JP3831293B2

JP3831293B2 - Method for producing sintered ore

Info

Publication number: JP3831293B2
Application number: JP2002143126A
Authority: JP
Inventors: 俊秀松村; 文雄野間
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2002-05-17
Filing date: 2002-05-17
Publication date: 2006-10-11
Anticipated expiration: 2022-05-17
Also published as: JP2003328043A

Description

【０００１】
【発明の属する技術分野】
本発明は、焼結鉱の製造方法に関し、特に排ガス循環操業において焼結鉱の品質を低下させることなく高生産性を達成し得る焼結用混合原料の製造方法に関するものである。
【０００２】
【従来の技術】
通常、高炉用原料である焼結鉱は、概略以下の工程で製造される。
【０００３】
まず、約１０ｍｍ以下の粒度の焼結用鉱石原料である、鉄鉱石粉および焼結返鉱と、約３ｍｍ以下の粒度の珪石、石灰石、蛇紋岩などの副原料と、コークス粉、石炭粉などの固体燃料と、生石灰、消石灰等の凝集剤とを混合し、配合水を添加して混練に引き続いて疑似粒子化（粗い粒子を核として、その表面に微細な粒子を水の表面張力により付着させて形成した粒子群）した混合原料を、焼結機（たとえばＤＬ式焼結機）のパレット上に充填し、層頂部の混合原料中の固体燃料に着火する。着火後、下方に向けて空気を吸引しながら固体燃料を燃焼させてこの燃焼熱により充填した混合原料（原料充填層）を焼結させて焼結ケーキとする過程で、混合原料を乾燥後、１１５０〜１２００℃へ加熱することにより、混合原料中の鉄鉱石と副原料とのスラグ反応により融液を生成させる。この融液により鉄鉱石粉の液相焼結が行われ、冷却後、この融液による鉄鉱石粉の結合により必要な焼結鉱の強度が得られる。
【０００４】
焼結機としては、近年、排ガス循環方式の焼結機が広く採用されるようになってきた。排ガス循環方式の焼結機は、従来の大気吸引方式の焼結機の欠点を改善し、環境保全の点から焼結機の系外に排出する排ガス量やNOｘ総量の削減、さらに排ガスの熱回収、生産性の向上などを図るようにしたものである。
【０００５】
例えば、特開平５−４３９５１号公報には、焼結機の点火炉域と後部域のウィンドボックス（風箱）からの排ガスを、それぞれ点火炉域の排ガスは焼結機の中後部に、また後部域の排ガスは点火炉後の焼結機の前部に循環するとともに、各循環される排ガス中の酸素濃度を１８％以上とした排ガス循環操業方法が提示されている。この操業方法において、循環排ガス中の水分を１０％以下、好ましくは７％以下とすることにより排ガス循環経路内での結露を防止するとともに、焼結機の中後部の焼結燃焼層の燃焼促進が図れるとしている。
【０００６】
一方、近年の鉄鉱石資源の変化に起因して、焼結用鉱石原料に占める豪州産ピソライト鉱石やマラマンバ系鉱石等の高保水能鉱石の比率が増加している。これらの高保水能鉱石は、表面に微小気孔を多数有しているために、安定して擬似粒子化するためには、造粒時に従来の鉄鉱石よりも多量の水分を添加する必要がある。この造粒水分が焼結時に蒸発して排ガス中に移行し、これを焼結機に再循環するため循環排ガス中の水分濃度はさらに上昇する傾向にある。循環排ガス中の水分が１０％を超えると、焼結中の原料充填層下部（湿潤帯）に多量の水分が凝縮するため、上部からの荷重により擬似粒子が崩壊されやすくなる。このため、混合原料の通気性が悪化して焼結に要する時間が長くなり、焼結鉱の生産能率が低下し、あるいは焼結鉱の強度が低下して歩留が低下することが問題となっている（図８参照）。
【０００７】
この対策として、造粒後の擬似粒子を予め乾燥させたのちに焼結させることにより、循環排ガス中の水分濃度を低下させることが考えられる。
【０００８】
例えば、特開昭６１−２３８９２５号公報には、ミキサー内で擬似粒子化された混合原料を焼結機クーラーの排ガスを利用した移動パレット式乾燥装置により加熱・乾燥し、混合原料中の水分を３〜４重量％の範囲に減少することにより、焼結ベッド（原料充填層）の通気性を向上することができるとする提案がなされている。しかしながら、この方法は、擬似粒子（混合原料）を乾燥させるために過大な設備コストが必要となる問題がある。
【０００９】
また、特開平６−３３０１８９号公報には、含有水分量を５．０％以下に調整した焼結原料（混合原料）を焼結パレット上の原料充填層の表層に装入し、しかる後に焼成することにより、焼結層上部の歩留を大幅に向上させる方法が提示されている。しかしながら、単純に造粒水分を低減した場合、原料鉱石の造粒性が大幅に低下して擬似粒子化が不十分となるため、充填層の通気性が低下し、その結果として焼結鉱の生産性はむしろ低下するという問題がある。
【００１０】
また、特開平６−３３０１８９号公報、特開平８−１４７６３号公報では、焼結パレット上に原料充填層を形成した後に、点火炉で着火するまでの間に、高温ガス、マイクロ波加熱などにより、原料充填層を全厚にわたって乾燥する方法が提示されている。しかしながら、これらの方法も前述の特開昭６１−２３８９２５号と同様、原料充填層を乾燥するために過大な設備改造が必要であることに加え、別途加熱エネルギーを必要とするため焼結鉱の製造コストが上昇する問題がある。
【００１１】
【発明が解決しようとする課題】
そこで、本発明の目的は、排ガス循環操業において高保水能鉱石を多量使用しても、過大な設備コストを不要とし、かつ製造コストを著しく増大させることなく、循環排ガス中の水分含有量を維持ないし低減して原料充填層の通気性を維持ないし改善し、製品焼結鉱の生産性および歩留を維持ないし向上しうる焼結鉱の製造方法を提供することにある。
【００１２】
【課題を解決するための手段】
本発明者らは、上記課題を解決するため、焼結混合原料の添加剤に注目し、添加剤の種類、組み合わせ、添加量、添加方法等について種々検討を行った。その結果、有機繊維、粘土質物質、および有機粘着材を組み合わせたものを添加剤として、高保水能鉱石に選択的に多く添加することにより上記課題を解決し得ることを見出した。
【００１３】
すなわち、請求項１に記載の発明は、焼結用鉱石原料を、「高保水能鉱石としての結晶水含有量：３．０質量％以上及び／又は比表面積：３．０ｍ ^２／ｇ以上の鉱石」を含む第１系統の原料と、その他の鉱石からなる第２系統の原料とに２分する焼結原料分割工程と、その他の鉱石からなる第２系統の原料とに２分する焼結原料分割工程と、前記第１系統の原料に、副原料と、固体燃料とを添加し、さらに、有機繊維と、粘土質物質と、有機粘着材とからなる添加剤を添加して第１系統の造粒原料を造粒する第１系統造粒工程と、前記第２系統の原料に、副原料と、固体燃料とを添加し、さらに必要により前記添加剤を添加して第２系統の造粒原料を造粒する第２系統造粒工程と、前記第１系統及び第２系統の造粒原料を混合して混合原料とする原料混合工程と、前記混合原料を常法により焼結する焼結工程とを備える焼結鉱の製造方法であって、前記第１系統の造粒原料中に、乾量基準で、有機繊維０．０１〜１．０質量％と、粘土質物質０．０１〜１．０質量％と、有機粘着材０．０００５〜０．１質量％とを含ませるとともに、前記第２系統の造粒原料中に含ませる、有機繊維と、粘土質物質と、有機粘着材の各質量％を、前記第１系統の造原料中に含まれる有機繊維と、粘土質物質と、有機粘着材の各質量％のそれぞれ５０％以下とすることを特徴とする焼結鉱の製造方法である。
【００１４】
高保水能鉱石に有機繊維、粘土質物質、および有機粘着材からなる添加剤を添加して造粒すると、有機繊維は吸水性を有するため核粒子内部への吸水を阻止して原料の造粒性を向上させ、少ない造粒水分で擬似粒子化が可能となる。そのため、通常、多銘柄鉱石からなる焼結用鉱石原料を予め高保水能鉱石を含む原料（第1系統の原料）とその他の原料（第２系統の原料）とに２分しておく。そして、上記有機繊維、粘土質物質、および有機粘着材からなる添加剤を、第１系統の原料側の方にのみ添加ないしは選択的に多く添加するとよい。
【００１５】
また、有機繊維自身と粘土質物質は難水溶性であるが、有機粘着材は易水溶性であるので造粒水に溶解し、有機繊維と粘土質物質との接点に侵入してこれらを接合する。この接合物が原料鉱石や石灰石等の粒子間に入って粒子間の摩擦を大きくするため湿潤帯においても擬似粒子の崩壊が防止される。そのため、第２の原料側にも、上記添加剤を添加してもよい。なお、この場合、第２の原料側には高保水能鉱石は含まれていないことから造粒性には問題がないため、上記添加剤の添加濃度は、第1の原料側より低濃度でよい。以上の結果、原料充填層の通気性が著しく改善され、焼結鉱製造の生産性が飛躍的に向上する。なお、有機繊維と有機粘着材は焼結時に燃焼して燃料として利用されるのでコークスや石炭などの固体燃料の配合量をも低減でき、粘土質物質は鉄鉱石等とスラグ反応して融液を生成し、焼結反応を促進する。
【００１６】
ここで、高保水能鉱石として、結晶水含有量：３．０質量％以上及び／又は比表面積：３．０ｍ ^２／ｇ以上の鉱石に限定したのは、結晶水含有量：３．０質量％以上及び／又は比表面積が３．０ｍ ^２／ｇ以上の鉱石は、特に高い保水能を示すため、このような条件を満たす鉱石に対し選択的に上記添加剤を添加することで、より効果的に造粒性を高めることができるからである。
【００１７】
また、有機繊維、粘土質物質、有機粘着材とも添加量が少なすぎると上記の効果が十分得られない一方、これらの添加量が多すぎると焼結鉱の製造コストが高くなりすぎることに加え、粘土質物質の添加量が多すぎると高炉のスラグ量が増加するので上記範囲の添加量の組み合わせとする。なお、有機粘着材の添加量が有機繊維および粘土質物質の添加量に比べ大幅に少なくてよいのは、有機粘着材が少なくても焼結原料の配合水に溶解して有機繊維と粘土質物質との接点部に重点的に侵入・配置され両者を接合する役目を果たすからである。また、第２の造粒原料側への添加濃度を第１の造粒原料の添加濃度の５０％以下に限定したのは、５０％を超える添加は擬似粒子の強度を向上させる効果に比し、焼結鉱の製造コストの上昇や高炉のスラグ量が増大する影響の方が大きくなるからである。
【００１８】
上記添加剤のうち、有機繊維の長さは、短すぎると摩擦力が小さく上記の作用効果が十分発揮されず、一方、長すぎると同じ添加量であっても鉱石等の粒子間への分散が不均一となり上記の作用効果が減殺されるので、繊維の長さが１〜２０００μｍの範囲のものが相当量（例えば８０質量％以上）存在することが好ましい。
【００１９】
また、有機繊維としては、例えば、セルロース木質繊維、織物繊維、又はこれらの混合物など、粘土質物質としては、例えば、主として２０〜５０質量％のＳｉＯ₂、２０〜５０質量％のＡｌ₂Ｏ₃、５〜２０質量％のＣａＣＯ₃、２〜１０質量％のＭｇＯ、１〜８質量％のＦｅ₂Ｏ₃からなる物質、有機粘着材としては、例えば、リグニン、澱粉、デキストリン、糖蜜等又はこれらの混合物などを用いることができる。これらの物質は比較的安価でかつ量の確保が容易なため、低コストで焼結鉱製造の生産性の向上を達成できる。
【００２０】
請求項２に記載の発明は、前記有機繊維と粘土質物質と有機粘着材からなる添加剤を古紙スラッジとすることを特徴とする請求項１に記載の焼結鉱の製造方法である。
【００２１】
古紙スラッジは、古紙リサイクル工程において、アルカリ剤等を含む溶液を加えて古紙を離解した古紙懸濁液スラリーからパルプを取出した後の廃液中に含まれる浮遊物を分離回収したものである。したがって、古紙スラッジには、比較的短い有機繊維であるセルロース木質繊維が相当量含有されている。また、古紙の無機充填剤および無機顔料であるベントナイト、タルク、石灰石、ドロマイト等由来の粘土質物質が濃縮され、さらに有機粘着材であるリグニンが含まれているので、これを用いることにより、上記請求項１に記載された発明の効果を得ることができる。さらに、従来、古紙スラッジの大部分は、脱水又は乾燥して埋め立て処分や焼却処分されており、その処分に多大な経費を要していた。しかし、本発明によれば、この古紙スラッジを大量に生産される焼結鉱の添加剤として用いることにより、資源およびエネルギーとして有効利用できるのみならず、環境汚染の防止にも寄与するものである。なお、特開平７−１８３４４号公報には、古紙スラッジではなく、古紙そのものを焼結鉱の製造に用いる方法が開示されている。ところが、古紙は古紙スラッジとは異なり比較的長い繊維で構成されていること、焼結原料に添加する際に繊維が離解されていないため別途解砕が必要なこと、粘土質物質の量が繊維の量に比べて非常に少ないこと等の理由から本発明の効果を奏し得ないものである。
【００２２】
【００２３】
【００２４】
【発明の実施の形態】
本発明の好ましい実施の一形態を以下に示す。
【００２５】
焼結用原料鉱石を銘柄ごとに高保水能鉱石とその他の鉱石に分類する。分類は、保水能と密接に関連する、結晶水含有量と比表面積とで行えばよい。ここで、比表面積は、ガス吸着法により測定した、一点ＢＥＴ比表面積を採用した。別途、保水能と、結晶水含有量および比表面積との関係を調査した結果、結晶水含有量が３．０質量％以上及び／又は比表面積：３．０ｍ²／ｇ以上のとき、特に高保水能を示すことが明らかとなった。したがって、この条件を満たす銘柄の鉱石を高保水能鉱石としてこれを第１系列の原料とし、その他の、結晶水含有量が３．０質量％未満でかつ比表面積が３．０ｍ²／ｇ未満の鉱石を第２系列の原料とするとよい（なお、焼結返鉱は保水能が低いため第２系列の原料に含めるとよい）。なお、第１系列と第２系列との原料の量のバランスを考慮して、第１系列の原料に、高保水能鉱石でない鉱石の一部を用いてもよい。
【００２６】
そして、第１系列の原料に、副原料として所定量の石灰石や生石灰および必要により珪石少量と、固体燃料として所定量のコークス粉または無煙炭粉とを添加し、さらに、所定量の古紙スラッジを添加し、造粒水を加えて第１のドラムミキサーで混練、疑似粒化して第１系列の造粒原料とする。原料中に相当量の古紙スラッジが存在するため、前述したように造粒水分が低減でき、擬似粒子中の水分含有量が低下できる。
【００２７】
なお、古紙スラッジは通常、水分を８０〜１２０質量％（乾量基準）程度含み紙粘土状の塊の状態になっているため、事前に、脱水・乾燥した後にボールミル等で粉砕しておき、粉状で添加するのがよい。あるいは、塊状の古紙スラッジに造粒水の一部又は全部を添加・攪拌してスラリー状にしたものを用いてもよい。古紙スラッジの添加量は、古紙スラッジ中の有機繊維、粘土質物質、及び有機粘着材の含有量に応じて、造粒原料中に乾量基準で、有機繊維０．０１〜１．０質量％、粘土質物質０．０１〜１．０質量％、及び有機粘着材０．０００５〜０．１質量％が含まれるように適宜調整すればよい。
【００２８】
一方、第２系列の原料に対しては、副原料と固体燃料とを添加し、さらに必要により古紙スラッジを添加し、適量の造粒水を加えて第１系列とは別の第２のドラムミキサーで混練、疑似粒化して第２系列の混合原料とする。なお、古紙スラッジを添加する場合は、第２系列の造粒原料中の古紙スラッジの添加濃度が、第１系列の混合原料の古紙スラッジの添加濃度の５０％以下となるように調整する。
【００２９】
このようにして擬似粒子化された第１および第２の造粒原料を、さらに別のミキサー内で一緒に混合し、混合原料とする。
【００３０】
このようにして作製した混合原料を、排ガス循環方式焼結機のパレット上に充填し、表層部の混合原料中の固体燃料に着火する。着火後、下方に向けて循環ガスを吸引することにより固体燃料を燃焼させてこの燃焼熱により充填した混合原料を焼結させて焼結ケーキとする。
【００３１】
この着火から焼結ケーキ製造までの過程で蒸発した水分は、吸引された循環ガス中の水分とともに原料充填層下部で凝縮して湿潤層を形成する。しかし、擬似粒子中の水分含有量が低減されているため、循環ガス中の水分含有量も低下し、湿潤層における水分凝縮が緩和されることに加え、古紙スラッジの添加により擬似粒子が強化されているので擬似粒子の崩壊は起らず通気を阻害しない。これにより、充填層の通気が確保され焼結鉱の生産性が維持ないし向上するとともに、焼結鉱の強度、すなわち歩留も維持ないし向上する。
【００３２】
また、焼結反応に際し少なくとも９００℃以上（最高１２５０〜１３００℃）の高温の状態が２〜４分間維持される間に、古紙スラッジ中の有機繊維であるセルロース木質繊維と、有機粘着材であるリグニンとは容易に燃焼消失するので焼結反応を阻害することはなく、むしろこれらの燃焼による燃焼熱と、古紙スラッジ中の粘土質物質が鉄鉱石等とスラグ反応して融液を生成することにより焼結反応が促進され、焼結鉱の強度が上昇する。また、これら有機物の燃焼熱が有効利用できるので固体燃料を節減することができる。
【００３３】
古紙スラッジの添加量は、あまり少なすぎては効果が十分得られず、逆に多すぎると粘土質物質の量が増えて高炉のスラグ量が増加する。さらに、古紙スラッジ中にはＺｎ、Ｃｌ、Ｎａ、Ｋ等の低融点化合物を生成する成分が含有されている（表１参照）ため、高炉内で付着物を形成する等の問題が生じる。このため、古紙スラッジの添加量は、第１系列の造粒原料に対し、乾量基準で、好ましくは０．０１〜１．０質量％、より好ましくは０．０２〜０．２質量部、さらに好ましくは０．０３〜０．１質量部、特に好ましくは０．０３〜０．０５質量部とする。また、第２系列の造粒原料に対しても古紙スラッジを添加する場合は、第１系列の造粒原料中の添加濃度の５０％以下の添加濃度となる添加量に制限することが推奨される。
【００３４】
古紙スラッジを添加する代わりに、有機繊維、粘土質物質、および有機粘着材をそれぞれ所定量ずつ混合して用いてもよい。これらの添加量は、あまり少なすぎては効果が十分得られず、逆に多すぎると焼結鉱の製造コストが高くなりすぎる。また、粘土質物質の添加量が多すぎると高炉のスラグ量が増加する。このため、第１系列の造粒原料に対し、乾量基準で、有機繊維の添加量は、好ましくは０．０１〜１．０質量部、より好ましくは０．０１〜０．２質量部、さらに好ましくは０．０１〜０．０７質量％、特に好ましくは０．０２〜０．０５質量％とする。また、粘土質物質の添加量は、好ましくは０．０１〜１．０質量％、より好ましくは０．０１〜０．２質量％、さらに好ましくは０．０１〜０．０７質量％、特に好ましくは０．０２〜０．０５質量％とする。また、有機粘着材の添加量は、好ましくは０．０００５〜０．１質量％、より好ましくは０．００１〜０．０２質量％、さらに好ましくは０．００２〜０．０１質量％、特に好ましくは０．００３〜０．００５質量％とする。また、第２系列の造粒原料に対してもこれらの物質を添加する場合は、第１系列の造粒原料中の添加濃度の５０％以下の添加濃度となる添加量に制限することが推奨される。
【００３５】
有機繊維としては、例えば、古紙を解砕したセルロース木質繊維を用いてもよいし、布染色工程から発生する織物繊維を含有する布染色スラッジを用いてもよいし、これらを混合して用いてもよい。粘土質物質としては、例えば、粘土、ベントナイト、カオリン、タルク等を単独又は２種以上混合して用いてもよい。有機粘着材としては、リグニンの他に、例えば、澱粉、デキストリン、糖蜜等を単独又は２種以上混合して用いてもよい。あるいは、古紙スラッジにこれらのものを適宜追加して有機繊維、粘土質物質、および有機粘着材の割合を調整して用いてもよい。
【００３６】
なお、本発明は、排ガス循環操業に対してのみでなく、大気吸引操業に対しても適用できる。この場合、吸引ガス中の水分含有量は、もともと排ガス循環操業ほど高くならないため、必ずしも造粒水分を低減させる必要性はない。このため、造粒水分を低減する代わりに、上記添加剤の添加による造粒性の向上効果に見合う分だけ、生石灰の添加量を低減することができる。すなわち、副原料として添加する石灰石または生石灰の配合量については、造粒原料中におけるＣａＯ成分の総質量を一定に維持しつつ、古紙スラッジの添加量を多くするにしたがい生石灰の配合量を減少し、代わりに石灰石の配合量を増加してもよい。つまり、古紙スラッジの添加量の増大により擬似粒子が強化されるのでバインダーとしての生石灰の添加量を削減できることになる。また、古紙スラッジを添加しない従来法においては、単に生石灰を減少して石灰石の配合量を増加すると焼結時に石灰石が分解吸熱（ＣａＣＯ₃→ＣａＯ＋ＣＯ₂）して熱不足となり焼結鉱強度が低下するため、固体燃料配合量を増加させる必要があった。これに対し、本発明によれば、この石灰石の分解吸熱分を古紙スラッジ中の有機繊維と有機粘着材の燃焼発熱分で補うことができるのでこのような問題は生じない。
【００３７】
【実施例】
本発明の効果を確認するため、焼結鍋試験装置を用いて以下の実験を実施した。
【００３８】
（実施例１）
実験に用いた焼結用鉱石原料の化学成分と比表面積を表１に示す。表１より結晶水含有量：３．０質量％以上及び／又は比表面積：３．０ｍ²／ｇ以上の鉱石Ｃ、Ｒ、Ｙを第１系統の原料とし、それ以外の鉱石Ｈ、Ｄを第２系列の原料とした（なお、本実施例では焼結返鉱を用いなかった）。添加剤である古紙スラッジは表２に示す成分のものを用いた。なお、古紙スラッジは、事前に乾燥したのちボールミルで粉砕して粒度−０．１２５ｍｍに粉状化したものを用いた。
【００３９】
【表１】

【００４０】
【表２】

【００４１】
そして、発明例１の混合原料を以下のようにして作製した。先ず、表３に示す配合条件で、第１および第２系列ごとに、原料鉱石に副原料（石灰石、珪石、生石灰）およびコークス粉を添加し、さらに第１系列側にのみ添加剤として粉状の古紙スラッジを添加し、造粒水分を加えてドラムミキサーにより擬似粒子化し造粒原料とした。その後、第１系列および第２系列の造粒原料をミキサーで混合して混合原料とした。
【００４２】
【表３】

【００４３】
また、比較例１の混合原料として、表３における添加剤の添加を一切行わず、その他の配合条件は上記本発明例と同一として混合原料を作製した。
【００４４】
また、比較例２−１の混合原料として、表３における第１系列側のみへの添加剤の添加を、第１および第２系列両方に振り分け、造粒原料中の添加剤の濃度が両系列で等しくなるように行い、その他の配合条件は上記本発明例と同一として混合原料を作製した。
【００４５】
これら３種類（発明例１、比較例１、比較例２−１）の混合原料について、それぞれ造粒性指数（ＧＩ）および充填層の通気性指数（ＪＰＵ）を測定した。
【００４６】
造粒性指数ＧＩは以下の式（１）で求められる。
【００４７】
ＧＩ＝（Ａ₁−Ｂ₁）／Ａ₁×１００ …（１）
ここに、Ａ₁：造粒原料（擬似粒子）を水洗した後の粒子中の−０．２５ｍｍ，質量％、Ａ₂：造粒原料（擬似粒子）中の−０．２５ｍｍ，質量％
【００４８】
また、充填層の通気性指数ＪＰＵは以下のようにして求められる。すなわち混合原料を直径１００ｍｍ、高さ３００ｍｍの焼結鍋に充填し、冷間にて一定吸引圧で大気を吸引しそのときの吸引ガス流量を測定することによって、以下の式（２）で求められる。
【００４９】
ＪＰＵ＝（Ｆ／Ａ）・〔ｈ／（ｓ／９．８０６６５）〕^0.6 …（２）
ここに、Ｆ：吸引ガス流量（ｍ³（標準状態）／ｍｉｎ）、Ａ：充填層断面積（ｍ²）、ｈ：充填層高さ（ｍ）、ｓ：吸引圧力（ｋＰａ）
【００５０】
実験結果を図１および図２に示す。
【００５１】
図１は、各混合原料の造粒性指数ＧＩを比較して示すグラフ図である。図１より明らかなように、添加剤無添加の比較例１に比べ、添加剤を均一に添加した比較例２−１の方が造粒性指数ＧＩが高くなっており、添加剤の添加による擬似粒子化の促進の効果が見られるが、添加剤を高保水能鉱石側に重点的に添加した発明例１では、比較例２−１と添加剤の平均濃度は同じであるにも関わらず、さらにＧＩが上昇し、より擬似粒子化が促進されることが確認された。
【００５２】
図２は、各混合原料の充填層の通気性指数ＪＰＵを比較して示すグラフ図である。図２より明らかなように、添加剤無添加の比較例１に比べ、比較例２−１の方が通気性指数ＪＰＵが高くなっているが、発明例１ではさらにＪＰＵが上昇することが認められる。この実験結果からも、本発明により、擬似粒子化が促進され、その結果、原料充填層の通気性も向上することが確認された。
【００５３】
（実施例２）
本実施例では、添加剤の添加を粉状で行うことに代えて、スラリー状で添加した。すなわち、表１に示す成分の古紙スラッジに造粒水を添加してミキサーで解砕しスラリー状の添加剤とし、添加剤の添加総量は、混合原料（表３の[F]）に対し０．０３５質量％とした。そして、発明例２の混合原料として、添加剤濃度１．２質量％のスラリーを造粒水分として第１系列のみに添加する以外は上記実施例１の発明例１（表３参照）と同一の配合条件で混合原料を作製した。また、比較例２−２の混合原料として、添加剤濃度０．５質量％のスラリーを造粒水分として第１系列および第２系列両方に添加する以外は、上記実施例１の比較例２−１と同一の配合条件で混合原料を作製した。
【００５４】
発明例２、比較例１（上記実施例１の比較例１と同じもの）、比較例２−２の混合原料について、それぞれ造粒性指数（ＧＩ）および充填層の通気性指数（ＪＰＵ）を測定した。実験結果を図３および図４に示す。図３は、各混合原料の造粒性指数ＧＩを比較して示すグラフ図であり、図４は、各混合原料の充填層の通気性指数ＪＰＵを比較して示すグラフ図である。図３および図４は、それぞれ実施例１の図１および図２と同様の傾向を示すことが明らかであり、これより、添加剤をスラリー状で添加しても粉状で添加するのと同様の作用効果が得られることが確認された。
【００５５】
（実施例３）
次に、上記実施例１の各混合原料について、第１系列および第２系列の両方とも造粒水分量を７質量％から６．４質量％および５．９質量％に順次減少させ、その他の配合条件は実施例１と同一として（すなわち、添加剤の添加は粉状に戻して）混合原料を作製し、造粒性指数ＧＩと充填層の通気性指数ＪＰＵを測定した。
【００５６】
実験結果を図５および図６に示す。図５は、造粒水分量と造粒性指数ＧＩとの関係を示すグラフ図であり、図６は、造粒水分量と通気性指数ＪＰＵとの関係を示すグラフ図である。両図において、破線は、添加剤を添加しない比較例１について造粒水分量を逐次減少させた場合の実験結果を示すものであり、実線は、造粒水分量の逐次減少（７．０質量％→６．４質量％→５．９質量％）に併せ、添加剤を無添加（比較例１）→均一添加（比較例２−１）→高保水能鉱石側への重点添加（発明例１）へと順次変更した場合の実験結果を示すものである。
【００５７】
図５より明らかなように、通常、造粒水分量を減少させると造粒性指数ＧＩが低下し（破線参照）、擬似粒子化が困難になるものである。ところが、添加剤を各系列の造粒原料に均一に添加することにより、造粒水分量を減少させても、却って造粒性指数ＧＩが上昇しており（比較例２−１）、添加剤の添加により造粒性が改善されることがわかる。さらに、添加剤を高保水能鉱石側に重点的に添加することにより、造粒水分量を一層減少させても、造粒性指数ＧＩはさらに上昇し（発明例１）、本発明は格段に優れた造粒性改善効果を有することが確認された。（なお、図１の本発明例（造粒水分７．０質量％）と図５の本発明例（造粒水分５．９質量％）とを比較すると、造粒水分量を減少させた図５の方が造粒性指数ＧＩが高くなっており、図５の破線の傾向と逆の傾向となっている。この理由の詳細は現時点では不明であるが、発明例１では、５．９質量％近傍が最適な造粒水分量に相当し、７．０質量％では造粒水分が過剰となり、却って造粒性が悪化したものと想定される。）
【００５８】
また、図６に示されるように、通常、造粒水分量を減少させると、上述したように擬似粒子化が困難になり充填層の通気性指数ＪＰＵが低下し（破線参照）、焼結鉱の生産性の低下や強度低下の原因となるものである。ところが、添加剤を各造粒原料に均一に添加することにより、造粒水分量を減少させても、通気性指数ＪＰＵはほぼ同じレベルに維持されており（比較例２−１）、添加剤の添加により造粒性が改善された結果、擬似粒子化が促進され、充填層の通気性の悪化が防止されたものと考えられる。さらに、添加剤を高保水能鉱石側に重点的に添加することにより、造粒水分量を一層減少させても、通気性指数ＪＰＵはほぼ同じレベルに維持されていることがわかる（発明例１）。この実験結果から、本発明は格段に優れた造粒性改善効果を有し、擬似粒子化がさらに促進されるため、充填層の通気性を維持しつつ、大幅に造粒水分量を減少できることが確認された。
【００５９】
（実施例４）
次に、上記実施例１の各混合原料について、第１系列および第２系列の両方とも生石灰の添加量を２．０質量％から１．０質量％および無添加に順次減少させ、その他の配合条件は実施例１と同一として混合原料を作製し、造粒性指数ＧＩと充填層の通気性指数ＪＰＵを測定した。
【００６０】
実験結果を図７に示す。図７は、各混合原料についての、生石灰添加量と充填層の通気性指数ＪＰＵとの関係を示すグラフ図である。図７に示されるように、通常、生石灰の添加量が減少するとともに通気性指数ＪＰＵが低下し、通気性が悪化する傾向が見られるため（比較例１）、生石灰の使用量を削減することは困難であった。ところが、添加剤を各系列の混合原料に均一に添加することにより、通気性指数ＪＰＵが上昇するため（図２の比較例２−１参照）、通気性指数ＪＰＵを維持しつつ生石灰添加量を低減できる（２．０質量％→約１．０質量％）ことがわかった（比較例２−１）。さらに、添加剤を高保水能鉱石側に重点的に添加することにより、通気性指数ＪＰＵを一層上昇できるため（図２の発明例１参照）、通気性指数ＪＰＵを維持しつつ生石灰添加量をさらに低減できる（→約０．５質量％）ことがわかった（発明例１）。
【００６１】
【発明の効果】
以上より、本発明によれば、排ガス循環操業において高保水能鉱石を多量使用しても、過大な設備コストを不要とし、かつ製造コストを著しく増大させることなく、循環排ガス中の水分含有量を維持ないし低減して焼結層の通気性を維持ないし改善し、製品焼結鉱の生産性および歩留を維持ないし向上できる。
【００６２】
また、吸引ガス中の水分含有量を低減する必要のない場合には、生石灰など高価なバインダーの使用量を大幅に削減できるため、焼結鉱の製造コストが低減できる。
【図面の簡単な説明】
【図１】実施例１（添加剤を粉状で添加する場合）における、各混合原料の造粒性指数ＧＩを比較して示すグラフ図である。
【図２】実施例１（添加剤を粉状で添加する場合）における、各混合原料の充填層の通気性指数ＪＰＵを比較して示すグラフ図である。
【図３】実施例２（添加剤をスラリー状で添加する場合）における、各混合原料の造粒性指数ＧＩを比較して示すグラフ図である。
【図４】実施例２（添加剤をスラリー状で添加する場合）における、各混合原料の充填層の通気性指数ＪＰＵを比較して示すグラフ図である。
【図５】実施例３において、造粒水分量と造粒性指数ＧＩとの関係を示すグラフ図である。
【図６】実施例３において、造粒水分量と充填層の通気性指数ＪＰＵとの関係を示すグラフ図である。
【図７】実施例４において、各混合原料についての、生石灰添加量と充填層の通気性指数ＪＰＵとの関係を示すグラフ図である。
【図８】吸引ガス中水分濃度と焼結鉱の落下強度との関係を示すグラフ図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a sintered ore, and more particularly to a method for producing a mixed raw material for sintering that can achieve high productivity without deteriorating the quality of the sintered ore in exhaust gas circulation operation.
[0002]
[Prior art]
Usually, the sintered ore which is a raw material for blast furnaces is manufactured in the following processes.
[0003]
First, iron ore powder and sintered ore, which are raw materials for sintering with a particle size of about 10 mm or less, auxiliary materials such as silica stone, limestone, serpentine with a particle size of about 3 mm or less, coke powder, coal powder, etc. Mixing solid fuel with flocculant such as quick lime and slaked lime, adding blended water and kneading followed by pseudo-particle formation (coarse particles are used as nuclei and fine particles are attached to the surface by the surface tension of water. The mixed raw material thus formed) is filled on a pallet of a sintering machine (for example, DL type sintering machine), and the solid fuel in the mixed raw material at the top of the layer is ignited. After ignition, in the process of burning the solid fuel while sucking air downwards and sintering the mixed raw material (raw material packed layer) filled with this combustion heat to make a sintered cake, after drying the mixed raw material, By heating to 1150-1200 degreeC, a melt is produced | generated by the slag reaction of the iron ore in a mixed raw material, and an auxiliary raw material. Liquid melt sintering of the iron ore powder is performed with this melt, and after cooling, the required strength of the sintered ore is obtained by combining the iron ore powder with this melt.
[0004]
In recent years, exhaust gas circulation type sintering machines have been widely adopted as sintering machines. The exhaust gas circulation type sintering machine improves the disadvantages of the conventional atmospheric suction type sintering machine, reduces the amount of exhaust gas discharged from the sintering machine system and the total amount of NOx, and further reduces the heat of the exhaust gas. It is intended to improve collection and productivity.
[0005]
For example, Japanese Patent Laid-Open No. 5-43951 discloses exhaust gas from an ignition furnace area and a rear area wind box (wind box) of a sintering machine, Exhaust gas in the rear region is circulated to the front of the sintering machine after the ignition furnace, and an exhaust gas circulation operation method is proposed in which the oxygen concentration in each circulated exhaust gas is 18% or more. In this operation method, moisture in the circulating exhaust gas is controlled to 10% or less, preferably 7% or less, thereby preventing condensation in the exhaust gas circulation path and promoting combustion in the sintered combustion layer in the middle and rear of the sintering machine. It is supposed to be able to plan.
[0006]
On the other hand, due to changes in iron ore resources in recent years, the ratio of high water-bearing ores such as Australian pisolite ores and maramamba ores to the raw materials for sintering ore is increasing. Since these highly water-retaining ores have a large number of micropores on the surface, it is necessary to add a larger amount of water than conventional iron ore during granulation in order to stably form pseudo-particles. . This granulated water evaporates during the sintering and moves into the exhaust gas, which is recirculated to the sintering machine, so that the moisture concentration in the circulating exhaust gas tends to further increase. When the water content in the circulating exhaust gas exceeds 10%, a large amount of water condenses in the lower part (wet zone) of the raw material packed bed during sintering, so that the pseudo particles are liable to be collapsed by the load from the upper part. For this reason, the air permeability of the mixed raw material deteriorates and the time required for sintering becomes long, the production efficiency of the sintered ore decreases, or the strength of the sintered ore decreases and the yield decreases. (See FIG. 8).
[0007]
As a countermeasure, it is conceivable to reduce the moisture concentration in the circulating exhaust gas by sintering the granulated pseudo particles after drying them in advance.
[0008]
For example, Japanese Patent Laid-Open No. 61-238925 discloses a method of heating and drying a mixed raw material that has been quasi-particled in a mixer by a moving pallet dryer using exhaust gas from a sintering machine cooler. It has been proposed that the air permeability of the sintered bed (raw material packed layer) can be improved by reducing the amount to 3 to 4% by weight. However, this method has a problem that an excessive equipment cost is required to dry the pseudo particles (mixed raw material).
[0009]
In JP-A-6-330189, a sintered raw material (mixed raw material) whose water content is adjusted to 5.0% or less is charged into the surface layer of the raw material packed layer on the sintering pallet and then fired. By doing so, a method for greatly improving the yield of the upper part of the sintered layer has been proposed. However, when the granulation moisture is simply reduced, the granulation property of the raw ore is greatly lowered and the pseudo-particle formation becomes insufficient, so that the air permeability of the packed bed is lowered, and as a result, the sintered ore There is a problem that productivity is rather lowered.
[0010]
In JP-A-6-330189 and JP-A-8-14863, after forming a raw material packed layer on a sintering pallet and before igniting in an ignition furnace, high temperature gas, microwave heating, etc. A method of drying the raw material packed layer over the entire thickness is proposed. However, as in the above-mentioned Japanese Patent Application Laid-Open No. 61-238925, these methods also require excessive equipment modification to dry the raw material packed bed, and additionally require additional heating energy, so There is a problem that the manufacturing cost increases.
[0011]
[Problems to be solved by the invention]
Therefore, the object of the present invention is to maintain the water content in the circulating exhaust gas without making excessive equipment cost unnecessary and significantly increasing the manufacturing cost even if a large amount of high water retention ore is used in the exhaust gas circulation operation. Another object of the present invention is to provide a method for producing a sintered ore that can reduce or maintain or improve the air permeability of the raw material packed bed and maintain or improve the productivity and yield of the product sintered ore.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors paid attention to the additive of the sintered mixed raw material and conducted various studies on the kind, combination, addition amount, addition method, and the like of the additive. As a result, it has been found that the above-mentioned problems can be solved by selectively adding a large amount of water retaining ore as an additive to a combination of organic fiber, clayey material, and organic adhesive material.
[0013]
  That is, claim 1Described inInvention of the ore material for sintering,"High water retention oreCrystal water content as: 3.0% by mass or more and / or specific surface area: 3.0 m ² / G ore "Sintering raw material splitting step that divides into two parts into the first line of raw materials and the second line of raw materials composed of other ores and the second part of the sintering raw material splits composed of other ores Adding a secondary raw material and a solid fuel to the raw material of the process and the first system, and further adding an additive composed of an organic fiber, a clayey material, and an organic adhesive material; A first system granulation step for granulating the granule raw material, and a secondary raw material and a solid fuel are added to the second system raw material, and further, if necessary, the additive is added to the second system granulation raw material. System granulation step, a raw material mixing step of mixing the first system and the second system of granulation raw materials to make a mixed raw material, and a sintering step of sintering the mixed raw material by a conventional method A method for producing a sintered ore comprising:In the granulation raw material of the first system, 0.01 to 1.0% by mass of organic fiber, 0.01 to 1.0% by mass of a clayey substance, and 0.0005 to an organic adhesive on a dry basis. 0.1% by mass and each mass% of organic fiber, clayey material, and organic adhesive material to be included in the second-system granulated raw material in the first-system raw material. 50% or less of each mass% of organic fiber, clayey material, and organic adhesive contained inIs a method for producing a sintered ore.
[0014]
When granulated by adding additives consisting of organic fibers, clayey substances, and organic adhesives to highly water-bearing ores, the organic fibers have water absorption, so water absorption into the core particles is prevented and granulation of raw materials is performed. And it becomes possible to make pseudo particles with a small amount of granulated water. Therefore, usually, the ore material for sintering made of multi-brand ore is divided in advance into a raw material containing a high water-retaining ability ore (raw material of the first system) and another raw material (raw material of the second system). And it is good to add the additive which consists of said organic fiber, a clayey substance, and an organic adhesive material only to the direction of the raw material side of 1st system | system | group, or to add selectively many.
[0015]
In addition, the organic fiber itself and the clay material are sparingly water-soluble, but the organic adhesive is easily water-soluble, so it dissolves in the granulated water and penetrates into the contact point between the organic fiber and the clay material to join them together. To do. Since this joined material enters between particles such as raw ore and limestone to increase the friction between the particles, the spurious particles are prevented from collapsing even in the wet zone. Therefore, you may add the said additive also to the 2nd raw material side. In this case, since the second raw material side does not contain high water retention ore, there is no problem with granulation, so the additive concentration of the additive is lower than that of the first raw material side. Good. As a result, the air permeability of the raw material packed bed is remarkably improved, and the productivity of sinter production is dramatically improved. Organic fibers and organic adhesives are burned during sintering and used as fuel, so the amount of solid fuel such as coke and coal can be reduced, and clayey substances react with iron ore and slag to react with the melt. To promote the sintering reaction.
[0016]
  Here, as a high water retention capacity ore, crystal water content: 3.0 mass% or more and / or specific surface area: 3.0 m ² / G or more is limited to the ore of crystal water content: 3.0% by mass or more and / or the specific surface area is 3.0m ² / G ore shows a particularly high water retention capacity, and by selectively adding the additive to ores that satisfy these conditions, granulation can be improved more effectively. is there.
[0017]
  Also,The above effects cannot be sufficiently obtained if the amount of organic fiber, clayey material, or organic adhesive is too small. On the other hand, if the amount is too large, the production cost of sintered ore becomes too high. If too much material is added, the amount of slag in the blast furnace increases.TheIt should be noted that the amount of organic adhesive added may be significantly smaller than the amount of organic fiber and clayey material added, even if there is little organic adhesive, it dissolves in the mixing water of the sintering raw material and organic fiber and clay This is because the material is invaded and arranged at the point of contact with the substance, and serves to join the two. Moreover, the addition concentration on the second granulation raw material side is limited to 50% or less of the addition concentration of the first granulation raw material. The addition exceeding 50% is compared with the effect of improving the strength of the pseudo particles. This is because the effect of increasing the production cost of sintered ore and increasing the amount of slag in the blast furnace becomes larger.
[0018]
Among the above additives, if the length of the organic fiber is too short, the frictional force is small and the above-mentioned effects are not sufficiently exhibited. Becomes non-uniform and the above-mentioned effects are diminished. Therefore, it is preferable that a considerable amount (for example, 80% by mass or more) of fibers having a length of 1 to 2000 μm is present.
[0019]
Moreover, as an organic fiber, for example, cellulose wood fiber, a textile fiber, or a mixture thereof etc. As a clayey substance, for example, mainly 20-50 mass% SiO₂20-50 mass% Al₂O_Three5-20 mass% CaCO_Three2-10 wt% MgO, 1-8 wt% Fe₂O_ThreeFor example, lignin, starch, dextrin, molasses, or a mixture thereof can be used as the substance composed of the above and the organic adhesive material. Since these substances are relatively inexpensive and easy to secure, the productivity of sinter production can be improved at low cost.
[0020]
  ClaimDescribed in 2The invention according to claim 2 is characterized in that the additive comprising the organic fiber, the clay-like material and the organic adhesive material is used paper sludge.1It is a manufacturing method of the described sintered ore.
[0021]
  Waste paper sludge is obtained by separating and recovering the suspended matter contained in the waste liquid after removing pulp from the waste paper suspension slurry obtained by adding a solution containing an alkali agent or the like in the waste paper recycling process to break up the waste paper. Accordingly, the waste paper sludge contains a considerable amount of cellulose wood fibers, which are relatively short organic fibers. In addition, the inorganic filler of waste paper and inorganic pigments such as bentonite, talc, limestone, dolomite, etc. are concentrated and further contain lignin, which is an organic adhesive material. ClaimInvention described in 1The effect of can be obtained. Furthermore, conventionally, most of the waste paper sludge has been dehydrated or dried and then disposed of in landfills or incineration, which has required a large amount of cost. However, according to the present invention, by using this waste paper sludge as an additive for sintered ore produced in large quantities, it not only can be effectively used as a resource and energy, but also contributes to prevention of environmental pollution. . Japanese Patent Application Laid-Open No. 7-18344 discloses a method of using waste paper itself, not waste paper sludge, for the production of sintered ore. However, unlike waste paper sludge, waste paper is composed of relatively long fibers, and when added to the sintering raw material, the fibers are not disaggregated and need to be crushed separately. The effect of the present invention cannot be achieved because it is very small compared to the amount of the above.
[0022]
[0023]
[0024]
DETAILED DESCRIPTION OF THE INVENTION
One preferred embodiment of the present invention is shown below.
[0025]
The raw material ore for sintering is classified into high water retaining capacity ore and other ores according to brand. Classification may be performed based on the crystal water content and the specific surface area, which are closely related to the water retention capacity. Here, the one-point BET specific surface area measured by the gas adsorption method was employ | adopted for the specific surface area. Separately, as a result of investigating the relationship between the water retention capacity, the crystallization water content and the specific surface area, the crystallization water content is 3.0% by mass or more and / or the specific surface area: 3.0 m.²It was revealed that the water retention capacity was particularly high when the amount was / g or more. Therefore, the ore of the brand satisfying this condition is used as a high water retention ore as the first series raw material, and the other crystal water content is less than 3.0 mass% and the specific surface area is 3.0 m.²It is preferable to use ore less than / g as the second series raw material (since sintered ore is low in water retention capacity, it may be included in the second series raw material). In consideration of the balance of the amount of raw material between the first series and the second series, a part of ore that is not a high water retention capacity ore may be used as the first series raw material.
[0026]
Then, a predetermined amount of limestone and quicklime as a secondary raw material and a small amount of silica stone if necessary, a predetermined amount of coke powder or anthracite coal powder as a solid fuel, and a predetermined amount of waste paper sludge are added to the first series of raw materials Then, granulated water is added and kneaded with a first drum mixer and pseudo-granulated to obtain a first series of granulated raw materials. Since a considerable amount of waste paper sludge is present in the raw material, the granulated water can be reduced as described above, and the water content in the pseudo particles can be reduced.
[0027]
In addition, since waste paper sludge is usually in the form of a paper clay-like lump containing about 80 to 120% by weight (dry basis), it is pulverized in advance with a ball mill or the like after dehydration and drying. It should be added in powder form. Or you may use what made a slurry form by adding and stirring a part or all of granulated water to lump-like waste paper sludge. The amount of waste paper sludge added is 0.01 to 1.0% by weight of organic fiber on a dry basis in the granulation raw material, depending on the content of organic fiber, clayey substance, and organic adhesive in waste paper sludge. The clay material may be appropriately adjusted so as to include 0.01 to 1.0 mass% and the organic adhesive material 0.0005 to 0.1 mass%.
[0028]
On the other hand, for the second series of raw materials, a secondary raw material and a solid fuel are added, and further, waste paper sludge is added if necessary, an appropriate amount of granulated water is added, and a second drum different from the first series is added. The mixture is kneaded with a mixer and pseudo-granulated to obtain a mixed raw material of the second series. In addition, when adding used paper sludge, it adjusts so that the addition density | concentration of the used paper sludge in a 2nd series granulation raw material may be 50% or less of the addition density | concentration of the used paper sludge of a 1st series mixed raw material.
[0029]
The pseudogranulated first and second granulated raw materials are mixed together in another mixer to obtain a mixed raw material.
[0030]
The mixed raw material thus produced is filled on a pallet of an exhaust gas circulation type sintering machine, and the solid fuel in the mixed raw material in the surface layer portion is ignited. After ignition, the circulating gas is sucked downward to burn the solid fuel, and the mixed raw material filled with the combustion heat is sintered to form a sintered cake.
[0031]
The water evaporated in the process from the ignition to the production of the sintered cake is condensed in the lower part of the raw material packed bed together with the water in the sucked circulating gas to form a wet layer. However, since the moisture content in the pseudo-particles has been reduced, the moisture content in the circulating gas is also reduced, the moisture condensation in the wet layer is alleviated, and the pseudo-particles are strengthened by the addition of waste paper sludge. Therefore, the pseudo particles do not collapse and do not hinder aeration. Thereby, the ventilation of the packed bed is ensured, and the productivity of the sintered ore is maintained or improved, and the strength of the sintered ore, that is, the yield is also maintained or improved.
[0032]
Further, during the sintering reaction, while the high temperature state of at least 900 ° C. or higher (maximum 1250 to 1300 ° C.) is maintained for 2 to 4 minutes, it is a cellulose wood fiber that is an organic fiber in waste paper sludge and an organic adhesive material. Lignin easily burns away and does not hinder the sintering reaction. Rather, the combustion heat from the combustion and the clay material in waste paper sludge react with iron ore to produce a melt. This promotes the sintering reaction and increases the strength of the sintered ore. Moreover, since the combustion heat of these organic substances can be used effectively, solid fuel can be saved.
[0033]
If the amount of waste paper sludge is too small, the effect is not sufficiently obtained. On the other hand, if the amount is too large, the amount of clayey material increases and the amount of slag in the blast furnace increases. Furthermore, since waste paper sludge contains components that generate low melting point compounds such as Zn, Cl, Na, and K (see Table 1), problems such as formation of deposits in the blast furnace arise. For this reason, the added amount of waste paper sludge is preferably 0.01 to 1.0% by mass, more preferably 0.02 to 0.2 parts by mass, on a dry basis, with respect to the first series of granulated raw materials. More preferably, it is 0.03-0.1 mass part, Most preferably, it is 0.03-0.05 mass part. In addition, when waste paper sludge is added to the second series of granulated raw materials, it is recommended to limit the amount to an additive concentration that is 50% or less of the additive concentration in the first series of granulated raw materials. The
[0034]
Instead of adding waste paper sludge, organic fibers, clayey substances, and organic adhesive materials may be mixed and used in predetermined amounts. If the added amount is too small, the effect cannot be obtained sufficiently. Conversely, if the added amount is too large, the production cost of the sintered ore becomes too high. Moreover, when there is too much addition amount of a clayey substance, the amount of slag of a blast furnace will increase. For this reason, the amount of organic fiber added is preferably 0.01 to 1.0 parts by weight, more preferably 0.01 to 0.2 parts by weight, based on the dry weight, with respect to the first series of granulated raw materials. More preferably, it is 0.01-0.07 mass%, Most preferably, it is 0.02-0.05 mass%. Further, the amount of the clayey substance added is preferably 0.01 to 1.0% by mass, more preferably 0.01 to 0.2% by mass, still more preferably 0.01 to 0.07% by mass, and particularly preferably. Is 0.02 to 0.05 mass%. The amount of the organic adhesive added is preferably 0.0005 to 0.1% by mass, more preferably 0.001 to 0.02% by mass, still more preferably 0.002 to 0.01% by mass, and particularly preferably Is 0.003 to 0.005 mass%. In addition, when adding these substances to the second series of granulated raw materials, it is recommended to limit the addition amount to 50% or less of the additive concentration in the first series of granulated raw materials. Is done.
[0035]
As the organic fibers, for example, cellulose wood fibers obtained by pulverizing waste paper may be used, cloth dye sludge containing fabric fibers generated from the cloth dyeing process may be used, or these may be mixed and used. Also good. As the clay material, for example, clay, bentonite, kaolin, talc and the like may be used alone or in admixture of two or more. As the organic adhesive material, in addition to lignin, for example, starch, dextrin, molasses and the like may be used alone or in admixture of two or more. Alternatively, these may be appropriately added to the used paper sludge to adjust the proportions of organic fiber, clayey substance, and organic adhesive material.
[0036]
The present invention can be applied not only to exhaust gas circulation operation but also to air suction operation. In this case, the moisture content in the suction gas is not necessarily as high as that in the exhaust gas circulation operation, and thus it is not always necessary to reduce the granulated moisture. For this reason, instead of reducing granulation moisture, the amount of quicklime added can be reduced by an amount commensurate with the effect of improving the granulation property by the addition of the additive. In other words, with regard to the amount of limestone or quicklime added as an auxiliary material, the amount of quicklime is reduced as the amount of used paper sludge increases while maintaining the total mass of the CaO component in the granulated material constant. Alternatively, the amount of limestone may be increased. That is, since the pseudo particles are reinforced by increasing the amount of waste paper sludge added, the amount of quick lime added as a binder can be reduced. Further, in the conventional method in which waste paper sludge is not added, when the amount of limestone is simply increased by reducing quick lime, the limestone decomposes and absorbs endothermic (CaCO) during sintering._Three→ CaO + CO₂) And the strength of sintered ore is reduced, so that it is necessary to increase the amount of solid fuel. On the other hand, according to the present invention, the decomposition endothermic component of limestone can be supplemented by the combustion exothermic component of the organic fiber and the organic adhesive material in the waste paper sludge, so that such a problem does not occur.
[0037]
【Example】
In order to confirm the effect of the present invention, the following experiment was conducted using a sintering pot test apparatus.
[0038]
(Example 1)
Table 1 shows the chemical composition and specific surface area of the sintering ore raw material used in the experiment. From Table 1, crystal water content: 3.0 mass% or more and / or specific surface area: 3.0 m²/ G ore C, R, and Y were used as the first series raw material, and the other ores H and D were used as the second series raw material (note that sintered ore was not used in this example). The waste paper sludge which is an additive used the component shown in Table 2. The used paper sludge was dried in advance and then pulverized with a ball mill and pulverized to a particle size of -0.125 mm.
[0039]
[Table 1]

[0040]
[Table 2]

[0041]
And the mixed raw material of the invention example 1 was produced as follows. First, under the blending conditions shown in Table 3, for each of the first and second series, auxiliary raw materials (limestone, quartzite, quicklime) and coke powder are added to the raw ore, and powder is added as an additive only on the first series side. Waste paper sludge was added, granulated water was added, and the mixture was pseudo-pulverized with a drum mixer to obtain a granulated raw material. Thereafter, the first and second series of granulated raw materials were mixed with a mixer to obtain mixed raw materials.
[0042]
[Table 3]

[0043]
In addition, as the mixed raw material of Comparative Example 1, the additive in Table 3 was not added at all, and the other raw material conditions were the same as those of the above-described present invention example to prepare a mixed raw material.
[0044]
Further, as the mixed raw material of Comparative Example 2-1, the addition of the additive only to the first series side in Table 3 is distributed to both the first and second series, and the concentration of the additive in the granulated raw material is both series. The other raw material conditions were the same as those of the above-described example of the present invention, and a mixed raw material was produced.
[0045]
With respect to the mixed raw materials of these three types (Invention Example 1, Comparative Example 1, and Comparative Example 2-1), the granulation index (GI) and the air permeability index (JPU) of the packed bed were measured.
[0046]
The granulation index GI is obtained by the following formula (1).
[0047]
GI = (A₁-B₁) / A₁× 100 (1)
Where A₁: -0.25 mm,% by mass, A in particles after washing granulated raw material (pseudo particles) with water₂: -0.25 mm, mass% in granulated raw material (pseudo particle)
[0048]
Further, the air permeability index JPU of the packed bed is obtained as follows. That is, the mixed raw material is filled into a sintering pot having a diameter of 100 mm and a height of 300 mm, the air is sucked in at a constant suction pressure in the cold, and the suction gas flow rate at that time is measured to obtain the following equation (2). It is done.
[0049]
JPU = (F / A) · [h / (s / 9.80665)]^0.6 ... (2)
Where F: suction gas flow rate (m^Three(Standard state) / min), A: sectional area of packed bed (m²), H: packed bed height (m), s: suction pressure (kPa)
[0050]
The experimental results are shown in FIGS.
[0051]
FIG. 1 is a graph showing a comparison of the granulation index GI of each mixed raw material. As is clear from FIG. 1, the comparative example 2-1 in which the additive was uniformly added had a higher granulation index GI than that in the comparative example 1 in which no additive was added, and this was due to the addition of the additive. Although the effect of promoting the formation of pseudo particles can be seen, in Invention Example 1 in which the additive is added to the highly water-retaining ore side, the average concentration of the additive is the same as that in Comparative Example 2-1. Further, it was confirmed that GI further increased and pseudo-particle formation was further promoted.
[0052]
FIG. 2 is a graph showing a comparison of the permeability index JPU of the packed layer of each mixed raw material. As is clear from FIG. 2, the air permeability index JPU is higher in Comparative Example 2-1 than in Comparative Example 1 in which no additive is added, but it is recognized that JPU further increases in Invention Example 1. It is done. Also from this experimental result, it was confirmed that pseudo-particle formation was promoted by the present invention, and as a result, the air permeability of the raw material packed bed was also improved.
[0053]
(Example 2)
In this example, the additive was added in the form of a slurry instead of being added in the form of a powder. That is, granulated water is added to waste paper sludge having the components shown in Table 1 and crushed with a mixer to obtain a slurry additive. The total amount of additive is 0 with respect to the mixed raw material ([F] in Table 3). 0.035% by mass. And as a mixed raw material of Invention Example 2, the same as Invention Example 1 of Example 1 (see Table 3) except that a slurry having an additive concentration of 1.2% by mass is added only as a granulated water to the first series. A mixed raw material was prepared under blending conditions. Moreover, as a mixed raw material of Comparative Example 2-2, Comparative Example 2 of Example 1 above was added except that a slurry having an additive concentration of 0.5% by mass was added to both the first series and the second series as granulated moisture. A mixed raw material was produced under the same blending conditions as in No. 1.
[0054]
For the mixed raw materials of Invention Example 2, Comparative Example 1 (same as Comparative Example 1 of Example 1 above), and Comparative Example 2-2, the granulation index (GI) and the air permeability index (JPU) of the packed bed are respectively shown. It was measured. The experimental results are shown in FIGS. FIG. 3 is a graph showing a comparison of the granulation index GI of each mixed raw material, and FIG. 4 is a graph showing a comparison of the air permeability index JPU of the packed layer of each mixed raw material. FIG. 3 and FIG. 4 clearly show the same tendency as FIG. 1 and FIG. 2 of Example 1, respectively. From this, it is the same as when the additive is added in the form of a slurry but in the form of a powder. It was confirmed that the following effects were obtained.
[0055]
(Example 3)
Next, for each of the mixed raw materials of Example 1 above, in both the first series and the second series, the amount of granulated water was sequentially reduced from 7% by mass to 6.4% by mass and 5.9% by mass. The blending conditions were the same as in Example 1 (that is, the additive was returned to the powder form) to prepare a mixed raw material, and the granulation index GI and the air permeability index JPU of the packed bed were measured.
[0056]
The experimental results are shown in FIGS. FIG. 5 is a graph showing the relationship between the granulated moisture content and the granulation index GI, and FIG. 6 is a graph showing the relationship between the granulation moisture content and the air permeability index JPU. In both figures, the broken line indicates the experimental results when the granulated water content is sequentially decreased for Comparative Example 1 in which no additive is added, and the solid line indicates the sequential decrease of the granulated water content (7.0 mass). % → 6.4% by mass → 5.9% by mass), additive not added (Comparative Example 1) → uniform addition (Comparative Example 2-1) → important addition to high water retention ore side (invention example) The experimental result when changing to 1) sequentially is shown.
[0057]
As is clear from FIG. 5, normally, when the amount of granulated water is reduced, the granulation index GI is lowered (see the broken line), which makes it difficult to make pseudo particles. However, even if the amount of granulated water is reduced by uniformly adding the additive to each series of granulated raw materials, the granulation index GI is increased (Comparative Example 2-1). It can be seen that the granulation property is improved by the addition of. Furthermore, by adding the additive mainly to the high water-retaining capacity ore side, even if the amount of granulated water is further reduced, the granulation index GI further increases (Invention Example 1), and the present invention is remarkably improved. It was confirmed that it has an excellent granulation improvement effect. (In addition, when the example of this invention (granulated water 7.0 mass%) of FIG. 1 and the example of this invention (granulated water 5.9 mass%) of FIG. 5 has a higher granulation index GI, which is the reverse of the tendency of the broken line in Fig. 5. The details of this reason are unknown at this time, but 5.9 in Invention Example 1. The vicinity of mass% corresponds to the optimum amount of granulation water, and at 7.0 mass%, the granulation water becomes excessive, and it is assumed that the granulation property is deteriorated.)
[0058]
In addition, as shown in FIG. 6, usually, when the amount of granulated water is reduced, as described above, pseudo-particle formation becomes difficult and the air permeability index JPU of the packed bed is lowered (see the broken line). This causes a decrease in productivity and a decrease in strength. However, the air permeability index JPU is maintained at substantially the same level even when the amount of granulated water is reduced by uniformly adding the additive to each granulation raw material (Comparative Example 2-1). As a result of the improvement of the granulation property, the formation of pseudo-particles is promoted, and it is considered that deterioration of the air permeability of the packed bed is prevented. Furthermore, it can be seen that the air permeability index JPU is maintained at substantially the same level even when the granulated water content is further reduced by adding the additive mainly to the high water retention capacity ore side (Invention Example 1). ). From this experimental result, the present invention has a remarkably excellent granulation improvement effect, and further promotes the formation of pseudo-particles, so that the amount of granulated water can be greatly reduced while maintaining the air permeability of the packed bed. Was confirmed.
[0059]
(Example 4)
Next, for each mixed raw material of Example 1 above, the addition amount of quicklime in both the first series and the second series is sequentially reduced from 2.0 mass% to 1.0 mass% and no addition, and other blending The mixed raw material was produced under the same conditions as in Example 1, and the granulation index GI and the air permeability index JPU of the packed bed were measured.
[0060]
The experimental results are shown in FIG. FIG. 7 is a graph showing the relationship between the amount of quicklime added and the air permeability index JPU of the packed bed for each mixed raw material. As shown in FIG. 7, the amount of quicklime is usually reduced and the breathability index JPU is lowered, and the breathability tends to deteriorate (Comparative Example 1). Was difficult. However, since the air permeability index JPU is increased by uniformly adding the additives to the mixed raw materials of each series (see Comparative Example 2-1 in FIG. 2), the amount of quicklime added while maintaining the air permeability index JPU. It was found that it can be reduced (2.0% by mass to about 1.0% by mass) (Comparative Example 2-1). Furthermore, since the air permeability index JPU can be further increased by intensively adding the additive to the high water retention ore side (see Invention Example 1 in FIG. 2), the amount of quicklime added while maintaining the air permeability index JPU. It was found that it could be further reduced (→ about 0.5 mass%) (Invention Example 1).
[0061]
【The invention's effect】
From the above, according to the present invention, even if a large amount of high water retention capacity ore is used in the exhaust gas circulation operation, excessive equipment costs are not required and the water content in the circulating exhaust gas is significantly increased without significantly increasing production costs. By maintaining or reducing, the air permeability of the sintered layer can be maintained or improved, and the productivity and yield of the product sintered ore can be maintained or improved.
[0062]
In addition, when it is not necessary to reduce the moisture content in the suction gas, the amount of expensive binders such as quick lime can be significantly reduced, so that the production cost of sintered ore can be reduced.
[Brief description of the drawings]
FIG. 1 is a graph showing a comparison of granulation index GI of each mixed raw material in Example 1 (when an additive is added in powder form).
FIG. 2 is a graph showing a comparison of air permeability index JPU of packed layers of mixed raw materials in Example 1 (when additives are added in powder form).
FIG. 3 is a graph showing a comparison of granulation index GI of each mixed raw material in Example 2 (when the additive is added in the form of a slurry).
FIG. 4 is a graph showing a comparison of air permeability index JPU of packed layers of mixed raw materials in Example 2 (in the case where an additive is added in a slurry state).
5 is a graph showing the relationship between the amount of granulated water and the granulation index GI in Example 3. FIG.
6 is a graph showing the relationship between the amount of granulated water and the air permeability index JPU of the packed bed in Example 3. FIG.
7 is a graph showing the relationship between the amount of quicklime added and the permeability index JPU of the packed bed for each mixed raw material in Example 4. FIG.
FIG. 8 is a graph showing the relationship between the moisture concentration in suction gas and the drop strength of sintered ore.

Claims

A raw material of the first system containing a raw material for sintering ore containing “ ores having a crystal water content of 3.0% by mass or more and / or a specific surface area of 3.0 m ² / g or more as a highly water-retaining ore” ; A sintering raw material splitting step that divides the raw material into a second system of raw materials composed of other ores;
A secondary raw material and a solid fuel are added to the raw material of the first system, and an additive composed of an organic fiber, a clayey substance, and an organic adhesive material is added to obtain a granulated raw material of the first system. Granulating and performing this first system granulation step;
A second system granulation step of adding the auxiliary material and the solid fuel to the second system raw material, and further adding the additive as necessary to granulate the second system granulated raw material;
A raw material mixing step of mixing the first system and the second system of granulated raw materials to form a mixed raw material;
A sintering step of sintering the mixed raw material by a conventional method;
A method for producing a sintered ore comprising:
In the granulation raw material of the first system, 0.01 to 1.0% by mass of organic fiber, 0.01 to 1.0% by mass of a clayey substance, and 0.0005 to an organic adhesive on a dry basis. 0.1% by mass and
Organic fiber, clayey material, and each mass% of organic adhesive material contained in the second system granulation raw material, organic fiber contained in the first system granulation raw material, and clayey material, A method for producing sintered ore, characterized in that each mass% of the organic adhesive material is 50% or less .

The method for producing sintered ore according to claim 1, wherein the additive is used paper sludge.