Title: Characteristics of graphite-like crystallites in coal with increasing coalification

Authors: Xianbo Su; Qian Wang; Fengde Zhou; Qing Si; Jinxing Song; Haixiao Lin

Addresses: School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan Province, 454000, China; Collaborative Innovation Centre of Coalbed Methane and Shale Gas for Central Plains Economic Region, Jiaozuo, Henan Province, 454000, China ' School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan Province, 454000, China ' Collaborative Innovation Centre of Coalbed Methane and Shale Gas for Central Plains Economic Region, Jiaozuo, Henan Province, 454000, China; School of Earth and Environmental Sciences, University of Queensland, Brisbane, QLD 4072, Australia ' School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan Province, 454000, China ' School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan Province, 454000, China; Collaborative Innovation Centre of Coalbed Methane and Shale Gas for Central Plains Economic Region, Jiaozuo, Henan Province, 454000, China ' School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan Province, 454000, China

Abstract: This paper presents a study on the characteristics of graphite-like crystallites (GCs) in coals with different maximum vitrinite reflectance (R_o,max) which can be used to describe the rank of coal. Laser Raman spectroscopy (LRS), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) were used in testing 17 coal samples with different ranks. Results show that the GCs in coal undertook through three consecutive processes including aromatisation, condensation and polymerisation. Five coalification upgrading yield to six stages that are corresponding to six different ranges of R_o,max. With the increasing coal rank, the GCs grow larger with improving quality and eventually evolve into graphite crystals. HRTEM observation also reveals that GCs in coal have undergone a graphitization process with increases in percentage, size, and order. [Received: April 13, 2017; Accepted: November 28, 2017]

Keywords: graphite-like crystallite; coal rank; coalification upgrading; coal deformation; evolution.

DOI: 10.1504/IJOGCT.2019.103067

International Journal of Oil, Gas and Coal Technology, 2019 Vol.22 No.3, pp.368 - 388

Received: 13 Apr 2017
Accepted: 18 Nov 2017
Published online: 15 Oct 2019 *

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