OCR Text |
Show • BACKGROUND Test methods for characterizing air emissions from stationary sources were initially developed by EPA under the Clean Air Act. Level 1 Site Assessments employed techniques such as the source assessment sampling train (SASS), now EPA Method 0020, for combined measurement of particulate, particle size, and PAH emissions. EPA test methods for characterization of emissions from hazardous waste incinerators have been developed for multiple trace metals, trace metal species such as hexavalent chromium, aldehydes (carbonyls), halogens, volatile and semivolatile organic compounds, and other non-criteria pollutants. These methods are the basis for more generally characterizing stationary sources. Some have been developed for applications beyond hazardous waste incinerators such as municipal solid waste combustors and medical waste incinerators. However, few methods have been fully validated for application to coal fired utility boilers. EER's recent experience in air toxics characterizations at three coal-fired power plants has demonstrated the need for caution when applying these methods to this application. MEASUREMENT METHODS The test methods selected for characterization of air toxics emissions from coal fired utility boilers comprise integrated sampling methods; i.e., a sample of the flue gas is extracted over a period of time and the average emission for the sampling period is determined. The sampling trains for key measurements are illustrated in Figure 1. The figure illustrates the sampling trains with modifications used by EER for sampling in coal fired boiler flue gas, which are summarized in Table 1. These are discussed briefly below. Trace metals Sampling for trace metals was performed using EPA Method 29, "Determination of Metals From Stationary Sources" shown in Figure 1 a. Flue gas samples are iso-kinetically withdrawn with from the source with heated probe. Particulate is collected in the probe and on a glass- or quartzfiber filter. Gaseous metal species are collected in an aqueous acidic solution of hydrogen peroxide and an aqueous acidic solution of potassium permanganate (for Hg only). Sample train components were analyzed by inductively coupled argon plasma spectroscopy (ICAP), graphite 3 |