Effects of particle size on properties and thermal inertization of bottom ashes (MSW of Turin's incinerator). (1st February 2019)

• Record Type: Journal Article
• Authors: Caviglia, Caterina; Confalonieri, Giorgia; Corazzari, Ingrid; Destefanis, Enrico; Mandrone, Giuseppe; Pastero, Linda; Boero, Renato; Pavese, Alessandro
• Is Part Of: Waste management. Volume 84(2019)
• Page Start: 340
• Page End: 354
• Publication Date: 2019-02-01
• Subjects: Bottom ashes -- Particle size distribution -- Leaching -- Heavy metals -- Inertization -- Thermal treatments; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2018.11.050
• Languages: English
• ISSNs: 0956-053X

Abstract

Highlights: BA show properties dependent on particle size. Heavy metals concentration tends to increase in small size BA. Thermal treatments on BA are only partially effective to inhibit heavy metals mobility. Abstract: The aim of this study is twofold: (i) characterization of the bottom ashes from the Incinerator plant of the city of Turin (northern Italy), in terms of their chemical/phase compositions and capacity to release heavy metals in leachates, as a function of particle size; (ii) investigation of thermal treatments' efficacy to promote inertization of the same bottom ashes, exploring time-temperature ranges with t ≤ 6 h and T ≤ 1000 °C. Special attention is paid to macro-sampling techniques in order to have samples that are representative of the average bottom ashes production. Micro-XRF, ICP-OES, SEM-EDS, Ion Chromatography and X-ray powder diffraction were used to investigate bottom ashes and leachates. Bottom ashes are mainly constituted by an amorphous phase, ∼66–97 wt%, regardless of particle size; the remaining phases are quartz, calcite, Fe-oxides, melilite and other minor crystalline materials. The amorphous phase exhibits a relevant dependence on particle size, and undergoes dissolution in water up to 20 wt%, thus being the most important component in affecting chemical species release. The smaller the bottom ashes' particle size, the more the heavy metals (major species: Zn, Cu, Ti, Pb) and calcium contents increase, whereas silicon's decreases. Electrolytic current observations in combination with phase/chemical composition and metals release as a function of particle size, suggest that bottom ashes partition into two classes, i.e. ≥1 and <1 mm, for inertization purposes. Thermal treatments exhibit partial efficacy to curb heavy metals mobility: whilst they reduce Cu release, they lead to a inverse effect in the case of Cr.