JPS63230808A - Method for charging raw material in blast furnace - Google Patents

Abstract

PURPOSE:To improve the efficiency of blast furnace operation by controlling the ratio of permeable resistances of iron ore and coke to the specific range at the time of supplying alternately the ore and the coke as layer-state. CONSTITUTION:The ore and coke are alternately supplied in the blast furnace as the layer-state. Then, the ratio of the permeable resistance of the iron ore charged in the furnace wall side of the blast furnace and the permeable resistance of the coke layer charged in the upper face and the lower face of the iron ore layer, is controlled so as to become the range of 10-45. For example, charging of the iron ore classified into grain sizes, etc., is executed. By this method, inactive zone in the blast furnace can be controlled and the utilizing efficiency in the blast furnace can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION 0) Industrial Application Field The present invention relates to a method for charging ore and coke into a blast furnace.

(b) Conventional technology In the blast furnace raw material charging method in which ore and coke are charged alternately into the blast furnace, when the furnace wall is worn out and the furnace wall side becomes extremely uneven, the materials are charged in layers from the top of the layer. The injected ore layer and coke layer mix due to the unevenness, forming a so-called mixed layer. In this way, when ore with a small particle size and coke with a large particle size are mixed, the porosity in this mixed layer decreases. As a result, the amount of gas passing through the mixed layer decreases, leading to the formation of the mixed layer in a low temperature range (400 to 600°C).

JP-A-60-17004 discloses a method of regulating the ratio of ore particle size to coke particle size in order to prevent such a decrease in porosity in the mixed layer.

However, such a decrease in porosity must also be affected by the porosity of the ore monolayer or the coke monolayer, and cannot be regulated by the average particle size ratio alone.

Furthermore, the wear and tear on the furnace wall that causes the formation of this mixed layer has been reduced due to advances in the furnace wall structure itself (for example, thick-walled staves) and advances in furnace wall repair technology. Therefore, it is most desirable to maintain the layered structure and charge the gas so that the gas flow is optimal for reducing the ore, that is, the ratio of the ore layer ventilation resistance to the coke layer ventilation resistance is optimized.

On the other hand, JP-A-61-119607, JP-A-61-
In Publication No. 119608, when iron ore and coke are charged into a furnace in layers using small iron ore,
The ratio of the harmonic mean diameter of the layers of iron ore and coke at each part in the radial direction of the furnace is o, te -0,002X < coke diameter m
m) Discloses a method of charging so as to achieve the above. This limit on the harmonic mean diameter ratio was set to prevent the radial distribution of the charge from being significantly disturbed as the iron ore particle size decreases, and to ensure that the charge is deposited stably in layers. As a condition, the particle size range is limited. However, since it is thought that pressure drop due to gas also affects stable deposition at the top surface of the layer, the porosity as well as the ratio of harmonic mean particle size should be used as a constraint on the relationship between the iron ore layer and the coke layer. It is necessary to evaluate the ratio of ventilation resistance, which also takes into account the effect.

In recent years, in order to reduce the cost of blast furnace hot metal, it has become desirable to directly charge fine grained sintered ore and iron ore, which were conventionally returned to the sintering machine, into the furnace. For this reason, the following charging method is used.

■ Lower the lower limit of the furnace sieve for iron ore charged into the blast furnace.

■ Iron ore is separated into fine and coarse particles and charged in layers.

■ Separate iron ore into fine grains and coarse grains, and charge the fine grains closer to the furnace wall to protect the furnace wall.

However, in any case, when fine iron ore is charged,
In a bell-type charging device, an ore layer containing many fine particles is formed on the furnace wall side, which deteriorates gas ventilation to the furnace wall side, and there is a possibility that an inert zone is formed on the furnace wall side. Ta.

(c) Problems to be solved by the present invention The problem to be solved by the present invention is that since the reduction of ore is gas reduction, it is necessary to optimize the gas ventilation resistance ratio between the ore layer and the coke layer. The purpose is to charge raw materials and improve the efficiency of blast furnace operation.

B) Means for Solving the Problems The blast furnace raw material charging method of the present invention is characterized in that when ore and coke are charged into the blast furnace in alternating layers, the iron ore charged on the wall side of the blast furnace is ventilated. The ratio of the resistance to the ventilation resistance of the coke layer charged on the upper and lower surfaces of the iron ore layer is 10 to 4.
The above problem is solved by charging iron ore and coke so that the amount falls within the range of 5.

Ventilation resistance refers to the pressure loss per unit length of a packed bed measured under a constant gas flow rate. In this case, the gas flow rate is 0
．． 5 to 1 m/s.

Increasing the reduction efficiency of iron ore in the blast furnace will lead to improved efficiency of the blast furnace. Since this reduction of iron ore is gas reduction, in addition to the reduction rate of the iron ore itself, gas aeration greatly contributes to this reduction.

In order to increase the reduction rate, the smaller the iron ore particle size, the better. Reduction will not proceed unless reducing gas flows. A general method for evaluating this gas permeability is shown by the following equation (1). Equation (1) is the pressure loss equation of the packed bed, and
This is a pressure drop experiment in a packed bed.

Figure 1 shows an outline of the experimental apparatus. A blower 2 is connected to the bottom of the packed tower 1, and a ventilation resistance ΔP/
ΔL is measured.

ΔP C(1-ε)■+71? C: constant ventilation resistance coefficient φ: particle shape coefficient dp: u sum average particle species ε: porosity g: gravity conversion coefficient ζ: gas density
μ: gas flow rate (in terms of void column) As shown in equation (1), it can be seen that the ventilation resistance is controlled by both the harmonic average particle diameter and the porosity of the packed bed. Therefore, in terms of ease of use, it is best to evaluate the relationship between the iron ore layer and the coke layer based on the ventilation resistance, which takes into account both the harmonic mean particle size and the porosity. Here it is the ventilation resistance coefficient.

A reduction and fusion experiment was conducted assuming the reduction and fusion region of an actual furnace as shown in FIG. 2 to examine the reducibility when such fine-grained iron ore is used alone or in combination with coarse particles. Second
In the figure, 4 indicates an iron ore layer 5 that is a coke layer.

As a result, as shown in FIG. 3(A), the ratio of gas ventilation resistance between the iron ore layer 4 and the coke layer 5 [FIG. 3(B)] is 1.
If it is less than 5, the reduction of large particles is delayed and the reduction rate decreases. On the other hand, above 45, the ventilation resistance of the iron ore layer is extremely high compared to that of the coke layer, so gas preferentially flows through the coke layer, and reduction stagnation occurs due to insufficient flow of reducing gas in the iron ore layer. It was found that this occurs. Appropriate gas permeability is ensured, and the iron ore particle size is small. Airflow resistance ratio (airflow resistance of iron ore layer/airflow resistance of coke layer) is 20
It was found that the return rate was highest when the value was .about.35.

As has been the case recently, if the sizing of coarse iron ore (crushing of coarse particles in order to equalize the upper limit grain size of coarse iron ore) is omitted, the grain size of the coarse iron ore will increase. , the harmonic mean particle size does not become smaller even when fine iron ore is mixed.

However, due to the expansion of the particle size range, the porosity becomes smaller and
Breathability may deteriorate. In particular, both coarse particles and fine particles tend to accumulate on the furnace wall side, leading to an increase in ventilation resistance due to a decrease in porosity, which causes the furnace wall to become inert. Therefore, as an indicator for preventing the formation of an inert zone on the furnace wall, charging is performed so that the ratio of ventilation resistance between the iron ore layer and the coke layer is 45 or more.

(E) Example The raw material charging method of the present invention is carried out by the following procedure.

■ Measure the particle size composition of iron ore and coke charged to the implementation furnace.

■ Estimating the radial particle size distribution of iron ore and coke based on the charging device (for example, in the case of a bell type, bell angle, bell opening stroke, bell opening speed, movable armor position, stock line position, etc.) (Figure 4)
.

■ Based on the radial particle size composition distribution, estimate the harmonic mean particle size and porosity of iron ore and coke at each radial position.

(2) Substitute the harmonic average particle size and porosity of iron ore and coke at each position in the radial direction into the above equation (1) to determine the ventilation resistance of each of iron ore and coke.

■ The ratio of iron ore ventilation resistance/coke ventilation resistance is 45.
If it is above or below 15, take remedial measures such as changing the sieve size or charging according to particle size.

The above-mentioned 0 term is estimated using a regression equation created based on the filling survey results and model experiment results of each blast furnace.

For the above-mentioned 0 term, the porosity is determined from the particle size structure as shown in FIG.

Next, the results of actually applying the present invention to an actual furnace will be described.

When the sieve size of the front sieve for iron ore was gradually lowered in an actual furnace (Fig. 6), an inert zone (400 to 600
℃) occurred, and the unloading behavior toward the end of the day also worsened.

At this time, the ventilation resistance ratio between the iron ore and the coke layer was -48.

Therefore, in order to improve the ventilation resistance ratio and charge iron ore with smaller particle size into the blast furnace, we implemented charging by particle size, which divides iron ore into a coarse grain layer and a fine grain layer and charges it. did. As a result, although the harmonic mean particle size of the fine grain layer decreased, the particle size composition range decreased and the particle size became uniform, which increased the porosity and improved air permeability. Since the ventilation resistance ratio was within the appropriate range at 38 degrees, the inert zone was reduced.

Therefore, it was confirmed that by controlling the ratio between the ventilation resistance of iron ore and the ventilation resistance of coke, it is possible to manage the inert zone of the blast furnace, which is extremely important for improving the utilization efficiency of the furnace.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of a packed bed ventilation resistance measurement experiment. Figure 2 is a schematic diagram of the reduced cohesive zone of iron ore in a blast furnace. FIG. 3 is an explanatory diagram showing the ventilation resistance ratio and the reduction rate of iron ore. FIG. 4 is a graph showing the radial particle size structure of the charge. FIG. 5 is a graph showing the influence of particle size structure on porosity. FIG. 6 is a graph showing the relationship between the ventilation resistance ratio on the furnace wall side and the inertness generation area when fine-grained iron ore is used. 1: Packed tower 2 Ni blower 3: Differential pressure pipe 4: Iron ore layer 5: Coke layer Patent applicant Sumitomo Metal Industries, Ltd. (5 others) Diagram (A) CB) 1 member Katsugihi C7 Qi chanting color 1 pattern

Claims (1)

[Claims] When ore and coke are charged into a blast furnace in alternating layers, the ventilation resistance of the iron ore charged on the wall side of the blast furnace and the coke layer charged on the upper and lower surfaces of the iron ore layer, respectively. A method for charging raw materials into a blast furnace, comprising charging iron ore and coke so that the ratio to ventilation resistance falls within the range of 10 to 45.