Characterization of char from high temperature fluidized bed coal pyrolysis in complex atmospheres--颗粒学报PARTICUOLOGY

Zhong, M., Gao, S., Zhou, Q., Yue, J., Ma, F., & Xu, G. (2016). Characterization of char from high temperature fluidized bed coal pyrolysis in complex atmospheres. Particuology, 25, 59-67. https://doi.org/10.1016/j.partic.2014.12.018

Characterization of char from high temperature fluidized bed coal pyrolysis in complex atmospheres

Mei Zhong ^{a b}, Shiqiu Gao ^c, Qi Zhou ^c, Junrong Yue ^c, Fengyun Ma ^{a b *}, Guangwen Xu ^c *

a Ministry Key Laboratory of Oil and Gas Fine Chemicals, College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046, China
b Key Laboratory of Coal Clean Conversion & Chemical Engineering Process, College of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046, China
c State Key Laboratory of Multi-Phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China

10.1016/j.partic.2014.12.018

Volume 25, April 2016, Pages 59-67

Received 30 October 2014, Revised 20 December 2014, Accepted 27 December 2014, Available online 20 July 2015, Version of Record 18 February 2016.

E-mail: ma_fy@126.com; gwxu@home.ipe.ac.cn

Highlights

• Continuous coal pyrolysis was studied in complex atmospheres at high temperatures.

• At ER of 0.064 char had the highest specific surface area and oxidation reactivity.

• In O₂-free atmosphere the presence of CH₄ and CO decreased char specific surface area.

• Presence of H₂ and CH₄ condensed char crystallite structure to lower oxidation activity.

Abstract

The physiochemical properties of chars produced by coal pyrolysis in a laboratory-scale fluidized bed reactor with a continuous coal feed and char discharge at temperatures of 750 to 980 °C under N₂-based atmospheres containing O₂, H₂, CO, CH₄, and CO₂ were studied. The specific surface area of the char was found to decrease with increasing pyrolysis temperature. The interlayer spacing of the char also decreased, while the average stacking height and carbon crystal size increased at higher temperatures, suggesting that the char generated at high temperatures had a highly ordered structure. The char obtained using an ER value of 0.064 exhibited the highest specific surface area and oxidation reactivity. Relatively high O₂ concentrations degraded the pore structure of the char, decreasing the surface area. The char produced in an atmosphere incorporating H₂ showed a more condensed crystalline structure and consequently had lower oxidation reactivity.

Graphical abstract

Keywords

Pyrolysis; Coal char; Oxidation reactivity; Active sites; Crystal structure

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