JPH07207310A - Operation of protecting side wall of furnace bottom of blast furnace - Google Patents

Abstract

PURPOSE:To prevent the generation of succeeding corrosion of a brick protecting layer and the erosion of the brick itself, etc., by taking the protecting countermeasure for the side wall part of a furnace bottom in accordance with the absolute value of the temp. indicated by a thermocouple. CONSTITUTION:The temp. at the side wall part of the furnace bottom is continuously measured by the thermocouple, and at the time of recognizing the temp. rising, the residual amount of the brick protecting layer is estimated from the relation between the indicated temp. before starting the temp. rising and temp. variable per the unit time. As the protecting countermeasure for the side wall of the furnace bottom, either one of the increase of charged TiO2, blast reduction and blowing down is executed in accordance with the residual amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operating method for protecting a bottom wall of a blast furnace.

[0002]

2. Description of the Related Art A factor that determines the life of a blast furnace is the remaining thickness of the refractory bricks on the side wall of the furnace bottom. If the protection can be done efficiently, the life can be extended, and the fixed cost can be greatly reduced and the blast furnace can be repaired. It is possible to reduce the influence on the production. Conventionally, various measures have been taken to protect the refractory bricks on the bottom wall of the furnace bottom, and these are classified as follows when the measures for protecting the bottom wall of the furnace bottom are viewed from the viewpoints of operation, work, and equipment. .

First, as a measure from an operational aspect, the amount of TiO ₂ charged is aimed at lowering the production level and promoting the production of a furnace bottom side wall brick protective layer (hereinafter referred to as a brick protective layer) by titanium bare (TiC / TiN). And the like. TiO
_{2 As} a concrete means for increasing the amount, Japanese Patent Laid-Open No.
There is an increase in the amount of charged TiO ₂ due to the blowing of finely divided TiO ₂ -containing material from the tuyere or the use of high TiO ₂ -containing ore as disclosed in Japanese Patent No. 297512. In addition, JP-A-6
Japanese Patent Laid-Open No. 4-39310 discloses a method of adding TiO ₂ to a filler used when closing a tap hole.

In terms of equipment, measures are taken such as increasing the amount of cooling water by adding a water pump and lowering the cooling water temperature by installing a refrigerator in order to improve the cooling efficiency at the side wall of the furnace bottom. In terms of work, it is possible to increase the amount of filler inserted when closing the taphole and to implement an irregular taphole usage method aimed at reducing the load on the taphole in the vicinity of the furnace bottom sidewall brick wear site. To be

When the above-mentioned protection measures for the bottom wall bricks of the furnace bottom are carried out, the decrease of the production level becomes a serious problem in a steel mill having no production capacity, and a large amount of cost is required for the measures for the facilities. In addition, work-related measures also have the problem of increasing the load on workers in front of the furnace. Therefore, as the simplest means, the degree of wear of the bottom wall bricks and brick protection layer,
That is, measures are taken to increase the amount of charged TiO ₂ according to the temperature indicated by the thermocouple.

[0006]

However, the heat transfer from the interface between the melt in the blast furnace and the brick protection layer to the thermocouple is
It is done through a brick protection layer and furnace bottom side wall bricks, etc., and it has been conventionally known that there is a delay of several hours before the indicated temperature of the thermocouple reaches a steady state after the wear of the brick protection layer. It was Therefore, there is a concern that further brick protection layer wear may occur inside the blast furnace (inside the bottom wall of the furnace) even if the furnace bottom side wall is protected according to the temperature indicated by the thermocouple. Further, since the disappearance of the brick protection layer leads to melting damage of the furnace bottom side wall bricks, the furnace bottom side wall bricks are also easily melted. The place to be the subject of the present invention is to prevent further erosion of the brick protection layer by the furnace bottom side wall protection measures according to the above-mentioned thermocouple indicated temperature absolute value and the occurrence of melting damage of the brick itself, etc. To provide the means.

[0007]

Means for Solving the Problems The present invention is to solve the above problems, and in a blast furnace having a thermocouple on the side wall of the furnace bottom, the temperature of the thermocouple is continuously measured, and the temperature rises by the measurement. If the residual amount of the brick protection layer on the bottom wall of the furnace bottom was estimated from the relationship between the indicated temperature before the start of temperature rise and the temperature change amount per unit time, and when the residual amount became less than the standard value, It is characterized by taking a predetermined operation measure such as increasing the amount of charged TiO ₂ , reducing the air flow, or taking a rest air.

[0008]

As described above, heat transfer from the boundary surface between the molten material in the blast furnace and the brick protection layer to the thermocouple is performed through the brick protection layer and the furnace bottom side wall brick. Therefore, it takes some time for the thermocouple indicated temperature to reach a steady state after the brick protective layer is worn. Therefore, in order to reliably protect the bottom wall of the furnace bottom wall, it is necessary to manage not the thermocouple indicated temperature but the process of wear of the brick protective layer, that is, the process of increasing the thermocouple indicated temperature. . Therefore, along with the findings obtained from the preliminary study described later,
The relationship between the thermocouple indicated temperature before wear of the brick protective layer and the amount of change in the indicated temperature per unit time was derived as shown in Fig. In the figure, the results of unsteady heat transfer calculation are stratified by the remaining amount of the brick protection layer.

In order to perform unsteady heat transfer calculation, the calculation model shown in FIG. 2 was constructed. The calculation model is represented by the following formulas (1) to (1) that are generally used when performing unsteady heat transfer calculation.
Using (4) as a basic formula, a model for calculating each cell was used. q (n + 1) = λ (n + 1) × [T (n + 1) -T (n)] / ΔL (1) q (n) = λ (n) × [T (n) -T (n-1) ] / ΔL (2) where q (0) = κ × [T (0) −Tw] / ΔL (3) T (n ′) = T (n) + [q (n + 1) -q (N)] / (Cp × ρ × ΔL) × Δt (4) where q: heat flux [kcal / m ² · hr] λ: thermal conductivity [kcal / m · hr · ° C] T: temperature [° C] ΔL: Minute length [m] κ: Overall heat transfer coefficient [kcal / m ² · hr · ° C] Cp: Heat capacity [kcal / m · hr · ° C] ρ: Density [kg / m ³ ] ΔT: Minute time [hr]

As a result of simulating the temperature change when the indicated temperature of the thermocouple increased in the side wall of the furnace bottom in the past using the calculation model, it was confirmed that the actual temperature transition and the calculation result accurately match. The results are shown in FIG. 3 (the circled numbers in the figure indicate the number of times the brick protective layer peeled off).
Further, from the simulation results, it was confirmed that the brick protective layer was worn several times before the melting damage of the furnace bottom side wall bricks occurred, and the brick protective layer was worn in layers and in stages. The results are shown in FIG. (The numbers at the top of the figure correspond to the circled numbers in Figure 3). That is,
It was found that it is possible to prevent the brick protection layer from disappearing and the brick itself from melting by controlling the process of wear of the brick protection layer.

Based on the above knowledge, in order to derive the relationship between the thermocouple indicated temperature before wear of the brick protective layer and the temperature change amount per unit time shown in FIG. 1, and to apply it to the existing blast furnace operation. Table 1 was established as the operation standard for furnace bottom side wall protection according to the remaining thickness of the brick protection layer.

[0012]

[Table 1]

[0013]

[Example] In a blast furnace operation with a furnace internal volume of 2884 m ³ ,
The thermocouple indicated temperature on the side wall of the furnace bottom increased from 230 ° C to 290 ° C in 8 hours as shown in Fig. 5. This allows
The residual thickness of the brick protection layer was estimated to be 25 mm or less from FIG. 1, and according to the operation standard shown in Table 1, the operation was temporarily stopped, that is, the air was blown off. As a result, the thermocouple indicated temperature on the side wall of the furnace bottom decreased as shown in FIG.

[0014]

[Comparative Example] FIG. 6 shows the temperature transition when the temperature rise in the above blast furnace was almost equal to that in the example. in this case,
In accord with the operation standard shown in FIG. 1 and Table 1, the bottom protection measures (Table 2) were implemented according to the absolute value of the thermocouple indicated temperature that has existed conventionally. As a result, the thermocouple indicated temperature increased even during the implementation, and the brick itself melted after the protective layer of the brick disappeared.

[0015]

[Table 2]

[0016]

As described above, according to the present invention, a quick response can be made as compared with the conventional control standard based on the absolute value of the thermocouple indicated temperature, further disappearance of the brick protective layer and the brick itself. Can be avoided in advance.

[Brief description of drawings]

1] Thermocouple indicated temperature and 8 before the brick protective layer peels off
Figure that stratifies the amount of rise in thermocouple indicated temperature per hour by the remaining amount of the brick protection layer

FIG. 2 is a diagram schematically showing a calculation model constructed to perform unsteady heat transfer calculation.

FIG. 3 is a diagram comparing the calculation result by a calculation model for estimating the amount of peeling of the brick protective layer and the actual temperature transition of the thermocouple.

FIG. 4 is a diagram schematically showing an aspect in which the brick protective layer is peeled off, which is confirmed by calculation results.

FIG. 5 is a diagram showing a thermocouple instruction temperature transition and an operation countermeasure in an example.

FIG. 6 is a diagram showing a thermocouple instruction temperature transition and an operation countermeasure in a comparative example.

Claims (1)

[Claims] 1. A blast furnace having a thermocouple on the side wall of the bottom of the furnace, the thermocouple temperature is continuously measured, and when a temperature rise is observed by the measurement, the indicated temperature before the start of the rise and per unit time The remaining amount of the furnace bottom side wall protective layer is estimated from the relationship of the temperature change amount, and when the remaining amount becomes less than the reference value, the increase / decrease / quiescent amount of the charged TiO ₂ is determined in advance. The operation method for protecting the bottom side wall of the blast furnace, characterized in that any one of the above operation measures is taken.