THE MAJOR SPECIES OF HEAVY-METAL AEROSOL RESULTING FROM WATER COOLINGSYSTEMS AND SPRAY DRYER SYSTEMS DURING INCINERATION PROCESSES

Trace toxic metals in municipal solid waste may escape from the incine ration process in flue gas, in dry collected ash, in wet scrubbed ash, or as a suspended aerosol. Therefore, understanding the behavior of h eavy metals in the flue gas and the best controls in the air pollution control equipment are important and necessary. The control conditions of water cooling and spray dryer systems during incineration processe s significantly influence the formation of heavy metal compounds. The formation of chromium (Cr), lead (Pb), and cadmium (Cd) species under various control conditions (water cooling tower and spray dryer reacto r) was investigated in this study. The object of the experiment is to understand the effects of water cooling and spray dryer systems indivi dually on the formation of heavy metal species. The operating paramete rs that are evaluated include different control systems, control tempe ratures, and chlorine content. A thermodynamic equilibrium model was a lso used to evaluate experimental data. In order to match real inciner ation conditions, a two-stage simulation was performed in this experim ent. The results showed that the relationship of speciation between th e simulation prediction and X-ray diffraction (XRD) analysis is consis tent for Cr compounds; both indicated that Cr2O3 is the major species. The relationship is almost the same for Cd compounds, but not for Pb compounds.