| OCR Text |
Show 2 the continuous annealing furnace shown in Figure 1. As for the reducing and direct-fired flame heating, the following advantages are enumerated compared with the indirect heating. 1) It is possible to heat the steel sheet rapidly. 2) The heating response is excellent. 3) The production line is compact. Therefore, the reducing and direct-fired flame heating was used in combination with the indirect heating. The roles of the reducing and direct-fired heating are rapid heating and the role of the indirect heating is uniform heating. The nozzle-mixed burner, which is generally applied in the iron and steel works for safety and stability, forms turbulent flow to improve mixing of fuel and air. Conventionally, it has been thought that the nozzle-mixed type burner is less suitable for the reducing and direct-fired flame heating than pre-mixed type burner, because the mixing of the nozzle-mixed type burner is inferior to that of the pre-mixed burner and unreacted oxygen remains in the flame. However, w e have confirmed that the nozzle-mixed type burner properly designed has the reduction heating ability.a3) With increasing productivity in recent years, improvement has been demanded not only in the heating ability but also the reduction ability. In this report, w e have studied of improvement of reducing-flame burner. 2.Reduction Mechanism The oxidation/reduction reaction of iron has been well researched, and the reactions of Fe-CO-C02 and Fe-H2-H20 using equilibrium theory are well known. Figure 2 shows the oxidation/reduction condition between steel temperature and CO/C02, H/h^O ratio. In conventional combustion conditions in the reducing and direct-fired heating furnace, CO/C02 and H / H p ratio are lower than 1 usually, and reducing ability of the reducing flame cannot be explained only by equilibrium theory. It is n o w thought that the radical species not the stable species greatly influences the reducing ability, but a clear explanation of the reduction mechanism has not been made. For turbulent diffusion flame, it is difficult to measure the flame characteristics or do combustion numerical analysis. With current mathematical tools, it is almost impossible to do numerical analysis of combustion reaction with turbulent flow. Moreover, it is necessary to clarify not only the reaction in the flame but also the oxidation/reduction reaction of the steel and composition in the flame (especially, radical species) to elucidate the reduction mechanism. O n the other hand, in numerical analysis using equilibrium |
