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Improving Measurement for Smokestack Emissions - Workshop Summary



Rodney A. Bryant, Aaron N. Johnson, John D. Wright, Tamae M. Wong, James R. Whetstone, Michael R. Moldover, Iosif I. Shinder, Scott Swiggard, Chris Gunning, David Elam, Tom Martz, Eric Harman, David Nuckols, Liang Zhang, Woong Kang, Salvator Vigil


The complex flow conditions inherent in power plant smokestacks make accurate flow measurements challenging, which in turn limits the accuracy of hazardous emissions measurements. While stack composition measurements are assessed daily via comparison to a certified gas standard, the flue gas meter is only calibrated once a year via the flow relative accuracy test audit (RATA). In most cases the flow RATA is performed using an S-type pitot probe whose performance can be adversely affected by the complex flow conditions (i.e., asymmetric velocity profile and swirling flow) typical in stacks. NIST sponsored a workshop to discuss the current and future flow measurement needs with stakeholders in the electric power generation industry. The meeting included regulators, owners of stationary sources, stack testers, equipment manufacturers, national metrology institutes from other countries, flow measurement laboratories, and accreditation bodies. During the workshop participants gave presentations on several topics including accreditation, modifications to EPA regulations that will improve flow measurement uncertainty, flow RATA accuracy for the S-type pitot probe as well as for the prism probe and spherical probe, and the accuracy of different continuous emissions measurement systems (CEMS) in stack applications. NIST gave tours and presented results from its research facilities specifically designed to improve the accuracy of stack flow measurements. At several points the workshop participants divided into small groups to discuss presentations made by NIST and other participants. Group discussions centered around three topics including 1) Air Emission Testing Bodies, 2) Accuracy of RATA and CEMS Flow Measurement Methods, and 3) how NIST research facilities can be best used to help improve flow measurements in industrial applications.
Special Publication (NIST SP) - 1228
Report Number


AETB, Carbon Mass Balance, CEMS, CO2 Emissions, Flow Measurement, Method 2F, National Fire Research Laboratory, Non-nulling, Prism Probe, RATA, S-probe, Scale-Model Smokestack Simulator, Spherical Probe, Tracer Gas Dilution


Bryant, R. , Johnson, A. , Wright, J. , Wong, T. , Whetstone, J. , Moldover, M. , Shinder, I. , Swiggard, S. , Gunning, C. , Elam, D. , Martz, T. , Harman, E. , Nuckols, D. , Zhang, L. , Kang, W. and Vigil, S. (2018), Improving Measurement for Smokestack Emissions - Workshop Summary, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed May 24, 2024)


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Created September 21, 2018, Updated March 12, 2020