Slag from hazardous waste incineration: Reduction of heavy metal leaching

Hazardous waste incineration (HWI) in rotary kilns and the disposal of the residues on landfills play an important role in German waste treatment. In order to reduce costs by disposal on cheaper landfill sites still applying to landfill regulations the leaching behaviour of HWI-slag should be improved further. In a new process-integrated approach hazardous waste is mixed with limestone, which initiates chemical reactions with heavy metals in the rotary kiln yielding new compounds of different solubility. These reactions were observed after treatment at 1200°C combined with fusion processes, at 930°C they also occurred without fusion to the major part. For that purpose HWI-slag/limestone mixtures are thermally treated and then examined by elution tests. A minimum of overall heavy metal leaching was determined at CaO-contents between 15 and 20% after sintering at the average temperature at HWI.