1.25%.
The microscopic morphology of macerals is shown in
Figure 1. The vitrinite of Shenhua low-rank bituminous
coal is dominated by matrix specular bodies (cemented
hemifilaments, fragments of filaments, detrital inertia,
coarse-grained bodies, microsporangia, clay, pyrite, etc.)
(dark grey strips in Figure 1a), with occasional structural
specular bodies (the cellular cavities are elongated by extru-
sion and are mostly hollow, and a few of them are filled up
by clay) (Figure 1b).The inertinite is dominated by hemi-
filament bodies (Figure 1c), with a small amount of detrital
inertia and oxidised filament bodies (Figure 1d), followed
by coarse-grained bodies (Figure 1e) and occasional
Table 4. The petrographic analysis of low-rank coal sample
Macerals Constituents Percent, %Total, %
Vitrinite Telinite 0.63 41.88
Collinite 41.25
Inertinite Fusinite 3.13 50.63
Semifusinite 40.63
Macrinite 1.88
Micrinite 0.63
Inertodetrinite 4.38
Exinite Sporinite 1.25 1.25
Minerals Calcite, quartz, clay
minerals
6.25 6.25
Figure 1. The morphology of low-rank coal sample

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Extracted Text (may have errors)

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2049
highest, which are 28.13 and 14.22% respectively, indicat-
ing that the raw coal has relatively more high ash and fine
mud content, which will affect the subsequent sorting of
macerals. From Table 3, the raw coal has more content of
low density grade material, and there are five density grades
with ash less than 5%, which are –1.30, 1.30–1.33, 1.33–
1.35, 1.35–1.40, and 1.4–1.45 g/cm3, and the sum of the
yields is 79.87%, of which +1.55 g/cm3 density grade con-
tent accounted for a larger proportion and higher ash con-
tent of 57.67%.
Analyses of Macerals Composition
BA310Pol type polarising microscope was used to deter-
mine the microscopic composition of low-rank bituminous
coal macerals. From Table 4, it can be seen that the macer-
als are dominated by the vitrinite and inertinite, with the
vitrinite content of being 41.88% and inertinite content
of being 50.63%, and the exinite has a low mass fraction
content of only 1.25%. Mineral mass fraction content is
6.25%, of which clay group accounts for 5% and sulphide
accounts for 1.25%.
The microscopic morphology of macerals is shown in
Figure 1. The vitrinite of Shenhua low-rank bituminous
coal is dominated by matrix specular bodies (cemented
hemifilaments, fragments of filaments, detrital inertia,
coarse-grained bodies, microsporangia, clay, pyrite, etc.)
(dark grey strips in Figure 1a), with occasional structural
specular bodies (the cellular cavities are elongated by extru-
sion and are mostly hollow, and a few of them are filled up
by clay) (Figure 1b).The inertinite is dominated by hemi-
filament bodies (Figure 1c), with a small amount of detrital
inertia and oxidised filament bodies (Figure 1d), followed
by coarse-grained bodies (Figure 1e) and occasional
Table 4. The petrographic analysis of low-rank coal sample
Macerals Constituents Percent, %Total, %
Vitrinite Telinite 0.63 41.88
Collinite 41.25
Inertinite Fusinite 3.13 50.63
Semifusinite 40.63
Macrinite 1.88
Micrinite 0.63
Inertodetrinite 4.38
Exinite Sporinite 1.25 1.25
Minerals Calcite, quartz, clay
minerals
6.25 6.25
Figure 1. The morphology of low-rank coal sample