Na_2O-CaO 系フラックスによる溶銑の脱硫速度

概要

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Study was made on the effect of Na_2O content and phosphorus content of hot metal on the desulfurization rate by Na_2O-CaO mixed flux at 1623K under argon gas atmosphere. In the case of high phosphorus content of hot metal, the optimum Na_2O content was observed. Na_2O may act not only as a desulfurization material but also as a oxidizer at slag-metal interface by decomposition reaction. The optimum Na_2O content appeared as a compromise between oxygen activity and sulfide capacity. Higher degree of desulfurization was obtained when hot metal of higher phosphorus content was treated. This result was ascribed to lowered oxygen activity at slag-metal interface caused by reduction of Na_2O activity and suppression of Na_2O decomposition by P_2O_5, formed by dephosphorization reaction. The highest degree of desulfurization could be achieved by Na_2O-SiO_2 flux, and this result support the mechanism described above. Through the experiment, large amount of unknown sulfur was observed and the rate of unknown sulfur increased with increase in Na_2O content in flux. To reveal this reaction mechanism, coupled reaction model calculation was performed. Although no evidence of gas formation at slag-metal interface could be obtained directly from this analysis, thermo-dynamic considerations suggested the possibility of SO_2 gas formation reaction in slag bulk phase.
社団法人日本鉄鋼協会の論文
1996-08-01