JP2000273518A - Pretreatment apparatus for molten iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pretreatment apparatus for molten iron, composed of an immersion lance and a lance holder which are suitable to restrain the running cost and improve the quality of molten iron. SOLUTION: In the pretreatment apparatus of the molten iron composed of the immersion lance 8 and the lance holder 7A formed as a double tube of an inner tube 7a holding this immersion lance 8 and connected with the piping for powder-blowing, blowing the powder into the molten iron and an outer tube connected with the piping for gas-blowing, a screw-connecting part 13 for screw-connected with the immersion lance 8 at the tip part of the outer tube in the lance holder 7A is provided. A heat-insulating cover 14 is arranged so as to cover at least the screw-connecting part 13 at the tip part of the outer tube, and a cooling nozzle 16 for blowing the cooling medium C between the heat insulating cover 14 and the outer tube is disposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot metal pretreatment apparatus.

[0002]

2. Description of the Related Art Conventionally, pretreatment such as desiliconization, dephosphorization or desulfurization is performed on molten metal before charging a converter, and only decarburization is performed after charging the converter to reduce the total cost of the refining process. The process of planning is widespread. In the pre-siliconization, dephosphorization and desulfurization of hot metal, the hot metal filled in a tope car or hot metal pot contains solid oxides mainly composed of iron oxide (hereinafter referred to as solid oxygen) and dephosphorized lime. Many methods have been adopted in which a powder of an agent is blown through a consumable immersion lance.

One of the weak points of this process is that the temperature of the hot metal drops significantly due to the heat of decomposition of solid oxygen and the increase in the sensible heat of solid oxygen and quicklime, which reduces the heat margin in the next step, a converter. That is. Therefore, in recent years, a method of compensating hot metal temperature by blowing part of iron oxide as an oxygen source instead of gaseous oxygen (for example, Japanese Patent No. 2812852) has been adopted.

[0004] A process of preliminary desiliconization, dephosphorization, and desulfurization in which gaseous oxygen and solid oxygen are simultaneously blown will be described with reference to FIG. As schematically shown in FIG. 5, the first
The solid oxygen 2 discharged into the powder cutting device 1 and the dephosphorizing agent 4 mainly composed of quicklime discharged into the second powder cutting device 3 are combined with a powder blowing pipe 5. The inside of the lance holder 7 is conveyed by air or an inert gas (such as nitrogen).
Is supplied to the inner tube 7a. On the other hand, the gaseous oxygen G is supplied to the gap between the outer tube 7b and the inner tube 7a of the lance holder 7 via the gas blowing pipe 6. A single-tube type immersion lance 8 is attached to the tip of the lance holder 7, and the powder and gaseous oxygen separately supplied to the lance holder 7 are mixed while passing through the immersion lance 8, and It is blown into the hot metal 10 filled in the tank.

[0005] To supplement the structure of the conventional lance holder 7 used here, the solid oxygen 2 conveyed through the powder injection pipe 5 by air or nitrogen as shown in an enlarged cross section in FIG. The powder comprising the phosphor and the dephosphorizer 4 is supplied from a powder introduction pipe 11 to a lance holder 7 connected thereto.
Is supplied to the inner tube 7a. The gaseous oxygen is T
It is supplied from the U-shaped tube 12 through the gap between the inner tube 7a and the outer tube 7b. The screw connection 13 between the outer tube 7b and the immersion lance 8
Are connected by a screw connection between a tapered female screw provided on the inner surface of the end of the outer tube 7b and a tapered male screw provided on the outer surface of the end of the immersion lance 8.

[0006]

When powder and gaseous oxygen are simultaneously blown into the hot metal using the lance holder 7 having the above-described structure, the gaseous oxygen reacts with various components in the hot metal. The heat of oxidation reaction generated at this time is extremely large, and the forming of the high-temperature generated gas causes seizure on the tapered thread portion of the screw connection portion 13 so that it becomes impossible to remove the immersion lance 8 from the outer tube 7b, or There is a disadvantage that the lance 8 comes off from the lance holder 7.

In order to solve this problem, it is conceivable to keep the screw connection 13 away from the hot metal bath surface, which is a heat source, by a predetermined distance. However, if the length of the immersion lance 8 is increased, the running cost increases. This is undesirable. Although it is conceivable to reduce the immersion depth of the immersion lance 8, the stirring energy in the hot metal decreases, the reaction efficiency decreases, and another major problem of impairing the quality of the hot metal occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and is a pretreatment of hot metal suitable for simultaneously satisfying both running cost and hot metal quality. It is intended to provide a device.

[0009]

According to the present invention, there is provided a double immersion lance, comprising an inner pipe connected to a powder injection pipe holding the immersion lance and an outer pipe connected to a gas injection pipe. A hot metal pretreatment device for blowing powder into a hot metal, comprising a lance holder serving as a tube, wherein a screw connection portion for screw-connecting the immersion lance is provided at a tip of the outer tube, and at least the external A pretreatment apparatus for hot metal, wherein a heat insulating cover is provided at a screw connection portion at a tip end of a pipe, and a cooling nozzle for blowing a cooling medium into a gap between the heat insulating cover and the outer pipe is provided.

Further, in the present invention, it is preferable that a plurality of holes are provided on an end face of the heat insulating cover, and that air or a mixture of water and air is used as the cooling medium.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a side view showing one embodiment of the structure of the lance holder of the present invention.
FIG. 2 is a view taken in the direction of arrows AA in FIG. FIG. 3 shows another embodiment of the lance holder of the present invention. The same members as those in the conventional example are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIGS. 1 and 2, the lance holder 7A of the present invention is provided with a cylindrical heat insulating cover 14 so as to cover the outer surface of the outer tube 7b. The size of the inner diameter of the heat insulating cover 14 is slightly larger than the value of the outer diameter of the outer tube 7b. At one end 14a of the heat-insulating cover 14, a lid 15 for sealing the end is provided. A hole 15a through which the tip of the lance 8 can penetrate is provided at the center of the lid 15, and the inner surface of the hole 15a is fixed to the end face 7c of the tip of the outer tube 7b by, for example, spot welding. Is done. Note that, instead of the lid part 15, the end part 14 of the heat insulating cover 14
You may make it draw-process to a.

A cooling nozzle 16 for blowing air or a cooling medium C of water and air is provided on the outer surface of the heat insulating cover 14. The outlet 16a of the cooling nozzle 16 is a heat insulating cover
The cover 15 is mounted so that it is located substantially at the center of the gap S formed by the inner surface of the outer tube 7 and the outer surface of the outer tube 7b, and the direction of the blowout is directed to the inner surface of the lid 15. With this configuration, if the cooling medium C is blown from the cooling nozzle 16, the surface of the screw connection portion 13 between the outer tube 7b and the immersion lance 8 can be cooled. Even if the depth is set to the same level as that of the conventional example, it is possible to suppress the occurrence of the seizure trouble in the screw connection portion 13 formed by the tapered screw.

Next, another embodiment of the present invention will be described. As shown in FIG. 3, a plurality of holes 17 are provided in a lid portion 15 of a heat insulating cover 14, and a cooling medium C is formed through the holes 17 through the holes 17. We let some blow out. Then, since the bath surface of the hot metal near the immersion of the immersion lance 8 can be cooled by the cooling medium C, the immersion lance 8 can be further immersed further. Thereby, the stirring energy can be increased, so that the reaction efficiency can be further improved.

[0015]

Embodiment 1 Using the lance holder 7A of the present invention shown in FIG. 1, the screw connection portion 13 was cooled using only air as the cooling medium C. As a result, the life of the lance holder was 15.0 charges / piece in the conventional example, but could be more than doubled to 32.9 charges / piece.

Example 2 Similarly, when a mixture of water and air was used for the cooling medium C, the life of the lance holder was
43.6 charges / book, a drastic improvement of about 3 times compared to the conventional example. Example 3 Using the lance holder 7A of the present invention having the hole portion 17 in the lid portion 15 shown in FIG. 2 described above, the screw connection portion 13 was cooled with a mixture of water and air as its cooling medium C. Then, a part of the mixture of water and air was blown out from the holes 17 to suppress the occurrence of forming on the hot metal bath surface. At this time, eight holes 17 having a size of 20 mmφ were provided symmetrically in the circumferential direction, and a mixture of water and air was jetted at about 500 l / min. The immersion depth of the immersion lance 8 was 1500 mm (usually 1000 mm in the conventional example). As a result, the life of the lance holder is extended about three times as compared with the conventional example, and the desulfurization reaction efficiency using soda ash is higher than that of the conventional example as shown in FIG.
A 22% improvement was achieved.

[0017]

As described above, according to the present invention,
It is possible to extend the life of the lance holder more than twice by attaching a heat-insulating cover so as to cover the screw part at the tip of the lance holder and cooling the screw connection part of the taper screw with air or water and a cooling medium of air. As a result, it is possible to reduce running costs. In addition, by injecting a part of the cooling medium to the hot metal bath surface, the immersion lance can be immersed further deeply, so that the reaction efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a side view showing one embodiment of the structure of a lance holder of the present invention.

FIG. 2 is a view as viewed in the direction of arrows AA in FIG. 1;

FIG. 3 shows another embodiment of the lance holder of the present invention.

FIG. 4 is a characteristic diagram showing desulfurization reaction efficiency.

FIG. 5 is a schematic diagram schematically showing a conventional example of a process of preliminary desiliconization, dephosphorization, and desulfurization.

FIG. 6 is a side sectional view showing a conventional example of a lance holder.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first powder extracting device 2 solid oxygen 3 second powder extracting device 4 dephosphorizer 5 powder blowing pipe 6 gas blowing pipe 7 conventional lance holder 7A lance holder 7a of the present invention inner pipe 7b Outer tube 7c End face 8 Immersion lance 9 Topped car 10 Hot metal 11 Powder introduction tube 12 T-shaped tube 13 Screw connection 14 Heat insulation cover 14a One end of heat insulation cover 15 Lid 15a Hole 16 Cooling nozzle 16a Outlet 17 Hole C Cooling medium G Gas oxygen S Gap between heat shield cover and outer tube

Claims (3)

[Claims] 1. An immersion lance, and a lance holder which is a double tube of an inner tube connected to a powder injection pipe and holding an immersion lance and an outer pipe connected to a gas injection pipe. A pretreatment device for hot metal that blows powder into hot metal, comprising a screw connection portion for screw-connecting the immersion lance at a tip of the outer tube, and at least a screw connection portion at a tip of the outer tube. A pretreatment apparatus for hot metal, comprising: a heat insulating cover; and a cooling nozzle for blowing a cooling medium into a gap between the heat insulating cover and the outer tube. 2. The hot metal pretreatment apparatus according to claim 1, wherein a plurality of holes are provided on an end face of the heat insulating cover. 3. The hot metal pretreatment apparatus according to claim 1, wherein air or a mixture of water and air is used as the cooling medium.