高燐溶銑の脱燐処理に関するプロセスシミュレーシヨン

摘要

Owing to the increasing demand of steel in East Asia, it will become necessary to use low-grade iron ore in blast furnaces. The use of low-grade iron ore will increase the phosphorus content in hot metal. In India, iron ore containing 0.1% or more phosphorus has already been mined and used, and the phosphorus content in hot metal has been 0.25% or more. In this paper, the conditions for decreasing the phosphorus content in steel from hot metal with high phosphorus content are discussed on the basis of a simulation model developed by the ISIJ research group- "Process Simulation for Dephosphorization of Pig Iron by Multi-Phases." Using this simulation model, the optimum conditions for BOF decarburization treatment with or without a hot metal dephosphorization process were determined to decrease the phosphorus content in steel at the end point of BOF operation to 0.015% from 0.3% in the hot metal. The results showed that when the phosphorus content decreased to 0.015% by the hot metal dephosphorization treatment before BOF decarburization, it was possible to produce steel with only a 4 kg/t increase in lime consumption. On the other hand, steel production by the single slag operation of the BOF treatment was very difficult. In the case of the double slag operation, although steel production became possible, the unit consumption of lime increased to 20 kg/t or more. The obtained results established the high potential of the hot metal dephosphorization process for the treatment of hot metal with high phosphorus content.%1980年代に日本で開発された溶銑脱燐プロセスは，高炉で出銑された溶銑の総てを転炉精練の前に脱燐処理するという斬新な技術であり，低温処理による生石灰原単位の削減，レススラグ脱炭による鉄歩留ゃマンガン歩留まりの向上という経済的メリットで成り立つものであった。開発当初はトピードカー等の輸送容器を用いたインジェクション処理が主体であつたため，処理中の温度低下により製鋼工程でのスクラップ溶解量に制約が生じるという，熱的制約に関する問題があり，欧米を始めとする海外では，ほとんど採用されなかった。