THE INFLUENCE OF ASH COMPOSITIONS ON THE BEHAVIOR OF HEAVY METAL IN MELTING PROCESS

The bottom ash of sewage sludge was examined to investigate the influence of ash compositions on the behavior of heavy metal in the melting process by a lab-scale test. Calcium oxide, diphosphorus pentaoxide, aluminium oxide and iron oxide were enriched to the tested ash, which in crucibles were melted in the electric furnace. The proportions of heavy metals remaining in residue after the melting were affected by the compositions of ash, especially basicity (CaO/SiO2) and the amount of P2O5. The proportion of heavy metal in residue increased with the elevated basicity and the amount of P2O5, whereas it decreased with the increase of the amount of Al2O3. According to multiple regression analysis, contribution of each composition to the proportion of heavy metal in residue was calculated.