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Show at 600°C. Schematic of the burner design is shown in Figure 4. One distinct feature of this burner which sets it apart from any other burner is non-circular cross-section of the four air ports. The burner has an air lance within the fuel pipe, thus resulting in the annular flow of the fuel for all firing condi tions. EXPERIMENTAL METHODOLOGY. Oxygen can be added by different means shown in Figure 5. The CAGCT setup is pictured in Figure 6. Oxygen is added via a sparger into the combustion line upstream of the burner to ensure good mixing. The enrichment levels investigated were 23, 25 and 27%, with the excess oxygen ratio kept constant at 1.1. The fuel was natural gas of the following composition j CH4 = 94.74%, C2H6 = 2.60%, C6Hs = 0.28%, C4H10 = 0.04%, CO2 = 0.55%, N2 = 1.79%. Fuel Lower Heating Value was 37.88 MJ/m3. The decreased amount of nitrogen in combustion air normally causes a reduction in the air jets momentum and thus a smaller flame envelope. The burner design features an air lance which provides an option for creating a second oxygen-fuel mixing interface (inside the fuel jet) and a local increase of air jet momentum. Operation of the burner with ambient air and the lance air on, produced flame of smaller diameter but much longer than that for standard operation without the lance. This observation led to the hypothesis that the negative effects of the decreased momentum of the primary air jets could be offset by exercising the lance air option when oxygen enrichment was tested. The experiments consisted of input-output and detailed in-flame measurements. In the input-output measurements the furnace wall temperatures, the heat flux density to the floor, the flue gas temperature, NOx , CO, CO2 and O2 were measured for varying oxygen enrichment levels and three firing rates. The in-flame measurements included temperature profiles. The baseline performance of the burner with respect to NOx emisions for varying temperature of the combustion air (no oxygen enrichment) was established first by covering the combustion chamber floor with a blanket of refractory material. This procedure prevented the heat transfer to the floor and allowed significant increases in both the combustion air and the flame temperatures. All the oxygen enrichment tests were done with the floor uncovered. EXPERIMENTAL RESULTS AND DISCUSSION. The burner generated stable and symmetrical flames for all operating conditions. The baseline flame with no oxygen addition was transparent only with some yellowish flamelets. There was a noticeable increase in the flame luminosity with the oxygen enriched air. Flames with the lance air on became longer and acquired blueish apperance. 3 |