Coarse defect structure in coke was quantified and its control factor was investigated, which exerts a strong influence on coke strength, as part of the development of high strength cokemaking technology.
First of all, X-ray CT images of several cokes were evaluated by image analysis and it was clarified that coke defect structure around millimeter scale obeyed Weibull distribution. Secondary, viscosity (η) and swelling pressure (ΔP) of coal during plastic phase, those affect bubble growth phenomena, were measured, based on the assumption that there is correlation between bubble growth behavior and coke defect generation. As a result, coarse defect structure in coke was strongly dependent upon the bubble growth factor ΔP/η which can be derivable from a governing equation for single bubble growth. Eventually, it was cleared that the bubble growth factor was one of the important parameter to control coke strength.
