Ash particle sticking and rebound behavior: A mechanistic explanation and modeling approach

In this work, a mechanistic ash particle sticking and rebound criterion is developed and validated against experimental data. The model is able to predict the threshold of particle sticking and rebound as a function of the particle kinetic energy. Furthermore, it explains the selective deposition of large iron-rich and small aluminum silicate particles, which were found in deposits on a cooled probe taken in a pulverized solid fuel fired power plant. Large particles stick to the deposition probe due to their low viscosity caused by the formation of a low melting eutectic. Small aluminum silicate particles completely dissipate their kinetic energy during the impact due to viscous deformation. There is no excess energy left for them to rebound. It is shown, that the particle kinetic energy and viscosity are key parameters for the sticking propensity. The model is extended for deposit properties, enabling the capture of solid or solidified particles on a sticky surface. Since all input parameters can be calculated, it is suitable for the application in CFD codes. The required data are the particle and deposit composition, their temperatures in combination with the particle kinetic energy just before the impact.