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Show IGT has teamed with Maxon Corporation (Maxon), one of the major industrial burner manufacturers in the United States, to develop an ultra-low emission, gas-fired cyclonic burner for directair heaters. Tests conducted on the 1 x 106 Btulh (293 kW) bench-scale burner, shown in Fig. 1, have demonstrated that NOx emissions were reduced to as low as 0.6 vppm with CO and THC under 3 vppm (at 15% 02) when the burner was operating at 80% excess air.s Stabilization of the main flame at such high excess air was achieved with a separate tlame stabilizer operating continuously at relatively low excess air. Since combustion temperatures in the stabilizer are relatively high, a significant portion of NOx emissions was produced in the stabilizer, limiting further reduction of NOx formation. Operation at higher excess air in the main combustor would require further improvements in the ignition and stabilization of the main flame. The purpose of the program was to determine if a dc electric field can provide additional stabilization in the high-speed swirl flow existing in the cyclonic combustor and thus allow operation at higher excess air and lower NOr From a practical point of view the ability to operate at current NOx levels with an electric field stabilizer instead of a flame stabilizer would lead to significant reductions in the cost of the burner and its operational complexity. III. DESCRIPTION OF BURNER Measurements were made in the existing pilot-scale cyclonic combustor fabricated by Maxon and installed in IGT's Applied Combustion Research Facilities (ACRF). Figure 1 shows the test setup including the combustion system, operating and control system, and the measurement and data acquisition/reduction system. The premixed natural gas/air-fired combustor is composed of a main combustion chamber and a smaller flame stabilizer chamber, each supplied by two tangential nozzles. The outlet cross-sectional area of each nozzle can be adjusted to control the nozzle velocity. The operating and control system provide a sequenced automatic start-up, inteJlock protection, individual control of the flow rate, as well as flow balance between the nozzles. A computerized data acquisition and reduction system facilitated the recording, storage, and real time output of data obtained from the measurements of gas and combustion air flow rates for both the main burner and stabilizer, gas temperature, flame sensor signal, refractory wall temperatures, and flue gas oxygen concentration and combustion emissions (NO/NOx' CO, and THC). 3 |
