Impact experiments of char and ash particles relevant to entrained-flow coal gasifiers

- Particle-wall interactions were characterized by impact experiments.
- Coal, char with different carbon conversion and ash particles were used.
- Experimental tests were carried out in cold and hot conditions.
- The target material and surface affect the tangential restitution coefficient.
- The restitution coefficients decrease with carbon conversion.

The present study addresses particle-wall interaction phenomena relevant to entrained-flow coal gasifiers. The dynamics of coal, char and ash particles as they are impacted onto a flat surface in cold and hot conditions and undergo momentum transfer and rebound, has been characterized by means of high speed imaging and tracking. Particle-wall collisions were described in terms of normal, tangential and global restitution coefficients. The influence of carbon conversion, impact velocity and surface properties and structure of the target on the dynamical pattern of rebound has been scrutinized. The results indicate that, even at ambient conditions, some plastic deformation occurs during the impact. The restitution coefficients decreased as temperature and carbon conversion increased. This feature was more pronounced at large carbon conversion, confirming the criticality of the char/slag transition to particle deposition on the wall. The dissipation of momentum associated with particle impact may promote the establishment of a dense-dispersed phase in the near-wall zone of entrained-flow slagging gasifiers.