EUEC 2012 Presentations

Please join us at the 2012 Energy, Utility & Environment Conference Jan 30-Feb 1 in Phoenix AZ where we will present two papers:

  • Upper Predicted Limits for HAP Emissions from Coal-Fired EGUs Using Stack Test and CEMS Data
    Jonathan O. Allen and Ralph L. Roberson
  • Effect of Plant Operations on Trace Metal Chemistry in FGD Liquor
    Jonathan O. Allen, Derek A. Eggert, and Corey A. Tyree.


Upper Predicted Limits for HAP Emissions from Coal-Fired EGUs Using Stack Test and CEMS Data
Jonathan O. Allen and Ralph L. Roberson

Abstract

EPA has proposed emission limits for Hazardous Air Pollutants (HAPs) emitted by coal-fired electric utility steam generating units (EGUs). Generally, EPA requires compliance with these emission limits based on continuous measurements. Ideally HAP emission limits would have been based on long-term continuous data from the entire fleet of EGUs. However, HAP emission data to characterize emissions from the EGU fleet were mainly available as short-term stack tests, and EPA based its proposed HAP emission limits on these data. Stack tests measure emissions over a short period of time, and so include no information about correlated emissions or emissions during infrequent events such as a unit startup. We have developed a method to correct long-term emission limits calculated from stack test data using the available continuous emission monitoring system (CEMS) data. In this method an empirical correction factor, R, is determined as the ratio of the 99th percentile of historical 30-day emission averages to emission limits that would have been calculated from continual stack tests of individual top performing units. For mercury and PM these ratios were in the range 1.07 to 3.89, and indicate that long term emission averages were higher than would have been calculated from stack tests alone.

 

Effect of Plant Operations on Trace Metal Chemistry in FGD Liquor
Jonathan O. Allen, Derek A. Eggert, and Corey A. Tyree.

Abstract

Wet flue gas desulfurization units (FGDs) may be used to capture a significant portion of mercury, selenium, and other hazardous air pollutants (HAPs) from flue gas. However, wet FGD units transfer gas phase constituents into the FGD slurry, which itself generates a waste stream. The US EPA is currently establishing guidelines for FGD wastewater effluent which will likely include discharge limits for a range of metals. Wet FGD wastewater composition is highly variable within and among FGDs due in part to liquid-solid partitioning. In order to better understand the causes of partitioning of trace metals, we have conducted an extensive 6-month long field sampling campaign that covered 15 full-scale FGD systems. Partitioning of trace metals in the FGD systems resulted in large changes in dissolved metals concentrations; Hg and Se concentrations were in the ranges 0 – 97 ppb and 80 – 15,000 ppb, respectively. Here we merge plant operational data with the trace metals data in order to better understand oxygen, sulfur, mercury, and selenium chemistry in wet FGD slurry. Changes in dissolved metals concentrations were coincident with changes to the overall oxidation state of the FGD system, as indicated by the oxidation-reduction potential (ORP).