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 chargelmass 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.
Pollution prevention (P2) options to reduce styrene emissions, such as new materials and application equipment, are commercially available to the operators of open molding processes. However, information is lacking on the emissions reduction that these options can achieve. To meet this need, the U.S. Environmental Protection Agency's (EPA) Air Pollution Prevention and Control Division, working in collaboration with Research Triangle Institute, measured styrene emissions for several of these P2 options. In addition, the emission factors calculated from these test results were compared with the existing EPA emission factors for gel coat sprayup and resin applications. Results show that styrene emissions can be reduced by up to 52% by using controlled spraying (i.e., reducing overspray), low-styrene and styrene-suppressed materials, and nonatomizing application equipment. Also, calculated emission factors were 1.6-2.5 times greater than the mid-range EPA emission factors for the corresponding gel coat and resin application. These results indicate that facilities using existing EPA emission factors to estimate emissions in open molding processes are likely to underestimate actual emissions. Facilities should investigate the applicability and feasibility of these P2 options to reduce their styrene emissions.
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