JPS5913012A - Method for protecting tuyere of blowpipe for refining molten iron - Google Patents
Method for protecting tuyere of blowpipe for refining molten ironInfo
- Publication number
- JPS5913012A JPS5913012A JP12096282A JP12096282A JPS5913012A JP S5913012 A JPS5913012 A JP S5913012A JP 12096282 A JP12096282 A JP 12096282A JP 12096282 A JP12096282 A JP 12096282A JP S5913012 A JPS5913012 A JP S5913012A
- Authority
- JP
- Japan
- Prior art keywords
- gas
- refining
- blowing
- concentration
- molten iron
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/42—Constructional features of converters
- C21C5/46—Details or accessories
- C21C5/48—Bottoms or tuyéres of converters
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
Abstract
Description
この発明は、溶鉄精錬用軟管羽目の保護方法に関し、た
とえば底吹きまたは上、底吹き゛転炉などで、酸素また
は少くともこれを含む気体よりな□る精錬用ガス気流の
吹込みに多用されている2重管タイプのような、軟管羽
目の保険流体の適合についての永年にわたる検討と実験
を経た開発成果を、新規に提案するものである。
従来、溶鉄精錬用軟管羽目の保鋤流体には、通常、OB
M/Q−BOP 、すなわち酸素底吹き転炉法で慣用の
、炭化水素系ガスたとえばプロパン・ブタンまたは天然
ガスなど、あるいはLWSと呼ばれる類似の製鋼法では
、灯油が、主として用いられ、何れも軟管羽目の細心流
としての精錬用酸化性ガス、なかでも純酸素ガスを、さ
や状にくるむ被包ガス気流として一緒に浴中へ噴射流出
させ、この被包ガスによ葛冷却i用で、羽目寿命の延長
が図られた。
しかし従来の1掲保護流体は水素原子を含みこれが鉄浴
中に吸収されて、製鋼品質上、好ましくない影響を示す
。
一方、ステンレ□ス鋼精錬におけるAOD法では、不活
性ガスとくにアルゴン、窒素など、水素原子を含まぬ保
−流体が使用されているが、上記炭化水素系ガスにおけ
るような分解熱の利用不能なため、鉄浴中に開口する軟
管羽目の先端を十分に冷却するに足る抜熱作用を生ぜず
して、羽目寿命はせいぜい850ヒート程変にとどまり
、OBM /Q−BOPにおける1 000 ヒフ )
G、1m比ベテハるかに劣る。
以上のべたところのほかにも、二酸化炭素の気体または
液体を用いることが知られていて特公昭89−2418
8号公報に前者が、そしてRev 。
Metallurgie (19り8)、p18〜19
に後者が、それぞれ開示されているが、やは″り分解反
応を伴わぬため、抜熱、冷却効果は十分でない。
すなわち、炭化水素のうちプロパン(0,H8)を例に
とると、精錬用ガスとしての酸素に対勢体積百分率でほ
ば4%程度の、被包ガス流量により、充分な軟管羽目の
保険を達し、ここにプロパンの抜熱作用は、一つに、常
温から鉄浴温度(はrflao。
℃)まで上昇する際の顕熱、いま一つとして、プロパン
が0とH8とに分解する際の吸熱が加わり、これらの熱
力学定数を石□いて算定され6抜熱量の和はぐ約1′□
□8 Kdhl/ nxol’であるのに対し、二酸化
炭素は気体の場合、単純な顕−熱度、化のみr、160
0℃に達す、る間にほぼ1 B、4 KOal/mol
、、また液体で呼蒸発熱が加わるにしても約& 1,
5 KOal/hlo、1程度でともに大差がなく、対
酸素体積百分率で、lIs〜17%、つ声り上記プロパ
ンの一倍輪、も及ぶ保−流体の供給が必要になる。ここ
に製−品質上懸念される、水素ピックアップは払拭され
るにせよ、なお保護流体使用量の着差で、プロパンよ、
り高価につく不利に加えて、転炉内熱収支の、悪(jS
を伴い、通常の吹錬よりも、鉄鉱石簿、用量をは、PI
25kg/1steel 、程度も削減しなけれ、ば、
兜じ吹止め温度が得られなくなり、この点鉄源として、
安1価な鉄鉱石使用を事実上不能にし、製、出鋼歩留り
の低下を招来する= ・さらに、
酸化性ガ1.スである二、酸化炭素、は、羽目周囲の耐
火物を酸化雰囲気にさ、らすために、通、常使用さ洟て
いるMg070系耐六5物σ?0を、親御するので耐火
1物の寿命低下が生じる。
、かように1.シて軟管−口の保護流体として1.二酸
化炭素の利用は、経済性において従来のプロパンにはる
かに及ばず、それ故、工業的に実用される段1階に至・
つ、ではい、ない。
他方、特公昭55−48ri68号公報によれば、はじ
め、に4触れたOBMプロセスに関して、1掲炭化水素
、・、希ガス類および二酸化炭素に加えて、−酸化炭素
についても、保険流体としての使用に言及されてい、る
ものの1.ぞ、の具体的な適用はす、でにのべたプロペ
ンに限ら゛れている。また特開昭66−98814号、
公報には、1、底吹精錬炉より未燃焼で回収し、た排ガ
ス”、の冷却媒体としての利用につぃ1て開示されてい
るか新設は、該排ガス中の二酸化炭素の活用に主眼がお
かれていて、該排ガス容積の大半を占める一酸化炭素に
よる伸動機能については1、全く筆画に付され、むしろ
禁忌すべき旨が言及されてい・るように、実際上、それ
による冷却。
作用の如きは、従来顧られるところさえなかったのであ
る。 ・ 。
、発明者らは、上記のような禁忌を踏み越えて果敢に、
−酸化炭素をもってす・る軟管羽口の保護に関し敢えて
究明を試みたところ、精錬用ガス流量に対する適切な供
給流量の下に、とくに有効な軟管羽目に対する冷却、保
護作用が、炭化水素系ガスによる場合と比べて何らの遜
色なく、シかもその最大の欠点である水素のピックアッ
プを、全く伴うことなくして、有利に実現されることを
見出した。
この−酸化炭素(以下単にCOで示す)の利用による、
吹錬羽口の顕著な溶損軽減の機構は、次のとおりと考え
られる。
すなわち鉄浴中への酸化性ガスの噴射流を取囲□んだ含
OO被包ガスの流出で、軟管羽目の内管と外管との間隙
上に、多孔質凝固鉄よりなるいわゆるマツシュルームが
形成されるのは従来と変りはないが、その孔隙を被包ガ
ス気流が通過するとき、次式(1)、
200→0 (S) + 00. −−−−− (
1)の反応が右へ進行して、多量の粉状炭素の析出を起
こす。
この粉状炭素は、被包ガス気流に帯同されて鉄浴中に浸
入し、一方吹管羽目の内管を通した醗素(以下単に0.
で示す)ガスと溶鉄との反応で生成した酸化鉄F60と
の間で、次式(2)、0(S) + Fe0−+Na
+ 00 −−−−− (2)の吸熱反応を生じ、この
反応熱によって軟管羽目の先端周辺が有効に冷却される
。
加えて、0.ガスが鉄浴中に吹込まれて大量に生成した
FeOが、軟管羽口の先端周辺の耐火物と反応して、そ
の融点を下げ、高温の溶鉄によって該耐火物が溶損する
おそれがあったところ、00の吹込みは、次式(8)
%式%(8)
の反応でFeOを還元し、該周辺でのFeO濃度を下げ
る点でも有利である上、COは還元性であるため、すで
に従来技術として掲げたCO8が酸化性であるのに対し
、とくに底吹き転炉の炉底耐大物として有用な、マグネ
シア・カーボン系ないしマグネシア・ドロマイ)・カー
ボン系れんがの酸化による劣化の観点からも有利である
。
上に説明した羽目ならびにその周辺耐火物の溶接軽減機
構、とくに1掲(2)式の吸熱反応を利用して羽目保護
効果を高めるためには、(1)式の反応に基く粉状炭素
の析出を十分に図ることが望ましく、この点、被包ガス
中の00濃度が高いほど有利である。
しかしながら被包ガスとして高00濃度たとえば純粋な
OOガスを使用することはコストの上昇を招き、低コス
ト化が叫ばれる現状と逆行する。1この点、製鉄所内に
おいて入手容易で多量の00を含む、転炉などの精錬容
器から゛未燃焼裡に回収された排ガスを利用できればコ
ストの面でも極めて有利なのであるが、一般にたとえば
転炉排ガスを未燃焼裡に回収する際には空気の混入が避
は鍾く、このため回収した転炉排ガス中には表1に示し
たようにかなりの窒素(以下単にN、で示す)が混在し
ている。
表 1
かような比較的多量のN、を含有する転炉排ガスをその
まま被包ガスとして利用した場合には、溶銑中窒素濃度
の上昇を招き、鋼品質の劣化をもたらすことが判明した
。
そこで発明者らは、未燃焼裡に回収した転炉排ガスを、
N、の吸着塔に通して該排ガス中のN、を吸着除去し、
種々のN、濃度に調整し、これらの排ガスを被包ガスに
用いて数多くの実験と検討を行ったところ、羽目の有効
保護に必要な被包ガス流量は底吹き08ガス流量によっ
て定まり、上記の転炉排ガスを用いる場合は00分で底
吹き0.ガス流量の5〜go%程度が適切であること、
また溶鉄中のN、濃度は、被包ガス中のN、濃度ならび
にその流量に依存することが判明し、従って溶鉄中N、
濃度の実質的な上昇防止のためには被包ガス(10)
中のNg濃度の上限を、底吹きO,ガス流産比率すなわ
ち上、底吹き0.ガス全流社に対する底吹き0gガス流
量によって規定すればよいことを突止め、かくして溶鉄
中N、 6度の上昇を招くことなしに、とくに有効な軟
管羽目の冷却、保睦が、炭化水竺禾ガスによる場合に比
べて何らの遜色なく有利に実現され得ることを見出した
のである。
この発明は、か、ような知見に基くものであって、鋼中
水素は勿論N、濃度の上昇を伴うことなく、シかも安価
に、溶鉄精錬用軟管羽目ならびにその周辺耐火物の損耗
を軽減することを目的とするものである。
この発明による上記目的の達成は、次の構成を解決手段
の要点とするものである。
この発明に従う溶鉄精錬は、上記の軟管羽目を精錬用ガ
スの鉄浴中吹込みに用いる限り、いわゆる底吹き転炉、
上、1底吹き転炉や、電気炉または平炉あるいは、AO
D法などのような、精蝕容器などを、その種類の如興に
拘らず適用で主、4た溶鉄についても、高炉溶銑を主体
とする鉄−炭素系−(11)
はもちるん電気炉などにより主としてスクラップの如き
溶解した鉄−炭素系の浴や主にAOD法での精錬に供さ
れるような、高合金スクラップを主原料とする高合金、
鉄−炭素氷浴などの何れであってもよい。
またこの発明で、溶鉄精錬に用いる軟管羽目は、従来通
りの一般的な同心2重管溝りのものを、そのまま用いて
、内管から酸素またはこれを含む気体よりなる精錬用ガ
ス気流を、そして外管、いま少しくわしく云うと内管と
外管との間のli!illがら、軟管羽目先端に対する
冷却、作置奪回る被包ガス気流を、それぞれ精錬容器内
に収容した鉄浴中に吹込む慣例に従って適用する。
この発明では、かかる被包ガスとしてとくにN、濃度を
低減した精蝕炉排ガスが、すでに述べたようにして、従
来のプロパンに匹敵する軟管羽口の冷却、作置作用を、
プロパンの使用に寸前して不可避の水素ピックアップの
弊害を生じることなしに、実現し得ることの知見事実に
由来しているO ・
、 ここに被包ガス中のN、濃度ON(%)は、qoテ
精錬用のO,ガス全流量(Nm8/m1n)、q、Pテ
吹管羽目からの0.供給流量(Nm’Ainjをそれぞ
れあられすものとして、次式(4)、” □
ON言−−5 、 o /q(、、−(4) 。
に従う限りにおいて、この発明の目的に適合することが
確められている0″ □
さてこの発明に従う吹管羽゛口の保護機能に関しミ炉容
5トンの底吹き転炉で吹錬′を実行した゛試験例につい
て説朗す名6 − ・ ゛第1図に、底
吹き転炉の炉尿゛面を、ま壕第1図にはそのA’−A’
矢視面番示す。この底吹き転炉+は、炉壁鉄皮1゛を高
′温焼成マグネシア・ドロ゛マイ)れんが2にて内張り
し、□またマグネジ″ア・力―゛ボンんが8で築伍した
転炉の゛炉底部4−に4″個の□2重管羽口5を、□ト
→ニオン軸パ(゛図示省略)と平行に一列に配列した。
□ □ ゝこご゛に02ガスの通過ザ
る内管6には、内径□8闘、外径12.ツーめ銅管を用
いミまた保護流体を□通過させる環状周隙を形づくる外
管7.には、内径1、、.9.q、u、、外径19.0
5m5+の銅!管を用いた。従って内管、6.と外管7
とで形成される環状周隙は0.6闘であ、つ、また。
。
各喀、管、羽5口6は、第2図、第8図に示したように
、内管6やこ配管8、分岐管9およびヘッダlOを介し
て精錬用ガスの供給管11をつなぎ、外管7には、配、
管1g、分岐管18を介して、この試験、ではとくに2
連とした保護流体供給管14@Np4を連ねた。なお図
、示しなし)が、供給管11,14お、よび1.5は、
転、炉の非吹錬時たとえば傾動中など、←1.溶昧浴の
静圧と対抗するのに必要な1.不活性朽ス圧力源と切替
え可能に接続した。
この、転・炉に、次の組成の高炉溶銑を装入した。
0:4.町重量%(以下単に%で示す)、i91 !
0.88’%、)in 、、: 0.41%、P、10
.10%、S ! 0.086 %。
また溶、銑m度は1200℃であった。
この装入中、各軟管羽目6に、その内管にはu、g 5
Nm / min 、外管7にはOJ 8 Nm /
minでそれぞれNsガスを供給して羽目の閉塞を防ぎ
、装人終了鋒直ちに転炉を直立姿勢にして、次の吹錬を
行った。
試験例1
軟管羽口5の1本当り、内管6から0.ガスを1.25
Nm8/minの割合で供給し、被nガスについては
、第1図にaとbとで区別した2本宛に、a群の外管7
には、底吹き02流量に対し20%に相当’f ル0.
25 Nm /minで84%C0−5%C02−8%
N2−3%N2の組成に成分調整した転炉排ガスを、ま
た同じくb群については0.10 Nm /min 1
のプロパンを羽口1本当りそれぞれ供給する一方、転炉
の炉口から上吹きランスを炉内に挿入し、6Nm 7’
minの02ガスを溶銑浴面に吹付けて底吹き精錬ガス
量の不足を補い、また吹錬開始と同時に150に9の焼
石灰を炉頂から溶銑上に添加し約20゛分間の吹錬を行
った。
ついで上吹きランスを引上げるとともに、各軟管羽目5
へは1掲のN2の供給に切替え、引続き転炉を装入側へ
傾け、溶鋼の測温とサンプリングを行い、次の吹錬成績
を得た。
0 : 0.0 2 %、In + 0.2
4 %、Si:tr。
P : 0,0 1 5 %、S : 0.0
21 %、W1#!湛度: 1660°C0
そこで出鋼側へ反転細動して取鍋に出鋼した上で再び装
入側に炉体を傾けて炉口より溶滓を排除して空炉にする
と共に、N、の供給を止め、第2図、第8図に示した内
管直下の点検用プラグ1Bを取除いて軟管羽目5の先端
溶損を計測したところ、a群すなわちこの発明に従う転
炉排ガスを適用したものは、上記の1チヤージで1.6
111i、1.9闘の溶損であったのに対し、b群すな
わちプロパンで冷却したものは、9.3sm、2.4m
mであった。
なおこれらの測定値は、内管6の端面輪郭の周上6ケ所
の平均値で示した。
この試験の被包ガス使用量は20%であるが、後述の試
験例にも示すように、15〜20%の使用量においては
、従来の一般的な使用量でのプロパンを凌いだ溶損防止
効果が明らかになった。
試験例2
軟管羽口6の内管6へは、1本当り1.25、 Nu8
/minの02ガスを、外管?へはatbil[ii群
ヲ通じ底吹き0□流量に対し15%に相当する0、19
1Jm8/mi、nで上記した試験例1と同じ組成にな
る転炉排ガスをそれぞれ供給し、底吹きのみで吹錬を行
った。このときの羽目損耗量は1.9〜2.1 s〆チ
ャージであり、やはりプロパンと同等以上の溶損防止効
果が認められたが、この場合は、溶鉄中のN、濃度が2
8 ppmであって通常のプロパンを用いた場合と比較
して5〜10 ppm程度高いことが明らかにされた。
かようにN、濃度が高い溶鉄は、低N、が要求される5
鋼種に対してはその用途に供し得ない。
そこで、プロパン並の羽目保護機能を実現でき、かつ通
常製品の品質上問題がないとされるgoppm以下程度
のN、濃度を満足する被包ガス中におけるN濃度を究明
すべく、種々のN、濃度に鉤整しま
た転炉排ガスを用いて、溶鉄中のN、濃度と、被包ガス
中のN、濃度および吹込み量との関係について調べた。
実験は、底吹きのみおよび上、底吹き併用いずれの場合
も、全体の011ガス流量はl ONm /minと一
定にし、上、底吹き各0.流量を種々の割合に変更する
条件で行った。また被包ガス流量は底吹きO,ガス量の
15〜20%の範囲とした。なお全0.ガス流量に対す
る底吹き0.ガス流量の割合が0.1の場合は、4本の
軟管羽目のうち8本は閉塞し、1本のみの使用で行った
。得られた結果を第4図にまとめて示す。
同図に示した成績から明らかなように、溶鉄中のN、濃
度は、全0.ガス流量に対する底吹き0゜ガス流量の割
合ならびに被包ガス中のN、濃度に依存し、通常、製鋼
品質上問題がないとされる20ppm以下とするには、
被包ガス中のN、濃度が全0.ガス流量きの場合2.5
%以下、50%底吹きて5%以下、さらに10%底吹き
で2゛6%以下にすればよいことを突止めた。
以上の結果をまとめて、精錬用のO,ガス全流量q。(
1m8/m1n)に対する軟管羽目からのO,ガス供給
量をq、F (Nm’/h+in)で表わした場合、溶
鉄中N8濃度の有効な低減に必要な被包ガス中のN、濃
度ON、(%)は、
で与えらnる。
なお上述の試験吹錬で、吹止め時に採取した溶鋼試料の
水素濃度は、この発明に従うとき1.8〜g、oppm
であり、プロパンを使用した場合が、4.5±1.2
ppm程度であるのと比べて、事実上水素のピックアッ
プは生じないということができる。
ところで、未燃焼裡に回収した転炉排ガスから所定の濃
度までN、ガスを除去するには、該排ガスを、吸着剤を
充満した吸着塔に圧送する脱N。
処理工程が必要になるが、この脱N、には費用がかさむ
。従って吹錬全期間にわたって脱N、処理を施した転炉
排ガスを使用することはコストの面から好ましくない。
そこで発明者らは、かような脱N、処理に要する費用の
削減も併せて達成すべく、溶鉄中N、濃度の上昇防止の
ために必要とする、この発明に従う低N、転炉排ガスの
使用期間についても、研究を重ねた。一般に吹錬の初期
で脱炭による00ガスの発生が盛んなときは脱ガス効果
が高く、従ってN、ガスを吹込んでもほとんどが浴外へ
排出されるので、IIT、が溶鉄中に吸収される心配は
少い0よって実験は吹錬の後半について重点的に行った
。
実験は前述した試験吹錬に準じ、精錬用の0゜ガス流量
は10 Nm’/minとし、5 Nm’/min t
t吹管羽目から、残りの51m”、、’h+inを上吹
きランスからそれぞれ供給した。また被包ガス流量は、
底吹き0、ガス流量の15〜Bθ%の範囲とした。この
実験では、吹錬開始初期は、00280〜98%、1o
o、 s a 〜 6 ラ曙; 、 N、 !
6 〜9 ラ響; 、 H,寞 8〜45曜iの
組成になる転炉排ガ天を脱N、処理なしにそのまま使用
し、吹錬の途中にて、この発明に従うN。
濃度範囲を満足する2〜5%N、濃度まで脱N、処理を
施した転炉排ガスに切替えることによって行った。なお
吹止め時の溶鋼温度は1680〜1090°Cで、吹止
めThe present invention relates to a method for protecting the lining of soft pipes for smelting molten iron, and is often used for blowing a refining gas stream made of oxygen or at least a gas containing oxygen in, for example, bottom blowing or top or bottom blowing converters. This is a new proposal based on the results of many years of research and experimentation regarding the suitability of insurance fluids for soft pipe linings, such as the double pipe type that has been developed. Conventionally, OB
Hydrocarbon gases such as propane, butane or natural gas commonly used in M/Q-BOP, the oxygen bottom-blown converter process, or kerosene in a similar steelmaking process called LWS, both of which are soft Oxidizing gas for refining, especially pure oxygen gas, is injected into the bath as a fine flow of the pipe siding, and the encapsulated gas is used for cooling by this encapsulated gas. Efforts were made to extend the life of the feather. However, the conventional Class 1 protective fluid contains hydrogen atoms, which are absorbed into the iron bath and have an unfavorable effect on the quality of steel production. On the other hand, in the AOD method in stainless steel refining, a holding fluid that does not contain hydrogen atoms, such as an inert gas, especially argon or nitrogen, is used. As a result, there is no heat removal effect sufficient to sufficiently cool the tip of the soft tube lining that opens into the iron bath, and the lining life is only 850 heats at most, which is 1000 heat in OBM/Q-BOP.
G, 1m comparison is much inferior. In addition to the above-mentioned methods, it is known that carbon dioxide gas or liquid can be used.
The former is in Publication No. 8, and Rev. Metalurgie (19ri 8), p18-19
The latter are disclosed in the following, but since they do not involve a decomposition reaction, the heat removal and cooling effects are not sufficient. In other words, taking propane (0, H8) among hydrocarbons as an example, The flow rate of the encapsulated gas, which is about 4% in terms of volume percentage against the oxygen used as the operating gas, achieves sufficient insurance for the soft pipe wall, and the heat removal effect of propane is one of the reasons why Sensible heat when the temperature rises to the bath temperature (rflao. °C) is added, as well as endothermic heat when propane decomposes into 0 and H8, and calculated by setting these thermodynamic constants, the amount of heat extracted is 6. The sum is about 1'□
□8 Kdhl/nxol', whereas when carbon dioxide is a gas, it has a simple sensible temperature, oxidation rate, 160
Approximately 1 B, 4 KOal/mol while reaching 0°C
,,Also, even if heat of vaporization is added to the liquid, it will be about & 1,
5 KOal/hlo is about 1, which is not much different in both cases, and the volume percentage relative to oxygen is 17%, and it is necessary to supply a retaining fluid that is about 1 times the volume of propane. Made here - Even though hydrogen pickup, which is a quality concern, has been eliminated, there is still a difference in the amount of protective fluid used, and propane,
In addition to the disadvantage of being expensive, the heat balance inside the converter is poor (jS
Accompanied by normal blowing, the iron ore list, dosage is PI
25kg/1steel, unless the degree is reduced,
It became impossible to obtain the temperature at the end of the helmet, and as a point iron source,
This makes it virtually impossible to use cheap iron ore, leading to a decline in production and steel tapping yields = ・Furthermore,
Oxidizing moth 1. Carbon oxide, which is a carbon oxide, is a Mg070-based 65-resistant σ? 0, the lifespan of the refractory material will be reduced. , like this 1. 1. As a protective fluid for the soft tube and mouth. The use of carbon dioxide is far less economical than conventional propane, and therefore has not yet reached the first stage of industrial practical use.
Well, no. On the other hand, according to Japanese Patent Publication No. 55-48ri68, regarding the OBM process mentioned in 4 above, in addition to hydrocarbons listed in 1., rare gases, and carbon dioxide, -carbon oxides can also be used as insurance fluids. Of the things mentioned: 1. The specific application of this is limited to the propene mentioned above. Also, JP-A No. 66-98814,
The bulletin discloses 1. The use of "unburned exhaust gas recovered from bottom-blown smelting furnaces" as a cooling medium. Regarding the expansion function of carbon monoxide, which is present and accounts for most of the volume of exhaust gas, cooling by carbon monoxide is not mentioned at all, and is actually contraindicated. Such effects had not even been considered in the past.The inventors boldly went beyond the above-mentioned taboos and
- An attempt was made to investigate the protection of soft pipe tuyere using carbon oxide, and it was found that hydrocarbon-based It has been found that the present invention is comparable to the case using gas, and can be advantageously realized without any hydrogen pickup, which is its biggest drawback. By using this carbon oxide (hereinafter simply referred to as CO),
The mechanism by which the blowing tuyere significantly reduces erosion loss is thought to be as follows. In other words, due to the outflow of OO-containing encapsulated gas surrounding the jet flow of oxidizing gas into the iron bath, so-called pine mushrooms made of porous solidified iron are formed in the gap between the inner and outer tubes of the soft tube lining. is formed as before, but when the encapsulated gas flow passes through the pores, the following equation (1), 200→0 (S) + 00. −−−−− (
The reaction 1) proceeds to the right, causing the precipitation of a large amount of powdered carbon. This powdered carbon is entrained in the encapsulated gas airflow and permeates into the iron bath, while the sulfur (hereinafter simply referred to as 0.
The following formula (2), 0(S) + Fe0-+Na
+ 00 ------ (2) The endothermic reaction occurs, and the area around the tip of the soft tube slats is effectively cooled by this reaction heat. In addition, 0. When the gas was blown into the iron bath, a large amount of FeO was produced, which reacted with the refractory material around the tip of the soft tube tuyere, lowering its melting point and causing the risk of the refractory material being melted away by the high-temperature molten iron. However, the blowing of 00 is advantageous in that it reduces FeO by the reaction of the following formula (8) % formula % (8) and lowers the FeO concentration in the vicinity, and since CO is reducing, While CO8, which has already been cited as a conventional technology, is oxidizing, it is useful from the viewpoint of deterioration due to oxidation of magnesia-carbon-based or magnesia-dolomy (magnesia-dolomy) carbon-based bricks, which are particularly useful as bottom-resistant materials for bottom-blowing converters. is also advantageous. In order to enhance the weld protection effect of the siding and the surrounding refractories described above, especially by utilizing the endothermic reaction of equation (2) listed above, it is necessary to use powdered carbon based on the reaction of equation (1). It is desirable to achieve sufficient precipitation, and in this respect, the higher the 00 concentration in the encapsulated gas, the more advantageous it is. However, using a high 00 concentration, for example, pure OO gas, as the encapsulating gas increases cost, which runs counter to the current demand for cost reduction. 1 In this regard, it would be extremely advantageous in terms of cost if it were possible to use unburned exhaust gas recovered from a refining vessel such as a converter, which is easily available and contains a large amount of 00 within a steelworks. When recovering unburned waste gas, it is difficult to avoid mixing of air, and therefore, as shown in Table 1, a considerable amount of nitrogen (hereinafter simply referred to as N) is mixed in the recovered converter exhaust gas. ing. Table 1 It has been found that if converter exhaust gas containing such a relatively large amount of N is used as it is as encapsulating gas, the nitrogen concentration in the hot metal will increase and the quality of the steel will deteriorate. Therefore, the inventors collected the unburned converter exhaust gas,
Adsorbing and removing N in the exhaust gas by passing it through an N adsorption tower,
After conducting numerous experiments and studies using various N and concentrations and using these exhaust gases as the encapsulating gas, we found that the encapsulating gas flow rate required for effective protection of the lining was determined by the bottom blowing 08 gas flow rate, and the above When using a converter exhaust gas of 0.00 minutes, the bottom blows 0. Approximately 5-go% of the gas flow rate is appropriate;
It was also found that the concentration of N in molten iron depends on the concentration of N in the encapsulated gas and its flow rate.
In order to prevent a substantial increase in the concentration, the upper limit of the Ng concentration in the encapsulated gas (10) should be set to 0. It was discovered that the gas flow rate should be specified by the bottom blowing 0g gas flow rate for Gas Zenryusha, and thus it was found that the cooling and preservation of the soft pipe wall was particularly effective without causing an increase in N in the molten iron by 6 degrees. They have discovered that this can be achieved with no inferiority and advantages compared to the case of using pure gas. This invention is based on this knowledge, and it is possible to reduce the wear and tear of soft pipe linings for molten iron refining and the surrounding refractories at low cost without increasing the concentration of hydrogen or N in steel. The purpose is to reduce the To achieve the above object according to the present invention, the following configuration is the main point of the solution. Molten iron refining according to the present invention can be carried out using a so-called bottom-blown converter, as long as the above-mentioned soft pipe lining is used for blowing refining gas into the iron bath.
Top, one bottom blowing converter, electric furnace, open hearth or AO
It is mainly applied to the D-method, etc., regardless of the type of eclipse container, etc., and also for molten iron, which is mainly made of blast furnace hot metal - carbon-based (11) Hamochirun Denki. High alloys whose main raw materials are high alloy scraps, such as melted iron-carbon baths such as scraps in furnaces, etc., and high alloy scraps, which are mainly used for refining by the AOD method.
Any method such as an iron-carbon ice bath may be used. In addition, in this invention, the soft pipe surface used for molten iron refining is a conventional general concentric double pipe groove type, and a refining gas airflow consisting of oxygen or a gas containing oxygen is passed from the inner pipe. , and the outer tube, to be more specific, the li between the inner tube and the outer tube! In addition, a cooling and enveloping gas flow to the tip of the soft tube siding is applied according to the customary practice of blowing into an iron bath contained in a refining vessel. In this invention, the encapsulating gas is N, and the cleaning furnace exhaust gas with a reduced concentration has a cooling and setting effect on soft tube tuyere comparable to that of conventional propane, as described above.
The concentration of N in the encapsulated gas (ON (%)) is derived from the knowledge that it can be realized without causing the inevitable adverse effects of hydrogen pickup just before the use of propane. qo Te O for refining, total gas flow rate (Nm8/m1n), q, P Te 0. Assuming that the supply flow rate (Nm'Ainj is each increment), the following formula (4), " □
It has been confirmed that the object of the present invention is met as long as the ON statement--5, o/q(,,-(4)) is followed. I will explain about a test example in which blowing was carried out in a bottom-blowing converter with a furnace capacity of 5 tons. 6 - ・ Figure 1 shows the furnace surface of a bottom-blowing converter, and Figure 1 shows the furnace surface of a bottom-blowing converter. is that A'-A'
The arrow plane number is shown. This bottom-blown converter + has a furnace wall steel shell 1 lined with high temperature fired magnesia dolomite bricks 2, At the bottom 4- of the furnace, 4'' double-tube tuyeres 5 were arranged in a line parallel to a □-to-nion axis member (not shown). □ □ The inner pipe 6 through which the 02 gas passes through has an inner diameter of □8 and an outer diameter of 12. 7. The outer tube is made of double-metal copper tube and forms an annular gap through which the protective fluid passes. has an inner diameter of 1, . 9. q, u, outer diameter 19.0
5m5+ copper! A tube was used. Therefore, the inner tube, 6. and outer tube 7
The annular gap formed by and is 0.6 mm.
. As shown in FIGS. 2 and 8, each tube, tuyer 5, and port 6 are connected to a refining gas supply pipe 11 via an inner pipe 6, a pipe 8, a branch pipe 9, and a header lO. The outer tube 7 includes a
In this test, in particular 2
A continuous protective fluid supply pipe 14@Np4 was connected. Note that the supply pipes 11, 14 and 1.5 are
When the furnace is not blowing, such as during tilting, ←1. 1. necessary to counteract the static pressure of the dissolution bath. switchably connected to an inert gas pressure source. Blast furnace hot metal having the following composition was charged into this converter/furnace. 0:4. Town weight% (hereinafter simply expressed as %), i91!
0.88'%,)in,,: 0.41%,P,10
.. 10%, S! 0.086%. Moreover, the melting temperature and pig iron temperature were 1200°C. During this charging, each soft tube layer 6 has u, g 5 in its inner tube.
Nm/min, OJ for outer tube 7 8 Nm/min
Ns gas was supplied at a minimum of 100 mL to prevent clogging of the siding, and immediately after finishing the installation, the converter was placed in an upright position and the next blowing process was carried out. Test Example 1 One soft tube tuyere 5, 0.0 from the inner tube 6. 1.25 gas
The N gas is supplied at a rate of Nm8/min.
For the bottom blow 02 flow rate, it is equivalent to 20% of the bottom blow 02 flow rate.
84%C0-5%C02-8% at 25 Nm/min
Converter exhaust gas whose composition was adjusted to N2-3%N2, and also for group b, 0.10 Nm/min 1
While supplying propane to each tuyere, a top blowing lance was inserted into the furnace from the converter mouth, and 6Nm 7'
02 gas was sprayed onto the surface of the hot metal bath to make up for the lack of bottom blowing refining gas, and at the same time as blowing started, 150 to 9 burnt lime was added to the hot metal from the top of the furnace, and blowing was continued for about 20 minutes. I did it. Then, while pulling up the top blow lance, each soft pipe siding 5
The supply of N2 was switched to the one listed above, and the converter was then tilted toward the charging side. The temperature of the molten steel was measured and sampled, and the following blowing results were obtained. 0: 0.02%, In+0.2
4%, Si:tr. P: 0.015%, S: 0.0
21%, W1#! Flooding level: 1660°C0 Then, the steel is reversed to the tapping side and tapped into the ladle, and the furnace body is again tilted to the charging side to remove the molten slag from the furnace mouth and make the furnace empty. , and the inspection plug 1B directly under the inner pipe shown in FIGS. 2 and 8 was removed to measure the melting damage at the tip of the soft pipe siding 5. The one that applies the above 1 charge is 1.6
111i, the corrosion loss was 1.9 m, while the b group, that is, the one cooled with propane, had a loss of 9.3 sm, 2.4 m.
It was m. Note that these measured values are shown as average values at six locations on the circumference of the end face contour of the inner tube 6. The amount of encapsulated gas used in this test was 20%, but as shown in the test example below, at a usage amount of 15 to 20%, the erosion loss exceeded that of propane at the conventional general usage amount. The preventive effect has been revealed. Test Example 2 To the inner pipe 6 of the soft pipe tuyere 6, 1.25 per piece, Nu8
/min 02 gas, outer tube? Atbil [0, 19 equivalent to 15% of the bottom blow 0□ flow rate through group II]
Converter exhaust gas having the same composition as in Test Example 1 described above was supplied at 1 Jm8/mi, n, and blowing was performed only by bottom blowing. The amount of damage to the siding at this time was 1.9 to 2.1 s〆charge, and the effect of preventing erosion was equal to or higher than that of propane. However, in this case, the N concentration in the molten iron was
8 ppm, which is about 5 to 10 ppm higher than when normal propane is used. Thus, molten iron with a high N concentration requires low N.
It cannot be used for that purpose for steel types. Therefore, in order to find out the N concentration in the encapsulated gas that can achieve the same level of lining protection function as propane and satisfy the N concentration below goppm, which is considered to have no problem with the quality of normal products, various N, The relationship between the concentration of N in molten iron and the concentration of N in encapsulated gas and the amount of injection was investigated using converter exhaust gas. In the experiment, the overall 011 gas flow rate was kept constant at 1 ONm /min in both cases of bottom blowing only and top and bottom blowing in combination, and 0.000. The tests were carried out under conditions where the flow rate was changed to various ratios. Further, the flow rate of the encapsulating gas was set to be bottom blowing O and in the range of 15 to 20% of the gas amount. In addition, total 0. Bottom blow to gas flow rate 0. When the gas flow rate ratio was 0.1, 8 of the 4 soft tube slats were occluded, and only one was used. The obtained results are summarized in FIG. 4. As is clear from the results shown in the same figure, the total N concentration in the molten iron is 0. It depends on the ratio of the bottom blowing 0° gas flow rate to the gas flow rate and the concentration of N in the encapsulated gas, and to keep it below 20 ppm, which is usually considered to cause no problem in steel manufacturing quality,
The total concentration of N in the encapsulated gas is 0. 2.5 for gas flow rate
% or less, 50% bottom blowing to 5% or less, and 10% bottom blowing to 2.6% or less. Summarizing the above results, the total flow rate of O and gas for refining is q. (
When the amount of O and gas supplied from the soft pipe surface per 1m8/m1n) is expressed as q,F (Nm'/h+in), the N and concentration in the encapsulated gas necessary to effectively reduce the N8 concentration in molten iron are: , (%) is given by n. In addition, in the above-mentioned test blowing, the hydrogen concentration of the molten steel sample taken at the time of blow-stopping is 1.8 to 1.8 g, oppm according to the present invention.
and when propane is used, it is 4.5±1.2
Compared to the amount of about ppm, it can be said that virtually no hydrogen pickup occurs. By the way, in order to remove N and gas to a predetermined concentration from the converter exhaust gas recovered while it is still unburned, de-Ning is performed by pumping the exhaust gas to an adsorption tower filled with an adsorbent. Although a treatment process is required, this de-N removal is expensive. Therefore, it is not preferable from a cost standpoint to use converter exhaust gas that has been subjected to de-N removal and treatment throughout the blowing period. Therefore, in order to achieve such de-N removal and reduction of the cost required for treatment, the inventors developed a low-N, converter exhaust gas according to the present invention, which is necessary to prevent the concentration of N in molten iron from increasing. We also conducted repeated research on the period of use. In general, when the generation of 00 gas due to decarburization is active in the early stage of blowing, the degassing effect is high, so even if N and gas are blown, most of it is discharged outside the bath, so IIT is absorbed into the molten iron. Therefore, the experiment focused on the second half of blowing. The experiment was conducted in accordance with the test blowing described above, with the 0° gas flow rate for refining being 10 Nm'/min and 5 Nm'/min t.
The remaining 51 m'', 'h+in' were supplied from the upper blow lances from the t-blowpipe section. Also, the encapsulated gas flow rate was as follows:
The bottom blow was 0 and the gas flow rate was in the range of 15 to Bθ%. In this experiment, the initial stage of blowing was 00280~98%, 1o
o, s a ~ 6 la dawn; , N, !
6-9 Rakyo; , H, 寞 8-45 The converter exhaust gas having a composition of I is used as it is without de-Ning or treatment, and in the middle of blowing, N according to the present invention is used. This was done by switching to converter exhaust gas that had been de-Ned and processed to a concentration of 2 to 5% N, which satisfied the concentration range. The molten steel temperature at the time of blow-stopping is 1680 to 1090°C.
〔0〕濃度は0.02〜0.85%であった。
第6図に、この発明に従う低N、転炉排ガスで吹錬した
期間の脱炭量Δ0(jO−被包ガス切替え時の[0] Concentration was 0.02-0.85%. Figure 6 shows the amount of decarburization Δ0 (when switching to jO-encapsulated gas) during the period of blowing with low N and converter exhaust gas according to the present invention.
〔0〕−
吹止め[0]-
stopper
〔0〕)と吹止め時の溶鉄中N、濃度との関係を
示す。 ・同図に示したように、上記脱炭□
量Δ0と溶鉄中N。
濃度との間には明瞭な関係があり、−濃度を鋼品質問題
がないとされるB Oppm以下に抑制するには被包ガ
スの切替えを、溶鉄中[0]) and the N concentration in the molten iron at the time of blow-stopping.・As shown in the figure, the above decarburization □
amount Δ0 and N in molten iron. There is a clear relationship between the encapsulation gas and the molten iron concentration.
〔0〕濃変が吹止め[0] Dark change stops blowing
〔0〕値より
少くとも0.76%を上まわるAt least 0.76% higher than the [0] value
〔0〕濃度に達した時期
に行えばよいことが明らかになった。従って溶鉄中N、
濃度の上昇防止、の□ためには、吹錬開始から中期にか
けてはことさら低N、転炉排ガスを□使用する必要はな
く未処理の生の転・炉排ガスを用いることができるので
、その分吠錬コストの低減が可能となる。
なおこの発明は、単なる8重管羽口の冷却に限定されず
、一般に0.ガス噴出管に付帯する保”論流体噴出管を
用いる場合にも適用することができる。
・・以上述べたよ・う
にこの発明によれば、軟管羽目の先端を含め、その周辺
れんがの溶損防止を、精錬容器から未燃焼裡に回収した
排ガスの有効利用(BO。
によって安価に、また°水素さらには窒素のピックアッ
プを伴う、ことなしに実現できる。It has become clear that this should be done when the [0] concentration is reached. Therefore, N in molten iron,
In order to prevent the concentration from increasing, it is not necessary to use particularly low N and converter exhaust gas from the start of blowing to the middle stage, and untreated raw converter and furnace exhaust gas can be used. It is possible to reduce the training cost. Note that this invention is not limited to mere cooling of an octet tube tuyere, but generally 0. It can also be applied when using a protective fluid ejection pipe attached to a gas ejection pipe.
As described above, according to the present invention, the erosion of the surrounding bricks, including the tips of the soft pipe slats, can be prevented by effective utilization (BO) of the unburned exhaust gas recovered from the refining vessel at low cost. It can also be achieved without hydrogen or even nitrogen pickup.
第1図は底吹き転炉の炉床面を示す横断面図、第8図は
そのムーム′矢視図、
第8図は炉床の裏面図1
そして第4図は吹錬終了時の溶鉄中N、濃度と被包ガス
中のN、濃度との関係について示したグラフ
第6図はこの発明に従う低N、転炉排ガスで吹錬した期
間の脱炭量Δ0と吠止め時の溶鉄中N、濃変との関係を
示したグラフである。
特許出願人 川崎製鉄株式金社
′=C]
第4図Figure 1 is a cross-sectional view showing the hearth surface of a bottom blowing converter, Figure 8 is a view from the Moum' arrow, Figure 8 is a back view of the hearth 1, and Figure 4 is the molten iron at the end of blowing. Figure 6 is a graph showing the relationship between the medium N concentration and the N concentration in the encapsulated gas, which shows the amount of decarburization Δ0 during the period of blowing with low N and converter exhaust gas according to the present invention, and the amount of decarburization in molten iron during barking. It is a graph showing the relationship between N and darkening. Patent applicant Kawasaki Steel Corporation Kinsha'=C] Figure 4
Claims (1)
よりなる精錬用ガス気流を、該ガス気流の周囲に流出す
る被包ガス気流とともに、精錬容器内に収容した鉄浴中
に吹込む、溶鉄精錬用軟管羽目に、該被包ガス気流とし
て、精錬容器から放出されて未燃焼裡に回収をした排ガ
スを、そのうち窒素について次式%式% 式中ON、:被包ガス中の窒素濃度(%)qo +精錬
用の酸素カス全流量(Nm /hlin)qoB :軟
管羽目の酸素供給流ii (Nm”7m1n)に従い除
去をして供給することからなる、溶鉄精錬用軟管羽目の
保険方法。 区 窒素の除去が、吹止め〔0〕値より少くとも0.7
6%を上まわる〔0〕濃度に達した脱炭末期である、l
記載の方法。 ′& 軟管羽目が、2重管よりなり、内管から精錬用ガ
ス、外管より被包ガスを、それぞれ鉄浴中に吹込むもの
である、1または2記載の方法。 □ 表 精錬操作が、専ら軟管羽目からのガス吹込みによる
ものであり、被包ガス中の窒素濃度が2.5%未満であ
る、1.2または8記載の方法。 4 精錬操作が、上吹きランスからの精錬ガス吹付けに
よる助成を伴い、その上吹き酸素供給量をq。Tであら
れして被包ガス中窒案濃度ONが ON、≦L 5 (qoB+q、”)/ q。 である、1.2または8記載の方法。[Scope of Claims] 1. A refining gas stream consisting of oxygen or a gas containing oxygen is passed through the wall of the refining vessel, together with an encapsulated gas stream flowing out around the gas stream. The exhaust gas discharged from the refining vessel and recovered unburnt as the encapsulated gas stream is blown into the soft pipe lining for molten iron refining into the bath, and the nitrogen content is expressed by the following formula % formula % where ON: Nitrogen concentration in the encapsulated gas (%) qo + total flow rate of oxygen residue for refining (Nm /hlin) qoB: consists of removing and supplying according to the oxygen supply flow ii (Nm"7mln) of the soft pipe lining, Insurance method for soft pipe lining for molten iron smelting. Nitrogen removal is at least 0.7 below the blow stop [0] value.
At the final stage of decarburization, when the concentration exceeds 6% [0], l
Method described. '& The method according to 1 or 2, wherein the soft pipe wall is made of a double pipe, and the refining gas is blown into the iron bath from the inner pipe, and the encapsulating gas is blown into the iron bath from the outer pipe. □ Table The method according to 1.2 or 8, wherein the refining operation is carried out exclusively by blowing gas through the soft pipe lining, and the nitrogen concentration in the encapsulated gas is less than 2.5%. 4. The refining operation is assisted by blowing refining gas from the top blowing lance, and the top blowing oxygen supply amount is q. 8. The method according to 1.2 or 8, wherein the concentration of nitrogen in the encapsulated gas is ON and ≦L 5 (qoB+q,'')/q.
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP12096282A JPS5913012A (en) | 1982-07-12 | 1982-07-12 | Method for protecting tuyere of blowpipe for refining molten iron |
US06/511,511 US4436287A (en) | 1982-07-12 | 1983-07-06 | Method for protecting tuyeres for refining a molten iron |
EP83304012A EP0099713B1 (en) | 1982-07-12 | 1983-07-11 | A method for protecting tuyères for refining a molten iron |
DE8383304012T DE3375731D1 (en) | 1982-07-12 | 1983-07-11 | A method for protecting tuyeres for refining a molten iron |
CA000432147A CA1200383A (en) | 1982-07-12 | 1983-07-11 | Method for protecting tuyeres for refining a molten iron |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP12096282A JPS5913012A (en) | 1982-07-12 | 1982-07-12 | Method for protecting tuyere of blowpipe for refining molten iron |
Publications (1)
Publication Number | Publication Date |
---|---|
JPS5913012A true JPS5913012A (en) | 1984-01-23 |
Family
ID=14799303
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP12096282A Pending JPS5913012A (en) | 1982-07-12 | 1982-07-12 | Method for protecting tuyere of blowpipe for refining molten iron |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS5913012A (en) |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS55158211A (en) * | 1979-05-24 | 1980-12-09 | Sumitomo Metal Ind Ltd | Refining device of steel having gas circulating system |
JPS5693314A (en) * | 1979-12-26 | 1981-07-28 | Fujitsu Ltd | Ion injector |
-
1982
- 1982-07-12 JP JP12096282A patent/JPS5913012A/en active Pending
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS55158211A (en) * | 1979-05-24 | 1980-12-09 | Sumitomo Metal Ind Ltd | Refining device of steel having gas circulating system |
JPS5693314A (en) * | 1979-12-26 | 1981-07-28 | Fujitsu Ltd | Ion injector |
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