JP2003119522A - Treated ore for blast furnace - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a treated blast furnace ore that contributes to a significant improvement in blast furnace operation, that is, an improvement in productivity and a decrease in fuel ratio. SOLUTION: A core made of a mixture containing an iron oxide-containing substance and a carbon-containing substance is formed by being covered with an outer shell containing the iron oxide-containing substance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blast furnace treated ore used as a blast furnace charging raw material, which contributes to a reduction in fuel ratio and an increase in productivity in a blast furnace.

[0002]

2. Description of the Related Art In a blast furnace, various raw materials are charged inside to produce pig iron which is a raw material for steel products. In this blast furnace, massive iron ore, sinter, and pellets are mainly used as an iron source, and they are charged into the blast furnace from the top of the furnace. In special cases, reduced iron or scrap may be used. On the other hand, coke is mainly used as the reducing agent and the fuel, which is also charged from the furnace top. Furthermore, it is also common to blow pulverized coal, natural gas, tar, etc. from the tuyere of the blast furnace as a partial substitute for the reducing material and the fuel.

In such a blast furnace operation, improvement of productivity and reduction of fuel consumption ratio lead to reduction of facility cost and operating cost in the hot metal cost, and expansion of operating range of the blast furnace. This leads to economically favorable results.

Sintered ore, pellets or lumpy iron ore, which has been the main raw material of iron used up to now, is reduced by the reaction with the gas in the furnace in the blast furnace. In order to carry out sufficient reduction, it is necessary to lengthen the contact time with the gas in the furnace. If productivity is expected and the contact time with the in-furnace gas is shortened, the utilization efficiency of the in-furnace gas for reduction is reduced, and the fuel ratio tends to increase.

Here, among the iron sources used, sinter ore and pellets are called treated ores, and by devising the manufacturing technology of these treated ores to improve the reducibility of the treated ores, they can be processed in the blast furnace. Has been attempted to improve the reactivity of the fuel, improve productivity, and reduce the fuel ratio.

For example, regarding the manufacturing technology of pellets,
In Kaihei 2-280522, pellets are attached to the core and the outside.
It has a double structure with the peripheral part, and CaO is present in the core part and the outer peripheral part.
/ SiO ₂Intentionally make the difference in the value of
Technology has been published. In addition, it is a reducing agent or fuel.
With regard to coke, the reactivity of blast furnace can be improved by increasing the reactivity.
It aims to improve productivity and reduce the fuel ratio.

[0007] However, the above-mentioned technique is focused on increasing the reactivity, and the mechanism itself for reducing ore by reaction with the gas in the furnace is the same as before. Improved productivity,
And it was difficult to face the decrease in fuel ratio.

[0008]

Therefore, the present invention is
It is an object of the present invention to provide a treated ore for blast furnace, which contributes to a great improvement in blast furnace operation, that is, an improvement in productivity and a reduction in fuel ratio.

[0009]

That is, the present invention is
It is a blast furnace treatment ore comprising a core made of a mixture containing an iron oxide-containing substance and a carbon-containing substance covered with an outer shell containing the iron oxide-containing substance.

The blast furnace treated ore according to the present invention is characterized in that the iron oxide-bonded oxygen mole number (X) in the iron oxide-containing substance in the core is
The total number of moles of carbon in the carbon-containing substance in the nucleus (Y) and the number of moles of oxygen bound to iron oxide in the iron-oxide-containing substance in the outer shell (Z)
It is preferable that and satisfy the following formulas (1) to (3). Note 0.5 ≦ Y / X ≦ 1.2 ---- (1) Y / (X + Z) ≧ 0.3 ---- (2) 0.6 ≦ Z / X ---- (3)

Further, at least one of the nucleus and the outer shell contains at least one selected from CaO, CaCO ₃ , Ca (OH) ₂ , MgO, MgCO ₃ and Mg (OH) ₂ , and a powder metal. Advantageously, each contains iron. In addition,
In the present invention, the nucleus means a portion containing a carbon-containing substance inside the blast furnace treated ore.

Here, the carbon-containing substance is a substance capable of reducing iron oxide contained in the iron oxide-containing substance at a predetermined temperature, such as carbonaceous materials such as coal and coke and various organic substances, and carbonates. And the like, which have only carbon forms that do not directly contribute to the reduction reaction.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The blast furnace ore of the present invention will be described in detail below. That is, the treated ore for blast furnace of the present invention includes a core 1 made of a mixture containing an iron oxide-containing substance and a carbon-containing substance, and an iron oxide-containing substance covering the nucleus 1 as shown in a half cut surface in FIG. It is characterized by comprising an outer shell 2. Hereinafter, the treated ore having a structure according to the present invention will be referred to as a carbonaceous material-containing double ore.

When the carbon-containing double ore is heated, its core 1 contains an iron oxide-containing substance and a carbon-containing substance, so that the iron oxide in contact with the carbon-containing substance is FeOx + xC = Fe + xCO ---- (i) is reduced and CO gas is generated. The CO gas thus generated becomes CO ₂ gas by the reaction of iron oxide in the nucleus 1 with FeOx + xCO = Fe + xCO ₂ ---- (ii). At this time, since carbon from the carbon-containing substance is contained in the nucleus 1, a gasification reaction of C by CO ₂ of C + CO ₂ = 2CO ---- (iii) occurs.

Here, the CO and CO ₂ gas generated and consumed are those produced from the iron oxide-bound oxygen in the iron oxide-containing substance of nucleus 1 and the carbon in the carbon-containing substance of nucleus 1, and carbonaceous material. Not affected by the gas atmosphere outside the interior double mine. When the reactions of these equations (i), (ii) and (iii) are added together, FeOx + xC = Fe + xCO ---- (iv), which is a CO gas generation reaction. This CO gas passes through the outer shell 2 of the carbon material-containing double ore and goes out of the carbon material-containing double ore. At this time, since the outer shell 2 contains the iron oxide-containing substance, the CO gas passing through the outer shell 2 and the outer shell 2
A reaction occurs with the iron oxide contained therein, and as shown in the following formula (v), the iron oxide portion of the outer shell 2 is also reduced. FeOx (iron oxide in the outer shell) + xCO (CO gas that passes through the outer shell) = Fe + xCO ₂ ---- (v)

The above reaction amount in the outer shell depends on temperature conditions (average temperature, particle temperature distribution), thickness of outer shell layer (amount of iron oxide).
The amount of nuclei or the ratio of iron oxide in the nuclei to carbon in the carbon-containing substance changes, but basically there is no difference that CO generated in the nuclei can be used for reduction in the outer shell.

Here, the characteristics of the above-mentioned double mine containing carbonaceous material are
Compare with normal sinter or pellets. By the way, it is customary that the sinter or pellets, which are the main source of iron in the current blast furnace, do not substantially contain carbonaceous materials which themselves can serve as reducing agents. These raw materials are reduced in the blast furnace and eventually melt down and become hot metal. Reduction is CO generated by combustion of coke, pulverized coal, etc. in the raceway in the blast furnace.
It is done by contact with gas (partly H ₂ gas),
In order to reduce the inside of the particles, CO gas needs to diffuse into the particles, and the diffusion resistance delays the reaction.

On the other hand, since the carbon material-containing double ore contains the carbon-containing substance in the core as described above,
CO gas is generated in the nucleus and is used for the reduction of iron oxide in the immediate vicinity, resulting in an extremely fast reaction.

On the other hand, although pellets mixed with carbonaceous material (briquette) may be used, since this type of carbonaceous material-containing pellets is obtained by mixing carbonaceous material, it can be used anywhere in the particle. Substantially, the compounding ratio of the carbon-containing substance and iron oxide is uniform, and therefore the carbonaceous material is also contained in the surface layer portion of the pellet. When carbonaceous material is present in the surface layer, a reaction of C + CO ₂ = 2CO occurs in the carbonaceous material portion, and the gas released outside the carbonaceous material-containing pellet particles contains a large amount of CO.

On the other hand, in the carbonaceous material-containing double ore, since the outer shell contains no carbonaceous material as described above, the outer shell can reduce the iron oxide by using the CO gas generated in the nucleus. Done. As a result, compared to the conventional pellets containing carbonaceous material, the gas outside the particles has less CO. This is a carbon material interior 2
Heavy ore means higher gas utilization in the blast furnace.

As described above, the carbonaceous material-containing double ore has a faster reduction reaction rate than the sintered ore and pellets, and uses gas when used in the blast furnace as compared with conventional pellets containing carbonaceous material. The rate can be increased.

Furthermore, in the carbonaceous material-containing double ore, the number of moles of oxygen bound to iron oxide in the iron oxide-containing substance in the nucleus (X) and the total number of moles of carbon in the carbon-containing substance in the nucleus (Y) are the same. And the iron oxide-bonded oxygen mole number (Z) in the iron oxide-containing substance in the outer shell
By maintaining the relationship of the following equations (1) to (3), the gas when used in a blast furnace while maintaining the property that the reduction reaction rate is faster than that of sinter or pellets. The utilization rate can be further improved. 0.5 ≦ Y / X ≦ 1.2 ---- (1) Y / (X + Z) ≧ 0.3 ---- (2) 0.6 ≦ Z / X ---- (3)

In a blast furnace operation using sinter or pellets, the ore is reduced by the reducing gas generated in the raceway, so at most FeO can be obtained while the ore descends from the top of the blast furnace to the preservation zone. It is theoretically known that it can only be reduced up to and therefore metallic iron is not formed up to this stage. This is how to improve the reducibility of sinter or pellets. In order to improve the productivity of the blast furnace (improve the production amount per unit volume of the furnace), this point must be fundamentally solved.

In the case of carbon material-containing double ore, iron oxide in the core is reduced by the carbon in the carbon-containing substance contained in the core, so that the stage from the top of the blast furnace to the preservation zone is reduced. It is possible to produce metallic iron. Regarding the relationship between carbon and iron oxide in the nucleus, metallic iron is produced at the stoichiometric theoretical value of Y / X ≧ 0.33 with respect to the above X and Y. Since the materials are unevenly distributed, metallic iron is generated even below the theoretical value. However, in order to produce an effective amount of metallic iron, it was found by the experiments described later that Y / X ≧ 0.5.

Similarly, when FeOx + xC = Fe + xCO is in the reduced form, Y / X = 1 is a stoichiometrically necessary condition for reduction of iron oxide. However, it should be noted that C content is used for carburizing when it finally melts, and depending on the operating conditions of the blast furnace, there is C consumption due to diffusion of CO ₂ gas and H ₂ O gas in the furnace into the ore. Considering this, even if C is present at Y / X = 1 or more, it does not remain because it is consumed for reduction and carburization. As shown in the experiment to be described later, if this value is within the range of Y / X ≦ 1.2, the C content used for the carbonaceous material-containing double ore did not remain in the furnace. By the way, if the carbon-containing material used in the carbon material-containing double ore is not used for reduction or carburization, fine powder will remain in the blast furnace,
This will deteriorate ventilation and increase the amount of dust generated from the furnace top.

Next, in the outer shell, it is important to efficiently utilize the CO gas generated in the nucleus for the reduction of iron oxide. Then, the more iron oxide in the outer shell with respect to the CO gas generated in the nucleus, the higher the CO gas utilization efficiency. As described above, X is the number of moles of oxygen bound to iron oxide in the iron oxide-containing substance in the nucleus, which is also the number of moles of CO gas generated. The larger the amount of iron oxide Z in the outer shell, the higher the utilization efficiency of CO gas generated in the nucleus, but on the other hand, if it is too large, the amount of metallic iron produced per carbon material-containing double ore is increased. The amount is relatively decreased, and the effect of improving the productivity of the blast furnace due to the production of metallic iron is hindered. To avoid this situation, as described later, regarding the iron oxide amount Z of the outer shell, Y / (X + Z)
If the range of ≧ 0.3 is satisfied, double ore with carbon material 1
The amount of metallic iron produced per piece can be significantly secured, and productivity in the blast furnace can be improved. The amount of iron oxide in the outer shell Z
It was stated that metallic iron decreases when the amount is too large, but metallic iron does not disappear. This is because the generation of metallic iron in the nucleus is guaranteed by the regulation of 0.5 ≦ Y / X ≦ 1.2.

Further, if the amount of iron oxide in the outer shell is small, the CO gas generated in the nucleus cannot be used efficiently. In that case, CO gas with reducing ability is released from the carbon material-containing double ore to the outside of the particles, so when used in a blast furnace, the fuel ratio in the blast furnace (pulverized coal used for coke and tuyere injection, And the carbon-containing substances contained in the double ore containing carbonaceous materials will also be included). In order to avoid this situation, it is expected that the fuel ratio increase in the blast furnace can be suppressed by setting 0.6 ≦ Z / X as described later.

Here, reduction experiments were carried out using various carbonaceous material-containing double ores using the reduction furnace shown in FIG. That is, a 300 g sample was heated for 2 hours in an atmosphere of temperature: 950 ° C. and N ₂ : 100%. The heating condition of 950 ° C is the representative temperature of the preservation zone of the blast furnace, and the atmosphere of N ₂ : 100% is different from the condition of the blast furnace. The experiment was conducted in an atmosphere of N ₂ : 100% to eliminate the influence. Further, as a result, the CO and CO ₂ appearing in the exhaust gas of the experiment are derived from the C content in the carbonaceous material inside, so it is easy to determine the reduction form of the carbonaceous material-containing double ore. During the experiment, the composition of the exhaust gas was analyzed and the sample after the experiment was analyzed.

As the carbon material-containing double ore, the iron ore shown in Table 1 and the coal shown in Table 2 were used, and the particle size was 99 mass% in each case.
Was a fine powder of 100 μm or less. That is, for the core, a mixture of iron ore shown in Table 1 and coal shown in Table 2 at various ratios was added with a small amount of water and bentonite to be molded,
The outer shell was formed by adding a small amount of water and bentonite to the coal shown in Table 1 to form a granule with a diameter of 15 mm. Furthermore, a drying process was performed before the reduction experiment.

[0030]

[Table 1]

[0031]

[Table 2]

The results of the above experiment are shown in the above equations (1) to (3).
Are summarized and shown in FIGS. First, as shown in FIG. 3, under the condition of 0.5 ≦ Y / X, metallic iron was observed in the nucleus portion in all cases. In an actual blast furnace using sinter or pellets, the ore cannot produce metallic iron at a temperature of about 950 ° C from the furnace top, and the effect of the carbonaceous material-containing double ore of the present invention is large. I understand. Normal blast furnace operation is the CO generated on the raceway
The gas rises towards the top of the furnace, while the ore descends. In the case of sinter or pellets, reduction proceeds by countercurrent contact between these and the gas in the furnace, but in this case, theoretically a chemical conservation zone is formed, that is, FeO + CO = Fe + CO ₂ reaction It has been proved that metallic iron is not made by forming the equilibrium state of.

Next, as shown in FIG. 4, Y / (X + Z)
Under conditions of ≧ 0.3, carbon material interior including core and outer shell 2
Since it is possible to secure a ratio of metallic iron of 5% or more in the iron content in heavy ore, it can be seen that the productivity of the blast furnace can be improved by the production of metallic iron.

Further, as shown in FIG. 5, 0.6 ≦ Z / X
The value of CO ₂ / (CO + CO ₂ ) of the exhaust gas (
The utilization rate of CO gas for reduction in the outer shell) is approximately 0.4 to 0.6, which is higher than the gas utilization rate of 0.3 in the conservation zone of the blast furnace during normal operation. This means that the amount of indirect reduction in the preservation zone is higher than that in normal operation, and as a result, the reduction of direct reduction in the lower part of the furnace can be expected, so the effect of suppressing the increase in fuel ratio can be expected for the blast furnace as a whole. .

In addition, using the same reducing furnace as described above, 300
2 g of the sample in an atmosphere of temperature: 950 ° C. and N ₂ : 100%.
After heating for an hour, the temperature was further raised to 1470 ° C. at a rate of 400 ° C./h to melt the sample, and then the sample in the furnace after cooling was recovered, and the residue of C was investigated. As a result, Y /
Under the condition of X ≦ 1.2, it was found that the C component contained in the carbonaceous material-containing double ore did not remain in the furnace.

In the double mine containing carbonaceous material, the core and
Caor and CaCO on the outer shell₃, Ca (OH) ₂, MgO, MgCO₃Oh
And Mg (OH)₂One or more, specifically one of these ingredients
Contains one or more species, especially one or more powdered substances
Preferably. In other words, the double mine with carbon material is
Formed from iron oxide-containing substances and carbon-containing substances
Iron-containing substances such as iron ore, carbon-containing substances such as coal and coke
When used, it will contain gangue and ash. So
In the case of, contains a powdery substance containing one or more of the above ingredients
The powdered material is placed near the gangue and ash.
As a result, the melting of gangue and ash in the carbonite-containing double ore
Can be promoted.

Examples of such powdery substances include limestone, converter slag, dolomite and the like.

Further, in the carbonaceous material-containing double ore, it is preferable that the core and / or the outer shell contain powdery metallic iron. That is, unlike iron oxide, metallic iron does not need to be reduced and can be melted only at a low temperature by carburizing.Therefore, by incorporating metallic iron, it is possible to easily dissolve a carbonite-containing double ore. Become.

[0039]

Example Using the iron ore shown in Table 1 and the coal shown in Table 2, a carbon material-containing double ore was produced. The particle size of both iron ore and coal is a fine powder with 99 mass% of 100 μm or less. First, 180 g of coal powder against 1000 g of iron ore powder
And 15 g of bentonite as a binder are mixed in advance with a V-type mixer to obtain mixed powder A. Also,
A mixed powder B is prepared by mixing 15 g of bentonite as a binder with 1000 g of iron ore powder by a V-type mixer. Then, the mixed powder A was put into a pan pelletizer having a diameter of 100 cm together with water to produce a core portion of the carbon material-containing double ore. The rotation speed of the pan pelletizer is 25 rpm, the mixed powder A is about 300 g / min, and the water is about 10 g.
Each was charged at about / minute. Next, while leaving the core part in the pan pelletizer, the mixed powder B was added in an amount of about 300 g /
Min. And water at about 10 g / min., Respectively, to form an outer shell and produce a carbonaceous material-containing double ore having an average particle size of 19 mm. Here, the amount of the mixed powder B, that is, the outer shell is 1: 1 (weight ratio) with respect to the mixed powder A.

Ten pieces were randomly sampled from the carbonaceous material-containing double ore thus obtained, and the amount of the outer shell and the core and the amount of the carbonaceous material of the core were examined while shaving each. As a result of the analysis, in the obtained carbonaceous material-containing double ore, Y /
X is 0.69 to 0.88, Y / (X + Z) is 0.35 to 0.44 and Z /
X was in the range of 0.9 to 1.2.

[0041]

When the carbonaceous material-containing double ore according to the present invention is used as a raw material for charging a blast furnace, it is possible to improve productivity while preventing an increase in fuel ratio in the blast furnace.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a blast furnace treated ore according to the present invention.

FIG. 2 is a diagram showing a reduction furnace used in an experiment.

FIG. 3 is a diagram showing a relationship between an iron oxide amount and a carbonaceous material amount in a blast furnace treated ore and a metallization rate in a nucleus.

FIG. 4 is a diagram showing the relationship between the iron oxide amount and the carbonaceous material amount in the blast furnace treated ore and the overall metallization rate.

FIG. 5 is a diagram showing the relationship between the amount of iron oxide and the amount of carbonaceous material and the exhaust gas utilization rate in the treated ore for blast furnace.

Claims (4)

[Claims] 1. A blast furnace treated ore comprising a core made of a mixture containing an iron oxide-containing substance and a carbon-containing substance covered with an outer shell containing the iron oxide-containing substance. 2. The number of moles of oxygen bound to iron oxide in the iron oxide-containing substance in the nucleus (X), the total number of moles of carbon in the carbon-containing substance in the nucleus (Y), and the oxidation of the iron oxide-containing substance in the outer shell. The iron-bonded oxygen mole number (Z) satisfies the following formulas (1) to (3), and the blast furnace treated ore according to claim 1. Note 0.5 ≦ Y / X ≦ 1.2 ---- (1) Y / (X + Z) ≧ 0.3 ---- (2) 0.6 ≦ Z / X ---- (3) 3. At least one of a nucleus and an outer shell is CaO, CaCO ₃ , Ca (OH) ₂ , MgO, MgCO ₃ and Mg.
The treated ore for blast furnace according to claim 1 or 2, containing at least one selected from (OH) ₂ . 4. The treated blast furnace ore according to claim 1, wherein at least one of the core and the outer shell contains powdered metallic iron.