JPS6335735A - Treating method for molten iron - Google Patents

Abstract

PURPOSE:To eliminate the trouble of molten metal overflow as controlling the height of hold-up to the low level and to give sufficient stirring force by bottom-blowing bubbling gas toward depression part formed on the molten surface at the time of injection treatment. CONSTITUTION:The injection lance 2 is inserted into the molten iron Me in a treating vessel 1 and the injection is executed at degree which carrier gas is floated up. Then, the bubbling gas is blown from the bottom blowing nozzle 3 toward the depression part formed on the molten surface corresponding to the hold-up height H, so as to equal the ascending height at the depression part in the molten surface with the descending hold-up height H. By this treatment, the molten surface of treated molten iron is held almost equally with the molten surface when still, and the molten metal overflow and scattering of the molten metal caused by splash are restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for treating molten iron. Specifically, an injection lance is inserted into molten iron in a molten iron processing container, and a treatment agent is blown into the molten iron using a carrier gas. During treatment, it suppresses the rise of the hot metal surface (hereinafter sometimes referred to as "hold up") that forms at the position where the bubbled carrier gas rises to the surface of the molten iron, eliminating problems such as hot water spilling. It's about how to do it.

[Prior art] In preliminary treatment for the purpose of desiliconization, dephosphorization, desulfurization, etc. of hot metal, an injection lance is plunged into the hot metal in a preliminary m burial furnace, and powdery desiliconization (dephosphorization or desulfurization) flux is injected into the hot metal. A method has been widely put into practical use in which flux is blown into the hot metal using a carrier gas, and the bubbling stirring effect of the carrier gas is utilized to increase the contact efficiency between the hot metal and the flux, thereby improving the pretreatment efficiency. In addition, when adding alloying components to molten iron that has undergone preliminary treatment or molten steel that has been subjected to converter blowing, an injection lance is inserted into the molten iron or molten steel to inject powdered alloy components into the carrier gas. The dispersion of alloy components may be promoted by utilizing the bubbling stirring effect.

In this method of treating molten iron (hereinafter referred to as molten pig iron and molten steel before and after pretreatment), the injected treatment agent is diffused or mixed into the molten iron using the bubbling agitation effect caused by the floating of carrier gas. The above-mentioned process can be accelerated by, for example, a conveying process using a ladle for removing molten iron, a pig iron mixer truck, etc., so it has the potential to be put into practical use more widely.

[Problems to be Solved by the Invention] When carrying out the above-described injection method, in order to enhance the stirring effect due to carrier gas floating, it is necessary to increase the gas flow rate or to plunge the lance into the injection depth. One possibility is to increase the depth.

However, if such a means is adopted, as shown in FIG.
As shown in FIG. 1 (G indicates a carrier gas and S indicates a treatment agent), the height h of the hold up H formed at the floating position of the carrier gas G on the surface of the molten iron becomes large, creating a risk of hot water spilling. In particular, when the freeboard F (the length from the molten metal level at settling to the top opening of the container) is reduced from the viewpoint of improving transportation efficiency or suppressing the temperature drop of molten iron,
The above-mentioned risk of overflowing will become even greater. Therefore, in order to prevent such problems, conventionally, hold up H
Safety is ensured by keeping the amount of carrier gas to a small level so that the amount of injection does not become too large, or by keeping the injection depth shallow. As a result, it becomes impossible to sufficiently enhance the stirring effect of the carrier gas, leading to problems such as prolongation of processing time, which reduces productivity, or the temperature of molten iron falling below standard values, which hinders subsequent processing. was there.

The present invention was made in consideration of the above-mentioned problems, and its purpose is to suppress the height h of the hold-up H caused by the floating of carrier gas to a low level, and to solve the problem of overflowing. The present invention aims to provide a method that can enhance the treatment effect by imparting sufficient stirring power to molten iron.

[Means for Solving the Problems] The structure of the treatment method according to the present invention is such that an injection lance is plunged into molten iron in a molten iron treatment container, and the molten iron is treated while blowing a treatment agent with a carrier gas. The gist is that the gas is blown so as to float the bubbling stirring gas towards the valleys of the molten metal surface formed by the fluctuation of the molten metal surface as a result of the blowing.

[Function] In the present invention, as shown in FIG. 3, in order to eliminate or suppress the hold-up H of the molten metal surface caused by the lifting force when the carrier gas used for blowing the treatment agent floats in the molten iron, Gas bubbling is also carried out in parallel so that a separate bubbling gas floats toward the valley formed on the hot water surface in response to the hold-up H (shown in the box in FIG. 3). 1st
．． FIG. 2 illustrates the situation, with FIG. 1 showing a schematic vertical sectional view and FIG. 2 showing a schematic plan view.

That is, on the ward side, there are four bottom blowing nozzles 3.3 at the bottom of the furnace.・
Using a molten iron processing container 1 equipped with..., an injection lance 2 is plunged into the molten iron Me in the processing container 1, and injection is performed so that the carrier gas floats toward the approximate center of the container 1. Then, as explained in FIG. 3, a hold up H appears approximately at the center of the hot water surface.In the present invention, in order to avoid an abnormal rise in the hold up H and the resulting problem of hot water spilling, the hold up H appears. Another gas bubbling is performed in parallel so that another bubbling gas floats toward the valley formed on the hot water surface in response to H. That is, in this example, assuming that a hold up H appears at approximately the center of the container 1 during the processing process and that the inner circumferential wall side of the container 1 becomes a valley, a 4-inch hole is formed at the bottom so that the opening is located directly below the valley. Bottom-blowing nozzles 3.3. ... are provided, and these nozzles 3.3. ...bubbling gas is blown in. As a result, the valley portion of the hot water level rises due to the lifting force generated by the upward flow of the bubbling gas, while the holdup H conversely falls by the amount of rise in the valley.

Therefore, if the amount and flow rate of the bubbling gas are adjusted appropriately so that the amount of rise in the molten metal level valley due to gas bubbling is equal to the amount of fall in the hold up H, the molten metal level of the treated molten iron can be adjusted to the same level as the molten metal level when it is settled. It is possible to maintain almost the same amount of water, and it is possible to significantly reduce the amount of water spilled over water. In the south,
An example has been shown in which four bottom blowing nozzles 3.3, .
．． The number and arrangement position of ... are not limited to those shown in the drawings, but may be changed as appropriate within the scope of conforming to the purpose of the present invention, which is to "evenly raise the valley formed in the hot water level." It can be implemented.

Also, in Figure 1.2, bottom blowing nozzle 3.3. Although an example of blowing bubbling gas from ... has been shown, for example, as shown in FIG. It is also possible to insert a bubbling-specific lance 4 into the center and blow inert gas from the lance 4 toward the valleys of the hot water surface so that the bubbling gas BG floats up. On the Sho-ku side, an example was shown in which four nozzles were installed in the radial direction at the tip of the lance 4, and bubbling gas was floated at four locations, but it is also possible to install two, three, or five or more nozzles to bubble in the valley position. It is also possible to levitate the gas.

As mentioned above, there are two methods for blowing bubbling gas: ■ using a bottom blowing nozzle and ■ using a bubbling-specific lance. In the latter case, multiple lance lifting devices and ancillary equipment (gas It is more practical to use a porous bottom-blowing nozzle when processing in a transport pan, as this increases the burden on equipment and tends to reduce maintenance efficiency. You can say that the method is to use a plug.

[Example] As shown in Fig. 1.2, 90 tons of hot metal was charged into a hot metal transfer ladle equipped with four bottom-blown porous plugs at equal intervals on the bottom periphery, and injection into the hot metal was carried out. A lance was inserted into the flask, and powdered desulfurization flux (100% Na2co) was blown into the flask using nitrogen as a carrier gas. The lance position was adjusted so that the floating position of the carrier gas was at the center of the furnace. In parallel with this, nitrogen gas was bottom blown from four bottom blown porous plugs to provide hold up force even in the valleys and to suppress the concentrated hold up height at the center of the hot water surface as a whole.

For comparison, a desulfurization experiment was conducted in the same manner as above except that the injection of bottom blowing gas was omitted.

Details of the above experimental conditions and experimental results are summarized in Table 1.

As is clear from Table 1, in the comparative method, the hold-up of the hot water surface was high and there was considerable loss due to hot water spilling outside the furnace and splashing, and as a result, the Fe content was 2.2%.
In contrast, when the method of the present invention is adopted, the hold-up is significantly lower, and the Fe loss due to hot water spills and splashes is suppressed to less than half (0.9%) of the comparative method. Moreover, in the method of the present invention, in addition to the stirring by the carrier gas, the bubbling stirring effect of the bottom-blown gas is added, so that the stirring of the bath is promoted and the desulfurization efficiency is also improved.

[Effects of the Invention] The present invention is configured as described above, and the following effects can be obtained.

(1) Since the hold-up of the hot water surface can be lowered, the scattering of molten iron due to dryness spills and splashes is suppressed, preventing danger and environmental pollution.Furthermore, it prevents a decrease in Fe loss and improves yield. can contribute to the improvement of

(2) The stirring power of the bubbling gas blown in to suppress hold-up increases the stirring efficiency in the bath, making it possible to improve the molten iron processing efficiency or shorten the processing time.

[Brief explanation of the drawing]

Fig. 1.2 shows an embodiment of the present invention, Fig. 1 is a schematic longitudinal sectional view, Fig. 2 is a schematic plan view, Fig. 3 is a schematic longitudinal sectional view showing a conventional method, and Fig. 4.5 The drawings show another embodiment of the present invention, with FIG. 4 being a schematic vertical sectional view and FIG. 5 being a schematic plan view. 1: Processing container 2: Injection lance 3: Bottom blowing nozzle 4: Gas bubbling lance H two-hold up F: Free board Figure 1 Figure 4

Claims (1)

[Claims] When processing the molten iron by inserting the injection lance into the molten iron in the molten iron processing container and blowing the processing agent with the carrier gas, the valleys in the molten metal surface formed by the fluctuation of the molten metal surface due to the injection described above are A method for processing molten iron characterized by blowing gas so as to float a bubbling stirring gas toward the surface.