JPS5842707A - Construction for refractory lining of blast furnace - Google Patents

Abstract

PURPOSE:To prevent the abnormal damages of refractories for lining of the well part and bottom part of a blast furnace by using refractory bricks of SiC base or SiC-C base for the lower step on the side wall of said wall part and the upper step of the bottom part. CONSTITUTION:Of the refractory bricks for lining of a blast furnace, at least the lowermost step 2A of refractory bricks 2 on the side wall in a well part and at least the uppermost step 3A of refractory bricks 3 on the side wall in a bottom part are built of bricks of SiC base or SiC-C base contg. >=60wt% SiC. The SiC or SiC-C bricks has high oxidation resistance and the surfaces are coated with SiO2 glass by the reaction with CO and steam which are the atmospheric gases in the furnace, whereby the surfaces are made dense. Thus the oxidation and damage of the side walls in the well and bottom parts are suppressed and the life of the blast furnace are prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the refractory lining structure of a blast furnace, and in particular to a refractory lining structure for a blast furnace which prevents abnormal damage to the refractories in the sump and bottom of the blast furnace. Regarding.

Conventionally, carbon bricks have been used to line the side walls of the sump and bottom of blast furnaces. This is due to its stable hot properties, low dissolution into hot metal, high thermal conductivity, and cooling of the iron skin to form a solidified layer of hot metal on the brick surface inside the furnace, which is effective in completely protecting the bricks. Due to certain reasons.

However, in recent years, as blast furnaces have become larger and operating conditions have become more severe due to high pressure operation, etc., there has been a noticeable tendency for a porous layer to be formed in the carbon bricks in the sump and bottom of the blast furnace.

When a porous layer is formed on the carbon brick, this part acts as a heat insulating layer, reducing the cooling ability from the steel shell and causing the temperature of the lining brick on the working side to rise. Become.

When the temperature of the brick increases.

If the carbon in the hot metal is not saturated, the carbon bricks will dissolve into the hot metal, resulting in rapid wear of the bricks up to the insulation layer, which causes the inconvenience of shortening the lifespan of high FC). .

This invention was made in view of the above disadvantages, and
It is an object of the present invention to provide a refractory lining structure for a blast furnace that prevents abnormal wear and tear of carbon bricks on the side walls of the sump and the bottom of the furnace.

This invention provides that at least the lowermost stage of the side wall of the sump and at least the uppermost stage of the side wall of the bottom of the lining of the blast furnace are made of SiC or 5iC-C containing 60% by weight or more of Fi and SjC. The above purpose is achieved by using the bricks.

In other words, we analyzed the cause of the formation of a porous layer on the lining refractory bricks on the side walls of the sump and the bottom of the blast furnace.
In addition, in response to this cause, a refractory brick made of a material that is least likely to form a porous layer was sought, and a large resistant structure for the lining of a blast furnace was constructed using this material.

First, the formation of a porous layer in carbon bricks is caused by damage to the blower panels, cooling water flowing down to the lower part of the furnace, steam oxidation of the side wall bricks in the sump and the bottom of the furnace, and oxidation of Zn within the brick structure. There are two possible reactions: , and reduction.

Apparent porosity and foreign component Z in carbon bricks in the sump and furnace bottom side walls recovered from blowdown blast furnaces
The relationship with the amount of nO intrusion was as shown in FIG.

In other words, the apparent porosity shown by the solid line in Figure 1 is very large at the position inside the furnace and into the shell side. There is a dense layer with a small ratio.

Here, Zn in the carbon brick structure during blast furnace operation
The precipitation of O occurs when Zn vapor penetrates into the brick structure and is oxidized by the furnace atmosphere gas CO. Since the temperature at this time is Pcm=latm and 950°C, ZnO will precipitate in a temperature range of 950°C or lower. When ZnO precipitates within the brick structure, a dense layer with low apparent porosity is formed. Therefore, as shown in Figure 1, the phenomenon that a porous layer exists on the iron shell side, that is, on the low temperature side, from the ZnO precipitation area cannot be explained by the oxidation and reduction reactions of Zn, but is caused by water vapor. The oxidation of carbon bricks is thought to be the cause.

In other words, carbon bricks are oxidized at 500°C in air.
As mentioned above, the temperature during operation of the porous layer part of the recovered brick, which occurs under conditions of 700℃ or higher in steam, is
Estimated calculation using finite element method: 650-750℃
Therefore, it can be said that the porosity of carbon bricks is based on oxidation by water vapor.

As mentioned above, this water vapor is caused by cooling water flowing down to the lower part of the furnace due to damage to the blower panel.

Therefore, in order to prevent the formation of a porous layer in the carbon bricks in the sump and the bottom of the furnace, it is necessary to prevent cooling water from flowing down to the bottom of the furnace due to damage to the blower blades, and/or to provide oxidation resistance to the parts where oxidation occurs due to water vapor. It would be a good idea to take measures such as using materials with high susceptibility.

In order to prevent dissolution into hot metal, refractory bricks must be made of materials with high thermal conductivity, but after studying various materials with high thermal conductivity and excellent oxidation resistance, we found that It has become clear that SiC materials or 5iC-C materials containing 60% by weight or more of SiC have excellent oxidation resistance.

In other words, when SiC material or 5iC-C type large-resistant material containing 60 weight or more of SiC is treated in an atmosphere containing water vapor, the apparent porosity and air permeability decrease and the strength of these materials increases. It was found that conventional treatment of carbon bricks in the same atmosphere made the bricks porous.

This is due to the densification of the material due to oxidation of SIC,
Furthermore, if the SiC content is less than 60% by weight, the tendency of porosity due to oxidation of carbon by water vapor becomes greater than the tendency of densification due to oxidation of SiC, resulting in the formation of a porous layer. This is because it causes a decrease in thermal conductivity.

Specifically, as shown in Fig. 2, among the refractory linings of the blast furnace I (whole illustration omitted), the fewest of the refractory bricks 2 on the side wall of the sump (both the lowest stage 2A and the refractory side wall at the bottom of the furnace) At least the uppermost row 3A of the bricks 3 is made of the SiC material or a 5iC-C brick containing 601% or more of SiC.

In the figure, numeral 4 is the blast furnace body shell, 5 is the carbon stamp, and 6
indicate the air tuyeres.

In this way, the SiC or fisic-C bricks not only have great oxidation resistance, but also reduce the amount of CO in the atmosphere in the furnace.
By the reaction with the toy glass, the surface is coated with 5ins glass, and also by the reaction with water vapor, the surface is coated with the toy glass and becomes dense, thereby preventing oxidation.

It should be noted that the 5iC-C type bricks may be used for at least the two bottom rows of the side wall refractory bricks 2 of the sump and the top row 3A of the furnace bottom side wall refractory bricks 3. Therefore, two or more of the side wall refractory bricks 2 of the sump side wall including the bottom stage 2A, or two or more of the furnace bottom side wall refractory bricks 3 including the top stage 3A, are
IC-C bricks may also be used.

Since the present invention is configured as described above, it is possible to suppress the oxidation and wear of the side walls of the sump and the bottom side walls of the furnace due to water vapor caused by the flow of cooling water from the air blower, thereby dramatically extending the life of the blast furnace. It has the excellent effect of being able to

According to the inventor's experiments, the weight change due to heat treatment in an atmosphere containing water vapor is as shown in Fig. 3 for conventional carbon bricks and Fig. 4 for the bricks of the present invention. Ta.

These test specimens are 30m in diameter and 40I11 in length.
In a furnace maintained at 0°C, a Ni wire with a diameter of 0.5 ml (
1) Then, blow dry air or air at 90℃ and humidity 100℃ for 5 minutes.
These are the results of flowing at a ratio of 7/b and measuring the weight of the test piece using a thermobalance.

As can be seen from these figures, the conventional carbon brick showed a weight loss rate of Fi7 to IO after 5 hours under the above conditions, but the SIC brick of the present invention showed an almost linear weight loss rate up to 200 hours. Weight increase is observed, and the rate of increase is 1
It is a small value below . The SiC bricks used here contained 80% by weight of 5iC and 20% by weight of SsN, but in addition to Si3N+, SiC bricks
It may contain one or more of metal oxides, nitrides, and carbon such as t, Ale 03, and C.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the apparent porosity and the amount of ZnO intrusion in recovered conventional carbon bricks, and FIG. 2 is a cross-sectional view showing an example of the refractory lining structure of a blast furnace according to the present invention. Figure 3 is a diagram showing the weight loss rate due to the oxidation reaction of conventional carbon bricks, and Figure 4 is a diagram showing the weight increase rate due to the oxidation reaction of bricks used in the lining refractory structure of a blast furnace according to the present invention. be. Construction: Blast furnace, 2: Refractory bricks for the side wall of the hot water tank, 2 people.
...Bottom row, 3...Furnace bottom side wall refractory brick, 3A...
・Top stage, 4...Blast furnace main body skin, 5...Carbon stamp, 6...Blow tuyere. Agent Keisuke Matsuyama (and 1 other person)

Claims (1)

[Claims] (1) Among the refractory bricks lining the blast furnace, at least the lowermost stage of the side wall of the sump and at least the uppermost stage of the side wall of the bottom of the furnace are made of 5iC=C bricks containing SiC or SLC of 60 weight Jt or more. A blast furnace lining structure that can withstand large objects.