Coal composition and structural variation with rank and its influence on the coal-moisture interactions under coal seam temperature conditions – A review article

https://doi.org/10.1016/j.petrol.2019.06.007Get rights and content

Highlights

  • o Coal is composed of organic compounds and minerals.

  • o With rank the chemical structure tends to become stable.

  • o Impact due to the interaction with moisture depends on the rank and the minerals.

  • o The chemical and mineral phase changes influence the mechanical properties.

Abstract

Although numerous studies were conducted on coal utilisation processes overall, due to the recent expansion of the coal industry, processes which involve within the reservoir bares a significant importance for the effective usage of coal. The key to the effective usage of such processes relies on the understanding of the chemical properties of coal and its changes due to the water interaction as most coal seams are naturally saturated. In this context, this paper provides a fundamental understanding of the coal composition and its structure, water adsorption capacity of coal and the impact on the mechanical characteristics due to the chemical property changes under coal seam temperature conditions. The chemical structure of coal can be separated into three catergories; 1) aromatic structures, 2) aliphatic side chains connecting the aromatic structures, 3) oxygen functional groups. The influence of water on the chemical and physical properties of coal largely depends on the oxygen functional groups, along with expandable minerals and dissolvable minerals. However, the degree of adsorption does not limit only to the concentration of oxygen functional groups, but factors including the amount of exposed hydrophilic material, type of polar functional groups, type of clay minerals and pore fluid conditions also needs to be considered. We also highlight the methods of which the mechanical properties of coal changes due to the coal water interaction.

Keywords

Coal chemical structure
Coal-water interactions
Coal reservoir temperature conditions
Mechanical strength

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