METHOD FOR EVALUATING WEATHERING DEGREE OF COAL, METHOD FOR EVALUATING COKING PROPERTIES OF WEATHERED COAL, METHOD FOR CONTROLLING WEATHERING DEGREE OF COAL, AND METHOD FOR PRODUCING COKES

摘要

Provided are: a method for evaluating the weathering degree of a coal and the coking properties of a weathered coal, said weathering degree and coking properties each falling within a range in which conventional methods are not usable in measuring the same, by using an index that enables the evaluation of an effect on coke strength; and a method for controlling the weathering degree of a coal using the above-said index, whereby a weathered coal can be added to a coal blend for producing cokes without lowering the coke strength. The weathering degree of a coal is evaluated by using as an index the surface tension of a semi-coke that is obtained by thermally treating a weathered coal. Further, the surface tensions of semi-cokes of multiple brands, which are obtained by thermally treating coals of the multiple brands contained in a coal stock, are preliminarily determined. Also, the ratios of the coals of the individual brands in the coal stock are assessed. Then, the weathering degrees of the coals of the individual brands are controlled so that the interfacial tension γinter of a semi-coke compound, which is obtained by mixing the semi-cokes of the individual brands in accordance with the ratios thereof, does not exceed 0.03 mN/m.