JPH0420962B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a hot metal pretreatment method in which a refining material is added to hot metal flowing in a blast furnace gutter to perform preliminary refining. [Conventional technology] In recent years, requirements for steel composition have become stricter (low P.
S. steelmaking), the necessity and importance of pre-treatment of hot metal has increased, and due to the advantages of omitting processes and simple processing, pre-treatment of hot metal by adding refining agents in the blast furnace trough has been actively carried out. I'm starting to be able to do it. Methods for adding refining agents into hot metal can be broadly divided into the overlay method, the injection method, and the blasting method. Among these methods, the injection method using an immersion lance is the most superior in terms of addition and mixing of refining agents. However, considering the running cost due to lance erosion,
Recently, the blasting method, in which a refining agent is injected into the top of the hot metal using a high-speed flow, has come into widespread use, as shown in Japanese Patent Application Laid-Open No. 58-130208. However, this preliminary processing presents a problem that has not existed in the past. In other words, in the conventional steelmaking method that does not perform pretreatment, the slag flowing in the blast furnace gutter has SiO ₂ and CaO as its main components, which acts extremely stably on the gutter refractories, making the gutter refractory It has extended the lifespan of things. However, when pre-treatment of hot metal began to be carried out, components that were extremely harmful to refractories, mainly FeO, were mixed into the produced slag, and corrosion caused by this became a problem. Erosion of the gutter refractory is most severe at the point where the boundary between the hot metal and slag meets, and the molten metal surface changes only slightly due to the flow rate of the hot metal and is almost constant (approximately in the range of 20 to 30 mm), making the life of the gutter even shorter. A mortar was applied to the vehicle. As a solution to this problem, conventional proposals have been to change the material of the gutter refractory to a different type, or to blow protective gas through the side walls of the gutter to direct the slag to the center of the gutter, as seen in Japanese Patent Application Laid-Open No. 57-134505. are doing. [Problem to be solved by the invention] However, in the former case, it is necessary to select the material according to the content of the hot metal pretreatment, and the selection is difficult, and it is difficult to change the material every time the content of the pretreatment changes. This is also difficult from an operational standpoint. In addition, since the quality of the material becomes higher, there is also the problem that the refractory unit cost (refractory cost per amount of hot metal processed) deteriorates. In the latter case, there is a practical problem because the protective gas lowers the temperature of the hot metal and it is difficult to work when turning the gutter. As a result of various studies conducted by the present inventor, the blasting method has disadvantages in that there are many ripples on the surface of the hot metal and severe erosion of the refractory, but these disadvantages are due to the fact that the refining agent penetrates the slag from the top surface of the hot metal. We have discovered that this can be solved by applying a large force to the slag and adjusting the blowing direction, and hereby provide a method for continuous pretreatment of hot metal with improved corrosion resistance. [Means for Solving the Problems] As a result of extensive research, the present invention has developed a continuous pretreatment method for hot metal in which a refining agent is added to a gutter that continuously flows and guides hot metal. They are arranged side by side and the tip of each nozzle is arranged toward the center from the gutter wall side, and the refining agent is blown into the hot metal from the upper surface of the hot metal at high speed through the plurality of nozzles. The multiple nozzles have a second nozzle to reduce splash and apply force to the slag layer toward the center of the gutter.
As shown in Fig. 3 and Fig. 3, an angle of 0°α45°, especially 5°α30° along the hot metal flow direction is preferred, and an angle of 0°<θ< along the cross-sectional direction of the hot metal is preferred.
It is preferable to tilt it at an angle of 4.5°. It is best to adjust the blowing angles α and θ so that the floating point of the blown refining agent is at the center of the gutter, taking into account the flow rate of hot metal.
The upper limit is 45°; if the tilt angle is greater than this, it becomes difficult for the blown refining agent to enter the hot metal, resulting in an increase in splash and a significant drop in refining reaction efficiency. Furthermore, the effect is even greater by arranging the nozzles in a staggered manner. As the carrier gas for the refining material, in addition to an inert gas such as N ₂ , compressed air or a combustion supporting gas such as oxygen can be used. The blowing pressure of the carrier gas cannot be determined unconditionally depending on the depth of the hot metal and the nozzle opening, but it is 1.5 to 6 Kgf/cm ² in order to apply force to the slag layer toward the center of the gutter and to ensure sufficient stirring.
It is desirable to keep it to a certain extent. [Operation] By blowing the refining material, a force is generated in the slag layer toward the center of the gutter, and the slag layer leaves the gutter wall surface and gathers at the center and flows, reducing erosion of the gutter refractories. [Example] Hereinafter, an example will be described with reference to the drawings. FIG. 1 is a schematic diagram of an apparatus used for carrying out the present invention, and in the figure, 1 is a blast furnace gutter constructed of refractory material. Refractories include Al ₂ O ₃ : 80wt%, SiC+C:
15wt% monolithic refractories and other refractories can be used. A skimmer 2 is arranged on the upstream side of the blast furnace gutter 1, and a slag discharge port 1a is provided on the gutter wall surface on the downstream side. Skinmer 2 and slag outlet 1
A plurality of nozzles 4 are arranged on the three surfaces of the hot metal for spraying a refining agent onto the three surfaces of the hot metal in order to perform preliminary refining. The plurality of nozzles 4 are arranged in two rows in the hot metal flow direction (arrow), and the tip of each nozzle 4 is oriented from the wall side of the gutter 1 toward the center. Specifically, the inclination angle of nozzle 4 is α
= 15° and θ = 10°, and the nozzles 4 are arranged in a staggered manner. Note that 5 is a tank in which the refining agent is placed. Using such equipment, 10 tons/min of hot metal was dephosphorized. Refining agent is CaO: 40wt%,
It consists of CaF: 8wt% and mill scale: 50wt%. Using a carrier gas, this refining agent is
It was blown at a pressure of 400Kg/min. Sufficient agitation is achieved by this blowing, and the slag 6
The slag moved away from the wall of the gutter 1 and proceeded from the center, and was discharged from the slag discharge port 1a. In order to compare the effects, gutter refining was carried out under the same conditions and the amount of erosion at the position where the refractory was in contact with the hot metal surface was measured, and the results were obtained as shown in Table 1 below.

〔Effect of the invention〕

As explained above, the present invention has the following effects. Gutter life can be extended. There is little interference with the next stage of blasting, and the refining efficiency is high. Since it can be blown in from near the wall, it can stir the entire cross section of the hot metal flow. The slag layer is thick in the center and thin near the wall, so there is less scattering of the refining agent by the slag layer during injection. Splash can be significantly reduced by adjusting the nozzle angle. No wall protection gas required. These effects become noticeable when applied to dephosphorization treatment that causes severe corrosion of refractories.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the outline of the device used in the present invention, Fig. 2 is a front view of the nozzles arranged along the flow direction of hot metal, and Fig. 3 is a perspective view of the nozzles arranged along the hot metal flow direction. It is a side view of a nozzle. 1...Blast furnace gutter, 1a...Slag discharge port, 2...
Skinmer, 3...Hot metal, 4...Nozzle, 5...
Tank, 6...Slag.

Claims (1)

[Claims] 1. In a hot metal continuous pretreatment method in which a refining agent is added to a gutter that continuously flows and guides hot metal, a plurality of nozzles are lined up in the hot metal flow direction, and the tip of each nozzle is arranged from the gutter wall side toward the center. , a continuous hot metal pretreatment method characterized by injecting a refining agent into the hot metal from the upper surface of the hot metal at high speed through the plurality of nozzles.