| OCR Text |
Show 950 *C 80 T Distance from qnarl [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 N O x - 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. time [s] AxOr-burner 80 70 g 60 Q. a. 50 Z 40 30 20 1050*C 1 03 1.14 • 1,22 V n=1.37 \ 1.4 V 1,!2 V^, 181 time [s] AxOr-bumer 1150 *C 80 70 | 60 a. a. 50 Z 40 30 -f 20 - - - 1.03 1.06 n=1,1 3 1.25 1.3 i.:i9 " \ 1,43 time Is] " AxOr-burner Fig. 10: NO-concentration as a function of air-factor W W to W ^ probe distance [mm] 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 80 70 60 50 40 30 20 • • A T=1 S. *v 250 °C T=135 Bum J-C 5T"B" j i j i i \ i i i 1 1 1.2 1.3 1,4 1,5 Air factor, n Fig. 11: Effect of air factor 1,6 |
