A maker of smoke-stack sampling equipment for power and process industries needed some help meeting the U.S. Environmental and Protection Agency’s rules.
Under the Clean Air Act, the EPA requires all coal-fired electric generating
plants to monitor and report mercury emissions from their stacks. Coal-fired
plants are the single largest source of mercury emissions in the country. To
meet the requirements, accurate measurement devices are a necessity.
The amount of monitoring needed at a particular source plant is a function
of its current output levels. In some cases, high levels of mercury emissions
require continuous monitoring. Accurate measurement is most critically affected
by one thing: the amount of moisture content in the gas. It is imperative to
keep the sampling draw on the stack gas above the dewpoint to prevent
condensation and measurement variance. NIST–traceable calibration standards
from the National Institute of Standards and Technology are used for maximum
accuracy, and readings are taken based on a dry-standard cubic-meter basis for
the gas sample.
A power plant specified single-end tubular heaters from Pittsburgh-based
Chromalox to keep the stack-probe gas temperature sampling tube dry and the
measurement error-free. The design also extended probe life by protecting
against corrosion that could be caused by condensation. For continuous
monitoring operation environments, using heaters like those from Chromalox could
make the difference between the ability to ratify compliance data without
interruption and having a gap in data recording due to a failure that could
result in costly fines to the site owner.
For more information on Chromalox heat and control products, go to www.chromalox.com.
Single-End Tubular Heaters Control Mercury Emissions
November 8, 2011