Organic Hazardous Air Pollutant Emissions from Gas Fired Combustion Sources Emissions and the Effects of Design and Fuel Type

Air emissions from industrial gas-fired combustion devices such as boilers, process heaters, gas turbines and stationary reciprocating engines contain hazardous air pollutants (HAPs) are subject to consideration under the U.S. Clean Air Act (CAA). HAP emissions test results for petroleum industry combustion devices were compiled into a database to allow extrapolation of the results to the full U.S. population of these devices and to allow analysis of HAP emission trends as a function of design and operating parameters. This paper presents new HAP emission factors based on field tests of gas-fired combustion devices used in the petroleum industry, discusses the effect of design and operating parameters on HAP emissions supported by both field and pilotscale tests, and compares these data to emission factors from other recent studies. Data from field tests of gas-fired petroleum industry boilers and heaters generally show very low emission levels of organic HAPs. Comparison of emissions data for boilers and process heaters, including units with and without various forms of NOx emissions controls, showed no significant difference in organic HAP emission characteristics due to design. This finding also is supported by results of pilot-scale tests with conventional and low-NOx burner designs. Field tests of units fired with natural gas and various petroleum industry process gases and pilot-scale tests in which gas composition was intentionally varied showed no dependence of organic HAP emissions on gas composition. Pilot-scale test data indicate that elevated organic HAP emission levels are found only under hypothetical extreme operating conditions associated with incomplete combustion. Such conditions are not considered safe or good operating practice within the industry.