Optimized Design and Operating m 9 1 1 Parameters for Minimizing Emissions 24 & 7 During VOC Thermal Oxidation

he Clean Air Act (CAA) Amendments of 1990 are inT tended to reduce emissions of volatile organic compounds (VOCs) by 70 to 90%. They specifically designate 189 compounds as hazardous air pollutants (HAPs). The EPA estimates that the aerospace industry generates 208,000 tons per year of HAPs plus an additional 145,000 tons per year of VOCs. Maximum Achievable Control Technology (MACT) standards for regulating HAP emissions from the aerospace industry were proposed by the EPA. The most common HAPs found in the aerospace industry are glycol ethers, xylene, toluene, methyl ethyl ketone, trichloroethane, and methyl isobutyl ketone. Most HAP emissions come from clean-up solvents. Thermal oxidation systems play, and will continue to play, a prominent role in meeting CAA-mandated VOC and HAP emission-reduction targets. According to a study conducted for the American Institute of Chemical Engineers in 1993, oxidation systems are projected to be the technology of choice in 43% of the applications requiring VOC reduction.' Thermal oxidation systems can he applied to 80% of the compounds classitied as HAPS under the CAA. On the one hand, thermal oxidation of VOCs is a very simple process. Organic compounds are bumed to innocuous byproducts. But on the other hand, proper design principles must be applied to ensure complete destruction of the organics while minimizing formation of undesirable by-products. Both design and operating parameters affect performance. This article discusses those principles used to maximize VOC destruction while minimizing the emissions of other pollutant species.