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Show The Clean Air Act, originated in 1967, was subsequently amended in 1977 and later in 1990. The Clean Air Act, as amended in 1990, is hailed as the most sweeping environmental legislation ever passed by Congress [1]. Title I of the CAAA focuses on CO and ozone health standards and to a lesser degree on four other criteria pollutants namely, particulate, sulfur dioxide, lead and oxides of nitrogen. Under!itle I control ofNC?x and volatil~ organic compound (VOC) emissions are specified as a means to bnng ozone non-attaInment areas mto compliance with national ambient air quality standards (NAAQS). Ground level ozone, commonly referred to as smog, fonns in urban areas when VOCs and NOx react in the presence of sunlight and heat. Title ill and Title IV also serve the purpose of reducing VOCs and NOx emissions and are therefore also called ozone titles [1]. Title ~ ?f the CAAA ~eals ~ith em~ssions of hazardous air pollutants (HAPs) and establishes ceiling lImIts beyond whIch an Industnal source must apply control measures. One hundred and eighty nine HAPs are listed for regulation which include many of the volatile organic compounds emitted from industrial sources. Major sources of HAP emissions are required by the EPA to install Maximum Achievable Control Technologies (MACT) [1]. There is evidence suggesting that some NOx control strategies may actually lead to the fonnation of HAPs in gas burners [2]. This evidence was obtained from the study of an industrial-style diffusion flame burner under conditions representative of refinery process heaters. The principle VOC emissions included toluene and benzene. HAP species are often present in refinery fuel gases and certainly are present in the combustion effluent [2], therefore air toxic emissions will be an important issue in the development of ultra-low NOx control technologies for the refinery industries . . The development of low NOx burners has for many years continued to focus on mechanisms for staging and postponing combustion to lower peak temperatures in the combustion zone. The level of technology often applied in developing low NOx burners has relied heavily on historical experience and rules of thumb. Although initial progress in reducing NOx emissions in burners was dramatic, it became more difficult with time to achieve significant advances without sacrificing burner perfonnance. Thus, the need to better understand near-flame physical and chemical phenomenon of industrial scale burners was recognized. At the same time as these needs developed, the BERL came on-line. The BERL is a state-of-the-art research laboratory, designed to give researchers access to the advanced diagnostic capabilities available at Sandia while studying industrial gasfired burners. Since the laboratory's inception in 1992, several burners have been evaluated utilizing the advanced diagnostic tools available at the BERL. The burner selected for study in this program was a specially modified version of the Selas Model K988. The K988 is a radial-flame wall-mounted process heater burner that is marketed with NOx emissions guarantees as low as 25 ppm (at 3% 02) in some industrial applications. This burner was selected for study as a burner that promises to yield insights into low NOx behavior. The Selas burner has been installed in four plants, one with almost three years of operating experience at 2300°F. It has proven to be a burner requiring little maintenance and is mechanically sound. The commercial natural-draft burner was specially modified for this study by separating all passageways so that fuel and air could be independently metered to each stage and so that the test furnace could be maintained at positive pressure. Most of the tests were run within flow ranges achievable by inspirating fuel gas. The burner, in field applications, utilizes fuel gas pressure to aspirate combustion air into the primary and secondary registers while natural draft draws combustion air through the tertiary register. Interchangeable secondary injector nozzles were constructed to permit variation of mixing behavior within the furnace. A test plan was developed around the K988 burner that would exploit the capabilities of the BERL while parametrically evaluating operation parameters that were expected to impact NOx, CO and hydrocarbon emissions. During the tests conducted at the BERL, chemiluminescence imaging was used to identify regions of expected NOx formation in the flame. These were correlated with measured furnace exhaust NOx concentrations and burner operating conditions. Mie scattering and laser doppler velocimetry were employed to characterize the mixing behavior and flow field generated by the burner. This study demonstrates the utility of the BERL diagnostics for evaluation and potential 2 |