RESEARCH ARTICLE
Catalytic effect of alkali and alkaline earth metals in
different occurrence modes in Zhundong coals
Dingcheng Liang
1
| Qiang Xie
1
| Huabing Zhou
1
| Mingshun Yang
1,2
| Junya Cao
1
|
Jun Zhang
1
1
School of Chemical and Environmental
Engineering, China University of Mining
and Technology (Beijing), D11 Xueyuan
Road, Haidian District, Beijing 100083,
China
2
Datang International Chemical
Technology Research Institute Co., Ltd.,
Beijing, China
Correspondence
Qiang Xie, School of Chemical and
Environmental Engineering, China
University of Mining and Technology
(Beijing), D11 Xueyuan Road, Haidian
District, Beijing 100083, China.
Email: dr‐xieq@cumtb.edu.cn
Funding information
National Key Basic Research Program of
China, Grant/Award Number:
2014CB238905
Abstract
Two Zhundong coals, Nanlutian coal and Wucaiwan coal, were pretreated by
a sequential extraction; alkali and alkaline earth metals (AAEMs) in different
occurrence modes were separated from the coal samples. The contents and
compositions of AAEMs in coal were investigated, and then a kinetic model
was used to quantify their catalytic behavior. Experimental results show that
the content of water‐soluble AAEMs is high and that these AAEMs are
composed mainly of NaCl and other sodium species. After removing these
AAEMs from the Nanlutian coal and the Wucaiwan coal, the activation
energy required for gasification increases by 7.679 and 4.035 kJ mol
−1
,
respectively. Some of the sodium, potassium, calcium, and magnesium species
exist in ion‐exchangeable form, but the content is low. When the ion‐exchange-
able AAEMs were removed, the activation energy increases by 5.117 and 1.400
kJ mol
−1
, respectively. The content of acid‐soluble AAEMs is high and com-
posed mainly of calcium and magnesium salts. After removing these AAEMs,
the activation energy was increased by 2.002 and 0.537 kJ mol
−1
,respectively.
Finally, the content of insoluble AAEMs is very high, and this fraction is com-
posed mainly of silicates and aluminosilicates. As these AAEMs are stable, their
catalytic effect could be ignored.
KEYWORDS
alkali and alkaline earth metals (AAEMs), catalytic performance, occurrence modes, Zhundong coal
1 | INTRODUCTION
The Zhundong coalfield, located in the Xinjiang Uygur
Autonomous Region, is the largest integrated basin in
China and includes a huge coal reserve of 390 Gt.
1
Zhundong coal is a promising fuel for power plants
because of its high volatility and low ash and sulfur con-
tents. Unfortunately, severe slagging, fouling, and ash
deposition occur inside furnaces and convective passes
when Zhundong coal is burned.
2
The high concentration
of alkali and alkaline earth metals (AAEMs) has been
found to be responsible for these problems. Additionally,
AAEMs show catalytic behavior and can increase the gas-
ification reaction rate. Besides, Zhundong coal, with its
high reactivity, is also a promising feedstock for gasifica-
tion. Therefore, AAEMs in the Zhundong coal have
attracted much attention recently.
Revealing the mode of occurrence and the role of
AAEMs is a prerequisite for clean use of Zhundong
coal. Normally, these properties are determined by the
sequential extraction method, which is four‐step proce-
dure using four types of extraction agent: deionized
Received: 18 January 2018 Revised: 7 March 2018 Accepted: 8 March 2018
DOI: 10.1002/apj.2190
Asia‐Pac J Chem Eng. 2018;13:e2190.
https://doi.org/10.1002/apj.2190
© 2018 Curtin University and John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/apj 1of13
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