JPH0441610A - Method for restraining wear of carbon-containing refractory - Google Patents

Abstract

PURPOSE:To drastically reduce the wear of refractory in a metallurgical furnace for executing oxygen blowing operation without any adverse effect and to reduce production cost of molten iron, etc., by blowing the specific quantity of non-oxidizing gas into gaps in the carbon-containing refractory. CONSTITUTION:In the metallurgical furnace for executing oxygen blowing, spiral-state gaps are arranged in inner part of the carbon-containing refractory used to lining at upper space of molten material. During oxygen blowing operation, the non-oxidizing gas of nitrogen gas, etc., is blown through this gaps at 50-300Nm<3>/h per cross-sectional area (unit m<2>) of the refractory. At this time, the spiral-state gaps are made to the length (l) of one spiral-state gap two or more times the length L of refractory and ration of the gap diameter Dp to distance Db between the gaps (distance between one gap and the other gap) is made to >=0.01. By this method, cooling of the refractory is executed while the non-oxidizing gas passes through in the refractory, and as this result, surface temp. of the refractory is lowered. Further, by allowing the non-oxidizing gas to flow into the furnace, the oxygen partial pressure is lowered and coupled with both, the wear of refractory is made to reduce.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a metallurgical furnace for manufacturing molten metal or alloy by oxygen blowing, such as steel making or smelting reduction. The present invention relates to a method for suppressing wear under an oxidizing atmosphere.

(Prior Art) In recent years, oxygen gas has been widely used in the production of molten metals or alloys. This is because when oxygen gas is blown into a high-temperature furnace where carbonaceous materials are present, a high temperature is obtained by burning the carbonaceous materials, and ore reduction or scrap melting can be performed without using expensive energy such as electricity. Further, when oxygen is blown onto a molten metal or alloy containing carbon, decarburization occurs, and the heat generated at this time can be efficiently used to focus the molten material. However, it is an undeniable fact that the use of oxygen gas increases the load on the refractories of the metallurgical furnace, especially the refractories in the space above the molten material layer.

As a refractory for metallurgical furnaces, durability against slag erosion,
Also, from the viewpoint of spalling resistance, carbon-containing refractories such as magcarbon and alumina graphite have come to be widely used.

However, once the carbon content of this type of refractory is burned,
The drawback is that the resistance to slag rapidly decreases, and in metallurgical furnaces that perform oxygen blowing, the combustion of carbon determines the rate of wear of the refractory. Therefore, how to reduce wear and tear on refractories is a big problem, especially in processes with high oxygen consumption.

Combustion of carbon in carbon-containing refractories depends on the ambient temperature and oxygen partial pressure. Therefore, from the viewpoint of lowering the temperature and also lowering the oxygen partial pressure, a method has been proposed in which a straight hole is made in the refractory and gas is blown through the hole. However, although this method can be expected to have a certain effect of cooling the refractories, there is a problem in that the effect of suppressing wear of the refractories is not fully satisfactory. In other words, since the contact area with the cooling gas can only be taken up by the length of the refractory, it is necessary to increase the amount of gas used in order to increase the cooling effect for the purpose of suppressing wear and tear. As a result, the latent heat of the gas is low due to dilution with a large amount of gas, and the utility value of the exhaust gas is low.Also, the linear velocity of the injected gas is greater than the flow rate of the exhaust gas in the furnace, so the cooling gas is The problem is that the atmospheric gas is pierced and the oxygen partial pressure reduction effect is reduced more than expected.

(Problems to be Solved by the Invention) As described above, in the conventional method for suppressing wear of carbon-containing refractories, the amount of cooling gas for the refractories must be increased, and as a result,
Since the utility value of the exhaust gas and the effect of reducing oxygen partial pressure were lower than expected levels, the effect was not satisfactory even though there was an effect of suppressing wear on refractories.

In view of the problems inherent in the prior art, the present invention significantly reduces the wear and tear of refractories in metallurgical furnaces that perform oxygen blowing operations without causing any adverse effects, thereby reducing the production cost of hot metal or molten steel more than ever before. The purpose is to lower the

(Means for solving the problem) In a metallurgical furnace that performs oxygen blowing, inside a carbon-containing refractory used as a lining in a 14-part space of a molten material.

A spiral void as shown in Fig. 1(a) is provided, and during oxygen blowing operation, a non-oxidizing gas such as nitrogen gas is supplied through the void at 50 to 30 ON per refractory cross section (unit: M).
Blow at m'/h. At this time, the length of one spiral void should be at least twice the length of the refractory, and the void diameter and void distance (distance between one void and another void) should be determined. ) shall be 0.01 or more.

The arrangement of the carbon-containing refractories is shown in FIG. 1(b).

(Function) When a non-oxidizing gas such as nitrogen is blown into the furnace through the refractory, the refractory is cooled while passing through the large material, resulting in a decrease in the surface temperature of the refractory.

Furthermore, when a non-oxidizing gas enters the furnace, the oxygen partial pressure is lowered, which together reduces wear and tear on the refractory. However, the larger the amount of non-oxidizing gas injected, such as nitrogen, the greater the effect of suppressing refractory wear, but on the other hand, when looking at the process as a whole, the thermal efficiency in the metallurgical furnace decreases, and the exhaust gas Since the gas is diluted with nitrogen, side effects such as a decrease in the calorific value per unit gas amount increase. Therefore, it is industrially important to obtain the desired effect of suppressing wear on refractories by blowing as little gas as possible.

Therefore, we introduced a characteristic value called the refractory wear suppression effect index J to examine the appropriate conditions for gas injection. Here, the [refractory wear suppression effect index] is an index obtained by dividing the refractory wear suppression amount by the amount of non-oxidizing gas such as nitrogen blown into the refractory.

FIG. 2 shows the relationship between the void diameter (D) and the ratio of the void outside M (Dゎ) on this index. (Dp, Db are the first
(See figure (b)). DP/D. It can be seen that the effect of suppressing refractory wear is large when is 0.0.1 or more.

This is because if D, /Db is small, the front surface of the large object will not be uniformly disposed of, and on the other hand, if D p/D is 0.0
This is because if it is set to 1 or more, the entire front surface of the refractory will be uniformly cooled. Furthermore, when compared to the case where a conventional linear gap is provided, it can be seen that the effect of suppressing wear on the refractory is increased by forming the gap in a spiral shape. This is because by spiralizing, the direction of gas discharge changes for each gap,
Because the gas can cover the entire surface of the refractory, the effect of reducing the oxygen partial pressure here becomes greater, suppressing the combustion of carbon in the refractory, and as a result, effectively suppressing wear and tear. be.

Figure 3 shows the influence of the ratio of the length of the spiral gap (Q) to the length of the refractory (L) on the "refractory wear suppression effect index" when D p / D b" 0, 01. show.

It can be seen that when Q/L is 2 or more, the effect of suppressing refractory wear is large. This is because when Q/L is less than 2, the cooling effect inside the refractory becomes small, and by setting 12/L to 2 or more, it is necessary to increase the cooling effect inside the refractory.

Figure 4 shows D p/D b= 0, 01, Q/L=
At 2.5, the nitrogen gas flow rate per refractory cross-sectional area into the furnace through the spiral gap (N rn' / h
/rrF) and the "refractory wear suppression effect index" is shown. It can be seen that when the nitrogen gas flow rate is in the range of 50 to 30 ONm/h/m, the effect of suppressing refractory wear is most efficiently obtained.

The reason for this can be explained as follows. That is,
If the flow rate of the blown gas is too small, the cooling effect of the gas as it passes through the refractory will be weakened, resulting in the temperature near the refractory surface not decreasing as expected, and splashes inside the furnace. The reason why it becomes difficult to suppress the wear of refractories is that the effect of preventing adhesion to the voids is reduced, and as a result, the distribution of the amount of gas blown in becomes unstable. On the other hand, if the injected gas flow rate is too large, the cooling effect on the refractory will be achieved, but the injected gas will penetrate into the interior of the furnace and the proportion of gas rising along the refractory wall will be small. , the effect of reducing the oxygen partial pressure near the refractory due to the blown gas becomes smaller. Therefore, wear and tear on the refractories cannot be suppressed.

(Example) In a converter using alumina-carbon bricks as a refractory, oxygen was blown at the top at 20,000 Nrn'/h and nitrogen was blown at the bottom at +1,00 Nrn'/h.

Hot metal was produced by inputting iron ore and coal. Each brick (cross section is 150m x 150an and depth is 500mm) in the upper part of the converter (more than 1/2 of the upper part in the height direction) has a diameter of 4se at the center, which is 3 times the length of the brick. It has one spiral gap (in this test, a pipe processed into a spiral shape was used as the gap) with a distance of (500m+++X3), and in this case, D
p/D b was 0.026. Then, nitrogen gas was flowed through the bricks at a rate of 100 NrrI''/h per unit cross-sectional area of the refractory. As a result, the average wear rate of the refractory in the upper half of the furnace was 0.8 m/h.

On the other hand, for comparison, we investigated the case without spiral voids and found that the average wear rate of refractories was 4 rrm/h,
The present invention has significantly reduced the rate of wear and tear.

In addition, when conventional linear voids are provided in bricks (four straight pipes with an inner diameter of 4 m are installed in one brick, and nitrogen is added thereto at 100 Nrn per unit cross-sectional area of the refractory, as in the case of the present invention) '/h flow) has an average wear rate of 1.7
m/h, and the present invention was able to reduce it to less than half compared to this case.

In addition, in the method according to the present invention, the amount of nitrogen blown into the entire furnace is 2,50 ONrn'/h, which accounts for about 50% of the total amount of exhaust gas.
It only accounts for %.

As described above, a feature of the present invention is that a large effect can be obtained in suppressing wear of refractories with relatively small amount of gas injection.

(Effects of the invention) By carrying out the present invention, it is possible to significantly reduce the wear and tear of the refractories of metallurgical furnaces that perform oxygen blowing operations that place a large load on the refractories, and as a result, it is possible to It is very effective industrially because it can reduce the manufacturing cost of molten metal or alloy.

[Brief explanation of drawings]

FIG. 1 shows an example of a refractory with spiral voids used in the practice of the present invention. Figure 2 shows the gap diameter (D) and gap distance (D) provided in the refractory.
The relationship between the refractory wear suppression effect index (refractory wear suppression amount/injected gas amount) with respect to the ratio with D5) is shown. Figure 3 shows the length of the spiral gap (R) and the length of the refractory (L).
Figure 4 shows the relationship between the refractory wear suppression effect index and the ratio of
/sin/rrr) and the refractory wear suppression effect index. 1... Working side of the refractory 2... Gas outlet in the void Figure 2 Nitrogen P! F, interval 0 distance, Db Fig. 1 (b) 4th vlJ Chapter Igakuten Amount of power including compensation (A#/su/-2)

Claims (2)

[Claims] (1) In a metallurgical furnace that performs oxygen blowing, a spiral void is provided inside the carbon-containing refractory used as a lining in the upper space of the molten material, and during operation, a non-oxidizing gas is passed through the void into the refractory. 50 to 300 per cross-sectional area (unit: m^2)
A method for suppressing wear of carbon-containing refractories, characterized by blowing at a rate of Nm^3/h. (2) The length of one spiral void is at least twice the length of the refractory, and the ratio of the void diameter to void distance (distance between one void and another void) is 0. The method for suppressing wear of a carbon-containing refractory according to claim 1, characterized in that the voids are provided so that the gap is greater than or equal to .01.