Air & waste : journal of the Air & Waste Management Association最新文献

This paper discusses the work and results to date leading to the demonstration of the corona destruction process at pilot scale. The research effort in corona destruction of volatile organic compounds (VOCs) and air toxics has shown significant promise for providing a valuable contribution to critical U.S. Environmental Protection Agency and national goals of reducing the health effects associated with exposures to hazardous air pollutants. The corona destruction technology could be especially useful in future years in helping industry meet the residual risk requirements of the Clean Air Act Amendments of 1990. Since 1988, EPA has conducted research in the area of corona destruction of VOCs and air toxics. EPA's interest in corona destruction of molecular species started with modeling of a point-plane reactor for destroying toxic organic compounds. EPA's goal is to develop a technology capable of controlling low concentration streams at low capital and operating costs. The purpose of this work is to develop an industrial scale corona reactor capable of efficiently and cost-effectively destroying VOCs and air toxics at ambient temperature and pressure. Results show that corona destruction is a promising control technology for many VOC-contaminated air streams, especially at low concentrations. Cost comparisons are presented for corona destruction and conventional control devices, carbon adsorption, catalytic incineration and thermal incineration.

The results of a full-scale evaluation of the thermal stability-based hazardous organic waste incinerability ranking are presented. Tests were conducted for a surrogate mixture consisting of sulfur hexafluoride, chlorobenzene, toluene, tetrachloroethene, methylene chloride, 2-chloropropene and 1,1,1-trichloroethane under nominal incinerator operating conditions. Based on median surrogate DREs, the results indicated that the pyrolytic ranking was statistically significant at the 90 percent confidence level while the oxidative ranking was statistically significant at the 97.5 percent confidence level. The heat of combustion ranking failed to give a statistically significant correlation at the 90 percent confidence level. The statistical success of the thermal stability rankings and statistical failure of the heat of combustion ranking suggest that chemical reaction kinetics controlled the relative emission rates of the surrogate compounds during these tests.

The Clean Air Act Amendments of 1990 incorporate, for the first time, provisions aimed specifically at the control of acid rain. These provisions restrict emissions of sulfur dioxide and oxides of nitrogen from electric power generating stations. The restrictions on sulfur dioxide take the form of an overall cap on the aggregate emissions from major generating plants, allowing substantial flexibility in the industry's response to those restrictions. This report describes one response scenario through the year 2030, which was examined by simulation of the utility industry under assumptions consistent with a reference case that was used for analysis of the National Energy Strategy. Emissions that would result from the use of existing and new capacity and the associated additional costs of meeting demand subject to the emission limitations imposed by the Clean Air Act are projected. Fuel use effects, including coal market shifts, consistent with the response scenario are also described. These results, while dependent on specific assumptions for this scenario, provide insight into the general character of the likely utility industry response to Title IV.

For assessing the efficacy of a specific form of the National Ambient Air Quality Standard for O3, those exposure patterns that result in vegetation and human health effects must be identified. For vegetation, it has been found that the higher hourly average concentrations should be weighted more than the lower concentrations. Controlled human exposure work supports the suggestion that concentration may be more important than exposure duration and ventilation rates. It has been indicated in the literature that the current form of the federal O3 standard may not be appropriate for protecting vegetation and human health from O3 exposures. The proposed use of the cumulative index alone as a form of the standard may not provide sufficient protection to vegetation. An extended-period average index, such as a daily maximum 8-hour average concentration, may not be appropriate to protect human health because of the reduced ability to observe differences among hourly O3 concentrations exhibited within exposure regimes. For both vegetation and human health effects research, additional experimentation is required to identify differences in responses that occur when ambient-type exposure regimes are applied. Any standard promulgated to protect vegetation and human health from O3 exposures should consider combining cumulative exposure indices with other parameters so that those unique exposures that have the potential for eliciting an adverse effect can be adequately described.