Vitrification of fly and bottom ashes from municipal solid waste incinerator using Brown's Gas

Municipal solid waste incinerator (MSWI) fly and bottom ashes 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 to much below the Korean regulatory limit value, though melted fly ash was a poor vitrified product having dark grey appearance. Addition of bottom ash to fly ash increased silica content and decreased the basicity. It was found that decrease in basicity (from 2.948 to 0.55) lead to good vitrified product having amorphous glassy structure of dark brown color. Leaching of all potentially hazardous heavy metals (except Cu and Mn) present in fly ash also decreased with decrease of basicity. It was found that Cu and Mn were not as efficient as Zn, Pb, Cr, As and Cd to substitute parent Al and Ca ions in the silicate structure. It was further confirmed by SEM and XRD studies that fly and bottom ashes contained some crystalline structure which transformed in to amorphous glassy structure on vitrification. As the vitrified ash product of bottom ash and its mixture with fly ashes were found to be non-hazardous in nature and glassy in appearance, they could be considered as construction and road building material in future.