JPS6242009B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a molten iron gutter refining method, and in particular to suppressing erosion of the lower surface of the molten iron gutter caused by the injection injection method of refining agents, reducing the frequency of repair, and improving the refining agent injection lance. It concerns technology that aims to extend lifespan. Although this specification mainly describes a method for continuously desiliconizing molten pig iron tapped from a blast furnace on a cast bed, the present invention is of course not limited to this method. It can be similarly applied to various treatment methods such as continuous dephosphorization or desulfurization during passing. [Prior art] As a relatively new desiliconization method that replaces the ladle desiliconization method, a desiliconization agent is added to the hot metal that is tapped from the blast furnace and flows through the tap hole of the casthouse, and the desiliconization is done before it is received into the ladle. The hot metal sluice desiliconization method, which completes the treatment, is becoming popular. That is, this method includes a method in which a desiliconizing agent is introduced into hot metal flowing through a hot metal gutter, and the desiliconizing agent is drawn into the hot metal using the stirring effect produced by the flow of hot metal to perform desiliconization. Considering that the stirring entrainment effect is weak, an injection lance is inserted into the hot metal flowing through the hot metal culvert, and a granular desiliconizing agent is injected from the lance together with a carrier gas to promote the reaction between the hot metal and the desiliconizing agent. method, and the above-mentioned method has problems as described below, so in order to prevent corrosion of the lance, a granular desiliconizing agent is sprayed together with a carrier gas, and the hot metal flow and the stirring force generated by the spraying are used. Increases contact efficiency between desiliconizing agent and hot metal,
Methods for improving the desiliconization efficiency are known, and all of them are prized as extremely efficient methods because they allow desiliconization to proceed while the hot metal flows down the gutter. In particular, it is thought that a high level of desiliconization efficiency is achieved because the bubbling caused by gas injection from the lance and the agitation caused by the turbulent flow of the hot metal combine to increase the agitation efficiency. ing. [Problems to be solved by the invention] However, the above method is not completely free of problems, and there are still various problems that need to be improved, such as the following, and these problems can be solved by refining (dephosphorization, This can be said to be a common drawback when performing desulfurization, etc.). a○ The desiliconizing agent is blown downward along with the carrier gas from the nozzle opened at the leading edge of the lance.
Since the lower surface of the hot metal gutter is locally eroded by this blowing flow, the life of the hot metal gutter is significantly shortened. b○ Since the desiliconizing agent injection lance hangs down from above the hot metal surface and part of its tip is immersed in the hot metal, the immersed part, especially near the slag line, is subject to considerable wear due to the erosion of the produced slag. . Moreover, the lance is only cantilevered upward.
Not only does it vibrate significantly due to the rapid flow of high-mass hot metal (specific gravity: approx. 6.7, flow rate: approx. 80 cm/sec), but it also receives an impact reaction (hereinafter simply referred to as shock) during the injection of desiliconizing agent. Minute cracks are likely to occur in the lance itself. When such a crack occurs, hot metal or slag enters into the crack and corrosion is significantly accelerated, resulting in the lance tip being destroyed in a short period of time. c○ Erosion that occurs near the slag line where the desiliconizing agent is injected rapidly progresses not only on the lance but also on the side walls of the hot metal runner, and is another cause of shortening the life of the hot metal runner. d○ The bubbling that accompanies injection extraction causes hot metal to scatter from the hot metal surface to the outside of the gutter, which is extremely dangerous and also leads to loss of hot metal. Against this background, the above-mentioned method has been developed, but in the method, hot metal scatters violently, and measures such as reducing the blasting speed are required from the viewpoint of scattering prevention, so it is less practical. The situation is that we have no choice but to go back to the old method.
When implementing the method, the erosion of the molten iron gutter shown as a○ above should be suppressed as much as possible,
Another important issue is to suppress the wear and tear of the refining agent injection lance, also shown as b○, and extend its life. Regarding the drawbacks mentioned in c○ and d○, we have carried out improvement research from different viewpoints and have filed a separate patent application. [Means for Solving the Problems] The molten iron gutter refining method of the present invention, which can solve the above problems, is based on the molten iron gutter refining method using the most advanced surface of the smelting agent injection lance, which has a sideways jetting nozzle opened near the tip. The gist is that the refining agent is injected into the molten iron flowing in the molten iron gutter together with a carrier gas by contacting the lower surface of the gutter. [Function] The basic structure of the molten iron gutter refining method according to the present invention is based on the so-called desiliconization agent injection method shown above. We have added innovations to the structure and installation method of the included lance (hereinafter simply referred to as the lance). That is, as will be made clear in the examples below, in the present invention,
The nozzle that opens at the tip of the lance is formed horizontally, and the tip of the lance is pressed and fixed against the lower surface of the molten iron gutter. With this configuration, the following effects are achieved. be done. (a) Since the refining agent is injected sideways from the tip of the lance, there is no fear that the lower surface of the molten iron gutter will be locally eroded, and the life of the molten iron gutter can be extended. By the way, it is extremely difficult to locally repair the molten iron gutter formed in the blast furnace casthouse due to constraints on the construction work, and even if the lower surface is partially damaged, the front end of the molten iron gutter must be constructed. , Local damage to the bottom surface must be considered the same as damage to the entire molten iron gutter, so by suppressing local erosion, the overall life can be significantly extended. (b) By pressing and fixing the tip of the lance against the lower surface of the molten iron gutter, the vibration of the lance is drastically reduced, and the occurrence of cracks at the tip of the lance is greatly suppressed. As explained above, in the refining agent injection method, the tip of the lance is immersed in hot metal and the refining agent is injected, so it is impossible to avoid erosion and deterioration of the immersed part. However, if a crack occurs in the refractory at the tip of the lance due to the collision of the hot metal flow or the impact from the shot of the refining agent, the molten metal will penetrate into the crack and corrosion will be accelerated significantly, causing the refractory to deteriorate. It will collapse in a short time. However, if the tip of the lance is pressed and fixed against the bottom surface of the molten iron gutter as described above, even if the lance receives an impact like the one described above, the lance will not vibrate and cracks will be prevented, and the refractory will wear and tear can be significantly suppressed. [Example] Hereinafter, the structure and operation and effect of the present invention will be further clarified with reference to the drawings of the example, mainly focusing on the hot metal trough desiliconization method. FIG. 1 is a schematic explanatory diagram showing an embodiment of the present invention, FIG. 1A is a schematic plan view, FIG. 1B is a schematic vertical sectional view, and FIG. 1C is a schematic cross-sectional view. 1 is the hot metal sluice, 2 is the lance, M is the hot metal, S is the slag, F is the desiliconizing agent, C is the carrier gas, and the arrows indicate the flow of the hot metal. As is clear from these figures, in the present invention, in addition to opening the desiliconization agent injection nozzle 2a sideways at the tip of the lance 2, the tip of the lance 2 is pressed against the bottom of the hot metal trough 1 and fixed. However, together with the supporting effect of the lance support device (not shown in the drawing) located above the lance 1, the lance 1 is held in a state where it is held on both sides and is fixed so that it does not move.In this state, the nozzle A desiliconizing agent is blown into the hot metal M together with the carrier gas C from 2a. Note that the pressing and fixing of the tip of the lance 2 to the bottom surface of the molten pig iron trough 1 may be an engagement or fitting fixation using unevenness or a step.
Normally, the lance 1 can be sufficiently fixed simply by using its own weight (usually about 400 to 500 kg) and placing it on the bottom of the gutter. Furthermore, it is more reliable if a descending force is added by an elevating device. When such a configuration is adopted, a horizontal nozzle 2a is opened at the tip of the lance 1, and the desiliconizing agent F is opened.
Since the carrier gas C is blown sideways from this nozzle 2a, there is no fear that at least the bottom surface of the hot metal trough 1 will be locally eroded, and the life of the molten metal trough 1 can be extended. By the way, in conventional hot metal trough desiliconization using the desiliconizing agent injection method, the nozzle 2a is
is opened downward, and the desiliconizing agent F and carrier gas C are blown toward the bottom at high speed, so the refractory facing the nozzle 2a rapidly undergoes local erosion, as shown in the figure, and within a short period of time was forced to rebuild. However, in the present invention, as mentioned above, local erosion of the bottom surface of the gutter does not occur, so the life of the entire hot metal gutter 1 can be significantly extended, and the frequency of rebuilding can be drastically reduced. Moreover, in the conventional hot metal trough desiliconization method as shown in Figure 2, the lance 2 is suspended into the hot metal in a so-called "mid-hanging" state, so as mentioned above, the hot metal with high specific gravity and high speed is constantly flowing. The lance that receives it vibrates violently,
Combined with the impact caused by the injection of the desiliconizing agent and carrier gas, the vibration becomes even more intense.
For this reason, cracks are likely to occur in the refractory material at the tip of the lance 2, and once a crack occurs, the process of pouring hot water into the crack, erosion, and collapse progresses rapidly as described above, and the refractory becomes unusable in a short period of time. In contrast, in the present invention, as shown in FIGS. 1A and 1B, the lower surface of the lance 2 is pressed against and fixed to the bottom surface of the hot metal trough 1, and the upper surface is of course supported by a support device. , the above-mentioned "mid-center" condition is eliminated, and the lance 2 does not vibrate even when subjected to collisions of hot metal flow, injection shocks of carrier gas, etc., and therefore, the occurrence of cracks seen in tip refractories is drastically reduced. As a result, the progress of accelerated erosion and collapse as in the conventional example is avoided, and the life of the lance 2 can be significantly extended. In addition, it has been confirmed that the desiliconization efficiency itself is considerably improved by employing the method of the present invention, and the reason for this can be considered as follows. That is, in the conventional example, the hot metal M to be treated flows through the gaps on both sides and the lower part of the lance 2, and comes into contact with the desiliconization agent blown from the lance 2 mainly on the downstream side of the lance 2 to undergo the desiliconization treatment. However, it is extremely difficult to prevent some of the hot metal from flowing out without reacting with the desiliconizing agent. However, in the present invention, all of the hot metal M flows down through both sides of the lance 2, and since the desiliconizing agent F is sufficiently supplied to this part, the untreated hot metal flows through the lance 2. It is considered that the amount decreases and the desiliconization efficiency improves as a result. By the way, we conducted a comparison experiment between the conventional desiliconization method using a single-hole lance and the in-jet extension method, and the desiliconization method of the present invention, which was carried out by pressing and fixing a side-blowing four-hole lance to the bottom of a hot metal trough. , the results shown in Table 1 were obtained.

【table】

[Table] However, the amount of gutter bottom erosion, lance life, and desiliconization efficiency were determined as follows. Amount of gutter bottom erosion: Amount of gutter refractory used (KG) / Amount of desiliconized hot metal (tons) Lance life: Amount of refractory used for lance (KG) / Amount of desiliconized hot metal (tons) Desiliconization oxygen efficiency: Amount of oxygen used in the desiliconization reaction (KG)/Amount of effective oxygen in the desiliconization agent (KG) x 100 (%) As is clear from the above results, if the method of the present invention is adopted, the bottom surface of the hot metal gutter Not only can corrosion be greatly reduced, but also the life of the lance can be greatly extended, and the desiliconization efficiency can also be considerably increased. Although the description above has focused on desiliconization of hot metal gutter, the unique features of the present invention as described above can be similarly exhibited in cases where hot metal or molten steel is dephosphorized or desulfurized on the gutter. It can be widely applied as a continuous refining method for molten iron. There are no restrictions on the number or size of the nozzles formed at the tip of the lance, as long as they are oriented laterally. Of course, it may be a type with 5 or more holes, but from the viewpoint of ensuring the strength of the tip of the lance, a type with 4 holes or less is preferable, and 5 holes or more. In such a case, it is preferable to form them at different positions in the height direction, as shown in FIG. 3, for example. Furthermore, the direction of these nozzles is not limited at all; for example, as shown in FIGS. 4A and 4B, the nozzles may be oriented perpendicularly or parallel to the wall surface of the hot metal gutter 1, or as shown in FIG. 5, they may be oriented obliquely to the wall surface. A directing method, or a combination of these methods as shown in FIG. 6 can be adopted. It may also be formed somewhat upwardly or downwardly, and in order to prevent the hot metal from scattering, which is sometimes seen in conventional injection extraction methods, the upper part of the hot metal gutter 1 at the lance immersion position can be widened, for example, as shown in Figure 7. It is also effective to form [Effects of the Invention] The present invention is configured as described above, and it not only prevents local erosion of the bottom of the molten iron gutter and significantly extends its life, but also significantly suppresses erosion and collapse of the tip of the lance. In addition to these benefits in terms of equipment, it is also possible to increase refining efficiency such as desiliconization efficiency, and in turn, it is possible to reduce the consumption of refining agents.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram showing a conventional example, Fig. 3 is a partial sketch showing another example of the lance, and Figs. FIG. 7 is a plan view showing a preferred example of a molten iron gutter. 1... Molten iron (pig) gutter, 2... Lance, 2a... Nozzle, M... Molten iron (pig) gutter, S... Slag, F... Refining agent (silicification agent), C... Carrier gas.

Claims (1)

[Claims] 1. A molten iron characterized in that the most advanced surface of a refining agent injection lance, which has a sideways jetting nozzle opened from near the tip, is brought into contact with the lower surface of a molten iron gutter, and the refining agent is injected together with a carrier gas into the molten iron flowing in the molten iron gutter. Gutter smelting method.