JPH0625365B2 - Blast furnace operating method with non-fired agglomerated ore - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a method for operating a blast furnace in which a raw material to be charged into a blast furnace is blended with a non-calcined agglomerated ore.

(Prior art) In the operation of a blast furnace, the pre-treated iron ore charged from the top of the furnace moves to the lower part of the furnace and is heated and reduced by contact with the gas in the furnace and melted in the cohesive zone. Drop it. The position of this cohesive zone is almost determined by the degree of temperature rise and reduction while the iron ore is descending from the furnace top to the cohesive zone (this part is referred to as the lump zone below). Decreases, and on the contrary, it increases when it is early. If the position of the cohesive zone is unnecessarily lowered, unreduced iron oxide melt is likely to drop into the hearth and unbalance in the circumferential direction, which not only makes smooth operation of the blast furnace difficult. Nonetheless, it also induces cooling of the blast furnace. On the contrary, if the temperature rises, it will unnecessarily increase the hot metal temperature and the [Si] in the hot metal.

As such a furnace heat control method, for example, JP-A-58-7
As disclosed in Japanese Patent No. 1308, there is one in which iron oxide having a specified grain size is blown from the tuyere of a blast furnace.

On the other hand, most of the pre-treated iron ore that is charged is sinter, and some of it is mixed with lump ore. From the problem that SOX, NOX or dust becomes a pollution source, and from the viewpoint of energy saving, iron ore powder is internally equipped with a fuel source such as coke powder, and cement, water, etc. are added and mixed as a binder,
Development of a non-fired agglomerated ore that has been cured and hardened after being formed into pellets, etc. has been partially put into practical use by blending it with the above-mentioned sintered ore and agglomerate ore as a raw material for blast furnace charging. , And efforts are being made to increase the blending amount.

(Problems to be solved by the invention) However, since the non-calcined agglomerated ore generally uses a hydraulic binder such as cement as a binder as described above, water is added to the uncalcined agglomerated ore. Due to the endothermic reaction caused by the water of crystallization / adhered water, the delay in the temperature rise at the upper part of the shaft in the furnace and the accompanying delay in the reduction become remarkable when a large amount of uncalcined agglomerated ore is used. In particular, the decomposition endothermic reaction of water of crystallization is prolonged to near 600 ° C., which considerably hinders the temperature rise of the raw materials. Therefore, it was one of the major causes of the inability to mix a large amount of non-fired agglomerated ore with sinter ore.

The present invention is intended to provide a stable blast furnace operating method by appropriately controlling the furnace heat by blowing iron oxide from the tuyere to reduce the reduction delay due to the charging of non-calcined agglomerated ore based on such circumstances. .

(Means for Solving Problems and Actions) The gist of the present invention is to provide a blast furnace operating method in which a non-calcined agglomerated ore is mixed with a blast furnace charging raw material, Accordingly, the iron ore powder or the iron oxide powder is blown from the blast tuyere to control the furnace heat.

Next, the method of the present invention will be described in detail.

The iron ore charged at the top of the blast furnace is the gas in the furnace (CO, CO ₂ , H ₂ ,
It descends through the massive zone while being heated and reduced by N ₂ ). Since the gas is ejected from the cohesive zone, the temperature is approximately constant. Therefore, the property of the raw material to be heated and reduced, the amount of gas per unit of raw material, and the descending speed of iron ore determine the heating and reducing speed. When the ratio of non-calcined agglomerated ore charged from the furnace top is changed, the endothermic change in the massive zone ΔQ is
It is represented by (1).

However, ΔQi: heat of reaction H ₂ O (l) → H ₂ O (g) ΔQ ₁ Fe ₂ O ₃ · H ₂ O → Fe ₂ O ₃ + H ₂ O (g) ΔQ ₂ Al ₂ O ₃ / 3H ₂ O → Al ₂ O ₃ ＋ 3H ₂ O (g) △ Q ₃ Al ₂ O ₃・ 2SiO ₂・ 2H ₂ O → Al ₂ O ₃ ＋ 2SiO ₂ ＋ 2H ₂ O (g) △ Q ₄ Ca ( OH) ₂ → CaO + H ₂ O (g) △ Q ₅ CaCO ₃ → CaO + CO ₂ (g) △ Q ₆ △ Vi: Increase / decrease in i substance due to increase / decrease in uncalcined agglomerate composition ratio The change in the amount of gas to be corrected by increasing or decreasing the amount can be calculated by equation (2).

△ Gas amount = △ Q ÷ (△ T × C gas) ・ ・ ・ (2) However, △ T: Gas ejection temperature from the cohesive zone-top furnace gas temperature C gas: Specific heat of gas in the furnace The amount of increase / decrease in the required fuel ratio (carbon ratio) to increase / decrease with CO and CO ₂ gas can be calculated by equation (3).

△ fuel ratio = △ gas amount ÷ 22.4 × 12 ÷ carbon content in fuel ... Equation (3) The fuel ratio changes only in the gas amount (CO, CO ₂ , N ₂ , H ₂ ). In the case of gasification as shown in equation (4), the heat of reaction accompanies the tuyere, so the reactions such as sensible heat of the melt dripping at the tip of the tuyere, reduction of SiO (g) with carbon, etc. Let This hinders the stabilization of blast furnace operation and the stabilization of hot metal quality.

C + 1 / 2O ₂ → CO (4) In order to prevent this, according to the method of the present invention, before the change of the non-calcined agglomerated ore composition ratio due to the increase or decrease of the amount of fine iron ore blown from the tuyere, this fuel ratio change And the same fuel ratio (base fuel ratio). That is, with respect to the increase / decrease in the calculated fuel ratio, the increase / decrease amount of the fine iron ore blown from the tuyere is calculated by the formula (5) and executed.

△ Powdered iron stone injection amount = △ Fuel ratio ÷ (Base fuel ratio × Iron oxide production basic unit of iron oxide) ・ ・
・ ・ Equation (5) Even if the unfired agglomerated ore mixture ratio is changed and the endothermic amount in the agglomerated zone changes, the temperature rise and reduction conditions in the agglomerated zone do not change. This is a method of operating a blast furnace in which the quality of hot metal such as temperature and components can be made constant.

The iron oxide powder used in the method of the present invention is iron ore, mill scale, metal refining slag, or the like, and any iron oxide such as FeO, Fe ₃ O ₄ Fe ₂ O ₃ is effective. It is preferable to make the particle size as fine as possible. The reason is that if the particle size is large, it reaches the bottom of the furnace without being reduced to iron,
This is because there is a risk that the increase in FeO concentration may lead to an increase in [S] in the hot metal.

Further, the non-calcined agglomerated ore compounded and charged is more effective as the water content is higher as described above, but even if the water content is low, the reduction delay due to the decomposition endothermic reaction can be prevented, so that the method of the present invention can be sufficiently exerted. Is.

(Example) The present invention was carried out in a blast furnace having a furnace volume of 4000 m ³ . Table 1 shows the components and water content of the non-calcined agglomerate, which is mainly composed of iron ore powder, carbon is added, cement and water are added and kneaded to form pellets having a particle size of 8 to 16 mm, and cured and hardened.

As iron oxide powder, particle size composition-0.044mm58%, 0.044-0.12
Fine iron ore of 5% 30% and 0.125 to 0.25 mm 12% was used. The components are shown in Table 2.

As shown in the figure, the non-calcined agglomerated ore having the components shown in Table 1 was mixed and charged into the sinter with different blending ratios. On the other hand, the fine iron ore having the components shown in Table 2 was blown from each tuyere using a blowing device according to the blending ratio of the non-calcined agglomerated ore, and the normal blast furnace operation was performed.

The results are shown in the same figure as a comparative example together with a conventional operation method in which iron oxide is not blown. As is clear from this figure, according to the blending ratio of the non-calcined agglomerated ore, powdered ore was blown from the tuyere as iron oxide, and the fuel ratio was kept constant at a low value by operating, and the hot metal temperature and the pig iron It became possible to keep [Si] almost constant.

(Effects of the Invention) As described above, according to the method of the present invention, even if the endothermic amount is changed by increasing the charging amount of the non-calcined agglomerated ore, the temperature rise and reduction conditions in the massive zone are not changed. Since the quality of the hot metal can be kept constant, the amount of non-fired agglomerated ore used can be increased, the cost of raw material processing can be reduced, and the blast furnace operating method is excellent in energy saving.

[Brief description of drawings]

The figure is a relational diagram of the elapsed time of blast furnace operation, the amount of powdered ore injected and the fuel ratio, the hot metal temperature, and the in-pigment [Si] with respect to the non-fired agglomeration compounded amount in the examples.

Claims (1)

[Claims] 1. A blast furnace operating method in which a non-calcined agglomerated ore is mixed with a blast furnace charging raw material, and powdered iron ore or oxidization is carried out from a blast tuyere according to a compounded amount of the non-calcined agglomerated ore and a water content. A method for operating a blast furnace in which non-sintered agglomerated ore is compounded and charged, which comprises injecting iron powder and controlling furnace heat.