Chlorinated polymers and their effects on incinerator emissions.

摘要

Many chlorinated organic compounds are emitted from stacks of waste incinerators. Many of these compounds are serious health threats and minimizing their emissions is a priority. Chlorinated plastics are thought to play a major role in formation of the chlorinated compounds, however their exact contribution to the formation of the chlorinated toxins is not known. Two areas of the polymer's expected behavior in an incinerator were investigated using two chlorinated polymers--polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC). The first area studied was the behavior of the PVDC polymer when exposed to heating rates and ambiances expected in an incinerator. By heating the PVDC polymer under different degradation atmospheres and heating rates the effects on the products generated were determined. Kinetic parameters describing the yield of the major degradation products from both polymers were also developed. Major degradation products included benzene and HCl from PVC, and chlorinated benzenes and HCl from PVDC. The products generated were not affected by ambiance or heating rate. The second area studied was the effects of HCl and benzene (or chlorinated benzene depending on the polymer) on flame chemistry. Microprobe sampling of a fuel-rich methane flat flame doped with a chlorine source and benzene or dichlorobenzene was performed. Profiles of the major species were determined at different chlorine and benzene or chlorobenzene loadings. The loadings were chosen to represent incinerator waste bed conditions. Results show that the identity of the aromatic compound is more important in forming higher molecular weight chlorinated species than is the chlorine concentration in the primary reaction zone. The SANDIA premixed flat flame computer code was used to develop a detailed kinetic mechanism for the flames. The mechanism consists of over 500 elementary reaction steps and 97 compounds. The results from the flame code modeling runs reinforce the findings from the flat flame experiments, that chlorinated aromatics degradation products from chlorinated plastics are more important for forming chlorinated toxins of concern than is HCl under fuel-rich conditions in the primary reaction zone.