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Show ha a a 1400 1300 1200 IV 1100 Bt*nar Ingot-* Top Inojot'A Bottom Ingof-eimr •* fcgot-B Wall otda lngot-C Top Ingot -C Bottom • • - SooWng Stag* Fvmaoi Ftsnaai Tamp Tamp (Bunar <Anti ,S»*). tk#n» Si<»a> 300 200 100 10 11 Time tM Fig. 21. Temperature raising characteristic of the conventional burner in top one way soaking pit (Fuel: Butane, Pit capacity: 240 ton/pin) 300 200 I Of I 4&. 2 6 10 11 Fig. 22. Temperature raising characteristic of Model E low N O x burner in a top one way soaking pit (Fuel': Butane, Pit capacity: 240 ton/pit) Steel ingot of the side opposite to the burner whose temperature is hard to increase, increased fast by the low NOx burner, and uniform distribution of steel ingot temperature was obtained* These results are shown in Table 2. Incidentally, improvement of fuel cost was about 5%. Figs. 23 and 24 shows photos of the flame shape of the heavy oil firing, top one way soaking pit and N O x values of the one heat cycle, respectively. With the conventional burner, N O x became extremely high as the local high-temperature region was created because the combustion reaction took place quickly from inside the port block situated near the burner tip. Moreover, N O x becomes very high in the soaking stage because it is greatly affected by combustion air temperature, furnace internal temper ature and excess air ratio. On the other hand, with this low NOx burner (Model E), combustion reaction inside the port block is for stability of flame, the main reaction region exists inside the furnace, and being a long flame, combustion takes place over the entire furnace interior. As the results of this, influence of combustion air temperature, furnace internal temperature and excess air ratio are small, similar to with the previously stated results of combustion test, and the percentage of NOx> reduction of 50 ~ 75% was obtained, and no change for the worse of fuel unit was observed. Figs. 25 and 26 show burner con- 11-12 - |