Experimental study on particle characteristics in an opposed multi-burner gasifier

•Particle behaviors in gasifier under hot condition are observed for the first time.•Particle characteristics are studied by multiplicate visualization techniques.•The particles in gasifier are mainly classified to five different types.•Larger size particles exist as particle groups with three different types.

Based on the bench-scale opposed multi-burner (OMB) coal-water slurry (CWS) gasifier, temperature distributions of particles at different spatial regions, reactivity characteristics of particles and their interactions were studied with a variety of visualization techniques. The particles in gasifier are mainly classified to five types, and the principles of transformation between them are concluded as: low temperature particle without wake (LTP) could transform to low temperature particle with high temperature wake (LTP-HTW) when contacted with high temperature flame, then transform to LTP as reactions terminate and the particles become non-reactive; low temperature particle with low temperature wake (LTP-LTW) would transform to LTP-HTW when transfer to high temperature regions; as LTP-HTW adhere to the refractory wall, their wakes vanish and particles transform to high temperature particle without wake (HTP); high temperature particle with high temperature wake (HTP-HTW) could finally transform to HTP after the end of reactions. Particle groups with irregular shapes, flake-shaped and hollowed spherical structure are the forms of existence for larger size particles in gasifier.