Source Activity Modeling of Freon® Emissions from Open-Top Vapor Degreasers

Publisher Website
Google Scholar
Abstract
Freon® emissions from vapor degreasing operations at an electronics manufacturing firm were studied. Freon concentrations were measured at nine locations around two open-top vapor degreasers (OTVDs) while simultaneous activity observations were made. Concentration measurements were obtained using both charcoal tube/gas chromatographic and Tedlar bag/infrared absorption methods. Advective air flow was found to influence the concentration pattern in the sampling area surrounding the degreasers. Because of this, the box model and an advective-diffusion model were used to translate area concentration measurements into emission rates. Regression analysis between emission rates and activity factors was used to develop emission factors for the degreasing operation. The two models gave very similar estimates of the total emissions from the two degreasers. The average emission predicted by the box model for the 6 hours with bag and charcoal-tube data was 74 g/hour, very close to the 95 g/hour predicted by the advection—diffusion model for the same hours. The correlation coefficient between the two models for these 6 hours was 0.91. Emissions were found to be a function of solvent dragout. Dragout is best represented as total surface area of parts cleaned, surface area of cupped parts, and the observation of Freon dripping from loaded baskets. Randomly loaded cupped parts were found to carry over three times more dragout than uncupped parts on a per surface area basis. The emission factor based on total surface area cleaned is 37 g/m2. When the model is adjusted for type of parts cleaned, emission factors are 21 g/m2 for uncupped parts, 75 g/m2 for cupped parts, and 7 g/load with visible solvent dripping. An addition 20 g/hour not associated with solvent dragout was identified.