JP3736229B2 - Hot metal processing method - Google Patents
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- JP3736229B2 JP3736229B2 JP27315499A JP27315499A JP3736229B2 JP 3736229 B2 JP3736229 B2 JP 3736229B2 JP 27315499 A JP27315499 A JP 27315499A JP 27315499 A JP27315499 A JP 27315499A JP 3736229 B2 JP3736229 B2 JP 3736229B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、溶銑の脱燐処理後に脱燐スラグの排出を行わないで、連続して溶銑脱硫を行う溶銑の処理方法に関するものである。
【０００２】
【従来の技術】
転炉精錬（主に脱炭精錬）する前に溶銑中の燐、硫黄濃度を低減しておくことは、転炉操業の精錬剤添加量を低減できるメリットがある。
【０００３】
しかし、溶銑の脱燐処理と脱硫処理とを分離して実施する方法が主流となっている。
その理由は、例えば脱硫処理後に、脱硫スラグを排出しないで続けて脱燐処理を行うと、残留するスラグ中の硫黄分が溶銑中に復硫するからである。
【０００４】
これとは逆に、脱燐スラグを排出しないで続けて脱硫処理を行うと、残留するスラグ中の燐分が溶銑中に復燐するからである。また、溶融状態の脱燐スラグ存在下で脱硫剤を溶銑中へ吹き込んでも、脱燐スラグが脱硫反応を阻害するからである。
【０００５】
しかしながら、溶銑脱燐処理と脱硫処理とを分けて行う場合、全処理時間が長くなり溶銑温度が低下し、装入スクラップ量を低減する必要があり、スクラップ比率が低下するという問題がある。
【０００６】
そのため、ＬＤ−ＯＲＰ法という高炉溶銑を転炉方式の溶銑処理専用炉を用いて、酸素上底吹き脱燐処理と底吹き脱硫とを行う方法が文献（ＣＡＭＰ−ＩＳＩＪ、ＶＯＬ４（１９９１）Ｐ．１１５３）に開示されている。
【０００７】
ＬＤ−ＯＲＰの最大の利点は、転炉での粉体底吹き機能を活用し、脱燐中はＣａＣＯ3 の吹き込みによる攪拌力の確保・脱燐促進を図るとともに、脱硫処理中は脱硫剤の高速吹き込みによって短時間脱硫が可能なことである。
【０００８】
【発明が解決しようとする課題】
しかし、この方法は、溶銑脱燐処理後、脱燐スラグを排出しないで続けて脱硫処理を行うため、溶銑温度の低下という問題を回避できるが、溶融脱燐スラグの影響を受けるため、脱硫率が４０〜５０％と低いという問題がある。
【０００９】
本発明の目的は、溶銑脱燐処理後、脱燐スラグを排出しないで続けて脱硫処理を行う方法において、従来に比べて脱硫率を高くすることができる溶銑の処理方法を提供することにある。
【００１０】
【課題を解決するための手段】
本発明者らは、上記目的を達成すべく種々検討を重ね、以下（Ａ）〜（Ｉ）の知見を得た。
【００１１】
（Ａ）ＣａＯによる脱燐反応は下記（１）式にて進行する。
３（ＣａＯ）＋５（ＦｅＯ）＋２［Ｐ］＝３ＣａＯ・Ｐ2 Ｏ5＋５［Ｆｅ](１）
（ ）：スラグ内、［ ］：溶銑内を示す。
上記溶銑脱燐反応を効率的に進めるには、ＣａＯ量を増加させ、しかも溶融させることが必要である。
【００１２】
ところが、ＣａＯの融点は約２５７０℃であり、溶銑温度（１３００〜１４００℃）よりかなり高く、ＣａＯを溶融させるためＣａＦ2 フラックスを用いざるを得なかった。
しかし、溶銑中へのＣａＦ2 添加は、耐火物の溶損を促進するという問題があり、ＣａＦ2 を使用しないでＣａＯを溶融させる方法が求められていた。
【００１３】
（Ｂ）ＣａＯを効率よく溶融する方法を検討した結果、ＣａＯ含有脱燐剤を酸素をキャリアーガスとして溶銑に吹き付けると、ＣａＯが溶融し効率的な脱燐処理が可能となることを見出した。
【００１４】
（Ｃ）ＣａＯ含有脱燐剤を酸素をキャリアーガスとして溶銑に吹き付けると、吹き付け部の溶銑温度が２０００℃以上の高温となり、しかも酸素と溶銑との反応により（ＦｅＯ）が多量に生成する。
【００１５】
この高温で（ＦｅＯ）が多量に生成している場所（以下、火点ともいう）にＣａＯを吹き付けると、ＣａＯがＦｅＯと反応して融点の低い化合物を生成する。従って、添加されたＣａＯは極めて速やかに溶融化（スラグ化ともいう）し、脱燐反応が効率的に進行する。
【００１６】
（Ｄ）低Ｓｉ溶銑（［Ｓｉ］≦０．１重量％（以下、単に％で重量％を表す））を脱燐する場合、ＳｉＯ2 の生成が少なくなるため、スラグ塩基度（重量比：ＣａＯ／ＳｉＯ2 ）が非常に高くなり生成スラグの融点が上がるため脱燐終了時にはスラグが固化する。
【００１７】
しかし、酸素をキャリアーガスとして溶銑に吹き付けられたＣａＯは火点付近ではスラグ化するため、脱燐に十分寄与し、処理後の溶銑中の［Ｐ］濃度を０．０２５％以下にすることができる。
【００１８】
すなわち、酸素をキャリアーガスとして溶銑に吹き付けられたＣａＯは火点付近ではスラグ化し、脱燐に十分寄与する。しかし、吹き付け処理を終了すると、直ちにスラグが固化する。
【００１９】
（Ｅ）一方、通常溶銑（［Ｓｉ］約０．３％）を脱燐する場合でも、酸素をキャリアーガスとして溶銑にＣaＯを吹き付けて、塩基度（重量比：ＣａＯ／ＳｉＯ2 ）を１．７以上にまで高めると、スラグ融点が急激に上がり、スラグが固化す る。
【００２０】
しかし、上記（Ｄ）の場合と同様に、酸素をキャリアーガスとして溶銑に吹き付けられたＣａＯは火点付近ではスラグ化するため、脱燐に十分寄与し、処理後の溶銑中の［Ｐ］濃度を０．０２５％以下にすることができる。
【００２１】
（Ｆ）更に、この様に脱燐スラグが固化すると、スラグ中の（Ｐ2 Ｏ5 ）が溶銑中の［Ｃ］によって還元される速度が低下するため、復燐はほとんど生じない。
【００２２】
（Ｇ）脱燐スラグが固化した後に、脱硫剤を溶銑に吹き込むと、脱燐スラグが溶融状態である場合に比べ、非常に効率よく脱硫できる。これは、脱硫剤と固化した脱燐スラグとの反応速度が極めて遅く、脱燐スラグが脱硫反応をほとんど阻害しないからである。
【００２３】
（Ｈ）また、脱硫剤による脱燐スラグの還元反応も生じにくいため、脱硫処理時の復燐反応もほとんど生じない。
【００２４】
本発明は、以上の知見に基づいて成されたもので、その要旨は、下記の通りである。
（１）酸素をキャリアーガスとしてＣａＯ含有脱燐剤を上吹きランスを使用して溶銑の浴面に吹き付けて脱燐し、脱燐処理後のスラグ塩基度（重量比：ＣａＯ／ＳｉＯ２）を１．７以上とした脱燐スラグを排出することなく脱硫剤を脱燐処理後の溶銑中に吹き込んで脱硫することを特徴とする溶銑の処理方法。
【００２５】
（２）ＣａＯ含有脱燐剤が、ＣａＯと、Ａｌ ２ Ｏ ３ 、Ｆｅ ２ Ｏ ３ の内少なくとも一種とを含有することを特徴とする上記（１）に記載の溶銑の処理方法。
【００２６】
（３）脱硫剤が、ＣａＯ、ＣａＯ含有金属Ａｌ、Ｎａ2 ＣＯ3 、ＣａＣ2 、金属Ｍｇの内少なくとも一種を含有することを特徴とする上記（１）または（２）に記載の溶銑の処理方法。
【００２７】
【発明の実施の形態】
脱燐に使用する炉としては、上底吹き転炉が良い。
しかしながら、脱燐処理は、脱炭より負荷が軽いので、脱燐専用炉を用いることもできる。
【００２８】
酸素をキャリアーガスとしてＣａＯ含有脱燐剤を溶銑に吹き付けるには、上吹きランスが使用できる。
キャリアーガスとして使用する酸素は、工業用の純酸素が使用できる。使用する酸素量は溶銑１トン（以下、単にｔともいう）当たり７〜１３ｋｇが望ましい。
【００２９】
その理由は、７ｋｇ/ｔ満では脱燐に必要な酸素量を付与できないおそれがあり、１３kg/tを超えると過剰な脱炭反応が生じ、この後の脱炭工程での熱源不足を生じるおそれがあるからである。
【００３０】
また、ＣａＯ添加量は溶銑中の［Ｓｉ］濃度や［Ｐ］濃度に依存するが、溶銑中の［Ｐ］濃度が約０．１％の場合、溶銑ｔ当たり５〜２０ｋｇが望ましい。
ＣａＯ量が５ｋｇ未満では、スラグ中ＣａＯの活量が小さすぎて溶銑中の［Ｐ］をスラグ中の（ＦｅＯ）で酸化しても、スラグ中に燐酸カルシウム（例えば３ＣａＯ・Ｐ2 Ｏ5 ）の形で安定して固定できない可能性がある。その結果、処理後の［Ｐ］を目標値：０．０２５％以下にできないおそれがある。
【００３１】
一方、２０ｋｇを超えてＣａＯを溶銑に吹き付けても、脱燐率は飽和し、ほとんど変わらないおそれがある。
脱燐剤はＣａＯと、Ａｌ ２ Ｏ ３ 、Ｆｅ ２ Ｏ ３ の少なくとも一種とを含有すると脱燐率が向上できて好ましい。
【００３２】
ＣａＯにＡｌ２Ｏ３を混合した場合、ＣａＯがＡｌ２Ｏ３と反応して融点が降下し、火点付近におけるＣａＯのスラグ化がさらに促進され脱燐率が向上できる。
ＣａＯ量に対するＡｌ２Ｏ３量の重量比（Ａｌ２Ｏ３／ＣａＯ）は、１／２０〜１／２とするのが望ましい。
【００３３】
その理由は１／２０より小さいと、Ａｌ2 Ｏ3 によるＣａＯの融点降下効果が小さすぎて、脱燐率向上に寄与できないおそれがあり、１／２より大きいと、脱燐率向上が飽和し、スラグ量が増加するおそれがあり好ましくないからである。
【００３４】
また、ＣａＯにＦｅ２Ｏ３を混合した場合、火点付近における（ＦｅＯ）濃度が増加するため、火点付近におけるＣａＯのスラグ化がＡｌ２Ｏ３を混合した場合と同様に促進され、さらに脱燐反応が進行する領域の酸素ポテンシャルが増加するため脱燐率が飛躍的に向上できる。
【００３５】
ＣａＯに対するＦｅ２Ｏ３の重量比（Ｆｅ２Ｏ３／ＣａＯ）を１／２以下とするのが望ましい。
【００３６】
その理由は、Ｆｅ2 Ｏ3 は冷却能が大きいので、１／２を超えて添加しても火点における酸素ポテンシャルは増加するものの、火点の温度が低下してＣａＯのスラグ化が困難となるおそれがあるからである。
【００３７】
ＣａＯにＡｌ2 Ｏ3 およびＦｅ2 Ｏ3 を適当量添加混合すると、相乗効果により脱燐率は飛躍的に向上するので、さらに好ましい。
脱燐処理後のスラグ塩基度（重量比：ＣａＯ／ＳｉＯ2 ）としては１．７以上とする。
【００３８】
スラグ塩基度が１．７未満であると、スラグが十分に固化しないおそれがあるからである。
ＣａＯ添加溶銑脱燐処理後、脱燐スラグを排出することなくＣａＯ、ＣａＯ含有金属Ａｌ、Ｎａ2 ＣＯ3 、ＣａＣ2 、金属Ｍｇの内少なくとも一種を含有する脱硫剤を添加すると、脱硫率６０％以上を達成できる。
【００３９】
脱硫剤を脱燐溶銑中に添加する方法は、底吹き羽口、浸漬ノズルが使用できる。
なお、Ｎａ2 ＣＯ3 以外は全て強還元性物質なので、脱燐スラグ中の（Ｐ2 Ｏ5 ）を還元して復燐を生じる可能性があるが、脱燐スラグが脱燐処理終了時には固化しているため復燐は認められない。
【００４０】
ＣａＯ含有脱燐剤および脱硫剤の粒径は、１０〜１０００μｍであればよい。１０μｍ未満とするには、製造コストが非常に高くなるおそれがあり、１０００μｍを超えるとキャリアーガスと混合してもスムースに流れないため配管内に堆積するおそれがあるからである。
【００４１】
【実施例】
（比較例）
試験転炉に成分が［Ｃ］約４．５％、［Ｓｉ］約０．２５％、［Ｐ］約０．１０％、［Ｓ］約０．０２５％、脱燐処理前温度１３２０℃の溶銑２ｔを装入した。
【００４２】
次に溶銑へ塊状（平均粒径：３０mm）の鉄鉱石２４ｋｇ、塊状（平均粒径：３０mm）の生石灰１９．３ｋｇを上置き添加し、塩基度（重量比：ＣａＯ／ＳｉＯ2 ）を１．８とした後、上吹きランスから溶銑ｔ当たり１．３Ｎｍ3 ／min の酸素を約７分間溶銑に吹き付けた。
【００４３】
また、処理中底吹き羽口からはＡｒガスを溶銑ｔ当たり、０．５０Ｎｍ3 ／min 吹き込んで溶銑およびスラグを攪拌した。
脱燐吹錬終了時の溶銑温度は１３５０℃、スラグ塩基度（重量比：ＣａＯ／ＳｉＯ2 ）１．５で、処理後の［Ｐ］濃度は０．０２４％、［Ｓ］０．０２４％、（Ｔ．Ｆｅ）１０％であった。
【００４４】
そして、リンス（上吹きランスから酸素を溶銑に吹き付けない状態で、底吹き羽口からＡｒガスを継続して吹き込んで溶銑およびスラグを攪拌する操作をいう）を３分行った後、底吹き羽口から溶銑中へ溶銑ｔ当たり４ｋｇのＮａ2 ＣＯ3 を４分間で吹き込んだ。なお、リンスを３分行ってもスラグフォーミングは鎮静しきらず、スラグは半溶融状態であった。
【００４５】
Ｎａ2 ＣＯ3 吹き込み終了時の溶銑中の［Ｓ］濃度は０．０１５％であり、脱硫率は４０％と低かった。なお、脱硫処理中に復燐は進行せず、溶銑中の［Ｐ］濃度は０．０２４％のままだった。
【００４６】
（本発明例１）
試験転炉に成分が［Ｃ］約４．５％、［Ｓｉ］約０．２４％、［Ｐ］約０．１０％、［Ｓ］約０．０２４％、脱燐処理前温度１３１５℃の溶銑２ｔを装入した。
【００４７】
次に溶銑へ塊状（平均粒径：３０mm）の鉄鉱石２４ｋｇを上置き添加した後、上吹きランスから溶銑ｔ当たり１．３Ｎｍ3 ／min の酸素と共に粉状（平均粒径：１００μｍ）のＣａＯ１９．６ｋｇを約７分間溶銑に吹き付けて塩基度（重量比：ＣａＯ／ＳｉＯ2 ）を１．９とした。
【００４８】
また、処理中底吹き羽口からはＡｒガスを溶銑ｔ当たり、０．５０Ｎｍ3 ／min 吹き込んで溶銑およびスラグを攪拌した。
脱燐吹錬終了時の溶銑温度は１３４５℃、塩基度（重量比：ＣａＯ／ＳｉＯ2 ）１．９で、処理後の［Ｐ］濃度は０．０１８％、［Ｓ］０．０２４％、（Ｔ．Ｆｅ）８％であった。
【００４９】
そして、リンスを２分行った後、底吹き羽口から溶銑中へ溶銑ｔ当たり４ｋｇの粉状（平均粒径：２００μｍ）のＮａ2 ＣＯ3 を４分間で吹き込んだ。なお、リンスを２分行うと、スラグフォーミングは完全に鎮静し、スラグはほぼ固化していた。
【００５０】
Ｎａ2 ＣＯ3 吹き込み終了時の溶銑中の［Ｓ］濃度は、０．００５％であり脱硫率は７９％と高かった。また脱硫処理中に復燐はなく、溶銑中の［Ｐ］濃度は０．０１８％と低く、目標［Ｐ］濃度の０．０２５％以下を達成できた。
【００５１】
（本発明例２）
スクラップ３０ｋｇを事前に装入しておいた試験転炉に、成分が［Ｃ］約４．５％、［Ｓｉ］約０．１０％、［Ｐ］約０．１０％、［Ｓ］約０．０２４％、脱燐処理前温度１３１５℃の溶銑２ｔを装入した。
【００５２】
次に溶銑へ塊状（平均粒径：３０mm）の鉄鉱石２４ｋｇを上置き添加した後、上吹きランスから溶銑ｔ当たり１．３Ｎｍ3 ／min の酸素と共に粉状（平均粒径：１００μｍ）のＣａＯ１５ｋｇを約７分間溶銑に吹き付けて塩基度（重量比：ＣａＯ／ＳｉＯ2 ）を３．５とした。
また、処理中底吹き羽口からはＡｒガスを溶銑ｔ当たり、０．５０Ｎｍ3 ／min 吹き込んで溶銑およびスラグを攪拌した。
【００５３】
脱燐吹錬終了時の溶銑温度は１３４４℃、塩基度（重量比：ＣａＯ／ＳｉＯ2 ）３．４で、処理後の［Ｐ］濃度は０．０２０％、［Ｓ］０．０２０％、（Ｔ．Ｆｅ）８％であった。なお、吹錬終了直後にスラグはほぼ固化した。そこで直ちに、底吹き羽口から溶銑中へ溶銑ｔ当たり４ｋｇの粉状（平均粒径：２００μｍ）の９０％ＣａＯ−１０％Ａｌを４分間で吹き込んだ。
【００５４】
９０％ＣａＯ−１０％Ａｌ吹き込み終了時の溶銑中の［Ｓ］濃度は０．００７％であり、脱硫率は７１％と高かった。また脱硫処理中に復燐はなく、溶銑中の［Ｐ］濃度は０．０２０％と低く、目標［Ｐ］濃度の０．０２５％以下を達成できた。
【００５５】
（本発明例３）
試験転炉に成分が［Ｃ］約４．５％、［Ｓｉ］約０．２５％、［Ｐ］約０．１０％、［Ｓ］約０．０２５％、脱燐処理前温度１３１５℃の溶銑２ｔを装入した。
【００５６】
次に溶銑へ塊状の鉄鉱石２４ｋｇを上置き添加した後、上吹きランスから溶銑ｔ当たり１．３Ｎｍ3 ／min の酸素と共に粉状（平均粒径：１００μｍ）の８０％ＣａＯ−２０％Ａｌ2 Ｏ3 混合物２４．５ｋｇを約７分間溶銑に吹き付けて塩基度（重量比：ＣａＯ／ＳｉＯ2 ）を１．８とした。
【００５７】
また、処理中底吹き羽口からはＡｒガスを溶銑ｔ当たり、０．５０Ｎｍ3 ／min 吹き込んで溶銑およびスラグを攪拌した。
脱燐吹錬終了時の溶銑温度は１３４０℃、塩基度（重量比：ＣａＯ／ＳｉＯ2 ）１．８で、処理後の［Ｐ］濃度は０．０１４％、［Ｓ］０．０２４％、（Ｔ．Ｆｅ）８％、（Ａｌ2 Ｏ3 ）１２％であった。
【００５８】
そして、リンスを２分行った後、底吹き羽口から溶銑中へ溶銑ｔ当たり４ｋｇの粉状（平均粒径：２００μｍ）のＣａＣ2 を４分間で吹き込んだ。なお、リンスを２分行うと、スラグフォーミングは完全に鎮静し、スラグはほぼ固化していた。
【００５９】
ＣａＣ2 吹き込み終了時の溶銑中の［Ｓ］濃度は０．００２％であり、脱硫率は９２％と高かった。また脱硫処理中に復燐はなく、溶銑中の［Ｐ］濃度は０．０１４％と低く、目標［Ｐ］濃度の０．０２５％以下を達成できた。
【００６０】
（本発明例４）
試験転炉に成分が［Ｃ］約４．５％、［Ｓｉ］約０．２４％、［Ｐ］約０．１０％、［Ｓ］約０．０２３％、脱燐処理前温度１３１８℃の溶銑２ｔを装入した。
【００６１】
次に溶銑へ塊状（平均粒径：３０mm）の鉄鉱石１８ｋｇを上置き添加した後、上吹きランスから溶銑ｔ当たり１．３Ｎｍ3 ／min の酸素と共に粉状（平均粒径：１００μｍ）の７０％ＣａＯ−１０％Ａｌ2 Ｏ3 −２０％Ｆｅ2 Ｏ3 混合物３０ｋｇを約７分間溶銑に吹き付けて塩基度（重量比：ＣａＯ／ＳｉＯ2 ）を２．０とした。
【００６２】
また、処理中底吹き羽口からはＡｒガスを溶銑ｔ当たり、０．５０Ｎｍ3 ／min 吹き込んで溶銑およびスラグを攪拌した。
脱燐吹錬終了時の溶銑温度は１３４２℃、塩基度（重量比：ＣａＯ／ＳｉＯ2 ）２．０で、処理後の［Ｐ］濃度は０．００２％、［Ｓ］０．０２４％、（Ｔ．Ｆｅ）８％、（Ａｌ2 Ｏ3 ）５％であった。
【００６３】
そして、リンスを２分行った後、底吹き羽口から溶銑中へ溶銑ｔ当たり４ｋｇの粒状（平均粒径：５００μｍ）の金属Ｍｇを４分間で吹き込んだ。なお、リンスを２分行うと、スラグフォーミングは完全に鎮静し、スラグはほぼ固化していた。
【００６４】
金属Ｍｇ吹き込み終了時の溶銑中の［Ｓ］濃度は０．００３％であり、脱硫率は８７％と高かった。また脱硫処理中に復燐はなく、溶銑中の［Ｐ］濃度は０．００２％と低く、目標［Ｐ］濃度の０．０２５％以下を達成できた。
【００６５】
（本発明例５）
スクラップ３０ｋｇを事前に装入しておいた試験転炉に、成分が［Ｃ］約４．５％、［Ｓｉ］約０．１０％、［Ｐ］約０．１０％、［Ｓ］約０．０２４％、脱燐処理前温度１３１５℃の溶銑２ｔを装入した。
【００６６】
次に溶銑へ塊状（平均粒径：３０mm）の鉄鉱石２４kgを上置き添加した後、上吹きランスから溶銑ｔ当たり１．３Ｎｍ3 ／min の酸素と共に粉状（平均粒径：１００μｍ）のＣaＯ１５ｋｇを約７分間溶銑に吹き付けて塩基度（重量比：ＣａＯ／ＳｉＯ2 ）を３．５とした。
【００６７】
また、処理中底吹き羽口からはＡrガスを溶銑ｔ当たり、０．５０Ｎｍ3 ／min吹き込んで溶銑およびスラグを攪拌した。
脱燐吹錬終了時の溶銑温度は１３４２℃、塩基度（重量比：ＣａＯ／ＳｉＯ2 ）３．４で、処理後の［Ｐ］濃度は０．０２０％、［Ｓ］０．０２０％、（Ｔ．Ｆｅ）８％であった。
【００６８】
また、吹錬終了直後にスラグはほぼ固化した。
そこで直ちに、底吹き羽口から溶銑中へ溶銑ｔ当たり４ｋｇの粉状（平均粒径：２００μｍ）のＣaＯ単体を４分間で吹き込んだ。
【００６９】
ＣaＯ吹き込み終了時の溶銑中の［Ｓ］濃度は０．００８％であり、脱硫率は６７％と高かった。また脱硫処理中に復燐はなく、溶銑中の［Ｐ］濃度は０．００２０％と低く、目標［Ｐ］濃度の０．０２５％以下を達成できた。
【００７０】
【発明の効果】
本発明によれば、（１）転炉または転炉型の溶銑予備処理専用炉を用いて、脱燐処理後、スラグを排出することなく続けて脱硫処理を行うことができる。（２）脱硫率は従来法の５０％を大きく凌駕するを実現できるのである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hot metal treatment method for continuously performing hot metal desulfurization without discharging dephosphorization slag after dephosphorization of hot metal.
[0002]
[Prior art]
Reducing the phosphorus and sulfur concentrations in the hot metal before converter refining (mainly decarburization refining) has the advantage of reducing the amount of refining agent added in the converter operation.
[0003]
However, a method in which the hot metal dephosphorization process and the desulfurization process are performed separately is the mainstream.
The reason is that, for example, if the dephosphorization process is continued without discharging the desulfurization slag after the desulfurization process, the sulfur content in the remaining slag is resulfurized in the hot metal.
[0004]
On the contrary, if the desulfurization treatment is performed without discharging the dephosphorization slag, the remaining phosphorus in the slag is restored to the hot metal. Further, even if a desulfurizing agent is blown into the hot metal in the presence of molten dephosphorization slag, the dephosphorization slag inhibits the desulfurization reaction.
[0005]
However, when the hot metal dephosphorization process and the desulfurization process are performed separately, the total processing time becomes longer, the hot metal temperature decreases, the amount of charged scrap needs to be reduced, and the scrap ratio decreases.
[0006]
Therefore, a method of performing oxygen top bottom blowing dephosphorization treatment and bottom blowing desulfurization using a blast furnace hot metal called LD-ORP method using a furnace for exclusive use of a converter type hot metal treatment is disclosed in the literature (CAMP-ISIJ, VOL4 (1991) P.A. 1153).
[0007]
The greatest advantage of LD-ORP is that it utilizes the powder bottom blowing function in the converter to ensure stirring power and promote dephosphorization by blowing CaCO 3 during dephosphorization, and the desulfurizing agent during desulfurization treatment. Desulfurization is possible for a short time by high-speed blowing.
[0008]
[Problems to be solved by the invention]
However, since this method continuously performs desulfurization treatment without discharging the dephosphorization slag after the hot metal dephosphorization treatment, it can avoid the problem of lowering the hot metal temperature. There is a problem that it is as low as 40 to 50%.
[0009]
An object of the present invention is to provide a hot metal treatment method capable of increasing the desulfurization rate as compared with the conventional method in the method of performing the desulfurization treatment without discharging the dephosphorization slag after the hot metal dephosphorization treatment. .
[0010]
[Means for Solving the Problems]
The inventors of the present invention have made various studies to achieve the above object, and have obtained the following findings (A) to (I).
[0011]
(A) The dephosphorization reaction with CaO proceeds according to the following formula (1).
3 (CaO) +5 (FeO) +2 [P] = 3CaO · P 2 O 5 +5 [Fe] (1)
(): In slag, []: In hot metal.
In order to advance the hot metal dephosphorization reaction efficiently, it is necessary to increase the amount of CaO and to melt it.
[0012]
However, the melting point of CaO is about 2570 ° C., which is considerably higher than the hot metal temperature (1300 to 1400 ° C.), and a CaF 2 flux has to be used to melt CaO.
However, the addition of CaF 2 into the hot metal has a problem of accelerating the melting of the refractory, and a method for melting CaO without using CaF 2 has been demanded.
[0013]
(B) As a result of investigating a method of efficiently melting CaO, it was found that when a CaO-containing dephosphorizing agent is sprayed on hot metal using oxygen as a carrier gas, CaO melts and efficient dephosphorization processing becomes possible.
[0014]
(C) When the CaO-containing dephosphorizing agent is sprayed on hot metal using oxygen as a carrier gas, the hot metal temperature of the sprayed part becomes a high temperature of 2000 ° C. or more, and a large amount of (FeO) is generated by the reaction between oxygen and hot metal.
[0015]
When CaO is sprayed onto a place where a large amount of (FeO) is generated at this high temperature (hereinafter also referred to as a fire point), CaO reacts with FeO to produce a compound having a low melting point. Therefore, the added CaO melts very quickly (also referred to as slag formation), and the dephosphorization reaction proceeds efficiently.
[0016]
(D) When dephosphorizing low Si hot metal ([Si] ≦ 0.1% by weight (hereinafter simply referred to as% by weight)), the production of SiO 2 is reduced, so slag basicity (weight ratio: Since CaO / SiO 2 ) becomes very high and the melting point of the produced slag increases, the slag solidifies at the end of dephosphorization.
[0017]
However, since CaO blown to the hot metal using oxygen as a carrier gas is slagged near the fire point, it contributes sufficiently to dephosphorization, and the [P] concentration in the hot metal after treatment may be 0.025% or less. it can.
[0018]
That is, CaO sprayed on the hot metal using oxygen as a carrier gas slags near the fire point and contributes sufficiently to dephosphorization. However, the slag solidifies immediately after finishing the spraying process.
[0019]
(E) On the other hand, even when dephosphorizing normal hot metal ([Si] approximately 0.3%), CaO is sprayed onto the hot metal using oxygen as a carrier gas, and the basicity (weight ratio: CaO / SiO 2 ) is set to 1. When it is increased to 7 or more, the slag melting point rises rapidly and the slag solidifies.
[0020]
However, as in the case of the above (D), CaO sprayed on the hot metal using oxygen as a carrier gas slags near the fire point, so that it contributes sufficiently to dephosphorization, and the [P] concentration in the hot metal after the treatment Can be made 0.025% or less.
[0021]
(F) Further, when the dephosphorized slag is solidified in this way, the rate at which (P 2 O 5 ) in the slag is reduced by [C] in the hot metal is lowered, and therefore, there is almost no recovery.
[0022]
(G) When the dephosphorization agent is blown into the hot metal after the dephosphorization slag is solidified, the desulfurization slag can be desulfurized very efficiently compared to the case where the dephosphorization slag is in a molten state. This is because the reaction rate between the desulfurization agent and the solidified dephosphorization slag is extremely slow, and the dephosphorization slag hardly inhibits the desulfurization reaction.
[0023]
(H) In addition, since the reduction reaction of the dephosphorization slag by the desulfurization agent does not easily occur, the dephosphorization reaction during the desulfurization treatment hardly occurs.
[0024]
The present invention has been made based on the above findings, and the gist thereof is as follows.
(1) CaO-containing dephosphorization agent is blown onto the hot metal bath surface using oxygen as a carrier gas and dephosphorization, and the slag basicity (weight ratio: CaO / SiO 2 ) after dephosphorization is obtained. A hot metal treatment method comprising desulfurization by blowing a desulfurizing agent into hot metal after dephosphorization treatment without discharging dephosphorization slag of 1.7 or more.
[0025]
(2) The hot metal treatment method as described in (1) above, wherein the CaO-containing dephosphorizing agent contains CaO and at least one of Al 2 O 3 and Fe 2 O 3 .
[0026]
(3) The hot metal treatment as described in (1) or (2) above, wherein the desulfurizing agent contains at least one of CaO, CaO-containing metal Al, Na 2 CO 3 , CaC 2 and metal Mg. Method.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
As a furnace used for dephosphorization, a top-bottom blow converter is preferable.
However, since the dephosphorization treatment has a lighter load than decarburization, a dedicated dephosphorization furnace can be used.
[0028]
An upper blowing lance can be used to spray the CaO-containing dephosphorizing agent on the hot metal using oxygen as a carrier gas.
The oxygen used as the carrier gas can be industrial pure oxygen. The amount of oxygen used is preferably 7 to 13 kg per ton of hot metal (hereinafter also simply referred to as t).
[0029]
The reason is that if it is less than 7 kg / t, the amount of oxygen necessary for dephosphorization may not be imparted, and if it exceeds 13 kg / t, an excessive decarburization reaction may occur, resulting in a shortage of heat source in the subsequent decarburization process. Because there is.
[0030]
The CaO addition amount depends on the [Si] concentration and [P] concentration in the hot metal, but when the [P] concentration in the hot metal is about 0.1%, 5 to 20 kg per hot metal t is desirable.
When the amount of CaO is less than 5 kg, even if the activity of CaO in the slag is too small and [P] in the hot metal is oxidized with (FeO) in the slag, calcium phosphate (for example, 3CaO · P 2 O 5 ) is contained in the slag. There is a possibility that it cannot be fixed stably in the form of. As a result, there is a possibility that the [P] after the processing cannot be set to the target value: 0.025% or less.
[0031]
On the other hand, even if CaO is sprayed over the hot metal exceeding 20 kg, the dephosphorization rate is saturated and there is a possibility that it hardly changes.
It is preferable that the dephosphorizing agent contains CaO and at least one of Al 2 O 3 and Fe 2 O 3 because the dephosphorization rate can be improved.
[0032]
When Al 2 O 3 is mixed with CaO, CaO reacts with Al 2 O 3 to lower the melting point, further promoting the slagging of CaO near the fire point and improving the dephosphorization rate.
The amount of Al 2 O 3 weight ratio CaO amount (Al 2 O 3 / CaO) is desirably set to 1 / 20-1 / 2.
[0033]
The reason is that if it is smaller than 1/20, the melting point lowering effect of CaO by Al 2 O 3 is too small and may not contribute to the improvement of the dephosphorization rate. This is because the slag amount may increase, which is not preferable.
[0034]
Further, when Fe 2 O 3 is mixed with CaO , the (FeO) concentration in the vicinity of the fire point increases, so that the slagging of CaO near the fire point is promoted in the same manner as when Al 2 O 3 is mixed. Since the oxygen potential in the region where the dephosphorization reaction proceeds increases, the dephosphorization rate can be dramatically improved.
[0035]
Ratio by weight of Fe 2 O 3 with respect to CaO (Fe 2 O 3 / CaO ) and is desirably set to 1/2 or less.
[0036]
The reason for this is that Fe 2 O 3 has a large cooling capacity, so even if added over 1/2, the oxygen potential at the fire point increases, but the temperature at the fire point decreases and it is difficult to slag CaO. This is because there is a risk of becoming.
[0037]
It is more preferable to add appropriate amounts of Al 2 O 3 and Fe 2 O 3 to CaO, since the dephosphorization rate is dramatically improved by a synergistic effect.
The slag basicity (weight ratio: CaO / SiO 2 ) after dephosphorization is set to 1.7 or more.
[0038]
It is because there exists a possibility that slag may not fully solidify that slag basicity is less than 1.7.
When a desulfurization agent containing at least one of CaO, CaO-containing metal Al, Na 2 CO 3 , CaC 2 and metal Mg is added without discharging dephosphorization slag after the CaO-added hot metal dephosphorization treatment, the desulfurization rate is 60%. The above can be achieved.
[0039]
As a method of adding the desulfurizing agent to the dephosphorizing hot metal, a bottom blowing tuyere and an immersion nozzle can be used.
Since all substances except Na 2 CO 3 are strongly reducing substances, there is a possibility that (P 2 O 5 ) in the dephosphorization slag is reduced to generate rephosphorus, but the dephosphorization slag is solidified at the end of the dephosphorization process. Therefore, recovery is not allowed.
[0040]
The particle size of the CaO-containing dephosphorizing agent and desulfurizing agent may be 10 to 1000 μm. If the thickness is less than 10 μm, the production cost may be very high, and if it exceeds 1000 μm, even if mixed with the carrier gas, it does not flow smoothly, and thus may be deposited in the pipe.
[0041]
【Example】
(Comparative example)
In the test converter, [C] is about 4.5%, [Si] is about 0.25%, [P] is about 0.10%, [S] is about 0.025%, and the temperature before dephosphorization is 1320 ° C. Hot metal 2t was charged.
[0042]
Next, 24 kg of massive (average particle size: 30 mm) iron ore and 19.3 kg of massive (average particle size: 30 mm) quicklime are added to the hot metal, and the basicity (weight ratio: CaO / SiO 2 ) is set to 1. After setting to 8, 1.3 Nm 3 / min of oxygen per hot metal t was sprayed onto the hot metal for about 7 minutes from the top blowing lance.
[0043]
Moreover, 0.50 Nm 3 / min was blown into the bottom blowing tuyere during the treatment per molten iron t to stir the molten iron and slag.
The hot metal temperature at the end of dephosphorization was 1350 ° C., the slag basicity (weight ratio: CaO / SiO 2 ) 1.5, and the [P] concentration after treatment was 0.024% and [S] 0.024%. , (T.Fe) was 10%.
[0044]
Then, after rinsing (referring to an operation in which Ar gas is continuously blown from the bottom blowing tuyer and oxygen is not blown from the top blowing lance to stir the molten iron and slag), the bottom blowing is performed. 4 kg of Na 2 CO 3 per molten iron was blown into the molten iron from the mouth for 4 minutes. In addition, even if rinsing was performed for 3 minutes, the slag forming was not subdued, and the slag was in a semi-molten state.
[0045]
At the end of Na 2 CO 3 blowing, the [S] concentration in the hot metal was 0.015%, and the desulfurization rate was as low as 40%. Note that rephosphorization did not proceed during the desulfurization treatment, and the [P] concentration in the hot metal remained at 0.024%.
[0046]
(Invention Example 1)
In the test converter, [C] is about 4.5%, [Si] is about 0.24%, [P] is about 0.10%, [S] is about 0.024%, and the temperature before dephosphorization is 1315 ° C. Hot metal 2t was charged.
[0047]
Next, after adding 24 kg of iron ore in a lump shape (average particle size: 30 mm) to the hot metal, CaO19 in the form of powder (average particle size: 100 μm) with 1.3 Nm 3 / min oxygen per hot metal t from the top blowing lance. .6 kg was sprayed on the hot metal for about 7 minutes to adjust the basicity (weight ratio: CaO / SiO 2 ) to 1.9.
[0048]
Moreover, 0.50 Nm 3 / min was blown into the bottom blowing tuyere during the treatment per molten iron t to stir the molten iron and slag.
The hot metal temperature at the end of dephosphorization was 1345 ° C., the basicity (weight ratio: CaO / SiO 2 ) was 1.9, and the [P] concentration after the treatment was 0.018%, [S] 0.024%, (T.Fe) was 8%.
[0049]
Then, after rinsing for 2 minutes, 4 kg of powdery (average particle size: 200 μm) Na 2 CO 3 per molten iron t was blown into the molten iron from the bottom blowing tuyere for 4 minutes. When rinsing was performed for 2 minutes, the slag forming was completely calmed down and the slag was almost solidified.
[0050]
The [S] concentration in the hot metal at the end of Na 2 CO 3 blowing was 0.005%, and the desulfurization rate was as high as 79%. In addition, there was no rephosphorization during the desulfurization treatment, and the [P] concentration in the hot metal was as low as 0.018%, and the target [P] concentration was 0.025% or less.
[0051]
(Invention Example 2)
In a test converter in which 30 kg of scrap was charged in advance, the components were [C] about 4.5%, [Si] about 0.10%, [P] about 0.10%, [S] about 0 .024%, 2t of hot metal having a temperature before dephosphorization of 1315 ° C. was charged.
[0052]
Next, after adding 24 kg of iron ore in a lump shape (average particle size: 30 mm) to the hot metal, 15 kg of CaO in powder form (average particle size: 100 μm) with 1.3 Nm 3 / min of oxygen per hot metal t from the top blowing lance. Was sprayed on the hot metal for about 7 minutes to adjust the basicity (weight ratio: CaO / SiO 2 ) to 3.5.
Moreover, 0.50 Nm 3 / min was blown into the bottom blowing tuyere during the treatment per molten iron t to stir the molten iron and slag.
[0053]
The hot metal temperature at the end of dephosphorization was 1344 ° C., the basicity (weight ratio: CaO / SiO 2 ) 3.4, and the [P] concentration after treatment was 0.020%, [S] 0.020%, (T.Fe) was 8%. The slag almost solidified immediately after the blowing. Therefore, 4 kg of 90% CaO-10% Al (average particle size: 200 μm) per molten iron t was blown into the molten iron from the bottom blowing tuyere for 4 minutes.
[0054]
The [S] concentration in the hot metal at the end of the 90% CaO-10% Al blowing was 0.007%, and the desulfurization rate was as high as 71%. In addition, there was no rephosphorization during the desulfurization treatment, and the [P] concentration in the hot metal was as low as 0.020%, and the target [P] concentration was 0.025% or less.
[0055]
(Invention Example 3)
In the test converter, [C] is about 4.5%, [Si] is about 0.25%, [P] is about 0.10%, [S] is about 0.025%, and the temperature before dephosphorization is 1315 ° C. Hot metal 2t was charged.
[0056]
Next, after adding 24 kg of massive iron ore to hot metal, 80% CaO-20% Al 2 in powder form (average particle size: 100 μm) together with 1.3 Nm 3 / min of oxygen per hot metal t from the top blowing lance. The basicity (weight ratio: CaO / SiO 2 ) was adjusted to 1.8 by spraying 24.5 kg of the O 3 mixture on the hot metal for about 7 minutes.
[0057]
Moreover, 0.50 Nm 3 / min was blown into the bottom blowing tuyere during the treatment per molten iron t to stir the molten iron and slag.
The hot metal temperature at the end of dephosphorization was 1340 ° C., the basicity (weight ratio: CaO / SiO 2 ) 1.8, and the [P] concentration after the treatment was 0.014%, [S] 0.024%, (T.Fe) 8%, (Al 2 O 3 ) 12%.
[0058]
Then, after rinsing for 2 minutes, 4 kg of powdery (average particle size: 200 μm) CaC 2 per molten iron t was blown into the molten iron from the bottom blowing tuyere for 4 minutes. When rinsing was performed for 2 minutes, the slag forming was completely calmed down and the slag was almost solidified.
[0059]
The [S] concentration in the hot metal at the end of the CaC 2 blowing was 0.002%, and the desulfurization rate was as high as 92%. In addition, there was no rephosphorization during the desulfurization treatment, and the [P] concentration in the hot metal was as low as 0.014%, and the target [P] concentration was 0.025% or less.
[0060]
(Invention Example 4)
In the test converter, [C] is about 4.5%, [Si] is about 0.24%, [P] is about 0.10%, [S] is about 0.023%, and the temperature before dephosphorization is 1318 ° C. Hot metal 2t was charged.
[0061]
Next, 18 kg of iron ore in a lump shape (average particle size: 30 mm) was added on top of the hot metal, and then powdered (average particle size: 100 μm) with oxygen of 1.3 Nm 3 / min per hot metal t from the top blowing lance. The basicity (weight ratio: CaO / SiO 2 ) was adjusted to 2.0 by spraying 30 kg of a% CaO-10% Al 2 O 3 -20% Fe 2 O 3 mixture onto the hot metal for about 7 minutes.
[0062]
Moreover, 0.50 Nm 3 / min was blown into the bottom blowing tuyere during the treatment per molten iron t to stir the molten iron and slag.
The hot metal temperature at the end of dephosphorization was 1342 ° C., the basicity (weight ratio: CaO / SiO 2 ) 2.0, and the [P] concentration after treatment was 0.002%, [S] 0.024%, (T.Fe) 8%, (Al 2 O 3 ) 5%.
[0063]
After rinsing for 2 minutes, 4 kg of granular Mg (average particle size: 500 μm) per molten iron t was blown into the molten iron from the bottom blowing tuyere for 4 minutes. When rinsing was performed for 2 minutes, the slag forming was completely calmed down and the slag was almost solidified.
[0064]
The [S] concentration in the hot metal at the end of the metal Mg blowing was 0.003%, and the desulfurization rate was as high as 87%. In addition, there was no rephosphorization during the desulfurization treatment, and the [P] concentration in the hot metal was as low as 0.002%, and the target [P] concentration was 0.025% or less.
[0065]
(Invention Example 5)
In a test converter in which 30 kg of scrap was charged in advance, the components were [C] about 4.5%, [Si] about 0.10%, [P] about 0.10%, [S] about 0 .024%, 2t of hot metal having a temperature before dephosphorization of 1315 ° C. was charged.
[0066]
Next, after adding 24 kg of iron ore in a lump (average particle size: 30 mm) to the hot metal, 15 kg of CaO in powder form (average particle size: 100 μm) with 1.3 Nm 3 / min of oxygen per hot metal t from the top blowing lance. Was sprayed on the hot metal for about 7 minutes to adjust the basicity (weight ratio: CaO / SiO 2 ) to 3.5.
[0067]
Further, per hot metal t the Ar gas from the processing in the bottom tuyeres, and stirred pig iron and slag blown 0.50Nm 3 / min.
The hot metal temperature at the end of dephosphorization was 1342 ° C., the basicity (weight ratio: CaO / SiO 2 ) 3.4, and the [P] concentration after treatment was 0.020%, [S] 0.020%, (T.Fe) was 8%.
[0068]
In addition, slag almost solidified immediately after blowing.
Therefore, 4 kg of powdery (average particle diameter: 200 μm) CaO alone per hot metal t was blown into the hot metal from the bottom blowing tuyere for 4 minutes.
[0069]
The [S] concentration in the hot metal at the end of CaO blowing was 0.008%, and the desulfurization rate was as high as 67%. Moreover, there was no rephosphorization during the desulfurization treatment, and the [P] concentration in the hot metal was as low as 0.0020%, and the target [P] concentration could be 0.025% or less.
[0070]
【The invention's effect】
According to the present invention, (1) a desulfurization process can be performed continuously without discharging slag after a dephosphorization process using a converter or a converter-type hot metal pretreatment dedicated furnace. (2) The desulfurization rate can greatly exceed 50% of the conventional method.
Claims (3)
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| JP27315499A JP3736229B2 (en) | 1999-09-27 | 1999-09-27 | Hot metal processing method |
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| JP27315499A JP3736229B2 (en) | 1999-09-27 | 1999-09-27 | Hot metal processing method |
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| CN104060049B (en) * | 2013-09-16 | 2016-05-25 | 攀钢集团攀枝花钢铁研究院有限公司 | A kind of desulfurization dephosphorization agent and half steel be the method for desulfurization dephosphorization simultaneously |
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