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Show The R S B was originally developed for use in oil field steamers, and has now been applied to industrial boilers and process heaters. The R S B technology has the following advantages (See Reference 1): • Lower NOx at equivalent excess air relative to competing perforated metal fiber burners • No combustion noise when operated over the specified range • Broad operating range and flame stability, allowing for high levels of F G R or use with low Btu fuels Two mechanisms are believed to contribute to the NOx reduction observed in the RSB. The first mechanism is a rapid post-flame cooling of each blue-flame zone. By spreading the flame over a large burner surface, and by combusting a thoroughly premixed air/fuel mixture, the combustion occurs at a uniform temperature, containing no rich/lean fluctuations. This uniform temperature limits the production of thermal NOx, which is exponential with temperature. A second mechanism is the internal F G R effect produced by the entrainment of the products of combustion from the adjacent radiant zones into the blue flame. In the radiant zone, the combustion reaction is completed a few millimeters downstream of the burner surface. The combustion products initially serve to stabilize the attachment of the blue flame above the perforated portion of the burner as well as to introduce lower temperature gas into the blue flame, thus reducing NOx. Before the completion of the work described in this paper (Reference 2), the R S B was demonstrated to achieve 30 ppm NOx at moderate levels of excess air and 9 ppm NOx at high excess air. To lower the stack 0 2 levels and obtain a high efficiency system, F G R was selected as the appropriate NOx reduction strategy based on sub-scale testing. The goal of the recently completed work was to demonstrate the use of F G R in a full-scale R S B burner with N O x emissions below 9 ppm, C O emissions below 50 ppm, stack 0 2 below 3%, and FGR levels under 30%. While these goals were achieved at several test points, the burner also showed the ability to operate with a stable flame at much higher levels of FGR. These goals were accomplished in a 62.5 MMBtu/hr (18.3 MWt h ) oil field steamer used for demonstration and data acquisition. 2 |