OCR Text |
Show furnace atomic adsorption spectroscopy (GFAAS), and cold vapor atomic adsorption spectroscopy (CV AAS) (for Hg only) according to EPA SW846 Method 6010 (ICAP) and 7000 Series (AAS) Methods. The detection limit for trace metals using ICAP is about 0.3 to 7 Jlg/Nm3 for a 4 hour (5 Nm3) sample, depending on the specific element. For elements such as lead, selenium, cadmium, and arsenic, the detection limit can be lowered one to two orders of magnitude by using the GFAAS analysis. The detection limit for Hg is about 0.01 Jlg/dscm using conventional CV AAS analyzers; however, new analytical instrumentation has the potential to achieve detection limits an order of magnitude lower. Iron and aluminum, major constituents of coal ash, are known interferences for ICAP analysis of many metals requiring the use of matrix modifiers during analysis. Key modifications of the sampling method included increasing the quantity of reagents to prevent depletion due to high S02. Hexavalent Chromium Sampling for hexavalent chromium (Cr+6) was performed using EPA SW846 Draft Method 0013 shown in Figure 1 b. The sample train utilizes a recirculating spray quench probe to ensure the flue gas is rapidly quenched and all of the highly reactive hexavalent chromium species are immediately absorbed. Potassium hydroxide solution from the first impinger is pumped to the probe at the nozzle tip. Sampling is performed isokinetically. The train does not employ a particulate filter. Sample train components were analyzed by ion chromatography with a post column reactor utilizing diphenyl carbazide according to Method 0013. The detection limit for hexavalent chromium is about 0.03 Jlg/Nm3 for a 4 hour (5 Nm3) sample. Due to the high S02 concentrations in the flue gas a greater concentration KOH solution was used to maintain a basic adsorbing solution for the Cr+6. This resulted in an analytical interference detected in the blank samples, precluding a definitive evaluation of test results. Hydrogen Halides and Halogens Sampling for hydrogen halides (HCI, HF) and halogens (CI2, F2) was performed using EPA Method 26A, "Determination of Hydrogen Halide and Halogen Emissions From Stationary Sources" shown in Figure lc. Flue gas samples are withdrawn isokinetically with from the source and pass through a heated probe and a filter into dilute sulfuric acid and dilute sodium hydroxide olutions. Hydrogen halides are collected in the sulfuric acid solution and the halogens pass through the sulfuric acid and are collected in the sodium hydroxide. The halide ions in the 4 |