JPH0639612B2 - Tubular structure of converter bottom - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a tuyere structure of a converter furnace bottom, and more particularly to a tuyere structure capable of remarkably extending the life of a furnace bottom refractory, a bottom blowing converter,
It is used in the steelmaking field using a top-bottom blown converter.

[Conventional technology]

After the war, pure oxygen top blowing converters represented by LD converters were the mainstream steelmaking furnaces. However, with the invention of the so-called double-tube tuyere, in which a hydrocarbon-based gas was sheathed in 1965 and contained oxygen gas, a bottom-blown converter was noticed in terms of accelerating in-furnace reaction by vigorous stirring of molten steel. The technology of the combined blowing converter using both the bottom method and the bottom blowing method has been developed, and high productivity has been achieved. However, the technology for extending the life of the bottom refractory remains an important issue.

An outline of the structure and operation of a conventional composite blowing converter having a concentric double tube bottom tuyere will be described with reference to FIGS.

An oxygen injection lance 4 is provided above the central portion of the converter furnace body 2 to inject oxygen into the surface of the hot metal 6A. On the other hand, the furnace bottom 8 is provided with a plurality of double tube tuyeres 10 as shown in FIG.
A flux solid powder 14 such as quicklime is generally blown into the inner tube 12 using oxygen gas as a carrier. On the other hand, in the gap between the inner pipe 12 and the outer pipe 16, hydrocarbon gas, CO ₂ gas, C
A cooling gas 18 such as O 2 gas is blown.

Impurity components such as C, P and S contained in the hot metal 6A charged into the furnace body 2 are oxygen blown into the furnace from the oxygen blowing lance 4 and the inner tube 12 of the furnace bottom tuyeres, Molten steel 6B that has the specified components removed by flux such as quicklime
Is smelted.

On the other hand, hydrocarbon gas, CO ₂ gas, CO gas, etc. 1 which is blown into the furnace through the outer pipe 16 of the double-tube tuyere 10 at the bottom of the furnace
8 has a function of protecting the tuyere 10 and the refractory material 20 around it from ultra-high temperature conditions due to the reaction between the oxygen gas blown into the furnace by the endothermic reaction and the hot metal 6A. .

As described above, the composite blowing converter has a high reaction efficiency due to strong stirring, is capable of producing a predetermined molten steel in a shorter time than the conventional top blowing converter, and is a raw material for the auxiliary raw materials used. It has many excellent characteristics such as few units.

However, although this converter cools the refractory material 20 around the tuyere 10 by the endothermic reaction of the hydrocarbon gas 18 etc. blown into the furnace through the outer pipe 16 of the double tube tuyere 10, the hydrocarbon gas or the like Since there is a place where the refractory decomposes near the surface of the refractory, there is a limit to the cooling of the tuyere 10 and the refractory 20 around it, and damage to the refractory as shown in FIG. There is a problem that the rate of wear of the bottom refractory is significantly higher than that of other parts of the converter.

The manner of damage to the furnace bottom refractory is shown in FIGS.
This will be described with reference to (C), (D) and (E). FIG. 5 (A) shows the tuyere 10 and the refractory 20 in a normal state. FIG. 5 (B) is a tuyere nozzle 1 by heat spalling.
A crack 22 generated in the refractory material 20 near 0 is shown. That is, the periphery of the tuyere nozzle 10 is exposed to molten steel at a high temperature of about 1700 ° C., and after tapping, it is exposed to the outside air and undergoes a heat cycle with a marked temperature difference within a short time. At that time, a large temperature gradient is generated inside the refractory 20, and as a result, thermal stress is generated and a crack 22 is generated. Refractory 20
When cracks occur in the surface, the surface easily peels off, and the refractory brick 20A falls off as shown in (C). Such damage due to heat spalling suddenly occurs, and the peeled brick layer may be large, which not only accelerates the wear of the brick 20A significantly, but also impairs the operation of the converter.

FIG. 5 (D) is a tuyere 1 caused by wear caused by molten steel.
3 schematically shows the wear of the refractory material 20 around 0. That is, in the composite blowing converter, in addition to the oxygen jet ejected from the upper oxygen blowing lance 4 to the surface of the molten steel, quick lime or the like containing oxygen gas blown from the furnace tuyere 10 as a carrier is used. The molten steel 6 in the furnace is strongly stirred by the jetting of the powder 14 of the flux solid, and as a result, the refractory 20 above the tuyere 10 is worn and scraped off by the violent movement of the molten steel 6.

FIG. 5 (E) is a schematic diagram showing a large wear situation of the brick around the upper part of the tuyere 10 caused by insufficient cooling by the cooling gas 18 such as hydrocarbons pumped by the outer pipe 16 of the tuyere bottom 10. . Once such large damage occurs, the tuyere nozzle 10 cannot be reused.

In addition, a backflow phenomenon of the oxygen jet blown into the molten steel 6 occurs on the surface of the tuyere nozzle 10 and the refractory material 20 in the vicinity thereof, which is also said to be a cause of damage to the refractory material 20 in the periphery.

Although various countermeasures have been considered for the wear around the bottom of the bottom of the composite blowing converter having the double tube tuyere,
As a typical example thereof, there is JP-A-55-24948. This is a triple tube system in which a third-layer flow path for injecting an inert gas is formed on the outside of a concentric double tube, unlike a normal double tuyere. About 800
Protects the heat absorption mechanism by thermal decomposition that occurs in two temperature regions above ℃ by blocking the heat transfer from the refractory around the tuyere by flowing an inert gas to the outermost layer, and the heat absorption effect. It was intended to remove the cause of the spalling of the bricks, while at the same time exhibiting a remarkable temperature gradient inconsistency.

However, in the above-mentioned concentric triple tube system, in the portion where the inert gas is jetted from the third layer flow passage and the boundary between the furnace bottom refractory,
Since the required amount of gas is large, the local cooling action is large, and therefore the refractory around the triple tube tuyere has a problem that spalling and falling during refining remain.

[Problems to be solved by the invention]

An object of the present invention is to solve the problems of the prior art such as damage to refractories around a plurality of sets of concentric multi-tubes in the bottom of the composite blowing converter, and to prevent the damage of the refractories in the converter furnace. The bottom is to provide an effective tuyere structure.

[Means for solving problems]

The gist of the present invention is as follows. That is, in the tuyere structure of the converter bottom having a plurality of sets of concentric multi-tubes for transmitting the oxidizing gas, the cooling gas, the powder, etc. through the converter bottom, the outer circumference of the multi-tube A tuyere structure at the bottom of a converter having a plurality of stainless micropore tubes having an inner diameter of 2, 5 mm or less, which are provided in a refractory material so as to surround the multiple tubes and supply a gas for refractory protection. Is.

The tuyere structure of the converter bottom according to the present invention will be described with reference to FIGS. 1 and 2 in the case of a concentric double tube.

A refractory material 20 in the furnace is lined inside the iron shell 24 at the bottom of the converter. This furnace bottom has a plurality of concentric double tube tuyere 10
Is provided. The tuyere 10 is provided with an inner tube 12 and an outer tube 16 having concentric double tubes penetrating the steel skin 24 and the refractory material 20 and opening in the furnace. A flux solid powder 14 such as quicklime is blown into the inner tube 12 with oxygen as a carrier, and an outer tube 16
The cooling gas 1 such as hydrocarbon gas is provided in the flow path between the inner pipe 12 and the inner pipe 12.
Injecting 8 is similar to the conventional tuyere. The tuyere 10A according to the present invention is provided with a plurality of metal pore tubes 26 surrounding the outer tube 16, and the inner tube 12 and the outer tube 1 are provided.
In parallel with No. 6, a hole is formed in the furnace bottom. Iron skin 24
A common tank 28 for the metal micropore pipe 26 is provided outside of the above, and the inert gas 30 blown into the furnace through the metal micropore pipe 26 is temporarily stored therein. The heat-resistant steel such as stainless steel is desirable for the metal pore tube 26, and the inert gas to be blown may be N ₂ , Ar, or the like, or CO ₂ , CO, or the like.

Since the purpose of installing the stainless steel pore tube 26 is to cool the refractory material 20 around the tuyere 10A, the arrangement thereof is concentrically arranged around the tuyere 10A as shown in FIG.
The area with many damages can be protected over a wide range by enlarging it into two rows and three rows according to the degree of damage of the 0A peripheral brick.

The outline of the configuration of the present invention has been described above, and further detailed description will be given below together with the experimental results of the present inventor by Examples.

〔Example〕

In a 250t composite blowing converter, a tuyere structure as shown in Figs. 1 and 2 was installed on the bottom of the furnace.

Surrounding the furnace bottom tuyeres 10A composed of the inner tube 12 and the outer tube 16, 60 stainless steel micropore tubes 26 having an inner diameter of 2 mm and an outer diameter of 4 mm were provided for each of the furnace bottom tuyeres 10A. The distance between the pipes of the stainless steel fine tube 26 was set to 10 to 30 mm, and they were arranged concentrically in two rows as shown in FIG. 2 from the outer surface of the furnace bottom tuyeres 10A to a position of 150 mm. 60 pore tubes 26
To the furnace bottom tuyeres 10A, that is, a pressure of ^{2 to} 8 kgG / cm ² is applied to each of the 261 sets of 60 fine pore tubes, and
An inert gas Ar of 2 to 1.5 Nm ³ / min was passed. Inert gas other Ar, can be used _{N 2,} other _CO 2, CO gas. Furnace bottom brick 20 around tuyere 10A
A magnesia-graphite brick was used as A, but the temperature around the pore tube 26 was measured at a depth of 100 mm from the tip of the operating surface of the pore tube 26 with molten steel 6B in the furnace. Showed a low temperature of 600 to 800 ° C. This is the effect of cooling by removing the heat of the inert gas passing through the pore tube 26. Next, the result of the test for determining the range of the inner diameter of the pore tube 26 used in the present invention will be described.
First, a stainless steel pipe having an inner diameter of 2 mm was used, and the change with time in the relationship between the gas flow rate and the back pressure was measured. The results are shown in Fig. 6. That is, the gas flow rate starts from 2 Nm ³ / min, gradually reduces the gas flow rate to almost 0, holds it for 4 minutes, and then when the gas pressure is increased to 4.6 kgG / cm ² , the gas flow rate is increased again. Came out.

Next, as a result of investigating the relationship between the inner diameter of the pipe and the open area ratio using the fine pore tubes 26 having the inner diameters of 2 mm and 4 mm, the results are shown in FIG. Here, the opening efficiency is the ratio of the number of times that the state in which the gas is discharged from the operating surface of the pore tube 26 by overcoming the coating layer of molten slag is visually confirmed. As is clear from FIG. 7, if the inner diameter of the pore tube 26 is 2.5 mm or less, the opening efficiency is as high as 80% or more, and the gas can be re-supplied even after it has been temporarily stopped, and the gas flow rate can be set in a wide range It has been found to be controllable over. Therefore, the inner diameter of the pore tube 26 used in the present invention is limited to 2.5 mm or less. If the gas flow from the pore tube 26 is unnecessary, the inner diameter of the pipe is small even if the gas flow is stopped, so that the outlet is closed by melting itself, so that the molten steel 6B is used as the pore tube 2.
There is no risk of leakage from No. 6, and even if the gas is temporarily stopped, it can be resupplied by overcoming the coating layer of the slag if it is still blowing. Since the pore tube 26 according to the present invention has the above-described effects, it has a great effect that the gas flow rate can be adjusted according to the conditions necessary for the molten steel to be refined, for example, the nitrogen concentration in the steel.

After the experiment by the present inventor, after adjusting the damage state of the furnace bottom tuyeres 10A and the refractory bricks 20 around the tuyeres 10A, as a result, the furnace bottom tuyeres 10 as shown in FIGS. No melt damage or cracks of the refractory brick 20 due to thermal spalling as shown in FIGS. 5 (B) and 5 (C) were observed at all, and the conditions inside the furnace were extremely good.

〔The invention's effect〕

The present invention is a bottom-end tuyere structure of a composite blowing converter having a plurality of sets of concentric multi-tubes. With a tuyere structure provided with a metal pore tube, the metal pore tube was preferably a stainless steel tube, and the following effects could be obtained by setting the inner diameter to 2.5 mm or less.

(B) Cooling and protecting the refractory around the tuyere by supplying an inert gas into the stainless micropore tube,
By preventing the generation of thermal stress around the tuyere, damage due to thermal spalling could be reduced.

(B) Since the inner diameter of the stainless steel pore tube is 2.5 mm or less, even if the injection of the inert gas is stopped when it is unnecessary,
There is no risk of molten steel leaking because it blocks the open hole in the furnace due to its own melting, and it is possible to re-supply gas by raising the supply gas pressure during converter blowing, and an inert gas for cooling. It is possible to control the flow rate in a wide range.

(C) Due to the effect of (b), it becomes possible to adjust the supply gas amount according to the conditions required for molten steel to be refined in a converter, such as the nitrogen concentration in steel.

(D) The wear of the multiple pipe tuyeres has been reduced, and the actual result is about 10%.
It has become possible to reduce the wear rate of.

[Brief description of drawings]

1 and 2 show the tuyere structure of the bottom of the converter according to the present invention. FIG. 1 is a schematic vertical sectional view, FIG. 2 is a lateral sectional view, and FIG. 3 is a structure of a composite blowing converter. FIG. 4 is a schematic cross-sectional view showing a conventional bottom bottom tuyere structure of a composite blowing converter,
5 (A), (B), (C), (D), and (E) are schematic cross-sectional views showing damage to the conventional furnace bottom tuyeres and surrounding refractories, and (A) is a normal state. , (B) the state of crack generation due to thermal stress, (C) the state of brick falling out of the crack,
(D) shows the worn state of the tuyere nozzle, (E) shows the large worn state of the tuyere nozzle, and FIG. 6 shows the flow rate of the inert gas for cooling through the stainless porous tube in the embodiment of the present invention. FIG. 7 is a diagram showing the change of back pressure with time, and FIG. 7 is a diagram showing the influence of the inner diameter of the stainless porous tube according to the present invention on the open area ratio. 6A ... hot metal, 6B ... molten steel 8 ... converter furnace bottom 10,10A ... double tube tuyere 12 ... inner tube, 16 ... outer tube 18 ... cooling gas, 20 ... furnace bottom Refractory 24 …… Converter iron shell, 26 …… Metal pore tube 28 …… Inert gas tank, 30 …… Inert gas

Claims (1)

[Claims] 1. A tuyere structure for a converter bottom comprising a plurality of sets of concentric multi-tubes for pressure-feeding an oxidizing gas, a cooling gas, powder, etc. through the converter bottom. A plurality of stainless micropore tubes having an inner diameter of 2, 5 mm or less, which are provided to surround the multiple tubes in the outer peripheral refractory of the tube and supply a gas for refractory protection, Tuyere structure.