JPH10273714A - Bottom blowing tuyere - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the large temp. variation between during blowing and during non-blowing of a tuyere brick and to make suitable the tuyere cooling by arranging a heat insulating tube flowing inert gas at further outside of the outer tube for blowing gas for protectioncooling the tuyere. SOLUTION: The heat insulating tube 22 at further outside of the tuyere outer tube 18 to prevent excess cooling of the tuyere outer tube 18 and the tuyere brick 20 with propane gas as cooling gas. A gap 24 between the tuyere outer tube 18 and the heat insulating tube 22 is held to constant and the heat insulation of the outer tube 18 of the double-tube tuyere and the tuyere brick 20 surrounding this tuyere can be obtd. by setting this gas and the temp. variation of the tuyere brick 20 is restrained and the wearing speed of the tuyere outer tube 18 is reduced. The lowest flow rate of gas is blown into the gap 24 to prevent the clogging by invading the molten iron or the molten steel 26. This gas is desirable to use inert gas, i.e., argon and gaseous nitrogen. Further, as the material of the heat insulating tube 22, the stainless steel, etc., having large high strength is desirable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tuyere
In particular, the present invention relates to a multi-layer bottom blowing tuyere used in a pure oxygen bottom-blowing converter or a pure oxygen top-bottom blowing converter.

[0002]

2. Description of the Related Art Conventionally, in a bottom blowing tuyere of a pure oxygen bottom blowing converter or a pure oxygen top bottom blowing converter, a bottom blowing tuyere having a double pipe structure as shown in FIG. 3 is used. In the permanent brick 3 and the hearth brick 4 lined with the steel shell 2, a tuyere having a double pipe structure of an inner pipe 6 and an outer pipe 8 is fixedly provided on a tuyere mounting flange 12, and is provided from the inner pipe 6. Blows pure oxygen, nitrogen, argon and carbon dioxide gas as refining gases, and blows propane, nitrogen, argon, carbon dioxide gas, etc. from the gap 10 between the outer tube 8 and the inner tube 6 as a tuyere protective cooling gas. To prevent damage to the furnace tuyere. In the tuyere having the double tube structure as described above, it is important that solidified iron, so-called mushroom, generated at the tip of the tuyere by the protective cooling gas is stably generated and present. However, during operation, the temperature fluctuates greatly due to heating and cooling, and the difference in the heat content (specific heat), thermal conductivity, and linear expansion coefficient of the refractory and the mushroom in the hearth indicates that the mushroom has the effect of protecting the tuyere. Conventionally, there are cases where it cannot be mentioned sufficiently.

[0003] Although the metallurgical advantages and advantages of the above-described converter having a bottom blowing function are well known, the bottom blowing tuyere affects the stable operation and furnace life. This is one of the biggest issues for bottom blown converters. To solve this problem, various countermeasures and technical developments as described below have been conventionally performed. Development of tuyere brick with excellent spalling resistance Development of slag coating technology Improvement of operation method (Q, D, T method; Quick Dir)
(Elect Tapping) Optimization of tuyere cooling (A) Proper control of cooling gas flow rate such as propane (B) Mixing diluted cooling gas such as Ar, N ₂ , CO ₂ into oxygen gas

[0004] All of the above-mentioned prior arts have shown great effects on the improvement of the tuyere life and the suppression of the abrasion, and they have achieved some success. However, from the viewpoint of tuyere wear phenomenon, problems still remain in the following points. That is, a satisfactory technology has not been developed in the following technology as a means for suppressing a large temperature change between during and after blowing of tuyere brick and optimizing tuyere cooling. The flow rate of tuyere cooling gas such as propane is reduced to prevent the tuyere outer tube temperature during blowing and the supercooling of tuyere bricks. The dilution gas (Ar, N ₂ ,
CO _2, etc.) are mixed, to prevent blade extraoral tube temperature during blowing, the supercooling of the tuyere brick. In addition, the diluent gas (Ar, N ₂ , CO ₂ ) is mixed with the pure oxygen gas blown from the tuyere inner tube to reduce the required cooling amount by the cooling gas.

The above method and means can prevent the tuyere outer tube from overcooling and suppress the temperature change of the tuyere brick. However, even the mushroom formed at the tip of the tuyere is reduced. Even though crack generation and brick loss of the brick can be suppressed, wear from the tuyere tip cannot be suppressed because the protective layer on the surface in contact with the molten steel becomes small. In addition, the method of (1) reduces the amount of heat applied to the mushroom and is effective for maintaining and protecting the mushroom.However, mixing the diluting gas with the inner pipe gas, which accounts for most of the bottom blown gas, results in an increase in the cost of the smelting gas. Becomes

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to suppress the problems of the prior art of the above-mentioned tuyere-blow tuyeres, in particular, to suppress a large temperature change during the tuyere brick blowing and non-blowing. It is an object of the present invention to provide a bottom-blow tuyere structure that optimizes tuyere cooling and thereby effectively protects mushrooms.

[0007]

SUMMARY OF THE INVENTION The inventor of the present invention has found that the tuyere bricks, especially the tuyere outer tube, are subjected to excessive temperature change due to supercooling during blowing and temperature rise during non-blowing. In the event that cracks occur in the inside and bricks are lost, but when the tuyere cooling gas flow rate is reduced, the protective layer of the mushroom in contact with the molten steel becomes smaller, and the wear from the tuyere tip is extremely large. Focusing on providing an outermost tube outside the outer tube and providing an insulated tube through which the inert gas flows, as a result of repeated tests, the present invention was completed, and the gist thereof is as follows. It is. (1) Pure oxygen bottom blow or pure oxygen top bottom blow converter having a double pipe structure of an inner pipe for blowing refining gas and an outer pipe for blowing tuyere protection cooling gas A bottom-blow tuyere, wherein a heat-insulating tube through which an inert gas flows is provided further outside the outer tube at the tuyere. (2) It has a temperature sensor buried in the refractory around the tuyere consisting of the inner pipe, the outer pipe and the heat insulating pipe, or provided in contact with the outer surface of the heat insulating pipe. The tuyere according to (1), wherein the flow rate of the inert gas is controlled based on temperature information. (3) The bottom-blowing tuyere according to the above (1) or (2), wherein the heat-insulating pipe is made of stainless steel or heat-resistant steel having high high-temperature strength. (4) The gap between the outer surface of the outer tube and the inner surface of the heat insulating tube is substantially 1
(1), (2),
The bottom-blow tuyere according to any one of (3).

[0008]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing the configuration of the bottom blowing tuyere of the present invention. The configuration of the bottom blow tuyere of the present invention shown in FIG. 1 is provided on the outer side of the outer tube of the bottom blow tuyere of the prior art double tube described above with reference to FIG. A tube is provided. That is, the permanent brick 14 and the hearth brick 15 lined to the converter steel shell 13 include:
A tuyere having a double structure of a tuyere inner tube 16 and a tuyere outer tube 18 is provided, and a tuyere brick 20 is provided outside the tuyere.
Conventionally, pure oxygen is blown from the tuyere inner tube 16 as a refining gas, and propane is mainly blown from the gap 19 between the tuyere outer tube 18 and the tuyere inner tube 16 as a tuyere protection cooling gas. Are identical.

The present invention relates to a tuyere outer tube 18 and a tuyere brick 2.
A major feature is that a heat insulating tube 22 is provided further outside the tuyere outer tube in order to prevent 0 from being supercooled by a cooling gas or propane. By keeping the gap 24 between the tuyere outer tube 18 and the heat insulating tube 22 constant and installing it, the outer tube 18 of the double tube tuyere and the surrounding tuyere brick 20 can be insulated. , Suppress the temperature change of tuyere brick 20,
It has the function of reducing the rate of wear of the tuyere outer tube 18.
A gas of a minimum flow rate is blown into a gap 24 formed between the inner surface of the heat insulating tube 22 and the outer surface of the tuyere outer tube 18 to prevent the hot metal or the molten steel 26 from entering and closing. This gas is thermally decomposed like a tuyere cooling gas, has no endothermic cooling effect, and reacts with hot metal or molten steel 26 to generate no inert gas, such as argon gas (Ar) or nitrogen gas (N). ₂ ) is desirable. In the present invention, this gas is referred to as a heat insulating pipe protection gas.

The heat insulating pipe 22 is provided with a temperature sensor 28 at an appropriate position in the longitudinal direction, and controls the flow rate of the heat insulating pipe protection gas 30 based on temperature information obtained from the temperature sensor 28. Specifically, the flow rate of the heat insulating pipe protection gas 30 is increased or decreased so that the temperature change of the tuyere brick 20 is reduced. The installation position of the temperature sensor 28 does not necessarily have to be a position in the longitudinal direction of the heat insulating tube 22. That is, the tuyere brick may be provided so as to be buried in an appropriate position in the inside of the tuyere. Further, as a material of the heat insulating tube 22, it is desirable to use a material having a high melting temperature and high strength at high temperature, specifically, stainless steel or heat-resistant steel.

[0011]

EXAMPLE The present invention was applied to a 250-ton top-bottom blow converter called K-BOP, and the wear rate of the bottom-blowing tuyere was investigated.
That, Ar 1, bottom blowing tuyeres as a diluent gas to the oxygen gas from the tuyere pipe 16 by a double tube tuyere, N ₂
And a small amount of diluent gas Ar, N ₂ is blown into propane as cooling gas from the gap 19 between the tuyere outer tube 18 and the inner tube 16, and the heat insulating tube 22 of the present invention is incorporated outside the outer tube 18. Blew up. Gap 24 between heat insulating tube 22 and outer tube 18
Is approximately 1 mm, and several splines of projections continuous in the longitudinal direction of the tube are provided on the outer surface of the outer tube 18 in order to keep the gap uniform. Gas flowing into the gap 24, i.e., the heat insulating tube protective gas 30, and Ar or N _2, and appropriately selected by grades. The flow rate of the protective gas for the adiabatic pipe is set to a minimum flow rate of 1 Nm ₃ / min (per one tuyere) during the blowing, and is set in the gap 24 so that the value of the temperature sensor 28 provided in the adiabatic pipe 22 becomes an appropriate temperature. The flowing inert gas flow was controlled.

If there is no possibility that the gap 24 will be closed by the intrusion of the molten steel 16 during non-blowing, the flow rate of the protective gas 30 is set to zero, otherwise 0.1 N per tuyere is used.
The operation was performed at a reduced m ₃ / min. The results of the test operation were compared with those of the conventional method, and the present invention was carried out in the case where the amount of temperature change (maximum value) during blowing and non-blowing of tuyere brick and the tuyere wear rate in the conventional method were set to 1. Table 1 shows example values
It was shown to. The blowing operation conditions were almost the same in both the conventional method and this embodiment. The mushrooms at the tuyere tip also showed little difference between the two by visual observation.

[0013]

[Table 1]

[0014]

According to the present invention, 1 m is provided outside the conventional double tube tuyere.
An insulated pipe is provided with a gap of about m, an inert gas flows through the gap 24, and a temperature sensor 28 is provided in the longitudinal direction of the insulated pipe 22 so that the flow rate of the inert gas is adjusted so that the temperature sensor has an appropriate temperature value. , The following effects could be obtained. (A) The maximum temperature change during the blowing and non-blowing of the tuyere brick 20 is reduced from 500 ° C. in the related art to about 50 ° C. without reducing the mushroom 31 generated at the tuyere tip.
10, and the tuyere attrition index can be reduced from 1 of the conventional method to 0.32, and the extension of the tuyere life can be realized at low cost. (B) As a result of (a), the furnace life of the bottom-blowing and top-bottom-blowing converters can be improved, and it has greatly contributed to improvement in productivity and cost reduction.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of a bottom blowing tuyere according to the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a conventional tuyere.

[Explanation of symbols]

 2,13 converter iron shell 4,15 hearth brick 6 inner tube 8 outer tube 10 gap 14 permanent brick 16 tuyere inner tube 18 tuyere outer tube 19 gap 20 tuyere brick 22 heat insulating tube 24 gap 26 molten steel 28 temperature sensor 30 heat insulation Pipe protection gas 31 mushroom

Claims (4)

[Claims] 1. A pure oxygen bottom-blowing or pure oxygen top-blowing converter having a double-pipe structure of an inner pipe for blowing refining gas and an outer pipe for blowing tuyere protective cooling gas. A bottom-blow tuyere, wherein a heat-insulating tube through which an inert gas flows is provided further outside the outer tube. 2. A temperature sensor buried in a refractory around a tuyere comprising the inner pipe, the outer pipe, and the heat insulating pipe, or provided in contact with an outer surface of the heat insulating pipe, The tuyere according to claim 1, wherein a flow rate of the inert gas is controlled based on temperature information obtained by a sensor. 3. The heat insulating tube according to claim 1, wherein the heat insulating tube is made of stainless steel or heat resistant steel having high strength at high temperature.
Or the bottom tuyere described in 2. 4. A gap between an outer surface of the outer tube and an inner surface of the heat insulating tube is approximately 1 mm.
The tuyere according to any one of the above items.