Research on the coke strength has recently been carried out treating the coke as a porous material and a new progress is made in the essential evaluation of coke strength. Previous researches have, however, discussed mainly the effects of porosity and/or distribution of pores on the strength and little has been studied on the inherent strength which affects the coke strength.In this research, a sieve opening for strength index applied to the microstrength which evaluates the inherent strength was investigated. The micro-strength with a smaller sieve opening was found to be a reasonable index for the inherent strength of coke.It was confirmed that the tensile strength is estimated by porosity and micro-strength. The JIS drum strength which is usually used in industrial plant is also estimated from the porosity and the microstrength through the tensile strength. The results show that the coke strength is determined by the strength of porous material which depends on its porosity and inherent strength.

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SynopsisCaking property is one of the most meaningful indices for the evaluation of coking coal, and is a basis for the coking mechanism analysis. The index given by the Audibert-Arnu dilatometer widely employed at present is re-evaluated in this paper.The results suggest that present indices of contraction and dilatation have little physical meaning, and are not suitable for the absolute evaluation of the caking property of coals; An index for a true dilatation is newly proposed. This true dilatation index (DT) is defined as the ratio of the apparent coal volume after dilatation (VD) to that before dilatation (Vs) and expressed as, DT = 100(VD-VG)IVc.It was confirmed that this index was not affected by test conditions, and was suitable for the absolute evaluation of caking coal with less deviation. Furthermore, the effects of coal size and heating rate are quantitatively evaluated by the true dilatation index.