JPH11246902A - Lance for injecting powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lance for injecting powder which is inclinatorily used and has an excellent cooling effect in the pretreatment of molten iron, particularly at the time of dephosphorizing. SOLUTION: In a double tube system lance 3 for injecting powder which is used by inclinatorily immersing it into molten iron and formed with an inner tube 4 for passing flux for refining and gaseous oxygen and with an outer tube 1 for passing a cooling gas, partition members 10 are provided along the longitudinal direction of a tube axis so as to partition a gap formed with the inner tube and the outer tube surrounding the inner tube into at least two cooling gas 6 flowing passages in a cross section crossing in the longitudinal direction at the tube axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lance for blowing powder, and more particularly to a method for blowing a flux of iron oxide, lime, etc. and gaseous oxygen into molten iron before oxygen blowing in a converter to remove silicon. And a lance for blowing powder used in so-called hot metal pretreatment for dephosphorization.

[0002]

2. Description of the Related Art In recent years, in steelmaking, before hot metal is oxygen-blown and decarburized in a converter, the hot metal is desiliconized, dephosphorized, and desulfurized in advance to reduce the refining load in the converter. became. Since the hot metal pretreatment is performed by adding or blowing the flux as a refining agent to the hot metal, the hot metal temperature tends to decrease. In recent years, since low phosphorus and low sulfur steels have been required more than ever before, the amount of flux charged into the hot metal has increased, and the hot metal temperature has been further decreasing. Therefore, at present, in the next step of decarburization in the converter, a heating agent is added to the pretreated hot metal,
Alternatively, the flux input amount in the hot metal pretreatment is restricted so as to avoid insufficient temperature in the decarburization treatment.

[0003] One of the methods for suppressing the drop of the hot metal temperature is a technique of blowing gaseous oxygen into the hot metal in addition to the flux when performing desiliconization and dephosphorization in the hot metal pretreatment. This is to reduce the drop in hot metal temperature by an amount corresponding to the sensible heat of iron oxide by substituting a part of oxygen in iron oxide as a heat source with gaseous oxygen. For example, Japanese Patent Application Laid-Open No.
No. 80909 discloses a technique for blowing oxygen gas into hot metal through a lance separate from a flux blowing lance. However, this technology has
When applied to the case where a car is used as a reaction vessel, refractories around the receiving port of the topped car are severely worn, and the frequency of repair work and the cost of the refractories are increased.

[0004] Further, "Iron and steel" vol. 82 (199
6), p569, discloses a technique for simultaneously injecting a dephosphorizing agent and gaseous oxygen through a single single-tube lance. However, in this technique, the ratio of gaseous oxygen to the total amount of oxygen used (the amount of gaseous oxygen + the amount of oxygen of iron oxide) (hereinafter, referred to as the oxygen content)
When the gaseous acid ratio is increased), the lance wear rate increases, causing an increase in the frequency of lance exchange and a reduction in the desiliconization or dephosphorization treatment ratio.

Therefore, Japanese Patent Application Laid-Open No. 58-22212 proposes that the lance has a double-pipe structure, in which hydrocarbon gas is blown from the outer pipe and flux and gaseous oxygen are blown from the inner pipe. However, in this lance, when the lance itself was insufficiently cooled and the gas-acid ratio was increased, the amount of wear of the lance increased. JP-A-60-162712 discloses a technique of blowing (iron oxide + nitrogen gas) from an outer tube and blowing (slagging agent + gaseous oxygen) from an inner tube using a lance having a double tube structure similar to the above. Was disclosed. However, in this technique, since the powder is blown from the outer tube having a narrow gap, the gap must be enlarged to prevent clogging. For this reason, the diameter of the lance becomes extremely large, and not only is the production cost high, but also the labor for replacing the lance becomes large.

[0006]

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide a lance for injecting powder having an excellent cooling effect, which is used in an inclined manner in hot metal pretreatment, particularly during dephosphorization. And

[0007]

Means for Solving the Problems In order to achieve the above object, the inventor investigated the state of erosion of a lance for blowing powder which is immersed and inclined in hot metal at the time of hot metal pretreatment. As a result, it was found that the erosion was remarkable in the portion on the upper surface side when the lance was inclined, and the result of intensive study of the countermeasure was completed as the present invention.

[0008] That is, the present invention is a double-pipe type powder blowing apparatus which is used by being inclined and immersed in hot metal and formed by an inner pipe through which a refining flux and gaseous oxygen pass and an outer pipe through which a cooling gas passes. A partitioning member extending along the longitudinal direction of the pipe so as to partition a gap formed by the inner pipe and the outer pipe surrounding the inner pipe into at least two cooling gas flow paths at a cross section intersecting the longitudinal direction of the pipe. This is a powder blowing lance characterized by having a lance.

Further, in the present invention, a gas distribution means is provided so that a larger amount of cooling gas can pass through the cooling gas passage divided into two by the partition member and which becomes the upper surface side due to the inclination of the lance. A lance for blowing powder, characterized in that: Further, the present invention provides a double-pipe type powder injection lance which is used by being inclined and immersed in hot metal and formed by an inner pipe through which a flux for refining and gaseous oxygen passes and an outer pipe through which cooling gas passes. The powder injection lance according to any one of claims 1 to 3, wherein the inner pipe is eccentric with respect to the pipe axis of the outer pipe.

[0010] In addition, the present invention is the powder blowing lance, wherein the cooling gas flow path which becomes the upper surface side by the inclination of the lance is a flow path whose cross section is widened by the eccentricity. In addition, the present invention is also a powder injection lance, wherein the refining flux is iron oxide and / or quick lime, or the cooling gas is a hydrocarbon-based gas.

According to the present invention, the lance used for dipping and inclining in the hot metal for the hot metal pretreatment is structured as described above, so that the cooling of the upper surface side of the lance is promoted. As a result, lance erosion is reduced and its life can be extended.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, an explanation will be given of an example in which a powder injection lance (hereinafter, referred to as a lance) according to the present invention is used for dephosphorization of hot metal held in a topped car. I do. As described above, conventionally, two types of steel pipes having different diameters are combined so as to draw concentric circles to form a double structure, and the surface of the outer pipe 1 is made of a refractory material 2 such as Al ₂ O _3. There is a lance 3 covered and protected by. In addition, a refining flux 8 (hereinafter, referred to as a dephosphorizing agent) is flown into the inner pipe 4, and a cooling gas 6 is flown into the outer pipe 1, that is, a gap between the inner pipe 4 and the outer pipe 1. When such a lance 3 is immersed in hot metal, and gas oxygen 7 and a dephosphorizing agent 8 are flowed into the inner tube 4 and used for dephosphorizing the hot metal, compared with the case where the iron oxide and the dephosphorizing agent 8 are flowed, There is an advantage that the drop in hot metal temperature can be suppressed because there is no endothermic decomposition of iron oxide.

When refining is performed by injecting powder into the hot metal in the torpedo car, the lance is usually inclined to form a circulating flow of the hot metal throughout the torpedo car. Immerse in hot metal. However, due to insufficient cooling near the powder outlet of the lance 3, the lance 3 is abnormally worn, that is, the upper surface side is severely melted due to the inclination. Therefore, a cooling gas 6 such as a hydrocarbon-based gas has been conventionally used for the outer tube 1. Nevertheless, since the erosion of the upper surface was unavoidable, the inventor measured the temperature distribution of the cooling gas 6 passing through the gap between the inner tube 4 and the outer tube 1 of the lance 3.
As a result, the temperature of the cooling gas 6 on the upper surface side was higher than the temperature on the lower surface side, and the cause of the preferential wear of the upper surface side of the lance 3 became clear.

Therefore, the inventor of the present invention provided a partition member along the longitudinal direction of the pipe, as shown in FIG. 1, in the gap between the inner pipe 4 and the outer pipe 1, and provided at least two chambers in the gap. Divided into two parts. Thereby, the cooling gas 6 flowing in the outer pipe 1 has at least two different flow paths. Since a larger amount of the cooling gas 6 is caused to flow through the flow path on the upper surface side due to the inclination, the cooling on the upper surface side is promoted, and the temperature rise in that portion is suppressed.

In FIG. 1, a plate-like partition member 10 is disposed on an extension passing through the center axis of the inner tube 4. In this case, the flow rate of the cooling gas 6 flowing through the two flow paths may be adjusted differently by separately provided distributing means (not shown).
More specifically, if two pipes for supplying the cooling gas 6 to the lance 3 are provided, and each of the pipes is provided with an on-off valve, or one pipe is branched in the middle of the two pipes and different flow rates are supplied to the respective pipes, good. Further, in the present invention, it has been considered that the partition member 10 is attached so that an extension of the partition member 10 deviates from the tube axis of the inner tube 4, and the sectional areas of the two chambers are made different. Thereby, the flow rate can be adjusted only by providing one cooling gas pipe without disposing the distribution means.

Further, by developing this idea, the present invention provides:
An eccentric lance 3 as shown in FIG. 2 is also proposed. That is, the arrangement of the inner tube 4 and the outer tube 1 in the cross section is not concentric but offset. Thus, even if the large partition member 10 is not used to form two chambers, a simple fixing member (spacer) 9 is inserted into the gap between the inner and outer pipes, so that the cooling gas 6 flowing in the outer pipe 1 has a flow distribution related to the cross section. Become like That is, the lance 3 is used by setting the side having the larger cross-sectional area to the side requiring more cooling. Note that the length of the spacer 9 used for changing the cross-sectional area may be determined according to a desired cross-sectional area. The material may be the same as that of the partition member 10, and a steel material having high heat resistance,
Alternatively, ceramic can be used. Further, the cooling gas 6 used may be a nitrogen gas or an argon gas, but is preferably a hydrocarbon-based gas which thermally decomposes and absorbs heat in the lance 3.

[0017]

[Example] About 200 tons of hot metal from a blast furnace was charged into a torpedo car, and a dephosphorizing agent was blown into the hot metal through three kinds of lances 3 having different structures, which were inclined and immersed. Dephosphorization was performed. At that time, in any method, CaO and iron oxide were used as the dephosphorizing agent 8 as the refining flux, which was mixed with gaseous oxygen 9 and blown. The dephosphorizing agent 8
Is 300 to 350 kg / min, the gas oxygen 9 is blown at 0 to ³⁰ Nm ³ / min, and the blowing time is 2 kg / min.
0-30 minutes.

The results are shown in FIG. 3 as a relationship between the gaseous acid ratio and the lance life (standardized as 1 when the gaseous acid ratio = 0 in a conventional single tube). When a conventional single tube type lance is used as the lance 3 (Comparative Example 1), the life of the lance is shortened as the gas-acid ratio increases. When the inner pipe 4 and the outer pipe 1 are simply arranged concentrically, and a dephosphorizing agent and gaseous oxygen are flowed into the inner pipe 4 and propane gas is flown as the cooling gas 6 into the outer pipe 1 (Comparative Example 2). The lance life is longer than that of Comparative Example 1. However, as the gas acid ratio increases, its lifetime decreases.

When the lance according to the present invention (FIG. 1) is used (Example) as compared with the case where these conventional lances are used, the life is almost shortened even if the gas-acid ratio changes. It seems that there was an excellent cooling effect. At this time, the total propane flow rate as the cooling gas was the same as in Comparative Example 2, and different flow rates were respectively passed through the two cooling gas flow paths of the lance. That is, the flow ratio of propane gas flowing through the cooling gas flow path on the upper surface side and the lower surface side of the lance was set to 1.5: 1. In the case of this example and comparative example 2, the temperature in the cooling gas flow path was actually measured at the tip of the lance. Table 1 shows the results. From Table 1, it can be seen that in Comparative Example 2, there was a temperature difference of 100 ° C. or more between the upper surface side and the lower surface side of the lance in the flow path, but in the example, it was almost uniform.

[0020]

[Table 1]

[0021]

As described above, according to the present invention, in the hot metal pretreatment, the life of the lance used by being inclined and immersed in the hot metal can be extended even if gas oxygen is used. became.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of a lance according to the present invention.

FIG. 2 is a sectional view showing another embodiment (eccentric type) of the lance according to the present invention.

FIG. 3 is a diagram comparing the life of a lance between a lance according to the present invention and a conventional lance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer pipe 2 Refractory 3 Lance 4 Inner pipe 5 Gap 6 Cooling gas 7 Gas oxygen 8 Dephosphorizer 9 Spacer 10 Partition member

Claims (6)

[Claims] 1. A double-pipe type powder injection lance which is used by being inclined and immersed in hot metal and formed by an inner pipe through which a refining flux and gas oxygen pass and an outer pipe through which a cooling gas passes. The gap formed by the inner tube and the outer tube surrounding it,
A powder blowing lance, characterized in that a partition member is provided along the longitudinal direction of the pipe so as to partition at least two cooling gas flow paths at a cross section intersecting with the longitudinal direction of the pipe. 2. A gas distributing means for allowing a larger amount of cooling gas to pass through a cooling gas flow path partitioned by the partition member, the flow path being on the upper surface side due to the inclination of the lance. The lance for blowing powder according to claim 1. 3. A double tube type powder injection lance which is used by being inclined and immersed in hot metal and formed by an inner tube through which a refining flux and gaseous oxygen pass and an outer tube through which a cooling gas passes. A powder blowing lance, wherein the inner pipe is eccentric with respect to the pipe axis of the outer pipe. 4. The powder blowing lance according to claim 3, wherein the cooling gas flow path which becomes the upper surface side by the inclination of the lance is a flow path whose cross section is widened by the eccentricity. 5. The method according to claim 1, wherein the refining flux comprises iron oxide and / or iron oxide.
5. The powder injection lance according to claim 1, wherein the lance is formed as quicklime. 6. The lance according to claim 1, wherein the cooling gas is a hydrocarbon-based gas.