Abstract
Recent epidemiologic studies have corroborated the relationship between ambient concentration of airborne fine particles and detrimental heath responses. Though dust particles in flue gases can efficiently be removed with bag filters and electrostatic precipitators, the collection efficiency for submicron particles requires improvement. In the present study, a packed bed with applied electric field was connected to the outlet of an electrostatic precipitator of the cylindrical type to collect submicron particles that pass through the precipitator. Since the submicron particles were observed to carry electrostatic charges, the precipitator also functions as an electrostatic charger. Measurement of the collection efficiency of the packed bed for submicron particles revealed that although collection mechanism has puzzling aspects and is more complicated than we expected, the efficacy is clearly enhanced by the electrostatic effects. Owing to the limitation in our high voltage supply, the maximum field strength we applied was only 1 kV/cm, which is much lower than that applicable in practice, namely, 5 kV/cm. Nevertheless, the observed collection efficiency of the packed bed for submicron particles was 98% at a pressure drop of 0.2-0.3 kPa for a superficial velocity of 50 cm/s.
