JP2016050323A - Blast furnace operation method - Google Patents

Blast furnace operation method Download PDF

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JP2016050323A
JP2016050323A JP2014174849A JP2014174849A JP2016050323A JP 2016050323 A JP2016050323 A JP 2016050323A JP 2014174849 A JP2014174849 A JP 2014174849A JP 2014174849 A JP2014174849 A JP 2014174849A JP 2016050323 A JP2016050323 A JP 2016050323A
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coke
ore
blast furnace
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gas
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JP6119700B2 (en
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佐藤　健
Takeshi Sato
健 佐藤
義孝 澤
Yoshitaka Sawa
義孝 澤
佑介 柏原
Yusuke Kashiwabara
佑介 柏原
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JFE Steel Corp
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Abstract

PROBLEM TO BE SOLVED: To improve utility value of blast furnace gas as a heat source while attempting reduction of reduction material ratio.SOLUTION: Blast furnace operation is carried out by charging coke and ore in a blast furnace. As a part of the coke, high reactive coke that a coke reactivity index CRI as an indicator of reactivity of the coke is not less than 65% is used. An average value of a reducibility index RI as an indicator of reducibility of iron oxide of the ore is 50% or more and 65% or less.SELECTED DRAWING: None

Description

本発明は、反応性の高いコークスを使用する高炉操業方法で、還元材比の低減を図りつつも高炉ガスの熱源としての利用価値を向上させる方法に関する。   The present invention relates to a blast furnace operation method using coke having high reactivity, and a method for improving the utility value of a blast furnace gas as a heat source while reducing the reducing material ratio.

高炉では、コークスと、鉄源として鉱石と、を炉頂から装入し、炉下部に設けられた羽口から、空気あるいは空気に酸素を富化して加熱した熱風と、微粉炭、重油、燃料ガスなどを吹き込み、高炉内では、コークスや、微粉炭、重油、燃料ガスなどを燃焼して発生した一酸化炭素ＣＯガスを含むガスで鉱石を還元するとともに、燃焼熱により鉱石を溶融して銑鉄を生成する。コークスや、微粉炭、重油、燃料ガスなどは還元材と呼ばれ、前記銑鉄１トン当りの還元材の使用量は還元材比として管理される。該還元材比を低減することは、コークス及び微粉炭の原料となる石炭の使用量を削減するという点で重要であり、還元材比を低減する技術として、鉱石中の酸化鉄の還元反応の効率を向上させることが挙げられる。   In a blast furnace, coke and ore as an iron source are charged from the top of the furnace, hot air heated by enriching air or air from the tuyere provided at the bottom of the furnace, pulverized coal, heavy oil, fuel In the blast furnace, the ore is reduced with gas containing carbon monoxide CO gas generated by burning coke, pulverized coal, heavy oil, fuel gas, etc. Is generated. Coke, pulverized coal, heavy oil, fuel gas, and the like are called reducing materials, and the amount of reducing material used per ton of pig iron is managed as a reducing material ratio. Reducing the reducing material ratio is important in terms of reducing the amount of coal used as a raw material for coke and pulverized coal. As a technique for reducing the reducing material ratio, the reduction reaction of iron oxide in ore is important. Increasing efficiency.

次に、高炉を示す図４を参照して、高炉１における酸化鉄の還元反応について説明する。高炉１には、通常、炉頂から鉱石２とコークス３とが交互に積層するように装入される。高炉１には、側面下部に設けられた羽口５から熱風６が吹き込まれ、該熱風６とともに吹き込まれた微粉炭などやコークス３中の炭素が、熱風６中の酸素と燃焼し、高温の一酸化炭素ＣＯガスを含むガスが発生する。このガスが高炉内を上昇していく過程で鉱石２とコークス３とに熱が与えられ、鉱石２の酸化鉄が還元されるとともに該鉱石２が溶融することによって、銑鉄９及び溶滓８が生成する。銑鉄９は、高炉内底面に溜まり、溶滓８の一部とともに、高炉１の側面底部に設けられている出銑口７から高炉１外へ排出される。   Next, the iron oxide reduction reaction in the blast furnace 1 will be described with reference to FIG. 4 showing the blast furnace. The blast furnace 1 is usually charged so that the ore 2 and the coke 3 are alternately stacked from the top of the furnace. Hot air 6 is blown into the blast furnace 1 from the tuyere 5 provided at the lower side of the side, and the pulverized coal blown together with the hot air 6 and the carbon in the coke 3 are combusted with oxygen in the hot air 6, so A gas containing carbon monoxide CO gas is generated. Heat is applied to the ore 2 and the coke 3 in the process in which the gas rises in the blast furnace, the iron oxide of the ore 2 is reduced and the ore 2 is melted. Generate. The pig iron 9 accumulates on the bottom surface of the blast furnace, and is discharged out of the blast furnace 1 from a tap outlet 7 provided at the bottom of the side surface of the blast furnace 1 together with a part of the molten iron 8.

高炉１には、鉱石２が軟化して相互に融着しあう部分となる融着帯４が形成され、該融着帯４を含む高炉１内下部となる炉下部２２では、羽口５から供給される熱風６中の酸素と炭素が燃焼し、燃焼熱によって炉下部２２は高温となり、鉱石２は溶融状態になるとともに、炉下部２２では次の反応式に示す還元反応が生じる。
ＦｅＯ＋Ｃ＝Ｆｅ＋ＣＯ （１）
式（１）に示す還元反応は、コークス３の固体の炭素Ｃによる酸化鉄の還元反応であり直接還元反応と呼ばれ、吸熱反応である。高炉１内では、上部から下部に向かって固体温度が上昇するので、鉱石２は、始めは固体の状態であり、高炉１の中部では、炉頂から装入された固体の鉱石２が軟化・溶融し始め、前記融着帯４が形成されることになる。 In the blast furnace 1, a fusion zone 4 is formed in which the ore 2 is softened and fused to each other. In the furnace lower part 22 that is the lower part of the blast furnace 1 including the fusion zone 4, Oxygen and carbon in the supplied hot air 6 are combusted, and the lower part of the furnace 22 is heated by the combustion heat, the ore 2 is in a molten state, and a reduction reaction shown in the following reaction formula occurs in the lower part of the furnace 22.
FeO + C = Fe + CO (1)
The reduction reaction shown in the formula (1) is a reduction reaction of iron oxide by solid carbon C of coke 3 and is called a direct reduction reaction, and is an endothermic reaction. In the blast furnace 1, the solid temperature increases from the upper part toward the lower part, so the ore 2 is initially in a solid state, and in the middle part of the blast furnace 1, the solid ore 2 charged from the top of the furnace is softened. The fusion zone 4 is formed as it begins to melt.

融着帯４より上側となる炉上部２１では、固体状態の鉱石２とコークス３とが存在し、炉下部２２で生じ上昇していく一酸化炭素ＣＯガスによって鉱石２の酸化鉄が還元され、炉上部２１では、次の式に示す還元反応が生じる。
Ｆｅ２Ｏ３＋ＣＯ＝２ＦｅＯ＋ＣＯ２ （２）
Ｆｅ３Ｏ４＋ＣＯ＝３ＦｅＯ＋ＣＯ２ （３）
ＦｅＯ＋ＣＯ＝Ｆｅ＋ＣＯ２ （４）
式（２）〜（４）に示す還元反応は、一酸化炭素ＣＯによる酸化鉄の還元反応であり間接還元反応と呼ばれ、式（３）に示す還元反応を除き発熱反応であり、全体的に発熱反応である。炉上部２１における炉頂部分では、鉱石２の酸化鉄は主にはＦｅ２Ｏ３やＦｅ３Ｏ４であり、比較的温度が低い状態であっても、式（２）及び（３）に示す還元反応が生じ易く、鉱石２の酸化鉄はＦｅＯになる。次いで、鉱石２が下方に向かうにつれて、式（４）に示す還元反応が主に生じ、鉱石２の酸化鉄が還元される。なお、式（２）及び（３）に示す還元反応が主に生じる炉上部２１の部分を予熱帯と呼び、式（４）に示す還元反応が主に生じる炉上部２１の部分を熱保存帯と呼ぶ。 In the upper furnace portion 21 above the cohesive zone 4, the solid ore 2 and the coke 3 exist, and the iron oxide of the ore 2 is reduced by the carbon monoxide CO gas generated and raised in the lower furnace portion 22. In the furnace upper part 21, the reduction reaction shown in the following formula occurs.
Fe 2 O 3 + CO = 2FeO + CO 2 (2)
Fe 3 O 4 + CO = 3FeO + CO 2 (3)
FeO + CO = Fe + CO 2 (4)
The reduction reaction shown in the formulas (2) to (4) is a reduction reaction of iron oxide with carbon monoxide CO, which is called an indirect reduction reaction, and is an exothermic reaction except for the reduction reaction shown in the formula (3). It is an exothermic reaction. At the top of the furnace 21, the iron oxide of the ore 2 is mainly Fe 2 O 3 or Fe 3 O 4. Even if the temperature is relatively low, the equations (2) and (3) The reduction reaction shown is easy to occur, and the iron oxide of the ore 2 becomes FeO. Next, as the ore 2 moves downward, the reduction reaction shown in Formula (4) mainly occurs, and the iron oxide of the ore 2 is reduced. In addition, the part of the furnace upper part 21 where the reduction reaction shown in the formulas (2) and (3) mainly occurs is called pre-tropical zone, and the part of the furnace upper part 21 where the reduction reaction shown in the expression (4) mainly occurs is a heat preservation zone. Call it.

非特許文献１には、前記熱保存帯の温度を低下させ、還元反応の効率を向上させ得ることが記載されている。熱保存帯で主に生じる式（４）に示す還元反応は発熱反応であり、一酸化炭素ＣＯガスによる鉄酸化物の還元反応に係るウスタイト（酸化鉄）−鉄還元平衡点を二酸化炭素ＣＯ２ガス濃度が高い方向へ移動させて平衡温度を下げることで、式（４）の還元反応を促進させることができる。 Non-Patent Document 1 describes that the temperature of the thermal preservation zone can be lowered and the efficiency of the reduction reaction can be improved. The reduction reaction represented by the formula (4) mainly occurring in the heat preservation zone is an exothermic reaction, and the wustite (iron oxide) -iron reduction equilibrium point related to the reduction reaction of iron oxide by carbon monoxide CO gas is defined as carbon dioxide CO 2. By reducing the equilibrium temperature by moving the gas concentration in a higher direction, the reduction reaction of the formula (4) can be promoted.

例えば、特許文献１には、前記熱保存帯の温度を低下させる手段として、高反応性コークスであるフェロコークスを用いることが記載されている。コークス３の一部として、フェロコークスを用いることで、次の式に示すコークス３のガス化反応の開始温度を低下させて、熱保存帯の温度を低下させ得る。
Ｃ＋ＣＯ２＝２ＣＯ （５）
特許文献１には、更に、フェロコークスを高炉操業に用いれば、還元された鉄鉱石の触媒効果でコークスの反応性を高めることができるので、上記式（５）を促進させて、還元材の使用量を抑えて、還元材比を低減できる旨が記載されている。 For example, Patent Document 1 describes that ferro-coke, which is highly reactive coke, is used as means for reducing the temperature of the heat preservation zone. By using ferro-coke as a part of the coke 3, the temperature at which the gasification reaction of the coke 3 shown in the following equation is reduced can be lowered, and the temperature of the heat storage zone can be lowered.
C + CO 2 = 2CO (5)
In Patent Document 1, further, if ferro-coke is used for blast furnace operation, the reactivity of coke can be enhanced by the catalytic effect of reduced iron ore. It describes that the amount of reducing material can be reduced by reducing the amount used.

特開２００６−２８５９４号公報JP 2006-28594 A

内藤ら、鉄と鋼、ｖｏｌ．８７（２００１）No.５ 第３５７〜３６４頁Naito et al., Iron and Steel, vol. 87 (2001) No. 5 pp. 357-364

非特許文献１及び特許文献１に記載の技術によって、確かに、高炉での還元反応の効率を向上させ、還元材比を低減させ得る一方で、高炉ガスの熱源として利用価値は低下してしまう。高炉から排出される高炉ガスは、水素Ｈ２や一酸化炭素ＣＯを含み、これらを多く含む方が熱源として利用価値が高い。ところが、還元材比を低下させることによって、一般的には、高炉ガス中の二酸化炭素ＣＯ２の割合が大きくなり、一酸化炭素ＣＯの割合は低下する。なぜならば、還元材比の低下は、コークスや微粉炭などの炭素Ｃを還元材として効率良く使用することを意味し、炭素Ｃが効率良く燃焼すると、二酸化炭素ＣＯ２がより多く生じることになるからである。 While the techniques described in Non-Patent Document 1 and Patent Document 1 can certainly improve the efficiency of the reduction reaction in the blast furnace and reduce the reducing material ratio, the utility value as a heat source for the blast furnace gas decreases. . The blast furnace gas discharged from the blast furnace contains hydrogen H 2 and carbon monoxide CO, and it is more useful as a heat source to contain more of these. However, by reducing the reducing material ratio, in general, the proportion of carbon dioxide CO 2 in the blast furnace gas increases, and the proportion of carbon monoxide CO decreases. This is because a reduction in the reducing material ratio means that carbon C such as coke or pulverized coal is efficiently used as the reducing material, and when carbon C is efficiently burned, more carbon dioxide CO 2 is generated. Because.

高炉ガスの利用価値を高めるという点では、高炉ガスには、二酸化炭素ＣＯ２よりも一酸化炭素ＣＯが多く含まれる方が良く、還元材比の低減を図りつつも、一酸化炭素ＣＯをより多く含む高炉ガスが排出されるように高炉を操業することが求められる場合もある。ところが、非特許文献１や及び特許文献１に記載されている通り、従来技術では、高炉ガス中の一酸化炭素ＣＯの割合は考慮されていないというのが実情である。 In terms of enhancing the utility value of blast furnace gas, it is better that the blast furnace gas contains more carbon monoxide CO than carbon dioxide CO 2 , and carbon monoxide CO is further reduced while reducing the reducing material ratio. It may be required to operate the blast furnace so that a large amount of blast furnace gas is discharged. However, as described in Non-Patent Document 1 and Patent Document 1, in the prior art, the ratio of carbon monoxide CO in the blast furnace gas is not considered.

本発明は上記事情に鑑みてなされたもので、その目的とするところは、還元材比の低減を図りつつも、高炉ガスの熱源としての利用価値を向上させることである。   The present invention has been made in view of the above circumstances, and an object thereof is to improve the utility value of a blast furnace gas as a heat source while reducing the reducing material ratio.

上記課題を解決するための本発明の要旨は以下の通りである。
［１］コークスと鉱石とを高炉に装入する高炉操業方法であって、前記コークスの一部として、該コークスの反応性の指標であるコークス反応性指数ＣＲＩが６５％以上の高反応性コークスを用い、前記鉱石の酸化鉄の被還元性の指標である被還元性指数ＲＩの平均値が５０％以上６５％以下であることを特徴とする高炉操業方法。
［２］前記鉱石として焼結鉱と塊鉱石を用いることとし、前記鉱石中の焼結鉱の割合を調整することによって前記平均値を５０％以上６５％以下とすることを特徴とする上記［１］に記載の高炉操業方法。
［３］前記高反応性コークスの全量または一部を前記鉱石と混合して炉内へ装入することを特徴とする上記［１］または上記［２］に記載の高炉操業方法。 The gist of the present invention for solving the above problems is as follows.
[1] A blast furnace operating method in which coke and ore are charged into a blast furnace, and as a part of the coke, a highly reactive coke having a coke reactivity index CRI of 65% or more, which is an index of reactivity of the coke. And the average value of the reducibility index RI, which is an index of the reducibility of the iron oxide of the ore, is 50% or more and 65% or less.
[2] Sintered ores and lump ores are used as the ores, and the average value is adjusted to 50% to 65% by adjusting the ratio of sintered ores in the ores. The blast furnace operating method according to 1].
[3] The blast furnace operating method according to the above [1] or [2], wherein all or part of the highly reactive coke is mixed with the ore and charged into the furnace.

本発明によれば、反応性が高いコークスを使用して還元材比の低減を図りつつも、高炉ガス中の一酸化炭素の量を多くして、高炉ガスの熱源としての利用価値を向上させることができる。   According to the present invention, the amount of carbon monoxide in the blast furnace gas is increased and the utility value of the blast furnace gas as a heat source is improved while reducing the reducing material ratio using highly reactive coke. be able to.

実験におけるガス組成と雰囲気温度との経時変化を示すグラフである。It is a graph which shows the time-dependent change of the gas composition and atmospheric temperature in experiment. 実験における、通常のコークスを混合した場合Ａと高反応性コークスを混合した場合Ｂとでの還元率を示すグラフである。It is a graph which shows the reduction | restoration rate in A when mixing normal coke in an experiment, and B when mixing highly reactive coke. 実施例における還元材比とガス利用率との散布図である。It is a scatter diagram of the reducing material ratio and gas utilization rate in an Example. 高炉を示す概略図である。It is the schematic which shows a blast furnace.

本発明に係る高炉操業方法では、コークス３の一部として高反応性コークスを用いることで、炉上部２１の熱保存帯にて生じる前述の式（４）に示す間接還元反応を促進させるとともに、炉下部２２での式（１）に示す直接還元反応を抑えて、還元材比の低減を図るものである。しかしながら、還元材比が低下すると、高炉ガス中の一酸化炭素ＣＯの量が低下し、高炉ガスの熱源としての利用価値が低下してしまう傾向がある。   In the blast furnace operating method according to the present invention, by using highly reactive coke as a part of the coke 3, the indirect reduction reaction represented by the above-described formula (4) generated in the heat preservation zone of the furnace upper part 21 is promoted, The direct reduction reaction shown in the equation (1) at the furnace lower part 22 is suppressed to reduce the reducing material ratio. However, when the reducing material ratio decreases, the amount of carbon monoxide CO in the blast furnace gas decreases, and the utility value of the blast furnace gas as a heat source tends to decrease.

そこで、本発明に係る高炉操業方法では、高反応性コークスを用いつつも、鉱石２として、該鉱石２の酸化鉄の被還元性の指標である被還元性指数ＲＩの平均値が５０％以上６５％以下である鉱石を用い、非特許文献１に記載されているように、ウスタイト（鉄酸化物）−鉄還元平衡の平衡温度が下がることに起因した、式（４）に示す間接還元反応の促進する度合いをある程度抑え得る。これにより、還元反応の効率をある程度向上させつつも、高炉ガスに含まれる一酸化炭素ＣＯの低下量も抑え、高炉ガスの熱源としての利用価値の向上を図っている。   Therefore, in the blast furnace operating method according to the present invention, while using highly reactive coke, the average value of the reducibility index RI, which is an index of the reducibility of iron oxide of the ore 2, is 50% or more as the ore 2. As described in Non-Patent Document 1, using an ore that is 65% or less, the indirect reduction reaction represented by the formula (4) caused by the reduction of the equilibrium temperature of the wustite (iron oxide) -iron reduction equilibrium The degree of promotion of can be suppressed to some extent. As a result, while the efficiency of the reduction reaction is improved to some extent, the amount of carbon monoxide CO contained in the blast furnace gas is suppressed, and the utility value of the blast furnace gas as a heat source is improved.

高反応性コークスを使用することで、式（５）に示す炭素Ｃのガス化反応が従来のコークスよりも活発に生じれば、コークスが高炉１に装入された段階から、炉上部２１において更なる一酸化炭素ＣＯガスによる還元促進が期待できる。
Ｃ＋ＣＯ２＝２ＣＯ （５）
この場合、式（５）と、熱保存帯で主に生じる式（４）とに示す間接還元反応が促進される。
ＦｅＯ＋ＣＯ＝Ｆｅ＋ＣＯ２ （４） If the carbon C gasification reaction shown in the formula (5) occurs more actively than the conventional coke by using the highly reactive coke, the coke is charged into the blast furnace 1 and then in the furnace upper part 21. Further reduction promotion by carbon monoxide CO gas can be expected.
C + CO 2 = 2CO (5)
In this case, the indirect reduction reaction shown in Formula (5) and Formula (4) mainly generated in the heat preservation zone is promoted.
FeO + CO = Fe + CO 2 (4)

還元材比を抑えるためには、炉上部２１の熱保存帯で上記式（４）に示す間接還元反応を促進させて、鉱石２の酸化鉄の還元を促進させ、炉下部２２で式（１）に示す直接還元反応を抑えることが望ましい。なぜならば、間接還元反応は発熱反応であり、直接還元反応は吸熱反応であるので、高炉１の全体でみて、間接還元反応が生じる割合が増えると、発熱量が増え、還元材の使用量を抑えることができるからである。   In order to suppress the reducing material ratio, the indirect reduction reaction shown in the above formula (4) is promoted in the heat preservation zone of the furnace upper portion 21 to promote the reduction of iron oxide of the ore 2, and the equation (1 It is desirable to suppress the direct reduction reaction shown in FIG. This is because the indirect reduction reaction is an exothermic reaction, and the direct reduction reaction is an endothermic reaction. Therefore, when the proportion of the indirect reduction reaction increases in the entire blast furnace 1, the calorific value increases and the amount of reducing material used increases. This is because it can be suppressed.

コークス３の反応性の指標としてコークス反応性指数ＣＲＩを採用する。上述の高反応性のコークスは、コークス反応性指数ＣＲＩが６５％以上である。コークス反応性指数ＣＲＩとは、粒径２０±１ｍｍ内のコークス試料２００ｇを１１００℃の温度で二酸化炭素ＣＯ２ガス５ｌ／分を流通させた雰囲気に、２時間保持した後の試料質量の減量分を、反応前の試料質量に対して百分率で示した指数である。コークス反応性指数ＣＲＩが高いほど、コークスは高反応性と評価できる。なお、高反応性コークスとしてフェロコークスを使用する場合には、反応前のフェロコークスの質量から鉱石分を減算して、反応前のフェロコークス中のコークスの質量を算出し、そこから、反応後のコークスの質量を減算して、コークスの減量分を算出し、反応前のコークス分の質量に対する前記減量分の百分率で、コークス反応性指数ＣＲＩを示すこととする。但し、コークス反応性指数ＣＲＩが高すぎると、やはり、高炉ガス中の一酸化炭素の量が減少してしまうので、高反応性のコークスのコークス反応性指数ＣＲＩは８５％以下とすることが好ましい。 The coke reactivity index CRI is employed as an index of coke 3 reactivity. The above-described highly reactive coke has a coke reactivity index CRI of 65% or more. The coke reactivity index CRI is a decrease in the mass of a sample after being held for 2 hours in an atmosphere in which 200 g of a coke sample having a particle size of 20 ± 1 mm was circulated at a temperature of 1100 ° C. and 5 l / min of carbon dioxide CO 2 gas. Is an index indicating the percentage of the sample mass before the reaction. The higher the coke reactivity index CRI, the higher the coke can be evaluated. When using ferro-coke as highly reactive coke, subtract the ore content from the ferro-coke mass before the reaction to calculate the mass of coke in the ferro-coke before the reaction. The amount of coke reduced is calculated by subtracting the mass of coke, and the coke reactivity index CRI is expressed as a percentage of the amount of the reduced coke relative to the mass of the coke before the reaction. However, if the coke reactivity index CRI is too high, the amount of carbon monoxide in the blast furnace gas will also decrease. Therefore, the coke reactivity index CRI of highly reactive coke is preferably 85% or less. .

上述の高反応性コークスを用いると、非特許文献１に記載されているように、ウスタイト（鉄酸化物）−鉄還元平衡の平衡温度を下げることに起因して、熱保存帯で、前述の式（４）の間接還元反応が促進されすぎてしまい、高炉ガス中の一酸化炭素の量が低下し、高炉ガスの熱源としての利用価値が低下してしまう傾向がある。そこで、本発明者らは、鉱石２の全量を、被還元性指数ＲＩの平均値がある程度の範囲として、高反応性コークスを用いつつも、式（４）の間接還元反応が促進されにくくすることに着想し、式（４）の間接還元反応をある程度抑えて、高炉ガス中の一酸化炭素の量の低下を防ぎ得ることを見出した。ここで、被還元性指数ＲＩとは、ＪＩＳ Ｍ８７１３−１９９３の「鉄鉱石−還元試験方法」に規定される方法１（還元率法：ＩＳＯ７２１５による方法）に基づいて測定した指数であり、鉱石の被還元指数ＲＩが大きい程、鉱石は還元されやすいことを意味する。この平均値とは、鉱石として使用される焼結鉱や塊鉱石などの鉱石原料の被還元性指数ＲＩを、配合割合を重みとして加重平均して求めた値である。非特許文献１には、通常のコークスの使用下において、ＲＩが７０以上の高被還元性焼結鉱を使用することで、炉内反応効率を向上させる操業が提案されている。   When the above-mentioned highly reactive coke is used, as described in Non-Patent Document 1, due to lowering the equilibrium temperature of wustite (iron oxide) -iron reduction equilibrium, The indirect reduction reaction of Formula (4) is promoted too much, the amount of carbon monoxide in the blast furnace gas tends to decrease, and the utility value of the blast furnace gas as a heat source tends to decrease. Therefore, the present inventors make the total amount of ore 2 less likely to promote the indirect reduction reaction of formula (4) while using the highly reactive coke with the average value of the reducible index RI being within a certain range. In particular, the inventors have found that the indirect reduction reaction of formula (4) can be suppressed to some extent to prevent a decrease in the amount of carbon monoxide in the blast furnace gas. Here, the reducible index RI is an index measured based on Method 1 (reduction rate method: method according to ISO7215) defined in “Iron Ore-Reduction Test Method” of JIS M8713-1993. It means that the ore is more easily reduced as the reducible index RI is larger. This average value is a value obtained by weighted averaging the reducibility index RI of an ore raw material such as sintered or massive ore used as ore with the blending ratio as a weight. Non-Patent Document 1 proposes an operation for improving the in-furnace reaction efficiency by using a highly reducible sintered ore having an RI of 70 or more under the use of ordinary coke.

本発明では、鉱石２の被還元性の指標として前述の被還元性指数ＲＩを採用し、鉱石２として、被還元性指数ＲＩの平均値が５０％以上６５％以下である鉱石を用いる。鉱石２の被還元性指数ＲＩの平均値が低すぎると高炉全体としての還元停滞に繋がり、生産量を維持するためには還元材比を増加させる必要が生じるため、５０％以上とすることが好ましい。また、６５％以下であれば、高炉ガス中の一酸化炭素ＣＯの割合をある程度維持することができる。   In the present invention, the above-described reducibility index RI is used as an index of the reducibility of the ore 2, and an ore having an average value of the reducibility index RI of 50% to 65% is used as the ore 2. If the average value of the reducibility index RI of the ore 2 is too low, it will lead to stagnation of the reduction of the entire blast furnace, and it will be necessary to increase the reducing material ratio in order to maintain the production amount. preferable. Moreover, if it is 65% or less, the ratio of carbon monoxide CO in blast furnace gas can be maintained to some extent.

コークス反応性指数ＣＲＩが３０％である通常のコークスで、被還元性指数ＲＩの平均値が７０％となる鉱石の酸化鉄を還元した場合Ａと、コークス反応性指数ＣＲＩが６５％となる高反応性コークスで、被還元性指数ＲＩの平均値が５０％となる鉱石の酸化鉄を還元した場合Ｂと、において、還元反応の後に生じるガス中の一酸化炭素ＣＯと二酸化炭素ＣＯ２の割合の推移と、鉱石の酸化鉄の還元率と、を比較する実験を行った。該実験では、コークス反応性指数ＣＲＩ及び被還元性指数ＲＩは、前述に記載の方法で調整してある。また、実験では、高炉の炉上部２１において原料が降下して熱保存帯に至るまでの雰囲気温度を電気炉で模擬すると共に、模擬したそれぞれの位置（時間）での炉内ガス組成を模擬して、還元反応を生じさせることとした。模擬した雰囲気温度及びガス組成の経時変化を図１に示す。 When normal iron coke with a coke reactivity index CRI of 30% and iron oxide of ore with an average value of the reducible index RI of 70% is reduced, the coke reactivity index CRI is 65%. The ratio of carbon monoxide CO and carbon dioxide CO 2 in the gas produced after the reduction reaction in reactive coke when iron oxide of ore with an average reducibility index RI of 50% is reduced An experiment was conducted to compare the transition of iron and the reduction rate of iron oxide in the ore. In the experiment, the coke reactivity index CRI and the reducibility index RI are adjusted by the method described above. In the experiment, the atmosphere temperature from when the raw material descends to the heat preservation zone in the furnace upper part 21 of the blast furnace is simulated with an electric furnace, and the gas composition in the furnace at each simulated position (time) is simulated. Thus, a reduction reaction was caused. FIG. 1 shows changes in simulated atmosphere temperature and gas composition over time.

場合Ａ及び場合Ｂにおける雰囲気温度１０００℃での鉱石の酸化鉄の還元率を図２に示す。還元率は次の式（６）で算出した。
還元率＝（１−（反応前の鉱石の酸化鉄中の酸素量−反応後の質量減少量）／反応前の鉱石の酸化鉄中の酸素量）×１００ （６）
図２から、場合Ａ（通常コークスの混合）と場合Ｂ（高反応性コークスの混合）とでは、鉱石の還元率が同等であり、還元性が低くても高反応性コークスと組み合わせることにより１０００℃以下での還元は進行することがわかった。また、図１から、雰囲気温度１０００℃以下の環境では、場合Ａ（通常コークスの混合）よりも場合Ｂ（高反応性コークスの混合）の方が、ガス中の二酸化炭素ＣＯ２の発生量が抑えられ、一酸化炭素ＣＯの発生量が多くなっていることがわかる。コークス反応性指数ＣＲＩが高い高反応性コークスで、被還元性指数ＲＩの平均値が低い鉱石の酸化鉄を還元する還元反応では、還元率をある程度維持しつつも、一酸化炭素ＣＯの発生量をある程度多く発生させ得ることがわかる。 FIG. 2 shows the reduction rate of the iron oxide of the ore at the atmospheric temperature of 1000 ° C. in the case A and the case B. The reduction rate was calculated by the following formula (6).
Reduction rate = (1- (the amount of oxygen in the iron oxide of the ore before the reaction−the amount of decrease in mass after the reaction) / the amount of oxygen in the iron oxide of the ore before the reaction) × 100 (6)
From FIG. 2, in case A (mixing of ordinary coke) and case B (mixing of highly reactive coke), the reduction rate of the ore is equivalent, and even when the reducing property is low, it is 1000 by combining with highly reactive coke. It was found that the reduction at a temperature below 0 ° C proceeded. Also, from FIG. 1, in an environment where the ambient temperature is 1000 ° C. or less, the amount of carbon dioxide CO 2 in the gas generated in the case B (mixed highly reactive coke) is higher than the case A (mixed normal coke). It can be seen that the amount of carbon monoxide CO generated is increased. In a reduction reaction that reduces iron oxide in ore with a high coke reactivity index CRI and a high average value of the reducibility index RI, the amount of carbon monoxide CO generated while maintaining the reduction rate to some extent It can be seen that a large amount of can be generated.

鉱石として焼結鉱と塊鉱石を用いることとし、鉱石中の焼結鉱の割合を調整することによって、鉱石の被還元性指数ＲＩの平均値を５０％以上６５％以下とすることが好ましい。焼結鉱は被還元性が高く、鉱石中の焼結鉱の割合を減少させ、比較的被還元性の低い塊鉱石の割合を増加させると、被還元性指数ＲＩの平均値を変更しやすい。また、焼結鉱と塊鉱石との鉱石中の割合を一定としつつも、焼結鉱や塊鉱石の被還元性指数ＲＩを低下させてもよい。   It is preferable that the average value of the reducibility index RI of the ore be 50% or more and 65% or less by using sintered ore and lump ore as the ore and adjusting the ratio of the sintered ore in the ore. Sintered ore is highly reducible, and if the ratio of sintered ore in the ore is decreased and the ratio of relatively low reducible massive ore is increased, the average value of the reducible index RI can be easily changed. . Further, the reducibility index RI of the sintered ore or massive ore may be lowered while the ratio of the sintered ore and massive ore in the ore is constant.

高反応性コークスとしてフェロコークスがあるが、このほかに、高カルシウム炭から製造した高反応性コークスや、ダスト類とコークス粉とをバインダーで固めたコールドペレットも高反応性コークスとして用いることができる。これらを高反応性コークスに用いても、高炉の炉上部で低温からコークスの反応を開始させることができる。   Ferro-coke is a highly reactive coke, but in addition to this, highly reactive coke produced from high calcium coal and cold pellets in which dusts and coke powder are hardened with a binder can also be used as highly reactive coke. . Even if these are used for highly reactive coke, the reaction of coke can be started from a low temperature in the upper part of the blast furnace.

本発明では高炉で使用するコークスの一部を高反応性コークスとするときに生じるガス利用率の上昇に対して鉱石の被還元性指数ＲＩを適正に維持することで効果を得ることができるが、特に高反応性コークスを１０ｋｇ／トン−銑鉄以上使用するときには上記ガス利用率の上昇が顕在化することが多いため、高反応性コークスを１０ｋｇ／トン−銑鉄以上使用するときに実施することが好ましい。ただし、高反応性コークスは、通常のコークスに比べて炉下部での反応による強度劣化が生じやすいので、高炉内の通気の安定の観点からは炉頂から装入するコークスの内の５０質量％以下とすることがより好ましい。   In the present invention, an effect can be obtained by appropriately maintaining the reducibility index RI of the ore against the increase in gas utilization rate that occurs when a part of the coke used in the blast furnace is made highly reactive coke. In particular, when the high-reactivity coke is used in an amount of 10 kg / tonne-iron or more, the increase in the gas utilization rate is often manifested. preferable. However, since highly reactive coke is more susceptible to strength deterioration due to reaction at the lower part of the furnace than normal coke, 50% by mass of coke charged from the top of the furnace from the viewpoint of stable ventilation in the blast furnace. More preferably, it is as follows.

鉱石の被還元性指数を下げることは、高炉全体としての還元停滞に繋がり、生産性を悪化させる可能性があるため、鉱石の平均被還元性指数は５０以上を維持することが望ましい。   Lowering the ore reducibility index leads to reduction stagnation of the entire blast furnace and may deteriorate productivity, so it is desirable to maintain the average ore reducibility index of 50 or more.

高反応性コークスの全量または一部を鉱石と混合して操業することが好ましい。高反応性コークスが鉱石に混合されていると、鉱石層の内部で高反応性コークスのガス化反応で発生した一酸化炭素ＣＯのガスが、近傍にある鉱石を還元し、さらに高反応性コークスのガス化に利用されるといった反応の循環が起こり易くなるので、炉上部での還元反応がより促進されることになる。また、図４にて、鉱石２とコークス３とを積層した状態で高炉１に装入されている形態を示してあるが、本発明は必ずしもこの形態に限定されるものではなく、高炉での一部に、鉱石２とコークス３とを積層した状態ではなく、高反応性コークスの全量または一部を鉱石と混合してある層が複数あっても、前述の通り、炉上部２１において式（４）に示される間接還元反応を促進させ得る。   It is preferable to operate by mixing all or part of the highly reactive coke with the ore. When highly reactive coke is mixed with ore, carbon monoxide CO gas generated by the gasification reaction of highly reactive coke inside the ore layer reduces the ore in the vicinity and further increases the highly reactive coke. Since the circulation of the reaction such as being used for gasification of the gas easily occurs, the reduction reaction in the upper part of the furnace is further promoted. Moreover, in FIG. 4, although the form currently charged in the blast furnace 1 in the state which laminated | stacked the ore 2 and the coke 3 is shown, this invention is not necessarily limited to this form, Even if there are a plurality of layers in which the ore 2 and the coke 3 are not laminated, and there are a plurality of layers in which all or a part of the highly reactive coke is mixed with the ore, the formula ( The indirect reduction reaction shown in 4) can be promoted.

以上の通り、コークス反応性指数ＣＲＩが６５％以上の高反応性コークスを用いて、炉上部２１で間接還元反応（式（４））を進行させ、炉下部２２での吸熱反応である直接還元反応（式（１））を抑えれば、高炉全体としては、還元材比の低減が可能となる。また、前記高反応性コークスを用いると同時に、鉱石の酸化鉄の被還元性の指標である被還元性指数ＲＩの平均値が５０％以上６５％以下である鉱石を用いれば、還元材比の低減を図りつつも、間接還元反応（式（４））の過剰な促進を抑え、高炉ガス中の一酸化炭素量の低下をある程度抑え得ることが期待される。   As described above, using a highly reactive coke having a coke reactivity index CRI of 65% or more, an indirect reduction reaction (formula (4)) is caused to proceed in the furnace upper part 21 and a direct reduction that is an endothermic reaction in the furnace lower part 22. If the reaction (formula (1)) is suppressed, the reducing material ratio can be reduced as the entire blast furnace. In addition, when using the ore having the average value of the reducibility index RI, which is an index of the reducibility of the iron oxide of the ore, at the same time as using the highly reactive coke, the ratio of the reducing material is reduced. While aiming at reduction, it is expected that excessive promotion of the indirect reduction reaction (formula (4)) can be suppressed and a decrease in the amount of carbon monoxide in the blast furnace gas can be suppressed to some extent.

図４に示す高炉１の操業において、本発明を実施した。該高炉１の内容積は５０００ｍ３である。高炉操業において、銑鉄９の温度が１５００［℃］で出銑比が２．２［トン−銑鉄／（日・ｍ３）］となるように、高炉１に鉱石２及びコークス３を投入し、微粉炭を１５２［ｋｇ／トン−銑鉄］で羽口５から吹き込んだ。標準となる高炉操業を行うために、コークス３としては、高反応性コークスを用いずに通常のコークスのみを用いた。通常のコークスのコークス反応性指数ＣＲＩは３０％である。鉱石２としては、焼結鉱と塊鉱石を用いて、還元性指数ＲＩの平均値を６７％とした（ベース）。 The present invention was implemented in the operation of the blast furnace 1 shown in FIG. The internal volume of the blast furnace 1 is 5000 m 3 . In blast furnace operation, ore 2 and coke 3 are introduced into the blast furnace 1 so that the temperature of the pig iron 9 is 1500 [° C.] and the output ratio is 2.2 [ton-pig iron / (day · m 3 )] Pulverized coal was blown from the tuyere 5 at 152 [kg / ton-pig iron]. In order to perform standard blast furnace operation, as the coke 3, only normal coke was used without using highly reactive coke. A normal coke has a coke reactivity index CRI of 30%. As ore 2, sintered ore and lump ore were used, and the average value of reducing index RI was set to 67% (base).

また、鉱石２の焼結鉱と塊鉱石との割合を変更して、還元性指数ＲＩの平均値を変更し、かつ、コークス３の一部に用いる高反応性コークスとして、適宜、コークス反応性指数ＣＲＩを変更したフェロコークスを用いた以外はベースの高炉操業と同じ条件で、高炉操業を行った（本発明例１〜４及び比較例１，２）。該フェロコークスは、石炭と鉱石の混合物をブリケットマシンで成型後、竪型シャフト炉に装入し乾留して製造し、その寸法は３０×２５×１８ｍｍのピロー型である。フェロコークス中の鉄分は３０質量％とした。コークス反応性指数ＣＲＩは、前述の実施形態で記載した方法によって測定し、還元性指数ＲＩは、ＪＩＳ Ｍ８７１３−１９９３に規定される方法に準拠して測定した。本発明例１〜４及び比較例１，２において、フェロコークスを鉱石２に混合した。   Further, the ratio of the sintered ore of the ore 2 and the lump ore is changed to change the average value of the reducibility index RI, and as a highly reactive coke used for a part of the coke 3, the coke reactivity is appropriately selected. The blast furnace operation was performed under the same conditions as the base blast furnace operation except that the ferro-coke with the index CRI changed was used (Invention Examples 1 to 4 and Comparative Examples 1 and 2). The ferro-coke is produced by molding a mixture of coal and ore with a briquette machine, charging it into a vertical shaft furnace and dry-distilling, and its dimensions are 30 × 25 × 18 mm pillow type. The iron content in ferro-coke was 30% by mass. The coke reactivity index CRI was measured by the method described in the above embodiment, and the reducing index RI was measured according to the method defined in JIS M8713-1993. In Invention Examples 1 to 4 and Comparative Examples 1 and 2, ferrocoke was mixed with ore 2.

ベースの高炉操業及び本発明例１〜４と比較例１，２の高炉操業における操業条件及び還元材比とガス利用率との結果を表１に示す。   Table 1 shows the results of operating conditions, reducing material ratio, and gas utilization rate in the base blast furnace operation and the inventive blast furnace operations 1 to 4 and Comparative Examples 1 and 2.

Figure 2016050323
Figure 2016050323

表１におけるガス利用率は、高炉ガスに含まれる二酸化炭素ＣＯ２と一酸化炭素ＣＯとの合計量に対する二酸化炭素ＣＯ２の量の割合を意味し、ＣＯ２（％）／［ＣＯ２（％）＋ＣＯ（％）］で表される値である。ガス利用率が低い方が、高炉ガスに一酸化炭素ＣＯが多く含まれていることを意味する。 The gas utilization rate in Table 1 means the ratio of the amount of carbon dioxide CO 2 to the total amount of carbon dioxide CO 2 and carbon monoxide CO contained in the blast furnace gas, CO 2 (%) / [CO 2 (% ) + CO (%)]. A lower gas utilization rate means that the blast furnace gas contains more carbon monoxide CO.

本発明では、還元材比の低減を図りつつも、高炉ガス中の一酸化炭素の量を上昇させることを目的とするため、少なくとも、本発明を満たす本発明例１〜４では、ベースの高炉操業の還元材比を基準とし、該基準に対して還元材比が低下し、その低下幅に対して、ベースの高炉操業のガス利用率を基準としてガス利用率が上昇する割合が抑えられていることが望ましい。よって、表１には、ベースの高炉操業の還元材比から、本発明例１〜４と比較例１，２の還元材比を減算して得られる還元材比の低下量を記載し、本発明例１〜４と比較例１，２のガス利用率から、ベースの高炉操業のガス利用率を減算して得られるガス利用率の上昇量を記載し、ガス利用率の上昇量／還元材比の低下量を記載してある。ガス利用率の上昇量が小さく還元材比の低下量が大きい、すなわち、ガス利用率の上昇量／還元材比の低下量の値が小さいほど、還元材比の低減を図りつつ、高炉ガス中の一酸化炭素量の低下幅を効果的に抑えていることを意味する。なお、参考として、ベースの高炉操業及び本発明例１〜４と比較例１，２の高炉操業における還元材比とガス利用率との散布図を図３に示す。   The present invention aims at increasing the amount of carbon monoxide in the blast furnace gas while reducing the reducing material ratio. Therefore, at least in the present invention examples 1 to 4 satisfying the present invention, the base blast furnace Based on the ratio of reducing material in operation, the ratio of reducing material decreases with respect to the standard, and the rate of increase in gas utilization rate based on the gas utilization rate of the base blast furnace operation is suppressed with respect to the reduction range. It is desirable. Therefore, Table 1 describes the reduction amount of the reducing material ratio obtained by subtracting the reducing material ratios of Examples 1 to 4 and Comparative Examples 1 and 2 from the reducing material ratio of the base blast furnace operation. The amount of increase in gas utilization rate obtained by subtracting the gas utilization rate of the base blast furnace operation from the gas utilization rates of Invention Examples 1 to 4 and Comparative Examples 1 and 2 is described, and the amount of increase in gas utilization rate / reducing material The amount of decrease in the ratio is described. The amount of increase in the gas utilization rate is small and the amount of reduction in the reducing material ratio is large. That is, the smaller the value of the gas utilization rate increasing amount / the amount of reduction in the reducing material ratio is, the more the reducing material ratio is reduced. This means that the amount of decrease in the amount of carbon monoxide is effectively suppressed. As a reference, FIG. 3 shows a scatter diagram of the reducing material ratio and gas utilization rate in the blast furnace operation of the base and the inventive blast furnace operations of Examples 1 to 4 and Comparative Examples 1 and 2.

本発明例１〜４では、ガス利用率の上昇量／還元材比の低下量の値が小さく、ベースの高炉操業と比べて、還元材比を低減した上で、高炉ガス中の一酸化炭素量の低下を抑え、高炉ガスに一酸化炭素量を多くできたことがわかる。   In Invention Examples 1 to 4, the amount of increase in the gas utilization rate / the amount of reduction in the reducing material ratio is small, and compared with the base blast furnace operation, the reducing material ratio is reduced, and then carbon monoxide in the blast furnace gas It can be seen that the amount of carbon monoxide was increased in the blast furnace gas by suppressing the decrease in the amount.

還元性指数ＲＩの平均値を６７％となる鉱石２を使用しつつ、フェロコークスを用いた比較例１では、ベースの高炉操業と比べて還元材比を大幅に低下させることには成功しているが、本発明例１〜４に比べると、ガス利用率も大幅に上昇しており、高炉ガス中の一酸化炭素量の低下している。よって、高炉ガスの熱源としての利用価値は低下していることがわかる。   In Comparative Example 1 using ferro-coke while using ore 2 with an average value of the reducing index RI of 67%, it has succeeded in significantly reducing the reducing material ratio compared to the base blast furnace operation. However, compared with Examples 1-4 of the present invention, the gas utilization rate has also increased significantly, and the amount of carbon monoxide in the blast furnace gas has decreased. Therefore, it turns out that the utility value as a heat source of blast furnace gas is falling.

還元性指数ＲＩの平均値を４８％となる鉱石２を使用した比較例２では、ベースの高炉操業と比べて、ガス利用率を低下させることには成功しているが、生産量を維持するべく操業するために、還元材比が上昇してしまっている。   In Comparative Example 2 using ore 2 having an average value of the reducing index RI of 48%, the gas utilization rate was successfully reduced as compared with the base blast furnace operation, but the production amount was maintained. In order to operate as much as possible, the ratio of reducing materials has increased.

比較例２では、ガス利用率の上昇量／還元材比の低下量の値を算出できなかった一方で、比較例１においては、前記値が０．０８２４と算出された。比較例１に対して、本発明例１〜４では前記値は０．０３以下と算出され、還元材比の低減を図りつつガス利用率の上昇幅を抑えられていることがわかる。この結果からすれば、本発明によって、反応性が高いコークスを使用して還元材比の低減を図りつつも、ガス利用率の上昇幅を抑えることで高炉ガス中の一酸化炭素の量を多くして、高炉ガスの熱源としての利用価値を向上できることがわかる。   In Comparative Example 2, the value of the gas utilization rate increase / reducing material ratio decrease could not be calculated, while in Comparative Example 1, the value was calculated to be 0.0824. Compared to Comparative Example 1, in Examples 1 to 4 of the present invention, the value is calculated to be 0.03 or less, and it is understood that the increase rate of the gas utilization rate is suppressed while reducing the reducing material ratio. According to this result, the present invention increases the amount of carbon monoxide in the blast furnace gas by suppressing the rate of increase in the gas utilization rate while reducing the reducing material ratio by using highly reactive coke. Thus, it can be seen that the utility value of the blast furnace gas as a heat source can be improved.

１ 高炉
２ 鉱石
３ コークス
４ 融着帯
５ 羽口
６ 熱風
７ 出銑口
８ 溶滓
９ 銑鉄
２１ 炉上部
２２ 炉下部 DESCRIPTION OF SYMBOLS 1 Blast furnace 2 Ore 3 Coke 4 Cohesive zone 5 Feather 6 Hot air 7 Outlet 8 Hot metal 9 Pig iron 21 Furnace upper part 22 Furnace lower part

Claims (3)

コークスと鉱石とを高炉に装入する高炉操業方法であって、
前記コークスの一部として、該コークスの反応性の指標であるコークス反応性指数ＣＲＩが６５％以上の高反応性コークスを用い、
前記鉱石の酸化鉄の被還元性の指標である被還元性指数ＲＩの平均値が５０％以上６５％以下であることを特徴とする高炉操業方法。 A blast furnace operating method for charging coke and ore into a blast furnace,
As a part of the coke, a highly reactive coke having a coke reactivity index CRI of 65% or more, which is an index of the reactivity of the coke,
A blast furnace operating method, wherein an average value of a reducibility index RI which is an index of reducibility of iron oxide of the ore is 50% or more and 65% or less. 前記鉱石として焼結鉱と塊鉱石を用いることとし、
前記鉱石中の焼結鉱の割合を調整することによって前記被還元性指数ＲＩの平均値を５０％以上６５％以下とすることを特徴とする請求項１に記載の高炉操業方法。 Sintered ore and lump ore will be used as the ore,
2. The blast furnace operating method according to claim 1, wherein an average value of the reducibility index RI is set to 50% or more and 65% or less by adjusting a ratio of sintered ore in the ore. 前記高反応性コークスの全量または一部を前記鉱石と混合して炉内へ装入することを特徴とする請求項１または請求項２に記載の高炉操業方法。   The blast furnace operating method according to claim 1 or 2, wherein the whole or part of the highly reactive coke is mixed with the ore and charged into the furnace.
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EP3992308A1 (en) * 2018-03-30 2022-05-04 JFE Steel Corporation Method for charging raw materials into blast furnace
CN113640173A (en) * 2021-09-15 2021-11-12 鞍钢股份有限公司 Coke degradation evaluation method under simulated blast furnace dynamic reaction
CN115494895A (en) * 2022-09-19 2022-12-20 国能神东煤炭集团有限责任公司 Method and device for simulating blast furnace molten iron carburization

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