Abstract
Emission of particulate matters having diameter of 10.0µm and less, PM10, was investigated in a laboratory-scaled combustion of dried sewage sludge. Influences of the combustion parameters were identified including both temperature and oxygen content in the gas atmosphere. The reaction temperature was fixed at 1200°C, whereas the oxygen content was from 10, 30 to 50% in the gas atmosphere. PM10 was collected by low-pressure-impactor. Each size of it was subjected to characterization by several techniques including XRF, SEM-EDX and CCSEM for the chemical speciation. The results show that, the content of ash in the raw sludge affected its PM10 concentration positively. About 0.1wt% of the inherent inorganic metals directly transferred into PM having size larger than 2.5µm, they mainly are of the refractory metals. On the other hand, about 0.4 4.0wt% of the inherent inorganic metals vaporized and condensed into the ultrafine particulates having size less than 0.5µm, they mainly are of the heavy metals including Zn, Mn, Pb, Cu, etc. A portion of the vaporized metals agglomerated with the refractory elements to form particulates having size ranging from 0.5 to 2.5µm. In addition, PM emission was improved exponentially with the increasing of the oxygen content in the gas atmosphere. Finally, the thermodynamic equilibrium calculation proved the vaporization of heavy metals within sludge and their re-condensation and chemical reaction with the other species in the gas atmosphere. The results were consistent with CCSEM characterization on PM.
