JP3547246B2 - Lance for molten iron refining and molten iron refining method - Google Patents

Description

なおここでいう「溶鉄精錬用ランス」は、ステンレス鋼を含む溶鋼の精錬に用いても良く、精錬設備としも転炉、電気炉、真空脱ガス装置などいかなるものに用いても良い。
【００１３】
【発明の実施の形態】
本発明の実施の形態を図１に従って説明する。
図１は、ノズルの入り側絶対圧Ｐ_Ｏ が４．５ ｋｇｆ／ｃｍ^２ のときの「ノズルの出口径ｄ_ｅ とスロート径ｄ_ｔ の比ｄ_ｅ ／ｄ_ｔ 」と「入り側絶対圧Ｐ_Ｏ と適正膨張絶対圧Ｐ_Ｏｐの比Ｐ_Ｏ ／Ｐ_Ｏｐ」の関係および「ノズルの出口径ｄ_ｅ とスロート径ｄ_ｔ の比ｄ_ｅ ／ｄ_ｔ 」と「噴流進行方向に垂直な断面における噴流中心軸上流速Ｕ_ｍａｘ と当該スロート径でノズルの入り側絶対圧Ｐ_Ｏ で適正膨張するように出口径を定めたノズルの噴流中心軸上流速Ｕ_ｍａｘｐの比Ｕ_ｍａｘ ／Ｕ_ｍａｘｐ」の関係を示す図である。
【００１４】
まず、図１の縦軸（２種類）および横軸について説明する。（ａ）図の縦軸Ｐ_Ｏ ／Ｐ_Ｏｐは一般的な物理量であり、ノズルの適正膨張絶対圧（Ｐ_Ｏｐ（ｋｇｆ／ｃｍ^２ ））とノズルの入り側絶対圧Ｐ_Ｏ との比である。Ｐ_Ｏ およびＰ_Ｏｐはいずれも下記（６） および（６） ′式によって表される数値であり、ノズルのスロート径ｄ_ｔ （ｍｍ）が決まれば、送酸速度Ｆ_Ｏ２あるいはＦ_Ｏ２ｐ （適正膨張絶対圧の時の送酸速度）により一義的に決まる。縦軸をこれらの比Ｐ_Ｏ ／Ｐ_Ｏｐとしたのは操業時の送酸速度の絶対値（精錬炉の操業規模）に依存せず、適正膨張条件との乖離度合いを表現するためである。
【００１５】
Ｐ_Ｏ ＝Ｆ_Ｏ２／（０．４５６×ｄ_ｔ ^２ ） …（６）
Ｐ_Ｏ ＝Ｆ_Ｏ２ｐ ／（０．４５６×ｄ_ｔ ^２ ） …（６） ′
次に（ｂ）図の縦軸のＵ_ｍａｘ ／Ｕ_ｍａｘｐとは、ノズル下端から噴出するガス噴流の溶鉄浴面への衝突時の噴流流速Ｕ（噴流進行方向に垂直な断面における噴流中心軸上流速であり、Ｕは流速分布を持つ）に関して、そのうちの最大値をＵ_ｍａｘ と定義し、同じスロート径でノズルの入り側絶対圧Ｐ_Ｏ で適正膨張するように出口径を定めたノズルのＵ_ｍａｘ をＵ_ｍａｘｐと定義する。この時、Ｆ_Ｏ２の絶対値によらない値としてそれらの比で図示している。また、これらのＵ_ｍａｘ やＵ_ｍａｘｐは本発明者がピトー管を用いて行った噴流流速測定結果を基に算出した値を用いている。
【００１６】
ここで、或る送酸速度Ｆ_Ｏ２に対して、ノズルのスロート径が一定ｄ_ｔ の条件下で、すなわちノズルの入り側絶対圧Ｐ_Ｏ が一定の条件下で、（１） 式および（２） 式、あるいは（１） 式および（３） 式のいずれかの条件を満たすような出口径ｄ_ｅ のノズルを使用すると、図１に示すようにＵ_ｍａｘ を大幅に低減できる。
またこのことから、或るノズルの出口径ｄ_ｅ とスロート径ｄ_ｔ の比ｄ_ｅ ／ｄ_ｔ で設計された既存のランスに対して、（１） 式および（４） 式、あるいは（１） 式および（５） 式のいずれかの条件を満たすようなノズルの入り側絶対圧Ｐ_Ｏ （実操業では、（６） あるいは（６） ′式からＦ_Ｏ２に置き換えられる）で操業することによっても、同様にＵ_ｍａｘ を大幅に低減することができる。
【００１７】
また、図１に示すように、請求項１に対応する本発明のより望ましい範囲として、前記(1) 式および下記(7) 式、あるいは前記(1) 式および下記(8) 式のいずれかの条件を満たすランスを使用することにより、Ｕ_max をさらに抑制できて、ダスト発生量低減効果を高めることができる。
Ｐ_O ／１．８≦Ｐ_Op≦Ｐ_O ／１．３ …(7)
Ｐ_O ／０．７≦Ｐ_Op …(8)
同様に、請求項３に対応する本発明のより望ましい範囲として、前記(1) 式および下記(9) 式、あるいは前記(1) 式および下記(10)式のいずれかの条件を満たすようなノズルの入り側絶対圧Ｐ_O （実操業では、(6) あるいは(6) ′式からＦ_O2に置き換えられる）で操業することによりＵ_max をさらに抑制できて、ダスト発生量低減効果を高めることができる。
【００１８】

本発明の請求の範囲をより具体的に示すために、該ｄ_ｅ ／ｄ_ｔ とノズル入り側の絶対圧Ｐ_ｏ の関係の一例を示したものが図４である。本発明の範囲は、操業時の出口部雰囲気絶対圧Ｐ_ｅ 、および送酸速度Ｆ_Ｏ２あるいはノズルの入り側絶対圧Ｐ_ｏ の値によりｄ_ｅ ／ｄ_ｔ およびＰ_Ｏｐの取るべき絶対値はいろいろな値になるが、それぞれが互いに請求項中の（１）〜（５）式の関係を満足することにより、ランス下端〜溶鉄湯面間距離および送酸速度を同一にしたままで、溶鉄湯面における最大噴流流速を従来の値より小さくすることができるというものである。図４では一例として、（１）式中のＰ_ｅ を通常の転炉の場合の大気圧１．０３３ｋｇｆ ／ｃｍ^２ とし、（２）式（Ｐ_ｏ ／２．０≦Ｐ_Ｏｐ≦Ｐ_ｏ ／１．２）を、Ｐ_ｏ ／２．０＝Ｐ_Ｏｐ （２）′ と、Ｐ_Ｏｐ＝Ｐ_ｏ ／１．２ （２）″ の２つの式に分割し、それぞれを（１）式中に代入して（１）式をｄ_ｅ ／ｄ_ｔ とＰ_ｏ の２つの関係式としてそれぞれの曲線を図示してある。（３）式についても同様である。つまり、本発明のＰ_ｅ ＝１．０３３ｋｇｆ ／ｃｍ^２ の場合については、図４中の斜線で示されるＰ_ｏ ／Ｐ_Ｏｐ＝０．８の曲線よりｄ_ｅ ／ｄ_ｔ が大なる範囲およびＰ_ｏ ／Ｐ_Ｏｐ＝１．２〜２．０の領域であって、この領域に存在する請求の範囲のｄ_ｅ ／ｄ_ｔ とＰ_ｏ との関係は１つではない。実際には、操業で使用するＰ_ｏ の範囲は約３〜２５ｋｇｆ ／ｃｍ^２ であって、これらに対応するｄ_ｅ ／ｄ_ｔ は約１以上の範囲である。ｄ_ｅ ／ｄ_ｔ 決定の手順としてはＰ_ｏ を決定してこの図４のような関係図を求めて、例えばＰ_ｏ を（６）式から操業時のＦ_Ｏ２によって５．０ｋｇｆ ／ｃｍ^２ と決まれば、ｄ_ｅ ／ｄ_ｔ の最適領域は約１．０２〜１．１１及び１．２１以上の２つの領域となり、Ｐ_ｏ を１５．０ｋｇｆ ／ｃｍ^２ と決めればｄ_ｅ ／ｄ_ｔ の最適領域は約１．２７〜１．４７及び１．６５以上の２つの領域となるわけである。これらの領域の中から他の条件、例えばランス本体形状あるいはランス冷却方式などからｄ_ｅ ／ｄ_ｔ を更に絞り込むのである。また、この図４の横軸Ｐ_ｏ ＝４．５ｋｇｆ ／ｃｍ^２ について、Ｐ_ｏ ／Ｐ_Ｏｐとｄ_ｅ ／ｄ_ｔ との関係に置換したものが図１である。
【００１９】
【実施例】
内径約１．２ｍの上底吹き転炉を用いて、６ｔの溶鉄を装入し、Ａ，Ｂ，Ｃ，Ｄ，Ｅ，Ｆの６種類のランスについて、それぞれランス先端−溶鉄静止湯面間距離を２段階に変更し、酸素ガス流量１２００Ｎｍ^３ ／ｈ、ノズル入り側絶対圧４．５ ｋｇｆ／ｃｍ^２ 一定で計１２水準の脱炭試験を行った。いずれの水準でも底吹きガスとして窒素３００Ｎｍ^３ ／ｈを用いた。また、精錬開始直後に塩基度が約３．５となるように石灰を１３０ｋｇ投入した。各ランスの設計値を表１に、試験条件および試験結果を表２に示す。また、本発明例のランスのうち、Ｅ，Ｆはより望ましい範囲に該当する。
【００２０】
【表１】

【００２１】
【表２】

【００２２】
本実施例の結果について説明する。本実施例は実炉ベースの６ｔ転炉によって、ランス条件（表１）における実操業水準としてランス高さを２水準（６００，１０００ｍｍ）、としたものである。すなわち、比較例Ａと比べて本発明のＢ〜Ｆでは、ダスト発生量および二次燃焼率がどのように改善されるかを定量的に表わしたものである。
【００２３】
従来方法においては、ダストを減らすと二次燃焼率が上昇していたが、本発明Ｂ〜Ｆでは、比較例Ａをベースに、同一ランス高さのもとではダストが減少し、かつ二次燃焼率（ＰＣＲ）が比較例Ａより高くならない。なお、耐火物損耗程度は前記ＰＣＲに比例するので、本実施例では、ダスト発生量と一次的関係を有する前記二次燃焼率で整理した。
【００２４】
【発明の効果】
本発明により、炉内耐火物への悪影響や二次燃焼率の上昇を生じることなく、ダスト発生量を低減することが可能となる。
【図面の簡単な説明】
【図１】本発明に係るノズルの入り側絶対圧Ｐ_Ｏ が４．５ ｋｇｆ／ｃｍ^２ の時の（ａ）ノズルの出口径ｄ_ｅ とスロート径ｄ_ｔ の比ｄ_ｅ ／ｄ_ｔ と入り側絶対圧Ｐ_Ｏ と適正膨張絶対圧Ｐ_Ｏｐの比Ｐ_Ｏ ／Ｐ_Ｏｐの関係、（ｂ）ノズルの出口径ｄ_ｅ とスロート径ｄ_ｔ の比ｄ_ｅ ／ｄ_ｔ と噴流進行方向に垂直な断面における噴流中心軸上流速Ｕ_ｍａｘ と当該スロート径でノズルの入り側絶対圧Ｐ_Ｏ で適正膨張するように出口径を定めたノズルの噴流中心軸上流速Ｕ_ｍａｘｐの比Ｕ_ｍａｘ ／Ｕ_ｍａｘｐの関係を示す図である。
【図２】本発明の実施の態様を示す図で、（ａ）本発明の実施の態様を示す概略図、（ｂ）ランス先端部の態様を示す概略図である。
【図３】実施例の各水準の試験結果で、二次燃焼率とダスト発生量の関係を示す図である。
【図４】本発明の請求の範囲２および４を前記ｄ_ｅ ／ｄ_ｔ と前記Ｐ_Ｏ の関係によってより具体的に示す図である。
【符号の説明】
１…精錬容器
２…ランス
３…溶鉄
４…ランス先端−溶鉄静止湯面間距離
５…ランスノズル
６…スロート径
７…出口径
８…酸素ガス流[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a lance structure and a molten iron refining method in molten iron refining using a lance.
[0002]
[Prior art]
The lance used for refining molten iron in a smelting vessel such as a converter uses a high-efficiency jet motion to control the inlet side pressure of the nozzle provided at the lower end of the lance in order to promote agitation of the steel bath by the oxygen gas jet. A multi-hole medium-sized nozzle that converts energy is generally used, and refining is performed within the range of the appropriate expansion pressure of the nozzle (Iron and Steel Handbook, Third Edition, Volume II, edited by The Iron and Steel Institute of Japan, 1982, 468). However, in this case, since the kinetic energy of the jet is high (hard blow), dust is generated, and the adverse effect of reducing the iron yield cannot be avoided. Therefore, in order to suppress the generation of such dust, the kinetic energy of the jet is reduced by increasing the distance between the tip of the lance and the molten metal surface of the molten iron in order to reduce the kinetic energy of the jet (soft blow). Attempts have been made to increase the throat diameter of the nozzle to reduce the pressure on the inlet side of the nozzle or to use a porous nozzle to promote the attenuation of the jet. However, in any method, the amount of space gas entrained in the furnace increases, and the secondary combustion rate increases, so that the decarbonation efficiency decreases and the refractory in the furnace is damaged by the combustion heat of the secondary combustion. There are difficulties. That is, in the conventional method, "dust generation" and "increase in the secondary combustion rate" are inextricably linked, and it is impossible to avoid both problems at the same time.
[0003]
The “nozzle provided at the lower end of the lance” here is a pipe (medium-thin nozzle) whose upper end is connected to the gas supply pipe, has a constriction on a vertical cross section, and opens at the lower end of the lance. The opening at the lower end of the nozzle refers to a structure called a hole. Also, the throat diameter refers to the inner diameter of the narrowest part of this conduit.
In addition, for the purpose of reducing the amount of dust generated, a lance has been proposed that optimizes the arrangement and inclination angle of the nozzle to reduce the overlapping rate of the cavity (depression on the molten metal surface) formed by the oxygen jet. (For example, JP-B-62-46611 and JP-A-6-57320). In these, the technical idea is to reduce the overlapping range of the cavity, which is considered to be one of the causes of dust generation, by dispersing the jet direction under a constant total kinetic energy of the jet. However, even in these cases, since the angle of inclination of the nozzle is widened, the distance between the furnace wall and the jet may be so small that the refractory in the furnace may be worn. For this reason, even if dust resulting from the overlap of the cavities can be reduced, the total kinetic energy of the jet does not change, so that the amount of dust generated due to kinetic energy cannot be reduced. After all, neither of the two problems described above can be solved.
[0004]
[Problems to be solved by the invention]
The present invention provides a two-sided problem in which the above-mentioned solutions are inconsistent, that is, a problem of a decrease in decarbonation efficiency due to an increase in the secondary combustion rate, a problem of erosion of refractories in a furnace, and generation of dust. The present invention provides an innovative lance for refining molten iron and a method for refining molten iron that can simultaneously solve the two problems described above.
[0005]
[Means for Solving the Problems]
The present inventor has confirmed through detailed experiments that there is a positive correlation between the amount of dust generated and the speed at which the gas jet reaches the molten iron surface (jet flow velocity = U). At that time, under a constant absolute pressure of the atmosphere in the refining furnace (= P _e ), the gas injection flow rate (in the case of oxygen gas, the acid supply rate (= FO ₂ ) in the case of oxygen gas) is set to the absolute value on the inlet side of the nozzle. The pressure (= P _O ) and the throat diameter of the nozzle (= _dt ) are uniquely determined under the same conditions. On the other hand, the jet velocity U is also under the same conditions is P _O and d _t, outlet diameter (= d _e) focused on the phenomenon that varies with the expansion of the jet over the throat to the outlet by changing the d _e In other words, the present invention has been invented as an industrial means capable of changing the state, that is, the loss amount of the kinetic energy of the jet (the degree of attenuation of the jet flow velocity U).
[0006]
That, F _O2, d _t, and the lance tip - molten iron stationary molten steel surface distance (= LG) even in the case of the same, conventionally obtained attenuation degree of the total kinetic energy of the jet which could not have been achieved (soft blow of) breakthrough conditions, which means he has to finding that there is a ratio of the optimum _{d e} and _{d t (= d e / d} t). Furthermore, even if attenuate the jet flow velocity U by changing the _{d e,} other conditions _{(P O,} the number of nozzles (= n), _{d t,} arrangement and positional relation of the nozzles, the inclination angle of the nozzle, LG) is identical In this case, it was found that the secondary combustion rate in the refining furnace was not affected, in other words, the jet flow velocity U could be changed without affecting the secondary combustion rate.
[0007]
Based on the above two new findings, molten iron smelting having a structure based on a completely new lance design condition that can avoid an increase in the secondary combustion rate while attenuating the jet flow velocity U to reduce the amount of dust generated Lance and a method of refining molten iron using the lance have been invented.
That is, the gist of the present invention is as follows.
[0009]
( 1 ) A lance for refining molten iron used for refining molten iron while supplying oxygen gas, wherein an outlet diameter (d _e (cm)) of at least one nozzle of a nozzle provided at the tip of the lance and a throat diameter (d _e (cm)) the ratio d _e / d _t the outlet atmosphere absolute pressure of the nozzle between ^{_{(P e (kgf / cm 2}} )), and proper inflation absolute pressure (P _Op nozzle (kgf / cm ² )) And P _Op in relational expression (1) is limited to the range of the following expression (2) or (3) by the ratio to the absolute pressure P _O on the inlet side of the nozzle. A lance for smelting molten iron, characterized by that:
[0010]
d _e / d _t = 0.509 ・ (P _e / P _Op ) ^-5/14・ ｛1- (P _e / P _Op ) ^2/7 ｝ ^-1 / ⁴ … (1)
_{P o /2.0≦ P op ≦ P o} /1.2 ... (2)
P _O /0.8≦P _op … (3)
( 2 ) A molten iron refining method characterized in that the molten iron refining lance described in (1) minimizes a dust generation rate with respect to a distance between a specific lance lower end and a molten metal surface when the total gas supply speed is maximized.
[0011]
(3) lance tip is provided with at least one of the outlet diameter of the nozzles of the nozzle (d _e (cm)) and the throat diameter (d _t (cm)) and the ratio d _e / d _t the nozzle outlet Atmosphere Using the lance for molten iron refining determined from the relational expression (1) between the absolute pressure (P _e (kgf / cm ² )) and the proper expansion absolute pressure of the nozzle (P _Op (kgf / cm ² )), and using the nozzle The molten iron refining method characterized by using the ratio of the absolute pressures P _O and P _Op on the entry side within the range of the following formula (4) or (5).
[0012]

The "lance for refining molten iron" used herein may be used for refining molten steel including stainless steel, and may be used for any refining equipment such as a converter, an electric furnace, a vacuum degassing device, and the like.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIG.
1, the "inlet side absolute pressure P" ratio _d e / _{d t} of output nozzle diameter _{d e} and the throat diameter _{d t} "when the entrance side absolute pressure _{P O} of the nozzles 4.5 kgf / cm ² jet in the cross section perpendicular _O and proper inflation absolute pressure relationship _P ratio _P O _{/ P Op} of _Op "and" specific _d e / _{d t} of exit diameter _{d e} and the throat diameter _{d t} of the nozzle "to" jet traveling direction the ratio _U max _{/ U maxp} "relationship of the central axis upstream speed _{U max} and jet central axis upstream speed _{U maxp} nozzle that defines the outlet diameter to properly inflated in the throat diameter at the inlet side absolute pressure _{P O} of the nozzle FIG.
[0014]
First, the vertical axis (two types) and the horizontal axis in FIG. 1 will be described. (A) The vertical axis P _O / P _Op in the figure is a general physical quantity, and is the ratio between the appropriate absolute expansion pressure (P _Op (kgf / cm ² )) of the nozzle and the absolute pressure P _O on the inlet side of the nozzle. . Both P _O and P _Op are numerical values represented by the following equations (6) and (6) ′, and when the throat diameter _dt (mm) of the nozzle is determined, the _{acid supply} rate F _O2 or F _O2p (proper expansion) It is uniquely determined by the acid transfer rate at absolute pressure). The vertical axis is set to these ratios P _O / P _Op in order to express the degree of deviation from the appropriate expansion conditions without depending on the absolute value of the acid supply rate during operation (the operation scale of the refining furnace).
[0015]
P _O = F _O2 / (0.456 × _dt ² ) (6)
^{_{P O = F O2p /(0.456×d t 2}} ) ... (6) '
Then A U _{max /} U _maxp the longitudinal axis of the (b) diagram, the jet flow velocity U at the time of collision of the molten iron bath surface of the gas jet to be ejected from the nozzle lower end (on the jet central axis in a cross section perpendicular to the jet direction of travel U has a flow velocity distribution), the maximum value of which is defined as U _max, and the U of the nozzle whose outlet diameter is determined so as to appropriately expand with the same throat diameter as the absolute pressure P _O on the inlet side of the nozzle. Define _max as U _maxp . At this time, the ratio is shown as a value not _{depending on} the absolute value of FO2. In addition, U _max and U _maxp use values calculated by the present inventors based on the results of jet flow velocity measurement performed using a pitot tube.
[0016]
Here, for a certain acid feed rate F _O2 , under the condition that the throat diameter of the nozzle is constant _dt , that is, under the condition that the absolute pressure P _O on the inlet side of the nozzle is constant, the formula (1) and (2) ) expression, or (1) using the nozzle of the formula and (3) exit diameter d _e that satisfies any of the conditions of expression can be significantly reduced U _max as shown in FIG.
Also from this fact, for existing lance designed in the ratio of the diameter out of one nozzle _{d e} and the throat diameter _{d t d e / d t,} (1) and Equation (4), or (1) By operating with the absolute pressure P _O on the inlet side of the nozzle that satisfies either of the conditions of the formulas (5) and (5) in actual operation, the formula (6) or (6) ′ is replaced by F _O2 ). Similarly, U _max can be greatly reduced.
[0017]
Further, as shown in FIG. 1, as a more desirable range of the present invention corresponding to claim 1, any one of the above formula (1) and the following formula (7), or the above formula (1) and the following formula (8) the use of satisfying lance can be made further suppress U _max, increase the dust generation amount reducing effect.
P _O /1.8≦P _Op ≦ P _O /1.3 (7)
P _O /0.7≦P _Op … (8)
Similarly, as a more desirable range of the present invention corresponding to claim 3 , the above formula (1) and the following formula (9) or the above formula (1) and the following formula (10) are satisfied. By operating with the absolute pressure P _O on the inlet side of the nozzle (in actual operation, it can be replaced with F _O2 from equation (6) or (6) ′), it is possible to further reduce U _max and enhance the dust generation reduction effect. Can be.
[0018]

FIG. 4 shows an example of the relationship between the _de / _dt and the absolute pressure _Po on the nozzle entrance side in order to more specifically show the claims of the present invention. The scope of the invention, the outlet portion atmosphere absolute pressure P _e during _operation, and the absolute value to be taken by the d _{e /} d _t and P _Op by the value of the oxygen-flow-rate F _O2 or entrance side absolute pressure P _o of nozzles different However, by satisfying the relations of the expressions (1) to (5) in the claims, the distance between the lower end of the lance and the molten metal surface and the acid feed rate are kept the same, and the molten iron The maximum jet flow velocity at the surface can be made smaller than the conventional value. As an example in Figure 4, the atmospheric pressure 1.033kgf / cm ² in the case of the conventional converter of _{P e} in equation (1), (2) _{(P o /2.0≦P Op ≦ P o} / 1.2) is divided into two expressions, P _o /2.0=P _Op (2) ′ and P _Op = P _o /1.2 (2) ″, and each is divided into the expression (1). by substituting the equation (1) is shown the respective curves as two relations of _d e / _{d t} and _{P o.} (3) the same applies to the type. that is, _P e = 1 of the present invention .033Kgf / for the case of cm ² is, _d e / _{d t} is larger than the curve of _P o _{/ P} Op = 0.8 indicated by oblique lines in FIG. 4 range and _P o _{/ P} Op = _1.2~ 2.0 a region, the relationship between d _{e /} d _t and P _o of the claims that are present in this region is not one. in fact, it is used in the operation Range that _{P o} is from about 3~25kgf / cm ^2, to determine the _{P o} as the procedure of _d e / _{d t} is about 1 or more ranges _.d e / _{d t} determined corresponding to these this a seeking relationship diagram shown in FIG. 4, for example if Kimare the _{P o} and 5.0 kgf / cm ² by _{F O2} during operation from (6) _Te, the optimal region of d e / _{d t} is about 1. becomes 02 to 1.11 and 1.21 above two areas, the optimum area of _d e / _{d t} be determined to _{P o} and 15.0kgf / cm ² is about 1.27 to 1.47 and 1.65 From these areas, _de / _dt is further narrowed down from other conditions, such as the shape of the lance body or the lance cooling method, etc. Further, the horizontal axis P in FIG. _o = about ^{_{4.5kgf / cm 2, P o /}} P Op and _{d e} obtained by substituting the relationship between the d _t is 1.
[0019]
【Example】
Using a top and bottom blown converter with an inner diameter of about 1.2 m, 6 tons of molten iron were charged, and for each of the six types of lances A, B, C, D, E, and F, the distance between the lance tip and the molten iron stationary metal surface The distance was changed to two stages, and a total of 12 levels of decarburization tests were performed at an oxygen gas flow rate of 1200 Nm ³ / h and a nozzle inlet side absolute pressure of 4.5 kgf / cm ² . At any level, 300 Nm ³ / h of nitrogen was used as the bottom blown gas. Immediately after the refining was started, 130 kg of lime was added so that the basicity became about 3.5. Table 1 shows the design values of each lance, and Table 2 shows the test conditions and test results. Further, among the lances of the present invention, E and F correspond to a more desirable range.
[0020]
[Table 1]

[0021]
[Table 2]

[0022]
The result of this example will be described. In the present embodiment, a 6-ton converter based on an actual furnace is used to set the lance height to two levels (600, 1000 mm) as the actual operation level under the lance conditions (Table 1). That is, BF of the present invention compared with Comparative Example A quantitatively expresses how the dust generation amount and the secondary combustion rate are improved.
[0023]
In the conventional method, when the dust was reduced, the secondary combustion rate increased. However, in the present inventions B to F, based on Comparative Example A, the dust decreased under the same lance height and the secondary combustion rate decreased. The burn rate (PCR) is not higher than Comparative Example A. In addition, since the degree of wear of the refractory is proportional to the PCR, in the present embodiment, the secondary combustion rate which has a primary relationship with the amount of generated dust is arranged.
[0024]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to reduce the amount of dust generation, without causing a bad influence on the refractory in a furnace and an increase in a secondary combustion rate.
[Brief description of the drawings]
[1] inlet side absolute pressure _{P O} of the nozzle according to the present invention enters the ratio _d e / _{d t} of 4.5 outlet diameter of (a) a nozzle when kgf / cm ² _{d e} and the throat diameter _{d t} relationship side absolute pressure _{P O} and proper inflation absolute pressure _{P Op} ratio _P O _{/ P Op,} perpendicular to the ratio _d e / _{d t} and the jet traveling direction of (b) out of the nozzle diameter _{d e} and the throat diameter _{d t} nozzles in the jet central axis upstream speed _{U max} and the throat diameter in the cross section entrance side absolute nozzle that defines the outlet diameter to properly inflated with pressure _{P O} of the jet central axis upstream speed _{U maxp} ratio _U max _{/ U maxp} of It is a figure showing a relation.
FIGS. 2A and 2B are diagrams illustrating an embodiment of the present invention, in which FIG. 2A is a schematic diagram illustrating an embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing the relationship between the secondary combustion rate and the amount of dust generated, based on the test results at each level of the example.
FIG. 4 is a diagram showing claims 2 and 4 of the present invention more specifically based on the relationship between the _de / _dt and the _PO .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Refining vessel 2 ... Lance 3 ... Molten iron 4 ... Distance between lance tip and molten iron stationary metal surface 5 ... Lance nozzle 6 ... Throat diameter 7 ... Outlet diameter 8 ... Oxygen gas flow

Claims (3)

A lance for refining molten iron used for refining molten iron while supplying oxygen gas, wherein an outlet diameter (d _e (cm)) and a throat diameter (d) of at least one of nozzles provided at the tip of the lance are provided. _t (cm)) the ratio d _e / d _t between the outlet portion atmosphere absolute pressure of the nozzle ^{_{(P e (kgf / cm 2}} )), and proper inflation absolute pressure of the nozzle ^{_{(P Op (kgf / cm 2}} )) From the relational expression (1), and that the value of P _Op in the relational expression (1) was limited to the range of the following expression (2) or (3) by the ratio with the absolute pressure P _O on the inlet side of the nozzle. A characteristic lance for molten iron smelting.
d _e / d _t = 0.509 ・ (P _e / P _Op ) ^-5/14・ ｛1- (P _e / P _Op ) ^2/7 ｝ ^-1 / ⁴ … (1)
_{P o /2.0≦ P op ≦ P o} /1.2 ... (2)
P _O /0.8≦P _op … (3) 2. A method for refining molten iron according to claim 1, wherein the rate of dust generation with respect to the distance between the lower end of the specific lance and the molten metal surface when the total gas supply speed is maximized is minimized by the molten metal refining lance according to claim 1. At least one of the outlet diameter of the nozzle (d _e (cm)) and the throat diameter (d _t (cm)) and the ratio d _e / d _t the outlet atmosphere absolute pressure of the nozzles of the nozzle provided at the tip portion of the lance ( P _e (kgf / cm ² )) and the appropriate expansion absolute pressure of the nozzle (P _Op (kgf / cm ² )) using the molten metal smelting lance determined from equation (1) and the inlet side of the nozzle A molten iron smelting method characterized by using the ratio between the absolute pressures P _O and P _{Op in} the range of the following formula (4) or (5).
d _e / d _t = 0.509 ・ (P _e / P _Op ) ^-5/14・ ｛1- (P _e / P _Op ) ^2/7 ｝ ^-1 / ⁴ … (1)
1.2 ・ P _op ≦ P _o ≦ 2.0 ・ P _op … (4)
P _o ≦ 0.8 ・ P _op … (5)

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