Chemische und mineralogische Charakterisierung einer thermisch behandelten Elektrofilterasche

Abstract

The incineration of municipal solid waste creates a highly toxic fly ash, collected by the electrostatic precipitator. This residue requires a treatment before being disposed or partially recycled. One way for the detoxification is a thermal processing between 1300 and 1400°. At this temperature range all organic pollutants will be destroyed and the inorganic compounds separated into a heavy metal containing condensate, an inert, vitreous silicate-phase and a sulfurdioxid enriched waste gas. For the study of this process different samples of the glass phase (both from the melt vessel and after the outlet) were investigated by X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), and optical microscopy (OM). The samples from the melt vessel showed an increase of lead, zinc, manganese, copper, and iron from the top to the bottom of the crucible by a factor of 5. Sulfur displayed an even larger increase from 0.005 g/100 g (%) in the top part to 12 g/100 g (%) near the bottom. In the lower part of the melting tub sulfides like FeS, ZnS, Cu₂S, and MoS₂ dominate. Oxides like melilites and spinels are enriched in the top part and show decreasing concentrations with increasing depth.