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Research Papers: Energy Extraction From Natural Resources

Mechanism and Kinetics of Pyrolysis of Coal With High Ash and Low Fixed Carbon Contents

[+] Author and Article Information
Lin Yang

Key Laboratory of Low-grade Energy Utilization Technologies and Systems (Chongqing University), Ministry of Education, Chongqing, 400030, China;  School of Computer Science and Information Engineering, Chongqing Technology and Business University, Chongqing, 400067, Chinactbuyanglin@163.com

Jing-yu Ran

Key Laboratory of Low-grade Energy Utilization Technologies and Systems (Chongqing University), Ministry of Education, Chongqing, 400030, China; School of Power Engineering,  Chongqing University, Chongqing, 400030, Chinaranjy@cqu.edu.cn

Li Zhang

Key Laboratory of Low-grade Energy Utilization Technologies and Systems (Chongqing University), Ministry of Education, Chongqing, 400030, China; School of Power Engineering,  Chongqing University, Chongqing, 400030, Chinalizhang@cqu.edu.cn

J. Energy Resour. Technol 133(3), 031701 (Sep 06, 2011) (7 pages) doi:10.1115/1.4004786 History: Received April 29, 2010; Revised July 26, 2011; Published September 06, 2011; Online September 06, 2011

There are much coal with low content of volatile matter (Vad  < 20%), high content of ash (Aad  > 50%), low heating caloric (∼10,000 kJ/kg) in China. It is very important to study pyrolysis performance of the coal to ensure high efficiency of utilization and low pollution emissions. In this paper, we study the pyrolysis reaction details of different types of this coal from different regions of China under different pyrolysis pressures, temperatures, particle sizes, and heating rates by thermo-gravimetry (TG) method. The pyrolysis characteristic temperatures and the characteristic index of volatilization matter released of coal gangue (CG) are obtained in this work. In addition, the detailed process of mechanism and kinetic parameters of pyrolysis are presented. The results show that many factors have an obvious influence on the pyrolysis reaction of the coal. The pyrolysis process of the coal is comprised of two stages. At the primary stage(t < 560 °C), the pyrolysis reaction is dominated by the diffusion rate of volatile matter because of the high ash content, which is the global symmetry diffusion mechanism, and the volatile matter of this stage is more difficult to come out and a high pyrolysis activation energy is observed. With increasing pyrolysis temperature, the pyrolysis reaction is moving into diffusion limitation, the volatile matter is released plentifully, and the low activation energy is found. At the second stage (t > 560 °C), the pyrolysis reaction is governed by the tar-released reaction and the pyrolysis reaction order is 1.5. The high activation energy is also observed for the second stage pyrolysis process.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 7

Effect of pressure on weight loss of CG

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Figure 6

Character of TG and DTG of CG pyrolysis at three different heating rates ((a) TG) and Character of TG and DTG of CG pyrolysis at three different heating rates ((b) DTG)

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Figure 5

TG and DTG of pyrolysis of CG of different particle sizes ((a) TG) and TG and DTG of pyrolysis of CG of different particle sizes ((b) DTG)

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Figure 4

Pyrolysis characteristic points

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Figure 3

Character of TG and DTG for CG pyrolysis at 20 °C/min heating rate ((a) TG) and Character of TG and DTG for CG pyrolysis at 20 °C/min heating rate ((b) DTG)

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Figure 2

The relationship between the temperature and the quantity of pyrolysis production

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Figure 1

The thermogravimetric analysis system

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