NOx Control Technology Requirements Under the United States' 1990 Clean Air Act Amendments Compared to Those in Selected Pacific Rim Countries

The 1990 Clean Air Act Amendments (CAAAs) require reduction of nitrogen oxide (NOx) emissions under two provisions: Title I requires control of NOx from all source types for the purpose of attaining ambient air quality standards for NOx and ozone; and Title IV requires control of NOx from coal-fired utility boilers for the reduction of acid rain precursors. Title IV is the more straightforward of the two, and sets national emission standards for dry-bottom wall-fired and tangentially fired boilers based on low NOx burner technology (LNBT), defined by EPA to include separated overfire air (OFA). Emission standards for other boiler types are to be promulgated by 1997. NOx controls under Title I are more complex, and are based on reductions necessary to reduce local and regional ambient levels of NOx and ozone. Control technology requirements under Title I are based on Reasonably Available Control Technology (RACT) as defined by EPA's Office of Air Quality Planning and Standards; however, emission levels are set by the states according to local conditions. Technologies defined as RACT include low NOx burner technology, selective noncatalytic reduction (SNCR), and selective catalytic reduction (SCR). These and other combustion modifications and flue gas treatment technologies are described. NOx emission regulations and technology requirements in the U.S. are compared to those in selected Pacific Rim countries.