JP2812852B2 - Hot metal desiliconization and dephosphorization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for desiliconizing and dephosphorizing hot metal.

[0002]

2. Description of the Related Art At present, a process for preliminarily desiliconizing, dephosphorizing and desulfurizing hot metal before charging into a converter and performing only decarburization in the converter to reduce the total cost of the refining process has become widespread. doing. In pre-siliconization and dephosphorization of hot metal, hot metal charged in a topped car or hot metal pot
A method of immersing a lance and blowing a dephosphorizing agent such as solid oxide containing iron oxide as a main component (hereinafter referred to as solid oxygen) and quicklime through a consumable immersion lance has been often used. The biggest weakness of this process is that the temperature of hot metal drops significantly due to the heat of decomposition of solid oxygen and the increase in sensible heat of solid oxygen and quicklime, and the heat margin in the converter, which is the next step, decreases. For this reason, in recent years, a method of compensating the hot metal temperature by replacing part of the iron oxide as an oxygen source with gaseous oxygen and injecting it has been adopted.

[0003] At this time, since the heat of oxidation reaction generated when gaseous oxygen reacts with various components in the hot metal is extremely large, if the same blowing method as when only solid oxygen is used as the oxygen source is adopted, the lance life will be shortened. Significant decline has been expected and industrial application has been considered difficult. Therefore, in order to extend the life of the lance, a method of injecting gaseous oxygen from the inner tube, solid oxygen and quick lime conveyed by inert gas from the outer tube, and technology related to the lance structure using a double-tube lance and technology related to the lance structure have been proposed. No. 24451, Japanese Patent Publication No. 2-25406, Japanese Patent Publication No. 2-55485, and the like. Although these methods certainly extend the lance life,
Due to the complicated lance structure, the cost per lance increases by 4 to 30 times as compared with the single tube type. In addition, the use of a double-lance lance inevitably increases the diameter of the lance, resulting in a significant increase in the weight of the lance and a resulting increase in the load of lance replacement work.

There is also known a method in which solid oxygen and quick lime are blown from an immersion lance and gaseous oxygen is blown onto a bath surface to compensate for hot metal temperature mainly by secondary combustion of CO gas generated in the bath. Although this method does not have the problem of erosion of the immersion lance, it has a problem that refractory at the furnace mouth such as a topped car is significantly worn or splash is generated during operation.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to make use of the advantages of a single-pipe lance with a low lance cost and a small work load, while maintaining an industrially applicable lance life. It is an object of the present invention to provide a technology which enables temperature compensation of hot metal by substituting solid oxygen with gaseous oxygen while securing the temperature.

[0006]

That is, the present invention relates to a method of transporting and blowing a powder comprising a solid oxide containing iron oxide as a main component and a dephosphorizing agent such as quicklime into hot metal with an inert gas or air. When degassing and dephosphorizing hot metal by simultaneously injecting gaseous oxygen, the immersion lance of a single tube is gripped by a lance holder, and the lance holder is formed as a double tube consisting of an inner tube and an outer tube. In the vicinity, the pipe is connected to an independent oxygen blowing pipe and a powder blowing pipe, and the lower end of the inner pipe is opened in the immersion lance or the lance holder of the single pipe, and the powder supply rate Qflux (kg / Min) and the rate of supply of gaseous oxygen QO ₂ (Nm ³ / min), Qfl
ux / QO ₂ is 6 or more, and the powder and the gaseous oxygen are mixed in advance in the immersion lance or the lance holder of the single pipe and then blown into the hot metal, This is a dephosphorization method.

[0007]

The present invention will be described below with reference to FIGS. FIGS. 1 and 3 schematically show a state in which the present invention is applied to a case where a powder composed of gaseous oxygen, solid oxygen, quicklime, and the like is blown into hot metal filled in a tope car. The solid oxygen 2 discharged into the powder cutting device 1 and the dephosphorizing agent 4 mainly composed of quicklime discharged into the powder cutting device 3 likewise pass through the powder blowing line 5 with air or nitrogen. And is supplied to the inner tube of the lance holder 7. On the other hand, gaseous oxygen is supplied from the oxygen pipe 6 to the outer pipe 7. The powder and the gaseous oxygen separately supplied in this manner are mixed in the downstream portion of the lance holder 7 or in the immersion lance 8, and then blown into the hot metal 10 filled in the torpedo car 9 through the single tube immersion lance 8. .

FIGS. 2 and 4 show enlarged views of an example of the structure of the lance holder. The powder is conveyed by air, nitrogen, or the like, and supplied from the powder introduction tube 11 to the lance holder inner tube 12 connected thereto. On the other hand, gaseous oxygen is supplied from a T-tube 13 for oxygen introduction through a gap between the inner tube 12 and the outer tube 14 of the lance holder. Here, the inner tube 12 of the lance holder is constituted by a tube longer than the outer tube 14 as shown in FIG. 2, and the tip of the inner tube 12 has a structure protruding into the immersion lance 8, so that powder and gaseous oxygen Mixed with
Alternatively, as shown in FIG. 4, the inner pipe 12 is formed of a shorter pipe than the outer pipe 14, and the inner pipe 12 is opened into the outer pipe 14 to form a single pipe of the outer pipe 14. Oxygen is mixed. The powder and gaseous oxygen mixed in this way are transferred to the outer tube of the lance holder.
It is supplied at least into the immersion lance 8 through the connection portion 15 of the single-tube type immersion lance 8. In the above example, the powder was supplied through the inner tube of the lance holder, and gas oxygen was supplied through the outer tube.However, the present invention is not limited to this.
Even if this configuration is reversed, there is no particular problem. It is considered that this point is arbitrarily determined based on the arrangement of the existing pipes and the like.

However, it has been pointed out that, as described above, when powder and gaseous oxygen are mixed and transported, there is a high risk of causing a fire or explosion accident in the piping. For this reason, immersion lances with a double-tube structure have been used in the past.However, the present inventors investigate past accidents and documents in oxygen piping in detail and conduct laboratory-scale experiments. Therefore, if the mixing part of powder and gaseous oxygen is after the lance holder, even if the immersion lance is a single pipe, the risk of pipe fire and explosion accident is the same as when using a double pipe lance It revealed that.

[0010] That is, the starting point of pipe fire and explosion is:
1) A part where the powder violently collides with the pipe wall, such as a bent part of the pipe. 2) When a dead space of the flow is formed in the pipe, flammable iron powder or the like generated at that part by abrasion of the pipe. It was found that the accumulation was caused by 3) the oil and the flammable cleaning agent adhered to the pipe in a large amount, and 4) the flammable gasket was used.

Therefore, if the above four factors are avoided as in the present invention, all problems can be solved even if the immersion lance has a single tube structure. In order to further ensure thoroughness, the conveying system for the powder, including the lance holder structure, should be made as straight as possible, and the material forming the lance holder and the lance should be subjected to some surface hardening treatment. desirable.

Also, the immersion lance 8 of the inner tube 12 of the lance holder.
The length of protrusion into the lance is not specified, but when the lance is exhausted, the lance is immersed to the lowest limit so that the inner tube of the lance does not come into direct contact with the hot metal. What is necessary is just to be located above the bath surface. In addition, the example of the shape of the outer tube of the lance holder was described in which the diameter of the tip was slightly narrowed, but this point is not particularly specified, and the supply rate of the required amount of gaseous oxygen and powder in accordance with the operating conditions. May be arbitrarily designed so as to secure

On the other hand, the length of the inner tube of the lance holder is not specially specified, but the powder and gaseous oxygen supplied separately are rectified downstream by the inner and outer tubes of the lance holder, respectively. You only need to secure a minimum of a sufficient distance. Regarding the shape of the lance holder, an example was shown in which the diameter of the tip was reduced to about the same as the lance diameter, but this point is also not specially specified. May be arbitrarily designed so that

The gaseous oxygen and the powder thus mixed are blown into the hot metal through a single-tube immersion lance. As described above, when gaseous oxygen is blown with a conventional single-tube lance, It has been said that the erosion of steel is not industrially feasible. However, the present inventors meanwhile, the heat of decomposition of solid oxygen and the increase in sensible heat of the dephosphorizing material such as solid oxygen and quick lime have a cooling effect near the lance outlet,
As a result, we focused on suppressing the melting of the lance. Specific data will be shown later, but the conclusion is that powder consisting of solid oxygen and dephosphorizing agent such as quicklime and gaseous oxygen
If each of the feed rate ratio Qflux / QO ₂ to 6 or more, even in a single tube lance, erosion of the lance until the industrially extent possible satisfied found that can be suppressed.

In the present invention, the case where the lance is immersed obliquely in the hot metal filled in the tope car has been described. However, the container is not limited to the tope car and may be a hot metal pot or the like. It is not limited. Hereinafter, the present invention will be described in more detail based on examples.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the first embodiment, the structure of the apparatus is shown in FIGS.
The second embodiment is basically the same as that shown in FIGS. As a comparative example, an experiment using a double tube lance was also performed. FIG. 7 is a schematic diagram of an apparatus in a comparative example. In this example, the lance holder is a full section double pipe, and a steel pipe of the same diameter is used for the inner pipe of the lance holder.
Steel pipes whose outer surfaces were covered with fire-resistant skin were connected to the outer pipes, respectively, to form a immersion lance for the double pipes in all sections. Here, powder was supplied from the outer tube and gaseous oxygen was supplied from the inner tube according to the conventional technique using the above-described double tube lance.

Table 1 shows the specifications of the lance in Examples and Comparative Examples. The lance diameter and the like of the comparative example were designed so as to obtain the same blowing conditions as those of the apparatus in the example. Table 2 shows standard operating conditions in Examples and Comparative Examples. Table 3 shows a comparison of lance life, lance cost, and lance replacement time when operated under these conditions. In the case of the embodiment, although the lance life is slightly shortened, the cost per lance is low, so the lance cost required for processing is less than half. Further, since the structure is simple and the lance weight is light, the lance replacement operation is easy, and the replacement time is about one time as compared with the comparative example.
It can be seen that で to ５ is enough. FIG. 5 shows the relationship between the desiliconization external dephosphorization oxygen efficiency and the phosphorus concentration in the hot metal in Examples and Comparative Examples.

It can be seen that in the example, the dephosphorization efficiency is improved by about 5% as compared with the comparative example. In general, it is important to coexist a dephosphorizing agent such as quicklime and an oxygen source at a reaction site in order to improve the dephosphorization reaction efficiency. Therefore, in the case of the embodiment, it is considered that the reaction efficiency was improved because the gas was blown in a state where the gaseous oxygen and the powder were sufficiently mixed in the lance holder and the lance.

As described above, the securing of the lance life by the method of the present invention coexists with the heat of decomposition of solid oxygen and the cooling effect near the lance outlet due to the increase in sensible heat of the solid oxygen and the dephosphorizing agent such as quicklime. is there. The inventors of the present invention varied the supply rates of the gaseous oxygen and the powder based on the above-mentioned operating conditions, and investigated the lance erosion state in detail. as a result,
As shown in FIG. 6, it was found that the lance melting rate was well controlled by the ratio of the powder and gaseous oxygen supply rates.

In order for the present invention to be industrially feasible, it is desirable that at least one treatment be performed with one lance. On the other hand, general desiliconization / dephosphorization processing time is 10 ~
Taking into account that the immersion depth of the lance at that time is 1000 to 1500 mm, the melting speed of the lance is 50 mm / min at the maximum.
It is necessary to suppress to the extent. From the relationship shown in FIG. 6, it can be seen that in order to suppress the lance melting speed to 50 mm / min or less, it is better to set the ratio of the supply speed of the powder and gaseous oxygen to 6 or more.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

According to the present invention, a powder comprising a dephosphorizing agent such as solid oxygen and quicklime and gaseous oxygen are independently transported by a lance holder comprising a double tube, and a ratio of the supply speed of the powder to gaseous oxygen is obtained. 6 or more, mixed in a single-tube immersion lance or lance holder, and blown into hot metal from a single-tube immersion lance to perform desiliconization and dephosphorization. The lance can be suppressed from being melted, and the lance cost and the lance replacement work load can be significantly reduced as compared with the case where a conventional double-tube lance is used.

Further, since the mixing of the gaseous oxygen and the powder is good, there is an effect that the dephosphorization reaction efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing one device configuration suitable for implementing the present invention.

FIG. 2 is a sectional view showing one structure of a lance holder suitable for carrying out the present invention.

FIG. 3 is a conceptual diagram showing one device configuration suitable for implementing the present invention.

FIG. 4 is a sectional view showing one structure of a lance holder suitable for carrying out the present invention.

FIG. 5 is a graph showing the relationship between desiliconization dephosphorization oxygen efficiency and phosphorus concentration in hot metal in Examples and Comparative Examples.

FIG. 6 is a graph showing a relationship between a lance melting rate and a ratio of a powder supply rate to a gas oxygen supply rate in the present invention.

FIG. 7 is a conceptual diagram illustrating a device configuration used in a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Powder extraction apparatus 2 Solid oxygen 3 Powder extraction apparatus 4 Dephosphorizer 5 Powder injection pipe 6 Gas oxygen pipe 7 Lance holder 8 Immersion lance 9 Topy car 10 Hot metal 11 Powder introduction pipe 12 Lance holder inner pipe 13 T-tube for introducing gaseous oxygen 14 Lance holder outer tube 15 Lance connection

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-185814 (JP, A) JP-B-62-6608 (JP, B2) Jiko 2-4113 (JP, Y2) (58) Field (Int.Cl. ⁶ , DB name) C21C 1/04 101 C21C 1/02 110 F27D 3/18

Claims (2)

(57) [Claims] An inert gas or air is used to convey and blow a powder comprising a solid oxide containing iron oxide as a main component and a dephosphorizing agent such as quicklime into the hot metal, and simultaneously blows gaseous oxygen to remove the hot metal. When performing silicon and dephosphorization, a single pipe immersion lance is gripped by a lance holder, and the lance holder is formed as a double pipe consisting of an inner pipe and an outer pipe. And the lower end of the inner pipe is opened in the immersion lance of the single pipe, and the powder supply rate Qflux (kg / min) and the gas oxygen supply rate QO ₂ (Nm ³ / min), Qflux /
A method for desiliconizing and dephosphorizing hot metal, wherein QO ₂ is 6 or more, and the powder and the gaseous oxygen are mixed in advance in a dipping lance of the single tube and then blown into the hot metal. 2. A method for removing hot metal by feeding powder containing a solid oxide containing iron oxide as a main component and a dephosphorizing agent such as quick lime into the hot metal with an inert gas or air and simultaneously blowing gaseous oxygen into the hot metal. When performing silicon and dephosphorization, a single pipe immersion lance is gripped by a lance holder, and the lance holder is formed as a double pipe consisting of an inner pipe and an outer pipe. And the lower end of the inner pipe is opened to the lance holder, and the powder supply rate Qflux (kg / min) and the gas oxygen supply rate QO ₂ (Nm ³ / min) Ratio, Qflux / QO ₂
Wherein the powder and the gaseous oxygen are preliminarily mixed in the lance holder and then blown into the hot metal.