マグネシウム蒸気吹込みによる溶鉄の脱酸におけるノズルの閉塞挙動

抄録

Deoxidation experiments of molten iron with injecting magnesium vapour produced in-situ by aluminothermic reduction of magnesia were carried out. MgO-Al pellets were charged in the immersion tube, which was put into the molten iron. Several injection holes or thin injection tubes were installed at the bottom and the side of the immersion tube, which was called as the injection nozzle. The injection nozzle was often clogged during the deoxidation experiments.
Effects of material, shape and number of gas exits of the nozzle, pellet composition and initial oxygen concentration on the nozzle clogging were investigated. The nozzle clogging took place earlier with increasing initial oxygen concentration in the molten iron. The Al₂O₃, MgO and mullite injection tubes were clogged more easily than the ZrO₂ injection tube. The main reason of the nozzle clogging was deposition of the deoxidation product on the inner wall of injection holes and tubes. It was also found that the aluminum suboxide gas was formed during the aluminothermic reduction of MgO. The suboxide gas formation can be suppressed by adding excess MgO to the MgO-Al pellet of molar ratio of 3 : 2.
Countermeasures to prevent the nozzle clogging have been proposed in this study. Decreasing the partial pressure of magnesium vapour in the injection gas, increasing the gas velocity through the nozzle and suppression of the aluminum suboxide gas formation are effective for preventing the nozzle clogging. Countermeasures can also be achieved by dividing pellet charging to the nozzle into several portions.