JPH072963B2 - Method of preventing slag foaming during hot metal pretreatment - Google Patents

Method of preventing slag foaming during hot metal pretreatment

Info

Publication number
JPH072963B2
JPH072963B2 JP18046589A JP18046589A JPH072963B2 JP H072963 B2 JPH072963 B2 JP H072963B2 JP 18046589 A JP18046589 A JP 18046589A JP 18046589 A JP18046589 A JP 18046589A JP H072963 B2 JPH072963 B2 JP H072963B2
Authority
JP
Japan
Prior art keywords
slag
hot metal
dephosphorization
cao
sio
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.)
Expired - Lifetime
Application number
JP18046589A
Other languages
Japanese (ja)
Other versions
JPH0347907A (en
Inventor
良二 辻野
英二 相田
成章 荻林
潤二 中島
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
Original Assignee
Nippon Steel Corp
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Filing date
Publication date
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Priority to JP18046589A priority Critical patent/JPH072963B2/en
Publication of JPH0347907A publication Critical patent/JPH0347907A/en
Publication of JPH072963B2 publication Critical patent/JPH072963B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

Description

【発明の詳細な説明】 (産業上の利用分野) 本発明は溶銑の予備精錬方法に関し、特に、予備精錬時
のスラグの噴出を防止したスラグフォーミング防止方法
に関する。
Description: TECHNICAL FIELD The present invention relates to a method for pre-refining hot metal, and more particularly to a method for preventing slag foaming which prevents spouting of slag during pre-refining.

(従来の技術) 従来、混銑車、溶銑鍋等(以下反応容器と称する)内で
脱りん、脱硫等の予備精錬を行う場合に反応容器上部か
ら反応容器内にランスを挿入してこのランスの尖端から
反応容器内の溶銑に酸素ガス、窒素ガス、固形酸化物、
石炭等の予備処理剤を吹込み、脱りん,脱硫等を行って
いる。この場合、脱炭反応で生成するCOガスにより容器
内のスラグが急激に発泡し、所謂スラグフォーミングを
起し、その一部が反応容器外に流出してスラグの損失が
生じ、又、スラグとともに溶銑も一部流出するので鉄歩
留が低下する。また、反応容器が混銑車の場合、流出し
たスラグが原因で、混銑車の移動が不可能となる危険性
もある。
(Prior Art) Conventionally, when performing pre-refining such as dephosphorization and desulfurization in a hot metal car, a hot metal ladle (hereinafter referred to as a reaction vessel), a lance is inserted from the upper portion of the reaction vessel into the reaction vessel. From the tip to the hot metal in the reaction vessel, oxygen gas, nitrogen gas, solid oxide,
Pre-treatment agents such as coal are blown to perform dephosphorization and desulfurization. In this case, the slag in the container is rapidly foamed by the CO gas generated in the decarburization reaction, so-called slag forming is caused, and a part of the slag flows out of the reaction container to cause slag loss. The iron yield decreases because some of the hot metal also flows out. In addition, if the reaction vessel is a tow truck, there is a risk that the tow truck cannot be moved due to the slag that has flowed out.

このような問題点を解決するため、特開昭60−165311号
公報に示すように、従来は、例えば高炉出銑口閉塞用ボ
タ等をスラグフォーミング抑制剤として添加してスラグ
の発泡を防止していた。
In order to solve such a problem, as shown in JP-A-60-165311, conventionally, for example, a blast furnace tap closing plug is added as a slag foaming inhibitor to prevent foaming of the slag. Was there.

(発明が解決しようとする課題) 従来、溶銑予備処理において、スラグフォーミングが発
生すると、一般的に何らかの抑制剤を投入する作業が行
われていたが、抑制剤を投入する実作業においては上記
抑制剤を反応容器内へ投入するたびに、予備精錬処理を
中断しなければならず、操業時間の延長になっていた。
又抑制剤投入が散発なため、抑制効果に永続性がなかっ
た。
(Problems to be Solved by the Invention) Conventionally, in the hot metal pretreatment, when slag foaming occurs, generally, an operation of adding some kind of inhibitor has been performed. The preliminary refining process had to be interrupted every time the agent was charged into the reaction vessel, which resulted in extension of the operation time.
Moreover, the inhibitory effect was not permanent because the addition of the inhibitor was sporadic.

本発明は、上記スラグフォーミングの発生を防止するべ
く、予め対策を採らんとするものである。
The present invention takes measures in advance to prevent the occurrence of the slag foaming.

(課題を解決するための手段) 本発明の要旨とするところは下記のとおりである。(Means for Solving the Problems) The gist of the present invention is as follows.

(1)脱りんまたは脱りん,脱硫の溶銑予備処理におい
て、下記に定義するCOガス発生速度(Vco)が0.2未満の
場合、下記に定義するフォーミング指数(F・I)を16
以下とするべくスラグ組成を制御することを特徴とする
溶銑予備処理時におけるスラグフォーミング防止方法。
(1) In the hot metal pretreatment of dephosphorization or dephosphorization, desulfurization, if the CO gas generation rate (Vco) defined below is less than 0.2, the forming index (FI) defined below is 16
A method for preventing slag foaming during hot metal pretreatment, which comprises controlling the slag composition as follows.

(2)混銑車での脱りんまたは脱りん,脱硫の溶銑予備処
理において、下記の定義するCOガス発生速度(Vco)が
0.2以上の場合、下記に定義するフォーミング指数(F
・I)を9以下とするべくスラグ組成を制御することを
特徴とする溶銑予備処理時におけるスラグフォーミング
防止方法。
(2) In the hot metal pretreatment for dephosphorization or dephosphorization and desulfurization in a hot metal truck, the CO gas generation rate (Vco) defined below is
When it is 0.2 or more, the forming index (F
A method for preventing slag foaming during hot metal pretreatment, which comprises controlling the slag composition so that I) is 9 or less.

記 F・I=−6{(CaO)/(SiO2)}+2{(Al2O3) +(TiO2)}+0.5(P2O5)+16.5 ((CaO)/(SiO2)≦3の場合) F・I=−0.5{(CaO)/(SiO2)} +2{(Al2O3)+(TiO2)}+0.5(P2O5) ((CaO)/(SiO2)>3の場合) Vco(Nm3/(t・p・min))=(Vo2)×{1−(Δ
〔P〕 ×10×80/60+Δ〔Si〕×10×32/28)}×22.4/32/NO2 ここでVo2:送酸速度(Nm3/(t・p・min),NO2:総
酸素原単位(Nm3/(t・p) 本発明の骨子はスラグ組成の制御またはCOガス発生速度
の制御を行ないスラグフォーミングの発生条件を回避し
てスラグフォーミングの発生を防止せんとするものであ
る。
Note F · I = −6 {(CaO) / (SiO 2 )} + 2 {(Al 2 O 3 ) + (TiO 2 )} + 0.5 (P 2 O 5 ) +16.5 ((CaO) / (SiO 2) for ≦ 3) F · I = -0.5 {(CaO) / (SiO 2)} +2 {(Al 2 O 3) + (TiO 2)} + 0.5 (P 2 O 5) ((CaO) / (SiO 2 )> 3) Vco (Nm 3 / (t · p · min)) = (Vo 2 ) × {1- (Δ
[P] × 10 × 80/60 + Δ [Si] × 10 × 32/28)} × 22.4 / 32 / NO 2 where Vo 2 : acid transfer rate (Nm 3 / (t · p · min), NO 2 : Total oxygen intensity (Nm 3 / (t · p)) The skeleton of the present invention is to prevent the occurrence of slag foaming by controlling the slag composition or the CO gas generation rate to avoid the slag foaming generation condition. Is.

(作用) スラグフォーミングは、気泡の発生速度と気泡の消滅速
度のバランスによって決まるが、従来、スラグフォーミ
ングに関しては、水溶液系の研究が多く、また高温融体
スラグに関してもCaO/SiO2≦1.0の脱珪処理に関するも
のがほとんどであり、脱りんまたは脱りん,脱硫の高塩
基度の領域の研究は少ない。そこで、本発明者らは脱り
んまたは脱りん,脱硫に関しラボ実験を行ない、気泡の
消滅速度、すなわち気泡の安定性を支配する要因につい
ての検討を行ない、フォーミング指数(F・I)を設定
した。さらに実機スラグフォーミングの発生がフォーミ
ング指数(F・I)およびCOガスの発生速度とどういう
関係にあるかについて調査検討した。
(Function) Slag foaming is determined by the balance between the bubble generation rate and the bubble disappearance rate. Conventionally, there have been many studies on aqueous solution systems for slag foaming, and CaO / SiO 2 ≦ 1.0 for high temperature molten slag. Most of them are related to desiliconization treatment, and there are few studies on the high basicity region of dephosphorization or dephosphorization / desulfurization. Therefore, the present inventors conducted a laboratory experiment on dephosphorization or dephosphorization and desulfurization, studied the factors that govern the bubble disappearance rate, that is, the stability of the bubbles, and set the forming index (FI). . Furthermore, we investigated and examined how the occurrence of actual slag foaming is related to the forming index (FI) and the generation rate of CO gas.

10kg高周波溶解炉にて炭素飽和溶銑(1kg)中にCaO−Si
O2−Fe2O3−CaF2−P2O5系のスラグを生成するように試
薬(80g)を混合して添加し、スラグフォーミングを発
生させ、スラグフォーミングの高さを測定した。その結
果スラグフォーミングの高さは、第1図に示すように
(CaO)/(SiO2)の依存性が大きく、その他第2図、
第3図に示すように(Al2O3),(TiO2)の成分の影響
が大きいことがわかった。
CaO-Si in saturated carbon hot metal (1 kg) in a 10 kg high frequency melting furnace
A reagent (80 g) was mixed and added so as to generate a slag of O 2 —Fe 2 O 3 —CaF 2 —P 2 O 5 system, slag foaming was generated, and the height of the slag foaming was measured. As a result, the height of the slag foaming is highly dependent on (CaO) / (SiO 2 ) as shown in FIG.
As shown in Fig. 3 , it was found that the influence of the components (Al 2 O 3 ) and (TiO 2 ) was great.

第2図、第3図の結果は、溶銑脱りんの基本組成である
(CaO)/(SiO2)が3.0での結果であるが、(CaO)/
(SiO2)=1.0〜7.0まで(Al2O3),(TiO2)の影響が
みられた。また(P2O5)の影響は(Al2O3),(TiO2)
に比し影響は比較的小さいことがわかった。
The results shown in Figs. 2 and 3 are the results when the basic composition of hot metal dephosphorization (CaO) / (SiO 2 ) is 3.0, but (CaO) /
(SiO 2 ) = 1.0 to 7.0, the effects of (Al 2 O 3 ) and (TiO 2 ) were observed. Moreover, the influence of (P 2 O 5 ) is (Al 2 O 3 ), (TiO 2 ).
It was found that the effect was relatively small compared to.

以上の結果から、スラグの物性の影響を通してスラグフ
ォーミングの高さに影響を及ぼす因子の統一指標として
フォーミング指数(F・I)を次のように設定すること
ができた。
From the above results, the forming index (FI) can be set as follows as a unified index of the factors that influence the height of slag forming through the influence of the physical properties of slag.

すなわち、(CaO)/(SiO2),(Al2O3),(TiO2)の
影響を第1図、第2図、第3図から求め、溶銑予備処理
スラグでは(Al2O3),(TiO2)とも含有率が通常20%
以下であるため、第2図、第3図の20%以下の濃度域を
直線近似して、各要因を一次近似でフォミング指数を求
めた。
That is, the effects of (CaO) / (SiO 2 ), (Al 2 O 3 ), and (TiO 2 ) were obtained from FIGS. 1, 2, and 3, and in the hot metal pretreatment slag, (Al 2 O 3 ) , (TiO 2 ) content is usually 20%
Since it is below, the concentration range of 20% or less in FIGS. 2 and 3 was linearly approximated, and each factor was obtained by linear approximation to obtain the Foming index.

F・I=−6{(CaO)/(SiO2)}+2{(Al2O3) +(TiO2)}+0.5(P2O5)+16.5 ((CaO)/(SiO2)≦3の場合) F・I=−0.5{(CaO)/(SiO2)} +2{(Al2O3)+(TiO2)}+0.5(P2O5) ((CaO)/(SiO2)>3の場合) 実機でのスラグフォーミングの発生はフォーミング指数
のスラグ物性および、COガス発生速度の影響を受け、ス
ラグフォーミングによる精錬容器からのスラグの流出は
さらに精錬容器内の湯面上部空間の大きさに依存する
が、脱りんまたは脱りん,脱硫時に発生するフォーミン
グスラグの実態を調査したところ、0.1mm以下の微細な
気泡が分散した泡がその主体を成しており、泡の初期ス
ラグに対する膨張率は5〜10倍あることがわかった。
F · I = -6 {(CaO ) / (SiO 2)} + 2 {(Al 2 O 3) + (TiO 2)} + 0.5 (P 2 O 5) +16.5 ((CaO) / (SiO 2 ) for ≦ 3) F · I = -0.5 {(CaO) / (SiO 2)} +2 {(Al 2 O 3) + (TiO 2)} + 0.5 (P 2 O 5) ((CaO) / (In the case of SiO 2 > 3) The generation of slag foaming in an actual machine is affected by the slag physical properties of the forming index and the CO gas generation rate, and the slag outflow from the refining container by slag foaming is further caused Although it depends on the size of the space above the surface, we investigated the actual state of forming slag that occurs during dephosphorization or dephosphorization and desulfurization. It was found that the expansion coefficient of the foam with respect to the initial slag was 5 to 10 times.

したがって湯面上部空間の概して小さい混銑車の場合を
除き、F・Iをある値以下に確保できればCOガス発生速
度にかかわらず、スラグフォーミングによるスラグの流
出を防止できることがわかった。
Therefore, it was found that, except in the case of a tow car with a generally small space above the molten metal surface, if FI can be secured below a certain value, slag outflow due to slag foaming can be prevented regardless of the CO gas generation rate.

第4図は310T混銑車における脱りん処理でのスラグフォ
ーミングによるスラグ流出の有無とフォーミング指数
(F・I)、CO発生速度(Vco)との関係を示した図で
ある。
FIG. 4 is a diagram showing the relationship between the presence or absence of slag outflow due to slag forming in the dephosphorization treatment of a 310 T hot metal truck, the forming index (FI), and the CO generation rate (Vco).

第4図に示すようにCOガス発生速度(Vco)が0.2(Nm3/
t・p・min)未満の場合、F・Iが16以下でスラグフォ
ーミングによるスラグの流出はなかったが、COガス発生
速度(Vco)が0.2以上の場合、フォーミング発生による
スラグ流出傾向は増幅され、F・Iを9以下に管理する
必要があることがわかった。
As shown in Fig. 4, the CO gas generation rate (Vco) is 0.2 (Nm 3 /
When the CO gas generation rate (Vco) is 0.2 or more, the slag outflow tendency due to foaming is amplified when FI is 16 or less and there is no slag outflow due to slag foaming. , FI was found to need to be managed to 9 or less.

なお、この傾向はCOガスの発生速度を溶銑重量当たりと
しているので、混銑車の容量によって変わらない。
Note that this tendency is based on the CO gas generation rate per weight of hot metal, so it does not change depending on the capacity of the hot metal truck.

COガス発生速度(Vco(Nm3/(t・p・min))は、各
時期での溶銑サンプルの分析結果からP,Siの減少分を求
め、それらの酸化に用いられる酸素分を差し引いて次式
にて求められる。
The CO gas generation rate (Vco (Nm 3 / (t · p · min)) was calculated by subtracting the oxygen content used for oxidation of P and Si from the analysis results of the hot metal sample at each time. It is calculated by the following formula.

Vco(Nm3/(t・p・min))=(Vo2)×{1−(Δ
〔P〕 ×10×80/60+Δ〔Si〕×10×32/28)}×22.4/32/NO2 上記のようなF・I範囲に制御するためには、脱りん処
理前に生石灰を添加することあるいは、生石灰の添加速
度を制御すること、脱りん処理前の脱珪スラグを十分に
除去すること等の(CaO)/(SiO2)制御、さらに、通
常1〜5%の微量成分である(Al2O3),(TiO2)に関
しては、脱珪スラグの十分な除去、耐火物の管理等が重
要である。
Vco (Nm 3 / (tp) min) = (Vo 2 ) × {1- (Δ
[P] × 10 × 80/60 + Δ [Si] × 10 × 32/28)} × 22.4 / 32 / NO 2 In order to control the F / I range as described above, quicklime is added before the dephosphorization treatment. Or to control the addition rate of quick lime, (CaO) / (SiO 2 ) control such as sufficient removal of desiliconization slag before dephosphorization treatment, and usually with a trace amount of 1-5% For (Al 2 O 3 ) and (TiO 2 ), it is important to sufficiently remove desiliconization slag and manage refractories.

(実施例) 実施例1 300t取鍋にてCaO−CaF2系フラックス、鉄鉱石をインジ
ェクションによって添加し、さらに気体酸素を総酸素量
の20%として上吹し、脱りん処理を行なった。
(Example) Example 1 CaO-CaF 2 based flux at 300t ladle, iron ore was added by injection, further upward blown gaseous oxygen as 20% of the total oxygen content was subjected to dephosphorization process.

本処理の場合、処理前にスラグを採取し分析したとこ
ろ、表1に示すような組成であった。この場合F・Iは
25.2であり処理開始とともにスラグフォーミングが発生
し、スラグの流出がみられたがCaO−CaF2系フラックス
を高速で吹込むことによって3分後にスラグフォーミン
グは抑制され、スラグの流出はなくなった。このとき採
取されたスラグの組成は表2に示す通りであり、F・I
は12.0になっていた。以後、スラグフォーミングは抑制
されスラグの流出はみられず、脱りん処理をすることが
できた。
In the case of this treatment, slag was collected and analyzed before the treatment, and the composition was as shown in Table 1. In this case, FI
It was 25.2, and slag foaming occurred with the start of treatment, and slag outflow was observed, but slag foaming was suppressed after 3 minutes by blowing CaO-CaF 2 system flux at high speed, and slag outflow disappeared. The composition of the slag collected at this time is as shown in Table 2.
Was 12.0. After that, slag foaming was suppressed, slag outflow was not observed, and dephosphorization treatment was possible.

(実施例2) 310t混銑車にてCaO−CaF2−CaCl2系フラックス、Mn鉱石
のインジェクション、気体酸素の上吹にて、脱りん,脱
硫処理を行なった。
(Example 2) 310t torpedo car in CaO-CaF 2 -CaCl 2 based flux, Mn ore injection at blow on the gaseous oxygen was performed dephosphorization, desulfurization process.

処理前のスラグ組成は表3に示す通りでF・Iは11.3で
ありスラグフォーミングによるスラグの流出はみられな
かったが、処理とともに総酸素添加速度を増加していく
と、スラグの流出がみられた。この時点でのスラグ組成
を表4に示すが、F・Iは9.8であり、また計算上のVco
は、0.35であった。そこで処理を一次中断し、CaOを高
速度で吹込み、スラグフォーミングを抑制した。この時
点でのスラグ組成は表5に示す通りであり、F・Iは、
6.3となりこれ以降Vcoは0.3〜0.5の範囲で操業を行なっ
たが、スラグフォーミングによるスラグの流出はみられ
なかった。
The slag composition before treatment is as shown in Table 3 and FI was 11.3, and no slag outflow due to slag foaming was observed, but when the total oxygen addition rate was increased with the treatment, slag outflow was observed. Was given. The slag composition at this point is shown in Table 4. The FI is 9.8, and the calculated Vco
Was 0.35. Therefore, the process was temporarily interrupted and CaO was blown at a high speed to suppress slag foaming. The slag composition at this point is as shown in Table 5, and FI is
It became 6.3, and Vco operated from 0.3 to 0.5 after this, but no slag outflow due to slag forming was observed.

(発明の効果) 本発明により脱りんまたは脱りん,脱硫処理における、
スラグフォーミングの発生によるスラグ流出が防止でき
るので、操業の中断、鉄損失といった従来の問題点を解
決することができ、安定操業、コストダウンを達成し得
るという効果が奏される。
(Effects of the Invention) In the dephosphorization or dephosphorization / desulfurization treatment according to the present invention,
Since the outflow of slag due to the occurrence of slag foaming can be prevented, it is possible to solve the conventional problems such as interruption of operation and iron loss, and it is possible to achieve stable operation and cost reduction.

【図面の簡単な説明】[Brief description of drawings]

第1図,第2図,第3図は10kg高周波溶解炉でのスラグ
フォーミング実験の結果であり、第1図はスラグフォー
ミング高さ(最大)と((CaO)/(SiO2))の関係、
第2図はスラグフォーミング高さ(最大)と(Al2O3)
の関係、第3図は、スラグフォーミング高さ(最大)と
(TiO2)の関係を示す図、第4図は310t混銑車における
脱りん処理でのスラグフォーミングによるスラグ流出の
有無とフォーミング指数(F・I),CO発生速度(Vco)
との関係を示す図である。
Figures 1, 2 and 3 show the results of slag forming experiments in a 10kg high frequency melting furnace. Figure 1 shows the relationship between the slag forming height (maximum) and ((CaO) / (SiO 2 )). ,
Figure 2 shows the slag forming height (maximum) and (Al 2 O 3 ).
Fig. 3 shows the relationship between the slag foaming height (maximum) and (TiO 2 ), and Fig. 4 shows the presence or absence of slag outflow and the forming index ( FI), CO generation rate (Vco)
It is a figure which shows the relationship with.

Claims (2)

【特許請求の範囲】[Claims] 【請求項1】脱りんまたは脱りん,脱硫の溶銑予備処理
において、下記に定義するCOガス発生速度(Vco)が0.2
未満の場合、下記に定義するフォーミング指数(F・
I)を16以下とするべくスラグ組成を制御することを特
徴とする溶銑予備処理時におけるスラグフォーミング防
止方法。
1. A CO gas generation rate (Vco) defined below is 0.2 in the hot metal pretreatment of dephosphorization or dephosphorization and desulfurization.
If less than, forming index (F ·
A method for preventing slag foaming during hot metal pretreatment, which comprises controlling the slag composition so that I) is 16 or less.
【請求項2】混銑車での脱りんまたは脱りん,脱硫の溶
銑予備処理において、下記に定義するCOガス発生速度
(Vco)が0.2以上の場合、下記に定義するフォーミング
指数(F・I)を9以下とするべくスラグ組成を制御す
ることを特徴とする溶銑予備処理時におけるスラグフォ
ーミング防止方法。 記 F・I=−6{(CaO)/(SiO2)}+2{(Al2O3) +(TiO2)}+0.5(P2O5)+16.5 ((CaO)/(SiO2)≦3の場合) F・I=−0.5{(CaO)/(SiO2)} +2{(Al2O3)+(TiO2)}+0.5(P2O5) ((CaO)/(SiO2)>3の場合) Vco(Nm3/(t・p・min))=(Vo2)×{1−(Δ
〔P〕 ×10×80/60+Δ〔Si〕×10×32/28)}×22.4/32/NO2 ここでVo2:送酸速度(Nm3/(t・p・min),NO2:総
酸素原単位(Nm3/(t・p)
2. When the CO gas generation rate (Vco) defined below is 0.2 or more in the hot metal pretreatment of dephosphorization or dephosphorization and desulfurization with a mixed pig wheel, the forming index (FI) defined below is used. A method for preventing slag foaming during hot metal pretreatment, which comprises controlling the slag composition to be 9 or less. Note F · I = −6 {(CaO) / (SiO 2 )} + 2 {(Al 2 O 3 ) + (TiO 2 )} + 0.5 (P 2 O 5 ) +16.5 ((CaO) / (SiO 2) for ≦ 3) F · I = -0.5 {(CaO) / (SiO 2)} +2 {(Al 2 O 3) + (TiO 2)} + 0.5 (P 2 O 5) ((CaO) / (SiO 2 )> 3) Vco (Nm 3 / (t · p · min)) = (Vo 2 ) × {1- (Δ
[P] × 10 × 80/60 + Δ [Si] × 10 × 32/28)} × 22.4 / 32 / NO 2 where Vo 2 : acid transfer rate (Nm 3 / (t · p · min), NO 2 : Total oxygen intensity (Nm 3 / (tp))
JP18046589A 1989-07-14 1989-07-14 Method of preventing slag foaming during hot metal pretreatment Expired - Lifetime JPH072963B2 (en)

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JPH072963B2 true JPH072963B2 (en) 1995-01-18

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