API Publ 4720:2002 pdf download.Comparison of API and EPA Toxic Air Pollutant Emission Factors for Combustion Sources
Major gaps in air toxic emission factors for combustion sources include: • A lack of data for dioxin/furan emissions for most source categories. This gap may be important because EPA’s Per- sistent Bioaccumulative Toxic regulation is focusing attention on these chemicals. The reporting threshold for the dioxin and dioxin-like compounds is 0.1 grams per year. While the relative potential for dioxin emissions from gas- fired heaters is generally considered very low, the industry needs a reasonable and defensible position regarding their potential to emit dioxin. • A lack of data for metals emissions for reciprocating internal combustion engines (RICE) and gas-fired gas turbines. While it is likely that metal emissions from these sources are small, there are no published emission factors to con- firm this assumption. • No consistent list of target compounds used in the emission testing. Not all HAPs were tested for in all tests. For example, newer testing of reciprocating engines using Fourier Transform Infrared (FTIR) techniques included many more individual organic HAP compounds than older testing, which tended to focus on aldehydes, benzene, toluene, and xylene. Thus, there is a lack of data for certain organic HAP emissions from certain source categories such as gas- fired and fuel oil-fired boilers and heaters. Similarly, not all metals or polycyclic compounds were tested for in all tests. This results in isolated gaps for specific organic HAPs, polycyclic compounds, and metals throughout the database.
There are several inconsistencies in the reported emission factors. For example, several metal EPA emission factors for gas- fired boilers/heaters are 10-50 times lower than the API emission factor. There are many factors that contribute to these inconsistencies, including: • Differences in source populations and operating conditions. Differences in the design, operation, and maintenance of sources may contribute to emissions factor inconsistencies. For example, the EPA external combustion emission fac- tors based primarily on tests at large electric utility boilers, while the API factors based on petroleum industry boilers and process heaters. • Differences in sampling and analytical methods. Measurement methods are continually improving. Different mea- surement methods may contribute to emission factor inconsistencies. For example, formaldehyde may be measured using CARB method 430, EPA method SW-846, or the FTIR method. These different methods can have different biases in the methods, different detection limits, and different data reduction procedures. • Differences in the treatment of detection limits. Many tests of combustion sources result not in an emission rate but in knowledge that the pollutant was not present at or above the limit of detection of the test method used. How the method detection limits are reported and used to develop composite emission factors may contribute to emission fac- tor inconsistencies. An assigned value of 1 / 2 of the minimum detection limit is generally used in calculating emission factors. For example, the detection limit for benzo(a)pyrene is a factor of 200 lower if the sample is analyzed using high resolution gas chromatography/high resolution mass spectrometry rather than low resolution gas chro- matographe/low resolution mass spectrometry.
API Publ 4720:2002 pdf download
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