96/02170 Selenium sampling and analysis in coal combustion systems

Abstract

The Clean Air Act Amendments of 1990 identified 189 elements and compounds that are classified by the U.S. EPA as hazardous air pollutants. Among these are 11 inorganic trace elements found in coal. The U.S. EPA developed and validated a sampling train (Method 29) for the measurement of these trace elements in flue gas from municipal waste combustors. This method has been used in several trace element sampling programs conducted at coal-fired utilities. This presentation addresses the difficulties experienced in measuring selenium (Se) at coal-fired facilities. The U.S. DOE conducted a Utility Air Toxics Assessment program consisting of emission measurements and material balance studies at eight coal-fired power plants. At all sites, the Se material balance closures were low. These results were presented at the third DOE Air Toxics Working group meeting (3/94). Among the potential causes for the bias and inaccurate analysis of Se in the process stream samples, non-representative samples, and the Method 29 train`s ability to capture gas phase Se from the flue gas. Since then, CONSOL R&D has conducted a sampling and analytical program with the objective of determining the reasons for the low Se material balance closures. This program focused on three major areas: themore » Se collection efficiency of Method 29, the potential for Se losses within the combustion system. The findings in these three areas will be discussed.« less