Numerical Analysis of Coal Ash Bed Hardening by Water Condensation

In this study, hardening phenomena of coal ash beds in high-humidity condition are examined. We employ a diffusion simulation in clarifying the distribution of condensed water in coal ash beds, in which water vapor is absorbed into sulfur trioxide adhered on the surface of coal ash particles. Aqueous sulfuric acids solution formed by the absorption is in equilibrium with the ambient water vapor. The diffusion rate of water vapor is proportional to the difference between the pressure and ambient water vapor pressure. The simulation successfully describes the results of previous experiment, at a constant temperature, with the variations in the equilibrium moisture and particle diameter of coal ash. Moreover, it is clarified that the relationship between water content and hardening phenomena is very similar for various coal ashes, with a correction of particle diameter of coal ash and the volume of condensate bridging between particles.