JP4923872B2 - Blast furnace operation method - Google Patents

Description

  The present invention relates to a method for operating a blast furnace when ferro-coke is used as a blast furnace raw material.

  Ferro-coke produced by dry distillation of a molded product formed by mixing coal and iron ore is able to increase the coke reactivity due to the catalytic effect of iron ore at the same time that iron ore is partially reduced. It can be used as a blast furnace raw material by mixing with iron ore raw material (hereinafter referred to as main raw material) composed of sintered ore, lump ore, pellets, etc., thereby increasing the gas utilization rate in the blast furnace and reducing material It is known that the ratio can be reduced (for example, see Patent Document 1). According to Patent Document 1, coke is charged into a blast furnace alone to form a coke layer, and iron ore and ferro-coke are mixed and charged into the blast furnace to reduce the reducing material ratio, Productivity is also expected to improve. This is a very effective technique because both the effects of lowering the temperature of the blast furnace thermal preservation zone and charging partially reduced iron ore due to the use of ferro-coke are manifested simultaneously.

On the other hand, the use of ferro-coke has a problem of deterioration of air permeability in the furnace. The situation inside the blast furnace will be described with reference to FIG. FIG. 6 is a schematic diagram of a longitudinal section of the blast furnace. In the blast furnace 1, the coke is weakened by the progress of the gasification reaction shown in the following formula (b), and the strength is reduced.
C + CO ₂ = 2CO (b)
CO _{2 in the} formula (b) is generated during the reduction reaction of the main raw material. In the upper and middle parts of the blast furnace, the coke undergoes a reaction mainly in the region of the heat preservation zone 2 to the cohesive zone 4, but when the deteriorated coke moves further downward or undergoes the above gasification reaction. In the process, powder is generated due to the load of load and friction during movement. When the coke powder generated from the coke deteriorated in these regions falls to the dripping zone 5, or when the deteriorated coke falls to the dripping zone 5 and receives friction or the like to generate powder, the dripping zone 5 The porosity of the coke layer is reduced. It is known that an increase in the coke powder rate at the bottom of the furnace causes a deterioration in air permeability (see, for example, Non-Patent Document 1). When the air permeability deteriorates, the stable operation is hindered due to unsatisfactory descending of charges such as slips and the accompanying fluctuations in the furnace heat, leading to a reduction in pig iron production and an increase in the coke ratio. Therefore, generation of coke powder in the furnace is not desirable.

  It is considered that the above phenomenon becomes more prominent when ferro-coke having a higher reactivity than ordinary blast furnace coke is used as a blast furnace raw material. Therefore, when using ferro-coke, a reduction in the reducing material ratio can be expected by increasing the gas utilization rate in the blast furnace by increasing the coke reactivity. Operation may be hindered.

As a method of removing the coke powder at the bottom of the furnace, a technique is known in which carbon unsaturated iron is dropped into the furnace core part by charging scrap or the like at the center of the furnace top to reduce the powder coke in the furnace core. (For example, refer to Patent Document 2). However, this technology is such that the charging range of scrap and other iron raw materials is sufficient to be 20% or less of the furnace diameter from the center, so the coke powder removal effect is limited to the furnace core. The above-described dripping zone below the fusion zone has no effect on removing coke powder other than the furnace center.
JP 2006-28594 A Japanese Patent No. 2608505 Materials and Process 3 1990, p. 6

  However, when ferro-coke is used as a blast furnace raw material, the above-described conventional method is insufficient in order not to deteriorate the air permeability in the blast furnace, and there is a fear that the reducing material ratio is not reduced.

  Therefore, the object of the present invention is to solve such problems of the prior art and to remove coke powder derived from ferro-coke in the dripping zone when operating using ferro-coke mixed with the main raw material of the blast furnace. Therefore, an object of the present invention is to provide a method of operating a blast furnace capable of preventing deterioration of air permeability in the furnace.

The features of the present invention for solving such problems are as follows.
(1) A range in which the iron ore raw material, ferro coke, and metallic iron raw material are mixed and charged from the furnace top, and the charging amount of the ferro coke and the metallic iron raw material is represented by the following formula (a): A method of operating a blast furnace, characterized by:
Metallic iron raw material basic unit (kg / t) ≧ 0.286 × ferrocoke basic unit (kg / t) (a)

  According to the present invention, even if a large amount of ferro-coke is used as a blast furnace raw material, the air permeability in the furnace can be maintained satisfactorily, and an operation with a reduced reducing material ratio can be performed stably.

  In order to remove the ferro-coke-derived powder in the dropping zone of the blast furnace, it is considered that carbon-unsaturated iron may be dropped at the location where this powder exists. As a means for dripping carbon unsaturated iron, a droplet generated by dissolving a metal iron raw material such as scrap may be used. Therefore, coke powder generated by reaction degradation of ferro-coke can be removed by carburization by using metallic iron raw materials such as scrap together with ferro-coke. Here, when the metallic iron raw material is present at a location away from the ferro-coke at the furnace radius position, there is no opportunity for the ferro-coke-derived powder and the droplets derived from the metallic iron raw material to contact each other, and the powder is not removed. Therefore, the scrap needs to be present at the same radial position as the ferro-coke.

  The present invention has been completed by obtaining the above-described knowledge, and operates a blast furnace by charging an iron ore raw material, ferro-coke, and metallic iron raw material from the top of the furnace. It is preferable to mix the iron ore raw material, ferro-coke, and metallic iron raw material and charge them from the top of the furnace. By mixing the iron ore raw material, ferro-coke and metallic iron raw material and charging from the top of the furnace, the ferro-coke-derived powder and the metallic iron raw material droplet can be brought into sufficient contact, and the ventilation of the blast furnace Sexual deterioration is prevented.

  In addition, an iron ore raw material is a main raw material of a blast furnace, and is a raw material mainly containing iron ore composed of sintered ore, lump ore, pellets and the like.

  Ferro-coke is produced by heating a molded product produced by molding a raw material mainly composed of coal and iron ore, and carbonizing the coal in the molded product. In the above, the main component of coal and iron ore means that the raw material of ferro-coke is mainly coal and iron ore, and uses a raw material containing 70 mass% or more of coal and iron ore. Ferro-coke is produced, but usually a raw material containing 80 mass% or more of coal and iron ore is used. In addition to coal and iron ore, a binder for molding can be used.

  The metallic iron raw material is a raw material mainly containing metallic iron, such as scrap or reduced iron, and refers to a raw material having a metal iron content of 80 mass% or more. It is preferably metallic iron containing almost no carbon. Hereinafter, the metallic iron raw material is also referred to as a metallic raw material.

It is preferable that the amount of the ferro-coke and the metallic iron raw material is in the range represented by the following formula (a) because the air permeability of the blast furnace is sufficiently improved.
Metallic iron raw material basic unit (kg / t) ≧ 0.286 × ferrocoke basic unit (kg / t) (a)
An embodiment of the present invention will be described below.

  In the present invention, a “main raw material + ferrocoke” layer in which ferrocoke is mixed with iron ore raw material (main raw material) composed of sintered ore, lump ore, pellets, etc., and a layer in which metallic raw material is further mixed is a blast furnace. In order to form inside, iron ore raw material, ferro-coke, and metallic raw material are mixed and charged from the top of the furnace. The mixing of the charged raw materials can be performed in a raw material yard, a conveyor on the top of the furnace, a charging hopper at the top of the furnace, or the like. In this case, FIG. 1 shows a schematic diagram of the in-layer state formed by the charged raw material in the furnace. In order to sufficiently bring the ferro-coke-derived powder and the droplets derived from the metallic raw material into contact, it is preferable that the ferro-coke 11 and the metallic raw material 12 are uniformly mixed as shown in FIG. 13 is a main raw material. r is the blast furnace radial direction, and h is an arrow indicating the height direction of the layer.

  On the other hand, since it is effective if the ferro-coke and the metallic raw material are present at the same radial position, the metallic raw material is a case where the metallic raw material is arranged in part as shown in FIG. 2 in addition to the uniform mixing shown in FIG. Even if it exists, the same effect can be expected. In this case, it is possible to perform blast furnace operation in an in-layer state as shown in FIG. 2 by charging the metallic raw material 12 and separately mixing the main raw material 13 and the ferro-coke 11 and charging them into the blast furnace. It is.

In a blast furnace with an internal volume of 5000 m ³ , based on the operating conditions of a coke ratio of 370 kg / t and a pulverized coal ratio of 130 kg / t (operation No. 1), the mass ratio of fine iron ore: coke = 0.4: 0.6 Operation using the produced ferro-coke (operation No. 2, 3), operation using ferro-coke and metallic raw materials (operation No. 4, 5) were performed. Operation No. No. 1 is a normal operation mode in which main raw materials composed of lump ore and sintered ore and coke are alternately charged into the furnace, and in the operation using ferro-coke (operation No. 2, 3), Coke was mixed with the main raw material and used as shown in FIG. In operations using ferro-coke and metallic raw materials (operation Nos. 4 and 5), scraps were mixed as metallic raw materials as shown in FIG.

  Table 1 shows changes in operating conditions, lower ventilation resistance index, and output ratio in each operation. The lower ventilation resistance index was measured in the lower ventilation resistance measurement range 7 shown in FIG.

表１によれば、フェロコークスを使用した操業Ｎｏ．２、３では、操業Ｎｏ．１と比較してコークス比が減少したため還元材比は低減したが、図４に示す範囲の下部通気抵抗が増大し、送風量を減じた結果、出銑量が減少した（比較例１、比較例２）。これに対し、図１に示すように主原料＋フェロコークス混合層にさらにスクラップを混合した操業を行なったところ、下部通気抵抗指数は減少し、通気変動が抑制されて、操業が安定し、出銑比をベース条件に戻すことができた（本発明例１、本発明例２）。

According to Table 1, the operation No. using ferro-coke is shown. In Nos. 2 and 3, the operation No. The ratio of reducing material was reduced because the coke ratio was reduced as compared with 1, but the lower ventilation resistance in the range shown in FIG. 4 was increased, and as a result of reducing the amount of blown air, the output amount was reduced (Comparative Example 1, comparison) Example 2). On the other hand, as shown in FIG. 1, when the operation was performed by further mixing scrap with the main raw material + ferrocoke mixed layer, the lower airflow resistance index decreased, the airflow fluctuation was suppressed, the operation was stabilized, and the output was stabilized. It was possible to return the ratio to the base condition (Invention Example 1, Invention Example 2).

Furthermore, the operation test was repeated by changing the amount of ferro-coke and scrap, and the improvement effect of air permeability was confirmed. The results are shown in FIG. When using ferro-coke, it was found that the effect of improving the air permeability by using the metallic raw material is expressed in the upper left region of FIG. From FIG. 5, it was found that the amount of the metallic raw material used is preferably in the range of the following formula (a) with respect to the amount of ferrocoke used.
Metallic iron (metallic) raw material basic unit (kg / t) ≧ 0.286 × ferrocoke basic unit (kg / t) (a)

Schematic diagram of the state in the layer (ferrocoke + main raw material). Schematic diagram of the state in the layer (ferrocoke + main raw material + metallic raw material). Schematic diagram of the state in the layer (ferrocoke + main raw material + metallic raw material). Explanatory drawing of a lower ventilation resistance measurement range. The graph which shows the relationship between the amount of ferro-coke used, and the amount of metallic raw materials used. Schematic diagram of the situation inside the furnace.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 Heat preservation zone 3 Mass band 4 Fusion zone 5 Dripping zone 6 Raceway 7 Lower ventilation resistance measurement range 11 Ferro-coke 12 Metallic raw material 13 Main raw material r Blast furnace radial direction h Layer height direction

Claims (1)

Mixing iron ore raw material, ferro-coke, and metallic iron raw material, and charging from the furnace top, the charging amount of the ferro-coke and the metallic iron raw material is within the range shown by the following formula (a) A featured blast furnace operation method.
Metallic iron raw material basic unit (kg / t) ≧ 0.286 × ferrocoke basic unit (kg / t) (a)

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