Effect of Cl/S molar ratio on theoretical partitioning of heavy metals under waste combustion conditions

A simulation calculation was carried out to predict the behavior of heavy metals during waste incineration according to the variation of chlorine content by using a thermodynamic equilibrium model. To predict the behavior of heavy metals in incineration of wastes, chlorine content in wastes was changed up to 3.00 on a Cl/S molar ratio basis. Then the partitioning characteristics of heavy metals with Cl/Metal molar ratio were investigated as solid, liquid, and gas phases of metals. For analysis of emission characteristics, incineration temperature, chlorine content and air-fuel ratio (lambda(T)) were chosen as major operating parameters. It was found that the distribution characteristics of heavy metals were not significantly affected by air-fuel ratio, but evaporation rate of heavy metals increased with operating temperature. Most of the heavy metals remained in solid phase of metal oxides, such as CdO, CrO3, CrO2, CuO and ZnO, except for lead which existed as PbSO4 in the given operating conditions (i.e., T-b=800degreesC, lambda(T)=1.3, and Cl/S=0). It was found that most of the heavy metals in solid phase changed to gaseous Cl compounds, which have a high volatility with regard to increasing the Cl/S molar ratio under the same conditions. However, Cr compounds were almost not affected as chlorine level increased.