JP3806282B2

JP3806282B2 - Method of melting iron-containing cold material

Info

Publication number: JP3806282B2
Application number: JP2000154105A
Authority: JP
Inventors: 一雄大貫; 隆澤井; 安夫武田; 弘明山本; 利一青木; 宏之熊澤; 隆史辻; 忠司真鍋
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2000-05-25
Filing date: 2000-05-25
Publication date: 2006-08-09
Anticipated expiration: 2020-05-25
Also published as: JP2001335822A

Description

【０００１】
【発明の属する技術分野】
本発明は、連続残湯残滓方式の含鉄冷材の溶解方法の改良に関し、特に含鉄冷材、炭材等の原燃料として安価な原燃料を用い、含鉄冷材を溶解して製造する高炭素溶鉄の製造コストを低減する連続残湯残滓方式の含鉄冷材の溶解方法に関するものである。
【０００２】
【従来の技術】
種湯、種溶滓の存在する溶解専用転炉（溶解炉）に含鉄冷材、副材、炭材、酸素を供給して含鉄冷材を加炭溶解し高炭素溶鉄と溶滓を得、倒炉による出湯時に上記高炭素溶鉄の一部を炉内に残し、次回の含鉄冷材加炭溶解操業の種湯として使用すると共に、出湯に引き続く反出湯側への倒炉による排滓時に上記溶滓の一部を炉内に残し、次回の含鉄冷材加炭溶解操業の種溶滓、鉄ダスト飛散抑制溶滓として使用する連続残湯残滓方式の含鉄冷材の溶解方法、溶解専用転炉（溶解炉）から出湯された高炭素溶鉄を別の精錬専用転炉（脱炭炉）で酸素吹錬することにより所要成分の溶鋼を得る転炉製鋼方法は特公平４−７８６８６号公報で公知である。
【０００３】
同公報には、上記転炉製鋼法において、溶解専用転炉で使用するコークス、石炭等の炭材の硫黄含有量が高くて、取鍋に出湯される高炭素溶鉄の硫黄含有量が高い場合、取鍋内の高炭素溶鉄に脱硫剤を添加し、例えばインペラーで攪拌して脱硫処理し、この炉外脱硫処理後の高炭素溶鉄を精錬専用転炉へ供給することも開示されている。また、同公報には含鉄冷材、炭材としてスクラップ、石炭を用い、炭素含有量３．５％の高炭素溶鉄を得る実施例も開示されている。
【０００４】
上記転炉製鋼法においては、特許番号第２５６５７３１号の特許公報に記載されるように、精錬専用転炉での熱源を確保するためには理論的には炭素含有量３．０％以上、実際上は３．７％以上、好ましくは４．０％以上の高炭素溶鉄を溶解専用転炉で得る必要がある。
【０００５】
【発明が解決しようとする課題】
上記連続残湯残滓方式の含鉄冷材の溶解方法において、含鉄冷材、炭材等の原燃料として安価な原燃料を用いれば、高炭素溶鉄の製造コストを低減することができる。石炭よりも安価な炭材として廃タイヤがある。これは石炭に比べて硫黄含有量が高い。また、スクラップよりも安価な含鉄冷材として脱硫スラグ内から破砕と磁力選別で回収された鉄屑（以下、回収屑という）がある。これはスクラップに比べて硫黄含有量が高い。
【０００６】
本発明者等は、低コストで高炭素溶鉄を製造する（含鉄冷材を溶解する）ために、石炭の一部を硫黄含有量が高い安価炭材の廃タイヤに炭材Ｃインプット原単位が等価となるように置換した原燃料組成を変更して上記連続残湯残滓方式の含鉄冷材の溶解方法を実施した。
【０００７】
さらに、石炭の一部を上記安価炭材に置換することに加えてスクラップの一部を硫黄含有量が高い安価含鉄冷材の回収屑に置換した原燃料組成に変更して上記連続残湯残滓方式の含鉄冷材の溶解方法を実施した。その結果、
（１）連続残湯残滓方式の含鉄冷材の溶解方法においては、原燃料組成を変更後、溶解操業にして３〜５サイクルまで（過渡期）には溶鉄成分ならびに溶滓成分の変化が見られ、溶解操業にして３〜５サイクル目には、溶鉄成分ならびに溶滓成分が安定する定常状態となる。以降の説明での高炭素溶鉄組成は、上記定常状態における高炭素溶鉄組成を示す。
（２）石炭の上記（硫黄含有量が高い安価炭材の）廃タイヤへの置換比率を高くした原燃料組成、加えてスクラップの上記（硫黄含有率の高い安価含鉄冷材の）回収屑への置換率を高くした原燃料組成では、原燃料のＳインプット原単位が高くなり、原燃料のＳインプット原単位が高くなるに従がって製造された高炭素溶鉄の硫黄濃度が高くなる。また、製造された高炭素溶鉄の一部を炉内に残湯したものである種湯の硫黄濃度も高くなる。そして、
（３）原燃料のＳインプット原単位が０．９kg/t以上で、且つ種湯の硫黄濃度が０．０８０％を超えると、製造された高炭素溶鉄の炭素濃度が３．７％未満となり、精錬専用転炉での熱源不足となる新たな課題を見出した。また、
（４）種溶滓量が一定の条件で種湯の硫黄濃度が高くなるほど、溶解専用転炉（溶解炉）からの鉄ダスト発生量（含鉄冷材溶解過程の平均鉄ダスト発生速度）が増加して鉄歩留まりが低下する、という新たな課題も見出した。
【０００８】
本発明は、高炭素溶鉄の製造コストを低減するために硫黄含有量の高い安価原燃料を使用して原燃料のＳインプット原単位が０．９kg/t以上となっても、鉄歩留まりの低下なく、炭素濃度３．７％以上の高炭素溶鉄を得ることができる連続残湯残滓方式の含鉄冷材の溶解方法を提供するものである。
【０００９】
【課題を解決するための手段】
本発明は、連続残湯残滓方式の含鉄冷材の溶解方法において、含鉄冷材、炭材等の原燃料のＳインプット原単位が０．９kg/t以上であっても、種湯の硫黄濃度が０．０８０％以下であれば、製造された高炭素溶鉄の炭素濃度が３．７％以上となると共に、高炭素溶鉄の製造過程の鉄ダスト発生量が低下して（平均鉄ダスト発生速度が低下して）鉄歩留まりも向上するという新たな知見に基ずきなされたものである。
【００１０】
すなわち、本発明の要旨は、次の通りである。
（１）種湯、種溶滓の存在する溶解専用転炉に含鉄冷材、副材、炭材、酸素を供給して含鉄冷材を加炭（浸炭）溶解し高炭素溶鉄と溶滓を得、倒炉による出湯時に上記高炭素溶鉄の一部を炉内に残し、次回の含鉄冷材加炭溶解操業の種湯として使用すると共に、出湯に引き続く反出湯側への倒炉による排滓時に上記溶滓の一部を炉内に残し、次回の含鉄冷材加炭溶解操業の種溶滓、鉄ダスト飛散抑制溶滓として使用する連続残湯残滓方式の含鉄冷材の溶解方法において、原燃料として、原燃料のＳインプット原単位が０．９kg/t以上になる硫黄含有量の高い安価原燃料を使用すると共に、出湯前、或いは出湯後に上記含鉄冷材を加炭（浸炭）溶解して得た高炭素溶鉄全体、或いは残湯した上記高炭素溶鉄の一部を、アルミニウム濃度が２５〜５０％で、残部の主成分がアルミナであるアルミニウム精錬副産物（アルミ灰）からなる溶滓還元剤の供給と高炭素溶鉄の攪拌にて炉内脱硫処理して、種湯の硫黄濃度を０．０８０％以下に低下することで、硫黄含有量の高い安価原燃料使用に伴う高炭素溶鉄の炭素濃度の低下を防止し、高炭素溶鉄の炭素濃度を３．７％以上にすることを特徴とする含鉄冷材の溶解方法。
（２）溶滓還元剤の供給を、ブリケット状の溶滓還元剤の炉上からの投入にて行うことを特徴とする（１）に記載の含鉄冷材の溶解方法。
（３）溶滓還元剤の供給を、粉状の溶滓還元剤の高炭素溶鉄中への吹き込みにて行うことを特徴とする（１）に記載の含鉄冷材の溶解方法。
【００１１】
【発明の実施の形態】
本発明者等は、低コストで高炭素溶鉄を製造するために、石炭の一部を硫黄含有量が高い安価炭材の廃タイヤに炭材Ｃインプット原単位が等価となるように置換して上記連続残湯残滓方式の含鉄冷材の溶解方法を実施した。さらに、石炭の一部を上記安価炭材に置換することに加えてスクラップの一部を硫黄含有量が高い安価含鉄冷材の回収屑に置換して上記連続残湯残滓方式の含鉄冷材の溶解方法を実施した。
【００１２】
その際の原燃料Ｓインプット原単位と種湯Ｓ濃度と製造溶鉄Ｃ濃度の関係を図１に示す。
また、原燃料Ｓインプット原単位（種湯Ｓ濃度）と種溶滓一定量存在下の含鉄冷材溶解過程の平均鉄ダスト発生速度の関係を図２に示す。
【００１３】
図１から明らかなように、▲１▼原燃料Ｓインプット原単位０．９kg/t未満で、種湯Ｓ濃度は０．０８０％以下となり、製造溶鉄Ｃ濃度が３．７％以上となるが、▲２▼原燃料Ｓインプット原単位０．９kg/t以上では、種湯Ｓ濃度は０．０８０％超となり、製造溶鉄Ｃ濃度が３．７％未満となる。後者の場合、精錬専用転炉での熱源不足となる。
【００１４】
また、図２から明らかなように、▲１▼原燃料Ｓインプット原単位０．９kg/t未満で、種湯Ｓ濃度は０．０８０％以下となり製造溶鉄Ｃ濃度が３．７％以上となる操業に比べて、▲２▼原燃料Ｓインプット原単位０．９kg/t以上で、種湯Ｓ濃度は０．０８０％超となり製造溶鉄Ｃ濃度が３．７％未満となる操業は、含鉄冷材溶解過程の平均鉄ダスト発生速度が大きく、鉄歩留りが低下する。
【００１５】
本発明者等は、材料とプロセス（第６巻、（１９９３）１０２８頁）等で周知の溶鉄中Ｓ濃度が浸炭速度に及ぼす影響（溶鉄中Ｓ濃度が高いほど、炭材中Ｃの溶鉄中への加炭（浸炭）速度が低下する）に着目し、含鉄冷材を加炭（浸炭）溶解して得た高炭素溶鉄に炉内脱硫を施して種湯Ｓ濃度０．０８％以下にし、原燃料Ｓインプット原単位０．９ｋｇ／ｔ以上で操業することを着想し、実施した。
【００１６】
その際の原燃料Ｓインプット原単位と種湯Ｓ濃度と製造溶鉄Ｃ濃度の関係を図３に示す。
また、原燃料Ｓインプット原単位（種湯Ｓ濃度）と種溶滓一定量存在下の含鉄冷材溶解過程の平均鉄ダスト発生速度の関係を図４に示す。
【００１７】
なお図３には、炉内脱硫を施さないときの原燃料Ｓインプット原単位と種湯Ｓ濃度と製造溶鉄Ｃ濃度の関係を併記し、図４には炉内脱硫を施さないときの原燃料Ｓインプット原単位（種湯Ｓ濃度）と種溶滓一定量存在下の含鉄冷材溶解過程の平均鉄ダスト発生速度の関係を併記した。
【００１８】
図３から明らかなように、原燃料Ｓインプット原単位０．９kg/t以上であっても種湯Ｓ濃度を０．０８０％以下とすれば、製造された高炭素溶鉄の炭素濃度が３．７％以上とできる。このため精錬専用転炉での熱源不足となることはない。この高炭素溶鉄の炭素濃度の変化の機構は、Ｓ濃度が高い場合にはＳの界面吸着作用によって浸炭速度が低下し、Ｓ濃度が低い場合にはその作用が小さいために浸炭速度が低下しなかったものと考えられる。
【００１９】
また、図４から明らかなように、原燃料Ｓインプット原単位０．９kg/t以上であっても脱硫処理して、種湯Ｓ濃度を０．０８０％以下とすれば、含鉄冷材溶解過程の平均鉄ダスト発生速度も低下する。このため鉄歩留りは向上する。
【００２０】
このダスト発生の変化の機構は、次のように考えられる。溶鉄中のＳ濃度が低下すると界面張力が増加する。界面形成エネルギーと飛散粒鉄の運動エネルギーとの相互関係から求められる溶鉄から粒鉄が飛散し始める際の限界のガス側流速、いわゆる上吹き噴流強度、は、より大きな流速条件でないと飛散が始まらず、かつ飛散する粒鉄の粒径が粗くなる。このために、炉内発生ガスに随伴して煙道に吸引される粒鉄量が減少すると考えられる。
【００２１】
上記種湯Ｓ濃度を０．０８０％以下にするために、炉内脱硫処理するが、その処理対象は、溶解専用転炉（溶解炉）に、含鉄冷材を加炭（浸炭）溶解して得た高炭素溶鉄全体であっても、出湯時に上記高炭素溶鉄の一部を炉内に残湯させた高炭素溶鉄、即ち種湯であってもよい。
【００２２】
前者の場合、後者に比べて溶解専用転炉（溶解炉）の炉内脱硫負荷が大きく、炉内脱硫処理時間が長くなり、溶解専用転炉（溶解炉）の高炭素溶鉄の生産性が小さくなるが、残湯される高炭素溶鉄（種湯）は勿論、出湯される高炭素溶鉄（製造溶鉄）ともにＳ濃度０．０８０％以下に低減されるので、次工程の炉外脱硫負荷が低減される。
【００２３】
後者の場合、前者に比べて次工程の炉外脱硫負荷が大きいが、溶解専用転炉（溶解炉）の炉内脱硫負荷が小さく、炉内脱硫処理時間が短くなり、溶解専用転炉（溶解炉）の高炭素溶鉄の生産性が大きくなる。一方、溶解専用転炉（溶解炉）設備と炉外脱硫設備とは、別設備であり、これらの設備の操業は平行して行うことができる。
したがって、炉内脱硫処理対象は、必要とされる高炭素溶鉄の生産性に応じて選択すればよい。
【００２４】
一般に、脱硫精錬は溶滓中の酸化鉄濃度を低下せしめることが有効である。溶滓中の酸化鉄濃度を低減するには、いわゆる溶滓還元剤を供給することで達成できる。また、溶滓還元剤を供給して上記高炭素溶鉄を攪拌することで脱硫処理を促進することができる。
【００２５】
さらに、溶滓還元剤の供給方法としては、ブリケット状の溶滓還元剤を炉上から投入する方法、あるいは、粉状の溶滓還元剤を高炭素溶鉄中へ吹き込む方法、これらを併用する方法が採用できる。溶滓還元剤原単位の面からは、粉状の溶滓還元剤を高炭素溶鉄中へ吹き込む方法を採用するのが好ましい。
【００２６】
次に、溶滓還元剤としては、価格が安価な、アルミニウム濃度が２５〜５０％で、残部の主成分がアルミナであるアルミニウム精錬副産物（アルミ灰）を使用することが、製造コスト削減の観点からは望ましい。
【００２７】
脱硫処理を促進するための高炭素溶鉄の攪拌方法としては、周知の底吹きガスによる攪拌が採用できる。
硫黄含有量の高い安価炭材として、廃タイヤの他に廃プラスチック、廃ゴム等がある。
【００２８】
【実施例】
（実施例１）
種湯、種溶滓の存在する２００ton 規模の溶解専用転炉に含鉄冷材、副材、炭材、酸素を供給して含鉄冷材を加炭（浸炭）溶解し高炭素溶鉄と溶滓を得、倒炉による出湯時に上記高炭素溶鉄の一部を炉内に残し、次回の含鉄冷材加炭溶解操業の種湯として使用すると共に、出湯に引き続く反出湯側への倒炉による排滓時に上記溶滓の一部を炉内に残し、次回の含鉄冷材加炭溶解操業の種溶滓、鉄ダスト飛散抑制溶滓として使用する連続残湯残滓方式の含鉄冷材の溶解方法において、原燃料の含鉄冷材として、スクラップ（Ｓ含有率０．０２４％）５８ton 使用し、また、原燃料の炭材として、微粉炭（Ｃ含有率８０％、Ｓ含有率０．２％、灰分含有率１５％）９６２５kgおよび廃タイヤ（Ｃ含有率７８％、Ｓ含有率１．１％、灰分含有率１％）２０３５kg使用すると共に、出湯前に溶滓還元剤のアルミ灰（アルミニウム濃度が約４０％で残部の主成分がアルミナ）ブリケットを５００kg炉上方から添加すると共に、Ｎ₂ガスを底吹きして溶鉄を攪拌エネルギー４５０KJ/tで攪拌して上記含鉄冷材を加炭（浸炭）溶解して得た高炭素溶鉄全体を炉内脱硫処理した。
【００２９】
なお、上記操業における種湯（残湯）、種溶滓（残溶滓）、出湯量は、各々８４ton 、１０ton 、５５ton とした。また、副剤として石灰（ＣａＯ）１０７０kg、マグネシア（ＭｇＯ）３９０kg、アルミ灰ブリケット１６０kgを含鉄冷材の溶解完了時の溶滓組成調整のために供給した。酸素を９３５０Nm³供給した。この定常状態の操業結果を表１に示す。
【００３０】
【表１】

【００３１】
【表２】

【００３２】
（比較例１）
比較のために、実施例１において、炉内脱硫実施せずに、出湯前溶滓組成を実施例１と同一組成の塩基度（ＣａＯ／ＳｉＯ₂）１．６、Ａｌ₂Ｏ₃濃度２４％、ＭｇＯ濃度１０％とするために、副剤として供給するアルミ灰ブリケットを６６０kgに増量した操業を実施した。この定常状態での操業結果を表１に併記した。
【００３３】
（実施例２）
実施例１において、微粉炭（Ｃ含有率８０％、Ｓ含有率０．２％、灰分含有率１５％）８４１５kgおよび廃タイヤ（Ｃ含有率７８％、Ｓ含有率１．１％、灰分含有率１％）３２４５kgに変更し、石灰量９４０kgに変更した操業を実施した。これらの定常状態での操業結果を表１に併記した。
【００３４】
（比較例２）
比較のために、実施例２において、炉内脱硫実施せずに、出湯前溶滓組成を実施例２と同一組成の塩基度（ＣａＯ／ＳｉＯ₂）１．６、Ａｌ₂Ｏ₃濃度２４％、ＭｇＯ濃度１０％とするために、副剤として供給するアルミ灰ブリケットを５９０kgに増量した操業を実施した。この定常状態での操業結果を表１に併記した。
【００３５】
（実施例３）
実施例１において、微粉炭（Ｃ含有率８０％、Ｓ含有率０．２％、灰分含有率１５％）６６００kgおよび廃タイヤ（Ｃ含有率７８％、Ｓ含有率１．１％、灰分含有率１％）５０６０kgに変更し、石灰量７４０kgに変更した操業を実施した。この定常状態での操業結果を表１に併記した。
【００３６】
（比較例３）
比較のために、実施例３において、炉内脱硫実施せずに、出湯前溶滓組成を実施例３と同一組成の塩基度（ＣａＯ／ＳｉＯ₂）１．６、Ａｌ₂Ｏ₃濃度２４％、ＭｇＯ濃度１０％とするために、副剤として供給するアルミ灰ブリケットを５１０kgに増量した操業を実施した。この定常状態での操業結果を表１に併記した。
【００３７】
（比較例４）
また、実施例３において、炭材として廃タイヤを使用せずに微粉炭のみを１１６６０kg使用し、炉内脱硫実施せずに、出湯前溶滓組成を実施例３と同一の組成とするために、副剤として供給するアルミ灰ブリケットを７９０kgに増量した操業を実施した。この定常状態での操業結果を表１に併記した。
【００３８】
（実施例４、５、６）
実施例１、２、３において、炉内脱硫処理における溶滓還元剤の銘柄、投入量、投入法を「アルミ灰（アルミニウム濃度が約４０％で残部の主成分がアルミナ）粉、４００kg、炉底の底吹きノズルから吹き込み」に変更した。その操業結果を表１に併記した。
【００３９】
（実施例７）
種湯、種溶滓の存在する２００ton 規模の溶解専用転炉に含鉄冷材、副材、炭材、酸素を供給して含鉄冷材を加炭（浸炭）溶解し高炭素溶鉄と溶滓を得、倒炉による出湯時に上記高炭素溶鉄の一部を炉内に残し、次回の含鉄冷材加炭溶解操業の種湯として使用すると共に、出湯に引き続く反出湯側への倒炉による排滓時に上記溶滓の一部を炉内に残し、次回の含鉄冷材加炭溶解操業の種溶滓、鉄ダスト飛散抑制溶滓として使用する連続残湯残滓方式の含鉄冷材の溶解方法において、原燃料の含鉄冷材として、スクラップ（Ｓ含有率０．０２４％）５２ton および回収屑（Ｓ含有率１．０％）６ton 使用し、また、原燃料の燃料の炭材として、微粉炭（Ｃ含有率８０％、Ｓ含有率０．２％、灰分含有率１５％）６８７５kgおよび廃タイヤ（Ｃ含有率７８％、Ｓ含有率１．１％、灰分含有率１％）５２８０kg使用すると共に、出湯前に溶滓還元剤のアルミ灰（アルミニウム濃度が約４０％で残部の主成分がアルミナ）粉４００kgを炉底の底吹きノズルから吹き込むと共に、Ｎ₂ガスを炉底の底吹きノズルから吹き込み溶鉄を攪拌エネルギー４５０KJ/tで攪拌して上記含鉄冷材を加炭（浸炭）溶解して得た高炭素溶鉄全体を炉内脱硫処理した。
【００４０】
なお、上記操業における種湯（残湯）、種溶滓（残溶滓）、出湯量は、各々８４ton 、１０ton 、５５ton とした。また副剤として石灰（ＣａＯ）７７０kg、マグネシア（ＭｇＯ）３００kg、アルミ灰ブリケット１００kgを含鉄冷材の溶解完了時の溶滓組成調整のために供給した。酸素を９３５０Ｎｍ³供給した。この定常状態の操業結果を表１に示す。
【００４１】
表１より、高炭素溶鉄の製造コストを低減するために硫黄含有量の高い安価原燃料を使用して原燃料のＳインプット原単位が０．９kg/t以上となっても、鉄歩留まりの低下なく、炭素濃度３．７％以上の高炭素溶鉄を得ることができることが明らかである。
なお、灰分を多量に含有する石炭に置換して、廃タイヤを使用すると、廃タイヤは灰分を少量しか含有していないために、副材（ＣａＯ）が減少し、排滓量も減少することも明らかである。
【００４２】
また、溶鉄の脱硫処理を、溶滓還元剤の供給と高炭素溶鉄の攪拌にて行うに祭し、溶滓還元剤の供給を、粉状の溶滓還元剤の高炭素溶鉄中への吹き込みにて行うことで、溶滓還元剤使用量を削減できることも明らかである。
【００４３】
【発明の効果】
以上の本発明の連続残湯残滓方式の含鉄冷材の溶解方法によれば、高炭素溶鉄の製造コストを低減するために硫黄含有量の高い安価原燃料を使用して原燃料のＳインプット原単位が０．９kg/t以上となっても、鉄歩留まりの低下なく、炭素濃度３．７％以上の高炭素溶鉄を得ることができる。
【図面の簡単な説明】
【図１】原燃料組成を種々変更した際の原燃料Ｓインプット原単位と種湯Ｓ濃度と製造溶鉄Ｃ濃度の関係図。
【図２】原燃料組成を種々変更した際の原燃料Ｓインプット原単位（原燃料種湯Ｓ濃度）と含鉄冷材溶解過程の平均ダスト発生速度の関係図。
【図３】含鉄冷材を加炭（浸炭）溶解して得た高炭素溶鉄に炉内脱硫を施して種湯Ｓ濃度０．０８％以下にし、原燃料Ｓインプット原単位０．９kg/t以上で操業した際の原燃料Ｓインプット原単位と種湯Ｓ濃度と製造溶鉄Ｃ濃度の関係図。
【図４】含鉄冷材を加炭（浸炭）溶解して得た高炭素溶鉄に炉内脱硫を施して種湯Ｓ濃度０．０８％以下にし、原燃料Ｓインプット原単位０．９kg/t以上で操業した際の原燃料Ｓインプット原単位と含鉄冷材溶解過程の平均ダスト発生速度の関係図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a method for melting iron-containing cold material of a continuous residual hot water residue system, and in particular, high carbon produced by melting an iron-containing cold material using an inexpensive raw fuel as a raw fuel such as iron-containing cold material and carbonaceous material. The present invention relates to a method for melting iron-containing cold material using a continuous residual hot water residue system that reduces the manufacturing cost of molten iron.
[0002]
[Prior art]
Iron-containing cold material, secondary material, carbonaceous material, oxygen is supplied to a melting-only converter (melting furnace) containing seed hot water and seed hot metal, and the iron-containing cold material is carburized and melted to obtain high carbon molten iron and hot metal, A part of the high-carbon molten iron is left in the furnace at the time of tapping in the inversion furnace, and is used as seed water for the next iron-containing cold material carburizing and melting operation. A part of the hot metal is left in the furnace, seed hot metal for the next iron-containing cold material carburizing and melting operation, a method for melting the iron-containing cold material of the continuous residual hot metal residue method used as iron dust scattering suppression hot metal, A converter steelmaking method for obtaining molten steel of a required component by oxygen-smelting high-carbon molten iron discharged from a furnace (melting furnace) in another refining converter (decarburization furnace) is disclosed in Japanese Patent Publication No. 4-78686. It is known.
[0003]
In the above-mentioned converter steelmaking method, when the sulfur content of coke, coal, etc. used in melting converters is high, and the sulfur content of high-carbon molten iron discharged to the ladle is high In addition, it is also disclosed that a desulfurizing agent is added to the high carbon molten iron in the ladle, and the desulfurization treatment is performed by, for example, stirring with an impeller, and the high carbon molten iron after the out-of-furnace desulfurization treatment is supplied to a refining converter. The publication also discloses an example in which high carbon molten iron having a carbon content of 3.5% is obtained by using iron-containing cold material, scrap as coal, and coal.
[0004]
In the converter steelmaking method, as described in the patent publication No. 2565731, in order to secure a heat source in a refining converter, theoretically, the carbon content is 3.0% or more. Above, it is necessary to obtain high-carbon molten iron of 3.7% or more, preferably 4.0% or more in a melting-only converter.
[0005]
[Problems to be solved by the invention]
In the melting method of the iron-containing cold material of the above-mentioned continuous remaining hot water residue system, if an inexpensive raw fuel is used as the raw fuel for the iron-containing cold material, the carbonaceous material, etc., the manufacturing cost of the high carbon molten iron can be reduced. There is a waste tire as a cheaper carbon material than coal. This has a higher sulfur content than coal. Moreover, there is iron scrap (hereinafter referred to as recovered scrap) recovered from the desulfurized slag by crushing and magnetic separation as an iron-containing cold material that is cheaper than scrap. This has a higher sulfur content than scrap.
[0006]
In order to produce high carbon molten iron (dissolve iron-containing cold material) at a low cost, the present inventors have reduced the amount of coal C input basic unit to waste tires of low-cost carbon materials with high sulfur content. The raw fuel composition replaced so as to be equivalent was changed, and the method for melting iron-containing cold material of the above-mentioned continuous remaining hot water residue system was carried out.
[0007]
Furthermore, in addition to replacing a part of the coal with the above-mentioned low-cost carbon material, the above-mentioned continuous residual hot water residue is changed to a raw fuel composition in which a part of the scrap is replaced with recovered scrap of a low-cost iron-containing cold material having a high sulfur content. The method of melting iron-containing cold material of the system was carried out. as a result,
(1) In the method of melting iron-containing cold material of the continuous residual hot water residue method, after changing the raw fuel composition, the molten iron component and the molten iron component change after 3 to 5 cycles (transition period) after the melting operation. In the third to fifth cycles after the melting operation, the molten iron component and the molten iron component are in a steady state. The high carbon molten iron composition in the following description indicates the high carbon molten iron composition in the steady state.
(2) Raw fuel composition in which the replacement ratio of the above-mentioned coal (of low-cost coal with high sulfur content) to waste tires is increased, and in addition to the above-mentioned recovered scrap (of low-cost iron-containing cold material with high sulfur content) In the raw fuel composition in which the replacement ratio is increased, the S input basic unit of the raw fuel is increased, and the sulfur concentration of the high carbon molten iron produced as the S input basic unit of the raw fuel is increased is increased. In addition, the sulfur concentration of the seed hot water, which is a part of the manufactured high carbon molten iron remaining in the furnace, also increases. And
(3) If the S input basic unit of raw fuel is 0.9kg / t or more and the sulfur concentration of the seed hot water exceeds 0.080%, the carbon concentration of the manufactured high carbon molten iron will be less than 3.7%. , I found a new problem that the heat source in the refining converter is insufficient. Also,
(4) The amount of iron dust generated from the melting-only converter (melting furnace) (the average iron dust generation rate in the iron-containing cold material melting process) increases as the sulfur concentration of the seed hot water increases under the condition that the amount of seed hot metal is constant. As a result, they found a new problem that the iron yield would decrease.
[0008]
The present invention uses a low-cost raw fuel with a high sulfur content in order to reduce the manufacturing cost of high carbon molten iron, and even if the S input basic unit of the raw fuel becomes 0.9 kg / t or more, the iron yield decreases. The present invention provides a melting method of iron-containing cold material of a continuous residual hot water residue system that can obtain high carbon molten iron having a carbon concentration of 3.7% or more.
[0009]
[Means for Solving the Problems]
The present invention relates to a method for melting iron-containing cold material of a continuous residual hot water residue method, even if the S input basic unit of raw fuel such as iron-containing cold material and carbonaceous material is 0.9 kg / t or more, the sulfur concentration of the seed hot water Is 0.080% or less, the carbon concentration of the manufactured high carbon molten iron becomes 3.7% or more, and the amount of iron dust generated in the manufacturing process of the high carbon molten iron decreases (average iron dust generation rate). This is based on the new knowledge that the iron yield is improved.
[0010]
That is, the gist of the present invention is as follows.
(1) Supply iron-containing cold material, secondary material, charcoal, and oxygen to the converter dedicated to melting in which seed hot water and seed hot metal exist. In addition, a part of the high-carbon molten iron is left in the furnace at the time of tapping in the inversion furnace and used as seed water for the next iron-containing cold material carburizing and melting operation. In the melting method of the iron-containing cold material of the continuous residual hot metal residue system used as the seed hot metal for the next iron-containing cold material carburizing and melting operation, the iron dust scattering suppression hot metal, sometimes leaving a part of the hot metal in the furnace, As raw fuel, an inexpensive raw fuel with a high sulfur content that makes the S input basic unit of the raw fuel 0.9 kg / t or more is used, and the iron-containing cold material is carburized (carburized) before or after tapping. The entire high-carbon molten iron obtained or a part of the remaining high-carbon molten iron was used , and the aluminum concentration was 25-5. At 0%, the desulfurization treatment in the furnace is performed by supplying a hot metal reducing agent composed of an aluminum refining by-product (aluminum ash) whose main component is alumina, and stirring of high carbon molten iron, and the sulfur concentration of the seed hot water is reduced to 0. By reducing to 080% or less, it is possible to prevent the carbon concentration of high-carbon molten iron from using low-cost raw fuel with a high sulfur content, and to make the carbon concentration of high-carbon molten iron 3.7% or more. A method for melting iron-containing cold material.
(2) The method for melting iron-containing cold material as set forth in (1), wherein the hot metal reducing agent is supplied by feeding a briquette-shaped hot metal reducing agent from the furnace.
(3) The method for melting the iron-containing cold material according to (1), wherein the hot metal reducing agent is supplied by blowing a powdered hot metal reducing agent into the high carbon molten iron.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In order to produce high-carbon molten iron at low cost, the present inventors replaced a part of coal with waste tires of low-cost carbon material having a high sulfur content so that the carbon material C input basic unit becomes equivalent. The above-mentioned continuous residual hot water residue type iron-containing cold material melting method was carried out. Furthermore, in addition to replacing a part of the coal with the above-mentioned low-cost carbon material, a part of the scrap is replaced with a recovery scrap of a low-cost iron-containing cold material having a high sulfur content, so that A dissolution method was performed.
[0012]
The relationship between the raw fuel S input basic unit, the seed hot water S concentration, and the manufactured molten iron C concentration is shown in FIG.
FIG. 2 shows the relationship between the raw fuel S input basic unit (seed hot water S concentration) and the average iron dust generation rate in the iron-containing cold material melting process in the presence of a constant amount of seed hot metal.
[0013]
As is clear from FIG. 1, (1) the raw fuel S input basic unit is less than 0.9 kg / t, the seed hot water S concentration is 0.080% or less, and the manufactured molten iron C concentration is 3.7% or more. (2) When the raw fuel S input basic unit is 0.9 kg / t or more, the seed hot water S concentration exceeds 0.080%, and the produced molten iron C concentration is less than 3.7%. In the latter case, the heat source in the refining converter is insufficient.
[0014]
As is clear from FIG. 2, (1) the raw fuel S input basic unit is less than 0.9 kg / t, the seed S concentration is 0.080% or less, and the produced molten iron C concentration is 3.7% or more. Compared with the operation, (2) the raw fuel S input basic unit is 0.9kg / t or more, the operation of the seed hot water S concentration is over 0.080% and the production molten iron C concentration is less than 3.7%. The average iron dust generation rate in the material melting process is large, and the iron yield decreases.
[0015]
The inventors of the present invention have the effect that the S concentration in molten iron, which is well-known in materials and processes (Vol. 6, (1993) 1028), etc., affects the carburization rate (the higher the S concentration in molten iron, The carburizing (carburizing) speed of the steel will be reduced), and high-carbon molten iron obtained by carburizing (carburizing) iron-containing cold material will be desulfurized in the furnace to make the seed S concentration 0.08% or less. The concept was carried out with the idea of operating at a raw fuel S input basic unit of 0.9 kg / t or more.
[0016]
FIG. 3 shows the relationship between the raw fuel S input basic unit, seed hot water S concentration, and manufactured molten iron C concentration at that time.
FIG. 4 shows the relationship between the raw fuel S input basic unit (seed hot water S concentration) and the average iron dust generation rate in the iron-containing cold material melting process in the presence of a constant amount of seed hot metal.
[0017]
FIG. 3 shows the relationship between the raw fuel S input basic unit, the seed hot water S concentration, and the manufactured molten iron C concentration when no desulfurization is performed in the furnace, and FIG. 4 shows the raw fuel when no desulfurization is performed in the furnace. The relationship between the S input basic unit (seed hot water S concentration) and the average iron dust generation rate in the iron-containing cold material melting process in the presence of a certain amount of seed hot metal is also shown.
[0018]
As is clear from FIG. 3, even if the raw fuel S input basic unit is 0.9 kg / t or more, if the seed hot water S concentration is 0.080% or less, the carbon concentration of the produced high carbon molten iron is 3. 7% or more. For this reason, there is no shortage of heat source in the refining converter. The mechanism of change in the carbon concentration of this high carbon molten iron is that when the S concentration is high, the carburization rate decreases due to the interfacial adsorption action of S, and when the S concentration is low, the effect is small and the carburization rate decreases. It is thought that there was not.
[0019]
As is clear from FIG. 4, even if the raw fuel S input basic unit is 0.9 kg / t or more, if desulfurization treatment is performed and the seed hot water concentration is 0.080% or less, the iron-containing cold material melting process The average iron dust generation rate is also reduced. For this reason, the iron yield is improved.
[0020]
The mechanism of the change in dust generation is considered as follows. When the S concentration in the molten iron decreases, the interfacial tension increases. The critical gas side flow velocity at which particle iron begins to scatter from the molten iron, the so-called upper jet strength, obtained from the correlation between the interface formation energy and the kinetic energy of the scattered particle iron, will not start to scatter unless the flow velocity conditions are larger. And the particle size of the scattered iron becomes coarse. For this reason, it is considered that the amount of granular iron sucked into the flue accompanying the gas generated in the furnace decreases.
[0021]
In order to make the above-mentioned seed hot water S concentration 0.080% or less, in-furnace desulfurization treatment is performed, and the treatment object is to carburize (carburize) the iron-containing cold material in a melting-only converter (melting furnace). Even the entire high carbon molten iron obtained may be high carbon molten iron in which a part of the high carbon molten iron is left in the furnace at the time of pouring, that is, seed hot water.
[0022]
In the former case, the furnace desulfurization load of the melting-only converter (melting furnace) is larger and the furnace desulfurization treatment time is longer than the latter, and the productivity of high-carbon molten iron in the melting-only converter (melting furnace) is small. However, not only the high-temperature molten iron (seed bath) that is left but also the high-carbon molten iron (manufactured molten iron) that is discharged is reduced to 0.080% or less of the S concentration. Is done.
[0023]
In the latter case, the out-of-furnace desulfurization load of the next process is larger than the former, but the in-furnace desulfurization load of the melting-dedicated converter (melting furnace) is small, the in-furnace desulfurization treatment time is shortened, and the melting-dedicated converter (melting) The productivity of high carbon molten iron in the furnace is increased. On the other hand, a melting-only converter (melting furnace) facility and an out-of-furnace desulfurization facility are separate facilities, and operations of these facilities can be performed in parallel.
Therefore, what is necessary is just to select the object for desulfurization processing in a furnace according to the productivity of the required high carbon molten iron.
[0024]
In general, desulfurization refining is effective in reducing the iron oxide concentration in the hot metal. Reducing the iron oxide concentration in the hot metal can be achieved by supplying a so-called hot metal reducing agent. Moreover, a desulfurization process can be accelerated | stimulated by supplying a hot metal reducing agent and stirring the said high carbon molten iron.
[0025]
Furthermore, as a hot metal reducing agent supply method, a briquette hot metal reducing agent is introduced from the furnace, or a powder hot metal reducing agent is blown into high-carbon molten iron, or a combination thereof. Can be adopted. From the aspect of the hot metal reducing agent basic unit, it is preferable to employ a method in which a powdered hot metal reducing agent is blown into high-carbon molten iron.
[0026]
Next, as a hot metal reducing agent, it is possible to use an aluminum refining byproduct (aluminum ash), which is inexpensive and has an aluminum concentration of 25 to 50% and the remaining main component is alumina. Is desirable.
[0027]
As a method of stirring the high carbon molten iron for promoting the desulfurization treatment, a well-known bottom blowing gas can be used.
In addition to waste tires, there are waste plastics, waste rubber, and the like as inexpensive carbon materials having a high sulfur content.
[0028]
【Example】
Example 1
Iron-containing cold material, secondary material, carbonaceous material, and oxygen are supplied to a 200 ton scale melting converter with seed hot water and seed hot metal, and the iron-containing cold material is carburized (carburized) to melt high carbon molten iron and hot metal. In addition, a part of the high-carbon molten iron is left in the furnace at the time of tapping in the inversion furnace and used as seed water for the next iron-containing cold material carburizing and melting operation. In the melting method of the iron-containing cold material of the continuous residual hot metal residue system used as the seed hot metal for the next iron-containing cold material carburizing and melting operation, the iron dust scattering suppression hot metal, sometimes leaving a part of the hot metal in the furnace, Scrap (S content 0.024%) 58ton is used as iron-containing cold material of raw fuel, and pulverized coal (C content 80%, S content 0.2%, ash content) as raw fuel carbon material 1525) 9625 kg and waste tires (C content 78%, S content 1.1%, ash content 1%) 2 While 035kg used, with aluminum ash (the main component of the balance in the aluminum concentration of about 40% alumina) in溶滓reducing agent before pouring the addition of briquettes from 500kg furnace above the molten iron by bottom blowing N ₂ gas The entire high-carbon molten iron obtained by agitating at a stirring energy of 450 KJ / t and carburizing (carburizing) the iron-containing cold material was desulfurized in the furnace.
[0029]
In addition, the seed hot water (residual hot water), the seed hot metal (residual hot metal), and the amount of discharged hot water in the said operation were 84 tons, 10 tons, and 55 tons, respectively. Further, 1070 kg of lime (CaO), 390 kg of magnesia (MgO), and 160 kg of aluminum ash briquettes were supplied as auxiliary agents for adjusting the hot metal composition at the completion of melting of the iron-containing cold material. Oxygen was supplied at 9350 Nm ³ . The steady state operation results are shown in Table 1.
[0030]
[Table 1]

[0031]
[Table 2]

[0032]
(Comparative Example 1)
For comparison, in Example 1, the basic composition (CaO / SiO ₂ ) of 1.6 and the Al ₂ O ₃ concentration of 24% are the same as those in Example 1 without performing desulfurization in the furnace. In order to make the MgO concentration 10%, an operation was carried out in which the amount of aluminum ash briquettes supplied as an auxiliary agent was increased to 660 kg. The operation results in the steady state are also shown in Table 1.
[0033]
(Example 2)
In Example 1, pulverized coal (C content 80%, S content 0.2%, ash content 15%) 8415 kg and waste tire (C content 78%, S content 1.1%, ash content) 1%) The operation was changed to 3245 kg and the amount of lime was changed to 940 kg. The results of operation in these steady states are also shown in Table 1.
[0034]
(Comparative Example 2)
For comparison, in Example 2, the hot metal composition before tapping was the same composition as in Example 2 (CaO / SiO ₂ ) 1.6, Al ₂ O ₃ concentration 24% without performing desulfurization in the furnace. In order to make the MgO concentration 10%, an operation was carried out in which the amount of aluminum ash briquettes supplied as an auxiliary agent was increased to 590 kg. The operation results in the steady state are also shown in Table 1.
[0035]
Example 3
In Example 1, 6600 kg of pulverized coal (C content 80%, S content 0.2%, ash content 15%) and waste tire (C content 78%, S content 1.1%, ash content) 1%) The operation was changed to 5060 kg and the lime amount was changed to 740 kg. The operation results in the steady state are also shown in Table 1.
[0036]
(Comparative Example 3)
For comparison, in Example 3, the basic composition (CaO / SiO ₂ ) of 1.6 and Al ₂ O ₃ concentration of 24% was the same as in Example 3 without hot metal desulfurization. In order to obtain a MgO concentration of 10%, an operation was carried out in which the amount of aluminum ash briquettes supplied as an auxiliary agent was increased to 510 kg. The operation results in the steady state are also shown in Table 1.
[0037]
(Comparative Example 4)
Further, in Example 3, 11660 kg of only pulverized coal is used as a carbon material without using waste tires, and the hot metal composition before hot water is made the same as that of Example 3 without performing desulfurization in the furnace. The operation was carried out by increasing the amount of aluminum ash briquettes supplied as an auxiliary agent to 790 kg. The operation results in the steady state are also shown in Table 1.
[0038]
(Examples 4, 5, and 6)
In Examples 1, 2, and 3, the brand name, input amount, and input method of the hot metal reducing agent in the in-furnace desulfurization treatment were “aluminum ash (aluminum concentration was about 40% and the remaining main component was alumina) powder, 400 kg, furnace Changed to “Blow from the bottom blowing nozzle at the bottom”. The operation results are also shown in Table 1.
[0039]
(Example 7)
Iron-containing cold material, secondary material, carbonaceous material, and oxygen are supplied to a 200 ton scale melting converter with seed hot water and seed hot metal, and the iron-containing cold material is carburized (carburized) to melt high carbon molten iron and hot metal. In addition, a part of the high-carbon molten iron is left in the furnace at the time of tapping in the inversion furnace and used as seed water for the next iron-containing cold material carburizing and melting operation. In the melting method of the iron-containing cold material of the continuous residual hot metal residue system used as the seed hot metal for the next iron-containing cold material carburizing and melting operation, the iron dust scattering suppression hot metal, sometimes leaving a part of the hot metal in the furnace, Scrap (S content 0.024%) 52ton and recovered scrap (S content 1.0%) 6ton are used as iron-containing cold material for raw fuel, and pulverized coal (C Content rate 80%, S content rate 0.2%, ash content rate 15%) 6875kg and waste tire (C content rate) 8%, S content 1.1%, ash content 1%) 5280kg used, and 400kg of hot metal reducing agent aluminum ash (aluminum concentration is about 40% and the remaining main component is alumina) powder before tapping. High carbon obtained by blowing N ₂ gas from the bottom blowing nozzle at the bottom of the furnace and agitating molten iron at a stirring energy of 450 KJ / t to carburize (carburize) the iron-containing cold material. The entire molten iron was desulfurized in the furnace.
[0040]
In addition, the seed hot water (residual hot water), the seed hot metal (residual hot metal), and the amount of discharged hot water in the said operation were 84 tons, 10 tons, and 55 tons, respectively. Further, 770 kg of lime (CaO), 300 kg of magnesia (MgO), and 100 kg of aluminum ash briquette were supplied as auxiliary agents to adjust the hot metal composition at the completion of melting of the iron-containing cold material. Oxygen was supplied at 9350 Nm ³ . The steady state operation results are shown in Table 1.
[0041]
From Table 1, even if the raw material S input basic unit is 0.9 kg / t or more using low-cost raw fuel with a high sulfur content in order to reduce the manufacturing cost of high carbon molten iron, the iron yield will decrease. It is clear that high carbon molten iron having a carbon concentration of 3.7% or more can be obtained.
In addition, if the waste tire is replaced with coal containing a large amount of ash, the waste tire contains only a small amount of ash, so the secondary material (CaO) is reduced and the amount of waste is also reduced. Is also obvious.
[0042]
In addition, desulfurization of molten iron is performed by supplying hot metal reducing agent and stirring high-carbon molten iron, and supplying hot metal reducing agent into the molten high-carbon molten iron. It is also clear that the amount of hot metal reducing agent used can be reduced by performing the above.
[0043]
【The invention's effect】
According to the above-described method for melting iron-containing cold material of the continuous residual hot water residue method of the present invention, in order to reduce the manufacturing cost of high carbon molten iron, an inexpensive raw fuel having a high sulfur content is used and the S input raw material of the raw fuel is used. Even if the unit is 0.9 kg / t or more, high carbon molten iron having a carbon concentration of 3.7% or more can be obtained without lowering the iron yield.
[Brief description of the drawings]
FIG. 1 is a relationship diagram of raw fuel S input basic unit, seed hot water S concentration, and manufactured molten iron C concentration when various changes are made to the raw fuel composition.
FIG. 2 is a graph showing the relationship between the raw fuel S input basic unit (raw fuel seed water S concentration) and the average dust generation rate in the iron-containing cold material melting process when the raw fuel composition is variously changed.
[Fig. 3] High carbon molten iron obtained by carburizing (carburizing) iron-containing cold material is subjected to in-furnace desulfurization to make seed hot water concentration 0.08% or less, and raw fuel S input basic unit 0.9kg / t The relationship diagram of raw fuel S input basic unit, seed hot water S density | concentration, and manufactured molten iron C density | concentration at the time of operating above.
[Fig. 4] In-furnace desulfurization is performed on high-carbon molten iron obtained by carburizing (carburizing) iron-containing cold material to make seed S concentration 0.08% or less, and raw fuel S input basic unit 0.9kg / t The relationship diagram of the raw fuel S input basic unit at the time of the above operation, and the average dust generation | occurrence | production speed | rate of an iron-containing cold material melt | dissolution process.

Claims

Supply iron-containing cold material, secondary material, charcoal, and oxygen to a dedicated melting furnace with seed hot water and seed hot metal to carburize and dissolve the iron-containing cold material to obtain high carbon molten iron and hot metal. A part of the high-carbon molten iron is left in the furnace when it is discharged from the furnace, and is used as seed water for the next iron-containing cold material carburizing and melting operation. As a raw fuel in the method of melting the iron-containing cold material of the continuous residual hot water residue system that is used as the seed hot metal for the next iron-containing cold material carburizing and melting operation and the iron dust scattering suppression hot metal, leaving a part of the firewood in the furnace It is obtained by using low-cost raw fuel with a high sulfur content that makes the S input basic unit of the raw fuel 0.9 kg / t or more, and by carburizing (carburizing) the iron-containing cold material before or after tapping. The entire high-carbon molten iron, or a part of the remaining high-carbon molten iron, has an aluminum concentration of 25 to 50%. In addition, the sulfur concentration in the seed hot water is 0.080% or less by desulfurization treatment in the furnace by supplying hot metal reducing agent consisting of aluminum refining by-product (aluminum ash) whose main component is alumina and stirring high carbon molten iron To lower the carbon concentration of high-carbon molten iron due to the use of inexpensive raw fuel with a high sulfur content, and to make the carbon concentration of high-carbon molten iron 3.7% or more Method of melting the material.

The method for melting iron-containing cold material according to claim 1, wherein the hot metal reducing agent is supplied by charging a briquette hot metal reducing agent from the furnace.

The method for melting iron-containing cold material according to claim 1, wherein the hot metal reducing agent is supplied by blowing powder hot metal reducing agent into high carbon molten iron.