ABSTRACT
Coal can be regarded as an organic sedimentary rock. It consists of carbon, hydrogen, oxygen, and minor proportions of nitrogen and sulfur. Coal seams occur in main types of deposit: a sequence of coal seams, each of great extent and moderate thickness. The main factor in the formation of coal and of coalfields has been the accumulation and partial decay of vast quantities of woody material to produce peat. The nature of the peatlike product of decay can be estimated from the fact that vegetable matter consists of three main types of material: cellulose, lignins, and plant proteins. The laboratory tests applied to characterize coal and to assess its properties are proximate analysis, ultimate analysis, and various coke swelling index experiments to clarify its properties. Moisture in coal tends to reduce its heat of combustion and hence it is of considerable commercial interest.
