JPH0288711A - Method for protecting tuyere in converter - Google Patents

Abstract

PURPOSE:To form stable mushroom in molten steel just above tuyere and to prevent erosion of a tuyere brick by using hydrocarbon series gas, etc., as stirring gas in a combined blowing method in a converter, in which the stirring gas is brown from the bottom part. CONSTITUTION:The combined blowing is executed by top-blowing oxygen from upper part of the molten metal 4 charged into the converter 2 by using a lance 6 and blowing the stirring gas 10 from the tuyere 8 in the furnace bottom 2A. At this time, the hydrocarbon series gas or mixed gas of the hydrocarbon series gas and inert gas is used as the above stirring gas 10. The inert gas in this mixed gas is contained at 0-99vol.%. Further, the above gas blowing is executed at the latter half period of blowing in the converter.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for protecting converter tuyeres, and in particular, when blowing stirring gas from the bottom of the furnace, it is necessary to This invention relates to a method of protecting converter siding using a mixed gas of inert gas, and is widely used in the steel manufacturing field.

[Conventional technology]

The combined blowing method of a converter is also called the top-bottom blowing method, and as shown in FIG.
A stirring gas 1 such as N2 or Ar is supplied from the tuyere 8 through the tuyere 8.
0 is blown into the molten metal 4 to stir the molten metal 4 and promote the reduction of FeO remaining in the slag 12 floating on the molten metal 4.
This is a refining method that aims to improve yield, increase blown up Mn, and dephosphorize.

In the above composite blowing method, the most important thing is the life of the tuyere. The direct cause of the erosion of the bottom 2A of a top-bottom blowing converter using an inert gas as the stirring gas is that the tip 1 of the tuyere 8 is caused by the intense flow of the molten metal bath occurring near the tip of the tuyere 8.
6 is carved into a mortar shape as shown in FIG. 2 (A), or recessed into a forest shape as shown in FIG. 2 (B). This is caused by the water rising up and floating into the bath during smelting. The erosion of the tip of the tuyere 8 due to abrasion reaches approximately 0.3 to 1.0+nm/charge and causes problems in operation, so how to protect the tuyere is the most important issue in the composite blowing #I method. It is considered to be one of the

The tuyere structures of converters made using the combined blowing method include porous brick type, single tube type, and tube cluster type (MHP).
Furthermore, there is a method of circulating cooling gas through the outer tube as a concentric double tube or a concentric triple tube, and many methods have been proposed to extend the life of the tuyere 8.

For example, ``Method of blowing gas for bottom blowing'' in Japanese Patent Application Laid-Open No. 58-130212 is as follows. That is, (1) when performing blowing using a bottom-blowing converter or a top- and bottom-blowing converter having bottom-blowing tuyeres under the four sides of the steel bath, the bottom-blowing oxygen is used as part of the blowing process. In a bottom blowing gas blowing method of bottom blowing an inert gas or carbon dioxide gas or only an inert gas, blowing a mixed gas of oxygen and an inert gas or carbon dioxide gas or only an inert gas as the bottom blowing gas. During the blowing process and during the period when the tuyere is immersed in molten steel, only industrially pure oxygen is not blown again, and the mixing ratio of inert gas or carbon dioxide gas to oxygen is kept as above. A method for blowing gas for bottom blowing, characterized by blowing a mixed gas smaller than that of the mixed gas.

(2) In the above method, a mixed gas in which the mixing ratio of inert gas or carbon dioxide to oxygen is smaller than that of the mixed gas is blown, and when the mixed gas is blown into the inner pipe, the hydrocarbons in the outer pipe are The system coolant flow rate is reduced and the hydrocarbon coolant flow rate is appropriately controlled to a predetermined amount while injecting inert gas or carbon dioxide at a flow rate substantially equal to the reduced flow rate of the hydrocarbon coolant. This is a method of blowing gas for bottom blowing, characterized by blowing the gas mixed with the hydrocarbon coolant.

However, although this method uses a hydrocarbon coolant in the outer tube, oxygen or Co
This method uses an oxidizing gas such as 2 gas mixed with an inert gas, which is extremely unsatisfactory as a measure to prevent erosion of the tuyere.

In addition, JP-A No. 59-145718 states that ``The stirring gas injected after the middle stage of blowing is a gas containing 40 to 100% by volume of non-oxidizing and/or reducing gas, and further injected after the middle stage of blowing. The amount of stirring gas blown is 1 of the amount of gas blown in the first stage of blowing.
~3 times. ” method.

This method uses a non-oxidizing and/or reducing gas as a stirring gas, and after the middle stage of blowing, the amount of gas blown into the gas is 1 to 3 times that of the previous stage.
Although this method is one step ahead of No. 12, the tuyere life is at least equivalent to the life of one converter, and it is still far from a satisfactory solution.

Next, the method disclosed in Japanese Patent Application Laid-open No. 61-34114 is as follows: ``With respect to a concentric double tube tuyere consisting of an inner tube and an outer tube immersed in a molten metal bath, a cooling gas is caused to flow through an annular flow path inside the outer tube. A method for cooling a tuyere immersed in a bath, characterized in that the flow rate of the cooling gas to be passed through is adjusted according to fluctuations in the temperature of the outer tube.

However, this method reduces the tuyere wear rate by about 1 according to the examples.
Although it claims to have been able to extend the period by 0%, 1.
5 to 1.85 mm/charge, which is still not considered to be a satisfactory method.

Furthermore, the method disclosed in Japanese Patent Application Laid-Open No. 62-109918 is
[Injecting either oxygen gas alone, or a mixed gas of oxygen gas and inert gas, or oxygen gas and CO2 gas into the inner tube of the multi-tube panel for gas injection installed below the bath surface of the molten metal smelting furnace. , and in a cooling method for a multi-tube tuyere consisting of blowing a mixed gas of CO2 gas and propane gas into the outermost tube, the propane gas flow rate flowing into the outermost tube is 1750 to 1/7 in molar ratio of the Co2 gas flow rate. A method for cooling multi-tube tuyeres in a bottom-blown smelting furnace, which is characterized by:

This invention uses a limited amount of propane, which has an excellent cooling function, mixed with CO2 gas in the outermost tube of a multi-tube, and uses N2 generated by thermal decomposition of propane, C3HIl=3C+4H2.
In order to avoid pick-up of CO2 gas into the steel, one method is to inject either oxygen gas alone, oxygen gas and an inert gas, or a mixed gas of oxygen gas and CO2 gas into the inner tube of the multilayer tube as a stirring gas. However, if only the protection of the tuyere is considered, the use of the above-mentioned oxidizing gas is not preferable.

[Problem that the invention seeks to solve]

Although the above-mentioned conventional techniques for protecting the converter tuyere have achieved some degree of effectiveness, in view of the situation where a satisfactory method has not yet been found, an object of the present invention is to eliminate the drawbacks of the above-mentioned conventional techniques, and to provide a relatively simple method for protecting converter tuyeres. The purpose of this invention is to provide an effective protection method that prevents melting and damage of the siding at low cost.

[Means and operations for solving the problems] The gist of the present invention is as follows.

That is, in the combined blowing method of a converter, in which oxygen is blown upward from the top of the molten metal housed in the converter using a lance, and stirring gas is blown from the bottom, a hydrocarbon-based gas or a hydrocarbon is used as the stirring gas. This is a converter tuyere protection method characterized by using a mixed gas of a system gas and an inert gas.

However, the mixing ratio of the inert gas to the hydrocarbon gas is 0 to 99% by volume, and the timing of blowing the hydrocarbon gas or the mixed gas of the hydrocarbon gas and the inert gas is This will be the second half of converter blowing.

As described above, the present invention specifically injects a hydrocarbon gas or a mixed gas of this and an inert gas as a bottom blowing gas in the latter half of refining in a converter. Although there is conventional technology that uses hydrocarbon gas for cooling purposes in the outermost tube of multiple tubes in a converter, there is no example of this being blown alone or mixed with an inert gas as a stirring gas. ,
It has been found that this method is extremely effective as a means of protecting tuyeres.

The results of experiments conducted by the present inventors in order to obtain the present invention will be explained.

The present inventors conducted bottom blowing using N2 gas as an inert gas and propane as a hydrocarbon gas, varying the mixing ratio as shown in Table 1, and investigated the morphology of the produced pine mushrooms and the dissolution of the tuyeres. We investigated the loss situation.

Table 1 The above method of blowing the stirring gas is shown in the test No. 3 shown in Figure 3.
, the same applies to case 2. That is, stirring gas is not injected from the bottom of the furnace for 5 minutes after the start of top blowing, and after 5 minutes, inert gas N2 is injected at 1ONrn'/min, and at the end of blowing, propane is injected at a volume ratio of 100 % to 50%, 10%,
Tests were conducted by changing the mixing ratio to 1%, and for comparison, changing the mixing ratio and type of stirring gas to 100% N2 and 99% N2021% for No. 4.5, respectively.

In this case, the stirring gas such as propane was supplied through a bypass in the middle of the inert gas supply line such as N2, Ar, etc., as shown in FIG. Of course, these hydrocarbon gases are kept warm by steam or the like in order to maintain their gaseous state.

The above test results are as follows. That is, test No.
The form of the pine mushroom formed directly above the tuyere and the state of erosion of the tuyeres in cases 1 to 6 are shown in Figure 4 (A).
, (B), (C), (D), (E), and (F). The above-mentioned so-called "pine mushroom" is a pine mushroom-like solidified substance that is formed right above the siding when propane (C3HI) is blown into the siding. ，
→ It thermally decomposes as 3G + 4H2, but during the thermal decomposition, the lower hydrocarbons undergo an endothermic reaction and remove heat from the surrounding molten steel, forming a pine mushroom-shaped low-temperature zone of about 1000℃ directly above the siding.

As is clear from the shapes of the pine mushrooms according to the examples of the present invention shown in FIGS.
In the case of 100% propane as shown in Figure (A), the radius of the umbrella of the pine mushroom 20 reached as much as 500 mm, and no abrasion was observed in the refractory material 18 around the tuyere 8. In addition, test Nos. 2 and 10 in which 50% propane by volume was mixed with N2 used as an inert gas.
In test No. 013, in which 1% propane was mixed, although the shape of the pine mushroom 20 was slightly smaller, the protective effect of the refractory 18 was excellent;
In Test N004 in which propane was mixed, it was confirmed that pine mushrooms 20 were formed and the tuyeres 8 were protected. Therefore, in the present invention, as a method for protecting the tuyere 8, the hydrocarbon gas must be 100% or the mixture ratio of the inert gas to the hydrocarbon gas must be 1% or more by volume. When the gas mixing ratio is 0 to 99% by volume, pine mushroom 20 is placed directly above the tuyere.
It has been found that the tuyere can be protected by cooling.

In addition, in the case of only inert gas in Test No. 005 conducted as a comparative example, as shown in FIG. It was recognized that Furthermore, in test N006 in which 1% by volume of 02 was mixed as a heat source in N2 gas, the refractory material 18 directly above the tuyere 8 suffered abrasion and melted into a conical shape, as shown in Figure 4 (F). It was recognized that Therefore, it was found that 0□ should not be mixed in, even if it is 1%, in order to protect the feathers.

The flow rate of the bottom-blown stirring gas in each of the above tests was approximately 3.3N rn'/min per tuyere, and the total was:
<10 N rrf'/min as shown in FIG. Incidentally, FIG. 3 shows the case of test No. 2.

Next, as the bottom-blown stirring gas according to the present invention, the timing of blowing a hydrocarbon gas or a mixed gas of a hydrocarbon gas and an inert gas is limited to the latter half of blowing of the converter. The reason for this is that in the latter half of blowing, the C concentration in the molten steel decreases, and the melting point of the pine mushroom produced by the present invention increases, making it difficult to dissolve in the surrounding molten steel flow, and the pine mushroom produced by the present invention becomes difficult to dissolve in the surrounding molten steel flow. This is because the shape of the pine mushroom can be maintained, the low-temperature pine mushroom 20 can press the refractory bricks 18 near the tuyeres 8, and prevent them from floating up. As a result, abrasion of the refractory bricks 18 as shown in FIGS. 4(E) and 4(F) does not occur.

〔Example〕

Similarly to the comparative test according to the present invention, 5 minutes after the start of top blowing, 10 N rn'/min of N2 gas was blown in as a bottom blow stirring gas, and 5 minutes before the end of blowing at the end of blowing, Replace 172 of the flow rate of N2 gas with propane, and set the flow rates of both N2 gas and propane to 5Nrn'/min.
And so. The produced pine mushroom 20 had an umbrella radius of about 3ooIIW11, as shown in FIG. 4(B), and maintained its shape until it stopped. After tapping, the vicinity of the tuyere 8 was observed, and no abnormality was observed in the refractory bricks 18 around the tuyere.

〔Effect of the invention〕

In view of the conventional drawback that the refractory bricks near the tuyere are severely eroded during combined blowing of a converter, the present invention proposes a method using a hydrocarbon gas or a mixture of a hydrocarbon gas and an inert gas as a bottom blowing stirring gas. In addition, the mixing ratio of inert gas to hydrocarbon gas was 0 to 99% by volume, and the timing of injection of hydrocarbon gas or mixed gas was limited to the second half of blowing. We were able to achieve the following effects.

(a) Since a stable pine mushroom can always be formed in the molten steel directly above the tuyeres, the degree of erosion of the tuyere bricks due to ablation is extremely small. For example, according to experiments conducted by the present inventors, as shown in Figure 5, the wear of tuyere bricks when using only inert gas without propane is 0.4.
mn/charge, but when using a mixed gas of 7% propane and 93% inert gas, it was only 0.08 mm/charge.

(b) By (a), we were able to achieve significant productivity improvements and cost reductions by not only reducing the basic unit of tuyere bricks, but also by reducing the number of man-hours required to repair fireproofing materials.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view showing the combined blowing method of a converter according to the present invention, and Figures 2 (A) and (B) are partial cross-sectional views showing the state of wear and tear on the refractory bricks in the furnace directly above the tuyeres according to the conventional method. , FIG. 3 is a diagram showing the relationship between blowing time and bottom blowing gas flow rate in an embodiment of the combined blowing method for protecting the tuyere according to the present invention, and FIGS. 4 (A), (B), ( C), (D), (E), (F)
are cross-sectional views showing the shapes of pine mushrooms in the invention examples (A), (B), (C), and (D), and the comparative example (E).
, (F) is a sectional view showing the state of wear and tear on the tuyere bricks, (A) Table 1 Test No. 1 (B) Case 1
Table Test No. 12 (C) Table 1 Test No. 08
Case 3 (D) Table 1 Case No. 4 (E)
Table 1 Case of Test No. 005 (F) Table 1 Case of Test No. 6 FIG. 5 is a diagram comparing the wear status of the tuyere bricks in the present invention example and the comparative example.

Claims (3)

[Claims] (1) In the combined blowing method of a converter, in which oxygen is blown upward from the top of the molten metal housed in the converter using a lance, and stirring gas is blown from the bottom, the stirring gas is a hydrocarbon gas or a carbonized metal. A method for protecting a converter tuyere characterized by using a mixed gas of hydrogen-based gas and inert gas. (2) The method for protecting a converter tuyere according to claim (1), wherein the mixing ratio of the inert gas to the hydrocarbon gas is 0 to 99% by volume. (3) The method for protecting a converter tuyere according to claim (1), wherein the timing of blowing the hydrocarbon gas or the mixed gas of a hydrocarbon gas and an inert gas is in the latter half of blowing of the converter. .