Abstract
In recent years, blockage accidents of coal ash in ship transportation occur in unloading by hardened coal ash. Hardening phenomena of coal ash are investigated to prevent from blockage accidents. Because blockage accidents often occur at the season of high temperature and humidity, it is assumed that the cause is moisture absorption of coal ash. Then, the cause of hardening is considered by characteristic investigation of coal ash with different coal mining areas, hardening test in the assumed transportation environment, and chemical analysis on coal ash before and after hardening. As a result, it is confirmed that the main cause of the hardening phenomena is the bridge structure of gypsum between particles. In addition, by analyzing water-soluble composition of coal ash, it is specified that the amount of SO3 influence the degree of hardening. The amount of SO3 in coal ash is greatly influenced by the difference of coal mining area. Moreover, it is assumed that the temperature of EP influences hardening of coal ash because it tends to be the higher amount of SO3 in coal ash at lower temperature.
