JP3840891B2

JP3840891B2 - High-grade fired agglomerate for iron making and method for producing the same

Info

Publication number: JP3840891B2
Application number: JP2000326444A
Authority: JP
Inventors: 登坂本
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2000-10-26
Filing date: 2000-10-26
Publication date: 2006-11-01
Anticipated expiration: 2020-10-26
Also published as: JP2002129247A

Description

【０００１】
【発明の属する技術分野】
この発明は、高炉で使用される製鉄用原料としての焼成塊成鉱及びその製造方法に関するものであり、特に、品質が良好且つ品位が高く、しかもコークスの代替として微粉炭を多量に吹き込む高炉操業において、燃料比の低減を図ろうとする高炉操業時に、高炉装入用原料として適した焼成塊成鉱及びその製造方法に関するものである。
【０００２】
【従来の技術】
高炉を有する製鉄所においては、従来、高炉で発生する多量のガスが、製鉄所全体への燃料供給源として確保され、製鉄所内における適切なエネルギーバランスをとることに寄与している。しかしながら、上記燃焼性ガスの利用は同時にＣＯ₂の発生を伴なう。そこで、製鉄所におけるＣＯ₂発生量低減による環境改善への寄与の観点から、将来の望ましい製鉄所における高炉操業では、高炉における燃料比の低減を図ることにより、上記燃焼性ガスの発生量を低減することが重要な課題となる。
【０００３】
高炉で発生するガスの低減要因及び低減阻止要因は、いくつかのものが互いに複雑に関連しているが、特に最近の重要な開発技術との関連でみると、高炉への微粉炭多量吹込み操業、高炉原料である焼結鉱の低ＳｉＯ₂焼結鉱製造工程、及び高炉への装入物分布制御方法のそれぞれにおいて実施される反応操作要因がそれに相当する。
【０００４】
高炉への微粉炭多量吹込み操業、及び低ＳｉＯ₂焼結鉱製造技術を、高炉での燃料比の増減の観点から、従ってまたガス発生量の増減の観点からみると下記の通りである。
【０００５】
高炉への微粉炭多量吹込み操業は、コークス用原料炭の枯渇化に対処するために、安価な非微粘結炭を主体とした微粉炭によるコークス代替をねらってコークス比の低減を図ると共に、コークス炉の操業負荷を減らし炉寿命の延長を図ることにより、高炉及びコークス炉におけるコストの低減を目標としている。ところが、微粉炭の多量吹込みによりコークス比は低減するが、反面、微粉炭吹込み量の増加につれてガス発生量が増加すると共に、オールコークス操業に比較して微粉炭吹込み操業においては、炉内の熱流比（固体の熱容量／ガスの熱容量）が低下して、高炉内の通気性・通液性が悪化する。また、発生ガス量増加に伴い高炉内でのガス流れ分布が悪化し、その結果、高炉における燃料比は増加傾向をたどる。
【０００６】
低ＳｉＯ₂焼結鉱の製造は、高炉内における被還元性向上、炉内の通気・通液性向上、及び高炉スラグ比低下を図ることを目的とする。しかしながら、高炉燃料比低下を意図して、塩基度（ＣａＯ／ＳｉＯ₂）一定の条件で焼結鉱配合率を上昇させると、焼結鉱塩基度よりはるかに低い高炉スラグの目標塩基度に合わせるため、高炉でＳｉＯ₂系の添加が必要となる。その結果、低ＳｉＯ₂焼結鉱を使用するにもかかわらず、高炉のスラグ比低下効果を鈍らせる。
【０００７】
上記事情に鑑み本発明者等は、上述した最近の開発技術を生かしつつ、しかも経済的に高炉における燃料比の低減を図り、製鉄所におけるＣＯ₂発生量の低減に結び付けることにより、環境改善に寄与し得る高炉操業技術の確立を目指すことにした。
【０００８】
そこで、本発明者等は、高炉における燃料比低減の方向として、高炉装入原料中、７０〜８５ｍａｓｓ％程度を占める焼結鉱中のスラグ化成分組成を一層低減させ、しかも当該焼結鉱の高温性状を更に改善することにより、高炉の炉内通気・通液性を損なうことなく、特に、高炉への微粉炭吹込み量を高水準に維持しつつ高炉の安定操業を確保し、高炉での燃料比低減を図ることを目的とした。
【０００９】
上記観点から従来の焼結鉱製造技術をみると、最も先行していると思われる焼結鉱の製造技術として、特公平２−４６５８号公報等に開示されている焼成塊成鉱とその製造方法に関するものがある。これらの技術は、所謂ＨＰＳ（ＨｙｂｒｉｄＰｅｌｌｅｔｉｚｅｄＳｉｎｔｅｒ）と称される新しいタイプの焼成塊成鉱に関する技術である。このＨＰＳは、例えば特公平２−４６５８号公報に次の通り開示されている。即ち、所定粒径の微粉を所定割合で含有している微粉鉄鉱石と、他の所定粒径の粗粒を他の所定割合で含有している粗粒鉄鉱石とを主原料として、両者を所定の比率で配合し、媒溶剤を添加し混合して造粒する。こうして粗粒鉄鉱石を核として形成された擬似粒子（ミニペレット）の表面に粉コークス等の粉状燃料を被覆して、粒径３〜１２ｍｍのペレットを調製し、これを焼結機で焼成して焼成塊成鉱を得る。
【００１０】
得られた焼成塊成鉱は、元の擬似粒子（ミニペレット）の核部分の一部が残留し、この多数の残留核部分で一塊りとなり、各残留核部分の外層部にカルシウムフェライト相と少量のスラグ相とからなる相が形成され、この相が各残留核部分を相互に結合する結合相を形成すると共に、各残留核部分は多孔質形態を有するというものである。
【００１１】
【発明が解決しようとする課題】
上記ＨＰＳは上述した通り、残留核部分（元の擬似粒子（ミニペレット）の核部分の一部が残留したもの）が多孔質形態であり、残留核部分同士の間隙には、カルシウムフェライト相と少量のスラグ相とからなる結合相が形成している。しかも、ＨＰＳ中のＳｉＯ₂含有率は低い水準にある。その結果、高炉装入原料として、炉内での通気・通液性が確保され、高炉の高生産性及び安定操業に寄与している。
【００１２】
しかしながら、ＨＰＳの品質面及び生産性等についての利点を維持しつつ、今後の鉄鉱石及び原料炭の供給動向に適切に対処し、しかも、設備及び運転コストの上昇を抑制して溶銑の製造コストを上昇させずに、高炉における燃料比の低減を図り、高炉で発生するガス（高炉ガス）を減らして、所期目的を達成するためには、高炉操業において発生するスラグ量、即ち、高炉スラグ比の低減を図り、スラグ顕熱を減らすことが重要であり、効果的である。本発明者等は、かかる着想に立脚し、従来のＨＰＳを更に改善するために、焼結原料の事前処理工程で調製すべき擬似粒子の設計改善が必要であることに着眼した。
【００１３】
かくして、この発明の課題は、焼成塊成鉱の鉱物学的形態及び物理特性として、内部に酸化鉄主体で多孔質形態の多数の粒子状核部分が含まれ、しかもこの粒子状核部分同士の間隙に、この多孔質核部分の集合体の低い強度を補完して、十分な強度を維持し得る結合相を、必要最低限度量だけ形成させる。かくして、被還元性、耐還元粉化性及び冷間強度共に、従来のＨＰＳと同程度以上の水準を有し、しかも、スラグ化成分組成を一層低減させ、高温性状が一層改善された焼成塊成鉱を得ることにより、所期目的の高炉スラグ比の低減を可能とする。このような塊成鉱の焼成を可能とする焼結原料に適した、核部分とその結合相となるべき外層部分とで構成される擬似粒子を調製する技術を創案することにある。
焼成され得るように、鉄鉱石、媒溶剤及び固体燃料の分布と成分組成分布とを有する擬似粒子を設計し、これを適切に焼成することにある。
【００１４】
こうしてこの発明の目的は、従来のＨＰＳと同程度ないしそれ以上に被還元性、耐還元粉化性及び冷間強度に優れ、高温性状に優れており、高炉内における通気・通液性に優れた特性を維持しつつ、しかも、従来のＨＰＳよりもＳｉＯ₂含有率が低く、塩基度（ＣａＯｍａｓｓ％／ＳｉＯ₂ｍａｓｓ％）が低く、且つ全鉄含有率が高い塊成鉱を製造し、これを高炉装入原料とすることにより、高炉スラグ比の低減、組織の多孔質化、その結果として、被還元性の向上、高炉燃料比の低減が可能となるような製鉄用高品位焼成塊成鉱及びその製造方法を提供することにある。
【００１５】
【課題を解決するための手段】
本発明者等は、上記課題に対して鋭意試験及び研究を行ない、次の知見を得た。即ち、上述した特性を備えた焼成塊成鉱用の擬似粒子の設計は、焼成過程における初期融液の生成状態を支配する焼結原料中の塩基度（ＣａＯ含有率（ｍａｓｓ％）／ＳｉＯ₂含有率（ｍａｓｓ％））を、核部分と外層部分とにおいて適切に配分・制御する、即ち、１．５〜１．８（ＣａＯ：ＳｉＯ₂＝６０：４０〜６４：３６）程度を境界として、核部分の塩基度を十分に小さくし、外層部分の塩基度を十分に大きくすると共に、擬似粒子全体の塩基度を従来のＨＰＳよりも適切に低下させること、しかも、固体燃料の分布についても当該核部分と外層部分とに対して適切に配分・制御することが、上記望ましい擬似粒子設計の実現にとって重要であるとの知見を得た。
【００１６】
上記外層部分の塩基度調整においては、焼成後における残留核部分の相互間隙領域にカルシウムフェライト主体の結合相が生成するように当該結合相の塩基度が２．０〜４．０程度の範囲内になるようにしてやることが必要である。焼成過程においては通常、外層部分に含まれる固体燃料は全量燃焼させ、ＣａＯ源物質も全量融体化させて、核部分表層領域の構成物質と反応させる。従って、上記結合相の塩基度は、外層部分の量と、焼成過程で融体化反応を起こす核部分表層領域の量とにも影響されてきまる。このような焼成過程の前後における組成的及び量的関係は、他の焼結操業条件によっても影響を受ける。従って、上記に関する定量的条件は、操業する焼結機を用いた試験により把握しておくことができる。
【００１７】
本発明者等は、かかる観点から、擬似粒子の外層部分の塩基度調整について試験すると共に、前述のこの発明で解決すべき課題において述べた通りの「鉱物学的形態及び物理特性」として望ましい性状を備えた焼成塊成鉱を得るための、ＣａＯ分の添加量配分についての条件を検討した。その結果、少なくとも、擬似粒子の核部分に全石灰分添加量の内１０ｍａｓｓ％以下を添加し、残部をその外層部分に添加することが必要であるとの結論を得た。
【００１８】
この発明は、主として上記知見に基づきなされたものであり、その要旨は下記の通りである。
【００１９】
請求項１に係る製鉄用高品位焼成塊成鉱は、事前処理の造粒工程において鉄鉱石及び媒溶剤が含まれた混合原料から調製された核部分と、固体燃料及びＣａＯ源物質を前記核部分の表面に被覆した外層部分とからなる擬似粒子粒子の集合の内、前記核部分の一部が残留しており、当該残留核部分は、多孔質ヘマタイト及び多孔質マグネタイト、並びに、少量のカルシウムシリケート系スラグ及び少量のカルシウムフェライトからなり、そして、当該残留核部分同士の間隙には、焼成過程で生成したカルシウムフェライト融液と少量のオリビン系溶融スラグとの凝固相からなる結合相が形成しており、前記結合相中のＣａＯ含有率（ｍａｓｓ％）とＳｉＯ ₂ 含有率（ｍａｓｓ％）との比（ＣａＯ／ＳｉＯ ₂ ） _bond. は、前記残留核部分中のＣａＯ含有率（ｍａｓｓ％）とＳｉＯ ₂ 含有率（ｍａｓｓ％）との比（ＣａＯ／ＳｉＯ ₂ ） _rem-gr. よりも大きく、下記（１）及び（２）式の関係：
２．０≦（ＣａＯ／ＳｉＯ ₂ ） _bond. ≦４．０・・・・・・（１）
０．３≦（ＣａＯ／ＳｉＯ ₂ ） _rem-gr. ≦０．９・・・・・・（２）
を満たし、且つ、前記残留核部分と前記結合相とからなる前記焼成塊成鉱中の、ＣａＯ含有率（ｍａｓｓ％）とＳｉＯ ₂ 含有率（ｍａｓｓ％）との比（ＣａＯ／ＳｉＯ ₂ ） _PROD. は、１．５〜２．０の範囲内にあり、前記結合相は、前記残留核部分の内部への浸透が抑制されている形態を呈していることに特徴を有するものである。
【００２０】
請求項２記載に係る製鉄用高品位焼成塊成鉱は、請求項１記載の発明において、前記残留核部分の構成物質として、ヘマタイト、マグネタイト、並びに、少量のカルシウムシリケート系スラグ及び少量のカルシウムフェライトに加えて、少量のマグネシオフェライトが当該残留核部分自体の結合強化相として付加されていることに特徴を有するものである。
【００２３】
請求項３記載に係る製鉄用高品位焼成塊成鉱は、請求項１または請求項２に記載の発明において、前記焼成塊成鉱中のＳｉＯ₂含有率が、４．８ｍａｓｓ％以下であることに特徴を有するものである。
【００２４】
請求項４記載に係る製鉄用高品位焼成塊成鉱は、請求項１〜３のいずれかに記載の発明において、前記焼成塊成鉱中の全鉄含有率が、５８ｍａｓｓ％以上であることに特徴を有するものである。
【００２５】
請求項５記載に係る製鉄用高品位焼成塊成鉱は、請求項１〜４のいずれかに記記載の発明において、前記焼成塊成鉱中のＭｇＯ含有率が、０．５〜２．０ｍａｓｓ％の範囲内であることに特徴を有するものである。
【００２６】
請求項６記載に係る製鉄用高品位焼成塊成鉱の製造方法は、鉄鉱石を主体とする主原料に媒溶剤及び固体燃料を配合し、得られた配合原料を１次ミキサーに装入して混合する。得られた混合原料を造粒機に装入して擬似粒化させ、得られた擬似粒化体を擬似粒子の核部分とし、当該核部分からなる原料に固体燃料及びＣａＯ源物質を配合して、調整原料を得る。得られた調整原料を２次ミキサーで処理して、当該固体燃料及び当該ＣａＯ源物質を前記核部分の表面に付着外装し、前記核部分の表面に外層部分が形成された擬似粒子を調製する。こうして得られた前記擬似粒子を焼結原料として、焼結機へ装入する製鉄用高品位焼成塊成鉱の製造方法であり、次の通り行なう。即ち、前記１次ミキサーに装入する主原料と媒溶剤と固体燃料との配合、及び、前記核部分の表面に外装する前記固体燃料と前記ＣａＯ源物質との配合を、成品焼結鉱中のＳｉＯ₂含有率が、４．８ｍａｓｓ％以下となるように調整し、且つ、前記擬似粒子の核部分中に全固体燃料の２０〜０ｍａｓｓ％の範囲内の固体燃料及び／又は固体燃料を含有する原料を含有させ、そして、前記擬似粒子の外層部分中に当該全固体燃料の残部を全量含有させた擬似粒子を調製する。こうして得られた擬似粒子に焼成処理を施すことに特徴を有するものである。
【００２９】
請求項７記載に係る製鉄用高品位焼成塊成鉱の製造方法は、鉄鉱石を主体とする主原料に媒溶剤及び固体燃料を配合し、得られた配合原料を１次ミキサーに装入して混合する。得られた混合原料を造粒機に装入して擬似粒化させ、得られた擬似粒化体を擬似粒子の核部分とし、当該核部分からなる原料に固体燃料及びＣａＯ源物質を配合して、調整原料を得る。得られた調整原料を２次ミキサーで処理して、当該固体燃料及び当該ＣａＯ源物質を前記核部分の表面に付着外装し、前記核部分の表面に外層部分が形成された擬似粒子を調製する。こうして得られた前記擬似粒子を焼結原料として、焼結機へ装入する製鉄用高品位焼成塊成鉱の製造方法であり、次の通り行なう。
【００３０】
即ち、前記１次ミキサーに装入する主原料と媒溶剤と固体燃料との配合を、前記混合原料中のＣａＯ含有率（ｍａｓｓ％）とＳｉＯ₂含有率（ｍａｓｓ％）との比（ＣａＯ／ＳｉＯ₂）_mix.が、０．３〜０．９の範囲内となるように調整し、且つ、前記核部分の表面に外装する前記固体燃料と前記ＣａＯ源物質との配合を、前記外層部分中のＣａＯ含有率（ｍａｓｓ％）とＳｉＯ₂含有率（ｍａｓｓ％）との比（ＣａＯ／ＳｉＯ₂）_surf.が、１．５〜４．５の範囲内となり、しかも成品焼結鉱中のＣａＯ含有率（ｍａｓｓ％）とＳｉＯ₂含有率（ｍａｓｓ％）との比（ＣａＯ／ＳｉＯ₂）_PRODが、１．５〜２．０の範囲内となるように、前記外層部分に添加するＣａＯ源物質中のＣａＯ分添加量を調整する。こうして得られた擬似粒子に焼成処理を施すことに特徴を有するものである。
【００３１】
請求項８記載に係る製鉄用高品位焼成塊成鉱の製造方法は、鉄鉱石を主体とする主原料に媒溶剤及び固体燃料を配合し、得られた配合原料を１次ミキサーに装入して混合する。得られた混合原料を造粒機に装入して擬似粒化させ、得られた擬似粒化体を擬似粒子の核部分とし、当該核部分からなる原料に固体燃料及びＣａＯ源物質を配合して、調整原料を得る。得られた調整原料を２次ミキサーで処理して、当該固体燃料及び当該ＣａＯ源物質を前記核部分の表面に付着外装し、前記核部分の表面に外層部分が形成された擬似粒子を調製する。こうして得られた前記擬似粒子を焼結原料として、焼結機へ装入する製鉄用高品位焼成塊成鉱の製造方法であり、次の通り行なう。即ち、前記１次ミキサーに装入する主原料と媒溶剤と固体燃料との配合、及び、前記核部分の表面に外装する前記固体燃料と前記ＣａＯ源物質との配合を、成品焼結鉱中のＳｉＯ₂含有率が、４．８ｍａｓｓ％以下となるように調整し、且つ、前記擬似粒子の核部分中に全固体燃料の２０〜０ｍａｓｓ％の範囲内の固体燃料を含有させ、そして、前記擬似粒子の外層部分中に当該全固体燃料の残部を全量含有させる。そして、前記１次ミキサーに装入する主原料と媒溶剤と固体燃料との配合を、前記混合原料中のＣａＯ含有率（ｍａｓｓ％）とＳｉＯ₂含有率（ｍａｓｓ％）との比（ＣａＯ／ＳｉＯ₂）_mix.が、０．３〜０．９の範囲内となるように、且つ、前記核部分の表面に外装する前記固体燃料と前記ＣａＯ源物質との配合を、前記外層部分中のＣａＯ含有率（ｍａｓｓ％）とＳｉＯ₂含有率（ｍａｓｓ％）との比（ＣａＯ／ＳｉＯ₂）_surf.が、１．５〜４．５の範囲内となるようにし、しかも、前記擬似粒子全体のＣａＯ含有率（ｍａｓｓ％）とＳｉＯ₂含有率（ｍａｓｓ％）との比（ＣａＯ／ＳｉＯ₂）_ps-gr.が、１．５〜２．０の範囲内となるように調整する。こうして得られた擬似粒子に焼成処理を施すことに特徴を有するものである。
【００３２】
請求項９記載に係る製鉄用高品位焼成塊成鉱の製造方法は、請求項６〜８のいずれかに記載の発明において、前記１次ミキサーに装入する主原料と媒溶剤と固体燃料との配合、及び、前記核部分の表面に外装する前記固体燃料と前記ＣａＯ源物質との配合を、当該請求項８、９又は１０に記載の配合調整条件に加えて更に、前記擬似粒子中の全鉄含有率が、５８ｍａｓｓ％以上となるように調整する条件を付加することに特徴を有するものである。
【００３３】
請求項１０記載に係る製鉄用高品位焼成塊成鉱の製造方法は、請求項６〜９のいずれかに記載の発明において、前記１次ミキサーに装入する主原料と媒溶剤と固体燃料との配合、及び、前記核部分の表面に外装する前記固体燃料と前記ＣａＯ源物質との配合を、当該請求項６〜９のいずれかに記載の配合調整条件に加えて更に、前記擬似粒子中のＭｇＯ含有率が、０．５〜２．０ｍａｓｓ％の範囲内となるように調整する条件を付加することに特徴を有するものである。
【００３４】
請求項１１記載に係る製鉄用高品位焼成塊成鉱の製造方法は、請求項６〜１０のいずれかに記載の発明において、前記主原料中には、結晶水を４ｍａｓｓ％以上含有する鉄鉱石を、２５ｍａｓｓ％以上配合することに特徴を有するものである。
【００３５】
【発明の実施の形態】
この発明に係る製鉄用高品位焼成塊成鉱の製造方法の特徴は、各種原料及び固体燃料の事前処理方法にある。鉄鉱石を主体とする主原料に媒溶剤及び固体燃料を配合し、得られた配合原料を次の通り事前処理して、擬似粒子を調製する。ここで、この発明で用いる主原料の種類としては、通常使用されているものを使用する。即ち、粉状鉄鉱石或いは多銘柄の粉状鉄鉱石を混合して作ったいわゆるＢ粉及び返鉱等を使用する。また適宜、雑原料として製鉄所で発生するダスト、即ち鉄分を含有するダストや、ニッケルスラグ、ＭｇＯを含有するフラックス等を使用する。媒溶剤としては、ＣａＯ源物質は添加するが、蛇紋岩や珪石等のＳｉＯ₂源物質は、低ＳｉＯ₂焼結鉱製造に不利であるから、通常の鉱石需給条件下においては、使用しないこととする。
【００３６】
図１に、この発明に係る焼成塊成鉱を製造するために望ましい製造工程の一例を説明する概略フロー図を示す。主原料として粉鉄鉱石１及び返鉱２を、適宜雑原料として製鉄所発生ダスト３等を、媒溶剤として生石灰４、又は、生石灰４とマグネサイト５とを、そして、固体燃料として粉コークス６を、それぞれのホッパーから所定の重量割合で切り出し、水分３０を添加して１次ミキサー７において混合・処理し、混合原料８を調製する。マグネサイト５の替わりにドロマイトを用いてもよい。次いで混合原料８を造粒機９へ装入する。
【００３７】
造粒機９としては、皿型造粒機（ディスクペレタイザー）を用いるのが望ましいが、ドラムミキサーの内、滞留時間の長いものを用いることもできる。水分２５を添加して加湿された混合原料８を造粒機９で、粒径が３〜１２ｍｍ程度の範囲内に入る不規則形状体に擬似粒化して、擬似粒子の核部分１０を調製する。造粒機９としてディスクペレタイザーを用いれば、核部分１０を効率的に調製することができる。得られた核部分１０に、固体燃料として粉コークス１１と、ＣａＯ源物質として粉石灰石１２、消石灰１３又は生石灰１４とを配合し、水分２６を添加して加湿された調整原料１５を調製する。こうして得られた調整原料１５を２次ミキサー１６で処理し、核部分１０の表面に固体燃料及びＣａＯ源物質が外装された擬似粒子１７を調製する。
【００３８】
図２は、この発明に係る焼成塊成鉱を製造する過程において、上記のように事前処理を施された擬似粒子１７が焼成されて本発明の焼結ケーキ３が得られる状況を、ＣａＯ−Ｆｅ₂Ｏ₃−ＳｉＯ₂の平衡状態図を用いて説明する模式図である。
【００３９】
先ず、事前処理を施された擬似粒子１７の構造を説明する。擬似粒子１７（図２の（ａ）参照）は、核部分１０と外層部分２７とからなる。そして、核部分１０は、ヘマタイト及び少量の脈石、並びに少量の粉コークス１１及び生石灰４と適宜少量添加されたマグネサイト５等とのＭｇＯ含有フラックスからなる。核部分１０は、低塩基度組成物である。そして、外層部分２７は、粉コークス１１と、粉石灰石１２又は消石灰１３、及び適宜生石灰１４を添加したＣａＯ源物質とからなる高塩基度組成の混合粉でなる。
【００４０】
こうして事前処理を施されて調製された擬似粒子１７を焼結機１８へ搬送し、これを焼結原料として原料装入装置１９により焼結機１８のパレット２０内へ、厚さ５００〜７００ｍｍ程度の層状に充填装入する。原料装入装置１９には、焼結原料の粒度偏析装入機構２１を装備し、底面がグレートで構成されたパレット２０に装入される焼結原料、即ち擬似粒子１７は、偏析装入機構２１により、下層から上層に向かって細粒から粗粒に変化する粒度分布となるように調整する。焼結機１８は無端移動グレート式焼結機であって、パレット２０内に形成された焼結原料層２２の上面に点火し、擬似粒子１７は乾燥、加熱、溶融、冷却過程を経て焼成塊成鉱の焼結ケーキ２３を得る。得られた焼結ケーキ２３を冷却、破砕、篩分けして所定粒度の焼結鉱、例えば４ｍｍ〜５０ｍｍのものを成品焼結鉱２４とし、高炉装入用原料にする。一方、−４ｍｍのものは返鉱２として焼結鉱製造原料にリターンする。
【００４１】
上記工程において、主原料と媒溶剤との配合においては、１次ミキサー７で得られる混合原料８中のＣａＯ成分の含有率（ｍａｓｓ％）とＳｉＯ₂成分の含有率（ｍａｓｓ％）との比（ＣａＯ／ＳｉＯ₂）_mix.、即ち、混合原料８の塩基度が、０．３〜０．９の範囲内に入るように調整し、更に、この混合原料８中には、本焼成塊成鉱用の製造工程で原料中に添加する全固体燃料の内、２０〜０ｍａｓｓ％の範囲内の固体燃料を配合調整する。固体燃料としては、例えば前述した通り、粉コークス６を用いるのが望ましい。その他の固体燃料として、粉状チャー、微粉炭、粉状石油コークス等がある。
【００４２】
上記混合原料８を調製する工程での各種原料及び固体燃料の配合調整における第１の特徴は、焼成塊成鉱の成分組成の内、ＳｉＯ₂含有率を４．８ｍａｓｓ％以下に制限するようにし、且つ、混合原料８に添加する固体燃料（ここでは粉コークス６）の全固体燃料中の比率を２０〜０ｍａｓｓ％の範囲内と、相当に低くしていることであり、その比率は０であってもよい。即ち、混合原料８中には一切固体燃料を添加しなくてもよいということである。これに対して、後工程で混合原料８が造粒されて得られる、核部分１０の表面に外装されて形成される外層部分２７には、全固体燃料の残部の全量を、即ち全固体燃料の８０〜１００ｍａｓｓ％の範囲内で含有させることにある。
【００４３】
そして、第２の特徴は、混合原料８の塩基度を０．３〜０．９の範囲内と相当に低くし（いわば「低塩基度ライン」を構成し）、これに対して、後工程で混合原料８が造粒されて得られる、核部分１０の表面に外装されて形成される外層部分２７の塩基度は、１．５〜４．５の範囲内と相当に高い値に調整し（いわば「高塩基度ライン」を構成し）、しかも擬似粒子（即ち上記核部分１０の表面に外層部分が被覆された造粒物）１７の塩基度を、焼成後の塊成鉱（焼結ケーキ２３）の塩基度が１．５〜２．０の範囲内となるように、ＣａＯ分の添加量を調整することにある。焼成過程においては、焼成前擬似粒子１７の核部分１０の表層の一部が溶融して、焼成後の結合相２９（図２の（ｃ）参照）の一部を構成する。こうして、焼成塊成鉱の結合相２９の塩基度は、２．０〜４．０の範囲内となるようにする。
【００４４】
結合相２９の塩基度が、２．０〜４．０の範囲内となる成分組成のＣａＯ−Ｆｅ₂Ｏ₃−ＳｉＯ₂３元系平衡状態図（図２、（ｂ）参照）上の領域は、ＣａＯ濃度軸上の６７〜８０ｍａｓｓ％の範囲であって、その下限濃度６７ｍａｓｓ％とＦｅ₂Ｏ₃１００ｍａｓｓ％の点とを結ぶ直線と、その上限濃度８０ｍａｓｓ％とＦｅ₂Ｏ₃１００ｍａｓｓ％の点とを結ぶ直線とで囲まれた３角形領域内部に相当する。この領域内のＦｅ₂Ｏ₃コーナーよりに存在するβ相領域でカルシウムフェライト系初期融液（溶融温度＜約１２００℃）を生成させる。これにより、焼成後の焼結ケーキ２３に対して、残留核部分２８同士の強固な結合機能を与えると共に、当該結合相２９に被還元性に比較的優れた特性を確保させる。
【００４５】
なお、焼結ケーキ２３の塩基度１．５〜２．０の範囲内となる成分組成のＣａＯ−Ｆｅ₂Ｏ₃−ＳｉＯ₂３元系平衡状態図（図２、（ｂ）参照）上の領域は、同じように、ＣａＯ濃度軸上の６０〜６７ｍａｓｓ％の範囲であって、Ｆｅ₂Ｏ₃１００ｍａｓｓ％の点とを結ぶ直線とで囲まれた３角形領域内部に相当する。
【００４６】
この発明においては、上記の通り、擬似粒子１７の核部分１０及び外層部分２７に対する固体燃料の配分調整及び塩基度調整を行ない、しかも、擬似粒子全体に含まれるＳｉＯ₂含有率を低く抑えることにより、焼成塊成鉱の焼結ケーキ２３として、下記特徴を有するものが得られる。
【００４７】
図２（ａ）〜（ｃ）により、擬似粒子１７が焼成されて焼結ケーキ２３が得られる状況を説明する。擬似粒子１７は、外層部分２７に粉コークスの大半が含まれており、これが焼結工程で、吸引空気中の酸素ガスで燃焼される。擬似粒子１７内への酸素の拡散は遅いので、外層部分２７にある固体燃料（粉コークス）の燃焼によって擬似粒子は短時間で強熱され、高温短時間焼結のパターンで焼成される。従って、核部分１０は、図２中の一点鎖線ｌ₁の経路にしたがって、一部分のみが溶融して図２の（ｂ）に示すマグネタイト相となり、外層部分２７に移行して結合相２９に溶け込み、残部はヘマタイトとマグネタイトとになって、図２の（ｃ）に示す焼結ケーキ２３の残留核部分２８になる（一点鎖線ｌ₁’）。一方、外層部分２７は、強熱されるので、図２中の一点鎖線ｌ₂の経路にしたがって、全体が溶融して図２の（ｂ）に示すβ相となり、上記核部分の一部溶融によるマグネタイト相を吸収して、カルシウムフェライトと、局所的に塩基度の低い部分は少量のオリビン系スラグになり、これら両者が図２の（ｃ）に示す結合相２９になる。結合相２９は上述した通り、短時間で生成した後急速に冷えるので、残留核部分２８内部への融液浸透は抑制される。こうして、残留核部分２８は、多孔質ヘマタイトと多孔質マグネタイトとからなる状態が確保される。よって、優れた被還元性を示すことになる。
【００４８】
ここで、焼結ケーキ２３のＳｉＯ₂含有率としては、４．８ｍａｓｓ％以下であることが望ましい。ＳｉＯ₂含有率が、４．８ｍａｓｓ％を超えると、残留核部分２８中のスラグ成分（カルシウムシリケート系スラグ）及び結合相中のオリビン系スラグの量が限度以上に増加し、焼結鉱の被還元性を高水準に維持できなくなる。
【００４９】
上記のようにして、本発明で得られる焼成塊成鉱の鉱物学的形態及び物理特性として、内部に形成される多数の残留核部分２８については、固体燃料配合量が少なく、且つ低ＳｉＯ₂含有率であって低塩基度であるため、多孔質ヘマタイトと多孔質マグネタイトとが主体をなし、カルシウムシリケート系スラグとカルシウムフェライトとが少量生成するに留まる。そして、残留核部分の主体を構成する多孔質ヘマタイト及び多孔質マグネタイトは、拡散結合主体の結合力によりその強度維持に寄与する。
【００５０】
一方、多数個が形成されたこの残留核部分２８の間隙には、焼成過程で生成したカルシウムフェライト融液（ＣａＯ・Ｆｅ₂Ｏ₃及びＣａＯ・２Ｆｅ₂Ｏ₃）と少量のオリビン系溶融スラグ（２（Ｆｅ，Ｃａ）Ｏ・ＳｉＯ₂）との凝固相からなる結合相２９が形成され、この結合相２９は、残留核部分２８の内部への浸透が抑制された形態を呈する。得られる焼結ケーキ２３はこのような形態を呈するので、多数の残留核部分２８を取り巻く結合相２９が、内部の拡散結合主体による多孔質ヘマタイト及び多孔質マグネタイト部分の強度維持を補完して、局部的に強度劣化部分が生じていても強固に被覆保護する。ここで、多孔質ヘマタイト及び多孔質マグネタイトを被覆する結合相２９の主体はカルシウムフェライトであり、これは被還元性が比較的優れている。そして、上記主原料、媒溶剤及び固体燃料の配合条件が満たされているので、この結合相２９の形成量に関しては、残留核部分２８同士の強固な結合と、衝撃や摩耗による焼結ケーキ２３の表面に対する外力からの保護作用を発揮し得るに十分なだけの量を確保することができる。但し、擬似粒子１７の外層部分２７の塩基度を、１．５〜４．５と相当に高い値に調整してあり、且つ、上記の高温短時間焼結であるため、残留核部分２８の最外層部中のカルシウムフェライトあるいは微量のオリビン系溶融スラグが、残留核部分２８の内部に浸透する量は少なく、しかもＳｉＯ₂含有率を低く調整してあるので、残留核部分自体のスラグ量も少なく、焼結ケーキ２３の被還元性は優れた水準に維持される。
【００５１】
上記混合原料８の塩基度調整において用いるＣａＯ源物質としては、石灰石を用いず、生石灰４を用いるのが望ましい。石灰石は焼成過程で吸熱反応により分解熱を吸収するので、配合すべき固体燃料の増加につながる。その点、生石灰４は有利であり、また造粒過程でバインダー機能を発揮するから造粒性向上に有利となるからである。また、生石灰４と共にマグネサイト８を用いると、マグネタイト及びマグネシオフェライト（（Ｍｇ，Ｆｅ）Ｏ・Ｆｅ₂Ｏ₃）の生成を助長し、結果的に耐還元粉化性が改善される。ここで、ＭｇＯ源物質としてドロマイトを用いると、ＭｇＯ成分がマグネタイト中のＦｅＯと十分に置換しないが、マグネサイトを用いれば、これが解消され、またマグネサイトのＳｉＯ₂含有率が僅少であり（１ｍａｓｓ％以下）、Ａｌ₂Ｏ₃含有率も微小だからである。
【００５２】
この発明においては、主原料中の鉄鉱石として、結晶水含有率が４ｍａｓｓ％程度以上含有される鉄鉱石（本願明細書において、「高結晶水鉱石」という）を適宜用いる。但し、高結晶水鉱石の主原料中配合率が、２５ｍａｓｓ％以上になると、この発明の焼成塊成鉱の製造においても、従来の焼結鉱製造におけると同様、擬似粒子の造粒性の劣化、及び溶融・焼結過程における局部的な過溶融部分と未焼部分との発生や通気性の劣化等による、成品焼結鉱歩留の低下や生産性低下を招く。一方、高結晶水鉱石の焼結鉱への大量使用は、今後回避困難な情勢にある。従って、この発明においても、高結晶水鉱石の多量使用技術が必要である。その際の高結晶水鉱石使用技術は、当該高結晶水鉱石の物性特徴に応じた事前処理を施すことを付加するものとする。例えば、結晶水を予め除去する事前処理や、逆に予め十分に吸水させる事前処理が考えられ、また、これらを粒度に注目してその処理方法を変えることも考えられる。
【００５３】
次に、混合原料８の各構成体粒子の望ましい粒度分布は、鉄鉱石については、−０．０４ｍｍの微粉部分割合が、５０〜８０ｍａｓｓ％程度を占める粉鉄鉱石と、１〜−８ｍｍの粗粒部分割合が、３０〜５０ｍａｓｓ％程度を占める粒度−８ｍｍ程度の粗粒鉄鉱石とからなり、その粉鉄鉱石と粗粒鉄鉱石との重量構成比率が３０：７０から７０：３０程度までの範囲内に入るようにするのが望ましい。こうすることにより、次の造粒工程において、粗粒鉄鉱石が核粒子となり、この表面に粉鉄鉱石が付着粒子となって充填密度の大なる不規則形状体である、擬似粒子の核部分の形成が促進される。
【００５４】
固体燃料として、製鉄所のコークス炉で発生するＣＤＱ粉（コークス乾式消火設備粉）等のコークス粉６、１１を用いれば、粒度構成が微粉であることから有利である。
【００５５】
この発明による焼成塊成鉱では、全鉄含有率を５８ｍａｓｓ％以上に制限する。その理由は、成品焼結鉱を高炉原料として装入するに当たり、銑鉄１ｔ当たりの製造に要する高炉装入主原料の重量（以下、「高炉主原料比」という）を、所定値以下に低くして、高炉スラグ比を低下させ、高炉燃料比を減らすためである。高炉装入主原料は、一般に処理鉱と塊鉱石とからなり、処理鉱の主なものは、焼結鉱とペレットである。わが国においては、多くの高炉において処理鉱として焼結鉱を主体とし、残部を購入ペレットでまかなっており、一部の高炉においては処理鉱として、自社製造のペレットを使用している。わが国の上記多くの高炉で使用されている焼結鉱の主原料に占める割合は、７０〜８５ｍａｓｓ％程度である。このように高炉装入主原料中に多くを占める焼結鉱の鉄分含有率を高くすることは、高炉主原料比を減らし、その結果スラグ比を低下させるのに極めて効果的である。わが国においては、高炉主原料比は、凡そ１６００〜１６５０ｋｇ／ｔ程度であり、焼結鉱中の全鉄含有率は、凡そ５７ｍａｓｓ％弱〜５９ｍａｓｓ％弱である。
【００５６】
この発明による焼成塊成鉱では、ＭｇＯ成分の望ましい含有率は、０．５〜２．０ｍａｓｓ％の範囲内とし、残留核部分に含有させる。その理由は、当該ＭｇＯ含有率が、０．５ｍａｓｓ％よりも低いと、マグネタイト及びマグネシオフェライトの生成量が少なく耐還元粉化性が悪化し、一方、当該ＭｇＯ含有率が２．０ｍａｓｓ％を超えて含有させると、緻密質マグネタイトの影響で、成品焼結鉱の被還元性を悪化させるからである。
【００５７】
【実施例】
この発明を実施例により更に説明する。
【００５８】
（試験１）
図１に示した焼成塊成鉱の製造フローに準じて、本発明の製鉄用高品位焼成塊成鉱を製造した。主原料として粉鉄鉱石１及び返鉱２を、媒溶剤として生石灰４及びマグネサイト５を、そして固体燃料として粉コークス６をそれぞれ所定量切出して配合し、得られた配合原料を１次ミキサー７で混合し、混合原料８を得た。次いで、混合原料８を造粒機９に装入し、水分２５を添加して造粒処理を行なった。造粒機９としてディスクペレタイザーを用い、混合原料８から擬似粒化体を調製した。擬似粒化体は擬似粒子１７の核部分１０となるものである。ディスクペレタイザーから排出された核部分１０に粉コークス１１及び粉石灰石１２を配合し、水分２６を添加して調整原料１５とした。調整原料１５を２次ミキサー１６で処理して擬似粒子１７を調製した。擬似粒子１７の核部分の表面には粉石灰石１２と粉コークス１１とが外装されて外層部分が形成される。擬似粒子１７を焼結機１８に装入し、焼成塊成鉱の焼結ケーキ２３を製造した。
【００５９】
ここで使用した粉鉄鉱石１、返鉱２、生石灰４、マグネサイト５、その他の成分組成を表１に示し、粉コークス６の工業分析値を表２に示す。なお、使用した粉鉄鉱石１は、−４４μｍの微粉部分の割合が４０ｍａｓｓ％以上を占める鉱石を４０〜７０ｍａｓｓ％程度と、ペレットフィードを２０〜３０ｍａｓｓ％程度使用した。
【００６０】
【表１】

【００６１】
【表２】

【００６２】
本発明に係る焼成塊成鉱の製造試験として、１次ミキサー７に装入する粉鉄鉱石１及び返鉱２からなる主原料、生石灰４、及び粉コークス６並びにマグネサイト５からなる配合原料を、その塩基度目標値を０．５に設定して、０．３〜０．９の範囲内に入るように調整した。ここでの粉コークス６の添加量としては、全粉コークス添加量の内、２０ｍａｓｓ％以下とし、種々の水準に設定した。この配合原料を混合して混合原料８とし、水分６〜８ｍａｓｓ％程度でディスクペレタイザーで粒度約３〜１２ｍｍ程度の不規則形状体に擬似粒化して、擬似粒子１７の核部分１０を調製した。
【００６３】
次いで、造粒された核部分１０に粉コークス１１と粉石灰石１２とを外装被覆して、擬似粒子１７を次の通り調製した。
【００６４】
ここで、外装被覆の粉コークス１１と粉石灰石１２とを、その外装部分の塩基度目標値を、焼成後において２．５におき、２〜４の範囲内に入るように、しかも、焼成後における塊成鉱の平均塩基度の目標値を１．７５におき、少なくとも１．５〜２．０の範囲内に入るように、核部分１０の原料に対する粉コークス１１と粉石灰石１２との添加量及び両者の配合比率を調整して、調整原料１５を調製した。ここでの粉コークス１１の添加量としては、全粉コークス添加量の内、上記配合原料８に添加した粉コークス６を差し引いた残部の全量を添加した。そして、上述した焼成後における塊成鉱のＳｉＯ₂含有率が４．８ｍａｓｓ％以下、全Ｆｅ含有率が５８ｍａｓｓ％以上、且つＭｇＯ含有率が０．５〜２．０ｍａｓｓ％の範囲内に入るように調整した。こうして得られた調整原料１５を２次ミキサー１６で処理して、粒径約４〜１５ｍｍの擬似粒子１７を調製した。
【００６５】
なお、上記本発明の範囲内の試験（実施例）においては、鉄鉱石１の銘柄別配合比率において、高結晶水鉱石の主原料に占める割合が２５ｍａｓｓ％以上となるように調整した。
【００６６】
上記条件で調製された擬似粒子１７を焼結機１８へ搬送し、装入ホッパーへ貯留せずに、コンベアベルト型の原料装入装置１９により焼結機１８のパレット２０内へ装入した。ここで、装入ホッパーへ焼結原料を貯留しない理由は、核部分１０に含ませたバインダー機能も有する生石灰添加量を、当該部分の塩基度を０．３〜０．９の範囲内という低い範囲に抑えたのに伴い少なくしている。これを考慮して擬似粒子１７の崩壊をできるだけ無くすためである。擬似粒子１７即ち焼結原料の装入は、粒度偏析装入機構２１により、パレット２０内の焼結原料層２２の上層部に細かい粒度焼結原料が分布し、下層部にいくにつれて粗い粒度の焼結原料が分布するようにした。従って、焼結原料層２２の層厚方向の粉コークス１１の含有率は、細粒側原料が分布する上層部において相対的に高く、粗粒側原料が分布する下層部において相対的に低くなる。
【００６７】
なお、これは、擬似粒子１７の核部分に含ませた粉コークス６は擬似粒子１７の大きさよらず、ほぼ同じ含有率になる。これに対して、核部分に外装して外層部分に含ませた粉コークス１１は、核部分の表面にほぼ均一に付着するので、擬似粒子１７の比表面積（単位質量に対する表面積）当たりの粉コークス１１の量は、細粒側原料に多く、粗粒側原料に少なくなるからである。
【００６８】
こうして、層厚約６００ｍｍに充填装入した焼結原料２２を、ドワイトロイド式焼結機１８で焼成した。焼成時の原料層内の雰囲気圧力は、焼成・冷却ゾーンで−４５０ｍｍ程度の負圧で吸引した。このように低い負圧条件で操業できるのは、原料層内の通気性が良好に維持されているためである。
【００６９】
上記実施例に対して、本発明の範囲外の試験（比較例）として、実施例と同じく図１に示した概略フローの製造工程により焼成塊成鉱を製造した。但し、比較例においては、同図において核部分１０の原料に造粒する前の混合原料８の原料配合、及びその核部分１０の表面を外装被覆するための原料配合において、下記のように、実施例における配合とは、次の２点において異なった調整を行なった。第１点は、塩基度に関して、焼成後における塊成鉱の平均塩基度の目標値を１．５未満（比較例１）、又は、２．０超え（比較例２）としたこと、そして、第２点は、それぞれの平均塩基度の場合において、焼成後における外装部分相当領域、即ち、焼成ケーキ２３における結合相２９（図２、（ｃ）参照）の塩基度を２〜４の範囲外とし、且つ、焼成ケーキ２３における残留核部分（図２、（ｃ）参照）の塩基度を０．３〜０．９の範囲外としたことである。
【００７０】
実施例及び比較例１及び２の操業試験で製造された成品焼結鉱の成分組成、鉱物学的組織、成品品質及び操業成績を、表３に示す。ここで表３のミクロ組織は研磨試料を反射顕微鏡で観察した結果であり、厳密な意味での定量評価は困難であるが、その組織の特徴を示すものである。
【００７１】
【表３】

【００７２】
本発明による焼結鉱の成分組成については、ＳｉＯ₂含有率、塩基度（ＣａＯ／ＳｉＯ₂）、全鉄（Ｔ．Ｆｅ）含有率、及びＭｇＯ含有率の全てにわたり、本発明の望ましい範囲内にあり、また、鉱物学的組織観察結果においても、特に、被還元性に優れた焼結鉱の組織を呈している。成品焼結鉱の品質特性は、冷間強度ＴＩ_+5mm、還元率ＲＩ、及び耐還元粉化指数ＲＩのいずれにおいても優れている。一方、焼結操業成績は、粉コークス原単位、成品焼結鉱の歩留、及び焼結鉱生産率のいずれにおいても優れている。
【００７３】
（試験２）
上記試験１の実施例並びに比較例１及び２において製造された焼成塊成鉱を高炉原料として用い、高炉操業試験を行なった。高炉操業は、内容積３４４３ｍ³の高炉において、送風温度１２００℃、酸素富化率３．２％、調湿蒸気２５．３ｇ／Ｎｍ³、スラグ目標塩基度１．２２、微粉炭吹込み比１５０〜２００ｋｇ／ｔ設定、溶銑目標温度１５００℃の条件で操業した。
【００７４】
この操業試験で得られた高炉の操業成績を、表４に示す。
【００７５】
【表４】

【００７６】
本発明による焼結鉱を使用した実施例の高炉操業においては、高炉装入の主原料比（銑鉄１ｔを製造するのに要する鉱石の重量）がほぼ１６００ｋｇ／ｔ以下となり、高炉スラグ比がほぼ２５０ｋｇ／ｔ以下になり、こうして、高炉燃料比は、コークス比３０６ｋｇ／ｔと、微粉炭吹込み比２０３ｋｇ／ｔとの和である、ほぼ５０９ｋｇ／ｔという低燃料比が達成された。
【００７７】
【発明の効果】
この発明によれば、既存の製造設備を利用して、極めて高品質で歩留に優れた焼成塊成鉱を製造することができる。また、本発明の焼成塊成鉱の製造方法によれば、焼結鉱の生産性が向上する。そして、この焼結鉱を高炉装入原料として用いることにより、高炉スラグ比は低減し、高炉における燃料比が低下する。また、その結果、製鉄所における二酸化炭素の排出量が減り、環境改善にも寄与する。このような製鉄用高品位焼成塊成鉱及びその製造方法を提供することができ、工業上有用な効果がもたらされる。
【図面の簡単な説明】
【図１】この発明に係る焼成塊成鉱を製造するために望ましい製造工程の一例を説明する概略フロー図である。
【図２】この発明に係る焼成塊成鉱を製造する過程において、擬似粒子が焼成されて焼結ケーキが得られる状況を、平行状態図を用いて説明する模式図である。
【符号の説明】
１鉄鉱石
２返鉱
３ダスト
４生石灰
５マグネサイト
６粉コークス
７１次ミキサー
８混合原料
９造粒機
１０（擬似粒子の）核部分
１１粉コークス
１２粉石灰石
１３消石灰
１４生石灰
１５調整原料
１６２次ミキサー
１７擬似粒子
１８焼結機
１９原料装入装置
２０パレット
２１粒度偏析装入機構
２２焼結原料層
２３焼結ケーキ
２４成品焼結鉱
２５水分
２６水分
２７（擬似粒子の）外層部分
２８（焼結ケーキの）残留核部分
２９（焼結ケーキの）結合相
３０水分[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a calcined agglomerated ore as a raw material for iron making used in a blast furnace and a method for producing the same, and in particular, a blast furnace operation in which quality is high and quality is high and pulverized coal is blown in large quantities as a substitute for coke. The invention relates to a calcined agglomerate suitable as a raw material for charging a blast furnace during a blast furnace operation for reducing the fuel ratio and a method for producing the same.
[0002]
[Prior art]
In steelworks having a blast furnace, conventionally, a large amount of gas generated in the blast furnace has been secured as a fuel supply source to the entire steelworks, contributing to an appropriate energy balance in the steelworks. However, the use of the above-mentioned combustible gas is simultaneously CO₂Accompanied by the occurrence of Therefore, CO in steelworks₂From the viewpoint of contributing to environmental improvement by reducing the generation amount, it is important to reduce the generation amount of the above-mentioned combustible gas by reducing the fuel ratio in the blast furnace in the future desirable blast furnace operation at steelworks. Become.
[0003]
Some of the factors that reduce and prevent the reduction of gas generated in a blast furnace are intricately related to each other, but especially in relation to recent important development technologies, a large amount of pulverized coal is injected into the blast furnace. Operation, low SiO of sintered ore as raw material for blast furnace₂The reaction operation factor implemented in each of the sinter production process and the charge distribution control method to the blast furnace corresponds to it.
[0004]
Operation of large quantity of pulverized coal injection into blast furnace and low SiO₂The sinter production technology is as follows from the viewpoint of increasing or decreasing the fuel ratio in the blast furnace, and from the viewpoint of increasing or decreasing the amount of gas generated.
[0005]
In order to cope with the depletion of coking coal for coke, the operation of large-scale pulverized coal injection into the blast furnace is aimed at reducing the coke ratio with the aim of substituting coke with pulverized coal, mainly cheap non-coking coal. The goal is to reduce costs in blast furnaces and coke ovens by reducing the operating load of coke ovens and extending the life of the furnaces. However, the coke ratio is reduced by a large amount of pulverized coal injection, but on the other hand, the amount of gas generated increases as the amount of pulverized coal injection increases, and in the pulverized coal injection operation compared to the all coke operation, The heat flow ratio (solid heat capacity / gas heat capacity) decreases, and the air permeability and liquid permeability in the blast furnace deteriorate. In addition, the gas flow distribution in the blast furnace deteriorates as the amount of generated gas increases, and as a result, the fuel ratio in the blast furnace tends to increase.
[0006]
Low SiO₂The purpose of the production of sintered ore is to improve the reducibility in the blast furnace, improve the ventilation and liquid permeability in the furnace, and lower the blast furnace slag ratio. However, with the intention of lowering the blast furnace fuel ratio, basicity (CaO / SiO₂) When the sinter blending ratio is increased under certain conditions, in order to match the target basicity of the blast furnace slag, which is much lower than the basicity of the sinter,₂System addition is required. As a result, low SiO₂Despite the use of sintered ore, the slag ratio reduction effect of the blast furnace is dulled.
[0007]
In view of the above circumstances, the present inventors have made use of the recent development technology described above, while also economically reducing the fuel ratio in the blast furnace, and reducing the CO ratio in the steelworks.₂We decided to aim to establish blast furnace operation technology that could contribute to environmental improvement by reducing the amount of generation.
[0008]
Therefore, the present inventors have further reduced the slagging component composition in the sinter occupying about 70 to 85 mass% in the blast furnace charge as the direction of reducing the fuel ratio in the blast furnace, By further improving the high-temperature properties, the stable operation of the blast furnace is ensured while maintaining a high level of pulverized coal injection to the blast furnace without impairing the ventilation and liquid permeability of the blast furnace. The purpose was to reduce the fuel ratio.
[0009]
Looking at the conventional sinter ore production technology from the above viewpoint, the sintered agglomerate disclosed in Japanese Patent Publication No. 2-4658, etc. There is something about the method. These techniques are related to a new type of calcined agglomerated so-called HPS (Hybrid Pelletized Sinter). This HPS is disclosed, for example, in Japanese Patent Publication No. 2-4658 as follows. That is, the main raw materials are fine iron ore containing fine powder of a predetermined particle size at a predetermined ratio and coarse iron ore containing other predetermined particle diameter of coarse particles at another predetermined ratio. It mix | blends with a predetermined | prescribed ratio, adds a solvent and mixes and granulates. The surface of pseudo particles (mini-pellets) formed with coarse iron ore as a core is coated with powdered fuel such as powdered coke to prepare pellets with a particle size of 3 to 12 mm, which are fired with a sintering machine. Thus, a calcined agglomerated mineral is obtained.
[0010]
In the obtained agglomerated ore, a part of the core part of the original pseudo-particle (mini-pellet) remains, and a large number of the residual core parts lump together, and a calcium ferrite phase is formed on the outer layer part of each residual core part. A phase composed of a small amount of slag phase is formed, and this phase forms a bonded phase that bonds the respective remaining core parts to each other, and each residual core part has a porous form.
[0011]
[Problems to be solved by the invention]
As described above, the HPS has a porous form in which a residual core portion (a part of the core portion of the original pseudo particle (mini-pellet) remains), and a gap between the residual core portions includes a calcium ferrite phase. A bonded phase composed of a small amount of slag phase is formed. Moreover, SiO in HPS₂The content is at a low level. As a result, as a blast furnace charging raw material, air permeability and liquid permeability in the furnace are secured, contributing to high productivity and stable operation of the blast furnace.
[0012]
However, while maintaining the advantages of HPS quality and productivity, etc., it will appropriately cope with the future supply trend of iron ore and coking coal, and suppress the increase in equipment and operating costs, and the manufacturing cost of hot metal In order to reduce the fuel ratio in the blast furnace and reduce the gas generated in the blast furnace (blast furnace gas) without increasing the slag, the amount of slag generated in the blast furnace operation, that is, blast furnace slag It is important and effective to reduce the ratio and reduce the slag sensible heat. Based on this idea, the present inventors have noted that it is necessary to improve the design of pseudo particles to be prepared in the pretreatment step of the sintering raw material in order to further improve the conventional HPS.
[0013]
Thus, the problem of the present invention is that the mineralized morphology and physical properties of the calcined agglomerate include a large number of particulate core parts mainly composed of iron oxide and porous, and the particulate core parts are A necessary minimum amount of a binder phase that can maintain sufficient strength is formed in the gap while complementing the low strength of the aggregate of the porous core portions. Thus, both the reducibility, the resistance to reduction dusting and the cold strength have the same level as or higher than that of conventional HPS, and the slag component composition is further reduced and the high temperature properties are further improved. By obtaining the ore, it is possible to reduce the desired blast furnace slag ratio. An object of the present invention is to devise a technique for preparing pseudo particles composed of a core portion and an outer layer portion to be a binder phase thereof suitable for a sintering raw material capable of firing such agglomerates.
The object is to design pseudo particles having the distribution of iron ore, medium solvent and solid fuel and the composition distribution of the components so that they can be fired and to fire them appropriately.
[0014]
Thus, the object of the present invention is excellent in reducibility, reducing dust resistance and cold strength, excellent in high temperature properties, and excellent in ventilation and liquid permeability in a blast furnace. In addition, while maintaining the characteristics, it is more SiO than conventional HPS.₂Low content, basicity (CaOmass% / SiO₂mass%) and high agglomerates with a high total iron content, and using this as a raw material for blast furnace charging, reducing the blast furnace slag ratio, making the structure porous, and as a result, reducibility An object of the present invention is to provide a high-quality fired agglomerated ore for iron making and a method for producing the same so that improvement of the blast furnace fuel ratio can be achieved.
[0015]
[Means for Solving the Problems]
The inventors of the present invention conducted intensive studies and research on the above-mentioned problems, and obtained the following knowledge. That is, the design of the pseudo-particles for the calcined agglomerate having the above-described characteristics is based on the basicity (CaO content (mass%) / SiO 2 in the sintering raw material that governs the state of formation of the initial melt in the calcining process.₂The content (mass%)) is appropriately distributed and controlled in the core portion and the outer layer portion, that is, 1.5 to 1.8 (CaO: SiO₂= 60: 40 to 64:36) With the boundary as the boundary, the basicity of the core part is made sufficiently small, the basicity of the outer layer part is made sufficiently large, and the basicity of the whole pseudo particle is more appropriate than the conventional HPS In addition, it has been found that it is important for the realization of the desirable pseudo-particle design to appropriately reduce and distribute the solid fuel distribution to the core portion and the outer layer portion.
[0016]
In adjusting the basicity of the outer layer part, the basicity of the binder phase is within the range of about 2.0 to 4.0 so that a binder phase mainly composed of calcium ferrite is formed in the inter-gap region of the residual core part after firing. It is necessary to do so. In the firing process, the solid fuel contained in the outer layer portion is generally burned in whole, the CaO source material is also melted in its entirety, and reacted with the constituent materials in the core surface region. Therefore, the basicity of the binder phase is also affected by the amount of the outer layer portion and the amount of the core partial surface region that causes a melting reaction in the firing process. The compositional and quantitative relationships before and after such a firing process are also affected by other sintering operating conditions. Therefore, the quantitative conditions related to the above can be grasped by a test using the operating sintering machine.
[0017]
From such a viewpoint, the present inventors have tested the basicity adjustment of the outer layer portion of the pseudo particle, and desirable properties as “mineralogical morphology and physical properties” as described in the above-mentioned problems to be solved by the present invention. In order to obtain a calcined agglomerated mineral ore, conditions for adding the CaO content were examined. As a result, it was concluded that it is necessary to add at least 10 mass% of the total amount of lime added to the core part of the pseudo particle and to add the remainder to the outer layer part.
[0018]
The present invention has been made mainly based on the above findings, and the gist thereof is as follows.
[0019]
The high-grade fired agglomerated ore for iron making according to claim 1 includes a core part prepared from a mixed raw material containing iron ore and a medium solvent in a granulation process of a pretreatment, a solid fuel and a CaO source material as the core. A part of the core part remains in the aggregate of the pseudo particle particles composed of the outer layer part coated on the surface of the part, and the residual core part includes porous hematite and porous magnetite, and a small amount of calcium. It consists of a silicate-based slag and a small amount of calcium ferrite, and in the gap between the residual core parts, a bonded phase consisting of a solidified phase of calcium ferrite melt produced in the firing process and a small amount of olivine-based molten slag is formed. And, CaO content (mass%) and SiO in the binder phase ₂ Ratio (CaO / SiO) with content (mass%) ₂ ) _bond. Is the CaO content (mass%) in the residual core part and SiO ₂ Ratio (CaO / SiO) with content (mass%) ₂ ) _rem-gr. Larger than the relationship of the following formulas (1) and (2):
2.0 ≦ (CaO / SiO ₂ ) _bond. ≦ 4.0 (1)
0.3 ≦ (CaO / SiO ₂ ) _rem-gr. ≦ 0.9 (2)
And the CaO content (mass%) and SiO in the calcined agglomerate composed of the residual core portion and the binder phase ₂ Ratio (CaO / SiO) with content (mass%) ₂ ) _PROD. Is in the range of 1.5 to 2.0,The combined phase is characterized in that it has a form in which permeation into the inside of the residual core portion is suppressed.
[0020]
The high-grade fired agglomerated ore for iron making according to claim 2 is the invention according to claim 1, wherein hematite, magnetite, a small amount of calcium silicate slag and a small amount of calcium ferrite are used as constituents of the residual core portion. In addition to the above, a small amount of magnesia ferrite is added as a bond strengthening phase of the residual core portion itself.
[0023]
ClaimItem 3The high-grade fired agglomerate for iron making according to the above list is claimed1 or claim 2In the described invention, SiO in the calcined agglomerated mineral₂The content is characterized by being 4.8 mass% or less.
[0024]
ClaimItem 4The high-grade fired agglomerated ore for iron making according to claim 1~ 3In any one of the inventions, the total iron content in the calcined agglomerate is 58 mass% or more.
[0025]
ClaimItem 5The high-grade fired agglomerated ore for iron making according to claim 1~ 4In any one of the inventions described above, the MgO content in the calcined agglomerate is characterized by being in the range of 0.5 to 2.0 mass%.
[0026]
ClaimItem 6The manufacturing method of the high-grade calcination agglomerated ore for iron manufacture which concerns mounting is mix | blended with the solvent and solid fuel with the main raw material which has iron ore as a main body, and the obtained mixing | blending raw material is charged into a primary mixer, and is mixed. . The obtained mixed raw material is charged into a granulator and pseudo-granulated, and the obtained pseudo-granulated material is used as a core part of the pseudo particle, and a solid fuel and a CaO source material are blended into the raw material composed of the core part. To obtain the adjusted raw material. The obtained adjustment raw material is processed by a secondary mixer, and the solid fuel and the CaO source material are attached to the surface of the core part to prepare pseudo particles having an outer layer part formed on the surface of the core part. . The pseudo-particles thus obtained are used as a sintering raw material to produce a high-quality fired agglomerate for iron making that is charged into a sintering machine. That is, the blending of the main raw material, the solvent and the solid fuel charged in the primary mixer, and the blending of the solid fuel and the CaO source material on the surface of the core part, SiO₂A raw material containing a solid fuel and / or a solid fuel within a range of 20 to 0 mass% of the total solid fuel in the core part of the pseudo particles, the content ratio being adjusted to be 4.8 mass% or less. Then, pseudo particles are prepared in which the entire amount of the remaining solid fuel is contained in the outer layer portion of the pseudo particles. The pseudo-particles thus obtained are characterized by firing treatment.
[0029]
ClaimItem 7The manufacturing method of the high-grade calcination agglomerated ore for iron manufacture which concerns mounting is mix | blended with the solvent and solid fuel with the main raw material which has iron ore as a main body, and the obtained mixing | blending raw material is charged into a primary mixer, and is mixed. . The obtained mixed raw material is charged into a granulator and pseudo-granulated, and the obtained pseudo-granulated material is used as a core part of the pseudo particle, and a solid fuel and a CaO source material are blended into the raw material composed of the core part. To obtain the adjusted raw material. The obtained adjustment raw material is processed by a secondary mixer, and the solid fuel and the CaO source material are attached to the surface of the core part to prepare pseudo particles having an outer layer part formed on the surface of the core part. . The pseudo-particles thus obtained are used as a sintering raw material to produce a high-quality fired agglomerate for iron making that is charged into a sintering machine.
[0030]
That is, the blending of the main raw material, the medium solvent and the solid fuel charged into the primary mixer, the CaO content (mass%) in the mixed raw material and SiO₂Ratio (CaO / SiO) with content (mass%)₂)_mix.Is adjusted to be within the range of 0.3 to 0.9, and the composition of the solid fuel and the CaO source material that is externally packaged on the surface of the core portion is the CaO content in the outer layer portion. (Mass%) and SiO₂Ratio (CaO / SiO) with content (mass%)₂)_surf.Is within the range of 1.5 to 4.5, and the CaO content (mass%) in the sintered product ore and SiO₂Ratio (CaO / SiO) with content (mass%)₂)_PRODHowever, the CaO content addition amount in the CaO source material added to the outer layer portion is adjusted so as to be within the range of 1.5 to 2.0. The pseudo-particles thus obtained are characterized by firing treatment.
[0031]
ClaimItem 8The manufacturing method of the high-grade calcination agglomerated ore for iron manufacture which concerns mounting is mix | blended with the solvent and solid fuel with the main raw material which has iron ore as a main body, and the obtained mixing | blending raw material is charged into a primary mixer, and is mixed. . The obtained mixed raw material is charged into a granulator and pseudo-granulated, and the obtained pseudo-granulated material is used as a core part of the pseudo particle, and a solid fuel and a CaO source material are blended into the raw material composed of the core part. To obtain the adjusted raw material. The obtained adjustment raw material is processed by a secondary mixer, and the solid fuel and the CaO source material are attached to the surface of the core part to prepare pseudo particles having an outer layer part formed on the surface of the core part. . The pseudo-particles thus obtained are used as a sintering raw material to produce a high-quality fired agglomerate for iron making that is charged into a sintering machine. That is, the blending of the main raw material, the solvent and the solid fuel charged in the primary mixer, and the blending of the solid fuel and the CaO source material on the surface of the core part, SiO₂The content is adjusted so as to be 4.8 mass% or less, and a solid fuel within a range of 20 to 0 mass% of the total solid fuel is contained in the core portion of the pseudoparticle, and the pseudoparticle The entire remaining amount of the solid fuel is contained in the outer layer portion. And the mixing | blending of the main raw material, medium solvent, and solid fuel which are charged in the said primary mixer is made into CaO content rate (mass%) in the said mixed raw material, and SiO.₂Ratio (CaO / SiO) with content (mass%)₂)_mix.Is in the range of 0.3 to 0.9, and the blend of the solid fuel and the CaO source material that is sheathed on the surface of the core portion is the CaO content rate (mass in the outer layer portion). %) And SiO₂Ratio (CaO / SiO) with content (mass%)₂)_surf.Is within the range of 1.5 to 4.5, and the CaO content (mass%) of the pseudo particles as a whole and SiO 2₂Ratio (CaO / SiO) with content (mass%)₂)_ps-gr.However, it adjusts so that it may exist in the range of 1.5-2.0. The pseudo-particles thus obtained are characterized by firing treatment.
[0032]
ClaimItem 9The manufacturing method of high-grade fired agglomerated ore for iron making according toItem 6-8In any one of the inventions, the blending of the main raw material, the solvent and the solid fuel to be charged into the primary mixer, and the blending of the solid fuel and the CaO source material to be sheathed on the surface of the core part Further, in addition to the blending adjustment conditions according to claim 8, 9 or 10, the addition of conditions for adjusting the total iron content in the pseudo-particles to be 58 mass% or more. It is.
[0033]
Claim10 notesThe manufacturing method of high-grade fired agglomerated ore for iron making according toItem 6-9In any one of the inventions, the blending of the main raw material, the solvent and the solid fuel to be charged into the primary mixer, and the blending of the solid fuel and the CaO source material to be sheathed on the surface of the core part The claimItem 6-9In addition to the blending adjustment conditions described in any one of the above, the addition of conditions for adjusting the MgO content in the pseudo particles to be in the range of 0.5 to 2.0 mass% It is.
[0034]
Claim11The manufacturing method of high-grade fired agglomerated ore for iron making according toItem 6-10In any one of the inventions, the main raw material is characterized by blending 25 mass% or more of iron ore containing 4 mass% or more of crystal water.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
A feature of the method for producing a high-grade fired agglomerated ore for iron making according to the present invention resides in a pretreatment method for various raw materials and solid fuel. A main solvent mainly composed of iron ore is blended with a solvent and a solid fuel, and the obtained blended material is pretreated as follows to prepare pseudo particles. Here, as a kind of main raw material used by this invention, what is normally used is used. That is, so-called B powder made by mixing pulverized iron ore or multi-brand pulverized iron ore and return ore are used. In addition, dust generated at steelworks, that is, dust containing iron, nickel slag, flux containing MgO, or the like is appropriately used as a miscellaneous raw material. As a solvent, a CaO source material is added, but SiO such as serpentine and quartzite is added.₂Source material is low SiO₂Because it is disadvantageous for the production of sintered ore, it will not be used under normal ore supply and demand conditions.
[0036]
FIG. 1 shows a schematic flow diagram for explaining an example of a desirable production process for producing a fired agglomerated ore according to the present invention. Powder iron ore 1 and return ore 2 as main raw materials, iron mill generated dust 3 as miscellaneous raw materials, quick lime 4 or quick lime 4 and magnesite 5 as a medium solvent, and powder coke 6 as solid fuel Are cut out from each hopper at a predetermined weight ratio, added with water 30 and mixed and processed in the primary mixer 7 to prepare a mixed raw material 8. Dolomite may be used instead of magnesite 5. Next, the mixed raw material 8 is charged into the granulator 9.
[0037]
As the granulator 9, it is desirable to use a dish granulator (disc pelletizer), but a drum mixer having a long residence time can also be used. The mixed raw material 8 that has been humidified with the addition of moisture 25 is pseudo-granulated into an irregularly shaped body having a particle size in the range of about 3 to 12 mm by the granulator 9 to prepare the core portion 10 of the pseudo particle. . If a disk pelletizer is used as the granulator 9, the core part 10 can be prepared efficiently. Powdered coke 11 as a solid fuel and powdered limestone 12, slaked lime 13 or quicklime 14 as a CaO source material are blended in the obtained core portion 10, and moisture-adjusted raw material 15 is prepared by adding moisture 26. The prepared raw material 15 thus obtained is processed by the secondary mixer 16 to prepare pseudo particles 17 in which the surface of the core portion 10 is covered with the solid fuel and the CaO source material.
[0038]
FIG. 2 shows a situation where the sintered cake 3 of the present invention is obtained by firing the pseudo-particles 17 that have been pretreated as described above in the process of producing the sintered agglomerated mineral according to the present invention. Fe₂O_Three-SiO₂It is a schematic diagram demonstrated using an equilibrium state figure.
[0039]
First, the structure of the pre-processed pseudo particle 17 will be described. The pseudo particle 17 (see FIG. 2A) includes a core portion 10 and an outer layer portion 27. The core portion 10 is composed of a MgO-containing flux of hematite and a small amount of gangue, a small amount of powder coke 11 and quicklime 4 and magnesite 5 added in a small amount as appropriate. The core portion 10 is a low basicity composition. And the outer-layer part 27 consists of mixed powder of the high basicity composition which consists of the powder coke 11, the limestone 12 or the slaked lime 13, and the CaO source material which added the quicklime 14 suitably.
[0040]
The pseudo particles 17 thus prepared by being pre-treated are conveyed to the sintering machine 18, and this is used as a raw material for sintering into the pallet 20 of the sintering machine 18 by the raw material charging device 19 with a thickness of about 500 to 700 mm. Fill and charge in layers. The raw material charging device 19 is equipped with a sintered raw material particle size segregation charging mechanism 21, and the sintered raw material charged into the pallet 20 having a bottom surface composed of a grit, that is, the pseudo particles 17, is segregated. 21 to adjust the particle size distribution to change from fine particles to coarse particles from the lower layer to the upper layer. The sintering machine 18 is an endless moving great-type sintering machine, which ignites the upper surface of the sintering raw material layer 22 formed in the pallet 20, and the pseudo particles 17 undergo a drying, heating, melting, and cooling process to be a calcined lump. The sintered ore cake 23 is obtained. The obtained sintered cake 23 is cooled, crushed and sieved to obtain a sintered ore having a predetermined particle size, for example, 4 mm to 50 mm, as a product sintered ore 24, which is used as a raw material for charging a blast furnace. On the other hand, the -4 mm one returns to the sintered ore production raw material as return ore 2.
[0041]
In the above process, in the blending of the main raw material and the solvent medium, the CaO component content (mass%) in the mixed raw material 8 obtained by the primary mixer 7 and SiO 2₂Ratio with component content (mass%) (CaO / SiO₂)_mix.That is, the basicity of the mixed raw material 8 is adjusted so as to fall within the range of 0.3 to 0.9. The solid fuel in the range of 20 to 0 mass% of the total solid fuel to be added to is adjusted. As the solid fuel, for example, it is desirable to use the powder coke 6 as described above. Other solid fuels include powdered char, pulverized coal, and powdered petroleum coke.
[0042]
The first feature in the blending adjustment of various raw materials and solid fuel in the step of preparing the mixed raw material 8 is that of the component composition of the calcined agglomerated SiO 2₂The content ratio is limited to 4.8 mass% or less, and the ratio of the solid fuel added to the mixed raw material 8 (here, powdered coke 6) in the total solid fuel is considerably within the range of 20 to 0 mass%. The ratio may be zero. That is, no solid fuel needs to be added to the mixed raw material 8. On the other hand, in the outer layer portion 27 formed on the surface of the core portion 10 obtained by granulating the mixed raw material 8 in the subsequent step, the entire amount of the remaining solid fuel, that is, the total solid fuel is obtained. It is made to contain in the range of 80-100 mass% of.
[0043]
The second feature is that the basicity of the mixed raw material 8 is considerably low within the range of 0.3 to 0.9 (so-called “low basicity line”), and in contrast, a post-process The basicity of the outer layer portion 27 formed by being coated on the surface of the core portion 10 obtained by granulating the mixed raw material 8 is adjusted to a considerably high value within the range of 1.5 to 4.5. (In other words, it constitutes a “high basicity line”), and the basicity of the pseudo-particles (that is, the granulated material in which the outer layer part is coated on the surface of the core part 10) is determined by the agglomeration (sintering) after firing. The purpose is to adjust the amount of CaO added so that the basicity of the cake 23) is in the range of 1.5 to 2.0. In the firing process, a part of the surface layer of the core portion 10 of the pseudo-particle 17 before firing is melted to constitute a part of the binder phase 29 (see FIG. 2C) after firing. Thus, the basicity of the bonded phase 29 of the calcined agglomerated mineral is set to be in the range of 2.0 to 4.0.
[0044]
CaO-Fe having a component composition in which the basicity of the binder phase 29 is in the range of 2.0 to 4.0.₂O_Three-SiO₂The region on the ternary equilibrium diagram (see FIG. 2, (b)) is a range of 67-80 mass% on the CaO concentration axis, and its lower limit concentration of 67 mass% and Fe₂O_ThreeA straight line connecting the points of 100 mass%, its upper limit concentration of 80 mass% and Fe₂O_ThreeThis corresponds to the inside of a triangular region surrounded by a straight line connecting points of 100 mass%. Fe in this region₂O_ThreeA calcium ferrite-based initial melt (melting temperature <about 1200 ° C.) is generated in the β-phase region existing from the corner. Thereby, the sintered cake 23 after firing is provided with a strong bonding function between the residual core portions 28, and the bonding phase 29 is ensured to have relatively excellent reducibility.
[0045]
In addition, CaO-Fe of the component composition which becomes in the range of basicity 1.5-2.0 of the sintered cake 23₂O_Three-SiO₂Similarly, the region on the ternary equilibrium diagram (see FIG. 2, (b)) is in the range of 60 to 67 mass% on the CaO concentration axis, and Fe₂O_ThreeThis corresponds to the inside of a triangular region surrounded by a straight line connecting points of 100 mass%.
[0046]
In the present invention, as described above, the distribution adjustment and basicity adjustment of the solid fuel to the core portion 10 and the outer layer portion 27 of the pseudo particle 17 are performed, and the SiO contained in the entire pseudo particle is performed.₂By keeping the content low, a sintered cake 23 of the sintered agglomerated mineral is obtained having the following characteristics.
[0047]
The situation where the pseudo particles 17 are fired to obtain the sintered cake 23 will be described with reference to FIGS. The pseudo particles 17 contain most of the powdered coke in the outer layer portion 27, and this is burned with oxygen gas in the suction air in the sintering process. Since the diffusion of oxygen into the pseudo particles 17 is slow, the pseudo particles are ignited in a short time by the combustion of the solid fuel (powder coke) in the outer layer portion 27, and are fired in a high temperature short time sintering pattern. Accordingly, the core portion 10 is indicated by a one-dot chain line l in FIG.₁2, only a part is melted to become the magnetite phase shown in FIG. 2B, moves to the outer layer part 27 and dissolves in the binder phase 29, and the remainder becomes hematite and magnetite, The residual core portion 28 of the sintered cake 23 shown in FIG.₁’). On the other hand, since the outer layer portion 27 is ignited, the one-dot chain line l in FIG.₂The whole melts into the β phase shown in FIG. 2B, absorbs the magnetite phase due to partial melting of the core part, and the calcium ferrite and the locally low basic part are A small amount of olivine slag is formed, and both of these become the binder phase 29 shown in FIG. As described above, the bonded phase 29 is rapidly cooled after being generated in a short time, so that the melt penetration into the residual core portion 28 is suppressed. Thus, the residual core portion 28 is ensured to be composed of porous hematite and porous magnetite. Accordingly, excellent reducibility is exhibited.
[0048]
Here, the SiO of the sintered cake 23₂As a content rate, it is desirable that it is 4.8 mass% or less. SiO₂If the content exceeds 4.8 mass%, the amount of slag components (calcium silicate slag) in the residual core portion 28 and the olivine slag in the binder phase will increase beyond the limit, and the reducibility of the sintered ore will increase. Cannot be maintained at a high level.
[0049]
As described above, as the mineralogical form and physical characteristics of the calcined agglomerated mineral obtained in the present invention, a large amount of the residual core portion 28 formed therein has a small amount of solid fuel and low SiO.₂Since the content is low and the basicity is low, porous hematite and porous magnetite are mainly used, and only a small amount of calcium silicate slag and calcium ferrite is generated. And the porous hematite and porous magnetite which comprise the main body of a residual nucleus part contribute to the intensity | strength maintenance by the binding force of a diffusion coupling main body.
[0050]
On the other hand, in the gaps between the residual core portions 28 in which a large number are formed, a calcium ferrite melt (CaO · Fe produced in the firing process) is formed.₂O_ThreeAnd CaO 2Fe₂O_Three) And a small amount of olivine-based molten slag (2 (Fe, Ca) O.SiO)₂) And a solidified phase 29 is formed, and this bonded phase 29 has a form in which penetration into the residual core portion 28 is suppressed. Since the obtained sintered cake 23 has such a form, the binder phase 29 surrounding a large number of residual core portions 28 complements the maintenance of the strength of the porous hematite and porous magnetite portions by the internal diffusion bonding main body, Even if there is a locally deteriorated portion, it is strongly covered and protected. Here, the main component of the binder phase 29 covering the porous hematite and the porous magnetite is calcium ferrite, which is relatively excellent in reducibility. Since the blending conditions of the main raw material, medium solvent, and solid fuel are satisfied, the bonded phase 29 is formed with a strong bond between the residual core portions 28 and a sintered cake 23 due to impact and wear. It is possible to ensure an amount sufficient to exert a protective action against external force on the surface of the film. However, the basicity of the outer layer portion 27 of the pseudo particle 17 is adjusted to a considerably high value of 1.5 to 4.5, and the high temperature and short time sintering described above, the residual core portion 28 The amount of calcium ferrite or a small amount of olivine-based molten slag in the outermost layer penetrates into the residual core portion 28, and SiO 2₂Since the content is adjusted to be low, the amount of slag in the residual core portion itself is small, and the reducibility of the sintered cake 23 is maintained at an excellent level.
[0051]
As the CaO source material used in the basicity adjustment of the mixed raw material 8, it is desirable to use quick lime 4 without using limestone. Limestone absorbs heat of decomposition through an endothermic reaction during the firing process, leading to an increase in the amount of solid fuel to be blended. In that respect, quicklime 4 is advantageous, and since it exhibits a binder function in the granulation process, it is advantageous for improving granulation properties. When magnesite 8 is used together with quicklime 4, magnetite and magnesiferrite ((Mg, Fe) O.Fe₂O_Three), And as a result, the resistance to reduction dusting is improved. Here, when dolomite is used as the MgO source material, the MgO component is not sufficiently substituted with FeO in the magnetite. However, if magnesite is used, this is eliminated, and the magnesite SiO₂The content rate is very small (less than 1 mass%), Al₂O_ThreeThis is because the content is very small.
[0052]
In the present invention, iron ore containing a crystal water content of about 4 mass% or more (referred to as “high crystal water ore” in the present specification) is appropriately used as the iron ore in the main raw material. However, when the blending ratio of the high crystal water ore in the main raw material is 25 mass% or more, in the production of the calcined agglomerated ore according to the present invention, the granulated property of the pseudo particles is deteriorated as in the conventional sintered ore production. In addition, the yield of the product sintered ore and the productivity are reduced due to the occurrence of local overmelted and unfired portions in the melting / sintering process and deterioration of air permeability. On the other hand, the use of high-crystal water ore as a sintered ore is difficult to avoid in the future. Therefore, also in this invention, a technique for using a large amount of high crystal water ore is necessary. The high-crystal water ore use technology in that case adds that it pre-processes according to the physical property characteristic of the said high-crystal water ore. For example, a pretreatment for removing crystallization water in advance or a pretreatment for sufficiently absorbing water in advance can be considered, and the treatment method can be changed by paying attention to the particle size.
[0053]
Next, the desirable particle size distribution of each constituent particle of the mixed raw material 8 is as follows. For iron ore, a fine powder portion ratio of -0.04 mm accounts for about 50 to 80 mass%, and a coarse particle size of 1 to -8 mm. The grain portion ratio is composed of coarse iron ore having a particle size of about 8 mm, which occupies about 30 to 50 mass%, and the weight composition ratio of the fine iron ore to coarse iron ore is about 30:70 to about 70:30. It is desirable to be within the range. By carrying out like this, in the next granulation process, coarse iron ore becomes a core particle, and powder iron ore becomes an adhering particle on this surface, which is an irregularly shaped body having a high packing density, and the core part of the pseudo particle The formation of is promoted.
[0054]
Use of

coke powders

6 and 11 such as CDQ powder (coke dry fire extinguishing equipment powder) generated in a coke oven at an ironworks as a solid fuel is advantageous because the particle size structure is fine.
[0055]
In the calcined agglomerate according to the present invention, the total iron content is limited to 58 mass% or more. The reason is that when charging the product sintered ore as a blast furnace raw material, the weight of the blast furnace charging main raw material required for production per 1 ton of pig iron (hereinafter referred to as “the ratio of the blast furnace main raw material”) is lowered below a predetermined value. This is because the blast furnace slag ratio is reduced and the blast furnace fuel ratio is reduced. The main raw material charged in the blast furnace is generally composed of treated ore and lump ore, and the main processed ore is sintered ore and pellets. In Japan, many blast furnaces mainly use sintered ore as processing ore, and the remainder is covered with purchased pellets. Some blast furnaces use in-house manufactured pellets as processing ore. The ratio of the sintered ore used in many of the above blast furnaces in Japan to the main raw material is about 70 to 85 mass%. Thus, increasing the iron content of sintered ore, which occupies a large amount in the main raw material charged in the blast furnace, is extremely effective in reducing the blast furnace main raw material ratio and consequently reducing the slag ratio. In Japan, the blast furnace main raw material ratio is about 1600 to 1650 kg / t, and the total iron content in the sintered ore is about 57 mass% to slightly less than 59 mass%.
[0056]
In the calcined agglomerated ore according to the present invention, the desirable content of the MgO component is in the range of 0.5 to 2.0 mass% and is contained in the residual core portion. The reason for this is that if the MgO content is lower than 0.5 mass%, the amount of magnetite and magnetioferrite produced is small and the reduction dust resistance deteriorates, while the MgO content is 2.0 mass%. This is because if it is contained in excess, the reducibility of the product sintered ore is deteriorated due to the influence of dense magnetite.
[0057]
【Example】
The invention is further illustrated by the examples.
[0058]
(Test 1)
The high-grade fired agglomerate for iron making of the present invention was produced according to the production flow of the fired agglomerate shown in FIG. Powdered iron ore 1 and return ore 2 as main raw materials, quick lime 4 and magnesite 5 as medium solvents, and powdered coke 6 as solid fuel are respectively cut out and blended, and the resulting blended raw materials are primary mixer 7 And mixed raw material 8 was obtained. Subsequently, the mixed raw material 8 was charged into the granulator 9, and water 25 was added to perform a granulation process. A pseudo pellet was prepared from the mixed raw material 8 using a disk pelletizer as the granulator 9. The pseudo-granulated material becomes the core portion 10 of the pseudo-particle 17. Powdered coke 11 and powdered limestone 12 were blended into the core portion 10 discharged from the disk pelletizer, and moisture 26 was added to prepare the adjustment raw material 15. The adjusted raw material 15 was processed by the secondary mixer 16 to prepare pseudo particles 17. Powdered limestone 12 and powdered coke 11 are sheathed on the surface of the core part of the pseudo particle 17 to form an outer layer part. The pseudo particles 17 were charged into a sintering machine 18 to produce a sintered cake 23 of a fired agglomerated ore.
[0059]
Table 1 shows the composition of the powdered iron ore 1, returned mineral 2, quicklime 4, magnesite 5 and other components used here, and Table 2 shows the industrial analysis values of the powder coke 6. In addition, the used iron ore 1 used about 40-70 mass% of the ore in which the ratio of the fine powder part of -44 micrometer occupies 40 mass% or more, and about 20-30 mass% of pellet feed.
[0060]
[Table 1]

[0061]
[Table 2]

[0062]
As a production test of the calcined agglomerated ore according to the present invention, a main raw material consisting of fine iron ore 1 and return ore 2 charged into the primary mixer 7, quick lime 4, and mixed raw material consisting of fine coke 6 and magnesite 5 The basicity target value was set to 0.5 and adjusted to fall within the range of 0.3 to 0.9. The amount of powder coke 6 added here was 20 mass% or less of the total amount of powder coke added, and various levels were set. This blended raw material was mixed to obtain a mixed raw material 8, which was pseudo-granulated into an irregular shape having a water content of about 6-8 mass% and a particle size of about 3-12 mm with a disk pelletizer, thereby preparing the core portion 10 of the pseudo particle 17.
[0063]
Next, the granulated core portion 10 was externally coated with the powdered coke 11 and the powdered limestone 12 to prepare pseudo particles 17 as follows.
[0064]
Here, the powdery coke 11 and the powdered limestone 12 of the exterior coating are set so that the basicity target value of the exterior part is set to 2.5 after firing and falls within the range of 2 to 4, and after firing. The target value of the average basicity of the agglomerated ore at 1.75 is added, and the addition of the powder coke 11 and the powdered limestone 12 to the raw material of the core portion 10 so as to fall within the range of at least 1.5 to 2.0 The adjustment raw material 15 was prepared by adjusting the amount and the blending ratio of both. As addition amount of the powder coke 11 here, the whole amount of the remainder which subtracted the powder coke 6 added to the said mixing | blending raw material 8 was added among the total powder coke addition amount. And the SiO of the agglomerated mineral after the firing described above₂The content was adjusted so as to fall within the range of 4.8 mass% or less, the total Fe content of 58 mass% or more, and the MgO content of 0.5 to 2.0 mass%. The prepared raw material 15 thus obtained was processed by the secondary mixer 16 to prepare pseudo particles 17 having a particle size of about 4 to 15 mm.
[0065]
In addition, in the test (Example) within the scope of the present invention described above, the iron ore 1 was adjusted so that the proportion of the high crystal water ore in the main raw material was 25 mass% or more in the brand-specific blending ratio.
[0066]
The pseudo particles 17 prepared under the above conditions were transferred to the sintering machine 18 and charged into the pallet 20 of the sintering machine 18 by the conveyor belt type raw material charging device 19 without being stored in the charging hopper. Here, the reason why the sintered raw material is not stored in the charging hopper is that the amount of quicklime added that also has a binder function included in the core portion 10 is low such that the basicity of the portion is within a range of 0.3 to 0.9. The number is reduced as the range is reduced. This is for the purpose of eliminating the collapse of the pseudo particles 17 as much as possible. The pseudo particles 17, that is, the charging of the sintering material, are distributed by the particle size segregation charging mechanism 21 in the upper layer portion of the sintering material layer 22 in the pallet 20, and the particle size of the sintering material increases toward the lower layer portion. The sintering raw material was distributed. Therefore, the content of the powder coke 11 in the layer thickness direction of the sintered raw material layer 22 is relatively high in the upper layer portion where the fine grain side raw material is distributed, and is relatively low in the lower layer portion where the coarse grain side raw material is distributed. .
[0067]
In addition, this is because the powder coke 6 contained in the core portion of the pseudo particles 17 has substantially the same content rate regardless of the size of the pseudo particles 17. On the other hand, the powder coke 11 that is sheathed on the core portion and included in the outer layer portion adheres almost uniformly to the surface of the core portion, so that the powder coke per specific surface area (surface area per unit mass) of the pseudo particles 17 This is because the amount of 11 is larger in the fine grain side raw material and less in the coarse grain side raw material.
[0068]
In this way, the sintering raw material 22 filled and charged to a layer thickness of about 600 mm was fired by the Dwytroid type sintering machine 18. The atmospheric pressure in the raw material layer at the time of firing was sucked at a negative pressure of about −450 mm in the firing / cooling zone. The reason why the operation can be performed under such a low negative pressure condition is that the air permeability in the raw material layer is well maintained.
[0069]
As a test (comparative example) outside the scope of the present invention with respect to the above example, a fired agglomerated ore was manufactured by the general flow manufacturing process shown in FIG. However, in the comparative example, in the raw material composition of the mixed raw material 8 before granulating the raw material of the core part 10 in the same figure, and the raw material composition for covering the surface of the core part 10 as follows, The blending in the examples was adjusted differently in the following two points. The first point regarding the basicity is that the target value of the average basicity of the agglomerated mineral after firing is less than 1.5 (Comparative Example 1) or more than 2.0 (Comparative Example 2), and The second point is that in the case of each average basicity, the basicity of the exterior portion corresponding region after baking, that is, the basicity of the binder phase 29 (see FIG. 2, (c)) in the baking cake 23 is outside the range of 2-4. In addition, the basicity of the residual core portion (see FIG. 2, (c)) in the baked cake 23 is outside the range of 0.3 to 0.9.
[0070]
Table 3 shows the component composition, mineralogy structure, product quality, and operation results of the product sintered ore produced in the operation test of Examples and Comparative Examples 1 and 2. Here, the microstructure in Table 3 is a result of observing the polished sample with a reflection microscope, and quantitative evaluation in a strict sense is difficult, but shows the characteristics of the structure.
[0071]
[Table 3]

[0072]
Regarding the component composition of the sintered ore according to the present invention, SiO 2₂Content, basicity (CaO / SiO₂), The total iron (T.Fe) content, and the MgO content are all within the desirable range of the present invention, and in the mineralogical structure observation results, the sintering is particularly excellent in reducibility. It exhibits a mineral structure. The quality characteristic of the product sintered ore is the cold strength TI_{+ 5mm}The reduction ratio RI and the reduction dust resistance index RI are excellent. On the other hand, the sintering operation results are excellent in all of the powder coke basic unit, the yield of the product sinter, and the sinter production rate.
[0073]
(Test 2)
A blast furnace operation test was conducted using the calcined agglomerated ore produced in the Example of Test 1 and Comparative Examples 1 and 2 as a blast furnace raw material. Blast furnace operation has an internal volume of 3443m^ThreeIn the blast furnace, the blast temperature is 1200 ° C, the oxygen enrichment rate is 3.2%, the humidity control steam is 25.3 g / Nm.^ThreeThe slag target basicity was 1.22, the pulverized coal injection ratio was set to 150 to 200 kg / t, and the hot metal target temperature was 1500 ° C.
[0074]
Table 4 shows the operation results of the blast furnace obtained in this operation test.
[0075]
[Table 4]

[0076]
In the blast furnace operation of the embodiment using the sintered ore according to the present invention, the main raw material ratio of the blast furnace charge (the weight of ore required to produce 1 ton of pig iron) is about 1600 kg / t or less, and the blast furnace slag ratio is about Thus, a low fuel ratio of approximately 509 kg / t, which is the sum of the coke ratio of 306 kg / t and the pulverized coal injection ratio of 203 kg / t, was achieved.
[0077]
【The invention's effect】
According to the present invention, it is possible to produce a calcined agglomerated mineral with extremely high quality and excellent yield using existing production equipment. Moreover, according to the manufacturing method of the sintered agglomerated mineral of this invention, productivity of a sintered ore improves. And by using this sintered ore as a blast furnace charging raw material, the blast furnace slag ratio is reduced and the fuel ratio in the blast furnace is lowered. As a result, the amount of carbon dioxide emissions at steelworks is reduced, contributing to environmental improvement. Such a high-grade fired agglomerate for iron making and a method for producing the same can be provided, and industrially useful effects are brought about.
[Brief description of the drawings]
FIG. 1 is a schematic flow diagram illustrating an example of a production process desirable for producing a calcined agglomerated mineral according to the present invention.
FIG. 2 is a schematic diagram for explaining a situation in which a pseudo cake is fired to obtain a sintered cake in the process of producing a fired agglomerated mineral according to the present invention, using a parallel state diagram.
[Explanation of symbols]
1 Iron ore
2 Returning
3 Dust
4 Quicklime
5 Magnesite
6 Powdered coke
7 Primary mixer
8 Mixed raw materials
9 Granulator
10 Core part (of pseudoparticle)
11 Powdered coke
12 Powdered limestone
13 Slaked lime
14 Quicklime
15 Preparation raw materials
16 Secondary mixer
17 Pseudoparticles
18 Sintering machine
19 Raw material charging equipment
20 palettes
21 Grain segregation charging mechanism
22 Sintering raw material layer
23 Sintered cake
24 Product Sinter
25 moisture
26 Moisture
27 Outer layer part (of pseudo particles)
28 Residual core (sintered cake)
29 Binder phase (for sintered cake)
30 moisture

Claims

In the pre-processing granulation step, a pseudo-particle particle comprising a core part prepared from a mixed raw material containing iron ore and a medium solvent, and an outer layer part in which the surface of the core part is coated with a solid fuel and a CaO source material. A part of the core part remains in the assembly, and the residual core part is composed of porous hematite and porous magnetite, and a small amount of calcium silicate slag and a small amount of calcium ferrite, and the residual In the gap between the core parts, a bonded phase composed of a solidified phase of a calcium ferrite melt produced in the firing process and a small amount of olivine-based molten slag is formed, and the CaO content (mass%) in the bonded phase And the SiO ₂ content (mass%) ratio (CaO / SiO ₂ ) _bond. Is the CaO content (mass%) and SiO ₂ content (ma ss%) and the ratio (CaO / SiO ₂ ) _rem-gr., and the relationship of the following formulas (1) and (2):
2.0 ≦ (CaO / SiO ₂ ) _bond. ≦ 4.0 (1)
0.3 ≦ (CaO / SiO ₂ ) _rem-gr. ≦ 0.9 (2)
And the ratio of CaO content (mass%) to SiO ₂ content (mass%) in the calcined agglomerated mineral comprising the residual core portion and the binder phase (CaO / SiO ₂ ) _{PROD .} is in the range of 1.5 to 2.0, the sintered Gosho is characterized in that the interior to the penetration of the residual nucleus portion and has a form as it is suppressed, and high for steel Grade fired agglomerate.

In addition to the hematite, the magnetite, and the small amount of calcium silicate slag and the small amount of calcium ferrite as a constituent material of the residual core portion, a small amount of magnesia ferrite serves as a binding strengthening phase of the residual core portion itself. The high-grade calcined agglomerate for iron making according to claim 1, which is added.

The high-grade fired agglomerate for iron making according to claim 1 or 2, wherein the content of SiO ₂ in the fired agglomerate is 4.8 mass% or less.

The high-grade fired agglomerate for iron making according to any one of claims 1 to 3, wherein the total iron content in the fired agglomerate is 58 mass% or more.

The high-grade fired agglomerate for iron making according to any one of claims 1 to 4, wherein the MgO content in the fired agglomerate is in the range of 0.5 to 2.0 mass%. .

The main raw material mainly composed of iron ore is blended with a solvent and a solid fuel, and the resulting blended raw material is charged into a primary mixer and mixed. The resulting mixed raw material is charged into a granulator and simulated. Granulated, the obtained pseudo-granulated body as a core part of the pseudo-particle, blending the solid fuel and CaO source material in the raw material consisting of the core part, processing the obtained adjusted raw material with a secondary mixer, The solid fuel and the CaO source material are attached to the surface of the core portion and prepared as pseudo particles in which an outer layer portion is formed on the surface of the core portion, and the pseudo particles thus obtained are used as a sintering raw material. In the method for producing a high-grade fired agglomerated ore for iron making to be charged into a sintering machine, a mixture of the main raw material, medium solvent and solid fuel to be charged into the primary mixer, and a sheath on the surface of the core part The blend of the solid fuel and the CaO source material is changed to S in the product sintered ore. O ₂ content, adjusted to less 4.8Mass%, and contains a solid fuel and / or solid fuel in the range of 20～0Mass% of the total solid fuel in the core portion of the pseudo particles Ironmaking, characterized in that a raw material is contained, and pseudo particles containing all of the remaining solid fuel in the outer layer portion of the pseudo particles are prepared, and the pseudo particles thus obtained are subjected to a firing treatment. For producing high-grade fired agglomerated minerals.

The main raw material mainly composed of iron ore is blended with a solvent and a solid fuel, and the resulting blended raw material is charged into a primary mixer and mixed. The resulting mixed raw material is charged into a granulator and simulated. Granulated, the obtained pseudo-granulated body as a core part of the pseudo-particle, blending the solid fuel and CaO source material in the raw material consisting of the core part, processing the obtained adjusted raw material with a secondary mixer, The solid fuel and the CaO source material are attached to the surface of the core portion and prepared as pseudo particles in which an outer layer portion is formed on the surface of the core portion, and the pseudo particles thus obtained are used as a sintering raw material. In the method for producing a high-grade fired agglomerated ore for iron making to be charged into a sintering machine, the blending of the main raw material, medium solvent and solid fuel to be charged into the primary mixer is combined with the CaO content in the mixed raw material ( the ratio of mass%) and SiO ₂ content of the (mass%) (CaO / iO ₂₎ _mix. is adjusted to within the range of 0.3 to 0.9, and the addition of the aforementioned solid fuel to the exterior to the surface of the core portion and the CaO source material, the outer layer portion The ratio of CaO content (mass%) and SiO ₂ content (mass%) in the mixture (CaO / SiO ₂ ) _surf. Is in the range of 1.5 to 4.5, and in the product sintered ore Ratio of CaO content (mass%) and SiO ₂ content (mass%) (CaO / SiO ₂ ) CaO added to the outer layer portion so that _PROD is in the range of 1.5 to 2.0. A method for producing a high-grade fired agglomerate for iron making, comprising adjusting a CaO content addition amount in a source material, and subjecting the pseudo particles thus obtained to a fire treatment.

The main raw material mainly composed of iron ore is blended with a solvent and a solid fuel, and the resulting blended raw material is charged into a primary mixer and mixed. The resulting mixed raw material is charged into a granulator and simulated. Granulated, the obtained pseudo-granulated body as a core part of the pseudo-particle, blending the solid fuel and CaO source material in the raw material consisting of the core part, processing the obtained adjusted raw material with a secondary mixer, The solid fuel and the CaO source material are attached to the surface of the core portion and prepared as pseudo particles in which an outer layer portion is formed on the surface of the core portion, and the pseudo particles thus obtained are used as a sintering raw material. In the method for producing a high-grade fired agglomerated ore for iron making to be charged into a sintering machine, a mixture of the main raw material, medium solvent and solid fuel to be charged into the primary mixer, and a sheath on the surface of the core part The blend of the solid fuel and the CaO source material is changed to S in the product sintered ore. O ₂ content, adjusted to less 4.8Mass%, and, by incorporating a solid fuel in the range of 20～0Mass% of the total solid fuel in the core portion of the pseudo particles, and, the pseudo The entire amount of the solid fuel is contained in the outer layer portion of the particles, and the mixture of the main raw material, the solvent and the solid fuel charged in the primary mixer is combined with the CaO content (mass) in the mixed raw material. %) And the SiO ₂ content (mass%) ratio (CaO / SiO ₂ ) _mix. The blend of the solid fuel and the CaO source material is such that the ratio (CaO / SiO ₂ ) _{surf. Between} the CaO content (mass%) and the SiO ₂ content (mass%) in the outer layer portion is 1.5 to C in the quasi-particle so as to be in the range of 4.5 The ratio (CaO / SiO ₂ ) _ps-gr. between the aO content (mass%) and the SiO ₂ content (mass%) was adjusted to be in the range of 1.5 to 2.0, and thus obtained. A method for producing a high-quality fired agglomerated ore for iron making, wherein the pseudo-particles are fired.

The blending of the main raw material, the medium solvent and the solid fuel charged in the primary mixer, and the blending of the solid fuel and the CaO source material to be sheathed on the surface of the core part are described in claims 6 to 8. in addition to the formulations adjustment condition, the total iron content in the pseudo particles, and wherein the adding condition adjusted to be above 58Mass%, according to any one of claims 6-8 A method for producing high-grade fired agglomerates for iron making.

The blending of the main raw material, the medium solvent and the solid fuel charged in the primary mixer, and the blending of the solid fuel and the CaO source material to be armored on the surface of the core part are any of claims 6 to 9. In addition to the blending adjustment conditions described above, a condition for adjusting the MgO content in the pseudo particles to be in the range of 0.5 to 2.0 mass% is added. The manufacturing method of the high quality baked agglomerate for iron manufacture in any one of Claims 6-9 .

The iron ore containing 4 mass% or more of crystal water is mixed in the main raw material in an amount of 25 mass% or more. The high-grade fired agglomerated ore for iron making according to any one of claims 6 to 10 , Production method.