OCR Text |
Show PAPER NO. 38 Development of Reducing and Direct Fire Heating Technology Abstract: Yutaka Suzuki,Motofumi Kaminaka Hiroyuki Takashima Smi tomo Metal Industries, Ltd. A recent majar problem in continuous heat treatment furnaces for steel sheet is the achievement of high productivity without deterioration of Qual i ty. Therefore, as a heating method, a reducing and direct flame heating technology which leads to non-oxidation and Quick heating is at -tractive. The conventional technolog with pre-mixed gas burners have some problems, such as the limit of maximun steel sheet temperature, the difficulty of use of hot combustion air and the life of burners. To improve these problems, a new technology has been developed. At the first stage, a high performance burner was developed with a small test furnace which was made up of a heating chamber installed a test burner and a nitrogen gas cooling box for heated steel sheets. The features of the newly developed burner are: -well mixing in a burner nozzle with a swirling air flow. -forming a large single flame with a ring-slit burner nozzle. -stabilizing a flame with swiring flow and a cone type burner tile. At the second stage, various characteristics of the developed burner such as maximum steel sheet temperatures for non-oxidation heating, heating rate and NOX formation were investigated with a continuous annealing furnace model which was made up of a pre-heating chamber by waste gas, a heating chamber installed two burners,a soaking chamber with a radiant tube and a nitrogen cooling chamber. The results are as follows. l)Maximum non-oxidation heating temperature is more than 900°C. 2 ) H eat i n g rat e 0 f O. 8 t s tee Ish e e tis abo utI 0 0 °c / sec a t the con d i t ion of 1330°C furnace temperarure. 3)Converted concentration of Nox in the pre-heating chamber is less than 50ppm(ll%02). - 1 - |