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
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