Changes in organic structure and mineral phases transformation of coal during heat treatment on laboratory scale

Vivek Mishra,Sanchita Chakravarty,Mamta Sharma,Amit Banerjee

doi:10.1007/s40789-016-0153-y

Vivek Mishra, Sanchita Chakravarty + Show 2 more

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https://doi.org/10.1007/s40789-016-0153-y

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Abstract

Structural changes due to coalification and oxidation influence the coal quality, geochemically and petrologically. Understanding of the coal structures helps to predict the behaviour of coal at various processes. The objective of this paper is to study the changes in organic structure and mineral phase transformation during combustion. Different density fractions were generated and then heated at different temperatures from 200 to 1000 °C. Petrography, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were carried out on all the density fractions aimed to accomplish this objective. Here, through petrography, it was observed that the vitrinite and liptinite macerals disappear at higher temperature while porous inertinite is seen. The inertinite structure is exposed which is assumed by the presence of −OH and C–O–C stretches with the aromatic nucleus (CH) and three to four adjacent H from FTIR spectra. Moreover, it can be concluded that aliphatic groups get collapsed at high temperature. In case of inorganic matter, through XRD and FTIR, it is also revealed that with increasing temperature, clay minerals converted into elemental oxides. Hence, this study is suggesting that the structures of coal are altered by the degree of contact metamorphism.

Highlights

Coal consists of primary macromolecules of polyaromaticpolynuclear structure with some heteroatom groups and their secondary networks, latter of which are derived from aromatic ring stacking, aliphatic side chain entanglement, and hydrogen bonds, cation bridges, charge-transfer interactions through oxygen functional groups (Solum et al 1989; Carlson 1992; Cody et al 1993; Nakamura et al 1995; Larsen et al 1996; Wu et al 2013)
The presence of kaolinite at low temperatures (B400 °C), and illite, andalusite, mullite at high temperatures ([400 °C) whereas quartz was seen as the major mineral phase in all the samples of different density fractions at different temperatures
This study provides a comprehensive view of the changes in organic structure with increasing temperature and helps to predict the structure of inertinite macerals

Summary

Introduction

Coal consists of primary macromolecules of polyaromaticpolynuclear structure with some heteroatom groups and their secondary networks, latter of which are derived from aromatic ring stacking, aliphatic side chain entanglement, and hydrogen bonds, cation bridges, charge-transfer interactions through oxygen functional groups (Solum et al 1989; Carlson 1992; Cody et al 1993; Nakamura et al 1995; Larsen et al 1996; Wu et al 2013). Inertinite is the most aromatic and most thermally stable of all the maceral groups (Pandolfo et al 1988; White et al 1989; Vasallo et al 1991; Xie et al 1991; Sun et al 2003; Wang et al 2010). In this group, the Changes in organic structure and mineral phases transformation of coal during heat treatment

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