Abstract: Fly ash generated from incineration of municipal solid waste (MSW) when placed in landfills under mild acid conditions can leach lead and cadmium. A process for stabilizing heavy metals in this fly ash is presented which involves calcining in the presence of an oxygen containing gas stream at a temperature greater than about 375.degree. C. and substantially less than about 800.degree. C. for times from about 170 seconds up to about 5 hours fly ash which has been subjected to lime scrubbing for acid gas removal. Such treated MSW fly ash will give leachates containing heavy metal concentrations less than the EPA regulatory limit.

Abstract: Fly ash generated from incineration of municipal solid waste (MSW) when placed in landfills can under mild acid conditions leach lead and cadmium. A process for stabilizing lead in this fly ash is presented which involves calcining a mixture of the fly ash and certain calcium-containing compounds in the presence of an oxygen containing gas stream at a temperature greater than about 475.degree. C. and substantially less than about 800.degree. C. for times from about 30 minutes up to about 5 hours. Such treated MSW fly ash will give leachates containing lead concentrations less than the EPA regulatory limit.