| OCR Text |
Show 950 *C •NOx' •NO szonda 1500 Distance from quart [mm] Fig. 8: NO-concentration and temperature in the furnace-axis (Owing to the time-constant of NO-analyzer the value of N O is a bit less (60 s) than the registered temperature on the diagram). It can be seen in this Fig., that the temperature and NO-concentration increase quickly in the burners. The highest value of NO-concentration is obtained at the end of of flame, and this value decreases abruptly after that point and the NO-concentration measured in the axis remains a bit under the average value. It confirms the opinion, according to which the NOx-development is restricted to the flame. In the section following the flame, where there isn't any combustion, any greater quantity of N O doesn't develop even in case, if the temperture exceeds 1400°C. The rotational flame of "B" type burner has a cone-shape and the flue gas flows back in the axis. Fig. 9 shows the temperature- and NO-values measured at a distance of 205 m m from the burner by means a probe moved in cross-sectional direction. Here the NO-concentration in the axis of flame is hardly higher than the average (leaving) NO-concentration, at the same time it shows the maximum value around the burner axis at.a distance of 250 m m . The concentration-difference is about 10 ppmv. The N O shows its maximum value in the burner axis too, but this maximum value is nearer the burner than in case of the "A" type burner. ^5S s^i n=1,43 T7S 4T63- tirae [s] AxOr-bumer 60 1050°C a- 50 1 03 1,14 1.22 V 1 29 '"' * n=1.37 \ 1.4 V 4 ^ 1.61 time |s| AxOr-bumer 1150 "C time [s] "~ AxOr-burner Fig. 10: NO-concentration as a function of air-factor « § 8 § 8 8 § 9 8 § § probe distance [ m m ] Fig. 9: Temperature and N O in the cross section of flame 3.03 The effect of air factor The air factor is regulated automatically at the furnace-burners, as the increasing of air factor increases the scaling and decarbonization at the iron-containing metals. The air which is not used for combustion behaves as inert gas, it decreases the flame speed, [11], and the max. of flame temperature, especially above n = 1.1. A value of NO-concentration shown in Fig. 8 was measured in the leaving flue gas of "B" burner by keeping the operational parameters of furnace at a constant value and changing only the air factor at the following chamber-temperatures: 950, 1050 and 1150°C, and at a value of air factor of 1 0<n<1.5. 100 T 70 *>• E a so O z 50 40 30 - ... • • A T=1 250 "C . 1 i Burner " B " ' T=1350',C 1 i i | . I 1 1,1 1.2 1,3 1.4 1,5 1,6 Air factor, n Fig. 11: Effect of air factor |
