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Effects of microstructural evolutions of pyrolysis char and pulverized coal on kinetic parameters during combustion

  • Jiang-yong He
  • Chong ZouEmail author
  • Jun-xue Zhao
  • Cheng Ma
  • Xiao-rui Zhang
Original Paper
  • 34 Downloads

Abstract

Pyrolysis chars have potential as fuels for pulverized coal injection (PCI); however, their proper and efficient utilization requires evaluation of char combustion kinetics. The combustion characteristics of two chars (F-char and M-char) and two pulverized coals (H-PCI and P-PCI) were analyzed herein using thermogravimetric analysis–mass spectrometry. The apparent activation energy (Ea) of the sample under non-isothermal combustion conditions was obtained using the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods, and the reaction mechanism for the fuels was established using the Malek method. Additionally, changes in the microscopic pore structure and carbon chemical structure of the fuels at different stages of combustion were characterized using N2 adsorption and X-ray diffraction to analyze the relationship between microstructural evolution and Ea. The results suggested that Ea of the sample first rapidly decreased and then became stabilized during combustion. Compared with pulverized coals, the two chars presented more developed microscopic pore structure, less-ordered carbon chemical structure and lower Ea during reaction. During combustion, the stacking height of the aromatic layer first decreased and then increased, whereas the specific surface area first increased and then decreased. The volatile content significantly influenced Ea only during the initial stage of combustion. During the middle stage, Ea was controlled more by the microscopic pore structure and the carbon chemical structure, and those influences disappeared in the later stage. The transition point of the structures affecting Ea occurred at a combustion rate between 52.9% and 72.0%. In general, the microscopic pore structure and the carbon chemical structure influenced kinetic parameters more than the volatile content.

Keywords

Char Pulverized coal Combustion Chemical structure Kinetics Activation energy Pore structure 

Notes

Acknowledgements

The authors are grateful for the financial support of the National Natural Science Foundation of China (Nos. 51704224 and 51574189), the Natural Science Foundation of Shaanxi, China (No. 2016JQ5041), the Ministry of Education Services Local Scientific Research Program, Shaanxi, China (No. 2017JF012), and Yulin Government of Science and Technology.

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Copyright information

© China Iron and Steel Research Institute Group 2019

Authors and Affiliations

  • Jiang-yong He
    • 1
  • Chong Zou
    • 1
    Email author
  • Jun-xue Zhao
    • 1
  • Cheng Ma
    • 1
  • Xiao-rui Zhang
    • 1
  1. 1.School of Metallurgical EngineeringXi’an University of Architecture and TechnologyXi’anChina

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