JP3704853B2 - Hot metal preliminary refining method - Google Patents

Description

ここで、
［％Ｓｉ］：予備処理前の溶銑のＳｉ濃度
ｑｏ₂ ：酸素投入速度（Ｎｍ³ ／ｔ・min ）
ＱＯ₂ ：積算酸素投入量（Ｎｍ³ ／ｔ）
Ｂ：スラグ塩基度
を表す。
【００２１】
なお、上記Ｂ（スラグ塩基度）は、一般には、下記（３）式のように表される。

ここで、
Ｗ_slag（ＣａＯ）：予備精錬前のスラグ中のＣａＯ（kg／ｔ）
Ｗ_slag（ＳｉＯ₂ ）：予備精錬前のスラグ中のＳｉＯ₂ （kg／ｔ）
Ｗ_flux（ＣａＯ）：投入する予備処理剤中のＣａＯ（kg／ｔ）
Ｗ_flux（ＳｉＯ₂ ）：投入する予備処理剤中のＳｉＯ₂ （kg／ｔ）
ＷΔＳｉ：溶鋼中のＳｉ酸化によるＳｉＯ₂ 生成量（kg／ｔ）
を表す。
【００２２】
上述のように、スロッピングの発生臨界の収めるように酸素投入量を制御すればよい。
その条件を求めたところ、図６の結果が得られ、上記（２）式を満足すれば、発生臨界を越えないことを分かった。ここで、脱Ｓｉ外酸素投入速度は、投入酸素から既Ｓｉに使用した酸素を除いたものでＣＯ発生速度に比例するものと考えられる。
【００２３】
但し、実際の操業では、完全にスロッピング発生を抑えることができないが、石灰石化合物及びコークスのうちの少なくとも一方をスラグに添加しつつ予備精錬処理を行うことで、確実にスロッピング更にはスラグフォーミングを抑制しつつ連続的に予備精錬処理が可能となる。
【００２４】
なお、連続的又は断続的に石灰石化合物及びコークスのうちの少なくとも一方をスラグに添加しつつ行うものであるが、発生するスロッピングは従来よりも小さいために使用量も少なく、このことは、従来のような大量の炭材投入に起因するスラグによる脱燐反応の低下も抑えることができる。しかも、連続的又は断続的に石灰石化合物及びコークスのうちの少なくとも一方をスラグに添加するので、スラグフォーミングの抑制をしながらの予備精錬処理を自動化することも可能となる。
【００２５】
なお、上記石灰石化合物とは、例えば、ＣａＣＯ₃ 等である。
次に、上記式の妥当性について説明する。
溶銑のＳｉ濃度の時間変化については、次のように推定できる。
【００２６】
即ち、脱珪反応が一次反応であるとすると、脱珪速度式は、次式で表される。
ｄ［Ｓｉ］／ｄξ ＝−α・［Ｓｉ］
ここで、ξは、酸素原単位である。
【００２７】
この式を積分すると、
［Ｓｉ］＝［Ｓｉ］₀ ・ｅｘｐ（−αξ）が得られる。
ここで、
［Ｓｉ］₀ ：処理前のＳｉ濃度（％）
［Ｓｉ］ ：酸素投入量の添加後のＳｉ濃度（％）
また、脱燐処理中の途中サンプリングを行うことで、上記α≒０．４ｔ／Ｎｍ³ という値が得られた。
【００２８】
従って、脱燐処理中の溶銑中のＳｉの濃度推移は、次のように表される。
［Ｓｉ］＝［Ｓｉ］₀ ・ｅｘｐ（−０．４・ξ） ・・・（４）
の難易を求めて見たところ、図４に示すような結果を得た。
【００２９】
（４）式から、投入酸素量のうち、脱Ｓｉに消費される酸素量の割合は計算でき、その値は、
３２０×〔％Ｓｉ〕（％） ・・・（６）
ここで、〔％Ｓｉ〕は、処理中のＳｉ濃度（％）
これにより、脱Ｓｉ外酸素投入速度は、
ｑｏ₂ （１−３．２〔％Ｓｉ〕） （Ｎｍ³ ／ｔ・分）・・・（７）
ここで、ｑｏ₂ ：酸素投入速度（Ｎｍ³ ／ｔ・分）
で表される。
【００３０】
また、〔％Ｓｉ〕は、上記（４）式のとおり、
［％Ｓｉ］＝［％Ｓｉ］₀ ・ｅｘｐ（−０．４・ξ） ・・・（８）
ここで、
［％Ｓｉ］₀ ：処理前のＳｉ濃度（％）
ξ ：酸素投入積算量（Ｎｍ³ ／ｔ）
であるので、（７）式の脱Ｓｉ外酸素投入速度は、

で示されることになる。
【００３１】
一方、図６で示したように、脱Ｓｉ外酸素投入速度ｑｏ′₂ とスラグ塩基度Ｂの関係は、
ｑｏ′₂ ＞ ０．２・Ｂ
の領域では、スロッピングが発生しており、この領域に入らない条件で酸素投入速度を決定すればよいことが確認され、（２）式が妥当であると考えられた。
【００３２】
【発明の実施の形態】
次に、本発明の実施の形態を図面を参照しつつ説明する。
まず、構成を説明すると、図１に示すように、反応容器であるトピードカー１内に対象とする溶銑２が収容され、その溶銑２の上にスラグ３が形成されている。
【００３３】
また、トピードカー１内には、上側から予備処理剤用のランス４が挿入され、そのランス４の下端先端部を上記溶銑２内に浸漬している。このランス４は軸を斜めに配置されている。なお、ランス４の軸を斜めに設定するのは、ランス４から吹き出す予備処理剤によって生じた、流動する溶銑２の対流域を長くして予備精錬処理の反応の促進を図るためである。
【００３４】
その予備処理剤用のランス４の上端部は、予備処理剤供給装置５に連通し、該予備処理剤供給装置５から順次，供給される予備処理剤を溶銑２内に投入するようになっている。
【００３５】
また、上記トピードカー１内には、上記ランス４とは独立して作動する抑止剤用のランス６が挿入され、そのランス４の下端部である吹出し口は、スラグ面上方に所定の間隔を開けて設定されている。そのランス６は、上記予備処理剤用のランス４とは反対方向に軸を傾けて配置され、これによって、予備処理剤投入位置とは反対側に位置するスラグ３上面に対してスロッピング抑止剤を投入可能となっている。
【００３６】
その抑止剤用のランス６の上端部は、抑止剤供給装置７に連通し、抑止剤供給装置７から供給された予備処理剤を溶銑２内に投入可能となっている。
また、上記予備処理剤供給装置５は、図２に示すような構成となっている。即ち、酸化鉄粉又は生石灰粉をそれぞれ収容したリザーバタンク１０，１１を備え、各リザーバタンク１０，１１の出口は、それぞれロータリフィーダ１２，１３及び粉体供給遮断弁１４，１５を介して合流管１６に接続されることで合流し、その合流管１６を介して上記予備処理剤用のランス４に接続している。図２中、１７，１８はそれぞれ搬送ラインである。なお、上記各リザーバタンク１０，１１は、それぞれ粉体材料供給制御弁１９，２０を介して酸化鉄粉及び生石灰粉をそれぞれ収容した各粉体材料供給源２１，２２に接続されている。
【００３７】
また、上記各リザーバタンク１０，１１は、それぞれ加圧ライン２３，２４、バルブユニット２５，２６、及び加圧ガス供給ライン２７を介して加圧ガス供給源２８に接続されることで、所定圧力で加圧されている。この加圧の目的は、リザーバタンク１０，１１内の各粉体材料をロータリーフィーダ１２，１３に圧送して、粉体材料の切り出しを確実にするためである。
【００３８】
また、上記加圧ガス供給源２８からバルブユニット２５，２６に導入された加圧ガスは分岐し、バルブユニット２５，２６内の搬送ガス制御弁２５ａ，２６ａを介して搬送ガス供給ライン２９，３０に供給されている。その搬送ガス供給ライン２９，３０は、上記ロータリフィーダ１２，１３及び粉体供給遮断弁１４，１５の下流側に配置された粉体・ガス混合器３１，３２に接続されている。これによって、各ロータリフィーダ１２，１３及び粉体供給遮断弁１４，１５を介して供給された各粉体材料（酸化鉄粉及び生石灰粉）は、この粉体・ガス混合器３１，３２で上記搬送ガス供給ライン２９，３０から供給された加圧ガスとの混合することによって、流動状態になると共に、当該加圧ガス流によって上記合流管１６に搬送可能となっている。
【００３９】
ここで、上記バルブユニット２５，２６は、搬送用のガス流量及びガス圧を制御するものであって、上記バルブユニット２５，２６内の２５ｂ，２６ｂは圧力制御弁を、２５ｃ，２６ｃはガス流量制御弁を表している。
【００４０】
また、上記ロータリーフィーダ１２，１３や供給遮断弁１４，１５等の各アクチュエータは、それぞれコントローラ３３に接続され、該コントローラ３３からの信号によって作動が制御されている。
【００４１】
ここで、２５ｄ，２６ｄはガス流量センサ、３４，３５は各リザーバタンク１０，１１内の圧力を検出するタンク圧力センサ、３６は、合流管１６内の圧力を検出する合流部圧力センサ、３７はランス４に供給されるガスの背圧を検出する背圧センサであって、上記各センサは検出した検出信号をそれぞれ上記コントローラ３３に供給可能となっている。
【００４２】
また、各リザーバタンク１０，１１には、ロードセル等からなる粉体重量センサ３６，３７が取り付けられ、この粉体重量センサ３６，３７は、各リザーバタンク１０，１１内に収容された各粉体（酸化鉄粉や生石灰粉）の重量をそれぞれ検出して、その重量信号をコントローラ３３に供給可能となっている。
【００４３】
次に、上記抑止剤供給装置７について説明する。該抑止剤供給装置７は、上記予備処理剤供給装置５と同様な構成をしていて、図３に示すように、スロッピング抑止剤が抑止剤用リザーバタンク４０に収容され、その抑止材用リザーバタンク４０の出口がロータリフィーダ４１及び粉体供給遮断弁４２を介して上記抑止剤用ランス６に接続されている。また、上記リザーバタンク４０は、スロッピング抑止剤供給制御弁４３を介して各スロッピング抑止剤貯蔵源４４に接続されている。
【００４４】
ここで、上記スロッピング抑止剤には、コークスまたは石灰化合物、若しくはその混合物を使用する。
また、上記リザーバタンク４０は、それぞれ加圧ライン４５、バルブユニット４６、及び加圧ガス供給ライン４７を介して窒素ガス等からなる加圧ガス供給源４８に接続されることで、所定圧力で加圧されている。
【００４５】
また、上記加圧ガス供給源４８からバルブユニット４６に導入された加圧ガスは分岐し、バルブユニット４６内の搬送ガス制御弁４６ａを介して搬送ガス供給ライン４９に供給可能になっている。その搬送ガス供給ライン４９の下流側は、上記ロータリフィーダ４１及び粉体供給遮断弁４２の下流側に配置された粉体・ガス混合器５０に接続されている。
【００４６】
また、上記ロータリーフィーダ４１や供給遮断弁４２等の各アクチュエータは、それぞれコントローラ３３に接続され、該コントローラ３３からの信号によって制御されている。
【００４７】
ここで、４５ｂは圧力制御弁を、４６ｃはガス流量制御弁を、４６ｄはガス流量センサ、５１はリザーバタンク４０内の圧力を検出するタンク圧力センサであって、各センサは検出した検出信号をそれぞれ上記コントローラ３３に供給可能となっている。また、上記リザーバタンク４０には、ロードセル等からなる粉体重量センサ５２が取り付けられ、この粉体重量センサ５２は、リザーバタンク４０内に収容されたスロッピング抑止剤の重量を検出して、その重量信号をコントローラ３３に供給可能となっている。
【００４８】
コントローラ３３は、上記各センサからの信号を基に、予備処理剤供給装置５の各ロータリフィーダ１２，１３、粉体供給遮断弁１４，１５を作動して各リザーバタンク１０，１１から切り出される酸化鉄粉及び生石灰粉の各量を制御すると共に搬送ガスの流量及び圧力を制御することで、単位時間当たりに溶銑２内に投入される酸化鉄粉、生石灰粉の量、気体酸素量を制御する。
【００４９】
なお、各粉体重量センサ３６，３７からの信号に基づき実際の切り出し量をフィードバックしている。
このとき、上記各酸化鉄粉及び搬送気体中の酸素の単位時間当たりの投入量は、溶銑２への酸素投入量ととスラグ塩基度とを指標として、上記図４に示すように、スロッピング発生の発生し易い領域と発生しにくい領域との発生臨界Ａを予め求め、その発生臨界Ａを越えないような投入計画を、生石灰の投入量も含めて予め決定し、この投入計画に従うように上記各ロータリフィーダ１２，１３、粉体供給遮断弁１４，１５を作動する。
【００５０】
例えば、下式を満足するような酸素投入量となるように酸化鉄の投入速度を制御する。

ここで、
［％Ｓｉ］：予備処理前の溶銑のＳｉ濃度
ｑｏ₂ ：酸素投入速度（Ｎｍ³ ／ｔ・min ）
ＱＯ₂ ：積算酸素投入量（Ｎｍ³ ／ｔ）
Ｗ_slag（ＣａＯ）：予備精錬前のスラグ中のＣａＯ（kg／ｔ）
Ｗ_slag（ＳｉＯ₂ ）：予備精錬前のスラグ中のＳｉＯ₂ （kg／ｔ）
Ｗ_flux（ＣａＯ）：投入する予備処理剤中のＣａＯ（kg／ｔ）
Ｗ_flux（ＳｉＯ₂ ）：投入する予備処理剤中のＳｉＯ₂ （kg／ｔ）
ＷΔＳｉ：溶鋼中のＳｉ酸化によるＳｉＯ₂ 生成量（kg／ｔ）
を表す。
【００５１】
同時に、コントローラ３３は、抑止剤用の粉体供給遮断弁４２及び搬送ガス制御弁４６ａに作動信号を供給して、予備精錬中、連続的に所定量のスロッピング抑止剤をランス４からスラグ３表面に吹き付けるように制御する。
【００５２】
ここで、スロッピング抑止剤の吹出しは、連続的に吹き付けてもよいし、所定時間間隔毎に断続的に吹き付けるように設定しておいてもよい。
次に、上記装置の作動や効果などについて説明する。
【００５３】
上記構成の装置では、コントローラ３３による制御によって、ランス４を通して各酸化鉄粉、生石灰粉、搬送ガス量の各投入量が溶銑２内に投入されて、脱珪・脱燐等の予備精錬処理が行われる。
【００５４】
このとき、溶銑２内炭素が予備処理剤と反応してＣＯガスが発生し、そのガスによる気泡がスラグ３まで到達すると、スラグ３内に捕捉されてスロッピングを起こしスラグフォーミングを形成する。
【００５５】
しかし、本実施形態では、上述のように発生臨界Ａ内になるように酸素投入速度を制御しているので、スロッピング発生の回数や程度が大幅に抑制され、しかも、連続的又は断続的にスラグ３にスロッピング抑止剤を投入しているので、スロッピング発生が確実に抑えられる。
【００５６】
しかも、連続的又は断続的にスロッピング抑止剤を投入しているが、上述のように、スロッピング発生の回数や程度が大幅に抑制されているので、そのスロッピング抑止剤の使用量も少なくて済むと共に、スロッピング発生の有無とは関係なく添加しているので、スロッピング更にはフォーミングを抑制しながらの予備精錬処理を自動化することができる。
【００５７】
また、上記のようにスロッピング抑止剤の添加量も少なくて済むので、スロッピング抑止剤を大量に投入した際のスラグ３中のＦｅＯの還元によるスラグ３による脱燐反応の低下もなく、且つ予備処理剤の投入の一時的な停止もないので、スロッピング更にはフォーミングを抑制しつつ、従来よりも予備精錬の処理時間の促進を図ることができる。
【００５８】
また、上記実施の形態では、予備処理剤投入位置とは反対側のスラグ３に抑止剤を投入するようにしているが、これは、溶銑２の流動に伴ってスラグのスロッピング高さが一番高くなるのが予備処理剤投入位置とは反対側となることに鑑みてなされたものであるが、実際のスロッピング発生とは関係なく連続的又は断続的にスロッピング抑止剤を添加しているので、必ずも反対側位置でなくてもよい。また、抑止剤用のランス６を傾けているが、特に傾ける必要もない。
【００５９】
また、スロッピング抑止剤の添加は、スラグ上面に吹き付けることで行っているが、ランス６の先端部をスラグ内に浸漬させた状態で供給するようにしてもよい。
【００６０】
また、上記実施の形態では、実際のスロッピング発生とは関係なくスロッピング抑止剤を投入するようにしているが、実際にスロッピング発生若しくは発生のおそれをを検知したときのみスロッピング抑止剤を投入するようにしてもよい。
【００６１】
例えば、カメラ等でスラグ上面を監視したり、実際の予備処理剤の投入量の計画量からの変動をもとにスロッピング発生を推定して、スロッピング抑止剤を添加するようにしてもよい。但し、この場合には、スロッピング高さが必要以上に高くなるおそれはある。
【００６２】
また、スラグ上面にスロッピング抑止剤を添加するので、スロッピング抑止剤の投入はランス６を使用しない方法であってもよい。
【００６３】
【実施例】
実際に、２００ｔの溶銑をトピードカーに収容して、酸化鉄３５ｋｇ／ｔ、生石灰１２kg／ｔを、２kg／ｔ・min の速度で溶銑に投入して予備精錬処理を行ってみた。
【００６４】
図２は、その処理の際の、トピードカー１からスラグ３の溢れる危険性のあるほど大きさのスロッピングの発生頻度を示したものである。
比較例１は、スロッピングに対する処理を取らなかった場合であって、スロッピング発生頻度は９／１０となり、予備処理剤の吹き込みを停止せざるを得なった。
【００６５】
また、引用例２は、フォーミングが生じたところでコークス（スロッピング抑止剤）をスラグ３に吹き付けた場合であって、酸素投入速度つまり、酸化鉄等の投入速度を増加しすぎると、コークスを投入してもスロッピングが収まらない場合があり、スロッピング頻度が３／１０であった。
【００６６】
これに対して、上述のように本発明の予備精錬方法を適用した場合には、スロッピングの発生は無かった。つまり、連続して予備精錬処理ができた。
しかも、スロッピング抑止剤であるコークスの使用量も、引用例２に比べて少なくて済んだ。
【００６７】
また、本発明に基づく予備精錬処理では、石灰化合物であるＣａＣＯ₃ 粉をスロッピング抑止剤としてスラグ表面に連続的に吹き付けることで、酸化鉄の吹き込み速度を平均３８５kg／min でもスロッピングなして処理できたことも確認した。
【００６８】
この場合、脱燐処理時間は２５分で、Ｓｉ濃度が０．２０％から０．０１％に、Ｐ濃度が、０．１６６％から０．０２０％となったことも確認された。
さらに、コークス及びＣａＣＯ₃ 粉ともに脱燐効率への悪影響も無かった。
【００６９】
これによって、フォーミング抑止のためのコストを抑えつつ予備精錬処理の高速化が図られる。
【００７０】
【発明の効果】
以上説明してきたように、本発明の溶銑の予備精錬方法では、溶銑への酸素投入量を調整することで、スロッピング抑止剤の使用量を抑えつつ、連続した予備精錬を可能とするという効果がある。
【００７１】
しかも、スロッピングの発生臨界を求めているので、スラグフォーミングを抑えた状態で且つ適正な時間で脱珪等の予備精錬処理を行うことができる。
このとき、請求項２又は請求項３に記載の発明を採用すると、確実にスロッピング更にはフォーミング形成を抑えつつ、予備精錬処理の自動化を図ることができるという効果がある。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る溶銑の予備精錬処理の概略構成図である。
【図２】本発明の実施の形態に係る予備処理剤供給装置を示す構成図である。
【図３】本発明の実施の形態に係る抑止剤供給装置を示す構成図である。
【図４】酸素投入量とスラグ塩基度を指標としたスロッピング発生条件及び発生臨界を説明するための図である。
【図５】本発明に基づく処理実績を説明するための図である。
【図６】スロッピング抑止剤を投入しつつ脱珪・脱燐処理を行う場合の酸素投入速度と塩基度を指標としたスロッピング発生条件及び発生臨界を説明するための図である。
【符号の説明】
Ａ 発生臨界
１ トピードカー
２ 溶銑
３ スラグ
４ 予備処理剤用のランス
５ 予備処理剤供給装置
６ 抑止剤用のランス
７ 抑止剤供給用装置
１０，１１ リザーバタンク
１２，１３ ロータリフィーダ
２５ａ，２６ａ 搬送ガス制御弁
２８ 加圧ガス供給源
３６，３７ 粉体重量センサ
３３ コントローラ
４０ リザーバタンク
４１ ロータリフィーダ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a preliminary smelting process such as desiliconization of hot metal, and more particularly to a preliminary smelting method of hot metal in which preliminary smelting is performed while suppressing slag forming that occurs during the preliminary smelting of hot metal.
[0002]
[Prior art]
When performing preliminary refining treatment such as desiliconization, dephosphorization, desulfurization of hot metal in a reaction vessel such as a topped car, a lance is immersed in the hot metal in the reaction vessel, and oxygen gas and solid oxide are introduced from the tip of the lance. (For example, iron oxide) and pretreatment agents such as lime compounds are blown in to perform treatment such as desiliconization of hot metal. During this treatment, for example, if a large amount of solid oxide is charged at once, that is, if the oxygen input rate is high, the slag in the container forms due to CO gas generated suddenly by decarburization reaction, etc. If the state is continued, slopping will occur suddenly, and a part of the slag will overflow from the reaction vessel.
[0003]
This not only leads to a decrease in the iron yield, but also temporarily disables the operation due to a slag overflowing to fill the track for the topped car.
[0004]
For this reason, generally, when slapping exceeding a predetermined value occurs, the blowing speed (feeding speed) of the pretreatment agent as an oxygen source is reduced, or in some cases, the blowing of the pretreatment agent is temporarily stopped. Take measures to wait for the slipping to settle naturally.
[0005]
However, this method is accompanied by an extension of the pre-refining treatment time, and a reduction in productivity is inevitable.
On the other hand, a method for preventing slopping without reducing the processing speed of preliminary refining has been proposed.
[0006]
For example, as described in JP-A-2-290911, a gas such as nitrogen gas is introduced from the side surface of the lance into which the pretreatment agent is introduced in the vicinity of the interface with the hot metal with the slag floating on the hot metal. By constantly spraying, the slag is moved in the direction of the wall surface to form an opening that exposes the hot metal surface, thereby dissipating the generated CO gas into the air and suppressing the generation of slopping and slag foaming. Trying to.
[0007]
Alternatively, as described in Japanese Patent Application Laid-Open No. 5-125424, a lance for introducing a carbon material as a slopping inhibitor is installed in the vicinity of the lance for introducing the pretreatment agent, and a monitoring camera is used. There is also proposed a method of suppressing the slag forming by monitoring the actual slapping height of the slag and introducing the above-mentioned charcoal material when the height exceeds a predetermined height.
[0008]
[Problems to be solved by the invention]
However, the suppression method in which the gas is blown to form the opening portion is not so effective even if it is actually performed, and as a result, it is not possible to prevent the pretreatment time from being extended.
[0009]
In addition, the method of spraying carbonaceous materials such as coke into the slag only when the occurrence of the slopping is detected and the slopping height is equal to or higher than the predetermined level is recognized, but the spraying is stopped. In many cases, slopping is caused again, and the amount of carbon material sprayed is increased, resulting in an increase in cost.
[0010]
In addition, if a large amount of carbon is used to suppress forming, the reduction of FeO in the slag proceeds, the dephosphorization reaction due to the slag decreases, and as a result, the desiliconization / dephosphorization processing time increases. Arise.
[0011]
An object of the present invention is to provide a hot metal pre-smelting method capable of improving the processing efficiency of pre-smelting while suppressing the occurrence of slugging of slag at low cost.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the hot metal preliminary refining method according to claim 1 of the present invention suppresses slag foaming while preliminarily containing a solid oxide, a lime compound, gaseous oxygen or the like in the hot metal in the reaction vessel. In the hot metal preliminary refining method, the treatment agent is added to perform preliminary refining such as desiliconization and dephosphorization of hot metal.
Based on the slag slop generation conditions obtained using the solid oxide and gaseous oxygen input to the hot metal and the slag basicity as indicators, the criticality of the region where slopping is likely to occur and the region where it is difficult to occur is determined. The oxygen input amount per time is controlled so as to be within the determined generation criticality.
[0013]
The present inventors obtained the present invention from the following examination.
That is, slag forming is less likely to occur as the slag basicity increases. Further, it is considered that the generation rate of CO gas that causes forming increases as the oxygen removal rate outside oxygen removal (oxygen addition rate for desiliconization treatment) increases.
[0014]
From this point of view, when the slopping generation conditions were arranged with the oxygen removal rate outside desiliconization and the slag basicity as indices, the results shown in FIG. 4 were obtained.
In FIG. 4, A is the criticality for occurrence of slopping, and it has been found that the slopping phenomenon is likely to occur in the hatched range exceeding this criticality A.
[0015]
Therefore, if the amount of oxygen input is controlled so as not to exceed the generation critical A based on the slopping generation conditions, continuous pretreatment of the hot metal can be performed while suppressing slopping and further slag forming.
[0016]
In addition, since the occurrence criticality A of slopping is known, it is not necessary to lower the operation efficiency by setting the vicinity of the occurrence critical A and controlling the input amounts of solid oxide and gaseous oxygen.
[0017]
Here, the basicity of the slag is expressed as (lime compound) / SiO ₂ , but the treated SiO ₂ is mainly a reaction product of Si and solid oxide in the hot metal, It can be controlled by controlling the amount of solid oxide input according to the reaction rate.
[0018]
From the above, it is possible to keep within the generation critical A by adjusting the amount of oxygen input per hour by solid oxide and gaseous oxygen.
Further, the invention according to claim 2 introduces a pretreatment agent such as a solid oxide, a lime compound, and gaseous oxygen into the hot metal in the reaction vessel while suppressing slag forming, thereby desiliconizing and dephosphorizing the hot metal. In the hot metal preliminary refining method,
Slipping based on the slag slapping generation condition required by adding the solid oxide and gaseous oxygen to the molten iron and the slag basicity as an index while adding at least one of the limestone compound and coke to the slag It is characterized in that the generation criticality of the region where the occurrence of hydrogen is easily generated and the region where it is difficult to generate is obtained, and the oxygen input amount per time is controlled so as to fall within the obtained generation criticality.
[0019]
According to this invention, in addition to the effect of the invention of claim 1 above, since it is carried out while adding at least one of the limestone compound and coke as the slopping inhibitor, the fluctuation of the actual pretreatment agent input amount Even if there is, slopping is surely suppressed.
[0020]
In addition, since it is thought that the degree of forming is lower and the number of times is lower than that in the conventional case, the addition of the limestone compound or coke may be reduced even if it is continuously added. Next, the invention according to claim 3 introduces a pretreatment agent such as a solid oxide, a lime compound, and gaseous oxygen into the hot metal in the reaction vessel while suppressing slag forming, thereby desiliconizing and removing the hot metal. While adding at least one of the limestone compound and coke to the slag in the hot metal preliminary refining method for performing the preliminary refining of phosphorus or the like, the amount of oxygen input to the hot metal by the solid oxide and gaseous oxygen is the following (2) It is a hot metal preliminary refining method characterized in that preliminary refining is performed by setting a range satisfying the equation.

here,
[% Si]: Si concentration in hot metal before preliminary treatment qo ₂ : Oxygen input rate (Nm ³ / t · min)
QO ₂ : Accumulated oxygen input (Nm ³ / t)
B: Represents slag basicity.
[0021]
The B (slag basicity) is generally expressed as the following formula (3).

here,
W _slag (CaO): CaO (kg / t) in slag before preliminary refining
_{W slag (SiO 2): SiO} 2 in the previous spare refining slag (kg / t)
W _flux (CaO): CaO (kg / t) in the pretreatment agent to be charged
W _flux (SiO ₂ ): SiO ₂ (kg / t) in the pretreatment agent to be charged
WΔSi: Amount of SiO ₂ generated by Si oxidation in molten steel (kg / t)
Represents.
[0022]
As described above, the amount of oxygen input may be controlled so that the occurrence criticality of slopping is maintained.
When the conditions were obtained, the result of FIG. 6 was obtained, and it was found that if the above equation (2) was satisfied, the generation criticality was not exceeded. Here, the oxygen removal rate outside de-Si is obtained by subtracting the oxygen used for the existing Si from the introduced oxygen, and is considered to be proportional to the CO generation rate.
[0023]
However, in actual operation, the occurrence of slopping cannot be completely suppressed. However, by performing the preliminary refining treatment while adding at least one of the limestone compound and coke to the slag, the slopping and the slag forming are reliably performed. The preliminary refining process can be continuously performed while suppressing the above.
[0024]
In addition, it is performed while continuously or intermittently adding at least one of the limestone compound and coke to the slag, but since the generated slopping is smaller than the conventional one, the amount used is also small. It is also possible to suppress a decrease in the dephosphorization reaction due to slag caused by a large amount of carbon material input. Moreover, since at least one of the limestone compound and coke is continuously or intermittently added to the slag, it is possible to automate the preliminary refining process while suppressing the slag forming.
[0025]
Note that the above-mentioned limestone compounds such as CaCO ₃ or the like.
Next, the validity of the above formula will be described.
About the time change of hot metal Si concentration, it can estimate as follows.
[0026]
That is, assuming that the desiliconization reaction is a primary reaction, the desiliconization rate equation is expressed by the following equation.
d [Si] / dξ = −α · [Si]
Here, ξ is an oxygen basic unit.
[0027]
When this equation is integrated,
[Si] = [Si] ₀ · exp (−αξ) is obtained.
here,
[Si] ₀ : Si concentration before treatment (%)
[Si]: Si concentration after addition of oxygen input (%)
Moreover, the value of α≈0.4 t / Nm ³ was obtained by performing sampling during the dephosphorization process.
[0028]
Therefore, the transition of the Si concentration in the hot metal during the dephosphorization process is expressed as follows.
[Si] = [Si] ₀ · exp (−0.4 · ξ) (4)
As a result, the results as shown in FIG. 4 were obtained.
[0029]
From the equation (4), the ratio of the amount of oxygen consumed for de-Si out of the input oxygen amount can be calculated, and the value is
320 x [% Si] (%) (6)
Here, [% Si] is the Si concentration during processing (%)
As a result, the oxygen removal rate outside de-Si is
qo ₂ (1-3.2 [% Si]) (Nm ³ / t · min) (7)
Where qo ₂ : oxygen input rate (Nm ³ / t · min)
It is represented by
[0030]
In addition, [% Si] is as shown in the above equation (4).
[% Si] = [% Si] ₀ · exp (−0.4 · ξ) (8)
here,
[% Si] ₀ : Si concentration before treatment (%)
ξ: Oxygen input integrated amount (Nm ³ / t)
Therefore, the de-Si-external oxygen input rate of the equation (7) is

Will be shown.
[0031]
On the other hand, as shown in FIG. 6, the relationship between the de-Si-external oxygen input rate qo ′ ₂ and the slag basicity B is
qo ′ ₂ > 0.2 · B
In this region, slopping occurred, and it was confirmed that the oxygen input rate should be determined under conditions that do not enter this region, and Equation (2) was considered to be appropriate.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
First, the structure will be described. As shown in FIG. 1, a target hot metal 2 is accommodated in a topped car 1 as a reaction vessel, and a slag 3 is formed on the hot metal 2.
[0033]
Further, a lance 4 for a pretreatment agent is inserted into the topped car 1 from the upper side, and the tip of the lower end of the lance 4 is immersed in the hot metal 2. The lance 4 is arranged with its axis inclined. In addition, the axis | shaft of the lance 4 is set diagonally in order to aim at the acceleration | stimulation of the reaction of a preliminary refining process by lengthening the convection area | region of the flowing hot metal 2 which arises with the pretreatment agent which blows off from the lance 4. FIG.
[0034]
The upper end portion of the lance 4 for the pretreatment agent communicates with the pretreatment agent supply device 5, and the pretreatment agent supplied sequentially from the pretreatment agent supply device 5 is put into the hot metal 2. Yes.
[0035]
A lance 6 for a deterrent that operates independently of the lance 4 is inserted into the topped car 1, and a blow-out port that is a lower end portion of the lance 4 has a predetermined gap above the slag surface. Is set. The lance 6 is disposed with an axis inclined in the opposite direction to the lance 4 for the pretreatment agent, and thereby, the slopping inhibitor with respect to the upper surface of the slag 3 located on the side opposite to the pretreatment agent charging position. Can be introduced.
[0036]
The upper end portion of the lance 6 for the inhibitor communicates with the inhibitor supply device 7 so that the pretreatment agent supplied from the inhibitor supply device 7 can be put into the hot metal 2.
Further, the pretreatment agent supply device 5 has a configuration as shown in FIG. That is, reservoir tanks 10 and 11 each containing iron oxide powder or quicklime powder are provided, and the outlets of the reservoir tanks 10 and 11 are joined pipes via rotary feeders 12 and 13 and powder supply shut-off valves 14 and 15, respectively. 16 is connected to the lance 4 for the pretreatment agent via the merging pipe 16. In FIG. 2, 17 and 18 are conveyance lines, respectively. The reservoir tanks 10 and 11 are connected to powder material supply sources 21 and 22 respectively containing iron oxide powder and quicklime powder via powder material supply control valves 19 and 20, respectively.
[0037]
The reservoir tanks 10 and 11 are connected to the pressurized gas supply source 28 via the pressurized lines 23 and 24, the valve units 25 and 26, and the pressurized gas supply line 27, respectively. Is pressurized. The purpose of the pressurization is to ensure that the powder material in the reservoir tanks 10 and 11 is pumped to the rotary feeders 12 and 13 to cut out the powder material.
[0038]
The pressurized gas introduced from the pressurized gas supply source 28 to the valve units 25 and 26 branches, and the carrier gas supply lines 29 and 30 are passed through the carrier gas control valves 25a and 26a in the valve units 25 and 26. Has been supplied to. The carrier gas supply lines 29 and 30 are connected to powder / gas mixers 31 and 32 arranged on the downstream side of the rotary feeders 12 and 13 and the powder supply cutoff valves 14 and 15. As a result, the powder materials (iron oxide powder and quicklime powder) supplied via the rotary feeders 12 and 13 and the powder supply shut-off valves 14 and 15 are transferred to the powder / gas mixers 31 and 32, respectively. By mixing with the pressurized gas supplied from the carrier gas supply lines 29 and 30, the fluidized state is obtained, and the fluid can be conveyed to the junction pipe 16 by the pressurized gas flow.
[0039]
Here, the valve units 25 and 26 control the gas flow rate and gas pressure for conveyance. 25b and 26b in the valve units 25 and 26 are pressure control valves, and 25c and 26c are gas flow rates. Represents a control valve.
[0040]
The actuators such as the rotary feeders 12 and 13 and the supply shut-off valves 14 and 15 are connected to the controller 33 and their operations are controlled by signals from the controller 33.
[0041]
Here, 25d and 26d are gas flow sensors, 34 and 35 are tank pressure sensors for detecting the pressure in the reservoir tanks 10 and 11, 36 is a junction pressure sensor for detecting the pressure in the junction pipe 16, and 37 is A back pressure sensor for detecting the back pressure of the gas supplied to the lance 4, and each sensor can supply a detected signal to the controller 33.
[0042]
Further, powder weight sensors 36 and 37 made of load cells and the like are attached to the reservoir tanks 10 and 11, respectively. The powder weight sensors 36 and 37 are powders accommodated in the reservoir tanks 10 and 11, respectively. It is possible to detect the weight of each of (iron oxide powder and quicklime powder) and supply the weight signal to the controller 33.
[0043]
Next, the inhibitor supply device 7 will be described. The inhibitor supply device 7 has the same configuration as the pretreatment agent supply device 5, and as shown in FIG. 3, the slopping inhibitor is accommodated in a reservoir tank 40 for the inhibitor, and the inhibitor The outlet of the reservoir tank 40 is connected to the inhibitor lance 6 via a rotary feeder 41 and a powder supply shutoff valve 42. The reservoir tank 40 is connected to each of the slopping inhibitor storage sources 44 via the slopping inhibitor supply control valve 43.
[0044]
Here, coke, a lime compound, or a mixture thereof is used as the above-mentioned slopping inhibitor.
Further, the reservoir tank 40 is connected to a pressurized gas supply source 48 made of nitrogen gas or the like via a pressurized line 45, a valve unit 46, and a pressurized gas supply line 47, respectively. It is pressed.
[0045]
The pressurized gas introduced from the pressurized gas supply source 48 into the valve unit 46 branches and can be supplied to the carrier gas supply line 49 via the carrier gas control valve 46 a in the valve unit 46. The downstream side of the carrier gas supply line 49 is connected to a powder / gas mixer 50 arranged on the downstream side of the rotary feeder 41 and the powder supply cutoff valve 42.
[0046]
The actuators such as the rotary feeder 41 and the supply shutoff valve 42 are connected to the controller 33 and controlled by signals from the controller 33.
[0047]
Here, 45b is a pressure control valve, 46c is a gas flow rate control valve, 46d is a gas flow rate sensor, 51 is a tank pressure sensor that detects the pressure in the reservoir tank 40, and each sensor detects a detected signal. Each can be supplied to the controller 33. The reservoir tank 40 is provided with a powder weight sensor 52 composed of a load cell or the like. The powder weight sensor 52 detects the weight of the slopping inhibitor contained in the reservoir tank 40 and A weight signal can be supplied to the controller 33.
[0048]
The controller 33 operates the rotary feeders 12 and 13 and the powder supply shut-off valves 14 and 15 of the pretreatment agent supply device 5 based on the signals from the sensors, and the oxidation is cut out from the reservoir tanks 10 and 11. By controlling each amount of iron powder and quicklime powder, and controlling the flow rate and pressure of the carrier gas, the amount of iron oxide powder, quicklime powder, and gaseous oxygen amount to be fed into the molten iron 2 per unit time are controlled. .
[0049]
The actual cutout amount is fed back based on signals from the powder weight sensors 36 and 37.
At this time, the input amount per unit time of each iron oxide powder and oxygen in the carrier gas is slopping as shown in FIG. 4 using the oxygen input amount to the hot metal 2 and the slag basicity as indexes. The generation critical A of the region where the occurrence is likely to occur and the region where the generation is difficult to occur is determined in advance, and a charging plan that does not exceed the criticality A is determined in advance including the amount of quick lime input, and this charging plan is followed. The rotary feeders 12 and 13 and the powder supply cutoff valves 14 and 15 are operated.
[0050]
For example, the input rate of iron oxide is controlled so that the amount of oxygen input satisfies the following formula.

here,
[% Si]: Si concentration in hot metal before preliminary treatment qo ₂ : Oxygen input rate (Nm ³ / t · min)
QO ₂ : Accumulated oxygen input (Nm ³ / t)
W _slag (CaO): CaO (kg / t) in slag before preliminary refining
_{W slag (SiO 2): SiO} 2 in the previous spare refining slag (kg / t)
W _flux (CaO): CaO (kg / t) in the pretreatment agent to be charged
W _flux (SiO ₂ ): SiO ₂ (kg / t) in the pretreatment agent to be charged
WΔSi: Amount of SiO ₂ generated by Si oxidation in molten steel (kg / t)
Represents.
[0051]
At the same time, the controller 33 supplies an operation signal to the powder supply shutoff valve 42 and the carrier gas control valve 46a for the deterrent, and continuously supplies a predetermined amount of the slopping deterrent from the lance 4 to the slag 3 during the preliminary refining. Control to spray on the surface.
[0052]
Here, the blowing of the slopping inhibitor may be continuously sprayed or may be set to be intermittently sprayed at predetermined time intervals.
Next, the operation and effects of the above apparatus will be described.
[0053]
In the apparatus having the above-described configuration, the iron oxide powder, quicklime powder, and the amount of carrier gas are introduced into the hot metal 2 through the lance 4 under the control of the controller 33, and preliminary refining processes such as desiliconization and dephosphorization are performed. Done.
[0054]
At this time, carbon in the hot metal 2 reacts with the pretreatment agent to generate CO gas, and when bubbles by the gas reach the slag 3, they are trapped in the slag 3 and cause slopping to form slag forming.
[0055]
However, in this embodiment, since the oxygen input speed is controlled so as to be within the generation critical A as described above, the number and degree of the occurrence of slopping is greatly suppressed, and continuously or intermittently. Since a slopping inhibitor is introduced into the slag 3, the occurrence of slopping can be reliably suppressed.
[0056]
Moreover, although the slipping inhibitor is continuously or intermittently added, as described above, the number and degree of the occurrence of the slopping is greatly suppressed, so that the amount of the slipping inhibitor used is small. In addition, since the addition is performed regardless of the occurrence of slopping, the preliminary refining process can be automated while suppressing the slopping and the forming.
[0057]
In addition, since the amount of addition of the slopping inhibitor may be small as described above, there is no decrease in the dephosphorization reaction by the slag 3 due to the reduction of FeO in the slag 3 when a large amount of the slopping inhibitor is added, and Since there is no temporary stop of the introduction of the pretreatment agent, it is possible to promote the preliminary refining treatment time as compared with the prior art while suppressing slapping and forming.
[0058]
Further, in the above embodiment, the deterrent agent is introduced into the slag 3 on the side opposite to the pretreatment agent introduction position. This is because the slopping height of the slag is the same as the hot metal 2 flows. It is made in view of the fact that the highest point is on the side opposite to the pretreatment agent charging position, but the slopping inhibitor is added continuously or intermittently regardless of the actual occurrence of slopping. Therefore, it does not necessarily have to be in the opposite position. Further, although the lance 6 for the deterrent is tilted, it is not necessary to tilt it.
[0059]
Further, although the slopping inhibitor is added by spraying on the upper surface of the slag, it may be supplied in a state where the tip of the lance 6 is immersed in the slag.
[0060]
Further, in the above embodiment, the slipping inhibitor is introduced regardless of the actual occurrence of slopping. However, the slipping inhibitor is only applied when the occurrence of the occurrence of slipping is actually detected. You may make it throw in.
[0061]
For example, the top surface of the slag may be monitored with a camera or the like, or the occurrence of slopping may be estimated based on the variation of the actual amount of pretreatment agent input from the planned amount, and a slopping inhibitor may be added. . However, in this case, the slapping height may be higher than necessary.
[0062]
Further, since the slopping inhibitor is added to the upper surface of the slag, the slopping inhibitor may be charged without using the lance 6.
[0063]
【Example】
Actually, 200 t of hot metal was put in a topped car, and 35 kg / t of iron oxide and 12 kg / t of quick lime were put into the hot metal at a rate of 2 kg / t · min, and preliminary refining treatment was performed.
[0064]
FIG. 2 shows the frequency of occurrence of sloping so large that there is a risk of overflow of the slag 3 from the topped car 1 during the processing.
Comparative Example 1 was a case where the treatment for the slopping was not performed, and the occurrence frequency of the slopping was 9/10, and the blowing of the pretreatment agent had to be stopped.
[0065]
Citation 2 is a case where coke (sloping deterrent) is sprayed on the slag 3 when forming occurs, and if the oxygen input rate, that is, the input rate of iron oxide or the like is increased too much, coke is input. Even in this case, the slopping may not be achieved, and the slapping frequency was 3/10.
[0066]
On the other hand, when the preliminary refining method of the present invention was applied as described above, there was no occurrence of slopping. That is, the preliminary refining process was continuously performed.
In addition, the amount of coke used as a slopping inhibitor is less than that of the second example.
[0067]
Further, in the preliminary refining treatment based on the present invention, the CaCO ₃ powder, which is a lime compound, is continuously blown onto the slag surface as a slopping inhibitor, so that the iron oxide blowing speed is reduced even at an average of 385 kg / min. I also confirmed that it was possible.
[0068]
In this case, it was also confirmed that the dephosphorization time was 25 minutes, the Si concentration was changed from 0.20% to 0.01%, and the P concentration was changed from 0.166% to 0.020%.
Furthermore, neither coke nor CaCO ₃ powder had any adverse effect on the dephosphorization efficiency.
[0069]
As a result, the speed of the preliminary refining process can be increased while suppressing the cost for suppressing forming.
[0070]
【The invention's effect】
As described above, in the hot metal preliminary refining method of the present invention, by adjusting the amount of oxygen input to the hot metal, the effect of enabling continuous preliminary refining while suppressing the amount of use of the slopping inhibitor. There is.
[0071]
In addition, since the occurrence criticality of slopping is required, preliminary refining treatment such as desiliconization can be performed in an appropriate time with slag forming suppressed.
At this time, if the invention according to claim 2 or claim 3 is adopted, there is an effect that the preliminary refining process can be automated while reliably suppressing the slapping and the forming.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a hot metal preliminary refining process according to an embodiment of the present invention.
FIG. 2 is a configuration diagram showing a pretreatment agent supply apparatus according to an embodiment of the present invention.
FIG. 3 is a configuration diagram showing a deterrent supply device according to an embodiment of the present invention.
FIG. 4 is a diagram for explaining slopping generation conditions and generation criticality using oxygen input and slag basicity as indices.
FIG. 5 is a diagram for explaining processing results based on the present invention;
FIG. 6 is a diagram for explaining slopping generation conditions and generation criticality using oxygen input speed and basicity as indexes when performing desiliconization / dephosphorization processing while adding a slopping inhibitor.
[Explanation of symbols]
A generation criticality 1 topped car 2 hot metal 3 slag 4 lance for pretreatment agent 5 pretreatment agent supply device 6 lance for deterrent agent 7 deterrent agent supply device 10, 11 reservoir tank 12, 13 rotary feeders 25a, 26a carrier gas control Valve 28 Pressurized gas supply source 36, 37 Powder weight sensor 33 Controller 40 Reservoir tank 41 Rotary feeder

Claims (3)

Preliminary refining method for hot metal in which pretreatment such as desiliconization and dephosphorization of hot metal is performed by introducing a pretreatment agent such as solid oxide, lime compound, and gaseous oxygen into the hot metal in the reaction vessel while suppressing slag forming In
Based on the slag slumping conditions obtained by using the amount of oxygen introduced into the hot metal and the oxygen content of gaseous oxygen and the slag basicity as indices, the criticality of the region where slopping is likely to occur and the region where it is difficult to occur is determined. A method for preliminary refining of hot metal, characterized in that the amount of oxygen input per hour is controlled to be within the determined generation criticality. Preliminary refining method for hot metal in which pretreatment such as desiliconization and dephosphorization of hot metal is performed by introducing a pretreatment agent such as solid oxide, lime compound, and gaseous oxygen into the hot metal in the reaction vessel while suppressing slag forming In
Slipping based on the slag slop generation conditions required by adding the solid oxide and gaseous oxygen to the molten iron and the slag basicity as an index while adding at least one of the limestone compound and coke to the slag A hot metal preliminary smelting method characterized in that the criticality of occurrence of a region where gas is easily generated and the region where it is difficult to generate are obtained, and the amount of oxygen input per hour is controlled to fall within the obtained criticality of occurrence. Preliminary refining method for hot metal in which pretreatment such as desiliconization and dephosphorization of hot metal is performed by introducing a pretreatment agent such as solid oxide, lime compound, and gaseous oxygen into the hot metal in the reaction vessel while suppressing slag forming In
While adding at least one of the limestone compound and coke to the slag, the amount of oxygen input to the molten iron by the solid oxide and gaseous oxygen is set within a range satisfying the following formula (1), and preliminary refining is performed. A method for preliminary refining of hot metal characterized by the above.

here,
[% Si]: Si concentration in hot metal before preliminary treatment qo ₂ : Oxygen input rate (Nm ³ / t · min)
QO ₂ : Accumulated oxygen input (Nm ³ / t)
B: Represents slag basicity.

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