JP4598204B2

JP4598204B2 - Blast furnace operation method when a large amount of pulverized coal is injected

Info

Publication number: JP4598204B2
Application number: JP21125297A
Authority: JP
Inventors: 陽三細谷; 謙一樋口; 隆折本
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 1997-07-23
Filing date: 1997-07-23
Publication date: 2010-12-15
Anticipated expiration: 2017-07-23
Also published as: JPH1143710A

Description

【０００１】
【発明の属する技術分野】
本発明は、微粉炭多量吹き込みの時の高炉操業安定化を目的とし、高アルミナ焼結鉱の多量使用と高炉スラグ比を低減する高炉操業方法に関する。
【０００２】
【従来の技術】
コークスとの代替効果により溶銑原価低減効果が大きく、コークス炉の老朽化対策としても重要な微粉炭吹き込みが最近注目され、日本国内ではほぼ全高炉に採用されている。例えば「材料とプロセス」７（１９９４），ｐ１２４には微粉炭比１８０ｋｇ／ｔ−ｐ以上の吹き込み操業を装入物分布の改善（シャープな逆Ｖ型の融着帯を維持）と羽口前条件の改善で安定して継続している結果が報告されている。また「材料とプロセス」７（１９９４），ｐ１２６には１週間の微粉炭比２００ｋｇ／ｔ−ｐの操業試験結果が報告され、コークスＤＩの向上と高酸素富化操業、低Ａｌ₂ Ｏ₃ ・高被還元性焼結鉱の使用、局所的な高Ｏ／Ｃ部を形成させない装入物分布制御により達成した内容が記載されている。
【０００３】
融着帯厚み増加による炉下部通気性悪化を抑制するために、低Ａｌ₂ Ｏ₃ ・高被還元性焼結鉱を使用したと報告しているので、装入物の低Ａｌ₂ Ｏ₃ 化で融着帯厚み増加を抑制したと考えられる。さらに「材料とプロセス」８（１９９５），ｐ．３１９には月間微粉炭比２１８ｋｇ／ｔ−ｐの操業結果として、炉下部通気・通液性の改善のためにスラグ比の低下（３２０→２８０ｋｇ／ｔ−ｐ）と塊成鉱の高ＲＩ（被還元性）化（ＨＰＳ鉱の全面使用）、コークス強度向上を実施したことなどが報告されている。ＨＰＳ鉱が低ＳｉＯ₂ ・低Ａｌ₂ Ｏ₃ 鉱であるのはよく知られているので、融着帯厚み増加を装入物の低ＳｉＯ₂ 化と低Ａｌ₂ Ｏ₃ 化で抑制したと考えられる。
【０００４】
【発明が解決しようとする課題】
微粉炭吹き込み操業において、微粉炭を１５０ｋｇ／ｔ−ｐ以上吹込むためには次の技術課題を解決しておく必要がある。それは▲１▼微粉炭比増加により炉頂から装入するコークス量が減少（コークススリットの縮小）するので、高炉内の鉱石／コークス比（Ｏ／Ｃ）が高くなることによる融着帯厚み増加とそれ以下の炉芯部を含む炉下部の通気性の悪化、▲２▼羽口での微粉炭燃焼量増加によりガス流れが炉内で周辺流化し、炉体からの放散熱増加による熱損失の増大、▲３▼熱流比（固体熱容量／ガス熱容量）の低下により炉内ガス温度が上昇するので、炉頂から排出するガスの顕熱の増加による熱効率低下などである。微粉炭比が１５０ｋｇ／ｔ−ｐ以上になると、装入物の荷下がり悪化や圧力損失、炉体熱負荷増などにより操業が不安定になることが他に報告されているので、これらの技術課題の解決は重要と考えられる。
【０００５】
その中でも特に、微粉炭比増加で鉱石／コークス比（Ｏ／Ｃ）が高くなることによる融着帯厚み増加の問題が大きいと考えられる。炉下部の圧力損失が増加すると同時にガスの中心流れが抑制されて周辺流が助長されるので、荷下がりが不安定になり炉体熱負荷が増大する。ところが、Ｏ／Ｃが高くなることによる融着帯厚み増加とそれ以下の炉下部通気性の悪化に対する装入物の改善対策はすでに説明した文献にあるように、装入物の低ＳｉＯ₂ 化と低Ａｌ₂ Ｏ₃ 化（１．７ｍａｓｓ％未満）を実施した例が見られる程度である。
しかし、１９９６年の日本鉄鋼業全体の焼結鉱Ａｌ₂ Ｏ₃ の平均値は１．８０ｍａｓｓ％強であり、今後も焼結鉱Ａｌ₂ Ｏ₃ は徐々に増加していくことが予想されるので、多くの高炉が長期的に低Ａｌ₂ Ｏ₃ 焼結鉱を製造し、使用するのは困難であると考えられる。それに加えて高Ａｌ₂ Ｏ₃ 鉱石は通常の鉱石より安価であるので、今後は高Ａｌ₂ Ｏ₃ 焼結鉱の使用技術の確立が高炉操業の重要課題の一つになると考えられる。
【０００６】
他に特開平６−１００９１１号公報には、微粉炭吹き込み高炉操業において、微粉炭吹き込み量を１５０ｋｇ／ｔ−ｐ以上とし、投入水素量を１５〜２０ｋｇ／ｔ−ｐとし、さらに酸素を３〜５％富化することを特徴とする微粉炭多量吹き込み時の高炉操業方法が記載されている。水蒸気吹き込み量の増加と酸素富化により融着帯を逆Ｖ字形に変化させて通気性を改善する方法であるが、水蒸気と酸素を別に製造して高炉に吹き込むため、高炉操業コストが大幅に悪化する欠点がある。
【０００７】
特開昭６１−５６２１１号公報には、高炉操業において焼結鉱塩基度（Ｃ／Ｓ）を２以上とし、高炉スラグの目標塩基度より上昇分は高炉にてＳｉＯ₂ 源副原料の装入により調整し、軟化融着帯レベルを下降させることにより、溶銑中Ｓｉ濃度を低下させることを特徴とする高炉操業方法が記載されている。
この方法は、塩基度上昇で焼結鉱高温性状を改善して軟化融着帯の収縮率や通気抵抗を改善しているが、高炉スラグ量を増加させる欠点があるので、炉下部の通気性改善が必要な微粉炭多量吹き込み操業への適用は困難である。
【０００８】
特開平９−１３１０７号公報には、１５０ｋｇ／ｔ−ｐ以上の多量の微粉炭を吹き込む高炉操業法において、炉頂から装入されるコークスを除く装入物の８０％以上に、Ａｌ₂ Ｏ₃ 成分が１．９〜２．５％、ＳｉＯ₂ 成分が４．０〜４．８％、ＭｇＯ成分が１．２〜２．４％、ＣａＯ成分が６．０〜９．０％の焼結鉱を用いる高炉操業方法が記載されている。
この方法は高炉スラグ量の上昇を抑制し、焼結鉱滴下スラグの粘度を改善して、高出銑比、低燃料比操業が可能になるとしている。しかし、焼結鉱の強度を向上させるＳｉＯ₂ 成分、ＣａＯ成分がそれぞれ４．８％以下、９．０％以下と低く、焼結鉱の強度を低下させるＭｇＯ成分が１．２％以上であるので、高炉に装入される焼結鉱の被還元性は良好であるが、微粉炭多量吹き込み操業で重要な焼結鉱強度が低下する欠点がある。また、炉頂から装入されるコークスを除く装入物の８０％以上に本焼結鉱を使用するので、高炉スラグのＡｌ₂ Ｏ₃ 成分やＭｇＯ成分を調整する自由度が少なく、さらに大幅な成分調整をするには塊状の副原料を高炉に直接装入するか、粉状の副原料を高炉羽口から直接吹き込むことが必要になり、高炉操業に悪影響を与えることが懸念される。
【０００９】
本発明法は、上記の問題点を解決するためになされたもので、焼結鉱成分を適正に調整して強度、被還元性ともに優れた高Ａｌ₂ Ｏ₃ 焼結鉱を製造し、その焼結鉱を高炉から装入される原料の５０〜８０ｍａｓｓ％の装入割合で装入して、高Ａｌ₂ Ｏ₃ 焼結鉱の多量使用と高炉スラグ比の低下を可能にする微粉炭多量吹き込み時の高炉操業を提供することを目的とする。
【００１０】
【課題を解決するための手段】
具体的には微粉炭吹き込み量１５０ｋｇ／ｔ−ｐ以上で、Ａｌ₂Ｏ₃を１．８〜２．５ｍａｓｓ％含有する高Ａｌ₂Ｏ₃焼結鉱を５０〜８０ｍａｓｓ％含む原料を高炉炉頂部から装入する高炉操業であって、（１）前記焼結鉱は、結晶水を５ｍａｓｓ％以上含む鉄鉱石を焼結新原料中に２５ｍａｓｓ％以上配合、焼成して、ＳｉＯ₂を３．９〜４．９ｍａｓｓ％、ＭｇＯを０．５〜１．２ｍａｓｓ％未満、Ａｌ₂Ｏ₃を１．８〜２．５ｍａｓｓ％含有し、ＣａＯ／ＳｉＯ₂ が１．９〜２．５となるように製造し、前記高炉炉頂部から装入する原料の残部が酸性ペレット、塩基性ペレット、コールドペレット、ＣａＯ／ＳｉＯ₂が１．９未満の焼結鉱、塊鉱、スクラップ、還元鉄の２種類以上からなり、前記高Ａｌ ₂ Ｏ ₃ 焼結鉱の装入割合を調整して高炉スラグ比を２８０ｋｇ／ｔ−ｐ以下にして高炉操業することを特徴とする微粉炭多量吹き込み時の高炉操業方法。
【００１１】
なお、本発明における高炉炉頂部から装入する原料とは、焼結鉱、塊鉱、ペレット、団鉱、スクラップ、還元鉄、雑原料の合計を示しており、鉄マンガン鉱、製鋼スラグ、石灰石、その他副原料は含まない。
【００１２】
【発明の実施の形態】
燃料比が５００ｋｇ／ｔ−ｐの前提で微粉炭比が１５０ｋｇ／ｔ−ｐ（コークス比は３５０ｋｇ／ｔ−ｐ）に増加すると、鉱石／コークス比（Ｏ／Ｃ）は４．６レベルに上昇する。微粉炭比が２００ｋｇ／ｔ−ｐ（コークス比は３００ｋｇ／ｔ−ｐ）になると、Ｏ／Ｃは５．４まで上昇する。微粉炭比が低い通常装入時のＯ／Ｃは４．０未満であるので、微粉炭比１５０ｋｇ／ｔ−ｐ以上では鉱石層厚が大幅に増加することになり、融着帯形状が肥大化することになる。
【００１３】
図１に微粉炭比６０、２００ｋｇ／ｔ−ｐ吹き込み操業でのシュミレーション結果に基づく炉内融着帯形状の変化を示す。微粉炭比が増加すると融着帯が肥大化しているのが分かる。この融着帯の肥大化を抑制できれば炉内通気性が改善される。
本発明は高微粉炭比操業においても、高Ａｌ₂ Ｏ₃ 焼結鉱の多量使用を可能にし、高炉スラグ量を低減して操業を安定化するものである。
焼結鉱成分のＳｉＯ₂ が３．９〜４．９ｍａｓｓ％、ＭｇＯが０．５〜１．２ｍａｓｓ％未満、Ａｌ₂ Ｏ₃ が１．８〜２．５ｍａｓｓ％、ＣａＯ／ＳｉＯ₂ が１．９〜２．５になるように製造した焼結鉱は強度（ＳＩ、ＴＩ）、被還元性（ＪＩＳ−ＲＩ）、高温還元・軟化溶融性状がともに優れている。この焼結鉱の還元粉化性（ＲＤＩ）はやや悪化するが、焼結鉱製造時のコークス配合比の増加や配合原料中の生石灰配合比の増加により通常焼結鉱のＲＤＩレベルまで改善されることが分かった。
【００１４】
焼結鉱成分の中で、ＳｉＯ₂ を３．９〜４．９ｍａｓｓ％、ＭｇＯを０．５〜１．２ｍａｓｓ％未満、ＣａＯ／ＳｉＯ₂ を１．９〜２．５の範囲としたのは、Ａｌ₂ Ｏ₃ が１．９〜２．５ｍａｓｓ％の範囲の高Ａｌ₂ Ｏ₃ 焼結鉱では、ＳｉＯ₂ が３．９ｍａｓｓ％未満になると強度の低下が見られ、４．９ｍａｓｓ％超になると被還元性と高温還元・軟化溶融性状の悪化が見られたからであり、ＭｇＯが０．５ｍａｓｓ％未満まで低下させると高温還元・軟化溶融性状の悪化が顕著になり、１．２ｍａｓｓ％以上になると強度が低下するためである。ＣａＯ／ＳｉＯ₂ も１．９未満になると強度の低下が見られ、２．５超になると高温還元・軟化溶融性状が悪化する。なお、Ａｌ₂ Ｏ₃ が１．９〜２．５ｍａｓｓ％の範囲としたのは、Ａｌ₂ Ｏ₃ が１．９ｍａｓｓ％以上になると上記の焼結鉱成分の範囲に制御する効果が顕著になるが、２．５ｍａｓｓ％超になると効果が見られなくなり強度低下が顕著になるからである。
【００１５】
次に結晶水を５ｍａｓｓ％以上含む鉄鉱石を焼結新原料中に２５ｍａｓｓ％以上配合するとしたのは、焼成中に結晶水が蒸発することにより表１に示した焼結鉱中の微細気孔が増加し、高温還元・軟化溶融性状の改善がより顕著になるからである。
低ＳｉＯ₂ ・低ＭｇＯ・高Ａｌ₂ Ｏ₃ ・高ＣａＯ／ＳｉＯ₂ 焼結鉱の高炉への装入割合を高炉から装入される原料の５０〜８０ｍａｓｓ％としたのは、８０ｍａｓｓ％を超えると高炉操業に悪影響を与えないで高炉スラグ組成を制御、調整することは困難になるからであり、一方５０ｍａｓｓ％未満になると上記の焼結鉱を使用する効果が見られなくなるからである。
【００１６】
この高Ａｌ₂ Ｏ₃ 焼結鉱を高炉から装入される原料の５０〜８０ｍａｓｓ％に規定して高炉に装入するので、スラグの粘性や溶銑の脱硫率に影響を及ぼす高炉スラグのＡｌ₂ Ｏ₃ 、ＭｇＯ成分の割合を残部の酸性ペレット、塩基性ペレット、コールドペレット、ＣａＯ／ＳｉＯ₂ が１．９未満の焼結鉱、塊鉱、スクラップ、還元鉄などの装入により容易に調整することができ、高炉スラグ量を低減することが可能になるのも本発明の特徴である。
また、高炉スラグのＣａＯ／ＳｉＯ₂ を１．２５〜１．３２に制御することにより高Ａｌ₂ Ｏ₃ 焼結鉱使用時においても高炉操業をより安定化させ、溶銑の脱硫率もより向上させることができる。高炉スラグのＣａＯ／ＳｉＯ₂ を１．２５以上としたのは、それ以下になると脱硫率が悪化し始めるからである。１．３２以下としたのは、それ以上になるとスラグ初晶がダイカルシウムシリケートになり、スラグの融点の変化が大きくなって流動性が悪化するからである。高炉スラグ比を２８０ｋｇ／ｔ−ｐ以下にするとしたのは、高炉操業の安定がより顕著になるからである。
【００１７】
まず、低ＳｉＯ_２・低ＭｇＯ・高Ａｌ_２Ｏ_３・高ＣａＯ／ＳｉＯ_２焼結鉱の製造試験結果について述べる。焼結鉱は４５０ｍ^２の焼結機で製造した。従来法と本発明法１（参考例）の焼結鉱を比較して、強度（ＳＩ）とＲＤＩ、ＪＩＳ−ＲＩの測定結果を表１に、高温還元・軟化溶融性状測定結果を図２に示す。本発明法１（参考例）で使用する焼結鉱は、強度とＪＩＳ−Ｒ１に加えて高温還元性と軟化溶融性状が大幅に改善されているのが分かる。本発明法１（参考例）では、高Ａｌ_２Ｏ_３で低ＳｉＯ_２、低ＭｇＯ、高Ｃ／Ｓの焼結鉱を製造しており、これを高炉に装入して使用することにより、高Ａｌ_２Ｏ_３焼結鉱の使用が可能になる。
【００１８】
次に、結晶水を５ｍａｓｓ％以上含有する鉱石を焼結新原料中に３０ｍａｓｓ％配合して焼結した低ＳｉＯ₂ ・低ＭｇＯ・高Ａｌ₂ Ｏ₃ ・高ＣａＯ／ＳｉＯ₂ 焼結鉱の製造試験結果について述べる。同じように、焼結鉱は４５０ｍ² の焼結機で製造した。従来法と本発明法２の焼結鉱を比較して、強度（Ｓ１）とＲＤＩ、ＪＩＳ−ＲＩの測定結果を表１に、高温還元・軟化溶融性状測定結果を図２に示す。本発明法２で使用する焼結鉱は、表１に示すように水銀ポロシメーターで測定した１２０μｍ以下の微細気孔が多いので、ＪＩＳ−ＲＩに加えて高温還元性と軟化溶融性状が大幅に改善されているのが分かる。
【００１９】
本発明法１（参考例）、および、本発明法２では、高Ａｌ_２Ｏ_３で低ＳｉＯ_２、低ＭｇＯ、高Ｃ／Ｓの焼結鉱を製造しており、これを高炉から装入される原料の５０〜８０ｍａｓｓ％に規定して装入して使用することにより、高炉スラグ成分のＡｌ_２Ｏ_３、ＭｇＯを操業方針に応じて調整しながら高炉スラグ比を低減することが可能になる。
【００２０】
【表１】
【００２１】
本発明法１（参考例）または本発明法２の焼結鉱を使用して、微粉炭吹き込み量を１８０ｋｇ／ｔ−ｐに増加させたＡ高炉（内容積３８００ｍ^３）での実施例を説明する。本発明法１（参考例）および本発明法２の実施例を従来法と比較して表２にまとめた。従来法では、微粉炭比１３０ｋｇ／ｔ−ｐの操業レベル（比較例１）から微粉炭比１８０ｋｇ／ｔ−ｐ操業（期間Ａ、比較例２）に移行する過程で通気抵抗が増大し、スリップ頻度が増し、炉体放散熱も増えた。これは、微粉炭比の増加によりＯ／Ｃが上昇し、炉内全圧損が大きくなったためで、特に１７０ｋｇ／ｔ−ｐ以上でその傾向が顕著である。一方、本発明法の焼結鉱１（参考例）および本発明法２に切り換えると、微粉炭吹き込み量が１６０ｋｇ／ｔ−ｐでもむしろ炉内全圧損値と炉体放散熱量は低下し、スリップ発生回数は激減した。これは強度増加による炉上部の通気性改善に加え、シャフト部での被還元性が向上し、さらに高温性状の改善により、通気抵抗を悪化させる融着帯根部の肥大化を防止したためと考えられる。炉下部の異常も全く見られなかった。
【００２２】
【表２】
【００２３】
【発明の効果】
以上のように、微粉炭吹き込み量を１５０ｋｇ／ｔ−ｐ以上に増加させても、本発明法により炉内全圧損値を増加させることなく高炉安定操業を長期に継続することができた。
本発明法は、高アルミナ焼結鉱の多量使用と高炉スラグ量の低減を可能にし、かつ微粉炭多量吹き込みの高炉操業方法を可能にする。
【図面の簡単な説明】
【図１】高炉内融着帯をシュミレーションした図
【図２】本発明法の焼結鉱の高温性状測定結果を示す図[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for operating a blast furnace in which a large amount of high alumina sintered ore is used and a blast furnace slag ratio is reduced for the purpose of stabilizing blast furnace operation when a large amount of pulverized coal is injected.
[0002]
[Prior art]
The effect of reducing hot metal costs has been great due to the replacement effect with coke, and pulverized coal injection, which is important as a countermeasure for aging of coke ovens, has recently attracted attention, and has been adopted in almost all blast furnaces in Japan. For example, “Materials and Processes” 7 (1994), p124 is a blowing operation with a pulverized coal ratio of 180 kg / tp or more to improve charge distribution (maintaining a sharp reverse V-type cohesive zone) and in front of the tuyere Stable and continuing results have been reported with improved conditions. In “Materials and Processes” 7 (1994), p126, the results of an operation test with a pulverized coal ratio of 200 kg / tp for one week were reported. Improvement of coke DI, high oxygen enrichment operation, low Al ₂ O _3. The contents achieved through the use of a highly reducible sintered ore and the charge distribution control without forming a local high O / C part are described.
[0003]
To suppress the furnace bottom breathable deteriorated due to the increase cohesive zone thickness, since the reported using low Al ₂ O ₃ · high reducibility sinter, low Al ₂ O ₃ of feedstock It is thought that the increase in the cohesive zone thickness was suppressed. Furthermore, “Materials and Processes” 8 (1995), p. In 319, as a result of the operation of the monthly pulverized coal ratio of 218 kg / tp, the slag ratio decreased (320 → 280 kg / tp) and the high RI of the agglomerate (to improve the aeration and liquid permeability in the lower part of the furnace) It has been reported that (reducibility) has been improved (overall use of HPS ore) and coke strength has been improved. Since it is well known that HPS ores are low SiO ₂ and low Al ₂ O ₃ ores, it is thought that the increase in the cohesive zone thickness was suppressed by reducing the SiO ₂ and low Al ₂ O ₃ charges. It is done.
[0004]
[Problems to be solved by the invention]
In the operation of blowing pulverized coal, in order to blow pulverized coal at 150 kg / tp or more, it is necessary to solve the following technical problem. (1) The amount of coke charged from the top of the furnace decreases due to the increase in the pulverized coal ratio (reduction of the coke slit), so the thickness of the cohesive zone increases as the ore / coke ratio (O / C) in the blast furnace increases. Deterioration of air permeability in the lower part of the furnace including the core part of the furnace and below, and (2) heat loss due to increase in the amount of pulverized coal combustion at the tuyere and peripheral flow in the furnace, and increased heat dissipated from the furnace body (3) Since the gas temperature in the furnace rises due to a decrease in the heat flow ratio (solid heat capacity / gas heat capacity), there is a decrease in thermal efficiency due to an increase in sensible heat of the gas discharged from the top of the furnace. It has been reported that when the pulverized coal ratio becomes 150 kg / tp or more, the operation becomes unstable due to worsening of the charge drop, pressure loss, increased furnace heat load, etc. The solution of the problem is considered important.
[0005]
Among them, the problem of increase in the thickness of the cohesive zone due to the increase in the ore / coke ratio (O / C) due to the increase in the pulverized coal ratio is considered to be large. At the same time as the pressure loss at the lower part of the furnace increases, the central flow of the gas is suppressed and the peripheral flow is promoted, so that the unloading becomes unstable and the furnace heat load increases. However, as described in the literature already described, there is a reduction in SiO _{2 in the} charge, as described in the literature, for the measures to improve the thickness of the cohesive zone due to the increase in O / C and the lowering of the lower furnace breathability. and examples carried low Al ₂ O ₃ of (less than 1.7mass%) is the degree seen.
However, the average value of sintered ore Al ₂ O _{3 for} the entire Japanese steel industry in 1996 was just over 1.80 mass%, and it is expected that the sintered ore Al ₂ O ₃ will gradually increase in the future. Therefore, it is considered difficult for many blast furnaces to manufacture and use low Al ₂ O ₃ sintered ores in the long term. In addition, since high Al ₂ O ₃ ore is cheaper than ordinary ore, the establishment of technology for using high Al ₂ O ₃ sintered ore will be one of the important issues in blast furnace operation.
[0006]
In addition, in JP-A-6-100911, pulverized coal injection blast furnace operation has a pulverized coal injection amount of 150 kg / tp or more, an input hydrogen amount of 15 to 20 kg / tp, and oxygen of 3 to 3 A blast furnace operating method at the time of blowing a large amount of pulverized coal characterized by being enriched by 5% is described. It is a method of improving the air permeability by changing the cohesive zone into an inverted V shape by increasing the amount of steam blown and oxygen enrichment, but because the steam and oxygen are separately manufactured and blown into the blast furnace, the blast furnace operating cost is greatly increased There are drawbacks that get worse.
[0007]
Japanese Patent Application Laid-Open No. 61-56211 discloses that the basicity of sintered ore (C / S) is 2 or more in blast furnace operation, and the amount of increase from the target basicity of blast furnace slag is charged with SiO ₂ source auxiliary material in the blast furnace. The blast furnace operating method is characterized in that the Si concentration in the hot metal is lowered by adjusting the temperature and lowering the softening cohesive zone level.
This method improves the high temperature properties of the sinter due to the increase in basicity and improves the shrinkage rate and ventilation resistance of the softened cohesive zone, but has the disadvantage of increasing the amount of blast furnace slag. It is difficult to apply to a large quantity of pulverized coal in need of improvement.
[0008]
In JP-A-9-13107, in a blast furnace operation method in which a large amount of pulverized coal of 150 kg / tp or more is blown, 80% or more of the charge excluding coke charged from the top of the furnace contains Al ₂ O. _Three components 1.9-2.5%, SiO ₂ component 4.0-4.8%, MgO component 1.2-2.4%, CaO component 6.0-9.0% A blast furnace operating method using ore is described.
This method suppresses an increase in the amount of blast furnace slag, improves the viscosity of the sinter dripping slag, and enables a high output ratio and low fuel ratio operation. However, the SiO ₂ component and CaO component that improve the strength of the sintered ore are as low as 4.8% or less and 9.0% or less, respectively, and the MgO component that decreases the strength of the sintered ore is 1.2% or more. Therefore, although the reducibility of the sintered ore charged in the blast furnace is good, there is a drawback that the strength of the sintered ore which is important in the operation of blowing a large amount of pulverized coal is lowered. In addition, since this sintered ore is used for more than 80% of the charge excluding coke charged from the top of the furnace, the degree of freedom to adjust the Al ₂ O ₃ component and MgO component of the blast furnace slag is small and even greater. In order to adjust the components properly, it is necessary to charge the bulk auxiliary material directly into the blast furnace or to blow in powdery auxiliary raw material directly from the blast furnace tuyere, which may cause adverse effects on blast furnace operation.
[0009]
The method of the present invention was made in order to solve the above-mentioned problems. By appropriately adjusting the sinter components, a high Al ₂ O ₃ sinter with excellent strength and reducibility was produced. A large amount of pulverized coal that allows a large amount of high Al ₂ O ₃ sintered ore to be used and a reduction in the blast furnace slag ratio by charging the sintered ore at a charging rate of 50 to 80 mass% of the raw material charged from the blast furnace. The purpose is to provide blast furnace operation at the time of blowing.
[0010]
[Means for Solving the Problems]
Specifically, a blast furnace top with a raw material containing 50 to 80 mass% of high Al ₂ O ₃ sintered ore containing 1.8 to 2.5 mass% of Al ₂ O ₃ with a pulverized coal injection amount of 150 kg / tp or more (1) The sintered ore contains iron ore containing 5 mass% or more of crystal water in a sintered raw material at 25 mass% or more and calcined to obtain 3.9 of SiO ₂ . ~4.9mass%, MgO less than 0.5~1.2mass%, the Al ₂ O ₃ containing 1.8~2.5mass%, as CaO / SiO ₂ is 1.9 to 2.5 2 or more types of sintered ore, lump ore, scrap, and reduced iron with the balance of raw materials manufactured and charged from the top of the blast furnace furnace being acidic pellets, basic pellets, cold pellets, CaO / SiO ₂ less than 1.9 Tona is, by adjusting the charging ratio of the high Al ₂ O ₃ sintered ore Blast furnace method when the blast furnace slag ratio not exceed 280 kg / t-p pulverized coal multimeric blowing characterized that you blast furnace operation.
[0011]
Contact name and material is charged from the blast furnace top in the present invention, sintered ore, lump ore, pellets, briquettes, scrap, reduced iron, shows a total of miscellaneous materials, iron-manganese ore, steel slag, Limestone and other auxiliary materials are not included.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
If the pulverized coal ratio increases to 150 kg / tp (coke ratio is 350 kg / tp) on the assumption that the fuel ratio is 500 kg / tp, the ore / coke ratio (O / C) rises to the 4.6 level. To do. When the pulverized coal ratio reaches 200 kg / tp (the coke ratio is 300 kg / tp), the O / C increases to 5.4. Since the O / C during normal charging with a low pulverized coal ratio is less than 4.0, the ore layer thickness increases significantly when the pulverized coal ratio is 150 kg / tp or more, and the cohesive zone shape is enlarged. It will become.
[0013]
FIG. 1 shows the change in the in-furnace cohesive zone shape based on the simulation results in the pulverized coal ratio 60, 200 kg / tp blowing operation. It can be seen that the cohesive zone is enlarged as the pulverized coal ratio increases. If the enlargement of the cohesive zone can be suppressed, the air permeability in the furnace can be improved.
The present invention makes it possible to use a large amount of high Al ₂ O ₃ sintered ore even in a high pulverized coal ratio operation, and to stabilize the operation by reducing the amount of blast furnace slag.
The sintered ore component SiO ₂ is 3.9 to 4.9 mass%, MgO is 0.5 to less than 1.2 mass%, Al ₂ O ₃ is 1.8 to 2.5 mass%, and CaO / SiO ₂ is 1. The sintered ore manufactured to 9 to 2.5 is excellent in strength (SI, TI), reducibility (JIS-RI), high temperature reduction / softening melt properties. Although the reduced powdering property (RDI) of this sinter is somewhat deteriorated, it has been improved to the RDI level of ordinary sinter due to the increase in the coke blending ratio and the increase in the quicklime blending ratio in the blended raw material. I found out.
[0014]
Among sintered ore components, the SiO ₂ 3.9~4.9mass%, MgO less than 0.5～1.2Mass%, was in the range of CaO / SiO ₂ of 1.9 to 2.5 is in the high-Al ₂ O ₃ sinter ranging Al ₂ O ₃ is 1.9～2.5Mass%, the SiO ₂ is less than 3.9Mass% decrease in strength is observed, the 4.9Mass% greater This is because deterioration of the reducibility and high-temperature reduction / softening melt properties was observed. When MgO is reduced to less than 0.5 mass%, the deterioration of the high-temperature reduction / softening melting properties becomes significant, and the mass is increased to 1.2 mass% or more. This is because the strength decreases. When CaO / SiO _{2 is} also less than 1.9, the strength is decreased, and when it exceeds 2.5, the high-temperature reduction / softening melt properties deteriorate. The reason why Al ₂ O ₃ is in the range of 1.9 to 2.5 mass% is that when Al ₂ O ₃ is 1.9 mass% or more, the effect of controlling the above range of sinter components becomes remarkable. However, if it exceeds 2.5 mass%, the effect is not seen and the strength is significantly reduced.
[0015]
Next, the iron ore containing 5 mass% or more of crystal water is blended in the sintered raw material by 25 mass% or more because the crystal pores evaporate during firing and the fine pores in the sintered ore shown in Table 1 This is because the increase in the high temperature reduction / softening and melting properties becomes more remarkable.
The ratio of low SiO ₂ / low MgO / high Al ₂ O ₃ / high CaO / SiO ₂ sintered ore charged to the blast furnace is set to 50-80 mass% of the raw material charged from the blast furnace, which exceeds 80 mass%. This is because it becomes difficult to control and adjust the composition of the blast furnace slag without adversely affecting the operation of the blast furnace. On the other hand, when it is less than 50 mass%, the effect of using the sintered ore is not seen.
[0016]
Since this high Al ₂ O ₃ sintered ore is regulated to 50-80 mass% of the raw material charged from the blast furnace and charged into the blast furnace, the Al _{2 of the} blast furnace slag which affects the viscosity of the slag and the desulfurization rate of the hot metal. The ratio of O ₃ and MgO components can be easily adjusted by charging the remaining acidic pellets, basic pellets, cold pellets, sintered ore with less than 1.9 CaO / SiO ₂ , lump ore, scrap, reduced iron, etc. It is also a feature of the present invention that the amount of blast furnace slag can be reduced.
Further, by controlling CaO / SiO ₂ of blast furnace slag to 1.25 to 1.32, blast furnace operation is further stabilized even when high Al ₂ O ₃ sintered ore is used, and the desulfurization rate of hot metal is further improved. be able to. The reason why the blast furnace slag CaO / SiO _{2 is set} to 1.25 or more is that the desulfurization rate starts to deteriorate when the CaO / SiO ₂ is less than 1.25. The reason why it is set to 1.32 or less is that if it is more than that, the primary crystal of slag becomes dicalcium silicate, and the change in the melting point of slag becomes large and the fluidity deteriorates. The reason why the blast furnace slag ratio is set to 280 kg / tp or less is because the stability of blast furnace operation becomes more remarkable.
[0017]
First, the production test results of low SiO ₂ / low MgO / high Al ₂ O ₃ / high CaO / SiO ₂ sintered ore will be described. The sinter was produced with a 450 m ² sintering machine. Comparison between the conventional method and the sintered ore of the present invention method 1 (reference example) , the strength (SI), RDI, and JIS-RI measurement results are shown in Table 1, and the high temperature reduction / softening melt property measurement results are shown in FIG. Show. It can be seen that the sintered ore used in Method 1 (Reference Example) of the present invention has greatly improved high-temperature reducing properties and softening and melting properties in addition to strength and JIS-R1. In the present invention method 1 (reference example) , a high Al ₂ O ₃ and low SiO ₂ , low MgO, high C / S sintered ore is manufactured, and this is charged into a blast furnace and used. Use of high Al ₂ O ₃ sintered ore becomes possible.
[0018]
Next, production of low SiO ₂ , low MgO, high Al ₂ O ₃ , high CaO / SiO ₂ sintered ore, in which ore containing 5 mass% or more of crystal water is mixed and sintered at 30 mass% in a new sintered raw material The test results are described. Similarly, the sinter was produced on a 450 m ² sintering machine. Table 1 shows the strength (S1), RDI, and JIS-RI measurement results, and FIG. 2 shows the high-temperature reduction / softening melt property measurement results, comparing the conventional method and the sintered ore of the present invention method 2. As shown in Table 1, the sintered ore used in Method 2 of the present invention has many fine pores of 120 μm or less as measured with a mercury porosimeter, so that the high-temperature reducibility and softening and melting properties are greatly improved in addition to JIS-RI. I understand that.
[0019]
In the present invention method 1 (reference example) and in the present invention method 2, a high-Al ₂ O ₃ low-SiO ₂ , low-MgO, high-C / S sintered ore is produced and charged from a blast furnace. It is possible to reduce the blast furnace slag ratio while adjusting the blast furnace slag components Al ₂ O ₃ and MgO according to the operation policy by using 50 to 80 mass% of the raw material to be charged. Become.
[0020]
[Table 1]
[0021]
An example in A blast furnace (internal volume 3800 m ³ ) in which the amount of pulverized coal injection was increased to 180 kg / tp using the sintered ore of the present invention method 1 (reference example) or the present invention method 2 will be described. To do. Examples of Invention Method 1 (Reference Example) and Invention Method 2 are summarized in Table 2 in comparison with the conventional method. In the conventional method, the ventilation resistance increases in the process of shifting from the operation level (comparative example 1) with a pulverized coal ratio of 130 kg / tp to the operation with a pulverized coal ratio of 180 kg / tp (period A, comparative example 2). The frequency increased and the furnace heat dissipation increased. This is because O / C increased due to an increase in the pulverized coal ratio, and the total pressure loss in the furnace increased, and this tendency is particularly remarkable at 170 kg / tp or more. On the other hand, when switching to the sintered ore 1 of the present invention (reference example) and the present invention method 2, even if the amount of pulverized coal injection is 160 kg / tp, the total pressure loss value in the furnace and the heat dissipated in the furnace body are reduced, and the slip The number of occurrences has dropped dramatically. This is thought to be due to the improvement of the air permeability at the top of the furnace due to the increase in strength, the improvement of the reducibility at the shaft, and the prevention of the enlargement of the cohesive zone root that deteriorates the airflow resistance by improving the high temperature properties. . There was no abnormality at the bottom of the furnace.
[0022]
[Table 2]
[0023]
【The invention's effect】
As described above, even when the amount of pulverized coal injection was increased to 150 kg / tp or more, the blast furnace stable operation could be continued for a long time without increasing the total pressure loss value in the furnace by the method of the present invention.
The method of the present invention makes it possible to use a large amount of high alumina sintered ore and reduce the amount of blast furnace slag, and also to enable a method of operating a blast furnace with a large amount of pulverized coal.
[Brief description of the drawings]
FIG. 1 is a simulation of a blast furnace cohesive zone. FIG. 2 is a diagram showing a high temperature property measurement result of a sintered ore according to the present invention.

Claims

The raw material containing 50 to 80 mass% of high Al ₂ O ₃ sintered ore containing 1.8 to 2.5 mass% of Al ₂ O ₃ with a pulverized coal injection amount of 150 kg / tp or more is charged from the top of the blast furnace. In the blast furnace operation, the sintered ore contains iron ore containing 5 mass% or more of crystal water in a sintered raw material of 25 mass% or more, calcined, and SiO ₂ is 3.9 to 4.9 mass%, The blast furnace furnace is manufactured such that MgO is contained in an amount of less than 0.5 to 1.2 mass%, Al ₂ O ₃ is contained in an amount of 1.8 to 2.5 mass%, and CaO / SiO ₂ is 1.9 to 2.5. balance acidic pellet material to be inserted from the top, a basic pellet becomes cold pellets, CaO / SiO ₂ is sintered ore of less than 1.9, lump ore, scrap, of two or more kinds of reduced iron, the high Al ₂ adjust the insertion rate of O ₃ sinter Blast furnace method when pulverized coal multimeric blowing, characterized in that the blast furnace operation with the furnace slag ratio below 280kg / t-p.