Heterogeneities of fly ash particles gen

Although municipal solid waste incineration fly ash are fine particles and a priori considered as homogeneous, they have complicated structures inside their bodies. This study quantitatively investigated two categories of heterogeneity of fly ash produced from a fluidized bed combustor: intraparticle heterogeneity and inter-particle heterogeneity. The investigation revealed that in the surface and semi-soluble components, Ca exhibited smaller intraparticle heterogeneity than Al and Si. Ternary diagram analysis suggested that semi-soluble components mainly consist of Ca-based matrices such as CaCO3 and unreacted Ca(OH)2, along with aluminosilicate domains. Notably, all major elements, excluding Fe and Ti, demonstrated 3–66% higher inter-particle heterogeneities on the surface compared to semi-soluble and insoluble core components, indicating that the surface component of the fly ash is considerably more heterogeneous. Moreover, the fly ash produced from the fluidized bed combustor displayed intra- and inter-particle heterogeneities akin to those from a stock combustor, with Si playing a more critical role in the fly ash formation process in fluidized bed combustors. The findings suggest that the heterogeneous bodies of fly ash may significantly impact the leaching behavior of metals contained within the particles.