A side-blown submerged injection with a downward entry tuyere angle was conducted in a 5t pilot plant scale : where both of oxygen gas and CaO-based powders containing iron oxides were injected in order to control the temperature during the dephosphorization. Ceramic tuyeres were used for their good wear resistance against iron oxides. The results obtained are as follows : (1) Simultaneous removals of silicon and phosphorous were obtained effectively. And the final phosphorous content less than 0.010 percent was gained even with the initial silicon content of as high as 0.50 percent. (2) When the gaseous oxygen ratio to the total oxygen consumption was varied from 30 to 70 percent, the changes in bath temperature were range from - 120 to + 50°C, respectively. (3) The analysis of the mushroom showed that the dephosphorization reaction was proceeded just near by the tuyere tip.
