ABSTRACT
Abstract: Coal, a non-renewable resource, is far more plentiful than oil or gas with considerable amount of coal reserves worldwide. Coal and coal products play an important role in fulfilling the energy needs of the society. Basic knowledge about coal, its origin, and its formation will help in its future applications in power generation, metal processing, and chemical production. The greatest coal-forming period in geological history is during the Carboniferous era, while large deposits during the Permian,
with lesser but still significant in the Triassic and Jurassic periods, and minor in Cretaceous. The formation of coal has been explained either by in situ or by drift origin of vegetable matter under different conditions. The continuing effects of temperature and pressure over millions of years progressively increased the maturity of coal formation, that is, from peat to anthracite. The process of coalification starts with the biochemical process of peatification/ humification followed by geochemical process. The types
1.1 Introduction ....................................................................................................................................................................... 4 1.2 Origin and Formation of Coal ........................................................................................................................................... 4 1.3 Types of Coals ................................................................................................................................................................... 5 1.4 Coal Ranks and Classification ........................................................................................................................................... 6
1.4.1 Coal Ranks .......................................................................................................................................................... 6 1.4.2 Classification of Coal ........................................................................................................................................... 7
1.4.2.1 Scientific Classifications ........................................................................................................................ 7 1.4.2.2 Commercial Classification .................................................................................................................... 8
1.5 Micro-Constituents of Coal ............................................................................................................................................... 8 1.5.1 Microlithotypes .................................................................................................................................................... 11
1.6 Chemical Composition and Heteroatoms in Coal ........................................................................................................... 11 1.6.1 Chemical Composition ...................................................................................................................................... 11 1.6.2 Heteroatoms ....................................................................................................................................................... 12
1.6.2.1 Oxygen ................................................................................................................................................ 12 1.6.2.2 Nitrogen ............................................................................................................................................... 12 1.6.2.3 Sulfur ................................................................................................................................................... 13
1.7 Chemical Structure of Coal ............................................................................................................................................. 14 1.7.1 Random Layers (Turbostratic Structure) in Chemical Structure of Coal .......................................................... 15
1.8 Rock Types and Mineral Matters in Coal ....................................................................................................................... 16 1.8.1 Rock Types ........................................................................................................................................................ 16 1.8.2 Mineral Matters in Coal .................................................................................................................................... 17
1.9 Coal Sampling (In Situ and Ex Situ) and Coal Analysis ................................................................................................. 19 1.9.1 Coal Sampling ................................................................................................................................................... 19
1.9.1.1 In Situ Sampling .................................................................................................................................. 19 1.9.1.2 Ex Situ Sampling ................................................................................................................................. 19
1.9.2 Coal Analysis ..................................................................................................................................................... 19 1.9.2.1 Proximate Analysis ............................................................................................................................. 20 1.9.2.2 Ultimate Analysis ................................................................................................................................ 20 1.9.2.3 Thermochemistry of Coal ................................................................................................................... 21
1.10 Analytical Methods for Coal Analysis ............................................................................................................................ 22 1.11 Coal Products .................................................................................................................................................................. 23
1.11.1 Coal Combustion Products ................................................................................................................................ 23 1.11.2 Coal-Derived Products ...................................................................................................................................... 23 1.11.3 Other Products ................................................................................................................................................... 23
References ................................................................................................................................................................................... 25
of coal have been defined based on lithotypes, coal ranks, microlithotypes, and maceral contents. In this chapter, the chemical nature of coal and its products are summarized. It includes discussion on coal formation, types and nature of coals, coal ranks and classification, micro-constituents of coal, chemical composition of coal, heteroatoms in coal, coal chemical structure including molecular structure, analytical methods for coal characterization, rock types and mineral matters in coal, coal sampling (in situ and ex situ), coal analysis, elemental analysis of coal (C, H, N, O, Cl, Hg, etc.), analytical methods for coal analysis, coal products, chemical compositions of coal liquids, and other coalderived products. The maceral composition, heteroatoms, mineralogy, and the presence of trace elements and rare earth elements in coals found in the different parts of the world are also reported. Emphasis is also given on X-ray diffraction technique for the structural characterization on coals, evaluation of the carbon stacking structure, estimating the size of the aromatic lamellae and the average distance between lamellae, and the mean bond distance. The contents of this chapter will be basically of help to the beginners and the coal fraternity in developing and designing advanced coal conversion technologies. Moreover, this chapter will serve as a basis for going through the subsequent chapters in the book.
