Process for vitrifying incinerator ash

Abstract

The invention relates to a process of eliminating high chloride-containing incinerator ash and incinerator ash-residue mixtures, without generating excessive heavy metal-containing effluents during the actual vitrification of the ash. The process involves first pretreating the incinerator ash or ash-residue mixture, if needed, whereby the resultant ash contains less than about 3% halogen by weight and less than about 3% C.. Following the pretreatment, the ash is dried and then mixed with any additives needed to make up a vitrifiable batch mixture which will, when subsequently vitrified, form a glass possessing an excellent acid durability. A durability whereby such that the weight loss of the glass in 5% HCl solution at 95.degree. C. is 2.0 mg/cm.sup.2 or less in 24 hours. This durability results in minimal or non-detectable leaching of hazardous heavy metal or non-metallic specie and is sufficient enough durability such that the vitrified glass will easily pass the EPA's test for leachability. A suitable glass meeting the requirements is comprised of, expressed in terms of weight percent, about 47-76% SiO.sub.2 ; 8-29% Al.sub.2 O.sub.3, 3.4-33.0% CaO; and optionally 0-25% R.sub.2 O, wherein R.sub.2 O is selected from the group consisting of Na.sub.2, Li.sub.2 O, and K.sub.2 O; 0-5% Fe.sub.2 O.sub.3 ; 0-18% B.sub.2 O.sub.3 ; 0-7% ZrO.sub.2 ; 0-7% TiO.sub.2 ; 0-10% MO, wherein MO is selected from the group consisting of MgO, BaO, ZnO or SrO; 0-8% of at least one member selected from the group consisting of PbO, CdO, Cr.sub.2 O.sub.3, CuO, and NiO; and 0-4% SO.sub.3 with 0-4% Cl+F as batched.