OCR Text |
Show observed. Increasing the nitrogen content in the natural gas and oxygen resulted in higher N O x emission. Higher V and wider L resulted in ultra low N O x emission even if a few percent of nitrogen was contained in the natural gas or oxygen. Ultra low N O x emission has been established with the FDI oxy-fuel combustion. 4.4 FDI flat flame oxy-fuel burner To improve total radiative heat flux while maintaining low N O x emission, an innovative FDI flat flame burner which creates widely-spread flat flame along the surface of molten glass was invented and tested. Figure 17 shows the effect of V on total radiative heat flux. Three levels of V (35, 50 and 70 m/s) were tested with L set at 100 m m and 0 at 10 degrees. A m o n g the three levels of V tested, the lowest V (35 m/s) showed the highest heat flux distribution followed by the highest V (70 m/s). For V=50 m/s heat flux distribution showed somewhat minimum. The effect of V does not appear to be straightforward and will be discussed in the later section along with the effect of V on NOx. Figure 18 shows the effect of L on total radiative heat flux. Three levels of L, 100, 200 and 300 m m were tested with V set at 35 m/s and 0 at 10 degrees. High total radiative heat flux was observed at L=50 and 100 m m and there was little difference between them. Total radiative heat flux with L=200 m m was lower than that at L=50 and 100 m m . Figure 19 shows the effect of the angle 0 on total radiative heat flux. Four levels of 0, 0, 5, 10 and 15 degrees were tested with V set at 35 m/s and L at 100 m m . Total radiative heat flux at 0=0 degree, which is the FDI burner, was very low. A n clear improvement of total radiative heat flux by 20 % was observed at 0=5 degrees for all the six measurement points. Further inclination of the oxygen nozzles (0=10 and 15 degrees) improved total radiative heat flux at the near burner region with stightly decreased total radiative heat flux further downstream from the burner. This was caused by the transition of the collision point toward the burner and the decrease of flame length by the enhanced mixing between natural gas and oxygen. The highest average total radiative heat flux was established at 0=10 degrees. The distribution of radiative heat flux became flat and a widely-spread flat flame was observed at 0=10 degrees. Figure 20 shows the effect of V on NOx emission. Three levels of V (35, 50 and 70 m/s) were tested with various combination of L and 0. N O x emission decreased with increase 10 |