JP2769835B2 - Blast furnace operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is based on the use of coke with increased reactivity in a blast furnace and the use of low-reduced powdered sinter together with highly reactive coke. And a blast furnace operation method with improved productivity.

(Prior art) In a normal blast furnace, iron ore and coke are charged in layers from the top of the furnace, and the iron ore is reduced in the furnace, then reduced and melted to a metal state to produce hot metal. ing.

At this time, in order to operate the blast furnace stably,
According to Japanese Patent No. 174403, in the blast furnace operating method in which iron raw material and coke are sequentially charged and refined in the blast furnace, when charging the coke into the blast furnace, an average of 15 to 25 mm around the furnace is constantly or intermittently charged. A method of operating a blast furnace characterized by charging small coke having a particle size of large coke having an average particle size of 35 to 70 mm in the center of the furnace and operating the same is disclosed.

Further, the present inventors have disclosed in Japanese Patent Application No. 62-193457
mm or less, the high-reactivity coke is mixed with ordinary coke or ore and charged into the blast furnace, thereby lowering the heat storage zone temperature of the blast furnace and increasing the reaction efficiency of the blast furnace. A blast furnace operation method to enhance was proposed.

(Problems to be Solved by the Invention) However, by charging large coke having an average particle size of 35 to 70 mm in the center of the furnace and small coke having an average particle size of 15 to 25 mm in the periphery of the furnace, It is thought that the ventilation permeability of the furnace core in the center of the furnace can be ensured and stable operation is possible. However, in the operation using ordinary coke, the reaction efficiency of the blast furnace cannot be improved.

On the other hand, in order to improve the reaction efficiency of the blast furnace, it is effective to use a small lump highly reactive coke mixed with ore or coke. Since the reactor is charged so as not to reach the center of the furnace, the reduction efficiency of the center of the furnace does not improve, and the reaction efficiency in the entire radial direction of the blast furnace is hardly improved. In addition, if small coke high-reactivity coke is charged into the center of the furnace by charge distribution control, the reaction efficiency can be improved in the entire blast furnace radial direction, but there is a problem with the permeability of the core in the center of the furnace. It hinders stable operation.

Also, even when the reaction efficiency can be improved and low fuel ratio operation is possible, as is often seen during low fuel ratio operation,
If the gas flow becomes unbalanced and a region with a small gas flow rate is generated in the blast furnace shaft, a low-temperature heat preservation zone of 600 to 700 ° C will be easily generated. As a result, poor ventilation of the shaft portion of the blast furnace occurs, which often delays ore reduction and impairs the load, which hinders stable operation of the blast furnace in many cases.

Therefore, in the present invention, by increasing the reactivity of coke charged into the blast furnace, and separating and charging large coke and small coke, the heat storage zone temperature is reduced, and iron ore of the entire blast furnace is reduced. To promote stable production of hot metal with high reaction efficiency and high reaction efficiency, and to suppress the increase in the powder ratio due to sinter reduction powdering, which is likely to occur under low fuel ratio operation. And to operate the blast furnace stably.

(Means and Actions for Solving the Problems) The blast furnace operation method of the present invention has the following features.
In a blast furnace in which coke is separated into large and small lumps, high-reactivity coke is separated into large and small lump, large lump high-reactive coke is placed in the center of the furnace, and small lump highly reactive coke is placed in the furnace. By charging the furnace from the middle part to the periphery of the furnace, it is possible to ensure ventilation and liquid permeability of the furnace core at the center of the furnace, improve the reduction efficiency of the entire blast furnace, and enable low fuel ratio operation. . In addition, the high-reactivity coke is separated into large lump and small lump, and when the large lump high-reactivity coke is charged into the furnace center and the small lump high-reactivity coke is charged into the furnace periphery from the middle of the furnace, Stable blast furnace operation by charging low-reduced powdered sinter together with liquefied coke, and suppressing the increase in the powder rate due to sinter reduced-pulverization, which is likely to occur under low fuel ratio operation. It is characterized by.

 First, highly reactive coke will be described.

The highly reactive coke used in the present invention is JISK2151-19
30% JIS reactivity as measured by the reactivity test method of 77
It is desirable that this is the case. If the value is less than 30%, the heat storage zone temperature described below hardly decreases. Further, it is necessary to maintain high strength even for highly reactive coke, and it is desirable to maintain the same strength as normal coke.

As a method for preparing highly reactive coke having high strength,
There is a method of adding an alkaline aqueous solution to high-strength ordinary coke, or a method of forming and drying a common coal.

The high-reactivity coke is replaced with a part or all of the coke usually charged from the furnace top, and the high-reactivity coke is separated into large and small lumps, and the large lumps are mixed with normal coke, or The iron ore is charged separately and layered into the center of the furnace alone. The lumps are charged from the middle of the furnace to the periphery of the furnace in a mixture with iron ore and / or ordinary coke, or are separately charged separately and layered with iron ore.

In the present invention, the furnace center is defined as the furnace opening radius of the blast furnace at 20 mm.
%, For example, if the furnace opening radius is 5 m, the area within 1 m radius is called the furnace center. The outside of the furnace wall excluding the furnace center is referred to as the furnace middle to the furnace periphery.

It is desirable that the particle size of iron ore and / or highly reactive coke mixed and used with ordinary coke to be charged from the middle part of the furnace to the periphery of the furnace is 15 mm or less. If the particle size is 15 mm or less, the surface area per unit weight of coke increases, and the proportion contributing to the reaction increases.

Since this highly reactive coke has high reactivity, the interfacial reaction in which CO ₂ in the furnace comes into contact with CO on the coke surface is smoothly performed. Further, as a result, the reaction that the CO gas generated in the furnace effectively reacts with the iron ore to reduce to a lower oxide or a metal state is promoted.

The gasification reaction of coke of C + CO ₂ = 2CO is an endothermic reaction, and can lower the temperature of the heat storage zone in the blast furnace shaft. For example, according to the conventional method, a heat storage zone of about 1000 ° C. is generated and its value hardly changes, but by using a highly reactive coke,
It is possible to reduce the temperature of the heat storage zone to 900 to 950 ° C. As a result, since the reduction equilibrium reaching point has a margin, the reduction proceeds more, the shaft efficiency, the indirect reduction rate, and the CO gas utilization rate are improved, and the coke ratio can be reduced.

In addition, by introducing high-reactivity coke with a particle size of 35 to 70 mm as a large lump high-reactivity coke into the center of the furnace, the air permeability of the core in the center of the furnace is ensured, and stable operation becomes possible. In addition, since the reduction of the iron ore charged in the center of the furnace is promoted, the reduction efficiency in the entire blast furnace radial direction can be improved.

 Next, reduction and reduction of sintering powder will be described.

The use of high-reactivity coke can improve the reduction efficiency, which makes it possible to operate with a significantly reduced fuel ratio. The amount tends to increase. Especially for the blast furnace shaft
When a low-temperature heat storage zone of 600 to 700 ° C is generated, the amount of reduced ore sintering of the sinter increases remarkably, which hinders safe operation of the blast furnace.

As a countermeasure for this, all the ordinary sinters are replaced with low-reduced powdered sinters and charged together with highly reactive coke. Or, usually, ordinary sinter is charged, and while detecting the formation of a low-temperature heat storage zone of 600 to 700 ° C, when the low-temperature heat storage zone occurs, the normal sinter is charged. Stop and charge the whole amount of low-temperature reduction powdered sinter.

The production of low-reduced powdered sinter is possible by adjusting the blending of raw materials in the sintering operation and adjusting the operation (such as changing the basic unit of coke). It can also be produced by adding an aqueous solution.

Fig. 1 shows the relationship between the reduction powder index (RDI) of sinter, the JIS reduction rate and seawater immersion time. When immersed in seawater for about 5 seconds, the RDI of sinter is 35%. While the sinter ore JIS reduction rate remains unchanged while the -40% reduction to 15%, the addition of seawater to the sinter does not affect the reducibility of the sinter ore and has an effect on reducing powder reduction. Demonstrate.

For RDI, the sample (15-20 mm, 500 g) was reduced with a reducing gas (CO 30% -N ₂ 70%, 15 NI / min) at 550 ° C. for 30 minutes, and then 900 revolutions (30 rpm × 30 minutes) with a rotation tester. It is indicated with a weight percentage of -3 mm later. The reduction rate of the sintered ore is represented by the reduction rate after 180 minutes at 900 ° C measured by the JIS method.

(Examples) Hereinafter, features of the present invention will be specifically described with reference to examples.

Table 1 shows the blast furnace operation using high-reactivity coke and low-reduced powdered sinter in comparison with the conventional method.

Subject blast furnace is a medium-sized blast furnace having an inner volume of 3000 m ^3, the conventional method was charged with iron ore and ordinary coke in a ratio of O / C = 3.2 from the furnace top, 2270 ° C. wings preoral flame temperature (hot air temperature 1100 ° C. ,
Hot metal was manufactured while maintaining the added moisture at 35 g / Nm ³ and no pulverized coal injection) (Comparative Example) In Example 1, the total amount of normal coke was high reactive coke (JI).
S reactivity 50%), the particle size 50mm or more is 20%,
The particle size is less than 50mm 80% and the sinter is usually sinter (RD
I40%) is sprayed with seawater to make low RDI sintered ore (RDI 20%).

Example 2 is an example in which 50% of normal coke was replaced with high-reactivity coke (JIS reactivity 50%).
0%, particle size 15mm or less is 30%, and the sinter is usually low RDI sinter (RDI 40%) sprayed with thickener water.
I22%).

As for the charging method, in the case of Example 1, a large lump of highly reactive coke was charged into the center and a small lump was charged from the middle of the furnace to the periphery, and charged alternately with the sinter. In the case of Example 2, large lump highly reactive coke is mixed with normal coke and charged into the center of the furnace, and small lump coke is usually mixed with coke and sinter at a ratio of 1/2, and from the middle of the furnace. Charged to the surrounding area.

In the examples shown in Table 1, the gas utilization rate was improved and the coke ratio was reduced as compared with the comparative example, and the fuel ratio was able to be reduced.

(Effects of the Invention) As described above, in the present invention, high-strength highly-reactive coke is separated into large lumps and small lumps, and the large lumpy high-reactivity coke is placed at the center of the furnace. Charging coke into the periphery of the furnace from the middle of the furnace ensures the permeability of the furnace core at the center of the furnace and lowers the temperature of the heat preservation zone, thus increasing the shaft efficiency. It is also possible to increase the gas utilization rate of the entire blast furnace and to operate the blast furnace with a low coke ratio. Furthermore, stable operation can be performed for a long period of time by suppressing the increase in the powder ratio due to the reduction and pulverization of sinter ore, which tends to occur at a low fuel ratio.

Thus, according to the present invention, the productivity of the blast furnace operation can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the sinter ore RDI, JIS reduction rate and seawater immersion time.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C21B 5/00

Claims (2)

(57) [Claims] In a blast furnace in which coke is separated into large lumps and small lumps and charged, high-reactivity coke is separated into large lumps and small lumps, and large lumps and high-reactivity coke are placed at the center of the furnace. A blast furnace operating method, wherein reactive coke is charged from the middle of the furnace to the periphery of the furnace. 2. The method according to claim 1, wherein the highly reactive coke is separated into large lumps and small lumps.
At the time of loading the large lump highly reactive coke into the furnace center and the small lump highly reactive coke into the furnace periphery from the middle of the furnace, charge the low-reduction powdered sinter together with the highly reactive coke. A blast furnace operating method, characterized in that: