The Evaluation of Coal, with Particular Reference to Small Coal for Steam Raising

Abstract

It is generally recognized that the sale and purchase of coal for steam generation on the basis of its calorific value would be more rational than the present methods. In the paper the advantages of the calorific value basis are briefly discussed, and reasons given for its relatively slow development. The non-uniformity of industrial coals makes it difficult to assess their value except in relatively large quantities. This has an important bearing on the selection of coal by the short boiler-trial method. Apart from the technical difficulties of attaining a reasonable degree of accuracy in a short boiler-trial, there must always be a doubt as to whether the sample tested was really representative. An alternative method of evaluation is described which enables larger and more representative quantities of coal to be examined. This method is based on accurate sampling and analysis, and is claimed to be less liable to error. At the same time it permits a greater number of types of coals to be investigated, thus giving the purchaser a wider choice, and increasing his knowledge of coals. In addition, the author provides a basis of control for subsequent deliveries. It is, in any case, strongly recommended as a check on any other method.