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Show The structure is shown in Fig.2. 13A-city-gas (88% methane) was used as the fuel. A steel plate of 1 mm thick, on which a monitoring thermocouple (0.3 mm AlumelChromel) was welded, was inserted into the flame until the plate temperature reached 750°C (typical temperature for the annealing.process). Rapid cooling by nitrogen impingement was done in the upper auxiliary chamber to freeze surface reactions. The oxidizing behavior of flames were examined varying the overall equivalence ratio (the fuel to air ratio normalized by the stoichiometric one), the distance, L, between the burner face and the steel plate, and the type of the burner. Some of the burners showed the possibility of nonoxidizing heating as briefly described in Table 1, though the state of surface obtained were very sensitive to the operating condition. For example, the distance L was one of the essential factor to accomplish non-oxidizing heating, and one of the results showed that the allowance for L was less than 20 mm for the flame tested. It implies that surface oxidation depends on chemical processes in gas phase. Moreover, the oxidizing behavior changes significantly with the burner type, even if the mixture equivalence ratio and the distance L were unchanged. The fact implies ' the importance of physical processes in a furnace as well. 3. APPLICATION TO FULL SCALE FURNACE Based on the results of burner development work as previously mentioned, a practical version was designed aiming at application to a full-scale continuous galvanizing line (CGL). The burner, as schematically shown in Fig.3, incorporates a number of y-shape nozzles which ensures sufficient mixing between fuel gas and combustion air. It is also capable of employing high temperature air up to 550°C, unlike the conventional premixing type burner particularly designed for the same Table 1 Burner YJT ' EFB SlS Possibility of nonoxidizing direct flame heating Burner type and swirl intensity Nozzle mixing Medium swirl Premixed Strong swirl Premixed No swirl Possibility of realization Pcssib~e at 750°C, highly depending on deslgn parameters Impossible, distinct oxidation at 650°C Possible at 750°C - 4 - |