Numerical simulation of MSWI fly ash particle deposition and slag flow behavior in the cyclone melting furnace

In the melting treatment of MSWI fly ash using a cyclone furnace, particle deposition and slag flow behaviors on the furnace wall are critical factors that not only determine the generation of secondary fly ash but also influence the continuity of liquid slag discharge. In this study, the comprehensive model is constructed to encompass deposition criteria, flow characterization, and thermal resistance feedback. Then, this research systematically investigates the particle deposition and slag flow behaviors of MSWI fly ash within the cyclone melting furnace by implementing a bidirectional coupling with CFD simulation software and utilizing a structured mesh. Results demonstrate that particle deposition is effectively decoupled from the combustion process. Larger particles tend to deposit further downstream axially but exhibit better circumferential uniformity. Slag coverage on the refractory wall enhances the capture of large particles. In a vertical furnace, due to liquid slag flows strictly axially, the concentrated deposition of 30 μm particles promotes the circumferentially periodicity and axially strip-like distribution of both liquid and solid slag. The conical contraction structure exerts opposite effects on slag flow in the upper and lower circumferential regions of the furnace wall. When liquid slag at the circumferential bottom of the furnace flows from the cyclone barrel toward the conical contraction section, a sharp increase in liquid slag thickness occurs due to the abrupt reduction of the axial component of gravity.