Interphase thermal transport phenomena and slagging-wear mitigation mechanisms in industrial-scale waste heat boilers

Waste heat boilers (WHBs) represent vital heat and mass transfer systems for energy recovery and process intensification, yet their thermal efficiency and operational longevity are severely hindered by complex particulate slagging and surface erosion. In this study, the Multiphase Particle-in-Cell method is employed to uncover the coupled mechanisms of interphase thermal transport, size-dependent particle trajectories, and localized wall degradation within an industrial-scale waste heat boiler. Numerical findings demonstrate that accelerating the inlet gas velocity to 6 m/s suppresses gas recirculation zones but impairs interphase thermal transport efficiency. Particle scale plays a decisive role in heat transfer behavior, with 1 μm particles reaching instantaneous thermal equilibrium alongside convective heat transfer coefficients exceeding 4000 W/(m 2 ·K), whereas coarse particles exhibit values between 100 and 300 W/(m 2 ·K). Trajectory analysis reveals that fine particles seamlessly navigate internal obstacles, while 40 μm particles violently impinge on the baffle plate to produce a peak erosion rate of 72 mm/y. Elevating the flow velocity mitigates the 10 mm/y wear in the rising flue but shifts erosion hotspots to the baffle, driving peak wear to 125 mm/y. Crucially, elevating the wall temperature to 673 K prolongs the particulate molten state and triggers near-wall adhesion, causing the local particle volume fraction on the baffle to surge to 9.1 × 10 −6 and downstream tube concentration to peak at 5.4 × 10 -6 . These quantitative insights elucidate the governing mechanisms of interphase thermal-particulate interactions and offer crucial physics-based guidelines for optimizing industrial multiphase heat exchangers.