Electric-Field-Enhanced Fabric Filtration of Electrically Charged Flyash

Abstract

This paper summarizes measurements in which both external electric field, applied by electrodes at the fabric surface, and flyash electrical charge, controlled by an upstream corona precharger, are independent variables in a factorial performance experiment carried out in a laboratory pulse-jet baghouse. In agreement with previous publications, increasing either the electric field strength or the magnitude of the flyash charge/mass reduced the rate at which the pressure drop across the bags built up. And although increasing both field and dust charge together produced still further reduction in the pressure drop buildup rate, bag weighings showed that adding charge to the flyash reduced the quantity of flyash deposited on the bag during one filtration cycle, whereas increasing the electric field had no detectable effect on this quantity. These observations suggest that the mechanism by which the external field enhances the performance of the fabric filter is increasing the permeability of the collected flyash layer, while the precharger enhancement mechanism is primarily that of a prefilter. Since the magnitude of the electrical charge/mass of the test flyash does not affect the magnitude of the enhancement induced by the external electric field, the enhancement mechanism by which the external field increases the dust cake permeability is concluded not to be a coulomb capture force.