Continuous Emission Monitors

A complex combination of regulatory bodies determines which pollutants must be measured and in what manner the measurement must be made for a specific plant. Figure 5.12.6 shows the complexity of laws that affect the CEM design for a plant. For example, if the plant falls under the incentive program in Title IV of the 1990 CAA, this plant has an emission allowance in tons of SO2 per year. It must continually monitor its mass flow and accurately record its total mass emissions in tons per year for the entire period. This requirement means that a data acquisition and reporting system must be incorporated into the CEM sys tem (see Figure 5.12.7). A plant in a nonattainment area or region can be required to reduce NOx to a greater degree than that required in Title IV. This requirement could mean installing control equipment and measuring ammonia and other pollutants.

Table 5.12.1 shows the pollutants measured for various applications.

Table 5.12.2 summarizes the type of monitors and the concentration measurement range available for several CEM systems. Performance specifications for CO and O2 are given in Table 5.12.3. Dilution-extractive systems prefer a pulse of chopped fluoresence for SO2 analysis.

NO is generally measured using chemiluminescence (see



Unicon 700

Analyzers ^

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