Petrogenetic characteristics of molten slag from the pyrolysis/melting treatment of MSW

Amirhomayoun Saffarzadeh, Takayuki Shimaoka, Yoshinobu Motomura, Koichiro Watanabe

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Abstract

MSW slag materials derived from four pyrolysis melting plants in Japan were studied from the viewpoint of petrology in order to discriminate the glass and mineral phases and to propose a petrogenetic model for the formation process of molten slag. Slag material is composed of two major components: melt and refractory products. The melt products that formed during the melting process comprise silicate glass, and a suite of minerals as major constituents. The silicate glass is essentially composed of low and high silica glass members (typically 30% and 50% of SiO2, respectively), from which minerals such as spinels, melilite, pseudowollastonite, and metallic inclusions have been precipitated. The refractory products consist mainly of pieces of metals, minerals and lithic fragments that survived through the melting process. Investigations demonstrated that the low silica melts (higher Ca and Al contents) were produced at upper levels of high temperature combustion chamber HTCC, at narrower temperature ranges (1250-1350 °C), while the high silica melts formed at broader temperature ranges (1250-1450 °C), at the lower levels of HTCC. The recent temperature ranges were estimated by using CaO{single bond}Al2O3{single bond}SiO2 (CAS) ternary liquidus diagram that are reasonably consistent with those reported for a typical combustor. It was also understood that the samples with a higher CaO/SiO2 ratio (>0.74-0.75) have undergone improved melting, incipient crystallization of minerals, and extensive homogenization. The combined mineralogical and geochemical examinations provided evidence to accept the concept of stepwise generation of different melt phases within the HTCC. The petrogenesis of the melt products may therefore be described as a two-phase melt system with immiscible characteristics that have been successively generated during the melting process of MSW.

Original languageEnglish
Pages (from-to)1103-1113
Number of pages11
JournalWaste Management
Volume29
Issue number3
DOIs
Publication statusPublished - Mar 1 2009

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All Science Journal Classification (ASJC) codes

  • Waste Management and Disposal

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