JP3590442B2 - Blast furnace operation method - Google Patents

Description

【００１０】
【作用】
スラグ−メタル間の各成分の分配平衡はスラグ−メタル間の温度と酸素分圧により大きく影響される。スラグ−メタル間の酸素分圧を決める反応としては、下記（５）式が一般的である。
Ｆｅ＋１／２Ｏ_２ ＝ＦｅＯ ・・・（５）
ところで、（５）式からＰ_Ｏ２を求めるためにはＴの値を知る必要がある。従来は、このＴとして、溶銑温度または（溶銑温度＋ΔＴ）を代入して求めていた。しかし、これらの温度は必ずしもスラグ−メタル間の温度を表しているとはいえない。このため、湯だまりでの溶銑の滞留時間の変動内ではほぼ平衡に到達していると考えられるＭｎとの反応を考え、スラグ組成とメタル組成のデータのみからスラグ−メタル界面温度Ｔを推定する。すなわち、下記（６）式の反応を考えることにより、スラグ組成とメタル組成からスラグ−メタル界面温度を推定することができる。さらに、このようにして算出したＴを前記（２）式に代入することにより、スラグ−メタル界面の酸素分圧を求めることができる。
【００１１】
以下に、Ｆｅ，Ｍｎのスラグ−メタル間の分配平衡から、炉内のスラグ−メタル界面温度と酸素分圧を計算する方法を示す。
スラグ−メタル間のＦｅ，Ｍｎの反応として、下記（６）式の反応を考える。

ここで、ｌｎ γ_ＦｅＯ ＝ｔ_２ ｌｎγ_ＦｅＯ ^（ｔ２）／Ｔ
ｌｏｇ ａ_{Ｆｅ（１）} ＝−（０．３６＋１７００／Ｔ）（ｘ_Ｃ ／（１−ｘ_Ｃ ））^２ ＋ｌｏｇ（（１−２ｘ_Ｃ ）／（１−ｘ_Ｃ ））
の関係および前記（３）式および（４）式を用いてＴについて整理すると、下記（１）式が得られる。
【００１２】
Ｔ＝（２０１２４−４２３３［％Ｓｉ］−ｔ_１ ｌｎγ_ＭｎＯ ^（ｔ１）＋ｔ_２ ｌｎγ_ＦｅＯ ^（ｔ２）＋３９１５（ｘ_Ｃ ／（１−ｘ_Ｃ ））^２ ）／（９．４１＋０．１２４［％Ｃ］−２．２２［％Ｓｉ］−０．８２９（ｘ_Ｃ ／（１−ｘ_Ｃ ））^２ ＋ｌｎ（Ｘ_ＭｎＯ ・（１−２ｘ_Ｃ ）／（［％Ｍｎ］・Ｘ_ＦｅＯ ・（１−ｘ_Ｃ ）））） ・・・（１）
ここで、
ΔＧ°_（６） ：（６）式の反応の標準自由エネルギー変化［Ｊ／ｍｏｌ］
Ｋ_（６） ：（６）式の反応の平衡定数［−］
ｆ_Ｍｎ：温度Ｔ［Ｋ］におけるメタル中のＭｎの活量係数［−］
γ_ＭｎＯ ：温度Ｔ［Ｋ］におけるスラグ中のＭｎＯの活量係数［−］
γ_ＦｅＯ ：Ｆｅと平衡する純溶融ＦｅＯを基準とする温度Ｔ［Ｋ］
におけるスラグ中のＦｅＯの活量係数［−］
ａ_{Ｆｅ（１）} ：メタル中のＦｅの活量［−］
ｘ_Ｃ ：メタル中のＣのモル分率［−］
Ｒ：気体定数［Ｊ／Ｋ］
【００１３】
また、下記（７）式の反応を考える。

Ｐ_Ｏ２について整理すると、下記（２）式が得られる。（２）式中のＴは、前記（１）式により算出した値を用いる。
Ｐ_Ｏ２＝（（γ_ＭｎＯ ・Ｘ_ＭｎＯ ）／（ｆ_Ｍｎ・［％Ｍｎ］））^２ ・ｅｘｐ（−９７５１８／Ｔ＋３０．５８） ・・・（２）
ここで、
ΔＧ°_（７） ：（７）式の反応の標準自由エネルギー変化［Ｊ／ｍｏｌ］
Ｋ_（７） ：（７）式の反応の平衡定数［−］
【００１４】
以上の方法で求めたＴおよびＰ_Ｏ２は、γ_ＭｎＯ ^（ｔ１）等の物性値により異なるが、通常の管理では常に一定の値を用いる限りにおいては、これらの物性値は概略値を用いても差し支えない。つまり、ＴおよびＰ_Ｏ２の絶対値はγ_ＭｎＯ ^（ｔ１）等の物性値により変わるが、通常操業時との比較において平衡到達率は大きく変わらないからである。
【００１５】
平衡到達率が炉底温度と相関がある理由については、以下のように推定できる。
炉底底部の温度が高い場合、すなわち湯流れが炉底底部全体を通る場合は、炉底側壁部の温度が高い場合、すなわち湯流れが炉底周辺部に集中する場合に比べ、湯の滞留時間が長い。これは、出銑速度が一定ならば、湯流れが炉底周辺部に集中する場合は、湯が通る部分の体積が小さいためである。従って、湯流れが炉底周辺部に集中する場合には、スラグ−メタルの接触時間が短く、平衡到達率が低くなると推定される。
ここで、発明者らはＳｉ，Ｓは湯だまりでの溶銑の滞留時間の変動に対応して平衡到達率が変動することを見出したことにより、本発明を完成するに至ったものである。
【００１６】
次に、前記（１）式および（２）式で求めた温度、酸素分圧を用いて、平衡Ｓｉ濃度、平衡Ｓ分配比を求める方法を示す。
スラグ−メタル界面でのＳｉの反応は下記（８）式で表される。

ここで、
ΔＧ°_（８） ：（８）式の反応の標準自由エネルギー変化［Ｊ／ｍｏｌ］
Ｋ_（８） ：（８）式の反応の平衡定数［−］
［％Ｓｉ］^ｅｑ：平衡Ｓｉ濃度［ｍａｓｓ％］
【００１７】
また、スラグの脱硫能の尺度である、サルファイドキャパシティＣ_Ｓ が、温度とスラグ組成の関数として、高炉スラグの場合には下記（９）式で表される。
ｌｎＣ_Ｓ ＝７．９２Ｘ_ＣａＯ ＋０．７９Ｘ_ＭｇＯ −６．３４Ｘ_{Ａｌ２Ｏ３} −７．９２Ｘ_ＳｉＯ２−２２７８０／Ｔ＋４．７２ ・・・（９）
一方、定義より、
Ｃ_Ｓ ＝（％Ｓ）・（Ｐ_Ｏ２／Ｐ_Ｓ２）^１／２ ・・・（１０）
【００１８】
ここで、下記（１１）式の反応を考える。

（９）式、（１０）式、（１２）式からＣ_Ｓ ，Ｐ_Ｓ２を消去すると、

【００１９】
前記（１３）式に前記（１）式および（２）式で求めた温度、酸素分圧および他の数値を代入し、Ｌ_Ｓ ^ｅｑを求めることができる。
ここで、
ΔＧ°_（１１）：（１１）式の反応の標準自由エネルギー変化［Ｊ／ｍｏｌ］
Ｋ_（１１）：（１１）式の反応の平衡定数［−］
Ｐ_Ｓ２：Ｓ_２ 分圧［ａｔｍ］
Ｘ_ＣａＯ ：スラグ中のＣａＯのモル分率［−］
Ｘ_ＭｇＯ ：スラグ中のＭｇＯのモル分率［−］
Ｘ_{Ａｌ２Ｏ３} ：スラグ中のＡｌ_２ Ｏ_３ のモル分率［−］
Ｌ_Ｓ ：Ｓ分配比［−］
Ｌ_Ｓ ^ｅｑ：平衡Ｓ分配比［−］
【００２０】
次に、炉内のスラグ−メタル反応の平衡到達率Ｎ_Ｓｉ’，Ｎ_Ｓ ’を下記（１４）式および（１５）式で定義する。
Ｎ_Ｓｉ’＝［％Ｓｉ］^ｅｑ／［％Ｓｉ］×１００ ・・・（１４）
Ｎ_Ｓ ’＝Ｌ_Ｓ ^ｅｑ／Ｌ_Ｓ ×１００ ・・・（１５）
【００２１】
本発明者らは、このように定義したＮ_Ｓｉ’，Ｎ_Ｓ ’が、炉底底部の温度が高く側壁部の温度が低い場合、すなわち炉況が良好な場合には１００に近い値となり、側壁部の温度が上昇し炉底底部の温度が低下する場合には低下することを見出した。
従って、Ｎ_Ｓｉ’，Ｎ_Ｓ ’を管理し、所定の基準値よりも低下した場合に燃料比を増大させることにより、炉底レンガ温度で検知する方法よりも速やかにアクションを行うことができる。
【００２２】
また、燃料比増大等のアクションにより、炉底底部の溶銑凝固層が薄層化した場合、従来の方法ではレンガ温度に表れるまでの期間は炉内の状況を検知する手段が無いために燃料比増大等のアクションを行い続けなければならないが、本発明方法では、速やかに炉内の状況が検知できるため、余分なアクションを行う必要がなくなる。
平衡到達率が通常操業時に対し、Ｓｉの場合は７０％未満、Ｓの場合は８０％未満となる場合に燃料比を増大させる理由は、ＳｉはＳに比べ平衡するまでの時間が長いためであり、実炉データを解析した結果、Ｓｉで７０％未満、Ｓで８０％未満の状態が続くケースで炉底底部の温度が低下することが見出されたからである。
【００２３】
【実施例】
以下に、本発明での実施例を説明する。
実施例１は、日平均データを基にＳｉの平衡到達率Ｎ_Ｓｉ’を管理し、対応した例である。
Ａ高炉では安定操業を継続している時は、［％Ｓｉ］^ｅｑ＝０．２〜０．４に対して、［％Ｓｉ］＝０．２５〜０．５であり、Ｎ_Ｓｉ’＝８０〜８５の範囲である。ところが、ある時期からＮ_Ｓｉ’が低下し、［％Ｓｉ］^ｅｑ＝０．３に対し、［％Ｓｉ］＝０．６となり、通常操業時のほぼ６０％である５０まで低下した。このため、燃料比をそれまでの４８０ｋｇ／ｔから４８５ｋｇ／ｔまで増加した操業を１週間継続したところ、Ｎ_Ｓｉ’は従来の安定域である８２まで回復した。また、このとき炉底中心部のレンガ温度は管理下限である２００℃を下回らなかった。
【００２４】
実施例２は、日平均データを基にＳの平衡到達率Ｎ_Ｓ ’を管理し、対応した例である。
Ｂ高炉では安定操業を継続している時は、Ｌ_Ｓ ^ｅｑ＝２５〜３０，Ｎ_Ｓ ’＝９５〜１００の範囲である。ところが、Ｎ_Ｓ ’が低下し、Ｌ_Ｓ ^ｅｑ＝２５に対し、Ｌ_Ｓ ＝３７となり、通常操業時のほぼ７０％である６８まで低下した。このため、燃料比をそれまでの４７５ｋｇ／ｔから４８０ｋｇ／ｔまで増加し、炉底底部の冷却水量を５０％少なくした操業を５日間継続したところ、Ｎ_Ｓ ’は従来の安定域である９６まで回復した。この場合も、炉底中心部のレンガ温度は管理下限である１５０℃以上確保されていた。
【００２５】
比較例１は、炉底レンガ温度による管理を行った例である。
Ａ高炉では安定操業を継続している時は、炉底中心部のレンガ温度は２００〜３５０℃の範囲にある。ところが、ある時期からレンガ温度が低下し始め管理下限を下回ったため、燃料比をそれまでの４８０ｋｇ／ｔから４８５ｋｇ／ｔまで増加し、炉底底部の冷却水量を３０％少なくした操業を継続したが、炉底中心部のレンガ温度が管理下限の２００℃以上になるまでに約２ケ月かかった。この間は、減産操業となり経済的損失は膨大なものであった。
【００２６】
比較例２は、Ａ高炉で炉底中心部のレンガ温度が管理範囲内にあったが、レンガ温度が低下し始めた時点で対応した例である。
それまで炉底中心部のレンガ温度は２５０℃に保たれていたが、ある時期からレンガ温度が低下し始めた。直ちに燃料比をそれまでの４８０ｋｇ／ｔから４８５ｋｇ／ｔまで増加した操業を行ったが、レンガ温度の低下は止まらず管理下限である２００℃を下回った。このため、さらに炉底底部の冷却水量を３０％少なくした操業を継続したが、炉底中心部のレンガ温度が管理範囲になるまでに約１ケ月を要した。
【００２７】
【発明の効果】
本発明により、炉底状況を回復させるための速やかな対応が可能である。これにより、生産率を下げる期間を大幅に短縮することが可能となった。[0001]
[Industrial applications]
The present invention relates to a blast furnace operating method for detecting a precursor of operation deterioration, stabilizing the operation in a short time, and extending the life of the furnace bottom.
[0002]
[Prior art]
Maintaining good ventilation and liquid permeability of the blast furnace, in particular, good ventilation of the furnace core and liquid permeability of the furnace bottom is essential for stable operation of the blast furnace. In order to maintain good ventilation and liquid permeability, it is important not to lower the temperature. The reason for this is that the viscosity of the liquid phase, particularly the slag phase, increases as the temperature decreases, and the rate of hold-up in the coke layer increases, impeding ventilation and liquid permeability.
By the way, the temperature of the furnace bottom is mainly input by the hot metal sensible heat. That is, the portion of the furnace bottom where the hot water flow is good has a large heat input and a high temperature.
[0003]
On the other hand, from the viewpoint of hearth protection, it is necessary to generate a solidified layer of hot metal on the brick surface. Since the amount of heat input must be reduced in order to form a molten iron solidified layer, it is necessary to stop the flow of molten metal.
It is known from the results of blast furnace dismantling investigations and past hearth breakage accidents that the part of the hearth that is particularly susceptible to erosion is the side wall, and it is necessary to form a molten iron solidified layer in this part to protect it. That is, in order to protect the furnace bottom while maintaining good ventilation and liquid permeability, the flow of the molten metal may be prevented from concentrating around the furnace bottom.
[0004]
Until now, the flow of hot water at the bottom was estimated at the bottom brick temperature. In other words, thermocouples are buried in the circumferential direction of the furnace bottom brick, in the radial direction and in the circumferential direction of the side wall bricks, at several places to several tens of places in the height direction, and on the brick surface in the blast furnace from the temperature measurement results. The thickness of the formed hot metal solidified layer was calculated, and it was estimated that the hot metal flow was active in the thin portion of the hot metal solidified layer and that the hot metal flow was stagnant in the thick portion of the hot metal solidified layer. Therefore, in order to protect the furnace bottom while maintaining good ventilation and liquid permeability, it is necessary to keep the temperature of the furnace bottom bottom high and the temperature of the furnace bottom side wall low.
[0005]
Conversely, when the temperature of the bottom of the furnace bottom decreases and the temperature of the side wall increases, the molten iron solidified layer has developed in the bottom of the furnace bottom. For this reason, in order to return to the original state, it is necessary to increase the fuel ratio and dissolve the molten iron solidified layer at the bottom of the furnace bottom. In this case, it takes about two to three weeks from when the action is performed until a change in the furnace bottom appears in the brick temperature, so that the response tends to be delayed.
In addition, several methods for estimating the conditions inside the furnace using the slag-metal reaction have been reported in the literature (for example, edited by the Iron and Steel Institute of Japan, Interim Report “Blast Furnace Phenomena and Analysis” (1979), p. 126). The temperature of the slag-metal interface is substituted by the hot metal temperature or (hot metal temperature + ΔT), and does not necessarily represent the actual slag-metal interface temperature.
[0006]
[Problems to be solved by the invention]
It is desirable that the molten metal flow in the furnace bottom flows over the entire bottom of the furnace bottom from the viewpoint of protecting the furnace body and maintaining good ventilation and liquid permeability of the furnace core. There is no direct action to equalize the flow of hot water at the bottom of the furnace, but a method of increasing the fuel ratio or relaxing the cooling of the bottom of the furnace bottom and thinning the molten iron solidified layer at the bottom of the furnace bottom is common. It is a target.
However, in the related art, it is impossible to estimate a change in the hearth in a short time, so that it is necessary to cope with a state in which the solidified layer of hot metal is enlarged. Furthermore, even if the furnace bottom actually returns to a good state, there is no means to detect it until it appears at the brick temperature, so actions such as increasing the fuel ratio must be continued. There's a problem.
An object of the present invention is to detect a state of a furnace bottom in a short time, thereby enabling to cope before a hot metal solidified layer is enlarged and to cope without performing excessive action. .
[0007]
[Means for Solving the Problems]
The present invention is to take the following means in order to solve the above problems. That is,
(1) At the time of tapping in the blast furnace, the measured values of the FeO and MnO concentrations in the slag and the measured values of the C, Si and Mn concentrations in the metal, and the equilibrium reaction between the slag and metal of Fe and Mn in the blast furnace, The temperature of the slag-metal interface in the blast furnace is obtained from the following equation (1) , the oxygen partial pressure is obtained from the following equation (2) using the temperature, and CaO, SiO ₂ , Al ₂ O ₃ and MgO in the slag are further obtained. From the measured value of the concentration and the temperature of the slag-metal interface and the oxygen partial pressure, the equilibrium attainment rate of the slag-metal reaction of Si in the blast furnace was calculated, and the value of the equilibrium attainment rate was the equilibrium attainment rate during normal operation. A blast furnace operating method characterized by increasing the fuel ratio when the fuel ratio is less than 70%.
T = (20124-4233 [% Si] -t 1 lnγ _MnO ^(t1) + t ₂ lnγ _FeO ^(t2) +3915 (x _C / (1-x _C )) ² ) / ( 9.41 + 0.124 [ % _C ] -2.22 [ % Si] -0.829 ( xC / (1-x _C )) ² + Ln (X _MnO ・ (1-2x _C )
/ ([% Mn] · X FeO ・ (1-x _C )))) ・ ・ ・ (1)
P _O2 = ((γ _MnO ・ X _{MnO ) / (F Mn · [%} Mn])) 2 · exp (-97518 / T + 30.58) ··· (2)
[0008]
(2) At the time of tapping in the blast furnace, the measured values of the FeO and MnO concentrations in the slag and the measured values of the C, Si and Mn concentrations in the metal, and the equilibrium reaction between the slag and metal of Fe and Mn in the blast furnace, The temperature of the slag-metal interface in the blast furnace is obtained from the following equation (1) , the oxygen partial pressure is obtained from the following equation (2) using the temperature, and S in the metal and CaO, SiO ₂ , Al in the slag are further obtained. The equilibrium attainment rate of the slag-metal reaction of S in the blast furnace is calculated from the measured values of the ₂ O ₃ , MgO, and S concentrations and the temperature at the slag-metal interface and the oxygen partial pressure. A blast furnace operating method characterized by increasing the fuel ratio when the equilibrium attainment rate during operation is less than 80%.
[0009]
At this time, γ _MnO . f _Mn is obtained by the equations (3) and (4).

[0010]
[Action]
The distribution equilibrium of each component between slag and metal is greatly affected by the temperature and oxygen partial pressure between slag and metal. The following equation (5) is generally used as a reaction for determining the oxygen partial pressure between slag and metal.
Fe + 1 / 2O ₂ = FeO (5)
Incidentally, it is necessary to know the value of T in order to obtain _P02 from equation (5). Conventionally, T has been determined by substituting the hot metal temperature or (hot metal temperature + ΔT). However, these temperatures do not always represent the temperature between the slag and the metal. For this reason, considering the reaction with Mn, which is considered to have reached almost equilibrium within the variation of the residence time of the hot metal in the basin, the slag-metal interface temperature T is estimated only from the data of the slag composition and the metal composition. . That is, by considering the reaction of the following equation (6), the slag-metal interface temperature can be estimated from the slag composition and the metal composition. Further, the oxygen partial pressure at the slag-metal interface can be obtained by substituting T calculated in this way into the above equation (2).
[0011]
Hereinafter, a method for calculating the slag-metal interface temperature and the oxygen partial pressure in the furnace from the slag-metal distribution equilibrium of Fe and Mn will be described.
As a reaction between Fe and Mn between slag and metal, a reaction represented by the following formula (6) is considered.

_{Here, ln γ FeO = t 2 lnγ} FeO (t2) / T
_{log a Fe (1) = -} (0.36 + 1700 / T) (x C / (1-x C)) 2 + log ((1-2x C) / (1-x C))
The following equation (1) is obtained by rearranging T using the relation (1) and the equations (3) and (4).
[0012]
T = (20124-4233 [% Si] -t 1 lnγ MnO (t1) + t 2 lnγ FeO (t2) +3915 (x C / (1-x C)) 2) / (9.41 + 0.124 [% C] ^{_{-2.22 [% Si] -0.829 (x}} C / (1-x C)) 2 + ln (X MnO · (1-2x C) / ([% Mn] · X FeO · (1-x C )))) ・ ・ ・ (1)
here,
ΔG ° ₍₆₎ : Standard free energy change [J / mol] of the reaction of formula (6)
K ₍₆₎ : equilibrium constant [-] for the reaction of equation (6)
f _Mn : activity coefficient of Mn in metal at temperature T [K] [-]
γ _MnO : activity coefficient of MnO in slag at temperature T [K] [-]
γ _FeO : Temperature T [K] based on pure molten FeO equilibrating with Fe
Activity coefficient of FeO in slag [-]
a _{Fe (1)} : Activity of Fe in metal [-]
x _C: molar fraction of C in the metal [-]
R: gas constant [J / K]
[0013]
Also, consider the reaction of the following equation (7).

When P _O2 is arranged, the following equation (2) is obtained. As the T in the expression (2), a value calculated by the expression (1) is used.
P _O2 = ((γ _MnO · X _MnO ) / (f _Mn · [% Mn])) ² · exp (−97518 / T + 30.58) (2)
here,
ΔG ° ₍₇₎ : Standard free energy change [J / mol] of the reaction of formula (7)
K ₍₇₎ : equilibrium constant [-] for the reaction of equation (7)
[0014]
Although T and _PO2 obtained by the above method differ depending on physical properties such as γ _MnO ^(t1), as long as a constant value is always used in normal management, these physical properties can be approximated by using approximate values. No problem. That is, the absolute value of T and P _O2 is varied by physical properties such as gamma _{MnO ^(t1),} but the equilibrium arrival rate in comparison with the normal operation because no large difference.
[0015]
The reason why the equilibrium attainment rate has a correlation with the furnace bottom temperature can be estimated as follows.
When the temperature at the bottom of the furnace bottom is high, that is, when the flow of the molten metal passes through the entire bottom of the furnace bottom, the temperature of the side wall of the furnace bottom is high, that is, when the flow of the molten metal is concentrated around the bottom of the furnace bottom, Time is long. This is because if the tapping speed is constant, the volume of the portion through which the hot water flows is small when the flow of the hot water is concentrated around the furnace bottom. Therefore, when the flow of the molten metal is concentrated on the periphery of the furnace bottom, it is estimated that the contact time between the slag and the metal is short and the equilibrium attainment rate is low.
Here, the inventors have completed the present invention by finding that the equilibrium attainment rate of Si and S changes in response to the change of the residence time of the hot metal in the hot water pool.
[0016]
Next, a method for obtaining the equilibrium Si concentration and the equilibrium S distribution ratio using the temperature and the oxygen partial pressure obtained by the above equations (1) and (2) will be described.
The reaction of Si at the slag-metal interface is represented by the following equation (8).

here,
ΔG ° ₍₈₎ : Standard free energy change [J / mol] of the reaction of formula (8)
K ₍₈₎ : Equilibrium constant [-] for the reaction of equation (8)
[% Si] ^eq : equilibrium Si concentration [mass%]
[0017]
Furthermore, a measure of the desulfurization capacity of the slag, sulfide capacity C _S is, as a function of temperature and slag composition in the case of blast furnace slag is expressed by the following equation (9).
_{lnC S = 7.92X CaO + 0.79X MgO} -6.34X Al2O3 -7.92X SiO2 -22780 / T + 4.72 ··· (9)
On the other hand, by definition,
C _S = (% S) · (P _O2 / P _S2 ) ^1/2 (10)
[0018]
Here, the reaction of the following equation (11) is considered.

Eliminating C _S and P _S2 from equations (9), (10), and (12) gives:

[0019]
L _S ^eq can be determined by substituting the temperature, oxygen partial pressure and other numerical values determined by the expressions (1) and (2) into the expression (13).
here,
ΔG ° ₍₁₁₎ : Standard free energy change [J / mol] of the reaction of formula (11)
K ₍₁₁₎ : equilibrium constant [-] for the reaction of equation (11)
P _{S2: S 2} partial pressure [atm]
X _CaO : molar fraction of CaO in slag [-]
X _MgO : molar fraction of MgO in slag [-]
X _{Al2 O3:} mole fraction of _Al 2 _{O 3} in the slag [-]
L _S : S distribution ratio [-]
L _S ^eq: equilibrium S distribution ratio [-]
[0020]
Next, the equilibrium attainment ratios N _Si ′ and N _S ′ of the slag-metal reaction in the furnace are defined by the following equations (14) and (15).
N _Si ′ = [% Si] ^eq / [% Si] × 100 (14)
^{_{N S '= L S eq /}} L S × 100 ··· (15)
[0021]
The present inventors have determined that N _Si ′, N _s ′ thus defined is close to 100 when the temperature of the furnace bottom is high and the temperature of the side wall is low, that is, when the furnace condition is good, It has been found that when the temperature at the side wall increases and the temperature at the bottom of the furnace bottom decreases, the temperature decreases.
Therefore, by managing N _Si ′ and N _S ′ and increasing the fuel ratio when the value falls below a predetermined reference value, an action can be taken more quickly than in the method of detecting the temperature of the hearth brick.
[0022]
In addition, when the molten iron solidified layer at the bottom of the furnace is thinned due to an action such as increasing the fuel ratio, the conventional method has no means to detect the condition inside the furnace until the temperature of the furnace reaches the brick temperature. Although the action such as increase must be continuously performed, the method of the present invention can quickly detect the condition in the furnace, so that it is not necessary to perform an extra action.
The reason why the fuel ratio is increased when the equilibrium attainment ratio is less than 70% for Si and less than 80% for S with respect to the normal operation is that Si takes longer to equilibrate than S. This is because, as a result of analyzing actual furnace data, it has been found that the temperature at the bottom of the furnace bottom decreases in the case where the state of less than 70% for Si and less than 80% for S continues.
[0023]
【Example】
Hereinafter, embodiments of the present invention will be described.
The first embodiment is an example in which the equilibrium attainment rate N _Si ′ of _Si is managed based on the daily average data, and corresponding.
When we continue stable operations in A blast ^furnace, against [% Si] eq = 0.2~0.4, a _{[% Si] = 0.25~0.5, N} Si '= 80 ~ 85. However, from a certain time, N _Si ′ decreased, and [% Si] ^eq = 0.3, compared with [% Si] = 0.6, and decreased to 50, which is almost 60% of the normal operation. Therefore, when the operation in which the fuel ratio was increased from 480 kg / t to 485 kg / t was continued for one week, N _Si ′ recovered to 82, which is the conventional stable range. At this time, the temperature of the brick at the center of the furnace bottom did not fall below the control lower limit of 200 ° C.
[0024]
The second embodiment is an example in which the equilibrium attainment ratio NS of _S is managed based on the daily average data, and corresponding thereto.
When continues stable operations in B blast _furnace, ^L S eq = _25~30, in the range of _{N S} '= _95~100. However, N _S ′ decreased, and L _S ^eq = 25, whereas L _S = 37, which decreased to 68, which is almost 70% of the normal operation. Therefore, the fuel ratio increased to 480 kg / t from 475 kg / t until then, was continued operations where the cooling water of the hearth bottom and 50% less for 5 days, _{N S} 'is a conventional stable zone 96 Recovered. Also in this case, the temperature of the brick at the center of the furnace bottom was maintained at 150 ° C. or more, which is the lower control limit.
[0025]
Comparative Example 1 is an example in which control was performed based on the furnace bottom brick temperature.
When the stable operation is continued in the blast furnace A, the brick temperature at the center of the furnace bottom is in the range of 200 to 350 ° C. However, since the brick temperature began to drop from a certain point and fell below the lower control limit, the fuel ratio was increased from 480 kg / t to 485 kg / t, and the operation was continued with the cooling water volume at the bottom of the furnace bottom reduced by 30%. It took about two months for the temperature of the brick at the center of the furnace bottom to reach or exceed the lower control limit of 200 ° C. During this time, the operation was reduced and the economic loss was enormous.
[0026]
Comparative Example 2 is an example in which the brick temperature at the center of the furnace bottom in the blast furnace A was within the control range, but the brick temperature started to decrease.
Until then, the temperature of the brick in the center of the furnace bottom was kept at 250 ° C, but from a certain point the brick temperature began to drop. Immediately, an operation was performed in which the fuel ratio was increased from 480 kg / t to 485 kg / t, but the temperature of the brick did not stop decreasing and fell below the control lower limit of 200 ° C. For this reason, the operation was continued with the cooling water amount at the bottom of the furnace bottom further reduced by 30%, but it took about one month until the temperature of the brick at the center of the furnace bottom became within the control range.
[0027]
【The invention's effect】
According to the present invention, a prompt response for restoring the furnace bottom condition is possible. This has made it possible to significantly reduce the period during which the production rate is reduced.

Claims (2)

From the measured values of the FeO and MnO concentrations in the slag and the measured values of the C, Si and Mn concentrations in the metal during the tapping of the blast furnace and the equilibrium reaction between the slag and metal of Fe and Mn in the blast furnace, the following (1) ) , The temperature of the slag-metal interface in the blast furnace is determined, the oxygen partial pressure is determined from the following equation (2) using the temperature, and the measured values of CaO, SiO ₂ , Al ₂ O ₃ , and MgO concentrations in the slag And the temperature of the slag-metal interface and the oxygen partial pressure to calculate the equilibrium attainment rate of the slag-metal reaction of Si in the blast furnace, and the value of the equilibrium attainment rate is less than 70% of the equilibrium attainment rate during normal operation. A blast furnace operating method characterized by increasing the fuel ratio when:
T = (20124-4233 [% Si] -t 1 lnγ _MnO ^(t1) + t ₂ lnγ _FeO ^(t2) +3915 (x _C / (1-x _C )) ² ) / ( 9.41 + 0.124 [ % _C ] -2.22 [ % Si] -0.829 ( xC / (1-x _C )) ² + Ln (X _MnO ・ (1-2x _C )
/ ([% Mn] · X FeO ・ (1-x _C )))) ・ ・ ・ (1)
P _O2 = ((γ _MnO ・ X _{MnO ) / (F Mn · [%} Mn])) 2 · exp (-97518 / T + 30.58) ··· (2)
Here, T: absolute temperature [K]
γ _MnO ^(t1): Temperature t ₁ Activity coefficient of MnO in slag at [K] [-]
γ _FeO ^(t2) : temperature t _{2 based} on pure molten FeO equilibrating with Fe Activity coefficient of FeO in slag at [K] [-]
[% C]: C concentration in metal [mass%]
[% Si]: Si concentration in metal [mass%]
[% Mn]: Mn concentration in metal [mass%]
x _C : Mole fraction of C in metal [-]
f _Mn : activity coefficient of Mn in metal at temperature T [K] [-]
X _MnO : Molar fraction of MnO in slag [-]
X _FeO : Mole fraction of FeO in slag [-]
P _O2 : oxygen partial pressure [atm]
γ _MnO : Activity coefficient of MnO in slag at temperature T [K] [-] From the measured values of the FeO and MnO concentrations in the slag and the measured values of the C, Si and Mn concentrations in the metal during the tapping of the blast furnace and the equilibrium reaction between the slag and metal of Fe and Mn in the blast furnace, the following (1) ) , The temperature of the slag-metal interface in the blast furnace is determined, and the temperature is used to determine the oxygen partial pressure from the following expression (2) . Further, S in the metal and CaO, SiO ₂ , Al ₂ O ₃ , The equilibrium attainment rate of the slag-metal reaction of S in the blast furnace is calculated from the measured values of the MgO and S concentrations and the temperature of the slag-metal interface and the oxygen partial pressure. A method for operating a blast furnace, wherein the fuel ratio is increased when the arrival rate is less than 80%.
T = (20124-4233 [% Si] -t 1 lnγ _MnO ^(t1) + t ₂ lnγ _FeO ^(t2) +3915 (x _C / (1-x _C )) ² ) / ( 9.41 + 0.124 [ % _C ] -2.22 [ % Si] -0.829 ( xC / (1-x _C )) ² + Ln (X _MnO ・ (1-2x _C )
/ ([% Mn] · X FeO ・ (1-x _C )))) ・ ・ ・ (1)
P _O2 = ((γ _MnO ・ X _{MnO ) / (F Mn · [%} Mn])) 2 · exp (-97518 / T + 30.58) ··· (2)
Here, T: absolute temperature [K]
γ _MnO ^(t1): Temperature t ₁ Activity coefficient of MnO in slag at [K] [-]
γ _FeO ^(t2) : temperature t _{2 based} on pure molten FeO equilibrating with Fe Activity coefficient of FeO in slag at [K] [-]
[% C]: C concentration in metal [mass%]
[% Si]: Si concentration in metal [mass%]
[% Mn]: Mn concentration in metal [mass%]
x _C : Mole fraction of C in metal [-]
f _Mn : activity coefficient of Mn in metal at temperature T [K] [-]
X _MnO : Molar fraction of MnO in slag [-]
X _FeO : Mole fraction of FeO in slag [-]
P _O2 : oxygen partial pressure [atm]
γ _MnO : Activity coefficient of MnO in slag at temperature T [K] [-]