Nitrogen oxides are a class of compounds made of nitrogen and oxygen in varying percentages. Nitrogen dioxide (NO) is the most common and prevalent component of nitrogen oxide emissions. NOx is emitted from high temperature combustion processes. Sources include motor vehicles, fossil fuel electric generators, and other industrial, commercial and residential sources that burn fuels. In 1997, over 23 million tons of nitrogen oxides were emitted into the air in the United States. An important characteristic of NOx emissions is that they can be transported long distances and causes problems far from the original emissions sources. Some of the possible problems of NOx transport include acid rain, greenhouse effect, regional haze, formation of toxic chemicals, and eutrophication of waterways due to nitrogen deposition. (Final Draft, 2000)
NOx is identified as one of the major air pollution problems facing the U.S Environment control authorities. Poor atmospheric mixing and air inversions can increase ozone concentrations in populated areas to dangerous levels in a matter of hours. The inclusion of NOx in the air is a constant threat to the very young, old and the people having respiratory disease and heart problems. In order to control the NOx emission in the environment the U.S Government has implemented several measures. Since there origin the regulations imposed by the authorities have undergone many changes.
History of NOx Regulations
- The Clean Air Act was initiated in 1967 and was amended in 1970, 1977 and again in 1990.
- One of the 1990 amendments, called the Acid Rain Program, required all power plants to monitor NOx emissions.
The Acid Rain Program incorporates a two-phase NOx control strategy as outlined in the Table below. Phase I applied to boilers in selected eastern states. Phase II applies to all boilers (greater than 65 MW) throughout the US.......
