JP4050893B2

JP4050893B2 - Method and apparatus for evaluating soot level in blast furnace

Info

Publication number: JP4050893B2
Application number: JP2001356906A
Authority: JP
Inventors: 雅人杉浦; 和也国友; 豊藤原; 秀隆小南; 毅一郎中村
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2001-11-22
Filing date: 2001-11-22
Publication date: 2008-02-20
Anticipated expiration: 2021-11-22
Also published as: JP2003155507A

Description

【０００１】
【発明の属する技術分野】
本発明は、高炉内の銑滓レベル評価方法及び評価装置に関するものである。
【０００２】
【従来の技術】
高炉炉内において、原料となる鉄鉱石はコークスとともに炉頂から炉体内に供給され、羽口から炉体内に圧送される熱風によって温度が上昇し、コークスによって還元されて溶銑となる。溶銑は炉底部に貯留し、溶銑の上に接して溶滓（スラグ）が貯留する。高炉炉内に貯留した溶銑の上部でかつ溶滓が存在する部位の高さ方向の位置を、ここでは銑滓レベルという。
【０００３】
時間の経過とともに炉底部に貯留する溶銑量が増大し、銑滓レベルが上昇する。炉底部に設けられた出銑口を開口すると、溶銑及び溶滓が出銑口から炉外に導き出され、炉内の銑滓レベルが低下する。
【０００４】
高炉操業において、炉内の銑滓レベルを把握することは、出銑周期を決定し、安定した経済的な操業を行う上で重要である。銑滓レベルが上昇してスラグレベルが所定以上に上昇すると、送風圧力変動が大きくなり安定的な操業状態が維持できなくなり、特に、スラグレベルが送風羽口レベルまで上昇してしまうと、スラグが羽口を閉塞してしまい、操業不能となる。スラグレベルの過度な上昇で不安定となった炉内状況を安定化させるためには、コークスの投入量を増加させたり、熱風量を変化させる等の処置が必要となり、操業コストの増大を招くこととなる。
【０００５】
一般に、炉内の銑滓レベルは、銑滓の生成と排出との物質収支より大まかに推定することができる。例えば、銑滓の生成量は、単位時間あたりに高炉に装入した装入物の量とその成分から計算でき、溶銑の排出量は溶銑を収容するトーピードカーの重量変化の測定によって把握し、溶滓の排出量はスラグから製造した水滓の重量をスケールコンベアなどによって測定できるため、これらの銑滓の生成量と排出量の差分より炉内の銑滓量の増加量を推定できる。
【０００６】
特開平７−１５０２１０号公報には、プロセスコンピュータを用いて出銑加速度を計算し、現在の出銑状況が初期、安定期、後期及び終了期のいずれに属するかを判定し、出銑終了時刻を予測する方法が開示されているが、この方法も基本的には上記の物質収支に立脚した炉内残銑滓量の推定方法を利用した技術である。
【０００７】
しかし、物質収支による炉内残銑滓量の推定方法では、銑滓生産量は装入した鉱石類が直ちに溶融することを前提に計算するが、溶解までには少なくとも数時間のタイムラグがあるばかりでなく、成分分析値を元に計算を行うためにその分析値の精度、代表性、バラツキなどによっても誤差が生じる。
【０００８】
また、スラグについては直接的な秤量によって測定するのではなく、水滓後の水分を含んだものをスケールコンベアなどで秤量する程度であり、その誤差は少なくとも１０％程度あるといわれている。このため、物質収支により銑滓レベルを推定する際には大きな誤差を前提に安全代を大きくとった対応が不可欠である。
【０００９】
一方、物質収支による炉内残銑滓量の推定方法を用いずに、銑滓の検出器を用いて銑滓レベルを測定する方法としては、例えば特開昭５３−８６２４２号公報には、高炉の炉床部炉壁に、陽極と陰極からなる一対の棒状黒鉛電極を高さ方向に複数配列してそれぞれ電気的に回路を形成して通電し、溶銑が一対の棒状黒鉛電極に接触したときの導通をパイロットランプまたは電流計で検知することにより銑滓レベルを測定する方法が開示されている。この方法は、銑滓の通電を測定するために少なくとも一対の電極を銑滓に接触するように炉内に挿入して配置する必要があるため、電極表面に銑滓の冷却により形成される凝固層およびその厚み変動により通電状態が変動し信頼性のある炉内銑滓レベルの測定データを得ることは困難である。また、この方法では、電極を炉底部に炉壁を貫通させて設置するために、電極溶損時にはその部分から溶銑が流れ出し、炉底損傷といった大事故を招く可能性がある。
【００１０】
また、特開昭５９−１４０３０９号公報では、高炉の炉底付近の炉壁を構成するレンガに、少なくとも１対の電極を設けて四端子測定法による抵抗測定系（ダブルブリッジ系）電気回路を構成し、電気抵抗の測定値から銑滓レベルを測定する方法が開示されている。この方法は、レンガと銑滓の電気抵抗を測定するため、レンガの経時的な劣化や銑滓のレンガへの浸入等に起因するレンガの導電性の変動、およびレンガ近傍の銑滓温度や銑滓の凝固状態または流動状態に起因する銑滓の導電性の変動などによりレンガと銑滓の電気抵抗の測定値は変動し、信頼性のある炉内銑滓レベルの測定データを得ることは困難である。
【００１１】
高炉炉底部付近の鉄皮表面の高さ方向２個所間において電位差が検出され、その電位差は高炉炉内の銑滓レベルと関係があることが知られている。Development & application of new techniques for blast furnace process control at SSAB Tunnplant, Lulea works. 1995 Ironmaking conference Proceedings pp271 - 279 によると、測定点として炉底部及び羽口上部の鉄皮表面を用いて電位差を測定した結果、出銑の開始・終了のインターバルと測定した電位差の時間的変動との間に相関が見られる点が記載されている。検出される電位差は０．２ｍＶ前後であり、出銑口を閉鎖している間に電位差は０．１ｍＶほど増大し、出銑口を開いて出銑を行っている間に電位差は０．１ｍＶほど減少して元に戻る。
【００１２】
【発明が解決しようとする課題】
上記高炉の鉄皮表面に観測される電位差から銑滓レベルを検出する方法においては、検出される電位差が１ｍＶ以下の微弱な値であるため、ノイズの影響を受けやすい。また、測定電位差は時間と共にドリフトする傾向があるため、銑滓レベルが同一であると推定される場合であっても、電位差の値に差異が生じることがあり、鉄皮表面の電位差から直ちに銑滓レベルを推定することが困難であった。
【００１３】
本発明は、高炉炉内の銑滓レベルを精度良く推定することを可能にする方法及び装置を提供することを目的とする。
【００１４】
【課題を解決するための手段】
高炉炉体の円周方向１個所において鉄皮表面高さ方向に観測される電位差については、上記のようにノイズやドリフトの影響を受けて銑滓レベルの推定が困難であったが、円周方向の複数個所、好ましくは４個所以上において鉄皮表面での高さ方向の電位差を測定し、測定した複数個所の電位差を平均化すると、ノイズやドリフトの影響が相殺されて精度の高い測定値が得られ、銑滓レベルの推定が可能になることが判明した。
【００１５】
出銑終了時においては、銑滓レベルは出銑口の高さ位置にあり、各出銑タイミング毎に変動せずにほぼ一定である。そして、出銑が終了した時点での電位差を基準電位差Ｅ₀とし、基準電位差Ｅ₀からの電位差の上昇分ΔＥに基づいて高炉内の銑滓レベルを評価すると、電位差のドリフトの影響が相殺されて精度の高い測定値が得られ、銑滓レベルの推定が可能になることが判明した。
【００１６】
高炉炉体内部の炉底レンガに複数個の電位測定点を高さ方向に間隔を開けて設け、電位測定点の間の電位差を測定すると、５ｍＶ前後の電位差が存在し、かつ高炉炉内の銑滓レベルの変動に伴って電位差が５ｍＶ前後の幅で大きな変化を示すことが明らかになった。従来知られている高炉炉体の鉄皮表面で検出される電位差と比較すると、電位差の値および銑滓レベルの変動に伴う電位差の変動量ともに、１桁程度高い値である。そのため、ノイズの影響による誤差が非常に小さくなり、従来知られているいずれの方法と比較しても高い精度で銑滓レベルを推定することが可能になった。
【００１７】
本発明は、上記知見に基づいてなされたものであり、その要旨とするところは以下のとおりである。
（１）高炉鉄皮１表面に複数個の電位測定点１１を高さ方向に間隔を開けて設け、該複数個の電位測定点のうち、少なくとも１個の高さ方向の取り付け位置を出銑口のレベル以上とし、かつ少なくとも１個の高さ方向の取り付け位置を出銑口３のレベル未満とするように配置し、前記出銑口のレベル以上に配置した電位測定点と、前記出銑口のレベル未満に配置した電位測定点１１の間で電位差を測定するに際し、高炉炉体円周方向複数の個所で電位差を測定し、該電位差測定値の平均値を算出し、出銑が終了した時点での電位差測定値の平均値を基準電位差Ｅ₀とし、該出銑が終了した時点から出銑開始して再度出銑終了するまでの出銑インターバル毎に前記基準電位差Ｅ₀からの前記電位差測定値の平均値の上昇分を算出し、該算出した電位差測定値の平均値の上昇分ΔＥに基づいて高炉内の銑滓レベルを評価することを特徴とする高炉内の銑滓レベル評価方法。
（２）高炉鉄皮表面に代え、高炉炉底レンガ５外周側表面又は外周側非貫通孔に複数個の電位測定点１１を設けることを特徴とする上記（１）に記載の高炉内の銑滓レベル評価方法。
（３）高炉鉄皮表面に複数個の電位測定点１１を高さ方向に間隔を開けて設け、該複数個の電位測定点のうち、少なくとも１個の高さ方向の取り付け位置を出銑口のレベル以上とし、かつ少なくとも１個の高さ方向の取り付け位置を出銑口３のレベル未満とするように配置し、前記出銑口のレベル以上に配置した電位測定点と、前記出銑口のレベル未満に配置した電位測定点１１の間で電位差を測定する電位差測定装置１２を有し、高炉炉体円周方向複数の個所に該電位差測定装置１２を設け、各電位差測定装置１２における電位差測定値の平均値を算出する平均化手段を有し、出銑が終了した時点での電位差測定値の平均値を基準電位差とし、該出銑が終了した時点から出銑開始して再度出銑終了するまでの出銑インターバル毎に前記基準電位差からの前記電位差測定値の平均値の上昇分を算出する手段を有し、該算出した電位差測定値の平均値の上昇分に基づいて高炉内の銑滓レベルを評価する手段を有することを特徴とする高炉内の銑滓レベル評価装置。
（４）高炉鉄皮表面に代え、高炉炉底レンガ５外周側表面又は外周側非貫通孔に複数個の電位測定点１１を設けることを特徴とする上記（３）に記載の高炉内の銑滓レベル評価装置。
【００１８】
【発明の実施の形態】
本発明の上記（１）においては、図１に示すように、高炉鉄皮１表面に複数個の電位測定点１１を高さ方向に間隔を開けて設ける。銑滓レベルを評価するために有効な電位差は、高炉の高さ方向に発生しているからである。電位差を測定するのであるから個数は最低でも２個必要であり、高さ方向３個所以上にわたって３個以上の電位測定点１１を設ければ、高炉高さ方向の電位分布を評価に加えることも可能である。高さ方向複数の電位測定点の間で電位差を測定するので、この複数の電位測定点１１のセットを電位差測定装置１２と称する。
【００１９】
複数の電位測定点１１の高さ方向取り付け位置は、溶銑と溶滓の境界面を挟むように配置すると、電位差測定値から銑滓レベルを評価するためには好ましい結果を得ることができる。具体的には、少なくとも１個の取り付け位置を出銑口３のレベル以上とし、少なくとも１個の取り付け位置を出銑口３のレベル未満とするように配置すれば、銑滓レベル評価のための電位差測定を行う上で好ましい。図１において、電位測定点１１ａは出銑口３のレベル未満に配置され、電位測定点１１ｂは出銑口３のレベル以上であって羽口４の位置に配置されている。羽口４のレベルを明らかにするため、図１（ｂ）に羽口４を部分図にて示している。
【００２０】
図２に示す高炉炉体の円周方向４個所に、９０°ピッチで上記電位差測定装置１２を配置した。そのうちの２個所の電位差測定装置（１２ｂ、１２ｄ）はそれぞれ出銑口（３ｂ、３ａ）の近辺に、残り２個所の電位差測定装置（１２ａ、１２ｃ）は出銑口３と直角の位置に配置している。各電位差測定装置１２の電位測定点１１の高さ方向の配置については、図１に示すとおり、１個所は高炉炉底部、１個所は羽口レベルに配置した。
【００２１】
上記の合計４個所の各電位差測定装置１２による電位差測定結果を、時間の経過と共にプロットしたのが図３（ａ）である。同図にて上下に並べた４つの折れ線は、それぞれ電位差測定装置１２ａ〜１２ｄにおける電位差測定結果を表している。それぞれ、出銑終了時２２に最も低い電位差となり、その時点における電位差は概略０．４ｍＶ程度である。出銑終了後に電位差は上昇を開始し、次の出銑開始時２１に最大の電位差となり、出銑期間２３の間に電位差は低下する。各電位差測定装置１２で測定した電位差それぞれの信号はノイズ成分を有し、また出銑のインターバル毎に電圧レベルがドリフトし、そのドリフトの傾向は各電位差測定装置毎に異なっている。一方、４個所の電位差測定装置１２における測定電圧の平均値をプロットしたのが図３（ｂ）である。図３（ａ）に比較すると、ノイズ成分のレベルが大幅に低下していることがわかる。また、各電位差測定装置毎に様々だったドリフトが平均化され、出銑終了時２２における電位差がほぼ常に一定の０．４ｍＶ一定レベルを維持することがわかった。
【００２２】
出銑終了時２２においては、銑滓レベルはほぼ出銑口３の位置まで下降しており、各出銑終了時２２毎に異ならずほぼ一定レベルである。従って、出銑終了時２２における測定電位差がほぼ一定レベルに落ち着いているということは、従来、１個所の電位差測定装置で観測されていた電位差のドリフトが、複数個所の電位差測定値の平均値を用いることでほぼ解消されていると考えることができる。
【００２３】
本発明の上記（１）は以上の知見に基づいてなされたものであり、高炉炉体円周方向複数の個所で電位差を測定し、電位差測定値の平均値に基づいて高炉内の銑滓レベルを評価することにより、電位差のドリフトが軽減した効果とノイズレベルの低減効果とが相俟って、高炉内の銑滓レベルを精度よく評価することが可能になった。
【００２４】
炉体円周方向の電位差測定装置の配置位置としては、できるだけ全周に均等に配置することにより、電位差平均値と銑滓レベルとの相関を良好に保つことができる。電位差測定装置の配置個数としては、数が多いほど平均化効果を発揮することができ、４個所以上とすると好ましい。
【００２５】
図４には、約２日間にわたって測定した電位差の円周方向４個所平均値を示す。出銑終了時２２の電位差平均値は、概ね０．４ｍＶで一定であるが、１日目の２２時から２日目の１２時までは約０．４５ｍＶに変化しており、＋０．０５ｍＶのドリフトが見られる。
【００２６】
電位差の測定結果に観測される電圧ドリフトは、このように出銑インターバル（１周期が約３時間）に比較してより長い時間周期である日オーダーの周期で発生している。従って、１回の出銑インターバル（出銑終了から出銑開始して再度出銑終了するまで）の間における電圧ドリフトの変化の程度は小さいものと考えられる。一方、出銑終了時２２においては、上述のように銑滓レベルはほぼ出銑口３の位置まで下降しており、各出銑終了タイミング毎に異ならずほぼ一定レベルである。従って、本発明の上記（１）にあるように、出銑が終了した時点での電位差を基準電位差Ｅ₀とし、基準電位差からの電位差の上昇分ΔＥ（測定電位差Ｅと基準電位差Ｅ₀との差分ΔＥ）を高炉内の銑滓レベル評価に用いることとすると、差分ΔＥがゼロのときは銑滓レベルが出銑口３の位置にあることが確かなのであるから、電圧ドリフトの影響を削除した精度の高い銑滓レベル評価を行うことが可能になるのである。
【００２８】
高炉の炉底付近の内部構造は、図５に示すように、鉄皮１の内側に炉底レンガ５が築造され、炉底レンガ５の最外周と鉄皮１との間にはステーブ６が設けられたりあるいはスタンプ材７が充填されている。本発明の上記（２）においては、電位測定点の設置位置を、本発明（１）における高炉鉄皮表面に代えて炉底レンガ５に設ける。高炉炉体内部に位置する炉底レンガにおける電位測定点１１を用いて電位を測定するために、電位測定点１１から高炉炉体外部まで延びる電極１０を設ける。鉄皮１やステーブ６、スタンプ材７にはこの電極１０を通すための開口が設けられる。電極１０は電位測定点１１において炉底レンガ５に接触し、鉄皮１、ステーブ６、スタンプ材７などとの間に導通を生じないように外部に導かれ、高炉炉体外部において電極１０に別の導線１４を接続し、電圧計１３を用いて複数の電位測定点１１の間の電位差を測定する。
【００２９】
高炉炉体内部の炉底レンガ５に設けた電位測定点１１の間の電位差を測定すると、５ｍＶ前後の電位差が存在し、かつ高炉炉内の銑滓レベルの変動に伴って電位差が５ｍＶ前後の幅で大きな変化を示す。従来知られている高炉炉体の鉄皮表面で検出される電位差と比較すると、電位差の値および銑滓レベルの変動に伴う電位差の変動量ともに、１桁程度高い値である。そのため、ノイズの影響による誤差が非常に小さくなり、従来知られているいずれの方法と比較しても高い精度で銑滓レベルを推定することが可能になった。
【００３０】
炉底レンガ５における高炉半径方向の電位測定点１１の配置位置は、図６（ａ）に示すように最も外周側である炉底レンガ表面に設けても良いし、図６（ｂ）に示すように炉底レンガ５に非貫通孔２０を設けた上で当該非貫通孔２０の奥端を電位測定点１１とする、すなわち炉底レンガ５の内部に電位測定点を設けても良い。図６（ａ）に示す、炉底レンガ表面に電位測定点を設ける方法では、炉底レンガ５の穴加工が不要なので測定点設置が容易である。
【００３１】
本発明（２）においても、電位測定点の高炉高さ方向の配置位置、および高炉円周方向の配置位置についての考え方は、本発明（１）と同様である。
【００３２】
本発明の上記（３）〜（４）の銑滓レベル評価装置は、それぞれ本発明（１）〜（２）の銑滓レベル評価方法を実施するための評価装置に係る発明である。
【００３３】
本発明によって銑滓レベルを評価することにより、従来よりも信頼性の高い炉内貯留銑滓レベルの測定が可能になると共に、この電位差を予め設定した所定値以下にするように操業管理することで炉内銑滓レベルの上昇に伴うトラブルを回避することが可能となる。
【００３４】
高炉操業中に炉内高さ方向の電位差の測定値が予め定めた設定値を超えた場合には、炉内貯留銑滓レベルを低下させるために、銑滓生成速度を減少させる操業アクションおよび銑滓排出速度を増加させる操業アクションの何れか一方または両方を実施すればよい。
【００３５】
銑滓生成速度は、高炉の生産速度そのものであり、単位時間当たりの送風量を増減することにより変化させることが可能である。従って、銑滓生成速度を減少させる操業アクションとしては、羽口送風量を減少させる方法を用いるとよい。
【００３６】
また、銑滓排出速度を増加させる操業アクションとしては、出銑で使用中の出銑口の径を大きな錐で掘削して拡大したり（促進開口）、出銑で使用中の出銑口の他に、他の閉塞している出銑口を開口して複数の出銑口で同時出銑する（ラップ出銑）などの方法により、単位時間当たりの出銑量を増加させる方法を用いることができる。
【００３７】
銑滓生成速度を減少させる操業アクションおよび銑滓排出速度を増加させる操業アクションの何れか一方または両方を実施するか否かを判定するための予め定めた電位差の設定値は、高炉の操業実績と電位差の測定値との関係、および操業トラブルに至ることなく、早期回復が可能な操業アクションのタイミングをもとに高炉オペレータが予め定めておくことができる。
【００３８】
具体的には、炉内残銑滓量の増加に起因して送風圧力変動が大きくなる直前の電位差を過去の実績から求め、その値もしくはその値に安全率を考慮して設定値を決めたり、一定時間出銑を停止して上昇した電位差の経時変化をもとに決めることができる。
【００３９】
【実施例】
炉内容積３２７３ｍ³、炉床径１２．０ｍの高炉において、本発明を用いて銑滓レベルの評価を行った。電位測定点１１を高炉鉄皮１表面とし、高さ方向の配置位置は図１に示すとおりであり、下方の測定点はこの炉体の出銑口３から５ｍ下方の炉底カーボンレンガ１段目レベルとし、上方の測定点は出銑口３から３．８ｍ上方の羽口と同一レベルとし、この２点間で電位差を測定する１組の電位差測定装置１２とした。電位差測定装置１２の円周方向の配置位置は図２に示すとおりであり、円周４個所にそれぞれ９０°の角度を開けて配置し、うち２個所は出銑口３の近傍とした。これら４組の電位差測定装置１２において連続的に電位差を測定し、次いで４個所の電位差の平均値を計算し、この平均値をもとに操業アクションを行った。本実施例においては、多チャンネル電圧測定装置１５において４個所の電圧測定と該測定電圧の平均化とを行っている。平均化されたデータは計算機１６に送られ、基準電位差Ｅ₀の算出、差分ΔＥの算出などの計算を行う。計算機１６としてはパーソナルコンピュータを用いることができる。また、測定したデータは出力装置１７に出力される。
【００４０】
操業アクションとしては、まず前回の出銑終了時における電位差平均値を基準電位差Ｅ₀とし、現時点の電位差平均値Ｅから基準電位差Ｅ₀を差し引いて電位差の上昇分ΔＥを計算する。そして、この電位差の上昇分ΔＥが＋０．３ｍＶ以上となったら出銑量増加のアクションを行う。出銑量増加のアクションとしては、出銑で使用中の出銑口の径を大きな錐で掘削して拡大したり（促進開口）、出銑で使用中の出銑口の他の閉塞している出銑口を開口して複数の出銑口で同時出銑（ラップ出銑）のアクションを行った。
【００４１】
出銑量増加アクションを行うための設定値を＋０．３ｍＶとした理由は、実験的調査において、銑滓レベルの上昇に起因して送風圧力の変動が大きくなり、操業が不安定になる危険が生じる電位差上昇分が約０．３ｍＶであったためである。
【００４２】
本発明を適用した結果、的確かつ早期に銑滓排出促進等のアクションをとることができたため、今まで発生することがあった炉内貯銑滓異常増加による送風圧力変動トラブルがなくなり、操業を安定させることができた。
【００４３】
【発明の効果】
本発明は、高炉炉体鉄皮表面で観察される電位差に基づいて炉内の銑滓レベルを評価するに際し、炉体円周方向複数個所での電位差測定結果を平均化することによってノイズやドリフトの影響が相殺されて精度の高い測定値が得られ、銑滓レベルの高精度な評価が可能になった。
【００４４】
本発明はまた、出銑が終了した時点での電位差を基準電位差とし、基準電位差からの電位差の上昇分に基づいて高炉内の銑滓レベルを評価することにより、電位差のドリフトの影響が相殺されて精度の高い測定値が得られ、銑滓レベルの高精度な推定が可能になった。
【００４５】
本発明はさらに、電位測定点を炉底レンガに設けることにより、銑滓レベルの測定精度を一層向上させることができた。
【図面の簡単な説明】
【図１】本発明の電位差測定状況を示す図であり、（ａ）は高炉部分断面図、（ｂ）は羽口部を示す部分断面図である。
【図２】本発明の電位差測定状況を示す高炉の平面断面図である。
【図３】本発明の電位差測定結果を示す図であり、（ａ）は４個所の各電位差測定装置での測定電位差、（ｂ）は４個所の電位差平均値を示す。
【図４】本発明の電位差測定結果を示す図である。
【図５】炉底レンガで電位差を測定する本発明を示す図であり、（ａ）は高炉部分断面図、（ｂ）は部分拡大図である。
【図６】炉底レンガにおける電位測定点を示す図であり、（ａ）は炉底レンガ表面を電位測定点とし、（ｂ）は炉底レンガ内部を電位測定点としたものである。
【符号の説明】
１鉄皮
２炉内構造物
３出銑口
４羽口
５炉底レンガ
６ステーブ
７スタンプ材
８溶銑
９スラグ
１０電極
１１電位測定点
１２電位差測定装置
１３電圧計
１４導線
１５多チャンネル電圧測定装置
１６計算機
１７出力装置
２０非貫通孔
２１出銑開始時
２２出銑終了時
２３出銑期間[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a soot level evaluation method and an evaluation apparatus in a blast furnace.
[0002]
[Prior art]
In the blast furnace furnace, iron ore as a raw material is supplied from the top of the furnace together with coke into the furnace body, the temperature rises by hot air fed from the tuyere into the furnace body, and is reduced by the coke to form molten iron. The hot metal is stored at the bottom of the furnace, and the hot metal (slag) is stored in contact with the hot metal. Here, the position in the height direction of the portion of the hot metal stored in the blast furnace and where the hot metal exists is referred to as a hot metal level.
[0003]
As time passes, the amount of hot metal stored at the bottom of the furnace increases and the level of hot metal rises. When the tap hole provided in the bottom of the furnace is opened, the hot metal and the hot metal are led out of the furnace from the tap hole, and the level of the hot metal in the furnace is lowered.
[0004]
In blast furnace operation, grasping the soot level in the furnace is important for determining the output cycle and performing stable and economical operation. If the soot level rises and the slag level rises above a predetermined level, the fluctuation of the blowing pressure will increase and it will not be possible to maintain a stable operating state.In particular, if the slag level rises to the blowing tuyere level, the slag will The tuyere is blocked, making it impossible to operate. In order to stabilize the in-furnace situation that has become unstable due to an excessive increase in the slag level, measures such as increasing the amount of coke input or changing the amount of hot air are required, leading to an increase in operating costs. It will be.
[0005]
In general, the soot level in the furnace can be roughly estimated from the material balance of soot production and discharge. For example, the amount of soot generated can be calculated from the amount of charge and its components charged into the blast furnace per unit time, and the amount of hot metal discharged can be ascertained by measuring the weight change of a torpedo car containing hot metal. The amount of soot discharged from the slag can be measured with a scale conveyor or the like, so that the amount of soot in the furnace can be estimated from the difference between the amount of soot produced and the amount discharged.
[0006]
In Japanese Patent Laid-Open No. 7-150210, the output acceleration is calculated using a process computer, it is determined whether the current output status belongs to the initial period, the stable period, the latter period, or the end period, and the output end time However, this method is also basically a technique that uses the above method for estimating the amount of residue in the furnace based on the material balance.
[0007]
However, in the estimation method of the amount of residue in the furnace based on the mass balance, the amount of dredged production is calculated on the assumption that the charged ores are immediately melted, but there is a time lag of at least several hours before melting. In addition, since the calculation is performed based on the component analysis value, an error occurs due to the accuracy, representativeness, and variation of the analysis value.
[0008]
In addition, slag is not measured by direct weighing, but is measured only by weighing a thing containing moisture after pouring with a scale conveyor or the like, and the error is said to be at least about 10%. For this reason, when estimating the soot level from the material balance, it is indispensable to take a large safety allowance on the assumption of a large error.
[0009]
On the other hand, as a method for measuring the soot level using a soot detector without using the estimation method of the amount of residue in the furnace based on the mass balance, for example, JP-A-53-86242 discloses a blast furnace. When a plurality of pairs of rod-like graphite electrodes consisting of an anode and a cathode are arranged in the height direction on the hearth of the hearth of the furnace and electrically energized, and the hot metal contacts the pair of rod-like graphite electrodes A method is disclosed in which the soot level is measured by detecting the continuity of the battery with a pilot lamp or an ammeter. In this method, in order to measure the energization of the soot, it is necessary to insert and arrange at least a pair of electrodes in the furnace so as to contact the soot. It is difficult to obtain reliable measurement data of the level in the furnace because the energization state fluctuates due to fluctuations in the layer and its thickness. Further, in this method, since the electrode is installed through the furnace wall at the bottom of the furnace, when the electrode is melted, hot metal flows out from the part, which may cause a serious accident such as damage to the furnace bottom.
[0010]
In Japanese Patent Laid-Open No. 59-140309, a resistance measuring system (double bridge system) electric circuit using a four-terminal measuring method is provided by providing at least one pair of electrodes on a brick constituting the furnace wall near the bottom of the blast furnace. A method of configuring and measuring the wrinkle level from electrical resistance measurements is disclosed. This method measures the electrical resistance between the brick and the fence, so that the conductivity of the brick due to the deterioration of the brick over time, the penetration of the fence into the brick, etc. The measured values of the electrical resistance of bricks and fences fluctuate due to fluctuations in the conductivity of the fence due to the solidification state or flow state of the fence, and it is difficult to obtain reliable measurement data for the level in the furnace It is.
[0011]
It is known that a potential difference is detected between two places in the height direction of the iron skin surface near the bottom of the blast furnace furnace, and the potential difference is related to the soot level in the blast furnace furnace. According to Development & application of new techniques for blast furnace process control at SSAB Tunnplant, Lulea works.1995 Ironmaking conference Proceedings pp271-279 It describes that there is a correlation between the start / end interval of the output and the temporal variation of the measured potential difference. The detected potential difference is around 0.2 mV, the potential difference increases by about 0.1 mV while closing the tap and the potential difference is 0.1 mV while opening the tap. It decreases and returns to the original.
[0012]
[Problems to be solved by the invention]
In the method of detecting the soot level from the potential difference observed on the surface of the blast furnace, the detected potential difference is a weak value of 1 mV or less, and thus is susceptible to noise. In addition, since the measured potential difference tends to drift with time, even if it is estimated that the wrinkle level is the same, a difference may occur in the value of the potential difference. It was difficult to estimate the wrinkle level.
[0013]
An object of this invention is to provide the method and apparatus which make it possible to estimate the soot level in a blast furnace furnace accurately.
[0014]
[Means for Solving the Problems]
As for the potential difference observed in the height direction of the iron shell surface at one place in the circumferential direction of the blast furnace body, it was difficult to estimate the soot level due to the influence of noise and drift as described above. Measuring the potential difference in the height direction on the surface of the iron skin at multiple locations in the direction, preferably at 4 locations or more, and averaging the measured potential differences at the multiple locations cancels out the effects of noise and drift, resulting in highly accurate measurement values It was found that it was possible to estimate the heel level.
[0015]
At the end of the output, the output level is at the height of the output port and is substantially constant without changing at each output timing. Then, when the potential difference at the time when the dredging is finished is set as the reference potential difference E ₀ and the drought level in the blast furnace is evaluated based on the increase ΔE of the potential difference from the reference potential difference E ₀ , the influence of the potential difference drift is offset. As a result, it was found that highly accurate measurement values were obtained, and it was possible to estimate the wrinkle level.
[0016]
A plurality of potential measurement points are provided on the bottom brick inside the blast furnace body at intervals in the height direction, and when the potential difference between the potential measurement points is measured, a potential difference of about 5 mV exists, It became clear that the potential difference showed a large change in the range of about 5 mV with the fluctuation of the wrinkle level. Compared to the conventionally known potential difference detected on the surface of the blast furnace core, the value of the potential difference and the amount of fluctuation of the potential difference accompanying the fluctuation of the soot level are values that are about one digit higher. For this reason, the error due to the influence of noise becomes very small, and it becomes possible to estimate the eyelid level with high accuracy compared to any conventionally known method.
[0017]
This invention is made | formed based on the said knowledge, The place made into the summary is as follows.
(1) A plurality of potential measurement points 11 are provided on the surface of the blast furnace iron shell 1 at intervals in the height direction, and at least one mounting position in the height direction is selected from the plurality of potential measurement points. A potential measuring point that is at or above the level of the mouth and at least one mounting position in the height direction is less than the level of the mouth 3; When measuring the potential difference between potential measurement points 11 arranged below the level of the mouth, the potential difference is measured at a plurality of locations in the circumferential direction of the blast furnace body, the average value of the measured potential difference values is calculated, and the tapping ends The average value of the measured potential difference at the time of the output is defined as the reference potential difference E _0, and the output from the reference potential difference E ₀ is output at every output interval from the time when the output is completed until the output is completed again. Calculate the increase in the average value of the measured potential difference, and A method for evaluating a soot level in a blast furnace, wherein the soot level in the blast furnace is evaluated based on an increase ΔE in the average value of the difference measurement values.
(2) Instead of the blast furnace iron skin surface, a plurality of potential measurement points 11 are provided on the outer peripheral side surface of the blast furnace bottom brick 5 or on the outer peripheral side non-through hole.滓 Level evaluation method.
(3) A plurality of potential measurement points 11 are provided on the surface of the blast furnace iron core at intervals in the height direction, and at least one height mounting position among the plurality of potential measurement points is an outlet. And at least one mounting position in the height direction is set to be less than the level of the spout 3, and a potential measuring point disposed at the level of the spout and the spout A potential difference measuring device 12 for measuring a potential difference between potential measuring points 11 arranged below the level of the first and second potential difference measuring devices 12 at a plurality of locations in the circumferential direction of the blast furnace body. An averaging means for calculating the average value of the measured values is provided, and the average value of the potential difference measured at the time when the output is finished is set as a reference potential difference. The above standard at every output interval until the end And means for calculating the increase in the average value of the potential difference measurements from position difference, to have a means for evaluating the Zukukasu level in blast furnace based on the increase in the average value of the potential difference measurements the calculated A device for evaluating the level of soot inside a blast furnace.
(4) Instead of the surface of the blast furnace iron skin, a plurality of potential measuring points 11 are provided on the outer surface of the blast furnace bottom brick 5 or on the outer peripheral side non-through hole.滓 Level evaluation device.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
In the above (1) of the present invention, as shown in FIG. 1, a plurality of potential measurement points 11 are provided on the surface of the blast furnace iron shell 1 at intervals in the height direction. This is because the potential difference effective for evaluating the soot level is generated in the height direction of the blast furnace. Since the potential difference is measured, at least two pieces are required. If three or more potential measurement points 11 are provided in three or more height directions, the potential distribution in the blast furnace height direction can be added to the evaluation. Is possible. Since a potential difference is measured between a plurality of potential measurement points in the height direction, the set of the plurality of potential measurement points 11 is referred to as a potential difference measuring device 12.
[0019]
When the height direction attachment positions of the plurality of potential measurement points 11 are arranged so as to sandwich the interface between the hot metal and the hot metal, a preferable result can be obtained in order to evaluate the hot metal level from the potential difference measurement value. Specifically, if at least one mounting position is set to be equal to or higher than the level of the spout opening 3, and at least one mounting position is set to be lower than the level of the spout opening 3, it is necessary to evaluate the wrinkle level. This is preferable in measuring the potential difference. In FIG. 1, the potential measurement point 11 a is disposed below the level of the tap hole 3, and the potential measurement point 11 b is disposed at the position of the tuyere 4 above the level of the tap hole 3. In order to clarify the level of the tuyere 4, the tuyere 4 is shown in a partial view in FIG.
[0020]
The potential difference measuring devices 12 were arranged at 90 ° pitches at four locations in the circumferential direction of the blast furnace furnace body shown in FIG. Two of the potential difference measuring devices (12b, 12d) are arranged in the vicinity of the tap opening (3b, 3a), and the other two potential difference measuring devices (12a, 12c) are arranged at a position perpendicular to the tap opening 3. is doing. About the arrangement | positioning of the height direction of the electric potential measurement point 11 of each electric potential difference measuring device 12, as shown in FIG. 1, one place was arrange | positioned at the bottom of a blast furnace furnace and one place at the tuyere level.
[0021]
FIG. 3A is a plot of the potential difference measurement results obtained by the potential difference measuring devices 12 in total of four locations as time elapses. The four broken lines arranged vertically in the figure represent the potential difference measurement results in the potential difference measuring devices 12a to 12d, respectively. Each of them has the lowest potential difference at the end of brewing 22 and the potential difference at that time is about 0.4 mV. The potential difference starts to rise after the completion of the extraction, reaches the maximum potential difference at the next output start 21, and the potential difference decreases during the output period 23. Each potential difference signal measured by each potential difference measuring device 12 has a noise component, and the voltage level drifts at every output interval, and the tendency of the drift is different for each potential difference measuring device. On the other hand, FIG. 3B is a plot of the average values of the measured voltages in the four potential difference measuring devices 12. Compared to FIG. 3A, it can be seen that the level of the noise component is greatly reduced. In addition, it was found that the various drifts for each potential difference measuring device were averaged, and the potential difference at the end of tapping 22 maintained a constant level of 0.4 mV which was almost always constant.
[0022]
At the end of brewing 22, the level of the heel is almost lowered to the position of the brewing port 3, and is almost constant at each end of brewing 22. Therefore, the fact that the measured potential difference at the end of the tapping 22 has settled at a substantially constant level means that the drift of the potential difference that has been conventionally observed with one potential difference measuring device is the average value of the potential difference measured values at a plurality of locations. It can be considered that it is almost solved by using.
[0023]
The above (1) of the present invention has been made on the basis of the above knowledge, and the potential difference is measured at a plurality of locations in the circumferential direction of the blast furnace body, and the soot level in the blast furnace is determined based on the average value of the measured potential difference. As a result of the evaluation, the effect of reducing the potential difference drift and the effect of reducing the noise level can be combined to accurately evaluate the soot level in the blast furnace.
[0024]
As the arrangement position of the potential difference measuring device in the furnace body circumferential direction, the correlation between the average value of the potential difference and the soot level can be favorably maintained by arranging them as evenly as possible. As the number of potential difference measuring devices, the larger the number, the more the averaging effect can be exhibited.
[0025]
FIG. 4 shows the average value of four potential differences in the circumferential direction measured over about two days. The average value of the potential difference at the end of brewing 22 is approximately 0.4 mV, and is constant at about 0.45 mV from 22:00 on the first day to 12:00 on the second day, and +0.05 mV Drift is seen.
[0026]
As described above, the voltage drift observed in the measurement result of the potential difference is generated in the period of the day order which is a longer time period than the output interval (one period is about 3 hours). Accordingly, it is considered that the degree of change in voltage drift during one output interval (from the end of output until the end of output is completed again) is small. On the other hand, at the end of brewing 22, the heel level is lowered to the position of the brewing port 3 as described above, and is almost constant without being different at each brewing end timing. Therefore, as described in the above ( 1 ) of the present invention, the potential difference at the time when the output is finished is set as the reference potential difference E _0, and the increase ΔE (the difference between the measured potential difference E and the reference potential difference E _{0 from the} reference potential difference). If the difference ΔE) is used to evaluate the soot level in the blast furnace, when the difference ΔE is zero, it is certain that the soot level is at the position of the spout 3 so the effect of voltage drift has been deleted. This makes it possible to perform highly accurate eyelid level evaluation.
[0028]
As shown in FIG. 5, the inner structure of the blast furnace near the bottom of the blast furnace is constructed such that a bottom brick 5 is built inside the iron shell 1, and a stave 6 is provided between the outermost periphery of the bottom brick 5 and the iron core 1. It is provided or is filled with a stamp material 7. In the above (2) of the present invention, the installation position of the potential measurement points, instead of the blast furnace steel shell surface definitive to the present invention (1) provided in the furnace bottom bricks 5. In order to measure the potential using the potential measurement point 11 in the bottom brick located inside the blast furnace body, an electrode 10 extending from the potential measurement point 11 to the outside of the blast furnace body is provided. The iron skin 1, the stave 6, and the stamp material 7 are provided with openings for passing the electrodes 10. The electrode 10 comes into contact with the furnace bottom brick 5 at the potential measurement point 11 and is guided to the outside so as not to cause conduction with the iron shell 1, the stave 6, the stamp material 7, and the like, and is connected to the electrode 10 outside the blast furnace body. Another conductor 14 is connected, and a potential difference between the plurality of potential measurement points 11 is measured using a voltmeter 13.
[0029]
When the potential difference between the potential measurement points 11 provided on the bottom brick 5 inside the blast furnace body is measured, there is a potential difference of about 5 mV, and the potential difference is about 5 mV with the variation of the soot level in the blast furnace furnace. A large change in width. Compared to the conventionally known potential difference detected on the surface of the blast furnace core, the value of the potential difference and the amount of fluctuation of the potential difference accompanying the fluctuation of the soot level are values that are about one digit higher. For this reason, the error due to the influence of noise becomes very small, and it becomes possible to estimate the eyelid level with high accuracy compared to any conventionally known method.
[0030]
The arrangement position of the potential measuring point 11 in the blast furnace radial direction in the furnace bottom brick 5 may be provided on the surface of the furnace bottom brick which is the outermost side as shown in FIG. 6A, or as shown in FIG. Thus, after providing the non-through hole 20 in the furnace bottom brick 5, the back end of the non-through hole 20 may be set as the potential measurement point 11, that is, the potential measurement point may be provided inside the furnace bottom brick 5. In the method of providing a potential measurement point on the furnace bottom brick surface shown in FIG. 6 (a), it is easy to install the measurement point because hole machining of the furnace bottom brick 5 is not required.
[0031]
In the present invention (2), the concept of the blast furnace arrangement position in the height direction, and the blast furnace circumferential position of the potential measurement point is similar to the present invention (1).
[0032]
The above ( 3 ) to ( 4 ) wrinkle level evaluation apparatus according to the present invention is an invention relating to an evaluation apparatus for carrying out the wrinkle level evaluation method according to the present invention (1) to ( 2 ), respectively.
[0033]
By evaluating the soot level according to the present invention, it becomes possible to measure the in-furnace stored soot level with higher reliability than before, and to manage the operation so that this potential difference is set to a predetermined value or less. Therefore, it is possible to avoid troubles associated with the rise of the level in the furnace.
[0034]
If the measured value of the potential difference in the furnace height direction exceeds the preset value during blast furnace operation, the operation action and dr One or both of the operation actions that increase the soot discharge rate may be performed.
[0035]
The soot production rate is the production rate itself of the blast furnace, and can be changed by increasing or decreasing the amount of blown air per unit time. Therefore, as an operation action for reducing the soot generation speed, a method for reducing the tuyere air volume may be used.
[0036]
In addition, as an operation action to increase the dredging discharge speed, the diameter of the spout used at the time of excavation can be expanded by digging with a large cone (promotion opening), In addition, use a method that increases the amount of output per unit time by opening other closed output ports and simultaneously outputting at multiple output ports (wrap output). Can do.
[0037]
The preset value of the potential difference for determining whether or not to perform one or both of the operation action for decreasing the soot generation rate and the operation action for increasing the soot discharge rate is determined based on the operation results of the blast furnace. The blast furnace operator can determine in advance based on the relationship with the measured value of the potential difference and the timing of the operation action that allows early recovery without causing operation trouble.
[0038]
Specifically, the potential difference immediately before the blast pressure fluctuation increases due to an increase in the residual amount in the furnace is obtained from past results, and the set value is determined by taking the safety factor into that value or the value. It can be determined on the basis of the change over time in the potential difference that has risen after stopping the brewing for a certain period of time.
[0039]
【Example】
In a blast furnace with a furnace internal volume of 3273 m ³ and a hearth diameter of 12.0 m, the soot level was evaluated using the present invention. The potential measurement point 11 is the surface of the blast furnace iron skin 1, the arrangement position in the height direction is as shown in FIG. 1, and the lower measurement point is one stage of the bottom carbon brick 5 m below the outlet 3 of the furnace body. The eye level was set at the same level as the tuyere 3.8 m above the spout 3, and a pair of potential difference measuring devices 12 for measuring the potential difference between the two points was obtained. The arrangement position of the potential difference measuring device 12 in the circumferential direction is as shown in FIG. 2, and is arranged at an angle of 90 ° in each of the four circumferences, two of which are in the vicinity of the spout 3. These four sets of potential difference measuring devices 12 continuously measured the potential difference, then calculated the average value of the four potential differences, and performed an operation action based on the average value. In the present embodiment, the multi-channel voltage measuring device 15 measures four voltages and averages the measured voltages. The averaged data is sent to the computer 16, and calculation such as calculation of the reference potential difference E ₀ and calculation of the difference ΔE is performed. A personal computer can be used as the computer 16. The measured data is output to the output device 17.
[0040]
As an operation action, first, the potential difference average value at the end of the previous extraction is set as the reference potential difference E _0, and the potential difference increase ΔE is calculated by subtracting the reference potential difference E ₀ from the current potential difference average value E. When the potential difference increase ΔE becomes +0.3 mV or more, an action for increasing the output amount is performed. As an action to increase the amount of tapping, the diameter of the tapping outlet that is in use at tapping is expanded by digging with a large cone (promoting opening), or other blocking of tapping outlet that is in use at tapping. At the same time, the action of simultaneous output (lap output) was performed at multiple output ports.
[0041]
The reason why the setting value for performing the dredging amount increasing action is set to +0.3 mV is that there is a risk that the fluctuation of the blowing pressure will increase due to the increase in dredging level and the operation will become unstable in the experimental investigation. This is because the potential difference generated is about 0.3 mV.
[0042]
As a result of applying the present invention, it was possible to take actions such as promotion of soot discharge accurately and early, so there was no trouble with fluctuations in the blowing pressure due to abnormal increase in storage in the furnace that had occurred so far, It was possible to stabilize.
[0043]
【The invention's effect】
The present invention, when evaluating the soot level in the furnace based on the potential difference observed on the surface of the blast furnace core, the noise and drift by averaging the potential difference measurement results at a plurality of locations in the furnace body circumferential direction As a result, high-accuracy measurement values were obtained, and high-level evaluation was possible.
[0044]
In the present invention, the potential difference at the time when the dredging is finished is used as a reference potential difference, and the drought level in the blast furnace is evaluated based on the increase in potential difference from the reference potential difference, thereby canceling the influence of potential difference drift. Highly accurate measurement values were obtained, and high-level estimation was possible.
[0045]
Furthermore, the present invention can further improve the measurement accuracy of the soot level by providing potential measurement points on the brick at the bottom of the furnace.
[Brief description of the drawings]
1A and 1B are diagrams showing a potential difference measurement situation of the present invention, in which FIG. 1A is a partial sectional view of a blast furnace, and FIG. 1B is a partial sectional view showing a tuyere.
FIG. 2 is a plan cross-sectional view of a blast furnace showing a potential difference measurement situation of the present invention.
FIGS. 3A and 3B are diagrams showing the results of potential difference measurement according to the present invention, in which FIG. 3A shows measured potential differences in each of four potential difference measuring apparatuses, and FIG. 3B shows average potential differences at four locations.
FIG. 4 is a diagram showing a potential difference measurement result of the present invention.
FIGS. 5A and 5B are diagrams showing the present invention for measuring a potential difference with a furnace bottom brick, wherein FIG. 5A is a partial sectional view of a blast furnace and FIG. 5B is a partially enlarged view.
6A and 6B are diagrams showing potential measurement points in a furnace bottom brick, wherein FIG. 6A shows a potential measurement point on the furnace bottom brick surface, and FIG. 6B shows a potential measurement point inside the furnace bottom brick.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Iron skin 2 Furnace structure 3 Outlet 4 Tuna 5 Furnace bottom brick 6 Stave 7 Stamping material 8 Hot metal 9 Slag 10 Electrode 11 Potential measuring point 12 Potential difference measuring device 13 Voltmeter 14 Conductor 15 Multichannel voltage measuring device 16 Computer 17 Output device 20 Non-through hole 21 At the start of tapping 22 At the end of tapping 23 Tapping period

Claims

A plurality of potential measurement points are provided at intervals in the height direction on the surface of the blast furnace iron shell, and at least one of the plurality of potential measurement points is set at a height direction higher than the level of the outlet. In addition, at least one mounting position in the height direction is arranged to be less than the level of the tap hole, and the electric potential measurement point arranged above the level of the tap hole is arranged below the level of the tap hole. When measuring the potential difference between the measured potential measurement points, measure the potential difference at a plurality of locations in the blast furnace body circumferential direction, calculate the average value of the measured potential difference, and measure the potential difference at the time when the extraction is completed. The average value of the reference potential difference is used as the reference potential difference, and the increment of the average value of the measured potential difference from the reference potential difference is calculated at every output interval from the time when the output is completed until the output is completed again. Increase of the average value of the calculated potential difference Zukukasu level evaluation method of the blast furnace, characterized by assessing the Zukukasu level in blast furnace based on.

The method for evaluating a soot level in a blast furnace according to claim 1, wherein a plurality of potential measurement points are provided on the outer surface of the blast furnace bottom brick or the outer non-through hole in place of the surface of the blast furnace iron skin.

A plurality of potential measurement points are provided at intervals in the height direction on the surface of the blast furnace iron shell, and at least one of the plurality of potential measurement points is set at a height direction higher than the level of the outlet. In addition, at least one mounting position in the height direction is arranged to be less than the level of the tap hole, and the electric potential measurement point arranged above the level of the tap hole is arranged below the level of the tap hole. An electric potential difference measuring device for measuring the electric potential difference between the measured electric potential measuring points, the electric potential difference measuring device is provided at a plurality of locations in the circumferential direction of the blast furnace body, and an average for calculating an average value of the electric potential difference measured in each electric potential difference measuring device The average value of the measured potential difference at the time when the output is finished is used as a reference potential difference, and every output interval from the time when the output is completed until the output is completed again. The measured potential difference from the reference potential difference And means for calculating the increase in the average value, Zukukasu of the blast furnace, characterized in that it comprises a means for evaluating the Zukukasu level in blast furnace based on the increase in the average value of the potential difference measurements the calculated Level evaluation device.

4. The soot level evaluation apparatus in a blast furnace according to claim 3, wherein a plurality of potential measurement points are provided on a blast furnace bottom brick outer peripheral surface or an outer peripheral non-through hole in place of the blast furnace iron skin surface.