JP4369632B2

JP4369632B2 - Pretreatment method of hot metal with low slag generation using converter type vessel

Info

Publication number: JP4369632B2
Application number: JP2001058001A
Authority: JP
Inventors: 健一郎宮本
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2001-03-02
Filing date: 2001-03-02
Publication date: 2009-11-25
Anticipated expiration: 2021-03-02
Also published as: JP2002256325A

Description

【０００１】
【発明の属する技術分野】
本発明は、転炉等の精錬炉を用いて、前回の溶銑の脱Ｓｉ（珪素）処理及び脱Ｐ（燐）処理を行った際に発生したスラグの一部を利用して、新しい溶銑の脱Ｓｉ処理、脱Ｐ処理を行う転炉型容器を用いたスラグ発生量の少ない溶銑の予備処理方法に関する。
【０００２】
【従来の技術】
従来、製鋼の主原料である溶銑は、Ｓｉ（珪素）やＳ（硫黄）、Ｐ（燐）等の不純物を含んでおり、予めこれ等の不純物を除去する脱Ｓｉ、脱Ｓ、脱Ｐ等のいわゆる溶銑の予備処理が行われている。
特に、脱Ｓｉ処理及び脱Ｐ処理を同時に行う場合は、溶銑に生石灰、ソーダ灰等の脱燐用のフラックスとＰを酸化する気体酸素、あるいは酸化鉄や集塵ダスト、スラジ等の固体酸化剤を添加するか、又はフラックスや固体酸化剤の吹き込み（インゼクション）を行うことにより、溶銑中のＳｉを優先的にＳｉＯ₂にして除去し、同時に、Ｐを酸化物（Ｐ₂Ｏ₅）にし、生成したスラグ中のＣａＯに捕捉させて溶銑中から除去する。
しかし、これ等溶銑の予備処理では、Ｓｉは容易にＳｉＯ₂として除去できるが、脱Ｐの反応効率が悪く、到達Ｐ濃度を十分に低下することが困難である。
この対策として、特開昭６２−１０９９１０号公報に記載されているように、ＣａＯを主成分とした滓化促進剤を配合したフラックスを溶銑の表面に載置し、ランスから酸素を上吹きしながら、鉄鉱石やスケール等の固体酸素剤の粉末を溶銑内にインゼクションする方法が行われている。
更に、特開平６−２８７６１６号公報に記載されているように、酸化鉄６０〜８０質量％を含んだＣａＯ−Ｆｅ₂Ｏ₃−ＣａＦ₂系のフラックスに、Ｎａ₂Ｏ₃を３〜１０質量％を配合したものを、溶銑内にインゼクションし、上方からランスを用いて溶銑の表面に酸素を吹き付けて脱Ｓｉ処理及び脱Ｐ処理を同時に行う方法が提案されており、脱Ｐ効率の向上と到達Ｐ濃度の低減を図っている。
【０００３】
【発明が解決しようとする課題】
しかしながら、特開昭６２−１０９９１０号公報に記載された方法では、初期の溶銑の脱Ｓｉ、脱Ｐ効率を高めることができるが、脱Ｐ処理の初期から末期の間を同一の処理条件で行っており、スラグ等への燐の平衡論的な物質移動を考慮していないため、脱Ｐ処理の中期から末期である脱Ｐ後期における脱Ｐ効率が低下して到達Ｐ濃度が高くなる。
この到達Ｐ濃度を低くするには、脱Ｓｉ処理及び脱Ｐ処理に使用する生石灰や酸化鉄、ミルスケール、酸素等の使用量が増加して処理コストが上昇する。
更に、常に、新しい生石灰、酸化鉄等を使用したり、吹き込むフラックスの使用量が多くなることにより、脱Ｓｉ、脱Ｐ処理の際に生成するスラグ量が増加し、このスラグの処理に多大の費用を要する。
また、特開平６−２８７６１６号公報に記載された方法では、常に、新しい生石灰、酸化鉄等を使用し、ＣａＦ₂やＮａ₂Ｏ₃等の高価な原料を使用する必要があり、生成スラグ量が増加する。しかも、生成したスラグには、強アルカリ成分やフッ素等が含まれるため、生成したスラグは、廃棄する際に環境上での制約を受ける。
更に、特開昭６２−１０９９１０号公報に記載された方法と同様に、脱Ｐ処理の初期から末期の間を同一の処理条件で行い、スラグ等への燐の平衡論的な物質移動を考慮していないため、脱Ｐ処理の脱Ｐ後期における脱Ｐ効率が低下し、脱Ｓｉ、脱Ｐの予備処理に用いるフラックスの使用量が増加し、生成するスラグ量が増加し、このスラグの処理に多大の費用を要する等の問題がある。
【０００４】
本発明はかかる事情に鑑みてなされたもので、転炉型容器を用い、脱Ｓｉ、脱Ｐの予備処理に用いるフラックスの使用量や発生スラグ量を減少させ、脱Ｓｉ、脱Ｐ反応の反応効率を高めて到達Ｓｉ、到達Ｐ濃度を低減することができる転炉型容器を用いたスラグ発生量の少ない溶銑の予備処理方法を提供することを目的とする。
【０００５】
【課題を解決するための手段】
前記目的に沿う本発明に係る転炉型容器を用いたスラグ発生量の少ない溶銑の予備処理方法は、転炉型容器を用いて、脱Ｓｉ処理及び脱Ｐ処理を行うスラグ発生量の少ない溶銑の予備処理方法において、前回の溶銑の予備処理で発生したスラグの４０〜６０質量％を前記転炉型容器内に残留させておき、該転炉型容器内にＳｉ濃度が０．１〜０．６質量％である新しい溶銑を装入し、そして吹酸し該溶銑の脱Ｓｉ処理及び脱Ｐ処理を行い、この脱Ｓｉ処理及び脱Ｐ処理の途中であって前記吹酸の全経過時間の５０〜７０％にあたる時期に、該溶銑にＣａＯを添加して、更に、前記脱Ｓｉ処理及び脱Ｐ処理を継続して行う。
この方法により、酸素供給律則の領域である溶銑のＳｉ及びＰ濃度が高い領域で、前回の溶銑の予備処理で発生したスラグの一部を、新しく装入した溶銑の予備処理に用い、更に吹酸することによって、この新しい溶銑中のＳｉ及びＰを酸化してスラグ中に吸収させることができ、しかも、後で添加するＣａＯの滓化を促進させることができる。
更に、転炉型容器内に装入した新しい溶銑中のＳｉ及びＰ濃度が低くなる時点で、ＣａＯを添加して、早期にＣａＯを滓化して生成させたスラグのＳｉＯ₂やＰ₂Ｏ₅の吸収能を高め、脱Ｓｉ反応は勿論、特に、脱Ｐ反応を促進することができ、到達Ｐ濃度を低減することができる。
前回の溶銑の予備処理で発生したスラグ量の４０質量％未満を残留させた場合、スラグ量が少なくなり過ぎて、ＳｉＯ₂やＰ₂Ｏ₅のスラグの吸収能が低下し、後に添加するＣａＯが増加して予備処理コストが高くなる。一方、６０質量％を超えて残留させると、ある程度ＳｉＯ₂やＰ₂Ｏ₅を吸収したスラグ量が増加するため、新しいＣａＯが、ＳｉＯ₂やＰ₂Ｏ₅を吸収したスラグに希釈され、全体としての脱Ｓｉ及び脱Ｐ効率が低下する。更に、到達Ｐ濃度を低くするためには、ＣａＯの使用量を増す必要があり、発生するスラグ量が増加し、スラグの処理コストが上昇する。
【０００６】
また、前記転炉型容器内に装入する前記新しい溶銑のＳｉ濃度を０．１〜０．６質量％とすることにより、新しい溶銑中のＳｉを酸化させてＳｉＯ₂を生成させ、スラグ中に吸収させ、しかも、スラグ塩基度の低下を抑制して脱Ｐ反応を促進することができる。なお、新しい溶銑のＳｉ濃度が０．１質量％未満になると、生成したスラグの塩基度が高くなって生成したスラグの滓化が悪くなり、脱Ｐ反応が低下する。一方、Ｓｉ濃度が０．６質量％を超えると、生成したスラグの塩基度が低くなり過ぎて後期でのＰ₂Ｏ₅の吸収が悪くなり、到達Ｐ濃度が高くなる。
【０００７】
更に、前記ＣａＯの添加を、前記吹酸の全経過時間の５０〜７０％にあたる時期に行うことにより、添加したＣａＯの滓化を良好にし、しかも、スラグ中のＦｅＯ濃度の低下を抑制し、生成したスラグのＳｉＯ₂やＰ₂Ｏ₅の吸収能を安定して高めることができるため、脱Ｓｉ及び脱Ｐ反応を促進させることができる。
ＣａＯを添加する時期が吹酸の全経過時間の５０％未満では、吹酸の初期（ＣａＯの添加時）に発生するスラグの量が増大し、スラグ中のＦｅＯ濃度が低下するため、脱Ｓｉ及び脱Ｐ効率が低下する。一方、ＣａＯの添加時期が吹酸の全経過時間の７０％を超えると、ＣａＯの予備処理の内でのＣａＯの滓化が悪くなり、脱Ｐ効率が低下して到達Ｐ濃度が高くなる。
【０００８】
【発明の実施の形態】
続いて、添付した図面を参照しつつ、本発明を具体化した実施の形態につき説明し、本発明の理解に供する。
図１は本発明の一実施の形態に係る転炉型容器を用いたスラグ発生量の少ない溶銑の予備処理方法に適用される上底吹き転炉の全体図である。
図１に示すように、本発明の一実施の形態に係る転炉型容器を用いたスラグ発生量の少ない溶銑の予備処理方法に用いられる転炉型容器の一例である上底吹き転炉１０は、炉体１１の底部に底吹きノズル１２を設け、上方から炉体１１内に挿入される上吹きランス１３を有し、脱Ｓｉ（脱珪）、脱Ｐ（脱燐）用のフラックスの一例である生石灰（ＣａＯ）１５を貯留する貯蔵ホッパ１４と、これ等貯蔵ホッパ１４から切り出された生石灰１５を炉体１１内の溶銑１６の上部に形成されたスラグ１７に添加するシュート１８と、炉体１１の側部に設けた出鋼口１９を備えている。
【０００９】
次に、本発明の一実施の形態に係る転炉型容器を用いたスラグ発生量の少ない溶銑の予備処理方法について前記した上底吹き転炉１０を用いて説明する。
まず、上底吹き転炉１０に、Ｓｉ（珪素）濃度が０．１〜０．６質量％、Ｐ（燐）濃度が０．０９０〜０．１３０質量％の脱Ｓｉ及び脱Ｐ処理を行っていない溶銑を１７０トン装入し、生石灰１５を貯蔵ホッパ１４から切り出しシュート１８を介して炉体１１内に添加し、上吹きランス１３を下降させて、炉体１１内に挿入して吹酸を行って、ＳｉやＰを酸化させ、生成させたＳｉＯ₂やＰ₂Ｏ₅をスラグ中に吸収させて、溶銑の予備処理である脱Ｓｉ及び脱Ｐ処理を行い、溶銑中のＳｉ濃度を０．０１質量％、到達Ｐ濃度を０．０１０質量％にすることで、予備処理後に５トンのスラグを生成させた。
予備処理が終了した溶銑は、出鋼口１９から図示しない別の容器に出銑され、この予備処理で発生したスラグの４０〜６０質量％を上底吹き転炉１０の炉体１１内に残留させた。
【００１０】
本実施の形態では、前述した溶銑、すなわち前回の溶銑（前チャージの溶銑）の予備処理で生成したスラグの４０〜６０質量％を炉体１１内に残留させた状態で、上底吹き転炉１０の炉体１１内に、Ｓｉ（珪素）濃度が０．１〜０．６質量％、Ｐ（燐）濃度が０．０９０〜０．１３０質量％の新しい（脱Ｓｉ及び脱Ｐ処理を行っていない）溶銑１６を１７０トン装入する。
そして、上吹きランス１３を下降させ、その先端が炉体１１内の溶銑１６の表面から１８００ｍｍ上方の位置になるように挿入して、吹酸（気体酸素の吹き付け）を行った。
更に、底吹きノズル１２から溶銑の攪拌用のアルゴンガス、窒素ガス等の攪拌ガスを吹き込みながら新しい溶銑１６の脱Ｓｉ及び脱Ｐ処理の予備処理を行った。脱Ｓｉ処理、脱Ｐ前半の処理では、吹酸によって、溶銑１６中のＳｉの殆どが酸化され、ＳｉＯ₂になってスラグ１７中に吸収され、脱Ｓｉ反応が完了する。
このとき、脱Ｓｉ反応が進行するにつれて、吹酸されたＯによって溶銑１６中のＰも酸化されてＰ₂Ｏ₅になり、スラグ１７中に吸収され、脱Ｐ反応が行われる。
しかし、予備処理時の吹酸の全経過時間（吹酸の開始から吹酸の終了までの吹酸を行う時間）の５０％近傍になると、スラグ１７中のＰ₂Ｏ₅の吸収能が低下し、脱Ｐ反応は、スラグ１７にＰが吸収されにくい、即ちＰの供給律則の領域に入るため、脱Ｐ効率が低下し始める。
従って、脱Ｓｉ処理及び脱Ｐ処理の途中、即ち吹酸の全経過時間の５０〜７０％にあたる時期、つまりその時間内に、生石灰１５を貯蔵ホッパ１４から切り出し、シュート１８を介して炉体１１内の溶銑１６に添加して、更に、脱Ｓｉ処理及び脱Ｐ処理を継続して行う。
【００１１】
この生石灰１５は、脱Ｓｉ及び脱Ｐ処理の初期に一括添加すると、スラグ中のＦｅＯ濃度が上がらず、脱Ｐ処理の中間で多量に添加すると、添加直後にＦｅＯ濃度が低下したり、スラグの滓化不良を招くため、均等に分割して添加するか、あるいは少量ずつ連続して添加を行う必要がある。
添加した生石灰１５は、溶融したスラグ１７に容易に混合され、固体である生石灰１５と溶融体であるスラグ１７の接触によって速やかに溶解し、スラグ１７のＰ₂Ｏ₅の吸収能を高めることができる。
その結果、脱Ｐ反応の進行し難いＰの供給律則の領域であっても、Ｐの酸化とこの酸化により生成したＰ₂Ｏ₅のスラグ１７への吸収による脱Ｐ反応を促進することができ、この脱Ｐ反応を、到達Ｐ濃度が０．０２〜０．０３質量％の範囲になるまで行う。
また、この脱Ｓｉ、脱Ｐ処理は、前チャージの溶銑の予備処理を行った際に生成したスラグの４０〜６０質量％を再利用しているので、溶銑の予備処理で発生する廃棄スラグの量を減少させることができ、生石灰の使用量や廃棄スラグの処理コスト等を低減することができる。しかも、スラグ１７中にＮａやフッ素等の強アルカリ成分や特定の成分を含まないので、廃棄する際の環境上の制約を無くすことができる。
このように、前回の溶銑の予備処理を行った後のスラグの４０〜６０質量％を、常に上底吹き転炉１０の炉体１１内に残留させ、新しい溶銑１６を炉体１１内に装入して、吹酸による脱Ｓｉ、脱Ｐ処理を行い、しかも、脱Ｓｉ処理及び脱Ｐ処理の途中でＣａＯを添加する予備処理を繰返し行う。
脱Ｓｉ処理及び脱Ｐ処理が行われた溶銑１６は、出鋼口１９から出銑され、脱炭精錬炉である上吹き転炉、上底吹き転炉、電気炉等に装入されて、吹酸による脱炭精錬が行われ、これにより、溶鋼が製造される。
【００１２】
【実施例】
次に、本発明に係る転炉型容器を用いたスラグ発生量の少ない溶銑の予備処理方法の実施例について説明する。
初めに、珪素（Ｓｉ）濃度が０．３質量％、燐濃度が０．１００質量％の前チャージの溶銑１５０トンを上底吹き転炉１０に装入し、ＣａＯの添加と吹酸を行って脱Ｓｉ処理及び脱Ｐ処理を行い、炉体１１内に前チャージの予備処理で生成したスラグの一部を残留させ、そのスラグの残留量、燐濃度が０．１００質量％の新しい溶銑、即ち次チャージの溶銑の珪素（Ｓｉ）濃度、吹酸の途中でのＣａＯの投入タイミングを変化させて、脱Ｓｉ及び脱Ｐの予備処理を行った。
なお、炉体１１内には、新しい次チャージの溶銑１５０トンを装入した。
そして、次チャージの溶銑の予備処理後の到達Ｐ濃度（到達Ｐ質量％）と、生石灰と酸化鉄を添加して行う従来の予備処理のスラグ発生量を指数１とした場合の発生スラグ量指数、及び総合評価をそれぞれ調査した。その結果を表１に示す。
【００１３】
実施例１及び実施例２は、前チャージの残留スラグの５０質量％、４３質量％をそれぞれ使用し、溶銑の装入時のＳｉ濃度を０．３５質量％、０．４２質量％、追加ＣａＯの投入タイミングを吹酸の全経過時間の５５％、６３％にした場合であり、それぞれ到達Ｐ濃度を０．０１３質量％、０．０１１質量％、発生スラグ量指数を０．４５、０．５１にでき、総合評価として良い（○）結果が得られた。
実施例３は、前チャージの残留スラグの下限である４０質量％、実施例４は、前チャージの残留スラグの上限である６０質量％をそれぞれ使用した場合であり、それぞれ到達Ｐ濃度を０．０１２質量％、０．０１５質量％、発生スラグ量指数を０．５４、０．４１にでき、総合評価として良い（○）結果が得られた。
実施例５は、次チャージのＳｉ濃度を０．１０質量％、実施例６は、Ｓｉ濃度を０．６０質量％とした場合であり、それぞれ到達Ｐ濃度を０．０１２質量％、０．０１４質量％、発生スラグ量指数を０．４７、０．４８にでき、総合評価として良い（○）結果が得られた。
実施例７は、追加ＣａＯ投入タイミングを下限である５０％、実施例８は、追加ＣａＯ投入タイミングを上限である７０％にした場合であり、それぞれ到達Ｐ濃度を０．０１１質量％、０．０１４質量％、発生スラグ量指数を０．５１、０．４６にでき、総合評価として良い（○）結果が得られた。
【００１４】
【表１】

【００１５】
これに対し、比較例１は、前チャージの残留スラグの使用量を３３質量％と低くした場合であり、十分な脱Ｐを行うために必要なスラグ量が不足し、予備処理終了時の到達Ｐ濃度が０．０３４質量％と高くなって、脱炭精錬工程での負荷が増加し、総合評価として悪い（×）結果になった。
比較例２は、前チャージの残留スラグスラグの使用量を６７質量％と多くした場合であり、脱Ｐは十分に行なえるが、発生スラグ量指数が０．８２と高くなり、廃棄処理コスト等の増加を招くため、総合評価としてやや悪い（△）結果になった。
比較例３は、次チャージのＳｉ濃度を０．０５質量％と低くした場合であり、予備処理時のスラグの塩基度が高くなり、スラグの滓化が悪く、脱Ｐ効率が低下し、到達Ｐ濃度が０．０３７と高くなって、脱炭精錬工程での負荷が増加し、総合評価として悪い（×）結果になった。
比較例４は、次チャージのＳｉ濃度を０．６７質量％と高くした場合であり、ＳｉＯ₂の生成に起因してスラグの発生量が増加し、発生スラグ量指数が０．８５とやや悪く、更に、スラグの塩基度の低下によって脱Ｐ効率が低下し、到達Ｐ濃度が０．０３２質量％と高くなり、総合評価として悪い（×）結果になった。
比較例５は、追加ＣａＯの投入タイミングを３６％としたため、投入時期が早過ぎた場合であり、予備処理の開始の初期のスラグ量が増加し、このスラグ量の増加にともなってスラグ中のＦｅＯ濃度が低下し、予備処理の全体を通した脱Ｐ効率が低下して到達Ｐ濃度が０．０３５質量％と高くなり、総合評価として悪い（×）結果になった。
比較例６は、追加ＣａＯの投入タイミングが７８％となり、投入時期が遅過ぎた場合であり、予備処理の末期のスラグの滓化不良を招き、予備処理の全体を通した脱Ｐ効率が低下して到達Ｐ濃度が０．０３９質量％と高くなり、総合評価として悪い（×）結果になった。
なお、従来法は、炉内に装入した溶銑に、常に、新しい生石灰と酸化鉄を添加して吹酸を行う溶銑の脱Ｓｉ及び脱Ｐ処理を行った場合であり、予備処理の全体を通して生石灰及び酸化鉄の添加量が増加し、発生スラグ量指数が１．０と高くなり、廃棄処理コスト等の増加を招くため、総合評価として悪い（×）結果になった。
【００１６】
以上、本発明の実施の形態を説明したが、本発明は、上記した形態に限定されるものでなく、要旨を逸脱しない条件の変更等は全て本発明の適用範囲である。
例えば、溶銑中のＳｉ、Ｐの酸化を行う場合、吹酸による方法の他に、スラジ、集塵ダスト、鉄鉱石、スケール等の固体酸素剤を吹酸と併用することができる。
【００１７】
【発明の効果】
請求項１記載の転炉型容器を用いたスラグ発生量の少ない溶銑の予備処理方法においては、前回の溶銑の予備処理で発生したスラグの４０〜６０質量％を転炉型容器内に残留させておき、転炉型容器内に新しい溶銑を装入し、そして吹酸し溶銑の脱Ｓｉ処理及び脱Ｐ処理を行い、この脱Ｓｉ処理及び脱Ｐ処理の途中で、溶銑にＣａＯを添加して、更に、脱Ｓｉ処理及び脱Ｐ処理を継続して行うので、脱Ｓｉ、脱Ｐ予備処理に用いるＣａＯを節減することができ、脱Ｓｉ及び脱Ｐの効率を高めて、到達Ｓｉ、到達Ｐ濃度を低減することができ、廃棄スラグの処理コストを低減することができる。
【００１８】
また、転炉型容器内に装入する新しい溶銑のＳｉ濃度を０．１〜０．６質量％にしているので、スラグ量の過剰な増加やスラグの塩基度の低下を抑制して脱Ｓｉ、脱Ｐ効率を安定して高め、到達Ｓｉ、到達Ｐ濃度をより低くすることができ、後工程の脱炭精錬の負荷を軽減することができる。
【００１９】
更に、ＣａＯの添加を、吹酸の全経過時間の５０〜７０％にあたる時期に行うので、スラグの滓化を良好にして少ないスラグ量で脱Ｓｉ、脱Ｐ効率を安定して高めることができ、発生したスラグのアルカリ成分等の有害成分を抑制して再利用を行うことができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態に係る転炉型容器を用いたスラグ発生量の少ない溶銑の予備処理方法に適用される上底吹き転炉の全体図である。
【符号の説明】
１０：上底吹き転炉（転炉型容器）、１１：炉体、１２：底吹きノズル、１３：上吹きランス、１４：貯蔵ホッパ、１５：生石灰（フラックス）、１６：溶銑、１７：スラグ、１８：シュート、１９：出鋼口[0001]
BACKGROUND OF THE INVENTION
The present invention uses a part of the slag generated when the previous hot metal de-Si (silicon) treatment and de-P (phosphorus) treatment were performed using a refining furnace such as a converter, The present invention relates to a hot metal pretreatment method using a converter type vessel that performs de-Si treatment and de-P treatment with a small amount of slag generation.
[0002]
[Prior art]
Conventionally, hot metal, which is the main raw material for steelmaking, contains impurities such as Si (silicon), S (sulfur), and P (phosphorus), and removes such impurities in advance, such as Si removal, S removal, and P removal. The so-called hot metal pretreatment is performed.
In particular, when performing the Si removal treatment and the P removal treatment at the same time, a flux for dephosphorization such as quick lime and soda ash in the molten iron and gaseous oxygen that oxidizes P, or a solid oxidizer such as iron oxide, dust collection dust, sludge, etc. Or by blowing a flux or a solid oxidant (injection) to remove Si in the molten iron preferentially as SiO ₂ , and simultaneously convert P into an oxide (P ₂ O ₅ ), It is captured by CaO in the generated slag and removed from the hot metal.
However, in these hot metal pretreatments, Si can be easily removed as SiO ₂ , but the reaction efficiency of de-P is poor and it is difficult to sufficiently reduce the ultimate P concentration.
As a countermeasure, as described in JP-A-62-109910, a flux containing a hatching accelerator mainly composed of CaO is placed on the surface of the hot metal, and oxygen is blown up from the lance. However, a method of injecting a powder of solid oxygen agent such as iron ore or scale into hot metal has been performed.
Further, as described in JP-A-6-287616, ₃ to 10 mass of Na ₂ O ₃ is added to a CaO—Fe ₂ O ₃ —CaF ₂ -based flux containing 60 to 80 mass% of iron oxide. A method of simultaneously performing de-Si treatment and de-P treatment by injecting into the hot metal with oxygen and spraying oxygen onto the hot metal surface from above using a lance has been proposed. The ultimate P concentration is reduced.
[0003]
[Problems to be solved by the invention]
However, in the method described in Japanese Patent Laid-Open No. 62-109910, it is possible to increase the initial Si removal and P removal efficiency of the hot metal, but the initial and final stages of the deP treatment are performed under the same treatment conditions. Since the equilibrium mass transfer of phosphorus to slag or the like is not taken into consideration, the de-P efficiency from the middle stage to the late stage of the de-P treatment is lowered and the ultimate P concentration is increased.
In order to lower this ultimate P concentration, the amount of quick lime, iron oxide, mill scale, oxygen, etc. used for the de-Si treatment and the de-P treatment is increased and the treatment cost is increased.
Furthermore, always using new quicklime, iron oxide, etc., or increasing the amount of flux to be blown in, the amount of slag generated during de-Si and de-P treatment increases, and this slag is treated with a great deal. It costs money.
Further, in the method described in JP-A-6-287616, it is necessary to always use new quicklime, iron oxide, etc., and to use expensive raw materials such as CaF ₂ and Na ₂ O _3, and the amount of generated slag Will increase. In addition, since the generated slag contains a strong alkali component, fluorine, and the like, the generated slag is subject to environmental restrictions when discarded.
Further, similarly to the method described in Japanese Patent Application Laid-Open No. 62-109910, the initial P to P end of the de-P treatment is performed under the same treatment conditions, and the mass transfer of phosphorus to slag and the like is considered. As a result, the de-P efficiency in the late phase of de-P treatment is reduced, the amount of flux used for the pre-treatment of de-Si and de-P is increased, the amount of slag produced is increased, and this slag treatment However, there is a problem that a large amount of money is required.
[0004]
The present invention has been made in view of such circumstances, using a converter-type vessel, reducing the amount of flux used and the amount of generated slag used for pretreatment of de-Si and de-P, and the reaction of de-Si and de-P reaction. It is an object of the present invention to provide a hot metal pretreatment method using a converter type vessel that can increase the efficiency and reduce the reached Si and the reached P concentration with a small amount of slag generation.
[0005]
[Means for Solving the Problems]
The hot metal pretreatment method with a small amount of slag generation using the converter type container according to the present invention in accordance with the above object is a hot metal with a small amount of slag generation using the converter type container to perform de-Si treatment and de-P treatment. In the pretreatment method, 40-60 mass% of the slag generated in the previous hot metal pretreatment is left in the converter type vessel, and the Si concentration is 0.1-0 in the converter type vessel. The hot metal of 6 mass% was charged and blown, and the hot metal was subjected to de-Si treatment and de-P treatment, and during the de-Si treatment and de-P treatment, the total elapsed time of the blown acid Then , CaO is added to the molten iron at a time corresponding to 50 to 70% of the above, and the de-Si treatment and the de-P treatment are continued.
By this method, a part of the slag generated in the previous hot metal pretreatment in the hot metal Si and P concentration region, which is the oxygen supply rule region, is used for the pretreatment of the newly charged hot metal, and By blowing acid, Si and P in the new hot metal can be oxidized and absorbed in the slag, and further, the hatching of CaO added later can be promoted.
Furthermore, when the Si and P concentrations in the new hot metal charged in the converter-type vessel are lowered, CaO is added, and the slag SiO ₂ and P ₂ O ₅ produced by the early hatching of CaO are generated. In addition to the de-Si reaction, in particular, the de-P reaction can be promoted and the ultimate P concentration can be reduced.
If allowed to remain less than 40% by weight of the amount of slag generated in pre-processing of the previous hot metal, CaO amount slag becomes too small, the absorption capacity of the slag of SiO ₂ and P ₂ O ₅ is reduced, added after Increases the pretreatment cost. On the other hand, if the amount exceeds 60 % by mass , the amount of slag that has absorbed SiO ₂ and P ₂ O ₅ increases to some extent, so new CaO is diluted into slag that has absorbed SiO ₂ and P ₂ O ₅ , As a result, the Si removal and P removal efficiency decreases. Furthermore, in order to lower the reached P concentration, it is necessary to increase the amount of CaO used, the amount of slag generated increases, and the slag processing cost increases.
[0006]
Further, by the Si concentration of the new hot metal charged and 0.1-0.6 mass% before Kiten furnace type vessel, to oxidize the Si in new hot metal by generating a SiO _2, slag In addition, the de-P reaction can be promoted by suppressing the decrease in slag basicity. In addition, when the Si concentration of new hot metal becomes less than 0.1 mass% , the basicity of the produced | generated slag will become high, and the hatching of produced | generated slag will worsen, and de-P reaction will fall. On the other hand, when the Si concentration exceeds 0.6 % by mass, the basicity of the generated slag becomes too low, and the absorption of P ₂ O _{5 in} the later stage is deteriorated, and the ultimate P concentration is increased.
[0007]
Furthermore, the addition of the CaO, the row Ukoto the time corresponding to 50% to 70% of the total elapsed time of the吹酸, the good slag formation of added CaO, moreover, to suppress a reduction in FeO concentration in slag Since the generated slag can stably enhance the absorption capacity of SiO ₂ and P ₂ O ₅ , the de-Si and de-P reactions can be promoted.
When the CaO addition time is less than 50% of the total elapsed time of the blowing acid, the amount of slag generated at the initial stage of the blowing acid (at the time of addition of CaO ) increases, and the FeO concentration in the slag decreases. And de-P efficiency decreases. On the other hand, when the addition timing of CaO exceeds 70% of the total elapsed time吹酸, slag formation of CaO in the among the pretreatment CaO is deteriorated, reaching P concentration increases de P efficiency is lowered.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
FIG. 1 is an overall view of an upper-bottom blown converter applied to a hot metal pretreatment method using a converter-type vessel according to an embodiment of the present invention and having a small amount of slag generation.
As shown in FIG. 1, an upper bottom blown converter 10, which is an example of a converter type vessel used in a hot metal pretreatment method using a converter type vessel according to an embodiment of the present invention, with a small amount of slag generation. Is provided with a bottom blowing nozzle 12 at the bottom of the furnace body 11 and has an upper blowing lance 13 inserted into the furnace body 11 from above, and a flux for de-Si (desiliconization) and de-P (dephosphorization) fluxes. A storage hopper 14 for storing quick lime (CaO) 15 as an example, a chute 18 for adding quick lime 15 cut out from these storage hoppers 14 to a slag 17 formed on the hot metal 16 in the furnace body 11, and A steel outlet 19 is provided on the side of the furnace body 11.
[0009]
Next, a hot metal pretreatment method with a small amount of slag generation using the converter type container according to the embodiment of the present invention will be described using the above-described top-bottom blowing converter 10.
First, the top bottom blowing converter 10 is subjected to Si removal and P removal treatment with a Si (silicon) concentration of 0.1 to 0.6 mass% and a P (phosphorus) concentration of 0.090 to 0.130 mass%. 170 tons of hot metal is charged, quick lime 15 is cut out from the storage hopper 14 and added to the furnace body 11 via the chute 18, and the upper blowing lance 13 is lowered and inserted into the furnace body 11 for blowing acid. To oxidize Si and P, absorb the generated SiO ₂ and P ₂ O ₅ in the slag, perform de-Si and de-P treatment as the hot metal pretreatment, and reduce the Si concentration in the hot metal By setting the reached P concentration to 0.01 % by mass and 0.010 % by mass , 5 tons of slag was generated after the preliminary treatment.
The hot metal that has been subjected to the preliminary treatment is discharged from the steel outlet 19 to another container (not shown), and 40 to 60 mass% of the slag generated in the preliminary treatment remains in the furnace body 11 of the top-bottom blowing converter 10. I let you.
[0010]
In the present embodiment, the above-mentioned hot metal, that is, 40 to 60 % by mass of the slag generated in the preliminary treatment of the previous hot metal (pre-charged hot metal) is left in the furnace body 11, and the top-bottom blowing converter 10 new furnace bodies 11 with Si (silicon) concentration of 0.1-0.6 mass% and P (phosphorus) concentration of 0.090-0.130 mass% (de-Si and de-P treatment were performed. Not charged) Charge hot metal 16 to 170 tons.
And the upper blowing lance 13 was lowered | hung, and it inserted so that the front-end | tip might be a position 1800 mm above from the surface of the hot metal 16 in the furnace body 11, and blowing acid (gas oxygen blowing) was performed.
Further, preliminary treatment for removing Si and removing P from the hot metal 16 was performed while blowing stirring gas such as argon gas and nitrogen gas for stirring the hot metal from the bottom blowing nozzle 12. In the de-Si treatment and the first half of the de-P treatment, most of the Si in the molten iron 16 is oxidized by blown acid, becomes SiO ₂ and is absorbed in the slag 17, and the de-Si reaction is completed.
At this time, as the de-Si reaction proceeds, P in the molten iron 16 is also oxidized by the blown acid O to become P ₂ O ₅ and absorbed in the slag 17 to perform the de-P reaction.
However, the absorption capacity of P ₂ O ₅ in the slag 17 decreases when the total elapsed time of the blowing acid during the pretreatment (the time for performing blowing acid from the start of blowing acid to the end of blowing acid) is close to 50%. In the de-P reaction, however, P is not easily absorbed by the slag 17, that is, it enters the region of P supply regulation, and therefore the de-P efficiency starts to decrease.
Accordingly, quick lime 15 is cut out from the storage hopper 14 during the de-Si treatment and the de-P treatment, that is, at a time corresponding to 50 to 70% of the total elapsed time of the blowing acid, that is, within that time, and the furnace body 11 through the chute 18. It is added to the inner hot metal 16 and further, the Si removal treatment and the P removal treatment are continued.
[0011]
If this quicklime 15 is added all at once in the initial stage of de-Si and de-P treatment, the FeO concentration in the slag will not increase, and if added in a large amount in the middle of the de-P treatment, the FeO concentration will decrease immediately after the addition, In order to cause a hatching defect, it is necessary to add in equal portions or to add continuously in small portions.
The added quicklime 15 is easily mixed with the molten slag 17 and quickly dissolved by the contact between the quicklime 15 that is a solid and the slag 17 that is a melt, thereby increasing the ability of the slag 17 to absorb P ₂ O _5. it can.
As a result, it is possible to promote the de-P reaction due to the oxidation of P and the absorption of P ₂ O ₅ produced by this oxidation into the slag 17 even in the region of P supply regulation where the de-P reaction is difficult to proceed. This de-P reaction is carried out until the ultimate P concentration is in the range of 0.02 to 0.03 % by mass .
In addition, since the de-Si and P removal treatments reuse 40-60 mass% of the slag generated when the pre-charge hot metal pre-treatment is performed, the waste slag generated in the hot-metal pre-treatment The amount can be reduced, and the amount of quicklime used, the processing cost of waste slag, and the like can be reduced. In addition, since the slag 17 does not contain a strong alkali component such as Na or fluorine or a specific component, it is possible to eliminate environmental restrictions at the time of disposal.
In this way, 40-60 mass% of the slag after the previous hot metal preliminary treatment is always left in the furnace body 11 of the top-bottom blowing converter 10, and new hot metal 16 is loaded in the furnace body 11. Then, de-Si and de-P treatments with blowing acid are performed, and a preliminary treatment of adding CaO is repeated during de-Si and de-P treatments.
The hot metal 16 that has been subjected to the de-Si treatment and the de-P treatment is fed from the steel outlet 19 and charged into a decarburizing and refining furnace such as an upper blowing converter, an upper bottom blowing converter, an electric furnace, Decarburization refining with blown acid is performed, thereby producing molten steel.
[0012]
【Example】
Next, an embodiment of a hot metal pretreatment method using the converter type container according to the present invention with a small amount of slag generation will be described.
First, 150 tons of pre-charged hot metal having a silicon (Si) concentration of 0.3 % by mass and a phosphorus concentration of 0.100 % by mass was charged into the top-bottom blowing converter 10, and CaO was added and blown acid was added. Then, Si removal treatment and P removal treatment are performed to leave a part of the slag generated in the pre-charging pretreatment in the furnace body 11, and the residual amount of the slag, new hot metal having a phosphorus concentration of 0.100 % by mass , That is, preliminary treatment for Si removal and P removal was performed by changing the silicon (Si) concentration in the hot metal of the next charge and the timing of introducing CaO in the middle of the blowing acid.
The furnace body 11 was charged with 150 tons of new next charge hot metal.
And the reached P concentration after the pretreatment of the hot metal of the next charge (reached P mass% ) and the generated slag amount index when the slag generation amount of the conventional pretreatment performed by adding quick lime and iron oxide is taken as the index 1 , And comprehensive evaluation were investigated respectively. The results are shown in Table 1.
[0013]
In Examples 1 and 2, 50 % by mass and 43 % by mass of the residual slag of the precharge were used, respectively, and the Si concentration at the time of charging the hot metal was 0.35 % by mass , 0.42 % by mass , additional CaO Is set to 55% and 63% of the total elapsed time of the blowing acid, the reached P concentration is 0.013 % by mass , 0.011 % by mass , and the generated slag amount index is 0.45, 0.00 % , respectively. 51, and a good (◯) result was obtained as a comprehensive evaluation.
Example 3 is a case where 40 % by mass , which is the lower limit of the residual slag of the previous charge, and Example 4 is a case where 60 % by mass, which is the upper limit of the residual slag of the previous charge, is used. 012 mass% , 0.015 mass% , the generated slag amount index could be 0.54, 0.41, and good (◯) results were obtained for comprehensive evaluation.
Example 5 is a case where the Si concentration of the next charge is 0.10 % by mass , and Example 6 is a case where the Si concentration is 0.60 % by mass. The ultimate P concentration is 0.012 % by mass and 0.014 % , respectively. The mass% and generated slag amount index could be 0.47 and 0.48, and good (◯) results were obtained for comprehensive evaluation.
Example 7 is a case where the additional CaO charging timing is 50% which is the lower limit, and Example 8 is a case where the additional CaO charging timing is 70% which is the upper limit, and the reached P concentration is 0.011 % by mass , 0.00 % , respectively. 014 % by mass , the generated slag amount index could be 0.51 and 0.46, and good (◯) results were obtained for comprehensive evaluation.
[0014]
[Table 1]

[0015]
On the other hand, Comparative Example 1 is a case where the amount of residual slag of the precharge is reduced to 33 % by mass , and the amount of slag necessary to perform sufficient de-P is insufficient, reaching the end of the preliminary process. The P concentration became as high as 0.034 % by mass, and the load in the decarburization refining process increased, resulting in a bad (×) result as a comprehensive evaluation.
Comparative Example 2 is a case where the amount of residual slag slag used for pre-charging is increased to 67 % by mass , and de-P can be performed sufficiently, but the generated slag amount index is as high as 0.82, and the disposal processing cost, etc. Since the increase was caused, the overall evaluation was slightly bad (△).
Comparative Example 3 is a case where the Si concentration of the next charge is lowered to 0.05 % by mass , the basicity of the slag at the time of the preliminary treatment is increased, the hatching of the slag is poor, the de-P efficiency is lowered and reached The P concentration became as high as 0.037, the load in the decarburization refining process increased, and the result was poor (×) as a comprehensive evaluation.
Comparative Example 4 is a case where the Si concentration of the next charge was increased to 0.67 % by mass , and the amount of slag generated increased due to the generation of SiO ₂ , and the generated slag amount index was slightly poor at 0.85. Furthermore, the de-P efficiency decreased due to a decrease in the basicity of the slag, and the reached P concentration became as high as 0.032 % by mass, which was a bad (×) result as a comprehensive evaluation.
In Comparative Example 5, the charging timing of the additional CaO was set to 36%, so that the charging timing was too early. The initial slag amount at the start of the preliminary process increased, and the slag amount increased as the slag amount increased. The FeO concentration decreased, the de-P efficiency through the entire pretreatment decreased, and the reached P concentration increased to 0.035 % by mass, which was a bad (×) result as a comprehensive evaluation.
The comparative example 6 is a case where the charging timing of the additional CaO is 78% and the charging timing is too late, resulting in poor hatching of the slag at the end of the preliminary processing, and the de-P efficiency throughout the preliminary processing is reduced. As a result, the reached P concentration was as high as 0.039 % by mass , and the overall evaluation was bad (×).
Incidentally, the conventional method, the molten iron was charged into the furnace, always, the case of performing the de-Si and de P treatment of molten pig iron for performing吹酸by adding new quicklime iron oxide, throughout the pre-treatment Since the addition amount of quicklime and iron oxide increased, the generated slag amount index was as high as 1.0, leading to an increase in disposal costs and the like, the result was poor (×) as a comprehensive evaluation.
[0016]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and all changes in conditions and the like that do not depart from the gist are within the scope of the present invention.
For example, when performing Si in molten iron, the oxidation of P, in addition to the method according吹酸, sludge, collected dust, iron ore, solid oxygen scavenger such as scale can be used in combination with吹酸.
[0017]
【The invention's effect】
In the molten iron pretreatment process of less generation of slag with converter type container according to claim 1 Symbol placement, remaining 40 to 60 weight percent of the slag generated in pre-processing of the previous hot metal in the converter type vessel In addition, new hot metal is charged into the converter-type vessel, blown acid is applied to perform de-Si treatment and de-P treatment of the hot metal, and CaO is added to the hot metal during the de-Si treatment and de-P treatment. In addition, since the Si removal process and the P removal process are continuously performed, CaO used for the Si removal and P removal pretreatment can be reduced, and the efficiency of the Si removal and the P removal can be increased. The reached P concentration can be reduced, and the disposal cost of waste slag can be reduced.
[0018]
Moreover , since the Si concentration of the new hot metal charged in the converter type vessel is 0.1 to 0.6 % by mass , an excessive increase in the amount of slag and a decrease in the basicity of the slag are suppressed to remove Si. In addition, the de-P efficiency can be stably increased, the ultimate Si concentration and the ultimate P concentration can be lowered, and the load of decarburization and refining in the subsequent process can be reduced.
[0019]
Furthermore , since CaO is added at a time corresponding to 50 to 70% of the total elapsed time of the blowing acid, the slag hatching can be improved and the Si removal and P removal efficiency can be stably increased with a small amount of slag. In addition, it can be reused by suppressing harmful components such as alkali components of the generated slag.
[Brief description of the drawings]
FIG. 1 is an overall view of an upper bottom blown converter applied to a hot metal pretreatment method using a converter type vessel according to an embodiment of the present invention and having a small amount of slag generation.
[Explanation of symbols]
10: Top bottom blowing converter (converter type vessel), 11: Furnace body, 12: Bottom blowing nozzle, 13: Top blowing lance, 14: Storage hopper, 15: Quick lime (flux), 16: Hot metal, 17: Slag , 18: Chute, 19: Deguchi

Claims

In the pretreatment method of hot metal with a small amount of slag generation to perform de-Si treatment and de-P treatment using a converter type vessel,
40 to 60 % by mass of the slag generated in the previous hot metal preliminary treatment is left in the converter type vessel, and the Si concentration in the converter type vessel is 0.1 to 0.6% by mass. The hot metal is charged and blown, and the hot metal is subjected to de-Si treatment and de-P treatment, which are in the middle of the de-Si treatment and de-P treatment and correspond to 50 to 70% of the total elapsed time of the blown acid. A pretreatment method for hot metal with a small amount of slag generation using a converter-type vessel, characterized in that CaO is added to the hot metal at a time and the de-Si treatment and the de-P treatment are continued.