JPH01234508A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To obtain molten low Si iron without any changing the total coke cost, by mixing the coke having high reactivity with sintered ore, and by charging the mixture into the ore layer and the coke having low reactivity as it is into the coke layer. CONSTITUTION:The coke charging into a blast furnace is divided into two, which are the coke having high reactivity of corresponding quantity to 5-50% of the total coke charging wt. and the balance coke having low reactivity. Then, the above coke having high reactivity is mixed with the iron ore raw material to make the ore layer. Further, the above coke having low reactivity is charged in the coke layer as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a blast furnace operating method for reducing Si in hot metal.

[Prior Art] Various studies have been made to reduce Si in hot metal tapped from a blast furnace. It makes it easier.

The Si transfer reaction in the blast furnace can be considered as follows.

(a) SiO□(II) + C= SiO(g
) + Co(g)(b) SiO(g)+ C=
Si + Co (g) Mainly SiO in coke ash
2 reacts with coke at high temperature to generate SiO gas, which is reduced to C in the hot metal and becomes Si in the hot metal. Therefore, in order to reduce the amount of Si in hot metal, it is possible to increase the blending ratio of sintered ore in the charge, increase the basicity of the sintered ore, or add MgO to the charge. Improving the properties of the charge, such as ■ Decreasing the tuyere tip temperature by adding moisture to the blast and lowering the blast temperature, ■ Increasing slag basicity, ■ Decreasing the hot metal temperature, ■ Mill scale from the tuyere tip, etc. Injection of oxides, etc. have been proposed.

[Problems to be Solved by the Invention] However, each of the above-mentioned conventional techniques has problems and cannot be considered as a preferable technique. In other words, (2) increases the cost in any case, and there is an upper limit to the increase in basicity in sintered ore, so it is clear that it cannot be done as an economical and accurate method, and (2) increases the fuel ratio. Either this will increase the cost, or there will be restrictions on equipment, resulting in the same disadvantages as in (2). The method (2) is naturally limited because it affects the viscosity of the slag, and the method (2) is limited in terms of both iron tapping and slag tapping, so a sufficient reduction in Si cannot be expected. In addition, (2) is not only complicated in operation, but also has the same limitations as (2), so it cannot be considered a preferable method.

The present invention has been made in view of the above circumstances, and it solves the above problems, reliably reduces the Si content in hot metal to the desired level, and is economically sufficient without any special operational complications. The purpose is to provide a viable low-silicon operating method for blast furnaces.

[Means for Solving the Problems] The method of operating a blast furnace according to the present invention relates to the ore layer and the coke layer formed in the furnace by alternately charging iron ore raw material and coke from the top of the furnace. 5% to 5 of the input amount
0% of highly reactive coke (hereinafter referred to as high R
It is characterized in that it is mixed with iron ore raw material as I coke to form an ore layer, and the remaining amount of coke is used as low reactivity coke (hereinafter referred to as low RI coke) to form a coke layer.

When high RI coke is mixed with ore and charged into a blast furnace,
Because the ore is processed much more advanced than in the conventional method, the high-temperature properties of the raw material iron oxide are improved, the melting point becomes higher, so-called melting slows down, and the temperature rises. As a result, the cohesive zone level in the blast furnace decreases,
As the distance between the cohesive zone and the grain where the reaction (b) mainly takes place decreases, the Si○ gas generated from the ash in the coke is reduced to C in the hot metal dripping below the cohesive zone. There is less opportunity for the metal to enter the hot metal, and low-Si hot metal is produced. The high R echo mixed into the ore layer accounts for 5% of the total coke charge.
If it is less than 50%, the melting will drop and no effect of increasing the temperature will be seen, and if it exceeds 50%, the permeability will be inhibited due to coke powdering.

[Examples] Examples of the present invention will be described with reference to the accompanying drawings. Figure 1 shows the blast furnace 1 and raw material charging equipment used in the method of the present invention. FIG. 2 is the charging port at the top of the furnace;
3 and 4 are an ore layer and a coke layer formed in the upper part of the blast furnace, 5 is a cohesive zone in which the raw material is in a semi-molten state, 6 is a tuyere, and 7 is a sump. The shape or height of this cohesive zone varies depending on the operating conditions of the blast furnace. The raw material charging device 10 outside the blast furnace has a blending hopper 11, a hopper lower belt 12, and a charging belt 13. The blending hopper 11 also includes a plurality of bins each storing different types of raw materials. Bin 14 contains coke with high reactivity (hereinafter referred to as high RI coke), and bin 15 contains coke with low reactivity (hereinafter referred to as low RI coke).
(called coke) is stored in bins 16 and 17.1.
8 stores sintered ore, sintered pellets, and iron ore, which are raw materials for iron ore.

The operation of the apparatus shown in FIG. 1 constructed in this way will be explained. □Low RI coke stored in the bin 15 is directly transferred to the hopper lower belt 12 without being mixed with other raw materials.
The coke is then charged into the blast furnace from the charging port 2 of the blast furnace 1 via the charging belt 13 to form a coke layer 4. Next, the high RI coke stored in the bin 14 is transferred to the belt 12.1 together with the iron ore raw material stored in the bins 16 to 18.
3 and then charged into a blast furnace to form an ore layer on top of the coke layer. As described above, coke layers and ore layers are alternately formed in the blast furnace, and as the load is lowered, the temperature of the charged iron ore raw material rises due to hot air blown from the tuyere 6, and a reduction reaction progresses. Since the layer of iron ore raw material contains highly reactive high RI coke, reduction of the iron ore progresses, the proportion of Fe increases, the melt drops, the temperature rises, and the level of the cohesive zone increases. descend. On the other hand, since the low RI coke becomes the coke layer as it is, the coke layer has sufficient high-temperature strength and the ventilation inside the blast furnace is ensured.

Si generated from ash in coke generated in hot water pool 7
O gas is reduced to C in the hot metal dropped from the cohesive zone and becomes Si in the hot metal, but when the cohesive zone level is low, compared to when it is high, the SiO gas and the droplets of hot metal are The contact time is short, so the Si content in the hot metal is reduced.

Next, specific numerical examples of this example will be given. When we operated with 75% of the total coke charged as low RI coke in coke layer 4 and the remaining 25% as high RI coke in ore layer 3, Si in the hot metal was 0.28% compared to the conventional example. However, it decreased to 0.19%. In addition, the ventilation resistance is P
R and PO are respectively furnace top pressure (g/cm2, same below),
When the blowing pressure, ■ is the air volume (Nm3/min), and it is expressed as the ventilation resistance index K (-(PR2-Po2)/■17),
Although this was 2.77 in the conventional example, it was slightly larger to 2.79 in this example, but the difference was not significant enough to affect the furnace condition.

[Effects of the Invention] According to the present invention, highly reactive coke is mixed with sintered ore and charged into the ore layer, and less reactive coke is directly charged into the coke layer, thereby eliminating special operational complications. Low-Si hot metal can be obtained by an economically viable method without changing the total cost of coke.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a blast furnace and a raw material charging device used in the method of the present invention. 1...Blast furnace, 2...Charging direction, 3...Ore layer, 4...
Coke layer, 5... cohesive zone, 6... tuyere, 7... pool, 10. ...Raw material charging device, 11...Blending hopper, 12...Hopper lower belt, 13...Charging belt, 14 to 18...Bin.

Claims (1)

[Claims] In a blast furnace operating method for reducing Si in hot metal, an amount equivalent to 5% to 50% of the total amount of coke charged is added to the ore layer and coke layer that are alternately charged as raw materials from the top of the furnace. A blast furnace operating method characterized in that high coke is mixed with iron ore raw material and charged into the ore layer, and the remaining amount of coke is charged as low reactivity coke into the coke layer.