JPH0625369B2 - Blast furnace raw material charging method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a raw material charging method in a blast furnace.

(Prior Art) As is well known, in a blast furnace, iron ore (hereinafter, simply referred to as ore) and coke are charged in layers, and these layered charging materials (hereinafter, referred to as charging materials) are hot gases. By contacting with, the charge becomes pig iron through the processes of drying, heating and reducing. In order to make these processes proceed smoothly, it is essential to appropriately control the contact between the charge controlling the temperature rising / reducing process and the gas in the furnace.

Conventionally, the control of the gas flow distribution is generally performed by making the layer thickness ratio of ore and coke (hereinafter, referred to as Lo / Lc) different in the radial direction. Recently, a method has been proposed which focuses on the difference in ventilation resistance caused by the difference in particle size of the charge. For example, JP-A-57-15830
In JP-A-4, coarse coke having a large grain size is charged so that a concave portion is formed in the circumferential direction in the vicinity of the furnace wall, and thereafter, fine coke having a small grain diameter is mounted in the concave portion. The method of suppressing the gas flow around the furnace and effectively utilizing the fine-grain coke is disclosed. Further, in Japanese Patent Laid-Open No. 55-28308, raw materials composed of ore and coke are classified into a plurality of types each having a predetermined particle size, and the type and charging amount of the raw materials are classified according to the gas flow distribution. A method for controlling the gas flow by selecting a charging point and separately charging is shown.

However, the effect is not sufficient regardless of the various charging controls described above, and the all-coke that has been actively adopted recently in order to save cost especially with the price increase of heavy oil and the like. During operation, the temperature of the furnace body around the lower part of the furnace decreased, impairing the smooth running of the blast furnace operation. (Hereinafter, this phenomenon is referred to as a furnace bottom deactivation phenomenon.) (Problems to be solved by the invention) There are various possible causes for the furnace bottom deactivation phenomenon, but in the end, solids in the furnace peripheral portion The ratio of the heat capacity on the gas side to the heat capacity on the gas side, that is, the heat flow ratio (heat flow ratio = heat capacity on the solid side / heat capacity on the gas side. Note that heat capacity is the product of the specific heat of the substance and the mass velocity). Then, the temperature of the ore
It is presumed that the reduction / dissolution is not carried out smoothly.

In order to improve this, a well-known movable armor is used to control the dropping point of the charge so that the L
Although measures have been taken to lower the o / Lc, in order to solve the furnace inactivation phenomenon, the peripheral Lo / Lc must be significantly reduced.
In many cases, Lc increased too much to make the gas flow in the center unstable, which made it difficult to smoothly perform the blast furnace operation.

The present invention seeks to radically solve the above-mentioned conventional problems, and a raw material charging method that enables a blast furnace operation that eliminates the inactivation phenomenon of the lower part of the furnace without impairing the stabilization of the air permeability of the central part. It is provided.

(Means for Solving Problems) The present invention, when charging iron ore and coke in layers,
In a blast furnace raw material charging method in which iron ore per charge is divided into two or more batches, 10 to 25% by weight of the layered coke charged between the iron ore batches
In addition, by inserting fine coke having a particle size of 8 to 30 mm into the peripheral portion of the furnace, the above problems can be solved.

(Operation) FIG. 1 is a partial cross-sectional view of the inside of a blast furnace for explaining the raw material charging method according to the present invention. In FIG. 1, 1 indicates an ore charged in the furnace, and 2 indicates a coke. The ore 1 and the coke 2 are charged alternately and form a layer of an ore layer 10 and a coke layer 20, respectively. Charge amount of ore 1 and coke 2 per charge is the furnace volume,
The number of batches per charge is determined based on the production amount, the operating conditions, the facility capacity, etc., and the charging amount, the hopper capacity, the purpose of distribution control, and the like.

In the present invention, the charging per charge of the ore 1 is divided into at least two or more batches to set the charging pattern. The example in Fig. 1 is one in which the charge of ore per charge is divided into two batches, and charging is carried out. Coke 2 is charged between the charging of the first batch and the charging of the second batch. As a result, the coke intervening layer 3 is formed between the first and second batch ore layers 10a and 10b. In the present invention, the ore layer means a boundary portion between upper and lower ore layers separately charged in the charging of one charge as described above. As the coke 2 for forming the coke intervening layer 3, a part of the coke forming the coke layer 20 which is usually used in the operation is used, or a coke having a particle size distribution different from that of the coke 2 is used. It is possible to use any of the methods of storing it in the hopper and using it. The charging amount may be appropriately set within a range in which a predetermined air permeability can be efficiently ensured in the fusion layer to be described later.
According to the experience of the present inventors, forming the coke intervening layer 3 in an amount of 1/10 to 1/4 (% by weight) of the normal coke and the charging amount per charge is effective in exhibiting the above function. It was

When the number of batches for one charge of ore is divided into a plurality of 3 or more, naturally, a plurality of ore layers of 2 or more appear. In such a case, the coke intervening layer 3 may be formed between all the ore layers, or may be formed only between specific ore layers, but the charging amount for forming the coke intervening layer 3 is within the above range. It is preferable to set the inside. Further, according to the experience of the present inventors, the formation position of the coke intervening layer 3 is to be formed in the peripheral portion of the furnace as shown in FIG. 1 in order to modify the heating, reduction and melting of the ore in the peripheral portion of the furnace. I liked it. The formation position of the coke intervening layer 3 can be controlled by appropriately changing the inclination angle of the movable armor 6.

Now, the charging materials charged as described above are sequentially lowered to the lower part of the furnace, and with this, the temperature of the ore 1 and the coke 2 is raised and the ore 1 is melted. In FIG. 1, 4 indicates a fusion layer in which the above-mentioned ore 1 is melted. The fusible layer 4 has poor air permeability as compared with the ore layer 10, and the reducing gas 7 does not easily flow therethrough. Thus, the coke intervening layer 3 formed according to the present invention remains in the fusion layer 4 in the lower part of the furnace while maintaining its almost initial shape, and a passage for reducing gas is secured in the fusion layer 4. Fulfills the function of a spacer. As a result, the temperature rise, reduction and melting of the ore in the fusion layer 4 proceed smoothly.

As described above, according to the present invention, by forming the thin coke intervening layer 3 between the ore layers, Lo / Lc in the peripheral portion can be slightly reduced, and at the same time, the air permeability of the fusion layer 4 in the lower part of the furnace can be secured. It was possible to improve the temperature rise, reduction, and dissolution of the ore in the coating layer 4. As a result, the deactivation phenomenon of the lower part of the furnace can be resolved without destabilizing the air permeability of the central part, and the smooth progress of the blast furnace operation becomes possible.

(Example) Example 1 In order to investigate the behavior of the coke intervening layer based on the present invention, a model furnace of 1/3 of 3000 m ³ class blast furnace was made, and the situation before ore fusion was simulated. Fig. 2 shows the state of coke and ore deposition in the radial direction of the furnace by the conventional method.
FIG. 3 (A) is a comparison with the method (B) according to the present invention, and FIG. 3 is a diagram showing an example of the results of investigation of gas flow distribution in the deposition state of FIG. .

From FIG. 2, it was confirmed that it is possible to separately charge the ore charged per charge into two batches and form a coke intervening layer between the ore layers above and below the charge. Further, from FIG. 3, it was possible to increase the gas flow velocity in the peripheral portion of the furnace by the charging method of the present invention as compared with the conventional raw material charging method. It was presumed that this was effective in improving the heat flow ratio in the peripheral portion of the furnace described above, and was effective in eliminating the furnace inactivation phenomenon.

Example 2 The present invention was carried out in a 3000 m ³ blast furnace.

The charging pattern in this embodiment is as shown in Table 1, and the coke charged between the ore layers is 30 to 8 mm.
The fine grain coke was used and the charging amount was 3.5 tons. This corresponds to about 15% of the usual amount of coke charged per charge.

Further, in order to form the coke intervening layer in the peripheral portion as shown in FIG. 2, the inclination angle of the movable armor was adjusted so that a concave portion was formed in the peripheral portion of the ore layer charged immediately before.
FIG. 4 shows the results of investigating the gas temperature distributions in the furnace top and in the radial direction during operation in the conventional charging method and the charging method according to the present invention. It is considered that the temperature around the furnace was rising and the gas flow velocity around the furnace increased.

As a result, it was possible to significantly increase the temperature of the lower part of the furnace as shown in FIG. In FIG. 5, the vertical axis represents the furnace height direction by the number of stages of the cooling platen (the lower the number of stages is the lower part of the furnace), and the horizontal axis represents the temperature.

Next, FIG. 6 shows an example of the result of investigating the effect of this embodiment over a long period of time.
It shows the temperature transition at the stage level and the load drop situation at that time. The load drop situation is the number of times of known shelves (H), slips (S), and drops (D) that occur every day [4H + 2S
+ D (times / day)]. As is apparent from FIG. 6, the temperature of the lower part of the furnace was always 15
It can be maintained at a high temperature of 0 ° C or higher, which helps stabilize the load drop. As a result, as shown in FIG. 6, the coke ratio can be reduced and the hot metal quality can be stabilized, and the production amount (amount of hot metal) does not fluctuate day by day, which enables stable operation for a long period of time. It was

(Effects of the Invention) By carrying out the present invention, it was possible to effectively eliminate the inactivation phenomenon of the lower part of the furnace without inhibiting the air permeability and stabilization of the central part of the furnace. As a result, it was possible to maintain stable blast furnace operation for a long period of time.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of the inside of a blast furnace for explaining a raw material charging method based on the present invention, FIGS. 2 to 6 are views for investigating the effects of the present invention, and FIG. 2 is a furnace radius. Diagram showing the state of coke and ore deposition in the direction of comparison with the conventional method, No. 3
FIG. 4 is a diagram showing an example of gas flow distribution survey results in the deposition state of FIG. 2, and FIG. 4 is a furnace top portion and a radial direction when operating in the conventional charging method and the charging method according to the present invention. Fig. 5 shows the results of investigation of gas temperature distribution in Fig. 5, Fig. 5 shows the temperature of the lower part of the furnace in comparison with the conventional method, and Fig. 6 shows the effect of the embodiment according to the present invention over a long period of time. It is a figure which shows an example of the result of investigation. 1 ... Ore 10 ... Ore layer 2 ... Coke 20 ... Coke layer 3 ... Coke intervening layer 4 ... Fusion layer 6 ... Movable armor 7 ... Reducing gas

Claims (1)

[Claims] 1. A method for charging a raw material of a blast furnace, wherein when iron ore and coke are charged in layers, the iron ore per chazi is divided into two or more batches. 10-25% by weight of coke charged
And a fine blast coke having a particle size of 8 to 30 mm is charged into the peripheral portion of the furnace, and the blast furnace raw material charging method.