REFINING METHOD OF MOLTEN IRON

• Main Authors: MOMOSAKI KAZUHITO, OGASAWARA YASUSHI, ITO TOMOHIKO, OKUYAMA GORO, MIKI YUJI, KOBAYASHI NAOTO
• Format: Patent
• Language: English; Japanese
• Published: 03.03.2016
• Subjects: BLASTING; CHEMISTRY; DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS,IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KINDOF FURNACE; FURNACES; HEATING; KILNS; LIGHTING; MEASURING; MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUIDLEVEL; MECHANICAL ENGINEERING; METALLURGY; METALLURGY OF IRON; METERING BY VOLUME; OVENS; PHYSICS; PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OFWROUGHT-IRON OR STEEL; RETORTS; TESTING; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS; WEAPONS

PROBLEM TO BE SOLVED: To satisfy both of quick discharge of slag in a slug-off step and a secondary blowing step sufficient in cost aspect and quality aspect in a refining method of molten iron where the molten iron is continuously subjected to a primary blowing step and a secondary blowing step with the slug-off step interposed therebetween by using one converter type refining furnace.SOLUTION: A refining method of molten iron includes: a primary blowing step of supplying a gaseous oxygen source from a top-blowing lance 2 to molten iron 5 in a converter type refining furnace 1 and applying oxidation refining to the molten iron 5; a slug-off step of discharging a part of slag produced in the primary blowing step; and, subsequently, a secondary blowing step of adding CaO-based flux thereto, supplying the gaseous oxygen source thereto and applying the oxidation refining to the molten iron 5 remaining behind. A slag height in the converter type refining furnace 1 is measured during the primary blowing step, blowing is performed until a ratio of the slag height to an in-furnace free board height is equal to 0.6 or more, inputting slag-foaming depressant into the converter type refining furnace 1 and the blowing is continued when the ratio of the slag height thereto is equal to 0.6 or more and less than 0.8, and the primary blowing step is completed in a state of the ratio of the slag height thereto being equal to 0.5 or more and equal to 0.7 or less.SELECTED DRAWING: Figure 2 【課題】 １つの転炉型精錬炉を用いて溶銑の一次吹錬工程と二次吹錬工程とを、途中の排滓工程を挟んで連続して行う溶銑の精錬方法において、排滓工程におけるスラグの迅速な排出と、コスト面及び品質面で十分な二次吹錬工程とを両立させる。【解決手段】 転炉型精錬炉１内の溶銑５に上吹きランス２から気体酸素源を供給して溶銑に酸化精錬を施す一次吹錬工程と、一次吹錬工程で生成したスラグの一部を排出する排滓工程と、その後、ＣａＯ系媒溶剤を添加し、気体酸素源を供給して残留させた溶銑に酸化精錬を施す二次吹錬工程と、を有する精錬方法であって、一次吹錬工程中に炉内のスラグ高さを測定し、炉内フリーボードの高さに対するスラグ高さの比率が０．６以上となるまで吹錬を行い、スラグ高さ比率が０．６以上０．８未満のときにスラグのフォーミング鎮静材を炉内に投入して吹錬を継続し、スラグ高さ比率が０．５以上０．７以下となっている状態で一次吹錬工程を終了する。【選択図】 図２