JP2001207207A - Double pipe tuyere for blowing hydrocarbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape of a double pipe tuyere which is capable of suppressing the flow rate of the inert gas to be passed to an outer pipe of the double pipe tuyere as far as possible. SOLUTION: (1) The double pipe tuyere for blowing hydrocarbon from an inner pipe and the inert gas from the outer pipe, respectively, into molten metal is 0.08 to 2.0 in the ratio S/So of the flow passage sectional area So (m2) of the inner pipe and the flow passage sectional area S (m2) of the outer pipe and (2) the (S+/So)/St determined by using the total sectional area St (m2) of the tuyere satisfies 0.08 to 0.8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double tube tuyere for blowing hydrocarbons into molten metal.

[0002]

2. Description of the Related Art It is widely known that it is effective to enhance the stirring of molten steel in order to efficiently advance decarburization refining in a converter. For this reason, the current converter is equipped with a bottom-blowing tuyere for the purpose of stirring molten steel in addition to the top-blowing lance, which is the main oxygen supply source, to provide oxygen, hydrocarbons, and inert gas (A
r, N ₂ , CO, CO _2, etc.) are blown into the molten steel through the tuyere. When oxygen is blown from the bottom tuyere, a large amount of reaction heat is generated and there is a risk of nozzle erosion. To prevent nozzle erosion, methane, propane, butane, etc. with a flow rate of 10% or less of the oxygen flow rate is used. Generally, oxygen is blown from the inner tube and hydrocarbons are blown from the outer tube of the double tube in combination with hydrocarbons.

[0003] By utilizing the endothermic reaction when the hydrocarbon is decomposed, the exothermic reaction due to oxygen can be offset on the heat balance, and the bottom blown tuyere can be prevented from being damaged. Therefore, the prior art does not attempt to inject a large amount of hydrocarbons, and even if it is injected, the tuyere refractory receives thermal stress due to supercooling and breaks, or a molten metal solidified mass at the tuyere tip. It is difficult to stably inject hydrocarbons because the tuyere is clogged due to the formation of ash.

The present inventors have proposed in Japanese Patent Application Laid-Open No. H11-172319 a method in which hydrocarbon is blown from the inner tube of a double-tube tuyere and a heat-insulating gas such as an inert gas is blown from an outer tube. According to this proposal, a large amount of inexpensive hydrocarbons can be blown in place of expensive inert gas, the mixing of molten metal is promoted, and the speed of refining can be increased.

[0005]

However, the need for high-speed refining has further increased, and the amount of hydrocarbon injected has been increasing, and the amount of inert gas injected into the outer pipe required for heat insulation of the inner pipe hydrocarbons has been increasing. Has also reached its limit in terms of cost, and it has been desired to suppress the flow rate of the inert gas in the outer tube as much as possible.

An object of the present invention is to provide a shape of a double tube tuyere capable of suppressing the flow rate of an inert gas flowing through the outer tube of the double tube tuyere as much as possible.

[0007]

The present inventors have obtained the following findings.

(A) The hydrocarbon flowing through the inner pipe (hereinafter simply referred to as the inner pipe hydrocarbon, and the inert gas flowing through the outer pipe is also referred to as the outer pipe inert gas) flows from the hydrocarbon supply pipe. After passing through the control valve, it is introduced into the tuyere and finally blown into the molten iron from the tuyere tip. The pressure from the flow control valve outlet to the tuyere is defined as the tuyere pre-pressure. Therefore, even when the inner pipe hydrocarbons having the same flow rate are flowing, if a huge mushroom is formed at the tuyere tip, the tuyere pre-pressure increases.

(B) The tuyere pre-pressure of the inner pipe hydrocarbon is set to about 0.6
Relationship between the ratio (S / So) of the inner pipe cross-sectional area So and the outer pipe cross-sectional area S that can be maintained at MPa, and the ratio (Q / Qo) of the outer pipe inert gas flow rate Q and the inner pipe hydrocarbon flow rate Qo Was investigated.

The tuyere pre-pressure of the inner pipe hydrocarbon is set to about 0.6.
It is known from preliminary test results that the tuyere is stable when the tuyere can be maintained, and the tuyere pre-pressure was kept constant at about 0.6 MPa.

The ratio (S / So) of the inner pipe cross-sectional area So to the outer pipe cross-sectional area S is hereinafter simply referred to as a flow path area ratio.

Further, the ratio (Q / Qo) between the outer pipe inert gas flow rate Q and the inner pipe hydrocarbon flow rate Qo is hereinafter simply referred to as the outer pipe flow rate ratio.

FIG. 1 is a graph showing the relationship between the flow path area ratio (S / So) and the outer pipe flow rate ratio (Q / Qo).

As shown in FIG. 1, the flow path area ratio (S / S
When o) is less than 0.08, the outer pipe flow ratio for maintaining P at about 0.6 MPa is large, and when S / So exceeds 2, the cross-sectional area of the outer pipe becomes too large and P becomes about 0.6 MPa. It was also found that the outer pipe flow ratio for maintaining the pressure increased.

FIG. 2 shows that the tuyere front pressure is constant at about 0.6 MPa,
It is a graph which shows the relationship between the flow path area ratio (S / So) and the tuyere wear rate index under the condition that the outer pipe flow rate ratio (Q / Qo) is constant at 0.05.

It should be noted that the tuyere wear rate index is determined by the flow path area ratio (S
/ So) is 0.5 and the tuyere wear rate (mm / charge) is 1 when the outer tube flow ratio (Q / Qo) is 0.0035.

As shown in FIG. 1, when the ratio (S / So) is 2 or less, the tuyere wear rate index is about 1, but when it exceeds 2, the tuyere abrasion rate index increases rapidly.

From FIGS. 1 and 2, it can be seen that the flow path area ratio (S / S
It has been found that o) is preferably set to 0.08 to 2.0. The preferable range of the flow path area ratio (S / So) is 0.1 to 1.2.

Further, it has been found that the ratio ((S + So) / St) of the total cross-sectional area including the hardware: St to the tuyere cross-sectional area: S + So is related to the tuyere wear rate index.

The ratio ((S + So) / St) of the total cross-sectional area including hardware: St to the tuyere cross-sectional area: S + So is as follows.
It is simply referred to as a flow path cross-sectional ratio.

FIG. 3 shows that the flow path area ratio (S / So) is 0.5
It is a graph which shows the relationship between the flow path cross-sectional ratio ((S + So) / St) and the tuyere wear rate index under the condition that the outer pipe flow rate ratio (Q / Qo) is constant at 0.05.

As shown in the figure, the ratio ((S + So) / S
It was found that the tuyere wear rate index further decreased when t) was in the range of 0.08 to 0.8.

FIG. 4 shows that the outer pipe flow rate ratio (Q / Qo) is 0.0
5 Tuyere wear rate index under constant conditions, flow path area ratio (S / So) and flow path cross-sectional ratio ((S + So) / St)
6 is a graph showing a relationship with the graph.

In the figure, the x mark indicates that the tuyere wear rate index is 3
The circles in the figure indicate that the tuyere attrition rate index is 0.
In the drawing, the symbol ◎ indicates that the tuyere is worn and the rate of wear (index) is less than 0.7.

From the above, in order to reduce the tuyere wear rate index to less than 1.5, the flow path area ratio (S / So) must be 0.08 to 0.08.
In order to reduce the tuyere wear rate index to less than 0.7, it is necessary to set the flow path cross-sectional ratio ((S + S
It was found that setting o) / St) to 0.08 to 0.8 was effective.

The present invention has been made based on the above findings, and the gist thereof is as follows. (1) A double tube tuyere for blowing a hydrocarbon from an inner tube and an inert gas from an outer tube into a molten metal,
Channel cross-sectional area So (m ² ) of inner pipe and channel cross-sectional area S of outer pipe
A double-tube tuyere for blowing hydrocarbons, wherein the ratio S / So to (m ² ) is 0.08 to 2.0. (2) It is obtained using the tuyere's total cross-sectional area St (m ² ) (S + S
o) The double-tube tuyere for hydrocarbon injection according to the above (1), wherein / St satisfies 0.08 to 0.8.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The double tube of the present invention is applied to, for example, a bottom tuyere of a top-bottom blowing converter.

FIGS. 5 (a) and 5 (b) are cross-sectional views conceptually showing the structure of the double pipe of the present invention. FIG. 5 (a) shows a normal double pipe tuyere, and FIG. b) shows an outer tube split type double tube, respectively.

The range shown in black represents the flow path of the hydrocarbon and the inert gas, and the range shown in white represents the hardware of the tuyere.

The ordinary double pipe shown in FIG. 5A is composed of an inner pipe and an outer pipe.

The outer tube split type double tube shown in FIG. 5B is composed of an inner tube and a small-diameter tube surrounding the inner tube corresponding to the outer tube.

According to the present invention, the inner pipe and the outer pipe are respectively connected to the hydrocarbon supply pipe and the inert gas supply pipe via the flow control valves.

The flow passage cross-sectional area So (m ² ) of the inner tube of the present invention is:
A black circle at the center of FIG. 5A is shown, and a black circle at the center of FIG. 5B is shown.

The flow path cross-sectional area S (m ² ) of the outer tube of the present invention indicates the black ring area in FIG. 5A and the total area of the black satellite-like circle in FIG. 5B, respectively.

Further, the tuyere total cross-sectional area St (m ² ) of the present invention.
5A and 5B are the total area of the flow channel area of the hydrocarbon and the inert gas in the range shown in black and the tuyere hardware area in the range shown in white.

In the double tube tuyere of the present invention, hydrocarbon is introduced into the inner tube and inert gas is introduced into the outer tube.

The hydrocarbons used are CH ₄ , C ₂ H ₆ , C
₃ H ₈ , C ₄ H _{10 and the} like can be used alone or as a mixture.

The inert gas used is Ar, N ₂ , CO,
CO ₂ or the like can be used alone or as a mixture.

The double-tube tuyere of the present invention has a tuyere pre-pressure of about 0.5.
The operation management is preferably performed so as to maintain the pressure at 6 MPa, but may be in the range of 0.3 to 0.9 MPa.

The tuyere pre-pressure can be measured by any gas pressure measuring device capable of measuring the pipe pressure from the flow control valve outlet to the tuyere. For example, a Bourdon tube pressure gauge or a diaphragm type pressure gauge can be used.

The double-tube tuyere of the present invention can be applied to a bottom-blowing tuyere of an upper-bottom-blowing converter, a side-blowing / bottom-blowing tuyere of various refining furnaces, or a nozzle of an injection lance.

[0042]

EXAMPLE A 250 mass ton (temperature: 1200 to 1300 ° C.) of hot metal of a representative component shown in Table 1 was charged into a converter, and oxygen gas was supplied at 850 m ³ (standard condition) / min by a lance (6 holes, inclination angle). (15 degrees, throat diameter 48 mm, lance height 2.5 m).

[0043]

[Table 1]

At the time of the upper blowing, four tuyeres provided at the bottom of the converter furnace provided 5 m of LPG as hydrocarbons in the inner tube for each tuyere.
³ (standard state) / min, CO ₂ as an inert gas in the outer pipe is 9000 m ³ (standard state) at a flow rate per 1 m ^{2 of} outer pipe cross-sectional area
/ min, and blown until [C]: 0.05%.

Table 2 shows the test results when the test was performed under the above conditions.

[0046]

[Table 2]

The evaluation of the flow path area ratio (S / So) in the table is as follows.
A test number that falls within the appropriate range of 0.08 to 2.0 is marked with a circle, and a test number that falls outside the proper range is marked with a cross.

The evaluation of the flow path cross-sectional ratio ((S + So) / St) is based on the test numbers that fall within the appropriate range of 0.08 to 0.8.
, A test number out of this appropriate range was marked with a cross.

When the outer pipe flow rate ratio was 0.05 or more, the weight loss effect was poor, and when it was less than 0.05, the weight loss effect was good.

The tuyere attrition rate index is a relative value with the tuyere attrition rate of test No. 1 as 1.

The tuyere abrasion rate index indicates that the abrasion has deteriorated to more than 1.0, indicates that the abrasion has deteriorated. I attached each.

In the overall evaluation, the test number in which the outer tube flow rate ratio was ○ and the tuyere wear rate index was ○ was marked with ○.

In addition, ◎ was given to the test number in which the outer tube flow rate ratio was ○ and the tuyere wear rate index was evaluated as ◎.

As shown in Table 2, the flow path area ratio (S / S
Test numbers 4 to 9 and 1 where o) is 0.08 to 2.0
In Nos. 4 to 20, the outer pipe flow ratio was less than 0.5, and the tuyere wear rate index excluding Test Nos. 17 to 19 was maintained at the current level of 0.8 to 1.0.

Further, the flow path area ratio (S / So) is 0.08
Test numbers 17 to 19, in which the flow path cross-sectional ratio ((S + So) / St) is 0.08 to 0.8, can reduce the outer pipe flow ratio to less than 0.05. The tuyere attrition rate index was able to be improved to the present level of less than 0.8.

[0056]

According to the present invention, the flow rate of the inert gas flowing through the outer tube of the double tube tuyere can be suppressed as much as possible. Further, the tuyere wear rate can be reduced.

[Brief description of the drawings]

FIG. 1: Flow area ratio (S / So) and outer pipe flow rate ratio (Q / Q)
6 is a graph showing the relationship with o).

FIG. 2 shows the relationship between the channel area ratio (S / So) and the tuyere wear rate index under the condition that the tuyere pre-pressure is constant at about 0.6 MPa and the outer pipe flow rate ratio (Q / Qo) is constant at 0.05. FIG.

FIG. 3 shows the flow path cross-sectional ratio ((S + So) / St) and the tuyere when the flow path area ratio (S / So) is constant at 0.5 and the outer pipe flow rate ratio (Q / Qo) is constant at 0.05. It is a graph which shows the relationship with a wear rate index.

FIG. 4 is a tuyere wear rate index and a flow path area ratio (S / So) under the condition that an outer pipe flow ratio (Q / Qo) is constant at 0.05.
6 is a graph showing a relationship between the flow rate and a flow path cross-sectional ratio ((S + So) / St).

5 (a) and 5 (b) are cross-sectional views conceptually showing the structure of the double pipe of the present invention. FIG. 5 (a) shows a normal double pipe tuyere, and FIG. (B) shows an outer tube split type double tube, respectively.

Claims (2)

[Claims] 1. A double tube tuyere for blowing a hydrocarbon from an inner tube and an inert gas from an outer tube into a molten metal, wherein the cross-sectional area of the flow passage of the inner tube is So (m ² ). channel cross-sectional area S (m ²⁾ and the ratio S / So. double tube tuyere for blowing a hydrocarbon which is a 0.08 to 2.0 of the tube. 2. The hydrocarbon injection according to claim 1, wherein (S + So) / St determined using the tuyere total cross-sectional area St (m ² ) satisfies 0.08 to 0.8. For double tube tuyere.