JPS6347305A - Method for charging starting material into blast furnace - Google Patents

Abstract

PURPOSE:To improve the gas permeability in a blast furnace and to increase the rate of reduction of pellets by properly regulating the ratio of the thickness of an ore layer to the thickness of a coke layer in the peripheral and central parts of the furnace and charging pellets into the central part when starting materials are charged into the furnace. CONSTITUTION:When starting materials are charged into a blast furnace, the ration of the thickness of an iron ore layer consisting of pellets and sintered ore to the thickness of a coke layer is regulated to 0.45-0.55 in the peripheral part of the furnace and to 0.25-0.35 in the central part and the percentage of pellets in the ore layer is increased in the central part. Gas in the furnace does not flow toward the peripheral part, the rate of reduction of pellets can be prevented from being lowered by the lowering of the CO potential of gas in the central part and the conditions of the furnace are stabilized.

Description

[Detailed description of the invention] [Industrial usage r'f] The present invention relates to a method for charging raw materials into a blast furnace.

[Prior Art] When charging pellets into a blast furnace, when the pellets are charged toward the wall side of the blast furnace, as the pellets flow toward the center of the furnace,
The pellets enter between the coke layers, or as shown in FIG. 9, the coke 4 is rolled into the pellet layer 6, and as a result, the porosity in the furnace becomes smaller.

As a result, the gas distribution inside the furnace changes, and as shown in Figure 1, when the gas flow becomes a peripheral flow, the CO gas potential (CO/ (G O+
C02) ) is significantly reduced.

As the CO gas potential decreases, the reduction rate decreases, and particularly when the blending ratio of pellets is high, the reduction rate at temperatures above 1000° C. decreases significantly compared to when the blending ratio of sinter or pellets is small. In addition, if the peripheral flow becomes excessive, it will damage the large parts of the furnace wall.

Furthermore, when the ore is charged toward the wall with a high pellet blending ratio, the shape of the belly 2 is round, which causes variations in the pellet distribution from the center to the center of the blast furnace (
(inclination angle fluctuation) also increases.

For the above reasons, when the pellet blending ratio is increased, wind pressure fluctuations and solution loss C increase, as shown in Figures 3 and 4 (drawings showing the relationship between pellet blending ratio and furnace conditions). The situation that causes deterioration and decrease in furnace heat will be explained in detail with reference to FIG. Figure 5 shows the results of load reduction tests on sintered ore and pellets. In the case of sintered ore (Fig. 5 (a)), in the high temperature section (1100°C or higher), when the CO gas potential decreases (indicated by solid line B), it also changes when the CO gas potential is normal (indicated by solid line A). On the other hand, in the case of pellets (Fig. 5(b)'), the change in reduction rate is not so noticeable compared to the case shown in Fig. 5(b)'.
When the O gas potential is lowered (solid line B), the reduction rate is significantly lower than when the CO gas potential is normal (solid line A). That is, in the case of pellets, if the CO gas potential is low, the unreduced melt will fall to the lower part of the furnace.

This unreduced melt causes a violent endothermic reaction of FeO+C=Fe+CO, causing a decrease in furnace heat.

Conventionally, the following attempts have been made to improve this phenomenon.

■As an improvement in terms of pellet shape, a method of crushing pellets and using crushed pellets (Special Publication No. 55-4644)
Publication No. 1).

As an improvement from the aspect of pellet reduction, a method of using porous pellets by incorporating charcoal material etc.
7-4528857).

[Problems to be Solved by the Invention] However, when using crushed pellets as in the technology described in Japanese Patent Publication No. 55-46441, the yield rate for crushing the pellets once produced is large. This results in a decrease in

Furthermore, when using porous pellets such as the technique described in Japanese Patent Publication No. 55-46441, porous pellets have low strength and may break in the furnace, causing poor ventilation. Means to Solve] The above problem is solved by setting the ore layer thickness/coke layer thickness ratio on the wall side of the blast furnace to 0.45 to 0.55, and the ore layer thickness/coke layer thickness ratio in the center of the blast furnace to 0.25 to 0. .35, and the problem is solved by a blast furnace raw material charging method characterized by charging pellets into the center of the blast furnace.

In order to obtain such an ore layer thickness/coke thickness ratio, pellets and coke can be charged by using a movable armor and changing the extrusion point appropriately, or by charging pellets and coke by using a bellless method. Charging can be carried out by changing the tilting angle and number of turns of the chute as appropriate. Coke may be charged into the center, or into the wall, or from the wall. It is more preferable if the coke is mixed into the blast furnace, since percolacetic carbon occurs and coke with a relatively large particle size gathers in the center of the blast furnace, increasing the porosity.

In the present invention, pellets may be charged into the center of the furnace, and other ores, such as sintered ore, do not necessarily need to be charged into the center.

[Operation] Pellets are charged into the center of the furnace, and the ore layer thickness on the wall side of the blast furnace is
When the coke layer thickness ratio is set to 0.45 to 0.55° and the ore layer thickness/coke layer thickness ratio at the center of the blast furnace is set to 0°25 to 0.35, the ratio of pellets in the furnace wall is reduced, and , fluid segregation of pellets, and mixing with coke do not occur, increasing the stability of ore distribution.

In addition, the ore layer thickness/coke layer thickness ratio on the wall side of the blast furnace was set to 0.4.
5 to 0.55, and the ratio of ore layer thickness/coke layer thickness at the center of the blast furnace to 0.25 to 0.35, combined with charging the pellets to the center of the furnace, the porosity of the center of the furnace increases. As a result, in the center of the furnace, the CO gas potential in the temperature range of too much degrees Celsius or higher increases, and a central flow is ensured. By increasing the CO gas potential in a temperature range of too much degrees centigrade or higher, the reduction rate also increases, and as a result, it is possible to prevent a sudden decrease in furnace heat due to an endothermic reaction.

[Example of the Invention] Ore containing 5% by weight of pellets and 80% by weight of sintered ore was charged onto coke using a movable arm (Example 1); Ore containing 40% by weight and 50% by weight of sintered ore was charged into the center of the furnace (Example 2), coke and ore were charged alternately,
The ore layer thickness/coke layer thickness ratio on the wall side of the blast furnace and the ore layer thickness/coke layer thickness ratio at the center of the blast furnace were distributed as shown in FIG.

In this example, coke was charged to the furnace wall side.

When the furnace was operated at such an ore layer thickness/coke layer thickness ratio, the gas flow velocity distribution was high in the center and low on the wall side, as shown in Figure 8, forming a central flow. . Such a distribution has a beret/ ) of 5
Not only in the case of weight% (Example 1) but also when the pellets were 40
There was no change in the case of weight % (Example 2).

Furthermore, when the Co gas potential was measured, as shown in FIG. 6, it was 0.8 or more at temperatures above 1000°C. Since the ratio is not changed, the stability of the charging distribution can be increased without causing a decrease in yield or strength, and it is possible to eliminate reduction stagnation of pellets.

[Brief explanation of drawings]

FIG. 1 is a graph showing the distribution of the ore layer thickness/coke layer thickness ratio and the gas flow rate. FIG. 2 is a graph showing the relationship between pellet blending ratio and ore inclination angle variation coefficient. The t53 diagram is a graph showing the relationship between the pellet blending ratio and wind pressure fluctuation. FIG. 4 is a graph showing the relationship between pellet blending ratio and solution filtration C. FIG. 5 relates to a conventional example, and FIG. 5(a) is a graph showing the relationship between temperature and reduction rate in the case of sintered ore. FIG. 5(b) is a graph showing the relationship between temperature and reduction rate in the case of pellets. FIG. 5(C) is a graph showing the relationship between temperature and Co gas potential. FIG. 6 is a graph showing the relationship between temperature and Co gas potential in an example of the present invention. 7 and 8 relate to an embodiment of the present invention, FIG. 7 is a graph showing the distribution of the ore layer thickness/coke layer thickness ratio, and FIG. 8 is a graph showing the distribution of the gas flow rate. FIG. 9 is a conceptual diagram showing coke entrainment. 2Φ: Coke layer, 4: Coke, 6: Pellet layer. Furnace wall Fig. 2 Pellet blending ratio 00 Fig. 3 Pellet blending ratio (%) Pellet blending ratio (%) (c) aF C'c) Temperature ("O) Temperature (℃) Fig. 7 Fig. 8 Procedural amendment September 9, 1986

Claims (1)

[Claims] The ore layer thickness/coke layer thickness ratio on the wall side of the blast furnace is 0.45 to 0.55, and the ore layer thickness/coke layer thickness ratio in the center of the blast furnace is 0.25 to 0.35. , a method for charging raw materials into a blast furnace, characterized by charging pellets into the center of the blast furnace.