Characterization of Municipal Waste Combustion Air Pollution Control Residues as a Function of Particle Size

Air Pollution Control (APC) residues from Municipal Waste Combustion (MWC) typically contain high concentrations of potentially toxic metals. APC residues, consisting of fly ash and lime spray drier scrubber residue, were sieve separated into six size fractions. Residue characterization included physical and morphological classification and chemical speciation. Elemental distributions as a function of particle size indicated parabolic distributions for matrix species and sigmoidal distributions for volatile species. Unreacted lime in the scrubber residue preferentially was present in the smallest fractions which greatly altered the elemental distribution profiles. Mathematical correction for this highly water soluble portion of the residue normalized the data which showed extreme similarity between facilities. Parabolic profiles became nearly linear with negative slopes and sigmoidal trends were transformed into exponential curves. This included adjusted lead concentrations approaching 2 wt% and zinc concentrations up to 8 wt% in the smallest fractions.