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Show Paper No. 14 Development and performance evaluation of the new low-NOx CGRI burner for use with high air preheat Andrzej Sobiesiak1, Shahrzad Rahbar2 and Henry A. Becker3 • Centre for Advanced Gas Combustion Technology 'Department of Mechanical Engineering 2 Department of Chemical Engineering Queen's University Kingston, Ontario K 7 L 3N6 2Canadian Gas Research Institute 55 Scarsdale Road Don Mills, Ontario M 3 B 2R3 Abstract The CGRJ burner is a multi-jet, non-premix, gas-fired burner intended to give low-NOx performance at high air preheat. It was invented at the Canadian Gas Research Institute. Following tests in a tunnel furnace at CGRI, a more detailed investigation was carried out in the Furnace Research Laboratory of the Centre for Advanced Gas Combustion Technology. The performance of single burners and of banks of three firing into the C A G C T research furnace was studied, with maximum combustion heat releases of 300 to 400 k W per burner. The variables included manipulatable burner-design variables, air preheat, excess air level, firing rate and furnace load. The results confirm the low-NO, characteristic and provide guidance on how to optimize design and operation to minimize N O x and achieve acceptable combustion stability. The N O x emission levels ranged from 2 to 40 ppm, with the high levels being reached only at very high furnace exhaust-gas temperatures. From a theoretical analysis coupled with various lines of experimental evidence, correlations have been developed that predict flame size and provide guidance for scaleup. There is scope for tailoring the flame shape as well as the length. Combustion intensities (combustion heat release rate per unit flame volume) of up to 650 kW/m3 were attained. The low-NOx characteristic is achieved entirely through burner and furnace aerodynamics, rather than by costly brute-force methods such as mechanical fluegas recirculation. The burner poses exceptionally interesting problems of combustion aerodynamics and mixing coupled with chemical reaction. Some aspects of these problems are treated within the paper, while others are being pursued in studies currently underway. 1. Introduction The achievement of low NOx emissions in conjunction with high air preheat in industrial furnaces poses special challenges. The preheat is usually gotten by recuperation from the furnace exhaust gases, an energy conserving strategem. Mechanical fluegas recirculation through the 1 |