PM10 formation behaviors from staged volatile and char combustion of municipal solid waste and refuse-derived fuel

The formation behaviors of PM10 (particulate matter with an aerodynamic diameter ≤10 μm) during staged volatile and char combustion in municipal solid waste (MSW) and refuse-derived fuel (RDF) were investigated. The samples were pyrolyzed in a two-stage reaction tube coupled with a drop-tube furnace (DTF) combustion system for in-situ formation of volatile matter and its immediate combustion, followed by the collection of devolatilized char for subsequent char combustion at 700–1000 °C. The results indicated that the separation of combustion stages roughly aligns with actual combustion regarding formation modes and particle size distribution of PM10. Specifically, the volatilization and subsequent combustion of Na and K, produced in situ during pyrolysis, are key mechanisms for PM0.2 formation. Meanwhile, refractory minerals retained in the char post-pyrolysis still contribute to the formation of both PM0.2 and PM0.2-2. Compared to direct combustion, two mechanisms were found to be weakened during volatile combustion: the heterogeneous condensation on fine particles and the mineral-induced adsorption on volatile. Consequently, PM0.2 yields calculated through linear superposition of volatile and char combustion were overestimated. In contrast, the weaker interactions in staged combustion resulted in lower char combustion temperatures and less fragmentation, leading to lower PM2-10 yields than in actual combustion.