トピード•転炉型溶銑脱りん能力向上

摘要

In JFE Steel, hot metal dephosphorization treatment has been performed in torpedo car and converter to reduce slag generation and improve the quality of steel products. For the torpedo car treatment, a dephosphorization model was constructed based on the investigation of the reaction of iron oxide, which is the main component of the dephosphorization agent, in hot metal. In early stage of dephosphorization (i. e. higher phosphorus content region), the dephosphorization rate increased to 1.25 times by applying a method of lowering the slag basicity and tilting the torpedo car. In the later stage of dephosphorization (i.e. lower phosphorus content region), dephosphorization efficiency increased by 30 % higher oxygen supply rate conditions by applying a double lance injection method. In the converter, dephosphorization operation without using CaF_2 was achieved by increasing the hot metal temperature and promoting FeO generation in the early stage of blowing for slag fluxing. A new hot metal dephosphorization process with the converter was developed and is contributing to reduction of lime consumption and slag generation.%JFEスチールではトビード型(溶銑鍋型)，転炉型による溶銑脱りん処理を実施し，スラグ発生量低減，鋼材の品質向上を図っている。トビード型については，脱りん酸素源の酸化鉄の反応調査に基づき脱りん反応モデルを構築し，処理前半の高りん濃度域ではスラグの低塩基度化および傾転流滓，処理後半の低りん濃度域ではダブルランスを用いた酸素分散供給を行い，脱りん能力が1.25倍に増加した。転炉型については，溶銑温度の向上および吹鍊初期のFeO生成促進によるスラグ滓化等の対策により環境負荷の高いCaF_2を使用しない操業を実現した。さらに，吹鍊途中で中間排滓を行う新プロセス(Double-slag Refining Process, DRP~®)を開発し，石灰およびスラグ発生量の削減を図った。