JP4077668B2 - Sinter with excellent softening and melting properties - Google Patents
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- JP4077668B2 JP4077668B2 JP2002183450A JP2002183450A JP4077668B2 JP 4077668 B2 JP4077668 B2 JP 4077668B2 JP 2002183450 A JP2002183450 A JP 2002183450A JP 2002183450 A JP2002183450 A JP 2002183450A JP 4077668 B2 JP4077668 B2 JP 4077668B2
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【0001】
【発明の属する技術分野】
本発明は軟化溶融性状の優れた焼結鉱に関するものである。
【0002】
【従来の技術】
従来から焼結鉱の製造においては、焼結原料に粉コークスや粉石灰石等の副原料を配合して混合し、その配合原料を、造粒機で造粒した後、焼結機に装入し、焼結層の通気を良好に保ちながら操業を行っている。
焼結鉱の品質を向上させるために、通気性に悪影響を及ぼす粉コークス中0.5mm以下を少なくする粒度調整や、融液生成に重要な働きをする粉石灰石の特定粒度を増減させる粒度調整などが実施されてきた。ただ、これらの手段では、還元粉化性や被還元性を改善できるが、高炉下部の反応で最も重要な軟化溶融性状を改善する手段にはなっていなかった。
【0003】
例えば、特公昭63−13475号公報には、粒径7mm未満が100重量%の粉コークスにセメントと水を加えて混合して、混合物を積付けし、セメントの水和反応により形成された水和物でコークス粒子間が結合されるまで養生し、この積付け養生物を、粒径0.5mm未満が40重量%以下となるように解砕して鉄鉱石の焼結時に使用し、粉コークスの燃焼効率を向上させて成品焼結鉱の被還元性(JIS還元率)を向上させる方法が開示されている。
しかし、高炉下部における反応を大幅に向上させるには、焼結鉱の被還元性の向上だけでは不十分で、焼結鉱の軟化溶融性状の改善が重要であるが、上記公報に、焼結鉱の軟化溶融性状の改善については、何も記載されていない。
【0004】
特公昭63−6616号公報には、粉鉄鉱石を下方吸気式焼結機で焼結する際、粒度が10mm以下0.5mm以上の粗粒石灰石を他の配合原料と共に配合して、石灰石の焼結過程における反応を遅らせることにより、2次ヘマタイトの生成または成長を少なくして、耐還元粉化性を向上させる焼結鉱の製造法が開示されている。しかし、高炉下部の反応で最も重要な軟化溶融性状の改善については、何も記載されていない。
【0005】
特開昭57−192228号公報には、粉鉄鉱石を下方吸気式焼結機で焼結する際、粒度1〜3mmが50%以上の石灰石、粒度3〜5mmが10%以下の石灰石、粒度0.25mm以下の微粒子が19%以下の石灰石等を他の原料と配合して焼結することにより、骸晶状菱型ヘマタイトおよび板状カルシウムフェライトの生成を抑制し、被還元性の良い針状カルシウムフェライトと耐還元粉化性の良好な斑状ヘマタイトの生成を増やした、耐還元粉化性と被還元性を向上させる焼結鉱の製造法が開示されている。しかし、高炉下部の反応で最も重要な軟化溶融性状の改善については、何も記載されていない。
【0006】
特開昭61−34119号公報には、微粉鉱石に石灰石を他の配合原料と共に添加して焼結する方法において、石灰石の粒度を3〜5mmの粒子が全石灰石量の35wt%以上となるように調整して、焼結層の通気を良好にしてヒートパターンの高温保持時間を短くし、カルシウムフェライトと再酸化ヘマタイトの隣接を抑制して、耐還元粉化性を著しく改善する焼結鉱の製造法が開示されている。上記公報では、落下強度や被還元性は、従来の焼結法によるものと同等であると説明されているが、高炉下部の反応で最も重要な軟化溶融性状の改善については、何も記載されていない。
【0007】
特開昭58−91132号公報には、粉状鉱石を下方吸気式焼結機で焼結する際、石灰石を水分2〜7%で造粒し、造粒後の粒度が、0.5mm以下が20%以下、3mm以上が40%以下の石灰石を他の原料と配合して焼結し、還元粉化性に悪い2次ヘマタイトの生成を抑えながら被還元性の良いカルシウムフェライトを多量に生成して、JIS還元率と還元粉化指数(RDI)の向上を図る焼結鉱の製造法が開示されている。しかし、高炉下部の反応で最も重要な軟化溶融性状の改善については、何も記載されていない。
【0008】
ISIJ International,31(1991)5,p.468には、焼結過程で粒径が0.7mm以上の石灰石や0.5mm以上の粉コークスが消滅した後に、焼結鉱中にマクロ気孔が生成し易いことが記載されている。しかし、高炉下部の反応で最も重要な軟化溶融性状の改善については、何も触れられていない。
【0009】
材料とプロセス,4(1991),p.1126には、スケールなどの高FeO原料を5wt%以上配合すれば低融点のシリケートスラグが生成し易いことが記載されている。しかし、高FeO原料多配合以外の手段については記載されておらず、微粉コークスの減少とシリケートスラグの生成増の関係、ならびに、高炉下部の反応で最も重要な軟化溶融性状の改善に関する記載はない。
【0010】
【発明が解決しようとする課題】
本発明は、これまで制御する手段が確立されていなかった軟化溶融性状(高炉下部の反応で最も重要な性状)の優れた焼結鉱を提供することを目的とする。
【0011】
【課題を解決するための手段】
本発明の要旨は以下の通りである。
【0012】
(1) 結合組織が、CaO−SiO 2 −FeO系シリケートスラグとマグネタイトが主体で、一部ヘマタイトの結合組織であり、かつ、50μm以上のマクロ気孔が焼結鉱全体に分散していることを特徴とする軟化溶融性状の優れた焼結鉱。
【0014】
【発明の実施の形態】
本発明は、前記課題を解決するため、焼結原料に配合する粉コークスや粉石灰石、返鉱、焼結鉱粉の粒度分布を焼成前に調整することにより、マクロ気孔の生成と粘性の高いCaO−SiO 2 −FeO系シリケートスラグの生成の組合せで、焼結鉱中のマクロ気孔を多く確保することにより得られる軟化溶融性状の優れた焼結鉱を提供するものである。
【0015】
本発明は、まず、粉コークスの0.5mm以下の微粉を大幅に減少させて、擬似粒子の付着粉内へ埋没する粉コークスの量を減らして燃焼性を大幅に改善し、単位時間当たりの粉コークスの燃焼量を増加させて、焼結層内における酸素分圧(Po2)を低下させる。
そうすると、図2(CaO−SiO 2 −FeO系の状態図)に示すように、CaO−SiO2−FeO系の低融点シリケートスラグの生成が促進されて、融液量も増加し、逆に、図1(CaO−SiO 2 −Fe 2 O 3 系の状態図)に示すCaO−SiO2−Fe2O3系のカルシウムフェライト融液の生成が抑制される。
【0016】
それに加えて、石灰石の1.0mm以下の微粉を大幅に減少させて、石灰石の反応性を抑制するので、石灰石は、生成した粘性の高いCaO−SiO 2 −FeO系シリケートスラグと反応することになり、石灰石の反応・消滅後に、マクロ気孔(50μm以上)が形成される。当然、コークスの燃焼・消滅後にも、マクロ気孔が形成される。
CaO−SiO 2 −FeO系シリケートスラグは、粘性が高いので気孔に浸透し難く、気孔自身を閉塞することも少ないので、マクロ気孔(50μm以上)を、焼結鉱全体に、好ましくは均一に造ることができる。
【0017】
この粉コークスの0.5mm以下の微粉を減少させる方法と、粉石灰石の1.0mm以下の微粉を減少させる方法を組み合わせると、従来と違い、焼結鉱の組織は、シリケートスラグ結合主体にマクロ気孔(50μm以上)を、焼結鉱全体に、好ましくは均一に分布させたものになり、高炉内で昇温、還元されるときは、閉塞しない気孔内にガスが十分浸透するので、還元が著しく促進される。
しかも、CaO−SiO 2 −FeO系シリケートスラグとマグネタイトが主体で、一部ヘマタイトの結合組織であるので、カルシウムフェライトとヘマタイトが主体の結合組織に多く見られるような還元時の粉化は少ない。
すなわち、耐還元粉化性が良好で、マクロ気孔(50μm以上)が焼結鉱全体に、好ましくは均一に分散していることによりJIS還元率も向上した焼結鉱になる。この焼結鉱は、高炉シャフト下部の軟化融着ゾーンまで降下しても、マクロ気孔がつぶれないので、還元が益々促進されることになり、メタル・スラグの分離も、より高温側に移行してスムーズになり、図3に示すように、焼結鉱の高温荷重軟化溶融試験の性状が、大幅に改善されることになる。
返鉱や焼結鉱粉の微粉部分には、CaOが10%程度含まれているので、この部分を少なくして配合すれば、CaO−SiO 2 −FeO系シリケートスラグの生成がさらに促進され、上記効果はより増加することになる。
【0018】
鉄と鋼,72(1986)4,S3には、高炉内熱保存帯(シャフト中部)までの低温還元性は、JIS還元率が62%以上であれば良好で、それ以上に改善してもシャフト効率は横這いになり、また、熱保存帯以降(シャフト下部)の高温還元性は、JIS還元率と気孔率によって整理され、JIS還元率のみの改善では、高温還元性の向上幅は少なく、焼結鉱の気孔率の増加との組合せが大きな改善効果をもたらすと記載されている。この記載からも、本発明法のマクロ気孔生成増による軟化溶融性状改善策が妥当であるといえる。
【0019】
本発明法において、コークスの粒度を、0.5mm以下の微粉が0超〜25wt%、5.0〜10.0mmの粗粒が0超〜10wt%としたのは、事前に実施した鍋試験結果で、0.5mm以下の微粉コークスが25wt%より少なくなると効果が出始め、5.0〜10.0mmの粗粒が10wt%を越えると、焼結ベッド下層部への偏析増加による下層部熱過剰の悪影響と、気孔の不均一分散が逆に見られ始めるからである。
微粉コークスの粒度設定を0.5mm以下としたのは、焼結原料の擬似粒子の顕微鏡観察で0.5mm以下の粉コークスが付着粉内に多く埋没していたからであり、粗粒コークス上限の粒度設定を5.0〜10.0mmとしたのは、同じく、擬似粒子の顕微鏡観察で、5.0mmの粉コークスは単独で存在し、かつ、焼結ベッド層高方向の各層解体調査で、下層部分に多く偏析していたからである。
また、この粒度調整をした粉コークスは、焼結新原料の合計(鉄鉱石と焼結鉱粉、副原料)を100%とすると、外%(100%に加えての意味)表示で1.0wt%添加から効果が出始め、7.0wt%以上では熱過剰で効果が見られなくなった。
【0020】
同時に、石灰石の粒度を、1.0mm以下の微粉が0超〜30wt%、5.0〜10.0mmの粗粒が0超〜20wt%としたのも、粉コークスの場合と同様に、事前の鍋試験結果で、1.0mm以下の微粉が30wt%より少なくなると、マクロ気孔の焼結鉱全体にわたる生成による効果が出始め、5.0〜10.0mmの粗粒は、逆に、20wt%を越える辺りから気孔径が大きくなり過ぎて気孔数が減り、かつ、不均一に分散し始めるからである。
微粉石灰石の粒度設定を1.0mm以下としたのは、焼結原料の擬似粒子の顕微鏡観察で、1.0mm以下の微粉石灰石は付着粉内に取り込められていたからである。1〜5mmの粗粒の多くは、擬似粒子の核部分になっていたので、その部分からマクロ気孔が生成されると推定できた。
粗粒石灰石の上限を5.0〜10.0mmと設定したのは、擬似粒子の顕微鏡観察で、5.0mmの石灰石は単独で存在し、かつ、焼結ベッド層高方向の各層解体調査でも下層部分に多く偏析して、均一なマクロ気孔の形成への悪影響が考えられるからである。
また、この粉石灰石は、焼結新原料の合計を100%とすると、内%表示で、5.0wt%以上の添加から効果が出始め、15wt%以上になると効果は横這いになった。
【0021】
返鉱と焼結鉱粉の0.5mm以下の微粉が5wt%より少なくなると、粉コークスと粉石灰石の粒度調整によるマクロ気孔(50μ m 以上)の生成がより促進される。焼結原料微粉部のCaOがより少なくなって、CaO−SiO 2 −FeO系シリケートスラグの生成がさらに促進されたためと考えられる。
微粉の返鉱と焼結鉱粉を0.5mm以下と設定したのは、同じく、焼結原料の擬似粒子の顕微鏡観察で、0.5mm以下の返鉱と焼結鉱粉は付着粉内に埋没していたからである。
【0022】
【実施例】
粉コークスの粒度は、篩い分け法と造粒法の2方法で調整し、粉石灰石も、同様の篩い分け法と造粒法の2方法で調整し、返鉱・焼結鉱粉についても、同様の篩い分け法と上記2方法とは異なる造粒法で調整した。
粉コークス造粒時の水分は12.5wt%、粉石灰石造粒時の水分は6%、返鉱・焼結鉱粉の造粒時の水分は4%とした。篩い分け時の水分は、粉コークスは7%、粉石灰石は3%、返鉱・焼結鉱粉は1%であった。
【0023】
表1に、鍋試験に使用した配合原料の配合割合、表2に、粉コークス、粉石灰石、返鉱・焼結鉱粉の篩い分け法と造粒方法、表3に、鍋試験の各水準、表4に、鍋試験に使用した粉コークスと粉石灰石、返鉱・焼結鉱粉の粒度分布を示した。なお、粉コークス、粉石灰石の造粒にはマルメライザー、返鉱・焼結鉱粉の造粒にはディスクペレタイザーを使用した。表5に、高温荷重軟化溶融試験の条件を示す。
【0024】
【表1】
【0025】
【表2】
【0026】
【表3】
【0027】
【表4】
【0028】
【表5】
【0029】
図3に、粉コークス・粉石灰石と返鉱・焼結鉱粉の粒度調整鍋試験結果の生産率、成品歩留、TI(冷間強度、JISM8712により測定)、RDI(還元粉化性、製銑部会法)、JIS還元率(JISM8713)、成品5〜25mm割合、軟化溶融性状(軟化開始・滴下終了温度、1350℃での収縮率)を示す。
【0030】
図4に、焼結過程のヒートパターンの測定結果の一例を示す。そして、図5に、焼結鉱組織の顕微鏡写真の一例を示す。本発明法によれば、焼結層内のヒートパターンが、上層から下層にかけて均一化する傾向が見られ(図4、参照)、これが、成品焼結鉱の均一化をもたらしていると考えられる。また、本発明法による焼結鉱組織は、CaO−SiO 2 −FeO系シリケートスラグとマグネタイトが主体で、一部ヘマタイトの結合組織になり、かつ、マクロ気孔が、好ましくは均一に分散していることも明らかになった(図5、参照)。
【0031】
以上のように、粉コークスと粉石灰石、さらには返鉱・焼結鉱粉の粒度を同時に調整することにより、次の点が明らかになった。
【0032】
(1)焼結ベッドの通気性が大幅に改善され、焼結時間が短縮し、生産率が大幅に向上する。
【0033】
(2)焼結鉱組織が、CaO−SiO 2 −FeO系シリケートスラグとマグネタイトが主体で、一部ヘマタイトの結合組織になり、さらに融液量も増えるので、成品歩留とTI、RDIが向上する。本組織中にマクロ気孔(50μm以上)が増えるので、JIS還元率も向上する。
【0034】
(3)焼結鉱組織にはマクロ気孔(50μm以上)が、好ましくは均一に分散するので、軟化溶融性状が大幅に改善(軟化開始温度上昇、軟化開始と溶融滴下終了の温度差縮小(融着帯幅縮小)、軟化収縮率抑制)される。さらに、ヒートパターンのシャープ化により、成品粒度分布がシャープ化(+25mm減、5〜25mm増)する。この粒度分布の改善は、高炉内の還元性向上にさらに寄与する。
【0035】
(4)粉コークスと粉石灰石の粒度調整に加えて、返鉱・焼結鉱粉の粒度を同時に調整すると相乗効果が発生し、上記(1)、(2)、および、(3)がさらに増加する。
【0036】
【発明の効果】
本発明によれば、焼結鉱品質の冷間強度や還元粉化性、JIS還元率の向上のみならず、高炉下部の反応にとって最も重要な軟化溶融性状を大幅に向上できるので、高炉の安定操業に大きく寄与する。
【図面の簡単な説明】
【図1】 CaO−SiO2−Fe2O3系の状態図である。
【図2】 CaO−SiO2−FeO系の状態図である。
【図3】 粉コークス・石灰石と返鉱・焼結鉱粉を粒度調整して鍋試験を行った結果を示す図である。
【図4】 焼結層内のヒートパターンを測定した結果の一例を示す図である。
【図5】 焼結鉱の顕微鏡組織を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sintered ore excellent in softening and melting properties.
[0002]
[Prior art]
Conventionally, in the production of sintered ore, auxiliary materials such as powdered coke and powdered limestone are mixed and mixed in the sintered raw material, and the mixed material is granulated with a granulator and then charged into the sintering machine. However, the operation is carried out while maintaining good ventilation of the sintered layer.
In order to improve the quality of sintered ore, the particle size adjustment to reduce 0.5mm or less in the powder coke that adversely affects the air permeability and the particle size adjustment to increase or decrease the specific particle size of the powdered limestone that plays an important role in melt generation Etc. have been implemented. However, these means can improve the reduced powdering property and the reducible property, but have not been the means for improving the most important softening and melting property in the reaction at the bottom of the blast furnace.
[0003]
For example, Japanese Patent Publication No. 63-13475 discloses water formed by hydration of cement by adding cement and water to powder coke having a particle size of less than 7 mm and 100% by weight and mixing the mixture. The coke particles are cured in a Japanese product until the coke particles are bonded together, and this loaded cultured organism is crushed so that the particle size is less than 0.5 mm to 40% by weight or less, and is used when iron ore is sintered. A method for improving the reduction efficiency (JIS reduction rate) of a sintered product ore by improving the combustion efficiency of coke is disclosed.
However, in order to significantly improve the reaction at the bottom of the blast furnace, it is not sufficient to improve the reducibility of the sinter ore, and it is important to improve the softening and melting properties of the sinter. Nothing is described about improving the softening and melting properties of the ore.
[0004]
In Japanese Examined Patent Publication No. 63-6616, when pulverized iron ore is sintered by a lower suction type sintering machine, coarse limestone having a particle size of 10 mm or less and 0.5 mm or more is blended together with other blending raw materials. Disclosed is a method for producing a sintered ore that delays the reaction in the sintering process to reduce the formation or growth of secondary hematite and improve the resistance to reduction dusting. However, nothing is described about the most important improvement in softening and melting properties in the reaction at the bottom of the blast furnace.
[0005]
Japanese Patent Laid-Open No. 57-192228 discloses that when powdered iron ore is sintered by a lower suction type sintering machine, limestone having a particle size of 1 to 3 mm is 50% or more, limestone having a particle size of 3 to 5 mm is 10% or less, particle size The fine particles of 0.25 mm or less contain 19% or less of limestone or the like and sintered together with other raw materials to suppress the formation of body crystal rhomboid hematite and plate-like calcium ferrite, and needles with good reducibility There is disclosed a method for producing sintered ore that improves the reduction powder resistance and the reducibility by increasing the production of powdered hematite having good resistance to powdered calcium ferrite and reduction powder. However, nothing is described about the most important improvement in softening and melting properties in the reaction at the bottom of the blast furnace.
[0006]
In JP-A-61-34119, in a method in which limestone is added to finely divided ore together with other compounding raw materials and sintered, particles having a limestone particle size of 3 to 5 mm are 35 wt% or more of the total amount of limestone. Of the sintered ore that significantly improves the resistance to reduced dusting by suppressing the adjacent of calcium ferrite and reoxidized hematite by shortening the high temperature holding time of the heat pattern by improving the ventilation of the sintered layer. A manufacturing method is disclosed. In the above publication, it is explained that the drop strength and reducibility are equivalent to those of the conventional sintering method, but nothing is described about the most important softening and melting property improvement in the reaction at the bottom of the blast furnace. Not.
[0007]
In JP-A-58-91132, when a powdered ore is sintered by a lower suction type sintering machine, limestone is granulated with a moisture content of 2 to 7%, and the grain size after granulation is 0.5 mm or less. 20% or less, 3mm or more and 40% or less limestone is mixed with other raw materials and sintered to produce a large amount of calcium ferrite with good reducibility while suppressing the formation of secondary hematite with poor reducibility. And the manufacturing method of the sintered ore which aims at the improvement of a JIS reduction rate and a reduction | restoration powdering index (RDI) is disclosed. However, nothing is described about the most important improvement in softening and melting properties in the reaction at the bottom of the blast furnace.
[0008]
ISIJ International, 31 (1991) 5, p. No. 468 describes that macropores are likely to be generated in the sintered ore after limestone having a particle size of 0.7 mm or more or powder coke of 0.5 mm or more disappears during the sintering process. However, nothing is said about the most important improvement in softening and melting properties in the reaction at the bottom of the blast furnace.
[0009]
Materials and Processes, 4 (1991), p. 1126 describes that a silicate slag having a low melting point is easily generated when a high FeO raw material such as scale is blended in an amount of 5 wt% or more. However, there is no description about means other than the high FeO raw material multiple blending, and there is no description on the relationship between the reduction of fine coke and the increase in the formation of silicate slag and the most important improvement in softening and melting properties in the reaction at the bottom of the blast furnace. .
[0010]
[Problems to be solved by the invention]
An object of the present invention is to provide a sintered ore having an excellent softening and melting property (the most important property in the reaction at the bottom of the blast furnace), for which no means for control has been established.
[0011]
[Means for Solving the Problems]
The gist of the present invention is as follows.
[0012]
(1) connective tissue, in CaO-SiO 2 -FeO-based silicate slag and magnetite mainly is part hematite connective tissue, and, more macropores 50μm is dispersed Tei Rukoto throughout sinter A sintered ore with excellent softening and melting properties.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In order to solve the above-mentioned problems, the present invention adjusts the particle size distribution of powdered coke, powdered limestone, return mineral, and sintered ore powder to be mixed in the sintered raw material before firing, thereby generating macropores and high viscosity. A combination of the production of CaO—SiO 2 —FeO silicate slag provides a sintered ore with excellent softening and melting properties obtained by securing a large number of macropores in the sintered ore.
[0015]
The present invention first greatly reduces the fine powder of 0.5 mm or less of the powder coke, reduces the amount of powder coke embedded in the adhering powder of pseudo particles, greatly improves the combustibility, and per unit time The amount of combustion of the powder coke is increased to reduce the oxygen partial pressure (Po 2 ) in the sintered layer.
Then, as shown in FIG. 2 (CaO—SiO 2 —FeO-based phase diagram) , the generation of CaO—SiO 2 —FeO-based low melting point silicate slag is promoted and the amount of melt increases, conversely, Formation of the CaO—SiO 2 —Fe 2 O 3 -based calcium ferrite melt shown in FIG. 1 (CaO—SiO 2 —Fe 2 O 3 -based phase diagram) is suppressed.
[0016]
In addition, limestone reacts with the highly viscous CaO—SiO 2 —FeO silicate slag that is produced by significantly reducing the fine powder of limestone of 1.0 mm or less and suppressing the reactivity of limestone. Thus, after the reaction and disappearance of limestone, macropores (50 μm or more) are formed. Naturally, macropores are formed even after the combustion and extinction of coke.
CaO—SiO 2 —FeO-based silicate slag is highly viscous, so that it does not easily penetrate into the pores and hardly clogs the pores themselves, so that macropores (50 μm or more) are preferably formed uniformly throughout the sintered ore. be able to.
[0017]
Combining this method of reducing fine powder of 0.5 mm or less in powder coke with the method of reducing fine powder of 1.0 mm or less in powdered limestone, unlike the conventional structure, the structure of the sintered ore is macroscopically composed mainly of silicate slag. The pores (50 μm or more) are preferably uniformly distributed throughout the sintered ore, and when the temperature is increased and reduced in the blast furnace, the gas sufficiently permeates into the pores that do not occlude. Remarkably promoted.
Moreover, since CaO—SiO 2 —FeO-based silicate slag and magnetite are mainly composed of a connective structure of hematite, there is little pulverization at the time of reduction, which is often observed in a connective structure mainly composed of calcium ferrite and hematite.
That is, the reduction ore powdering resistance is good, and the macropores (50 μm or more) are preferably dispersed uniformly throughout the sintered ore, so that the JIS reduction rate is improved. Even if this sinter descends to the softening and fusion zone at the bottom of the blast furnace shaft, the macropores do not collapse, so the reduction will be promoted more and the separation of metal and slag will shift to a higher temperature side. As shown in FIG. 3, the properties of the high-temperature load softening and melting test of the sintered ore are greatly improved.
Since the fine powder portion of the return or sintered ore powder contains about 10% of CaO, if this portion is reduced and added, the generation of CaO—SiO 2 —FeO silicate slag is further promoted, The above effect will be further increased.
[0018]
For iron and steel, 72 (1986) 4, S3, the low temperature reducibility up to the blast furnace heat preservation zone (shaft middle part) is good if the JIS reduction rate is 62% or more, and even if it is improved further. The shaft efficiency becomes flat, and the high temperature reducibility after the heat preservation zone (bottom of the shaft) is organized by the JIS reduction rate and the porosity. By improving only the JIS reduction rate, there is little improvement in high temperature reducibility, It is described that the combination with the increase in porosity of the sinter provides a significant improvement effect. From this description as well, it can be said that the softening and melting property improvement measures by the macropore formation increase of the method of the present invention are appropriate.
[0019]
In the method of the present invention, the coke particle size was set to more than 0 to 25 wt% for fine powder of 0.5 mm or less, and more than 0 to 10 wt% for coarse particles of 5.0 to 10.0 mm. As a result, when the fine coke of 0.5 mm or less is less than 25 wt%, the effect starts to appear, and when the coarse particles of 5.0 to 10.0 mm exceed 10 wt%, the lower layer due to increased segregation to the lower layer of the sintered bed This is because the adverse effects of excessive heat and the uneven distribution of pores begin to be seen in reverse.
The reason why the fine particle coke particle size was set to 0.5 mm or less was that a large amount of powder coke of 0.5 mm or less was buried in the adhering powder by microscopic observation of the pseudo particles of the sintering raw material. The setting was set to 5.0 to 10.0 mm in the same manner as in the microscopic observation of pseudo particles, and the powder coke of 5.0 mm existed alone, and in each layer disassembly investigation in the sintered bed layer high direction, the lower layer This is because many segregated in the part.
In addition, the powder coke whose particle size has been adjusted is expressed as 1.% (meaning in addition to 100%) when the total of new sintered raw materials (iron ore, sintered ore powder, and auxiliary raw materials) is 100%. The effect started to appear when 0 wt% was added, and when it was 7.0 wt% or more, the effect was not observed due to excessive heat.
[0020]
At the same time, the limestone particle size is set to more than 0 to 30 wt% for fine powder of 1.0 mm or less, and more than 0 to 20 wt% for coarse particles of 5.0 to 10.0 mm, as in the case of powder coke. As a result of the ladle test, when the fine powder of 1.0 mm or less is less than 30 wt%, the effect due to the formation of the macroporous whole sinter starts to appear, and the coarse particles of 5.0 to 10.0 mm, on the contrary, 20 wt. This is because the pore diameter becomes too large from around the%, the number of pores decreases, and the dispersion starts unevenly.
The reason why the fine particle size of the fine limestone is set to 1.0 mm or less is that the fine powder limestone of 1.0 mm or less is taken into the adhered powder in the microscopic observation of the pseudo particles of the sintering raw material. Since most of the coarse particles of 1 to 5 mm were the core parts of the pseudo particles, it was estimated that macropores were generated from these parts.
The upper limit of coarse limestone was set to 5.0 to 10.0 mm by microscopic observation of pseudo particles, 5.0 mm limestone existed alone, and in each layer disassembly survey in the sintered bed layer height direction This is because a large amount of segregation occurs in the lower layer portion, which may adversely affect the formation of uniform macropores.
Moreover, this powder limestone, when the total amount of the new sintered raw materials was 100%, started to show an effect from the addition of 5.0 wt% or more in terms of%, and the effect became flat when it became 15 wt% or more.
[0021]
When 0.5mm following fines return ores and Shoyuikoko is less than 5 wt%, generation of macro pores by particle size adjustment of coke and powdered limestone (or 50.mu. m) is further promoted. This is probably because the CaO in the fine powder portion of the sintering raw material was reduced, and the generation of the CaO—SiO 2 —FeO silicate slag was further promoted.
Similarly, the fine powder return and sintered ore powders were set to 0.5 mm or less by microscopic observation of the pseudo raw material of the sintered raw material. Because it was buried.
[0022]
【Example】
The particle size of powder coke is adjusted by two methods of sieving method and granulation method, and powdered limestone is also adjusted by two methods of sieving method and granulation method. The same sieving method and the above two methods were adjusted by different granulation methods.
The moisture at the time of granulation of the powder coke was 12.5 wt%, the moisture at the time of granulation of the powdered limestone was 6%, and the moisture at the time of granulation of the return or sintered ore powder was 4%. The moisture at the time of sieving was 7% for the powder coke, 3% for the powdered limestone, and 1% for the return or sintered ore powder.
[0023]
Table 1 shows the blending ratio of the ingredients used in the pan test, Table 2 shows the sieving method and granulation method for powdered coke, powdered limestone, and returned or sintered ore powder. Table 3 shows the levels of the pot test. Table 4 shows the particle size distribution of the powdered coke, powdered limestone, and returned or sintered ore powder used in the pan test. In addition, a malmerizer was used for the granulation of the powdered coke and powdered limestone, and a disk pelletizer was used for the granulation of the returned or sintered ore powder. Table 5 shows the conditions of the high temperature load softening and melting test.
[0024]
[Table 1]
[0025]
[Table 2]
[0026]
[Table 3]
[0027]
[Table 4]
[0028]
[Table 5]
[0029]
Fig. 3 shows the production rate, product yield, TI (cold strength, measured by JISM8712), RDI (reducible powder, Isobe method), JIS reduction rate (JISM8713), product 5-25 mm ratio, softening and melting properties (softening start / end temperature, shrinkage at 1350 ° C.).
[0030]
In FIG. 4, an example of the measurement result of the heat pattern of a sintering process is shown. Then, in FIG. 5, shows the example of a photomicrograph of the sintered ore tissue. According to the method of the present invention, there is a tendency that the heat pattern in the sintered layer becomes uniform from the upper layer to the lower layer (see FIG. 4), and this is considered to bring about homogenization of the product sintered ore. . In addition, the sintered ore structure according to the present invention is mainly composed of CaO—SiO 2 —FeO silicate slag and magnetite, partially becomes a hematite connective structure, and macropores are preferably uniformly dispersed. This also became clear (see FIG. 5 ).
[0031]
As described above, the following points were clarified by simultaneously adjusting the particle sizes of the powdered coke and powdered limestone, and the returned or sintered ore powder.
[0032]
(1) The air permeability of the sintered bed is greatly improved, the sintering time is shortened, and the production rate is greatly improved.
[0033]
(2) Sintered ore structure is mainly CaO-SiO 2 -FeO silicate slag and magnetite, partly becomes a hematite connective structure, and the amount of melt also increases, improving product yield, TI, and RDI To do. Since macropores (50 μm or more) increase in this structure, the JIS reduction rate is also improved.
[0034]
(3) Since the macropores (50 μm or more) are preferably uniformly dispersed in the sintered ore structure, the softening and melting properties are greatly improved (softening start temperature rise, softening start and melting dripping temperature difference reduction (melting) (Bandwidth reduction) and softening shrinkage rate suppression). Furthermore, sharpening of the heat pattern sharpens the product particle size distribution (+25 mm decrease, 5-25 mm increase). This improvement in the particle size distribution further contributes to the improvement of reducing properties in the blast furnace.
[0035]
(4) In addition to adjusting the particle size of powdered coke and powdered limestone, adjusting the particle size of the returned or sintered ore powder simultaneously produces a synergistic effect, and the above (1), (2), and (3) are further To increase.
[0036]
【The invention's effect】
According to the present invention, it is possible not only to improve the cold strength, reduced powdering property and JIS reduction rate of sintered ore quality, but also to greatly improve the softening and melting properties that are most important for the reaction at the bottom of the blast furnace. Contributes greatly to operations.
[Brief description of the drawings]
FIG. 1 is a phase diagram of a CaO—SiO 2 —Fe 2 O 3 system.
FIG. 2 is a phase diagram of a CaO—SiO 2 —FeO system.
FIG. 3 is a diagram showing the results of a pot test in which powder coke / limestone and return or sintered ore powder were adjusted in particle size.
FIG. 4 is a diagram showing an example of a result of measuring a heat pattern in a sintered layer.
FIG. 5 is a view showing a microstructure of a sintered ore.
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