Single-particle characterization of municipal solid waste (MSW) ash particles using low-Z particle electron probe X-ray microanalysis

Environmentally benign treatment of municipal solid waste (MSW) ashes has been a worldwide issue since more countries are implementing incineration to reduce waste volume. A single-particle analytical technique, named low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA) was applied to characterize MSW fly- and bottom-ash particle samples collected from two municipal incinerators in Korea. According to their chemical composition, many distinctive particle types were identified. For fly ash sample collected in one incinerator (sample S1), where lime slurry injection is used for acid–gas treatment, CaCO3-containing particles (28.4%) are the most abundantly encountered, followed by carbonaceous (23.6%), SiO2-containing (13.8%), NaCl-containing (13.1%), and iron-containing (10.5%) particles. For fly ash sample collected at the other incinerator (sample S2), NaCl-containing particles (40.4%) are the most abundantly encountered, followed by iron-containing (29.1%), carbonaceous (11.8%), CaCO3-containing (2.2%), and SiO2-containing (7.0%) particles. For bottom ash sample collected at one incinerator (sample S3), iron-containing particles (46.6%) are the most abundantly encountered, followed by CaCO3-containing (17.3%), carbonaceous (16.6%), and Si and/or Al oxide-containing (15.8%) particles. For bottom ash sample collected in the other incinerator (sample S4), iron-containing particles (63.4%) are also the most abundantly encountered, followed by carbonaceous (14.0%), CaCO3-containing (10.0%), and Si and/or Al oxide-containing (6.1%) particles. Chemical compositions of the two bottom ash samples are not much different compared to those of the two fly ash samples. It was demonstrated that the single-particle characterization using this low-Z particle EPMA technique provided detailed information on various types of chemical species in the MSW ash samples. In addition, the technique has advantage over conventional analytical techniques in the point that both crystalline- and glass-like ash particles can be analyzed at the same time.