| OCR Text |
Show - 7 - Thus, these estimates predict the lowest NOx emissions at 75 m/s. However, it should be recalled that the penetration distance estimations, resulted in the opposi te trend. In Figure 5 these competitive penetration and temperature effects for all three burner configurations are shown. 'CXXl NOx 0%02 2000 1 ()(X) o 20/20 1~11.l"Y re1f~L-+, ~r:-;,'-;~lI ~'I -;-I I" I I I l~ IlJ)"C I I I I I : :j : /: I , 'I I I, /~ II I • I I; 1'0) I : '-...~--1 : I • .-~~I 7S 125 225 1.000 NOx 0%02 3000 2000 1000 o 20'12 ~c -- '----ll r;;';~I~ :~' I I tffeoct I I tHeel I I I )'~: I ~ I I IlCO I '/ I I I I" I I I I I I I I I I I :..--Tj i ' I I &CO I' 75 125 225 'tgas Im/s) 1.000 NOx 0%02 3000 2CXX> 1000 o 12 '12 ~J ,---- .... , r----- - 1 : /l~~ I f : A f . I II ifA I I ~t rc ll()(\ I I I C!lfeoc1 I I II II I r-r- I I I le<T1p. I I I ' C!ffeocl I I I :' ---'1 ~i: 75 125 225 Fig. 5 - Effect of burner configuration and operating parameter s on NOx For all the configurations studied, the 20/20 burner has the lowest NOx emissions at similar conditions of excess air level , air preheat temperature and gas injection veloci ty compared to the 20/12 and 12/12 configurations. These observations are in agreement with the theory of flame jet penetration. For air preheat levels of 1100 and 1300°C, the 20 / 20 burner has a minimum in NOx emission level at gas injection velocity of 125 m/s. At 75 mis, more combustion occurs in the oxygen r~ch combustion air stream, however the in-flame temperatures are relatively l ower. At 225 mis, the temperature effect has a stronger impact on the NOx emission level than the increased jet penetration distance, resulting in the highest emission leve ls for this configuration. This typical gas velocity dependence was observed for different levels of excess air and air preheat [3). For the 20/12 and 12/12 burner configurations, the jet penetration distance is less compared to the 20/20 configuration . This results in higher NOx emission levels at similar conditions. For these burners the lowest NOx emissions were observed at 75 m/s due to the reduced in-flame temperature characteristics . Increasing the gas injection velocity from 75 to 125 m/ s showed substantial changes on the NOx emission level due to the increased flame temperatures. Changes in injection velocity from 125 to 225 m/s resulted in limited effect on the NOx level due to the damping influence of jet penetration although at 1300 0 C air preheat the in-flame temperature effect became more significant . |
