Stability of heavy metals in bottom ash and fly ash under various incinerating conditions

Abstract High chloride concentrations are normally found in municipal waste. Most chloride resources are originally derived from organic chlorides, e.g., PVC and inorganic chlorides, or chloride salt from kitchen waste. Heavy metals can easily react with chlorides during incineration, thus, producing related metallic chlorides. These factors make the combustion products more complicated (such as metallic chloride, metallic oxide, or heavy metal). This study evaluates the effects of operating conditions on the stability of heavy metals (Pb, Cd and Cr) in bottom ash and fly ash. The parameters evaluated include (1) the additives of inorganic chloride (CaCl 2 and NaCI) and organic chloride (PVC), and (2) various operating temperatures. The experimental results indicate that adding organic chloride (PVC) increased the leaching rates of Cr, Pb and Cd in bottom ash, but decreased this rate in fly ash. The addition of sodium chloride (NaCl) increased the leaching rates of the three metals in fly ash, but only Cr and Cd increased in bottom ash. The other inorganic chloride (CaCl 2 ) increased the leaching rate of Cr in bottom ash and fly ash, but for Pb and Cd decrease. In addition, the TCLP leaching rates of these three metals did not have an obvious relation between the total amount of original metals existed in bottom ash and fly ash and operating temperatures of incinerator, but did relate to the chemical species of the formed products.