What is Coal? A Combustion File downloaded from the IFRF Online Combustion Handbook ISSN 1607-9 116 Combustion File No: 177 Version No: 1 Date: 22-04-02 Author(s): John Smart Source(s): See CF Referee(s): Peter Roberts Status: Published Sponsor: Smart Energy and Combustion Solutions 1. The Origin of Coal Coal is a combustible, dark and compact stratified mass of decayed plant debris interspersed with smaller amounts of inorganic matter and covered with sedimentary rock. As will be seen below, the length of deposition time and the conditions experienced during deposition all affect the quality of the coal. For these reasons coal is included within the group of primary fuels known as fossil sources of energy ( fossil fuel ). 2. The Quality of Coal The chemical and physical properties, which are of significant importance when a particular coal is used in a given combustion environment, depend upon the relative proportions of the different chemical components that were present in the parent plant debris. The nature and extent of the changes that these components have undergone since their deposition, and the nature and quantity of inorganic matter and moisture present also play a significant part in the quality of the final coal. These latter parameters vary widely for the different kinds of coals. Although land plants first developed in the Lower Palaeozoic Era, it was not until the Upper Palaeozoic Era, particularly the Carboniferous period that adequate plant coverage was established and preserved to produce the necessary accumulations of organic matter to produce significant coal reserves. These differences give rise to the concept of coal rank, which is used to indicate the stage of alteration, or degree of coalification, obtained by a particular coal; the greater the alteration, the higher the rank of the coal. The nomenclature describing the coal rank contain primarily, Peat , Lignite or Brown Coal , Sub-bituminous coal , Bituminous coal, Semi-anthra citeand Anthracite.
