JP2005097713A - Method for desiliconizing molten iron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently and stably perform a desiliconizing treatment to molten iron over the long time without bringing about the raise of a facility cost, when the desiliconizing treatment is applied to the molten iron on the pouring floor in a blast furnace. <P>SOLUTION: In a method for desiliconizing the molten iron, with which in the case of receiving the molten iron into a molten iron holding vessel set at the lower part of a tilting flume due to the falling flow of the molten iron 15 tapped off from the blast furnace from a molten iron flume 1 to a tilting flume 2, desiliconizing agent 16 is added into at least anyone of the molten iron in the molten iron flume, the falling flow of the molten iron from the molten iron flume to the tilting flume or the molten iron in the tilting flume, as the above tilting flume, the tilting flume 2 having V-shaped groove 6 at the bottom part is used and the molten iron is made to fall down from the molten iron flume by adjusting the position of the tilting flume so that the falling flow of the molten iron from the molten iron flume to the tilting flume collides against the inclined surface of the V-shaped groove. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a desiliconization method for removing silicon in hot metal, and more particularly, to a method for efficiently desiliconizing hot metal discharged from a blast furnace in a blast furnace casting floor.

  The hot metal discharged from the blast furnace is often subjected to desulfurization treatment and dephosphorization treatment called hot metal pretreatment before being refined in the converter. Initially, these pretreatments were carried out for steels that required low sulfidation and low phosphatization due to the quality of the steel materials. However, in recent years, productivity improvement in converters and reduction of Mn ore in converters As a means of reducing the total cost of the steelmaking process, desulfurization and dephosphorization treatments have been applied to almost all of the hot metal that is being produced at steelworks that are consistent with steelmaking. I came. In this case, since the dephosphorization reaction is inhibited when the silicon content of the hot metal is high, the hot metal desiliconization process is performed in advance in order to efficiently perform the dephosphorization process.

  As a hot metal desiliconization method, a blast furnace cast floor desiliconization method is widely adopted. In this blast furnace casting bed desiliconization method, iron oxide such as iron ore is used as a desiliconizing agent, and this desiliconizing agent is introduced into the hot metal flowing in the hot metal or tilting iron of the blast furnace casting bed through a chute or the like. , Blown and added together with the conveying gas through the lance or bottom blowing nozzle, or put in advance in a hot metal holding container such as a torpedo car before receiving, to react the silicon removal agent and silicon in the hot metal, For example, silicon is removed.

  In order to efficiently cause the desiliconization reaction in this desiliconization method, it is necessary to sufficiently hatch the desiliconizing agent and at the same time sufficiently bring the hatched desiliconizing agent into contact with the molten iron. That is, it is necessary to sufficiently stir the hot metal and the desiliconizing agent.

  For this reason, conventionally, many means for increasing the stirring strength between the hot metal and the desiliconizing agent have been proposed. For example, Patent Document 1 proposes a method in which a rotating magnetic field generated from a magnetic field generator is applied to a falling flow from a hot metal to a tilting iron, and the hot metal and the desiliconizing agent are rotated while rotating. . However, this method is not practical because it requires high equipment costs and requires measures for heat insulation of the apparatus.

In Patent Document 2, a receiving guide with a cylindrical outflow hole is provided at the outlet portion of the tilting iron, and the receiving guide generates a vortex in the falling flow of the hot metal from the tilting iron, A method of stirring and mixing the components has been proposed. However, in this method, there is a risk that eddy currents will gradually not be generated due to adhesion of metal or dust in the cylindrical outflow hole. In addition, since the hole diameter of the cylindrical outflow hole becomes small due to adhesion of the metal, etc., there is also a problem that the replacement operation of the receiving guide frequently occurs and the stable operation is hindered.
JP-A 64-83608 JP-A-3-153810

  As explained above, the conventional means for increasing the stirring strength of the hot metal and the desiliconizing agent in the blast furnace desiliconization method is expensive and impractical, or lacks operational stability. Or the development of effective means was eagerly desired.

  The present invention has been made in view of the above circumstances, and its object is to efficiently and for a long period of time without causing an increase in equipment costs when performing desiliconization treatment of hot metal on a blast furnace casting floor. An object of the present invention is to provide a desiliconization method capable of stably desiliconizing hot metal over a wide range.

  The inventors of the present invention diligently studied and studied to solve the above problems. The examination and research results are explained below.

  In the process of dropping the hot metal discharged from the blast furnace from the hot metal to the tilting iron and dropping it from the tilting iron into a hot metal holding container such as a torpedo car, the stirring strength between the hot metal and the desiliconizing agent is increased. In order to efficiently desiliconize, it was found that it is reasonable to strengthen the stirring in the tilting rod. By using the kinetic energy of the hot metal falling flow from the hot metal, the stirring strength can be increased relatively easily, and the stirring in the tilting iron is strengthened to achieve stirring and mixing. This is because, when the hot metal and the silicon removal agent fall into a hot metal holding container such as a torpedo car, stirring and mixing are promoted not only in the tilting iron but also in the hot metal holding container.

  Therefore, in order to strengthen the stirring in the tilting iron, the shape of the bottom surface of the tilting iron at the portion where the hot metal falling from the hot metal collides was tested as a structure having a V-shaped groove. Normally, the shape of the bottom of the tilting rod is flat (flat bottom), but by providing a V-shaped groove, the flow range of the falling flow after colliding with the bottom of the tilting rod is narrowed, and the falling flow is reduced. Based on the assumption that strong stirring is performed in the vicinity of the V-shaped groove or in the vicinity of the V-shaped groove, in other words, the kinetic energy of the falling flow is concentrated in a narrow range. It is based on the assumption that it will be strengthened.

  FIG. 1 shows a schematic diagram of a tilting rod having a V-shaped groove used in the test, and FIG. 2 shows a schematic diagram of a conventional tilting rod having a flat bottom structure tested for comparison. 1A is a plan view, FIG. 1B is a longitudinal sectional view taken along the line XX ′ of FIG. 1A, FIG. 2A is a plan view, and FIG. 2B is a diagram. It is a longitudinal cross-sectional view by the YY 'arrow of 2 (A). 1 and 2, reference numeral 2 represents a tilting rod having a V-shaped groove, symbol 2a represents a conventional tilting rod, symbol 6 represents a V-shaped groove, and symbol D represents The thickness of the bottom refractory of the tilting rod is represented, and the symbol θ represents the inclination angle of the V-shaped groove.

  Iron ore powder was used as a desiliconization agent, air was used as a carrier gas, and iron ore powder was sprayed onto the hot metal falling position in the tilting iron via an upper blowing lance for desiliconization treatment. Samples for analysis were collected from the hot metal before and after the silicon removal treatment, and the silicon concentration of the hot metal was analyzed, and the silicon removal oxygen efficiency (η) was determined based on the following equation (1). In addition, in order to investigate the transition of the amount of wear of the bottom refractory in the tilting rod, the thickness of the bottom part refractory (D) shown in FIGS. Measured immediately before wandering.

  FIG. 3 shows the transition of the minimum thickness of the refractory at the bottom of the tilting rod by comparing the tilting rod 2 having a V-shaped groove with the tilting rod 2a having a conventional flat bottom structure. The change of desiliconization oxygen efficiency (η) is shown in comparison. The solid line in FIG. 3 represents the case of the tilting rod 2 having a V-shaped groove, and the broken line represents the case of the tilting rod 2a having a flat bottom structure. In addition, the one-dot chain line in FIG. 3 is the thickness management reference value of the refractory at the bottom of the tilting rod, and when the refractory at the bottom is worn out and the minimum thickness of the refractory reaches the management reference value, Is removed for repair and replaced with another decanting rod.

  As shown in FIG. 3, the silicon removal oxygen efficiency (η) is 5 to 5 when compared to the case of using a conventional flat-bottom tilting rod when using a tilting rod having a V-shaped groove. It was found to improve by 10%. Even when a tilting rod having a V-shaped groove is used, if the refractory at the bottom is worn out, the desiliconization oxygen efficiency (η) is reduced and the conventional flat-bottom tilting rod is used. It has been found that the difference in the predominance of oxygen is reduced, and the desiliconization oxygen efficiency (η) is at the same level as that of a conventional tilting rod. In FIG. 3, the reason why the silicon removal oxygen efficiency (η) in the tilting rod of the structure having the V-shaped groove increases in a sawtooth shape is that the wear of the refractory forming the V-shaped groove is This is because the hot metal drop position is corrected so as to hit the slope of the V-shaped groove.

  From these results, the shape of the bottom surface of the tilting iron corresponding to the position where the hot metal falls from the hot metal has a V-shaped cross section and has a groove extending in the longitudinal direction of the tilting iron. It was found that the kinetic energy resulting from this is increased in density, so that stirring of the hot metal and the desiliconizing agent is promoted and the desiliconization oxygen efficiency (η) is improved. However, it has been found that as the wear of the bottom refractory progresses, its action / effect decreases. The shape of the V-shaped groove shown in FIG. 1 has a flat portion on the bottom surface. Strictly speaking, the shape of the V-shaped groove is not “V-shaped”. A shape having a slope is defined as “V-shaped”.

  To maintain the action and effect of increasing the desiliconization oxygen efficiency (η) by the slope of the V-shaped groove for a long time, how to maintain the refractory that forms the slope of the V-shaped groove in a healthy state However, it is currently impossible to completely prevent the refractory from being worn. However, although it is not possible to completely prevent the wear of the refractory, if the hot metal is dropped from the hot metal so that the falling flow always collides with the healthy part of the refractory that forms the slope of the V-shaped groove, It was found that the action and effect of increasing the silicon removal oxygen efficiency (η) by the slope of the V-shaped groove can be maintained for a long time. As will be described later, since the tilting iron is tilted to one torpedo car side, while pouring the hot metal into the torpedo car on the tilted side, it receives the hot metal discharged from the blast furnace, so that the hot metal is accumulated in the tilting iron. After that, there is little concern that collision with the slope of the V-shaped groove and stirring will be hindered.

  The present invention has been made on the basis of the above knowledge, and the hot metal desiliconization method according to the present invention allows the hot metal discharged from the blast furnace to flow down from the hot metal to the tilting iron and installed below the tilting iron. When receiving in the hot metal holding container, a desiliconizing agent is added to the hot metal in at least one of the hot metal in the hot metal, the falling flow of the hot metal from the hot metal to the tilting iron, and the hot metal in the tilting iron. A method of desiliconizing hot metal, wherein a tilting iron having a V-shaped groove at the bottom is used as the tilting iron, and the falling flow of the hot metal from the hot metal to the tilting iron collides with the slope of the V-shaped groove. As described above, the position of the tilting iron is adjusted to cause the hot metal to flow down from the hot metal.

  According to the present invention, the hot metal flows down by adjusting the position of the tilting iron so that the falling flow of the hot metal from the hot metal collides with the slope of the V-shaped groove installed on the tilting iron. Even if the refractory forming the groove is worn out, as long as the V-shaped groove remains at the bottom of the tilting rod, the flow range of the falling flow after colliding with the slope of the V-shaped groove becomes narrow, By concentrating the kinetic energy of the falling flow in a narrow range, the hot metal and the desiliconizing agent are strongly stirred, and the desiliconization oxygen efficiency (η) can be increased stably over a long period of time. In addition, since the present invention can be implemented simply by providing a facility for adjusting the position of the tilting rod, it is possible to cope with a low facility cost and to suppress an increase in cost due to an increase in facility cost.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 4 and 5 are schematic views showing an example of a cast bed desiliconization facility used in carrying out the desiliconization method according to the present invention, and FIG. 4 shows the positional relationship between the hot metal, the tilting iron and the torpedo car. FIG. 5 is a schematic side view showing, and FIG. 5 is a schematic side view of the pouring process to the inclined pouring rod shown in FIG. 4 as viewed from the side perpendicular to FIG.

  As shown in FIG. 4 and FIG. 5, a hot metal 1 for flowing hot metal 15 discharged from the blast furnace is installed on a cast floor of a blast furnace (not shown). An inclined pouring bar 2 for pouring the received hot metal 15 into the hot metal holding container such as the torpedo car 3 at the same time as receiving the hot metal 15 flowing down from the hot metal 1 is installed immediately below the hot metal. Below the inclined pouring rod 2, a hot metal holding container such as a torpedo car 3 is carried in and out. Although the torpedo car 3 is used as the hot metal holding container in FIG. 4, a ladle type hot metal ladle may be used instead of the torpedo car 3.

  Directly below the front end of the hot metal 1, as shown in FIG. 5, there are provided trolley receiving stands 8, 8 facing each other across the position where the hot metal 15 drops from the hot metal 1. Is provided with a hydraulic cylinder 13. Further, a carriage 7 is arranged on the carriage receiving base 8 so as to pass a space between the opposing carriage receiving stands 8, 8, and the carriage 7 is connected to a rod of the hydraulic cylinder 13. A plurality of wheels 14 are installed on the carriage 7, and the carriage 7 has a structure that can move on the carriage receiving stands 8, 8 via the wheels 14 by operating the hydraulic cylinder 13. . The carriage 7 is provided with a pair of bearings 11, 11. A support frame 9 having shafts 10, 10 is mounted on the carriage 7 with the shafts 10, 10 being rotatably supported by the bearings 11, 11. ing. Further, the cart 7 is provided with a tilting motor 12, and the shaft 10 is turned by the operation of the tilting motor 12. The tilting rod 2 is supported by the support frame 9 having such a structure.

  That is, the tilting rod 2 mounted on the carriage 7 via the support base 9 is structured to tilt about the shaft 10 as a turning axis by the operation of the tilting electric motor 12, and at the same time, by the operation of the hydraulic cylinder 13, It has a structure that approaches or moves away from the hot metal 1.

Reference numerals 17 ₁ , 17 ₂ ,... 17 _{n denote} position sensors such as proximity switches and limit switches for detecting positions where the tilting iron 2 approaches or moves away from the hot metal 1. Reference numeral 17 is a striker, 18 is a solenoid valve, 18A is a pressure reducing valve, 18B is a flow control valve, 19 is a tank, 20 is a pump, 21 is a control device, and 22 is a manual operation button. Solenoid valve 18 Other DS3P, may be a servo valve, the position sensor 17 _1, 17 _2, the sill NACK sensor may be installed in place of the proximity switch ... 17 _n.

  Above the drop point of the hot metal 15 from the hot metal 1 to the tilting iron 2, an upper blowing lance 5 for spraying and adding the desiliconizing agent 16 through a carrier gas is installed. As the silicon removal agent 16, iron oxide such as iron ore or mill scale is used. A basic substance such as quick lime powder for adjusting the basicity of the generated slag may be mixed with the iron oxide to form the desiliconizing agent 16. As the carrier gas, air, oxygen gas, nitrogen gas, Ar gas, or the like can be used.

  Like the tilting rod 2 shown in FIG. 1 described above, the tilting rod 2 used in the present invention has a V-shaped groove at the bottom and a V-shaped groove (hereinafter referred to as “longitudinal”) extending in the longitudinal direction of the tilting rod 2. "V-shaped groove 6"). In forming the V-shaped groove 6, if the inclination angle between the slope of the V-shaped groove 6 and the horizontal plane is θ (see FIG. 1), the inclination angle θ is 15 ° or more and 55 ° or less, preferably 30 °. The depth of the V-shaped groove 6 is desirable because the refractory replacement frequency decreases as the depth increases, and is preferably 100 mm or more. The upper limit of the depth is not particularly specified, but is preferably 1000 mm or less in order to obtain sufficient stirring strength. Furthermore, the length in the longitudinal direction of the tilting rod 2 of the V-shaped groove 6 is not particularly defined, and is a length that can secure at least a range in which the falling flow of the hot metal 15 from the hot metal 1 collides with the tilting rod 2. If it is. The V-shaped groove 6 may be formed by combining molded refractories, or may be formed by pouring construction of an irregular refractory such as a castable refractory. The corner portion at the tip of the V-shaped groove 6 does not necessarily need to be a surface that intersects linearly, and may be curved such as an arc depending on the ease of construction.

  Thus, the cast floor desiliconization equipment used in the present invention is configured. Hereinafter, the hot metal desiliconization method according to the present invention using the cast bed desiliconization equipment configured as described above will be described.

The hot metal 15 discharged from the blast furnace is caused to flow down in the hot metal 1 and is dropped from the tip of the hot metal 1 onto the tilting iron 2. At that time, the hydraulic cylinder 13 is operated at a position where the falling flow of the hot metal 15 from the hot metal 1 collides with the inclined surface of the V-shaped groove 6 installed at the bottom of the tilting iron 2, and the carriage 7 is installed thereon. The striker 17 is moved to a position where the position sensor 17 ₁ is turned on. When the hot metal 15 starts to fall from the hot metal 1, the desiliconizing agent 16 is sprayed and added from the upper blowing lance 5 toward the dropping point of the hot metal 15.

In addition, for example, the striker 17 has a position sensor 17 ₂ , a position sensor 17 ₃ ,..., A position sensor 17 _n , The operation of turning on in the order of 17 ₁ ,..., Position sensor 17 _n . The certain time here is preferably the time when the net hot metal 15 falls on the tilting iron 2, but may be other methods such as calendar time. The order in which the striker 17 is turned on to the position sensors 17 ₁ , 17 ₂ ,... 17 _n is not necessarily limited to the above example. If the position sensor 17 ₁ , 17 ₂ ,..., 17 _n uses a Sirnac sensor instead of a proximity switch, the carriage 7 can be set almost continuously at any position. Alternatively, the operator may determine that the wear of the refractory has progressed, and operate the manual operation button 22 so that the hot metal is dropped so as to avoid the worn portion.

  Further, since the trajectory of the falling flow from the hot metal 1 differs depending on whether the amount from the blast furnace is large or not, the manual operation button 22 is operated by visually observing the position of the carriage 7 immediately after unloading. Then, once the adjustment is performed, the manual operation button 22 may be adjusted by the operator's visual observation according to the amount of the output during the output. In addition, the inclination angle of the inclined surface of the V-shaped groove 6 changes depending on the degree of wear of the V-shaped groove 6, and the stirring strength also changes. Therefore, the inclination angle of the inclined surface is within the initial inclination angle range or the most initial. According to the degree of melting of the V-shaped groove 6 so as to collide with a portion close to the inclination angle, the installation position of the tilting rod 2 is adjusted, and the action / effect of increasing the desiliconization oxygen efficiency (η) by stirring is achieved. It is preferable to maintain for a long time.

  In this way, the hot metal 15 is poured into the torpedo car 3 while desiliconizing the hot metal 15, and when a predetermined amount of hot metal 15 is stored in the torpedo car 3, the tilting motor 12 is operated to tilt the tilting iron 2. Then, the hot metal 15 is poured into the waiting torpedo car 4. Also at this time, the desiliconizing agent 16 is continuously added, and the desiliconization treatment of the hot metal 15 is continued until the end of the receiving.

  As described above, in the present invention, when the hot metal 15 is desiliconized, the falling flow of the hot metal 15 from the hot metal 1 is made to collide with the slope of the V-shaped groove 6 of the tilting iron 2. The flow range of the falling flow from 1 is narrowed, and the kinetic energy of the falling flow is concentrated in a narrow range, so that stirring occurs intensively in a narrow range, whereby stirring of the hot metal 15 in the tilting iron 2 is performed. Strengthened. As a result, the added desiliconizing agent 16 is vigorously stirred and mixed with the molten iron 15 to accelerate the hatching of the desiliconized agent 16 and at the same time, the contact time with the molten iron 15 is sufficiently secured. The silicon reaction is promoted, the desiliconization oxygen efficiency (η) is increased, and the molten iron 15 can be sufficiently desiliconized even with a small amount of the desiliconizing agent 16 used.

  In addition, this invention is not restricted to the thing of the form demonstrated above, A various change is possible. For example, the desiliconizing agent 16 is sprayed and added toward the dropping point of the hot metal 15 from the hot metal 1 to the tilting iron 2, and a chute is used on the hot metal 15 in the hot metal 1 on the bath surface of the hot metal 15. It may be added, or sprayed onto the hot metal bath surface using a lance or added into the hot metal, or added toward the falling flow from the hot metal 1, etc. You may combine them. Further, when the molten iron 15 is desiliconized, a gaseous oxygen source such as oxygen gas may be used in combination with a desiliconizing agent mainly composed of iron oxide. Furthermore, although the cart 7 on which the tilting iron 2 is mounted is moved back and forth with respect to the hot metal 1, it may be moved left and right. Furthermore, although the carriage 7 is moved by the hydraulic cylinder 13, another driving force such as an electric motor may be used instead of the hydraulic cylinder 13.

  Below, in order to verify the effect of this invention, the result of the actual machine desiliconization experiment conducted using the cast-bed desiliconization equipment shown in FIG.4 and FIG.5 is demonstrated. The tilting rod used is a tilting rod having a maximum width of 1500 mm and a length of 5000 mm. At the bottom of this tilting rod, the tilt angle θ is 45 °, the depth is 150 mm, and the longitudinal length of the tilting rod is 1000 mm. A V-shaped groove was installed. The V-shaped groove was formed by pouring construction using the same castable refractory as the part other than the V-shaped groove.

  When the hot metal was received, the position of the tilting iron was adjusted by a hydraulic cylinder so that the falling flow of the hot metal from the hot metal always hit the slope of the V-shaped groove. The position adjustment of the tilting rod by the hydraulic cylinder was performed by the operator visually confirming the shape of the V-shaped groove before receiving and the operator also visually confirming the collision position of the falling flow.

  The hot metal temperature in the hot metal is about 1480 ° C., the silicon content of the hot metal in the hot metal is 0.2 to 0.3% by mass, air is used as a carrier gas, and iron ore powder as a desiliconizing agent is used as a carrier. The desiliconization treatment was performed while adding the gas at a rate of 350 kg / min. An analytical sample of hot metal was collected from the hot metal and torpedo car, and the desiliconization oxygen efficiency (η) was determined by the above-described equation (1). As a result, the desiliconization oxygen efficiency (η) in this desiliconization experiment obtained an average value of 38%, and the desiliconization oxygen efficiency (η) was 5 to 10% as compared with the case of the conventional flat-bottom tilting iron. It was confirmed that the degree was improved.

It is the schematic of the tilting rod of a structure with a V-shaped groove | channel, (A) is a top view, (B) is a longitudinal cross-sectional view by X-X 'arrow of (A). It is the schematic of the tilting rod of the conventional flat bottom structure, (A) is a top view, (B) is a longitudinal cross-sectional view by the Y-Y 'arrow of (A). It is a figure which contrasts and shows the transition of the minimum thickness of the bottom part refractory of a tilting iron, and the transition of desiliconization oxygen efficiency ((eta)). It is a schematic side view which shows the positional relationship of a hot metal, a tilting iron, and a torpedo car. It is the schematic side view which looked at the pouring process to the tilting pouring rod shown in FIG. 4 from the side surface orthogonal to FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hot metal 2 Tilt casting 3 Torpedo car 4 Torpedo car 5 Top blowing lance 6 V-shaped groove 7 Bogie 8 Bogie receiving stand 9 Supporting stand 10 Axis 11 Bearing 12 Tilt motor 13 Hydraulic cylinder 14 Wheel 15 Hot metal 16 Desiliconizer 17 Strike 17 ₁ , 17 ₂ ,... 17 _n Position sensor 18 Solenoid valve 18 A Pressure reducing valve 18 B Flow control valve 19 Tank 20 Pump 21 Control device 22 Manual operation button

Claims (1)

  When the hot metal discharged from the blast furnace flows down from the hot metal to the tilting iron and is received by the hot metal holding container installed below the tilting iron, the hot metal in the hot metal and the hot metal from the hot metal to the tilting iron A method of desiliconizing a hot metal by adding a desiliconizing agent to the hot metal in at least one of the falling flow and the hot metal in the tilting iron, wherein the tilting iron having a V-shaped groove at the bottom as the tilting iron The hot metal is made to flow down from the hot metal by adjusting the position of the hot metal so that the falling flow of the hot metal from the hot metal to the inclined hot metal collides with the slope of the V-shaped groove. Desiliconization method.

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