JPH0517811A - Multiple pipe tuyere cooling method for metallurgical reaction furnace - Google Patents

Abstract

PURPOSE:To prolong the service life of a multiple pipe tuyere without contaminating a molten metal by using gases prepd. by mixing gaseous hydrocarbon and steam at a specific ratio as tuyere cooling gases at the time of blowing a refining gas and the tuyere cooling gases with the tuyere to the molten metal. CONSTITUTION:The tuyere is made into a multiple pipe structure 23 and the refining gas is blown from the inside pipe 26 thereof into the molten metal 28 to execute refining, such as, decarburization by, for example, oxidation, at the time of refining the metal by blowing the refining reactive gas, such as O2, to the molten metal from the tuyere 23 provided under the bath surface of the molten metal. The gaseous mixture which is formed by mixing the gaseous hydrocarbon and the steam to the mixing volumetric ratio of the steam ranging from -50% up to +50% of the reference value, which is obtd. by determining 1:2m mixing volumetric ratio of the gaseous hydrocarbon and the steam ((m) is the number of the atoms of the hydrocarbon) as the reference value, is used from the outside pipe 26' of the tuyere 23 at the flow rate indices X, Y expressed by equation I if the mixing ratio of the steam is below the reference value and expressed by formula II if the above-mentioned ratio is above the reference value in order to prevent the tuyere 23 from rising to an extremely high temp. and from eroding in such a case. The service life of the tuyere 23 is thus prolonged while the deterioration in the material quality of the molten steel is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scrap melting furnace for melting scrap, a smelting reduction furnace for smelting and reducing ores,
A tuyere provided under a molten metal surface of a furnace bottom or a furnace wall of a metallurgical reaction furnace mainly for a steelmaking furnace such as a top-bottom blowing converter or a bottom-blowing converter, a gas for melting or refining, Alternatively, the present invention relates to a method for cooling tuyeres of multiple tubes such as a double tube and a triple tube for blowing powders of these gases and refining agents.

[0002]

2. Description of the Related Art Regarding furnaces for steelmaking, oxygen top blowing converters have been the mainstream in the past, but in recent years, especially in Japan, composite blowing converters, so-called top and bottom blowing converters have become popular. In this way, the top-bottom blow converter has come to be prized because the superior refining function of the top-bottom blow converter has attracted attention for the top-blown converter or the bottom-blown converter. In addition, it is largely due to the improvement of technology to extend the life of the bottom blowhole.

As a method of extending the life of the bottom tuyere, a multi-tube tuyere such as a double-tube tuyere or a triple-tube tuyere having a cooling gas passage in the blowing tuyere is used, and the tip of the tuyere is used. The method of protecting the tuyere by forming mushrooms is widely used. For this mushroom, for example,
"Iron and Steel" Regular Lecture Summary, 1981, S 873, 1982, S
The generation mechanism and properties are introduced in 889.

A cooling method for such a multi-tuyere is as follows:
There is a method using an inert gas such as Ar or N ₂ , or a method using only CO ₂ gas. However, in any case, it is difficult to stably control the bottom blowing gas flow rate due to the growth of mushrooms, Ar gas is expensive, and N ₂ gas is absorbed as nitrogen element in the molten steel and adversely affects the quality of the steel. There are drawbacks such as exerting

In the case of CO ₂ gas, Fe + CO ₂ = FeO + CO FeO + C * = Fe + CO (C * is MgO-C brick graphite) reaction occurs in the low-carbon region at the end of converter refining. Since the bricks around the mouth tend to melt, it is unsuitable for stable and sufficient exertion of the superior refining function of the top-and-bottom blow converter (Abstracts of the lecture by "Iron and Steel", 1984 Year, S 945).

On the other hand, there is a tuyere cooling method in which a relatively large amount of hydrocarbon gas such as propane gas or kerosene is blown into the tuyere outer tube to utilize the heat absorption by the thermal decomposition of these gases.

[0007] This method has a self-cooling control function of keeping the formation of mushrooms, which is not recognized by cooling with Ar, N ₂ and CO ₂ gas, constant, but some hydrogen atoms generated by thermal decomposition are It is known that it is absorbed in molten steel and adversely affects the quality of steel. In addition, since expensive propane gas or kerosene is used in this method, an increase in refining cost cannot be avoided.

[0008]

An object of the present invention is to reduce the amount of expensive hydrocarbon gas used for cooling the multi-tuyere of a metallurgical reactor to suppress the absorption of hydrogen into molten steel. The object of the present invention is to provide a tuyere cooling method capable of stably controlling the bottom blown gas flow rate while keeping the generation of mushrooms at the tip of the tuyere constant.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is to "inject a mixed gas of hydrocarbon gas and water vapor from an outer tube of a multi-tube tuyere provided below a molten metal bath surface of a metallurgical reactor. Characteristic method for cooling multiple metal tuyere of metallurgical reactor ”.

In the present invention, the metallurgical reaction furnace means a furnace such as an electric furnace whose main purpose is melting, including blast furnaces, converters, various furnaces for performing iron-making reactions such as AOD furnaces and steel-making reactions. .

The tuyere below the bath surface of the molten metal is generally provided at the bottom of the furnace, but may be provided at a position such as the side wall of the furnace as long as it is below the bath surface.

The multiple tube tuyere is provided below the surface of the molten metal bath of the metallurgical reaction furnace and is used for blowing gas or gas and powder. In the case of the double tube tuyere, it is Injecting oxidizing gas from the tube and cooling gas from the outer tube, in the case of a triple tube tuyere, flow the powder with the inert gas from the central tube,
Often, an oxidizing gas is blown from the middle pipe and a cooling gas is blown from the outermost pipe. The oxidizing gas is either oxygen gas alone or a mixed gas of oxygen gas and an inert gas (for example, air). In the method of the present invention, a mixed gas of hydrocarbon gas and steam is blown from the outer tube.

In carrying out the method of the present invention, the case where the mixing volume ratio of the hydrocarbon-based gas and the steam is 1: 2 m is taken as a standard value, and the mixing volume ratio of the steam is + 50% of the standard value or more and + 10%. If the mixing volume ratio of water vapor is below the reference value, the tuyere is cooled by blowing the mixed gas with the flow index shown in the following formula (1) and above the reference value when it is above the reference value. Is desirable.

[0014]

[Equation 2]

[0015]

In the cooling method using the mixed gas of hydrocarbon gas and water vapor according to the present invention, the tuyere is cooled by utilizing the heat of endothermic reaction of the mixed gas. Hydrocarbon-based gas is, for example, methane (CH
₄ ) When the gas is used, the endothermic reaction between methane gas and water vapor (H ₂ O) is represented by the following equation (3).

[0016]

[Equation 3]

On the other hand, in the conventional cooling method using only hydrocarbon gas, the tuyere is cooled by utilizing the heat of endothermic reaction due to the thermal decomposition of the gas. For example, the thermal decomposition endothermic reaction when methane gas is used is shown by the following equation (4).

[0018]

[Equation 4]

Comparing the endothermic reaction heats of the above equations (3) and (4), the equation (3) has an endothermic amount of 199.11 / 92.75 = 2.15 times per mole of methane gas as compared to the equation (4) reaction. ing.
Therefore, according to the method of the present invention, the amount of methane gas required to obtain the same cooling effect as the conventional method can be reduced to 1 / 2.15 = 0.47 times. As a result, as shown in Table 1, the cost of the tuyere cooling gas can be reduced to about half that of the conventional method by the method of the present invention.

[0020]

[Table 1]

The reaction of the formula (3) generates 4/2 = 2 times more H ₂ per mol of methane gas than the reaction of the formula (4). Has an endotherm. Therefore, from the viewpoint of the same cooling effect, the method of the present invention only produces 2 / 2.15 = 0.93 times more H ₂ than the conventional method. As a result, the method of the present invention can suppress the absorption of hydrogen into the molten steel and reduce the adverse effect of hydrogen on the steel quality.

[0022]

[Equation 5]

Since this temperature is a temperature that can easily occur inside the tuyere or mushroom,
Both the reactions of Eqs. (3) and (4) have the ability to control self-cooling to keep mushroom formation constant. Therefore, the method of the present invention is superior to the conventional cooling method using Ar, N ₂ or CO ₂ gas and has the same stable controllability of the bottom blown gas flow rate as the cooling method using a hydrocarbon-based gas.

Next, hydrocarbon gas (CmHn) and steam (H
An appropriate range of the mixing volume ratio with ₂ O) will be described.

[0025]

[Equation 6]

Here, m is the number of C atoms in the hydrocarbon gas, and n is the number of H atoms in the hydrocarbon gas.

Therefore, CmHn and H _{2 which} are preferred in the present invention are
The mixing volume ratio of O 2 is 1: 2 m. That is, CmHn is 1
/ (1 + 2m), H ₂ O is 2m / (1 + 2m) When the mixed gas is blown at a mixing volume ratio of CmHn and H ₂ O, the endothermic reaction of the formula (3) proceeds without excess or deficiency. . And this H ₂ O mixed volume ratio 2m
/ (1 + 2m) is the standard value, and if H ₂ O is less than this standard value, it will be in excess of CmHn consumed in the reaction of the above formula (3).
CmHn will be present in the mixed gas. This excess Cm
Hn is a thermal decomposition endothermic reaction of the following formula (6), and cooling is performed in the same manner as with conventional hydrocarbons.

[0028]

[Equation 7]

On the other hand, when H ₂ O is larger than this reference value,
(5) excess H ₂ O from H ₂ O to be consumed in the reaction of the formula will be present in the mixed gas. This excess H ₂ O is
The tuyere is cooled by the endothermic reaction of equation (7).

[0030]

[Equation 8]

[0031] Using the above endothermic reaction, when determining the relationship between the mixing ratio by volume and CmHn and H ₂ O flow rate of of H ₂ O to obtain a conventional method and the same cooling effect of the blowing CmHn plain, below
Equations (8) and (9) are obtained. The flow rate of the mixed gas was expressed as an index with an appropriate flow rate of the conventional CmHn plain gas cooling method (the endothermic reaction of the above formula (4)) being 1 mol / Hr. The H ₂ O mixing volume ratio is calculated from the mol ratio of the reaction in the above equation (3).
The mixing ratio of H ₂ O of 2 m / (2 m + 1) is used as a reference value, and the rate of increase or decrease of this reference value is shown.

(A) When the mixture ratio of H ₂ O is less than the standard value:

[0033]

[Equation 9]

(B) When the mixture ratio of H ₂ O is larger than the reference value

[0035]

[Equation 10]

When methane (CH ₄ , m = 1) is used as the hydrocarbon gas, the CH ₄ flow rate index and H ₂ O flow rate index and H ₂ O in the mixed gas that achieve the same cooling effect as the conventional method can be obtained. The relationship with the mixed volume ratio of is shown in FIG. In addition, when the mixing volume ratio of H ₂ O is -100% of the standard value, it corresponds to the conventional method of cooling only with CH ₄ .

As shown in the figure, when the mixed volume ratio of H ₂ O is less than -50% of the reference value, the amount of CH ₄ reduction is small,
No significant economic benefit. On the other hand, even if the mixed volume ratio of H ₂ O exceeds + 10% of the standard value, there is almost no effect of further reducing CH ₄ , and the cost merit disappears. Moreover, since H ₂ O is an oxidizing gas, it reacts with molten steel to produce FeO by the reaction of the above formula (7), which promotes the wear of tuyere bricks, which is not preferable.

Therefore, based on the case where the mixing volume ratio of the hydrocarbon gas and steam is 1: 2 m, the mixing volume ratio of the steam is set within the range of -50% to + 10% of the reference value, and When the mixing volume ratio is below the reference value, the mixed gas with the flow index shown in the above formula (8) is blown, and when it is above the reference value, the mixed gas with the flow index shown in the above formula (9) is blown to cool the tuyere. Is desirable.

The effects of the present invention will be specifically described with reference to the following examples.

[0040]

EXAMPLE 1 Scrap and iron ore were melted using a small test cylinder furnace similar to the converter with a furnace volume of 6 m ³ shown schematically in FIG. This furnace has a double tube primary tuyere 3'at the bottom of the furnace.

First, a coke filling layer 7 is formed in the tubular furnace 1 to a level including the primary tuyere 3, and a secondary tuyere 4 is formed thereon.
The ore / scrap packing layer 8 was formed to a level including. O ₂ 800Nm ³ / Hr, methane 14~25Nm ³ / Hr and water vapor 12 from the 'O ₂ 400Nm ³ / Hr, the outer tube 6 from the inner tube 6 of the' hearth double pipe primary tuyeres 3 from the primary tuyeres 3 The coke was burned by blowing a mixed gas of 39 Nm ³ / Hr for the tuyere cooling.

The mixing volume ratio of water vapor of the mixed gas for tuyere cooling is (A) reference value -50%, (B) reference value, (C) reference value + 10%, and the methane gas flow rate and water vapor flow rate are as described above.
The cooling effect was the same as that of the conventional method except for B2 shown in Table 2 which was calculated by the formulas (8) and (9). In B-2, the flow index was multiplied by 1.07 to make the cooling effect 1.07 times that of the conventional method.

Combustion-produced CO gas from the secondary tuyere 4 to O ₂ 800 Nm
Blowing in ³ / Hr for secondary combustion, scrap and iron ore were melted by the combustion heat to produce pig iron 9. 2 minutes before the total amount of scrap melted, stop blowing O ₂ into the inner pipe 6 and remove N ₂
92% by weight of CaO with 60 Nm ³ / Hr as carrier gas, CaF ₂ 8
Desulfurization refining was carried out by injecting 1200% by weight of desulfurizing agent 1200 kg / Hr.

After carrying out this operation for 50 heats, the meltdown length of the furnace bottom double tube primary tuyere 3'was measured to investigate the tuyere cooling effect.

As a comparative example 1, a furnace bottom double tube primary tuyere 3 '
The conventional tuyere cooling in which 32 Nm ³ / Hr of only methane gas was blown from the outer pipe 6 ′ of the above was performed. Other than that, the operation was performed under the same conditions as in Example 1.

Table 2 shows the amount of melting loss at the bottom of the double tube tuyeres and the total cooling gas cost index.

[0047]

[Table 2]

As shown in Table 2, the average tuyere erosion amount of Example 1 was 0.3 mm / heat, which was equivalent to that of Comparative Example 1 of the conventional method. On the other hand, the total cooling gas cost index of Example 1 was reduced to 80 to 52% of that of Comparative Example 1.

[0049]

[Embodiment 2] Steelmaking and refining for converting molten iron into molten steel was carried out by using an upper-bottom blowing converter 21 having a furnace volume of 6 m ³ whose schematic cross section is shown in FIG.

After receiving the hot metal into the converter 21 and charging the slag material, the inner pipes 26 of the two double pipe tuyere 23 provided at the bottom of the furnace are 40 Nm ³ / per tuyere. the Hr O ₂ gas, blowing from the outer tube 26 'methane gas 2 Nm ³ / Hr and the tuyere cooling gas mixture of steam 4 Nm ³ / Hr into the hot metal, O from the top blowing lance 27 ₂ gas 1800 Nm ³ /
Molten steel was manufactured by blowing Hr for decarburization refining. 28 is molten steel and 29 is slag. After performing this operation for 50 heats, the erosion length of the double tube tuyere 23 was measured.

As Comparative Example 2, the outer tube 26 'of the double tube tuyere 23
The conventional tuyere cooling was performed by blowing in methane gas of 4 Nm ³ / Hr. The other conditions were the same as in Example 2, and the operation was carried out.

Table 3 shows the amount of melting loss of the furnace bottom double tube tuyere in Example 2 and Comparative Example 2 and the hydrogen content in molten steel at the time of blowing stop (hereinafter referred to as [H]).

[0053]

[Table 3]

As shown in Table 3, the average erosion loss of the tuyere of Example 2 was 0.2 mm / heat, which was equivalent to that of Comparative Example 2 of the conventional method. On the other hand, the total cooling gas cost index could be halved compared to 1 in Comparative Example 2. Looking at the average blow-off [H] at the time of blow-off of the converter, [H] of Example 2 is suppressed to a lower level than that of Comparative Example 2.

[0055]

According to the method of the present invention, by blowing a mixed gas of a hydrocarbon-based gas and water vapor into the outer tube side of a multi-tube tuyere provided below the surface of a molten metal bath, a conventional hydrocarbon-based gas unit It is possible to maintain the amount of tuyere melting loss equivalent to that of the taste tuyere cooling method and a low [H] level in molten steel. Moreover, the bottom blown gas flow rate can be controlled stably, the amount of expensive hydrocarbon-based gas used can be reduced, and the tuyere cooling gas cost can be significantly reduced. Therefore, a good tuyere cooling effect equivalent to that of the conventional method can be obtained at a low cost, and the effect of reducing the manufacturing costs of pig iron and steel is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a CH ₄ flow rate index and a H ₂ O flow rate index in a mixed gas and a mixing volume ratio of H ₂ O in which the same cooling effect as that of a conventional method can be obtained.

FIG. 2 is a schematic sectional view of a cylindrical furnace used in an example of the method of the present invention.

FIG. 3 is a schematic sectional view of an upper bottom blowing converter used in another embodiment of the method of the present invention.

Claims (2)

[Claims] 1. A multi-tube tuyere of a metallurgical reaction furnace, wherein a mixed gas of a hydrocarbon-based gas and steam is blown from an outer tube of the multi-tube tuyere provided below a molten metal bath surface of the metallurgical reaction furnace. Cooling method. 2. A standard value is the case where the mixing volume ratio of the hydrocarbon gas and steam is 1: 2 m (m is the number of carbon atoms of the hydrocarbon), and the mixing volume ratio of the steam is from -50% of the standard value. +
In addition to the range up to 10%, if the mixing volume ratio of water vapor is below the reference value, the following formula (1), if it is above the reference value,
The method for cooling a multi-tube tuyere of a metallurgical reaction furnace according to claim 1, wherein a mixed gas having a flow index shown in the equation (2) is blown. [Equation 1]