KR100832978B1 - Method of BOF Operation for Removal of Skull Attached at Oxygen Blowing Lance - Google Patents

Abstract

The present invention relates to a current removal method attached to a converter transmission lance, the object of which is to induce the foaming of slag during the converter operation, the lance surface / now / slag coating layer by coating the slag on the current surface attached to the lance It is to provide a method of generating a crack at the moment due to the difference in thermal expansion and removing the current by the self load.

The present invention for achieving the above object, in the converter operation method for performing the blowing while sending oxygen to the molten iron charged into the converter,

Increasing the flow rate and raising the lance height so that the slag forming in the furnace is induced during the drilling;

In the process of induction of slag forming, if there are signs of slopeing, reducing the flow rate and lowering the lance height to coat the slag on the current surface attached to the lance for removal of the current attached to the lance. The technical point shall be about the method of converter operation.

Lance Height, Songshan Flow, Slope, Slag Forming, Subsidiary Materials, Goods, Now

Description

Method of BOF Operation for Removal of Skull Attached at Oxygen Blowing Lance}

1 is a structural diagram of a typical converter.

Figure 2 is a schematic diagram showing the furnace phenomenon that changes according to the rise of the transmission rate and lance height in accordance with the present invention.

Figure 3 is a schematic diagram for explaining the lance now removing method of the present invention.

4 is an example of a converter operation pattern of the prior art and the present invention.

Explanation of symbols on the main parts of the drawings

1 ..... Converter 2 ..... Lance 3 ..... Nogu

4 ..... skirt 5 ..... slag 6 ..... molten iron

The present invention relates to a current removal method attached to a converter transmission lance, and more particularly, lance surface / now / slag coating layer by actively inducing the forming during the converter operation to coat the slag on the current surface attached to the lance The present invention relates to a method of removing a current by causing a crack in the current interface due to a difference in thermal expansion therebetween.                         

In general, converter operation uses molten iron and scrap metal as main raw materials to inject oxygen through the lance 2 and decarburize the charged molten iron on the basis of a constant blowing pattern (lance height and delivery flow control) as shown in FIG. 1. . The converter refining operation through the drilling, there is a problem due to the control of many operating factors, the most common phenomenon is that sputtering (spitting) of the molten iron particles by the Songsan jet during the drilling occurs. As a result of this spitting phenomenon, the molten iron particles stick and grow on the surface of the lance and grow to adhere to the lance in a large size.

The lancet attachment tends to occur more frequently when the raw material is defective, or when the manganese and silicon in the molten iron are low or the molten iron temperature is low. In other words, the general charterer, silicon and manganese may be lower than 0.25% by weight, depending on the blast furnace operation, but usually contains 0.25 to 0.45% by weight of silicon and manganese. On the other hand, the delineated molten iron which has been oxidized in the pretreatment process is less than 0.15% by weight of silicon and manganese, respectively, so that it is difficult for the raw material to be injected during the drilling process, and the molten iron particles are likely to splash and adhere to the lance.

In the field operation, the main cause of the current attachment to the lance is inferior goods, and the large amount of fluorspar, which is advantageous for the goods, is injected, the songsan lance is increased or the flow rate is lowered to facilitate the goods of the slag during the drilling. Used to relax the attachment. However, this method could not be a fundamental countermeasure because the ability to cope varies depending on the worker because there is no standard of operation. In particular, when conducting the converter operation by using a low-lining vessel of manganese and silicon, the adhesion phenomenon is more serious now.

Therefore, the present inventors have disclosed a technique for significantly reducing the occurrence rate of spitting by increasing the lance height and reducing the flow rate when there is a spitting occurrence in the furnace during the conversion of the Korean patent application No. 2000-79940 (converting operation for preventing spitting). Method). This technique is a technique that can suppress the attachment to the lance as much as possible, and is not a technique that can directly remove the present when it is attached by continuous repeated use of the lance.

As a technique for removing the current attached to the lance in operation, there is a Korean Patent Publication No. 1995-14322. This technology installs a number of nozzles in the upper lance dome of the lance body which rises after the completion of the blowing process, and sprays the coolant through the nozzles, causing the cracks to be attached to the lance by rapid cooling so that they are now eliminated by their own weight. It is. This technology has the advantage of being able to remove the lance now during operation, so that the lance can be used continuously and repeatedly, but the installation is complicated and costly, such as installing a separate cooling nozzle on the upper lance dome.

The present invention has been proposed to solve such a conventional problem, in the case of continuously using the lance repeatedly to remove the current of the lance, actively inducing the slag forming during the blowing process, the slag is now attached to the lance The present invention relates to a converter refining method in which a crack is generated by the thermal expansion difference of the lance surface / now / slag coating layer by coating, and the present can be removed efficiently by the self-weighting process.

Converter operation method of the present invention for achieving the above object,

In the converter operation method for performing the blowing while sending oxygen through the lance to the molten iron charged in the converter, the step of increasing the flow rate and raising the lance height to induce slag forming in the furnace during the drilling,

In the process of inducing the slag forming, if there is a sign of the slope, it comprises a step of coating the slag on the surface now attached to the lance while reducing the flow rate and lowering the lance height.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

When the present inventors coat the slag on the now attached to the lance, the tensile stress acts on the now surface layer of the now and the slag interface by thermal slack, and the compressive stress is applied to the lance surface and the now layer of the now surface to be fused to the lance. It is noted that the crack can now be removed as it is sequestered and can be removed by its own weight. In the present invention completed by paying attention to this fact, the flow rate is increased and the lance height is increased so that slag forming is induced, and then the flow rate is decreased and the lance height is lowered before the sling is generated and attached to the lance. It is to coat the slag, which will be described with reference to FIG.

As shown in FIG. 2 (a), when the flow rate is increased and the lance height is increased, the firing point area (contact interface between molten iron and oxygen jet) increases from d1 to d2, and the cavity depth increases from h1 to h2. Conceptually, the phenomenon which appears in FIG. 2 (b) is described. As shown in FIG. 2 (b), when the flow rate is increased and the lance height is increased at a certain point of time, the collision momentum of the Songsan jet becomes stronger and the flash point area is widened to increase the decarburization rate and the oxidation rate of molten iron. do. As a result, the iron oxide concentration in the slag increases and the slag temperature rises sharply, resulting in a thick slag layer, a high slag temperature, a low slag melting point, and a low viscosity slag with good fluidity. Is increased to facilitate slag forming.

In the present invention, the slag forming is promoted as described above, and when the slag layer is raised and the sloping bleeding is observed through the furnace, the flow rate of the gas is immediately reduced and the lance 2 is lowered. This allows the slag layer to sink and the slag with good flowability is coated on the surface now attached to the lance for transpiration. As a result, tensile stress acts on the now-surface layer at the interface between now and the slag, and compressive stress acts on the surface of the lance and now at the interface between the lance and the space between the lance surface and now. It is isolated and cracked where it is partially fused to the lance and the current interface. At this time, the slag layer coated on the surface is broken off and the heavy now falls on the molten iron in the furnace by its own weight. This will allow the operation to continue stable. 3 schematically illustrates this series of processes. Figure 3 (a) shows the current state attached to the tranche for lances, Figure 3 (b) is a schematic diagram showing the process of dropping off the now attached to the Songsan lance during the conversion of the converter.

In the present invention, the point of time to increase the amount of acid and to raise the lance height is preferably the point of increasing the slag material, the temperature of the slag is increased. Increasing the slag recyclability and the temperature of slag increases depending on the conditions of the molten iron and the input conditions of the subsidiary materials, but most of the gas oxygen and molten iron blown from the lance after the middle stage of decoking It is the time when the iron oxide concentration produced by the reaction increases. Preferably, it is more preferable to increase the amount of delivery and raise the lance height after 60% of the blowing time. On the other hand, it is not preferable at the beginning of the drilling (beginning to 33% of the time) because the amount of added raw materials is less than 60% and the slag and molten iron are low. Due to the relatively low concentration of heavy iron oxide, it is difficult to induce slag high temperature, which is disadvantageous for inducing slag forming.

On the other hand, it is good to increase the flow rate and lance height control after 60% of the time of the above-mentioned increase of 5 to 15%. In this way, the flow rate and lance height are increased to induce slag high temperature and slag forming, and when the sling is seen from the furnace, the flow rate and the lance height are returned to the corresponding point in time. At this time, it is preferable that the upstream flow rate and the height of the lance are maintained at 5-15% of the blowing time. Increasing the transmission flow rate and lance height to less than 5% of the corresponding point, the effect of the slag high temperature and foaming effect is less effective, if it exceeds 15%, excessive slag movement is intense and the outflow of the hot slag deep out Or the risk of visible dust.

On the other hand, if the lance is continuously removed and the lance is to be removed in accordance with the present invention, it is more effective to apply the molten iron at a high molten iron temperature and containing 0.20 to 0.35 weight of silicon and manganese.

Hereinafter, the present invention will be described in detail through examples.

Example 1

(Conventional example)

After leaving about 30kg / t of slag last operated in a 300-ton converter, 10kg / t of fresh dolomite was added and the slag was coated on the furnace wall three to four times. ~ 17kg / t in the furnace, followed by 15% or less of the total amount of scrap as the main raw material, carbon 4.0-5.0% by weight, silicon 0.2-0.4% by weight, manganese 0.20-0.40% by weight, phosphorus 0.07-0.11% by weight More than 85% of the molten iron having a composition was charged into the converter furnace.

The furnace was then established, and the lance was lowered to start blowing. At this time, the converter blow pattern is as shown in Fig. 4 (a). In other words, when raw material is fed, fluorspar 0 ~ 1kg / TS is added, and in the middle of the blow (35 ~ 70% of the blowing time), P ₂ O ₅ is stabilized at low temperature in the slag generated by the induction of stable Tallin reaction. In order to protect the body, two to three times were added to the quicklime 1.5 ~ 2.0kg / TS. In addition, 2kg / TS of light dolomite was added at the end of the blow (70% of blow-up time) to induce continuous stable Tallin reaction and protect the body according to the high temperature.

Then, the sub lance was used to estimate the carbon content in the molten steel and measure the temperature at the dynamic point. When the temperature was high, the appropriate amount of coolant was added to adjust the temperature. Table 1 shows the component analysis values for the various subsidiary materials introduced in the above operation.

Chemical composition (% by weight) CaO MgO T.Fe MnO SiO ₂ Al ₂ O ₃ TiO ₂ CaF ₂ C S quicklime 92.5 2.20 0.39 - 0.92 0.30 - - - - Dolomite 56.26 38.80 0.60 - 1.40 0.51 - - - - Fresh dolomite 21.70 13.17 0.21 - 0.55 - - - - - fluorite - - - - 13.54 - - 83.86 - -

(Invention example)

Various auxiliary raw materials and coolant input during the drilling were performed in the same manner as the conventional method, and the slag behavior and the furnace temperature (1500 ° C. or higher) during the application of the converter blowing pattern of FIG. As shown in Fig. 6), the same flow rate was applied to the start time of the drilling ~ 70% of the time, but the Songshan flow rate increased by 10.2% from 57000Nm ³ / hr → 63000Nm ³ / hr at 70% of the time. At 75%, the rate was 60000 Nm ³ / hr → 67000Nm ³ / hr, an increase of 11.7%. In addition, the lance height was increased by 8.8% from 1930mm → 2100mm at 70% of the time of blowing, and increased by 10.0% from 2000mm → 2200mm at 75% of the time of blowing. In this way, the increase in the flow rate and the rise of the lance height were continued for about 10% of the blowing time, and the flow rate and the lance height were lowered to 85% at the blowing time, the moment when the slag formed from the furnace was seen. And after the transfer operation was completed, when the lance was raised, the previously attached was removed.

Example 2

After using the 300 ton converter continuously for about two months using the conventional method and the method of the present invention, the degree of removal of the current attached to the lance was examined, and the result was satisfactory. Later, although the lance nozzle was good, there was no lance discarded by the attachment now, which greatly improved lance life management and workability.

 As described above, the present invention is to control the flow rate and the lance height during the conversion of the converter to easily remove the now attached to the transmission lance by utilizing the slag motion naturally generated during the drilling without using a physical tool, By solving the problems that may cause deterioration, it is easy to secure and manage the service life of the lance and to prolong the life of the lance, thereby enabling stable and efficient operation.

Claims (2)

In the converter operation method of performing a blow while sending oxygen to the molten iron charged into the converter through a lance, Increasing the transmission flow rate by 15% compared to before the increase and the lance height by 5 to 15% compared to before the rise so that the slag forming in the furnace, In the process of induction of slag forming, if there is a sign of slopeing, reducing the feed flow rate to the flow rate before increasing, and lowering the lance height to the height before ascending, the feed lance made of a slag coated on the surface now attached to the lance Converter operation for the removal of the now attached to the. According to claim 1, wherein the flow rate and the lance height is adjusted upward at 60% after the start of the blow to maintain for 5-15% of the blowing time, and then to return to the lance for transcript flow and lance height Converter operation method for removing attached now.

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