Effect of Thermal Treatment Temperature on Characteristics of Hospital Solid Waste Incinerator Fly Ash

The thermal treatment method would be suitable for hospital solid waste incinerator (HSWI) fly ash with high levels of Cl. The goal is to investigate the influence of thermal treatment temperature on the evaporation rate of heavy metals in the fly ash, the phase of the residual ash and the leachability of heavy metals in the residual ash. The results show that Pb and Cd are almost completely evaporated at the temperature above 1000°C, but the evaporation rate of Zn is less than 100% as a result of the existence of two competing reactions at high temperature. With the heat temperature increasing, the content of NaCl in the residual ash decreases while that of silicate increases to a certain extent. As the temperature increases, the leachate concentrations of Cu, Pb, Zn, Cd, Ni etc. show downtrend except Cr in the residual ash. At above 800°C, the leachate concentrations of heavy metals in the residual ash are lower than the threshold values of the hazardous waste provisions. Considering the demand of the effective separation of volatile heavy metals such as Cd, Pb and Zn, the decomposition of dioxin and the safety disposal for the residual ash, the minimum heat treatment temperature should be controlled at about 1000°C.