OCR Text |
Show Regulations Existing regulations for N0X fall into three categories: (a) ambient air quality standards, (b) stationary new source performance standards, and (c) mobile source standards. To provide a basis for ambient air quality standards, available information was compiled and analyzed by an advisory committee. The areas covered included not only atmospheric chemistry, but also effects on materials, plants, and humans. A major conclusion was that the ambient concentration of NO2 should be used as the basis of the standards. This was based on two main points. First, NO is rapidly converted to NO2 in the atmosphere and, second, toxicology studies of NO and NO2 show that NO2 is the more hazardous form at concentrations found in the atmosphere. As required by the Clean Air Act of 1970, National Ambient Air Quality Standards (NAAQS) for N02 were set in 1971. The primary standard is based on a level required to protect public health and the secondary standard protects the public welfare from any known or anticipated adverse effect associated with the presence of air pollutants in the ambient air. Both standards were set at. 100 yg/m3 for N02. \ L - The Clean Air Act of 1970 required the EPA Administrator to set standards for new sources. The only source category for which Federal New Source Performance Standards (NSPS) are in effect is steam generators with a thermal input greater than 73 MW (250 X 106 Btu/hr). The initial NSPS for this class of equipment burning gas, oil, and coal (except lignite) became effective in 1971. The coal standards were revised in 1979 and a coal-derived liquids standard was added. The lignite standard, which was promulgated in 1978, is based on firing method; however, cyclone-fired boilers are only allowed for fuel containing greater than 25 percent lignite from North Dakota, South Dakota, or Montana. The NSPS are summarized in Table 2. The basis of these regulations is combustion modification to reduce NO^ formation, and compliance is achieved with flue gas recirculation staged combustion and/or altered burner designs. v 3-3 |