Vitrification MSWI fly ash using Brown's gas and fate of heavy metals

Municipal solid waste incinerator (MSWI) fly and bottom ash were vitrified at about 1450 °C, for the first time, using Brown's Gas. Vitrification of pelletized fly ash (fly ash + water glass) results in decrease in leaching of toxic heavy metals (except Pb) to much below the Korean regulatory limit value, though melted fly ash was a poor vitrified product having dark grey appearance. Addition of glass cutlet or bottom ash to fly ash increased silica content and decreased the basicity, which lead to good vitrified product having amorphous dark brown glassy structure. Leaching of all potentially hazardous heavy metals present in fly ash also decreased with decrease of basicity. Heavy metals (Zn, Pb, Cr, As, Cu, Mn, Cd) were efficient to substitute parent Al and Ca ions in the silicate matrix. SEM and XRD studies confirmed that fly and bottom ash contained some crystalline structure which transformed in to amorphous glassy structure on vitrification. As the vitrified ash products of fly ash and its mixtures with glass cutlet or bottom ash were found to be non-hazardous in nature and glassy in appearance, they could be considered as construction and road building material in future.