A model for the air emissions of trace metallic elements from coal combustors equipped with electrostatic precipitators

Trace element air emissions from pulverized coal combustion facilities are strongly element-dependent. Relatively non-volatile elements such as chromi um and manganese are captured with efficiencies comparable to overall parti culate capture, whereas more volatile elements such as selenium and arsenic are captured less efficiently than the ash particulate. Such element-speci fic behavior is a consequence of the partitioning of individual trace eleme nts within the combustion and post-combustion environment, resulting in enr ichment of the more volatile compounds in the smallest ash particles, coupl ed to size-dependent particulate penetration through air pollution control devices. In this paper, a model of trace element emissions that incorporate s fundamental laboratory results on trace element partitioning as well as r ecent field emissions data is developed. Model results and comparison to fi eld data indicate that while the emissions of non-volatile elements such as chromium are currently well predicted by existing database-referenced empi rical models, predictions of the emitted concentrations of volatile compoun ds such as arsenic and selenium can be improved by more than 25% through in corporation of element and size-dependent partitioning and penetration. (C) 2000 Elsevier Science B.V. All rights reserved.