NOx Emissions
Standards
History
The Clean Air Act of 1970 established
a major role for the federal government in
regulating air quality. The act was further
extended by amendments in 1977 and,
most recently, in 1990. The 1990 CAAA
is one of the most complex and comprehensive
pieces of environmental legislation
ever written. It authorizes EPA to
establish standards for a number of atmospheric
pollutants, including sulfur dioxide
(SO2) and NOx.
Two major portions of the CAAA relevant
to NOx control are Title I and Title
IV. Title I establishes National Ambient
Air Quality Standards (NAAQS) for six
criteria pollutants, including ozone, while
Title IV addresses controls for specific
types of boilers, including stationary coalfired
utility power plants. Title IV is often
referred to as the Acid Rain Program.
Title IV uses a two-phase NOx control
strategy. Effective January 1, 1996, Phase
I established regulations for Group 1
boilers: dry-bottom, wall-fired boilers
and tangentially fired (T-fired) boilers.
In Phase II, which begins on January 1,
2000, lower emissions limits are set for
certain Group 1 boilers, and regulations
are established for Group 2 boilers,
which include cell-burner, cyclone,
wet-bottom wall-fired, and other types
of coal-fired boilers.