Abstract
In our previous paper, we proposed a new measurement method for coal thermoplasticity called the “permeation distance method,” in which the permeation distance of thermally plastic coal into a glass bead layer adjacently placed on the coal sample is measured as a unique caking property. Although the maximum permeation distance measured by this method is roughly correlated with Gieseler fluidity, large deviation is observed, especially for high fluidity coals. Moreover, that study revealed that high MF coal having a longer maximum permeation distance forms thinner pore-wall structures in coke and that coke strength deteriorates when the coal blend includes longer maximum permeation distance coal. Therefore, a technique for reducing the adverse effects of long permeation distance coal on coke strength is necessary so as to utilize the coal more efficiently.
In this paper, the influence of the grain size of mainly high MF coal on permeation distance and coke strength was investigated to clarify the possibility of controlling the permeation distance. As a result, it was found that the measured maximum permeation distance became shorter with decreasing coal size. Moreover, the coke strength deterioration caused by long permeation distance coal in a coal blend was suppressed as the size of the long permeation distance coal became smaller. Consequently, coal grain size design and control techniques for more effective utilization of long permeation distance coal were proposed.
