Single-End Tubular Heaters Help to Control Mercury Emissions

Chromalox catalog tubular lp

The Challenge

A world leader in the manufacture of smoke stack sampling equipment for power and process industries needed some help meeting EPA rules. The Environmental Protection Agency (EPA) issued a mandate called the Clean Air Mercury Rule (CAMR) that requires all coal fired electric generating plants to monitor and report mercury emissions from their stacks by January 2009.  Coal fired plants are the single largest source of mercury emissions in the country. The goal is to reduce these emissions from current levels of 48 to 50 tons per year to less than 20 tons per year, nearly a 70% reduction. In order to achieve this reporting target, accurate measurement devices are a necessity.  In addition, 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 dew point to prevent condensation and measurement variance. NIST–traceable calibration standards (National Institute of Standards and Technology) are utilized for maximum accuracy, and readings are taken based on a “dry standard cubic meter” basis for the gas sample.

The Solution

Chromalox single-end tubular heaters were specified to keep the stack probe gas temperature sampling tube dry and the measurement error free.  This design also served to extend probe life by protecting against corrosion that could otherwise be caused by condensation.  For units in continuous monitoring operation environments, this may 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.


  • Prolonged life in a continuous operating application
  • Corrosion resistance
  • Uniform heat transfer