JPH02228408A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To easily cause ascending gas in a furnace to flow into center part and to stably operate the blast furnace at good efficiency by charging ore into circumference of the center part after charging solid reducing agent into the specific range in the center part of the blast furnace, repeating the above charging at plural times and forming the ore layer. CONSTITUTION:The solid reducing agent and the ore are charged from the top part of the blast furnace, in order to laminate the solid reducing agent layer and the ore layer, and by blowing hot blast from the tuyere, the reducing gas is generated and ascended, and the ore is reduced and allowed to flow down. In the above blast furnace operation method, at the time of forming the optional ore layer in the above ore layer, charge of the ore is divided into plural times. Further, after charging the solid reducing agent into the specific range in the center part of the blast furnace, the ore charging is executed at each time so as to charge the ore into the circumference thereof. By this method, the solid reducing agent charging rate into the center part can be easily and optionally increased. Further, the reducing reaction of the ore is progressed earlier at the position in the center part and the ascending gas in the furnace is made to flow in the center part. Further, shape of softed melting zone is made as sharp reverse V-shape and the blast furnace is stably and efficiently operated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of operating a blast furnace by charging a solid reducing agent and ore from the top of a blast furnace and stacking a solid reducing agent layer and an ore layer. In this method, a solid reducing agent is charged into the shaft center of the blast furnace to make the gas rising in the furnace into a central flow, maintain the shape of the softened and fused body in a sharp inverted V shape, and improve the ventilation and liquid flow of the furnace core. This relates to blast furnace operating methods to maintain proper properties. In this specification, the explanation will mainly be based on the case where coke, which is the most typical solid reducing agent, is used.

[Prior Art] In order to operate a blast furnace stably and efficiently, it is important to appropriately control the gas flow distribution rising inside the furnace. For example, Figure 7 is a schematic cross-sectional diagram showing the operational status of a blast furnace.
In the figure, OA is the ore layer, CA is the coke layer, K is the massive zone, and S
M is a softened cohesive zone, Co is a furnace core coke layer, L is a raceway, B is a tuyere, F is a hot metal, and E is a tap hole. That is, ore 0 and coke C, which are alternately charged from the top of the blast furnace, gradually descend while forming layers, and the reducing gas (C
Due to the action of O), ore 0 is reduced in the process of falling through the lumpy 'tK, and after forming softened and fused isM, the core coke layer CO
It travels through the gaps and accumulates at the bottom of the furnace. And this hot metal F is
It is extracted periodically or continuously from the tap E.

Many proposals have been made regarding control methods to improve the efficiency and stability of blast furnace operation, but the current almost established idea is that, for example, Japanese Patent Laid-Open No. 60-56003 filed by the applicant of the present invention As already described in the official gazette and also disclosed in Japanese Patent Publication No. 61-42896 and Japanese Patent Application Laid-Open No. 61-227109, the blast furnace rising gas is made into a central flow, and the shape of the softened cohesive zone SM is made into an inverted V-shape. It is said that operational efficiency is highest and most stable when maintained. Therefore, as a means to ensure such operational conditions, various improvement studies are being carried out on the charging method of ore 0 and coke C, the stacked shape, air permeability, etc.

The inventors of the present invention have been conducting research for some time with the aim of improving the efficiency and stability of blast furnace operation. As a result of examining the simulation, we were able to clarify the following facts.

Figures 8(^) and (B) are schematic longitudinal cross-sectional views showing the relationship between the permeability of the axial center of the massive zone K and the operating conditions;
If the central part of the block fK has good ventilation,
Since the blast furnace rising gas is oriented toward the center, the reduction reaction of the ore occurs faster at the axial center than at the periphery (i.e., at a higher position).
As a result, the softened cohesive zone SM is shown in Figure 8 (A
), it is stable in a sharp inverted V-shape. However, when the permeability of the shaft center becomes poor, the rising gas has no choice but to be directed toward the peripheral wall of the blast furnace due to the large ventilation resistance.As a result, an area where the early reduction reaction progresses is formed on the peripheral wall as well, and the softened cohesive zone SM is As shown in FIG. 8(B), the furnace takes on a W-shape, and wind pressure fluctuations, increased heat loss to the furnace wall side, unloading abnormalities, etc. occur frequently, and the operating conditions become extremely unstable.

N9 diagrams (A) and (B) are vertical cross-sectional schematic diagrams for explaining the influence that the permeability of the furnace core coke layer Co has on the furnace condition, and when the permeability of the furnace core coke layer CO is good,
The hot air blown from the tuyere B easily advances to the center of the core coke layer Co, which has good ventilation.
As shown by the white arrow in Figure (A), the amount of gas closer to the reactor axis increases, the rising gas forms a central flow, and the shape of the softened cohesive zone SM is also stably maintained in an inverted V-shape. In contrast, Fig. 9 (
B) shows the situation when the permeability of the core coke layer Co is poor, and because the ventilation resistance of the furnace core coke layer Co is large, the hot air blown from the tuyere B has to be diverted toward the blast furnace wall. As a result, ore 0 in the peripheral area begins to undergo reduction from an earlier position (higher position) as in the case of Fig. 8 (B), and as a result, the softened and fused fsM becomes W-shaped and the furnace The ventilation resistance in the height direction on the side closer to the wall becomes even smaller, the peripheral flow of rising gas is further promoted, and the furnace condition becomes even more unstable.

On the other hand, Fig. 10 (^) and (B) show the furnace core coke layer co
Fig. 10 (A) is a schematic cross-sectional view of the hearth section showing the influence of liquid permeability on the furnace condition. As shown, the hot metal F flows evenly from the entire hearth, including the center of the hearth, in the direction of the tap E, so the walls around the hearth bottom are not intensively eroded. If the coke layer co has poor liquid permeability and therefore the liquid permeation resistance in the furnace core is large,
As shown by the solid arrow in FIG. 10(B), the hot metal F during tapping is forced to form a peripheral flow, and the peripheral wall of the furnace bottom is subject to significant erosion.

Therefore, based on these facts, the present inventors aimed at controlling the air permeability or liquid permeability of the furnace core coke layer Co.
He developed a method of separately charging coke (solid reducing agent) into the core of the top of the furnace, and completed a separate invention (Patent application No. 62-2209).
No. 81).

This invention focuses on the fact that the core coke layer CO is renewed by the coke that descends down the shaft center of the blast furnace. The air permeability and liquid permeability of the furnace core are appropriately controlled by charging C or appropriately charging coke suitable for improving air permeability and liquid permeability in the axial center region of the coke layer. It was full of stuff. Further, according to the present invention, the amount of coke charged into a specific region of the shaft center portion is specified to be 0.2% by weight or more of the total coke charged.

[Problems to be Solved by the Invention] By the way, the purpose of charging coke into the core can be achieved by using a chute exclusively for charging the core.

Fig. 11 is an explanatory diagram showing an example of the axial center charging method. This figure shows the case of a bell-type blast furnace, in which coke C is charged only to the axial center at the top of the furnace, separate from the raw material charging bell. A chute 4 is provided for entry. In addition, when carrying out shaft center loading, there are cases where it is carried out using the bell removable method.
The procedure is almost the same in this case as well.

The coke layer CA is formed by charging the coke all at once (or in several batches) from the bell. To form an OA with an ore layer on top of it, before charging ore 0, a predetermined amount of coke C is first charged from the chute 4 to the axial center of the furnace top. Figure (A) ], then ore 0 is charged from bell 1 to the surrounding area [Figure 11 (B)
]. Then, since the furnace top axis is occupied by coke C, this acts as a weir, and ore 0 cannot flow into the furnace top axis, and as a result, the peripheral side of the furnace is the ore layer OA and the coke layer. A normal stacked structure in which CAs overlap each other is formed, but the core of the furnace becomes a columnar layer consisting essentially only of coke. In order to form one ore layer, the ore may be charged in several batches, but even in that case, the coke from the chute to the core of the furnace is injected all at once before the ore is introduced. [See the explanation regarding FIG. 1 CB) and FIG. 5(B) described later].

However, with the conventional coke core charging method, it is difficult to charge 0.2% or more coke into the furnace core without reducing productivity (operational workability) based on the total coke charged. , relatively large-scale equipment (for example, the chute 4
), which raised the problem of increased equipment costs.

Furthermore, even if an attempt is made to increase the amount of ore input from the perspective of improving blast furnace operation, there is a limit to the ability to arbitrarily increase the amount of coke charged at the shaft center in accordance with the increase in the amount of ore charged. Even if only the amount of ore is increased relative to coke, the coke will be covered with ore, and this coke will not contribute to improving gas flow distribution controllability.

The present invention has been made in view of these circumstances, and its purpose is to develop a system that can arbitrarily increase the amount of coke charged in the core even using existing equipment, or to develop a large-scale system. It is an object of the present invention to provide a blast furnace operating method that allows optimum shaft center charging even without the provision of such a method.

[Means for solving the problem] The structure of the method of the present invention that can achieve the above object is as follows:
A solid reducing agent and ore are charged from the top of the blast furnace, and the solid reducing agent layer and ore layer are stacked to operate the blast furnace. Divide into multiple times, and when charging ore each time,
The gist of this method is to charge a solid reducing agent into a specific region of the blast furnace axis, and then charge ore around it to form an ore layer and operate the blast furnace.

[Function and Examples] The main point of the present invention is that the coke charged into the axial center of the ore layer is not charged all at once in one charging operation as in the past. It has been found that the above object can be successfully achieved by charging a plurality of batches and dividing the coke into each batch.

For convenience of explanation below, each coke layer CA and each ore layer OA
Although the case where each batch is formed in two batches is shown, this does not limit the number of batches when carrying out the present invention.

Figure 1 is a conceptual diagram showing the deposition situation in the blast furnace.
A) shows normal blast furnace operation, FIG. 1(B) shows conventional shaft charging, and FIGS. 1(C) and (D) show shaft charging according to the method of the present invention. . In addition, CI in the figure,
C2 is the coke charged for each batch, ol, 0
2 indicates the ore charged for each batch.

In conventional coke axial charging, as shown in Figure 1 (B), the coke was charged at once before the ore ol was charged (that is, after the coke C2 was charged). In the method of the invention, core-charging coke C is charged to a specific area of the blast furnace shaft prior to each batch of ore 01.02, so that the entire core can be charged without increasing the amount of coke for each charge. It was possible to increase the amount charged. If you only want to increase the amount of coke charged at the core of the blast furnace, it is possible to use the method shown in Fig. 1 (B). [indicated by r in Figure (D)] may be expanded carelessly, and there is a concern that the original effect of coke axial charging may not be achieved.

According to experiments conducted by the present inventors using an existing device, it has been found that by carrying out the split injection multiple times according to the present invention, each charge (here, charge is shown in FIG. 11(A))
The units indicated by U, namely the coke layer OA and the ore layer O
It is possible to arbitrarily increase the total amount of coke axially charged (meaning the basic charging unit in a laminated state completed by both A and A), and in the example shown in Fig. 1, from 400 kg to 600 kg.
kg.

The weight is gradually increased to 1,000 kg, and this 100
0 kg was an amount equivalent to about 3% of the total amount of coke charged. In this way, as the amount of coke charged in the shaft center was increased, the central gas flow was stabilized and the number of slips was reduced, and the PC ratio (ratio of coal powder blown in from the tuyere) was also increased accordingly. Until now, when increasing the PC ratio, there had been concerns about an increase in heat load and pressure loss on the furnace wall, but by adopting axial center charging and adjusting the armour-notch, increases in heat load and pressure loss could be suppressed, and the SL during pig iron It was possible to operate without raising the temperature.

Figure 2 is an isothermal diagram showing the situation inside the furnace, and Figure 2 (A)
is for normal blast furnace operation (without core charging)
, Figure 2 (B) shows the amount of coke charged in the shaft center at 500 kg/
When charged (6.9 kg per ton of hot metal),
FIG. 2(C) shows the case where the amount of coke charged in the shaft center is 1000 g/charge (14.0 kg per ton of hot metal).

As is clear from FIG. 2, as the amount of coke charged in the shaft center increases, the shape of the cohesive zone takes on a sharp inverted V-shape. The PC ratio at this time is shown in Figure 2 (
Case A) is 65 g/l (per ton of hot metal), Figure 2 (B) is 74 g/11, Figure 2 (C) is 7
It was 7Kg/l.

Furthermore, as the amount of coke charged at the core increases, the gas temperature at the furnace mouth increases as shown by the arrow in Figure 3, and as shown in Figure 4, the gas temperature at the core at the furnace mouth increases. There are fewer fluctuations.

In the above explanation, the case where the amount of coke charged in the shaft center for each charge is arbitrarily increased is shown, but the present invention is not limited to such a case, but can also be implemented from the viewpoint of reducing the size of the equipment. is also valid. For example, FIG.
The figure is a conceptual diagram showing the in-furnace deposition situation according to the method of the present invention. It is clear from a comparison of Figure 5.6 that when forming ore layers of the same thickness (0, 1+02), the central issue is to form a columnar layer of coke at the axial center. Therefore, in the method of the present invention (FIG. 6) in which coke is charged in parts, the amount charged each time can be reduced to about 1/4 compared to the case in which coke is charged at once (FIG. 5).

This also means that the device dedicated to charging coke in the shaft center can be made smaller. Further, even if it is assumed that the same amount of coke is charged into the shaft center, the apparatus can be made smaller by charging the coke in parts. These things are extremely effective from the viewpoint of improving the controllability of gas flow in the blast furnace.

The structure of coke axial charging in the above explanation was such that more than a certain amount of coke was charged into the axial center of the ore layer OA when the ore layer OA was formed, but the axial center coke layer C
Considering the purpose of stabilizing blast furnace operation by improving the air permeability or liquid permeability of 0, coke for shaft core charging has strong cold and hot strength and is difficult to powder (i.e., has low liquid permeability). It is more effective to charge a certain amount or more of high quality coke. Furthermore, in carrying out the present invention, it is not necessary to charge the coke at the center of the coke for each charge, but the coke may be charged at the center of the shaft at any charge selected from 2 to 5 charges.

[Effects of the Invention] The present invention is configured as described above, and even if the existing installation is used, the amount of coke charged in the shaft center can be increased arbitrarily, and stable blast furnace operation is guaranteed. The method of the present invention is also effective in that optimum coke core charging can be achieved without the need for large-scale equipment.

[Brief explanation of the drawing]

Figures 1 (^) to (D) are conceptual diagrams showing the deposition situation in the blast furnace;
In Figure 2, (A) to (C) are isothermal diagrams showing the situation inside the furnace, Figure 3 is a graph showing the gas temperature distribution in the radial direction of the furnace, and Figure 4 is a graph showing the amount of coke axially charged and the furnace temperature. A graph showing the relationship between center-of-mouth gas temperature fluctuations, FIG. 5 is a conceptual diagram showing the deposition situation in the furnace by the conventional axial center charging method, FIG. 6 is a conceptual diagram showing the deposition situation in the furnace by the method of the present invention, and FIG. Figure 7 is a vertical cross-sectional schematic diagram showing the internal situation during blast furnace operation, and Figures 8 (A) and (B).
Figure 9 (A) and (B) show the relationship between the permeability of the furnace core coke layer and the shape of the softened cohesive zone. A schematic vertical cross-sectional view, Figures 10 (A) and (B) are a schematic cross-sectional view showing the liquid permeability of the core coke layer and hot metal flow distribution, and Figure 11 (A).
, (B) is an explanatory diagram showing an example of a shaft center insertion method. 1...Bell 4...Shoot OA...
Ore layer CA...coke layer K...massive
B...Tuyere L...Raceway CO・
・・Furnace core E・・Outlet C, C1, C2・・・
・Coke 0, 01.02...Ore

Claims (1)

[Claims] A method of operating a blast furnace by charging a solid reducing agent and ore from the top of the blast furnace and stacking a solid reducing agent layer and an ore layer, the method comprising: charging the ore when forming an arbitrary ore layer among the ore layers; The ore is charged in multiple times, and each time the ore is charged,
A blast furnace operating method characterized by charging a solid reducing agent into a specific region of the blast furnace shaft center, and then charging ore around it to form an ore layer and operating the blast furnace.