Experimental and theoretical analyses on the effect of physical properties and humidity of fly ash impacting on a flat surface

This study investigated the particle-wall collision characteristics of different fly ash particles against a flat surface under dry and humid conditions by experimental and theoretical analyses. The experiment could be applied to simulate the particle deposition in many engineering fields, such as electrostatic precipitators (ESPs), filtration, and agglomerates. The coal used are bituminous coal from Fushun, Liaoning Province (LN) and meager coal from Zhundong, Xinjiang Province (XJ), which are turned into fly ash particles with a diameter of approximately 7 µm using a muffle furnace. The experimental system is designed for an aerosol inlet particle velocity range of 1-7 m/s. A dynamic model is developed to calculate the damping coefficient, contact time, critical impact velocity, and contact displacement under both dry and humid conditions during impact. The results show that the normal restitution coeffcients decrease with increasing density, Young's modulus, and humid condition. Second, based on the dynamic model calculation, the damping coefficient and contact time are obtained with different impact velocities in a collision. The values of the damping coefficient and contact time are larger under humid conditions due to the effect of capillary force. Third, the critical impact velocity increases under humid condition. Finally, the maximum contact displacement versus the impact velocity and the change of total force and velocity versus the contact displacement during a collision are examined.