JP2008138271A - Refining method in converter type refining furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To refine molten iron or molten steel and simultaneously, efficiently melt the metal stuck onto the inner wall of a converter-type refining furnace, when the molten iron or the molten steel is refined by supplying oxygen from a top-blowing lance. <P>SOLUTION: When the molten iron or the molten steel is refined while supplying oxygen into the molten iron 8 or the molten steel charged into the converter-type refining furnace by using the top-blowing lance 2 having a main hole nozzle for blowing in the vertical lower direction or the inclined lower direction at the tip end part and having sub-hole nozzles 16 in the horizontal or the inclined lower direction on the side surface of the upper positional side surface of the upper blowing lance by separating a prescribed interval from the tip end part, the oxygen is supplied by controlling so that the horizontal directional distance (X<SB>0</SB>×sinθ) from the sub-nozzle outlet to the position where the center flowing speed of oxygen spouting flow spouted from the sub-hole nozzle is reduced to 30 m/s, becomes in the range of 0.10-0.75 of the distance (H) from the top blowing lance center to the side wall of the converter-type refining furnace. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention supplies oxygen from an upper blowing lance to refine hot metal or molten steel accommodated in a converter-type refining furnace, and at the same time, can dissolve metal that has adhered to the inner wall of the converter-type refining furnace. The present invention relates to a refining method in a furnace type refining furnace.

  In recent years, in order to improve productivity, in the decarburization and refining of hot metal in a converter type refining furnace (also referred to as “decarburization treatment”), the oxygen supply rate from the top blowing lance (also referred to as “acid feed rate”) has been increased. It is intended to shorten the blowing time. However, by increasing the acid feed rate, spitting (a phenomenon in which the oxygen jet from the top blowing lance collides with the molten iron or molten steel and the molten iron or molten steel scatters) increases, resulting in the inner wall and furnace opening of the converter type refining furnace. As a result, there was a problem that the bullion was adhered, and as a result, the stable operation was hindered and the yield of molten steel decreased.

  Also, using a converter-type refining furnace, hot metal dephosphorization is widely performed in a low temperature range of about 1300 to 1400 ° C., which is advantageous for dephosphorization equilibrium. However, in order to perform dephosphorization and refining in the hot metal stage at a relatively low temperature, hot metal adheres to and solidifies on the inner wall and furnace port of the converter-type refining furnace, and metal is deposited, leading to a decrease in hot metal yield. There was also a problem.

Various means have been proposed to solve these problems. For example, Patent Document 1, the top lance tip, an inner nozzle of the outward inclination angle theta ₁ on the circumference, in the same direction and the inner nozzle and an outer nozzle outward inclination angle theta _2, theta ₂ is Refining provided so as to be larger than θ _{1 and controlled} so that the overlap area of the cavity formed by the oxygen jet of the inner nozzle and the oxygen jet of the outer nozzle is 50% or less of the area of the cavity formed by the oxygen jet of the inner nozzle. A method is disclosed.

  Patent Document 1 is a technique for reducing the spitting by reducing the collision force of the oxygen jet to the molten metal surface by suppressing the overlap of the oxygen jet from each nozzle provided at the tip of the lance as much as possible. However, this method seems to have some effect of reducing spitting, but as long as an oxygen jet is blown to the surface of the molten metal, it is difficult to achieve zero spitting. Therefore, spitting increases, and it seems that metal is attached to the furnace. Further, once the bullion has adhered to the inside of the furnace or the furnace port, it is impossible in Patent Document 1 to remove the bullion.

  In Patent Document 2, a main nozzle composed of a laval nozzle for refining and a straight sub-nozzle for promoting secondary combustion are alternately arranged at the top end of an upper blowing lance, and an upper position side surface having a predetermined interval from the tip of the lance. Discloses an upper blowing lance provided with an auxiliary nozzle for melting a metal bar having an angle of −45 ° to + 70 ° with respect to the horizontal and a diameter of 1 to 15 mm. According to Patent Document 2, the use of the top blowing lance enables the removal of bullion adhering to the entire area of the converter type refining furnace. However, a smelting laval nozzle and secondary combustion acceleration are provided at the tip of the lance. If the straight jet sub nozzle is used, the oxygen jet from the secondary burn straight sub nozzle may affect the oxygen jet from the refining laval nozzle, and there is a concern that the refining capacity will be reduced. The

  In Patent Document 3, there is a top blowing lance having a main nozzle composed of a refining laval nozzle at the tip of a top blowing lance, and an auxiliary nozzle for melting a metal bar on the side surface at a predetermined distance from the tip. It is disclosed. However, as compared with the above-described top blowing lance of Patent Document 2, since the straight type nozzle for promoting secondary combustion is not installed at the tip, if the metal is deposited all over the furnace, it can be removed. Patent Document 2 describes that it is difficult to achieve this.

Thus, the conventional technique for preventing metal adhesion to the inner wall of the converter-type refining furnace and the technique for melting the attached metal are not yet fully effective, and the inner wall or furnace opening of the converter-type refining furnace. The bullion was attached to the shore, which obstructed stable operation and lowered the yield of molten steel.
Japanese Patent Laid-Open No. 11-36009 JP-A-10-219329 JP-A-8-127812

  The present invention has been made in view of the above circumstances, and its purpose is to supply oxygen from an upper blowing lance to refine hot metal or molten steel contained in a converter-type refining furnace. An object of the present invention is to provide a refining method in a converter type refining furnace capable of efficiently melting the metal attached to the inner wall of the converter refining furnace simultaneously with refining.

  The refining method in the converter type refining furnace according to the first aspect of the present invention for solving the above-mentioned problem is the method of supplying oxygen from the top blowing lance and refining the hot metal or molten steel accommodated in the converter type refining furnace. A main hole nozzle for blowing in a vertically downward direction or an obliquely downward direction is disposed at the tip of the blowing lance, and a horizontal or obliquely downward direction on the side surface of the upper blowing lance above the predetermined distance from the tip of the upper blowing lance. The number of sub-hole nozzles installed, the outlet diameter of the sub-hole nozzle, and the sub-hole nozzle so that the flow velocity of the oxygen jet ejected from the sub-hole nozzle satisfies the following condition (1) The oxygen is supplied from the upper blowing lance by adjusting any one or two or more of the throat diameter, the inclination angle of the sub-hole nozzle, and the acid feed speed from the sub-hole nozzle It is.

However, in the equation (1), X ₀ is the distance (m) from the outlet of the sub-hole nozzle to the point where the central flow velocity of the oxygen jet ejected from the sub-hole nozzle is reduced to 30 m / s, and θ is the sub-hole nozzle. The angle between the center line of the top blow lance and the center line of the top blowing lance (deg .: 0 ° <θ ≦ 90 °), and H is from the center of the top blowing lance to the side wall of the converter-type refining furnace And X ₀ can be obtained by the following equations (2), (3), and (4).

In the equations (2) to (4), de is the outlet diameter (mm) of the sub-hole nozzle, V ₀ is the flow velocity (m / s) of the oxygen jet at the sub-hole nozzle outlet, and P ₀ is the sub-hole nozzle diameter. absolute pressure display of the oxygen back pressure hole nozzle ^{(kgf / cm 2), P} e is the absolute pressure indication of the ambient pressure of the converter type refining furnace (kgf / cm ^2: under atmospheric pressure 1.033kgf / cm ² ), F is the acid feed rate (Nm ³ / hr) from the sub-hole nozzle, n is the number of sub-hole nozzles, and dt is the throat diameter (mm) of the sub-hole nozzle.

  In the refining method in the converter type refining furnace according to the second invention, in the first invention, the acid feed rate from the sub-hole nozzle is in the range of 5 to 30% of the acid feed rate from the main hole nozzle. It is characterized by.

  In the refining method in the converter type refining furnace according to the third invention, in the first or second invention, the oxygen supply flow path to the sub-hole nozzle and the oxygen supply flow path to the main hole nozzle are the same. It is characterized by this.

  According to the present invention, the main hole nozzle for blowing in the vertically downward direction or the obliquely downward direction is provided at the tip, and the horizontal or obliquely downward direction is disposed on the upper position side surface of the upper blowing lance spaced from the tip by a predetermined distance. When refining the hot metal or molten steel by supplying oxygen to the hot metal or molten steel accommodated in the converter-type refining furnace using the top blowing lance having the secondary hole nozzle, the flow velocity of the oxygen jet from the auxiliary hole nozzle is Since the control is performed so as to satisfy the above-described expression (1), that is, the horizontal distance from the sub-hole nozzle outlet to the point where the central flow velocity of the oxygen jet ejected from the sub-hole nozzle is reduced to 30 m / s is Since the distance from the center of the blowing lance to the side wall of the converter-type refining furnace is controlled to be within the range of 0.10 or more and 0.75 or less, the speed of the oxygen jet in the furnace becomes slow, and the refining of hot metal or molten steel Occurrence The reaction between the CO gas and the oxygen ejected from the sub-hole nozzle, that is, the secondary combustion reaction, is performed efficiently, and simultaneously with the refining of the molten iron or molten steel, It can be efficiently melted by the secondary combustion heat, and has industrially beneficial effects such as improvement of converter productivity and improvement of molten steel yield.

  Hereinafter, the present invention will be specifically described with reference to the drawings. First, the examination results that led to the present invention will be described.

  When the present inventors supply oxygen from the top blowing lance and refine the hot metal or molten steel, simultaneously with the refining of the molten iron or molten steel, in order to efficiently dissolve the metal that has adhered to the inner wall of the converter type refining furnace, We investigated and examined under various conditions using a converter-type refining furnace.

  Conventionally, if a supersonic or subsonic oxygen jet is blown from a top blowing lance onto hot metal or molten steel accommodated in a converter type refining furnace, refining has been unavoidable. Therefore, the present inventors do not need to spend time for removing the metal and repairing the furnace body if the metal attached to the furnace body can be melted at the same time as the refining process, and there is a concern that the productivity of the converter may be reduced. I thought it would disappear. Moreover, since the furnace body adhesion metal melt | dissolved simultaneously with the refining process can be collect | recovered in hot metal or molten steel, it is also possible to suppress a yield fall.

  As one of means for melting the bullion attached to the furnace body, there is a method of blowing the bullion by injecting oxygen for melting the bullion onto the surface of the attached metal like Patent Document 3 described above. However, in this method, when the interval between the refining treatments becomes long and the inside of the furnace is cooled, or when the temperature of the adhered metal surface decreases, such as in the case of treatment at a relatively low temperature such as hot metal pretreatment In some cases, even if oxygen is blown onto the metal, it does not ignite, the fusing efficiency of the metal decreases, and in the worst case, it cannot be removed. In addition, with this method, it is possible to remove the bullion only in the part where the oxygen for melting the bullion directly collides with the bullion. It is difficult.

Therefore, the present inventors studied to melt the furnace body adhering metal using reaction heat by secondary combustion. In general, it is known that the secondary combustion rate is increased by increasing the lance height (the distance between the iron bath surface and the tip of the upper blowing lance). However, since increasing the lance height affects the refining ability, it is not desirable to easily increase the lance height to increase the secondary combustion rate. In addition to the refining main nozzle at the tip of the lance, many lances have been developed in which a secondary nozzle for supplying secondary combustion oxygen is provided as in the above-mentioned Patent Document 2, but an oxygen jet from the main nozzle has been developed. And the oxygen jet from the sub nozzle mutually affect each other, so that the respective characteristics have not been fully exhibited. The secondary combustion means that CO gas or H ₂ gas generated in refining (also referred to as oxygen blowing) performed by supplying oxygen is burned in the furnace to CO ₂ gas or H ₂ O by the supplied oxygen. That is. In oxygen blowing of hot metal and molten steel, CO gas is mainly generated.

  Based on these events, the present inventors consider that it is necessary to completely separate the oxygen supply nozzle for refining and the oxygen supply nozzle for secondary combustion, and a refining nozzle ( Using an upper blow lance provided with a nozzle (sub-hole nozzle) for supplying secondary combustion oxygen in the horizontal or obliquely downward direction on the side surface above the upper blow lance at a predetermined distance from the tip. Then, the technology to melt the furnace body adhesion metal at the same time as the refining treatment was examined.

  First, an experiment was conducted using an upper blowing lance with an arbitrarily designed number of holes and diameter size of the main hole nozzle and sub hole nozzle. A melting phenomenon was observed, and a portion where the furnace wall refractory was melted by the collision of the oxygen jet was also observed. Therefore, the following knowledge was obtained as a result of conducting experiments with several top blowing lances by changing the number of holes and diameters of the main hole nozzle and the sub hole nozzle and examining optimum conditions.

  As a cause of local dissolution of the furnace body adhesion metal and local melting of the furnace wall refractory, the momentum of the oxygen jet from the sub-hole nozzle is too strong, that is, the flow velocity is too high, It was found that these local phenomena occur because oxygen reaches the furnace wall directly. Before the oxygen jet from the sub-hole nozzle reaches the furnace wall, the oxygen jet reacts with the CO gas generated in the furnace to generate secondary combustion, so that the secondary combustion heat is uniformly distributed in the furnace. We considered that the oxygen jet flow from the sub-hole nozzle could be controlled.

From general knowledge in hydrodynamics, it is known that when the fluid is oxygen, the oxygen back pressure in absolute pressure display at the nozzle that ejects oxygen is expressed by the following equation (4). However, in the equation (4), P ₀ is the oxygen back pressure (kgf / cm ² ) expressed in absolute pressure of the sub-hole nozzle, F is the acid feed rate (Nm ³ / hr) from the sub-hole nozzle, and n is , The number of nozzles of the sub-hole nozzle, dt is the throat diameter (mm) of the sub-hole nozzle.

Further, it is known that the jet velocity V ₀ of the oxygen jet at the nozzle outlet is expressed by the following equation (3). In Equation (3), V ₀ is the flow velocity (m / s) of the oxygen jet at the outlet of the sub-hole nozzle, P ₀ is the oxygen back pressure (kgf / cm ² ), P _e is the absolute pressure indication of the ambient pressure of the converter type refining furnace (kgf / cm ^2), a P _e = 1.033kgf / cm ² under the atmospheric pressure, such as a converter furnace.

Furthermore, regarding the attenuation behavior of the oxygen jet after the nozzle outlet, an empirical formula (reference: NKK Technical Report, No. 39 (1967), p. 19) shown in the following formula (5) has been submitted. In equation (5), de is the outlet diameter (mm) of the sub-hole nozzle, V ₀ is the flow velocity (m / s) of the oxygen jet at the sub-hole nozzle outlet, and P ₀ is the absolute pressure of the sub-hole nozzle. display oxygen back pressure (kgf / cm ^2), the P _e, absolute pressure indication of the ambient pressure of the converter type refining furnace (kgf / cm ^2), X is the distance from the sub-ports nozzle outlet (m), V is the central flow velocity (m / s) of the jet at the position of the distance X. Here, the center flow velocity of the jet means the flow velocity at the center position of the jet.

  The present inventors conducted various experiments and analyzes on the flow velocity V shown in Equation (5). As a result, when the flow velocity V attenuated to 30 m / s, the CO gas generated in the furnace and the sub-hole nozzle It has been found that the secondary combustion reaction occurs with the oxygen supplied from the reactor.

Therefore, in equation (5), the distance from the sub-hole nozzle outlet to the point where the central flow velocity of the oxygen jet ejected from the sub-hole nozzle is reduced to 30 m / s is X ₀ (m), and V in equation (5) Substituting 30 m / s for, the following equation (2) is obtained for the distance X ₀ .

As a result of experiments conducted by designing the top blowing lance and controlling the blowing conditions within an appropriate range where this distance X ₀ does not reach the furnace wall, local melting of the metal and local melting of the furnace wall refractory were confirmed. It was clarified that the heat of secondary combustion reaction can be uniformly dispersed in the furnace.

In addition, the throat diameter dt and the outlet diameter de of the sub-hole nozzle shown in the expressions (2), (4), and (5) are as follows. FIG. 1 shows a schematic cross-sectional view when the sub-hole nozzle 16 has a Laval nozzle shape. As shown in FIG. 1, the Laval nozzle 17 has a shape composed of two cones, ie, a portion whose cross section is reduced and a portion where the cross section is enlarged. In the Laval nozzle 17, the reduced portion is a throttle portion 18 and the enlarged portion is a skirt. The narrowest part of the transition from the narrow part 20 and the throttle part 18 to the skirt part 20 is called the throat 19, where dt which is the inner diameter of the throat 19 is the throat diameter and de which is the inner diameter of the outlet is output. It is called the caliber. The spread angle θ ₀ of the skirt portion 19 is usually 10 ° or less. Oxygen is jetted as a supersonic or subsonic jet through the throttle part 18, the throat 19 and the skirt part 20 in this order. When the sub-hole nozzle 16 is a straight type nozzle, the throat diameter dt and the outlet diameter de may be equal to each other, and the inner diameter of the straight portion may be used.

Next, an appropriate range of the distance X ₀ will be described with reference to a cross-sectional view of a simple converter-type refining furnace shown in FIG. Θ (deg .: 0 ° <θ ≦ 90 °), the angle formed by the center line of the sub-hole nozzle 16 installed in the horizontal direction or diagonally downward direction and the center line of the upper blowing lance 2 as a reference, If the distance from the outlet of the sub-hole nozzle to the point where the central flow velocity of the oxygen jet ejected from the sub-hole nozzle 16 is reduced to 30 m / s is X ₀ (m), the horizontal arrival distance of the oxygen jet is X ₀ sinθ. It is represented by Regarding the appropriate range of X ₀ sinθ, the knowledge obtained from the experimental results is as follows.

That is, assuming that the horizontal distance from the center of the top blowing lance to the furnace wall of the converter-type refining furnace 1 is H (m), X ₀ sinθ / H is 0 as a result of experiments using various top blowing lances 2. It became clear that when it became larger than .75, local melting of the metal and local melting of the furnace refractory were caused. By controlling X ₀ sinθ / H to be 0.75 or less, the refractory adhered to the furnace body was completely dissolved, and no erosion loss of the refractory body of the furnace was observed. Therefore, if X ₀ sinθ / H is 0.75 or less, it is considered that the secondary combustion heat can be dispersed in the furnace, and the furnace body adhering metal can be efficiently melted.

On the other hand, further experiments revealed that there is an optimum lower limit range for X ₀ sinθ / H. It has been found that when X ₀ sinθ / H is smaller than 0.10, the secondary combustion generation region is too close to the upper blowing lance, so that the upper blowing lance is severely damaged and damaged. Therefore, in order to use the top blowing lance stably, X ₀ sinθ / H needs to be 0.10 or more.

From the above results, it was found that the horizontal distance X ₀ sinθ of the oxygen jet from the sub-hole nozzle needs to be controlled within the range of the following equation (1).

By controlling the number of holes, hole diameter, angle θ, and acid feed rate of the sub nozzle so that X ₀ sin θ / H falls within the range of the formula (1), the furnace body is maintained without impairing the refining ability of the main hole nozzle. It became clear that the adhering metal could be melted throughout the furnace.

  In addition, in order to find the optimum range for the oxygen supply rate from the sub-hole nozzle, experiments and examinations were repeated. As a result of the examination, it has been found that the acid feed rate from the sub-hole nozzle is preferably in the range of 5 to 30% with respect to the acid feed rate from the main hole nozzle. If the acid feed rate from the sub-hole nozzle is less than 5% of the acid feed rate from the main-hole nozzle, the amount of oxygen supplied from the sub-hole nozzle is too small. The gold cannot be dissolved. On the other hand, in the range in which the acid feed rate from the sub-hole nozzle exceeds 30% of the acid feed rate from the main hole nozzle, the secondary combustion amount is excessive, so that the erosion status of the furnace refractory tends to deteriorate. Was recognized.

  Furthermore, it is preferable that the oxygen supply path from the sub-hole nozzle is separated from the oxygen supply path from the main-hole nozzle from the viewpoint of controllability of the oxygen jet from the sub-hole nozzle. There is concern that it will be a little complicated. Thus, an experiment was conducted with the oxygen supply path from the sub-hole nozzle and the oxygen supply path from the main hole nozzle as the same system, but it was found that there was no problem and that this was preferable from the viewpoint of equipment costs. When the oxygen supply path is of the same system, the acid feed rate is determined in proportion to the cross-sectional area ratio of each of the main hole nozzle and the sub hole nozzle.

  The present invention has been made on the basis of these test results, and has an upper blowing nozzle having a nozzle hole for blowing in a vertically downward direction or an obliquely downward direction at the tip thereof, and spaced from the tip by a predetermined interval. When refining hot metal or molten steel by supplying oxygen to the hot metal or molten steel accommodated in the converter-type refining furnace using an upper blowing lance having a horizontal or obliquely downward sub-hole nozzle on the side surface above the lance The flow rate of the oxygen jet from the sub-hole nozzle is controlled so as to satisfy the above-described formula (1), that is, the sub-hole up to the point where the central flow velocity of the oxygen jet ejected from the sub-hole nozzle is reduced to 30 m / s. Oxygen blowing is performed by controlling the horizontal distance from the nozzle outlet to be in the range of 0.10 or more and 0.75 or less of the distance from the center of the top blowing lance to the side wall of the converter type refining furnace. And

  Next, a specific implementation method of the present invention will be described using an example in which the converter type refining furnace shown in FIG. 2 is applied.

  As shown in FIG. 2, the converter-type refining furnace 1 has an outer shell made of an iron shell 3, a refractory 4 is applied to the inside of the iron shell 3, and further inserted into the converter-type refining furnace 1. The upper blow lance 2 made of steel that can move in the vertical direction is provided. On the upper side surface of the converter type refining furnace 1, a hot metal outlet 8 for pouring out the molten iron 8 or the generated molten steel is provided, and a bottom blowing tuyere 6 for injecting a stirring gas is provided in the furnace bottom. It has been. The bottom blowing tuyere 6 is connected to a gas introduction pipe 7. An oxygen gas pipe (not shown) is connected to the top blowing lance 2, and oxygen is supplied from the top blowing lance 2 to the inside of the converter type refining furnace 1 through the oxygen gas pipe at an arbitrary flow rate. It has become so.

  As shown in FIG. 3, the upper blowing lance 2 is composed of a cylindrical lance body 10 and a copper nozzle tip 11 connected to the lower end of the lance body 10 by welding or the like. The outer tube 12, the intermediate tube 13, and the inner tube 14 are composed of three concentric steel tubes, that is, a triple tube. Oxygen is supplied through the inner pipe 14, and the gap between the inner pipe 14 and the middle pipe 13 and the gap between the middle pipe 13 and the outer pipe 12 serve as a cooling water supply / drainage flow path. FIG. 3 is an enlarged view of the upper blowing lance shown in FIG.

  A main hole nozzle 15 for supplying refining oxygen is installed at the tip of the upper blowing lance 2 in a vertically downward direction or an obliquely downward direction, and is connected to the inner pipe 14. The main hole nozzle 15 shown in FIG. 3 is a Laval nozzle composed of two cones, a portion whose cross section is reduced and a portion where the cross section is enlarged, but it may be a straight type nozzle.

  Further, a secondary hole oxygen supply nozzle 16 for supplying secondary combustion oxygen is provided in a horizontal direction or a diagonally downward direction at an upper side surface position spaced apart from the tip of the upper blow lance 2 by a sub hole nozzle. The oxygen for dissolving the metal is supplied through 16. In FIG. 3, the sub-hole nozzle 16 is also connected to the oxygen channel of the inner tube 14, but a dedicated oxygen channel for the sub-hole nozzle 16 may be provided in the upper blowing lance 2. In that case, the top blowing lance has a quadruple tube structure, which is a slightly complicated design. Further, the sub-hole nozzle 16 is a straight type nozzle in FIG. 3, but may have a Laval nozzle shape. However, when the sub-hole nozzle 16 is a Laval nozzle, it is necessary to consider that the process of creating the top blowing lance is slightly complicated. In FIG. 3, the sub-hole nozzle 16 is installed in two steps at a distance from the tip of the lance (two-stage configuration). However, if the design is performed in accordance with the shape of each converter-type refining furnace 1, the effects of the present invention can be sufficiently exerted.

The molten iron 8 is charged into the converter type refining furnace 1 configured as described above, and a slagging agent for forming the slag 9 is charged as necessary, and nitrogen or Ar gas is introduced from the bottom blowing tuyere 6. Oxygen is supplied from the top blowing lance 2 while blowing a gas for stirring. At that time, the horizontal direction distance from the outlet of the sub-hole nozzle to the point where the central flow velocity of the oxygen jet spouted from the sub-hole nozzle 16 is reduced to 30 m / s, that is, the above-described formulas (2) to (4) is obtained. The oxygen blowing is performed by controlling X ₀ sinθ to be within a range of 0.10 to 0.75 of the distance H from the center of the top blowing lance to the side wall of the converter type refining furnace. Since X ₀ sinθ changes by changing the number of holes, hole diameter, angle θ, and acid feed speed of the sub nozzle 13, it can be easily controlled within a predetermined range.

  Oxidation and refining of the decarburization treatment and dephosphorization treatment of the hot metal 8 is performed by the oxygen ejected from the main hole nozzle 15 toward the surface of the hot metal 8, and the hot metal oxidation is performed by the oxygen jet ejected from the sub hole nozzle 16. Secondary combustion of the CO gas generated by refining occurs, the inside of the furnace becomes a high-temperature atmosphere, and the melting of the metal attached to the side wall of the converter-type refining furnace 1 proceeds. In other words, according to the present invention, simultaneously with the refining of hot metal or molten steel, it becomes possible to efficiently melt the metal that has adhered to the converter type refining furnace 1 by the secondary combustion heat throughout the furnace. Here, the decarburization treatment of the hot metal 8 is a treatment for producing molten steel from the hot metal 8 by removing carbon in the hot metal, and the dephosphorization treatment of the hot metal 8 is, for example, 0.04 mass of phosphorus contained in the hot metal. It is a process for producing low phosphorus hot metal by dephosphorization to about%.

  In applying the present invention, the oxygen supply path to the sub-hole nozzle 16 and the oxygen supply path to the main hole nozzle 15 are the same as the top blowing lance (non-independent control), and the top blowing lances (independent control) are different. Control)), no significant difference was found in the dissolution behavior of bullion. Moreover, it has been confirmed that the present invention exhibits a sufficient effect regardless of whether the hot metal preliminary dephosphorization treatment of hot metal having a relatively low processing temperature or the hot metal decarburization treatment having a high acid feed rate.

  An example in which the present invention is applied when carrying out decarburization refining of hot metal in the 300 ton / heat converter type refining furnace shown in FIG. 2 will be described.

  The hot metal used is hot metal that has been subjected to dephosphorization treatment and desulfurization treatment in the hot metal stage, but any hot metal composition can be used. After the hot metal is charged into the converter-type refining furnace, a predetermined amount of the slagging agent is further charged, and a non-oxidizing gas such as nitrogen or a rare gas such as Ar is blown from the bottom blowing tuyere as a stirring gas. Oxygen was supplied from the top blowing lance. Oxygen supplied from the main hole nozzle at the tip of the top lance causes decarburization and refining of the hot metal, and CO gas is generated. The generated CO gas and oxygen supplied from the sub hole nozzle in the process of rising in the converter The secondary combustion reaction occurred.

Table 1 shows a list of experimental levels and results obtained as examples of the present invention and comparative examples. In Table 1, “X ₀ sin θ / H” is an index of the above-described equation (1), and “the oxygen ratio from the sub-hole nozzle” is “the acid feed rate from the sub-hole nozzle / the main hole nozzle. The "acid delivery rate" is expressed as a percentage. In addition, the “melting state of the ingot in the furnace” was evaluated based on the measurement result of the dissolved amount of the ingot in the furnace body after decarburizing and refining continuously with the same top blowing lance. "And the degree of wear of the top blow lance" are also evaluated based on the measurement results after continuous use of the same lance.

In the inventive examples 1 to 7, the blowing conditions and the lance design conditions are controlled in the range where X ₀ sinθ / H is 0.10 or more and 0.75 or less, It was possible to melt evenly in the region and to operate the furnace refractory and the top blowing lance without any problem of wear. On the other hand, in Comparative Examples 1 and 2, X ₀ sin θ / H exceeded 0.75, and there was a portion where the metal remained locally. It was also confirmed that the furnace refractory was melted at locations where the metal was locally melted. This is presumably because the oxygen jet from the sub-hole nozzle had reached near the furnace wall. In Comparative Examples 3 to 4, X ₀ sinθ / H was smaller than 0.10, and although melting of the furnace body adhering metal was good, severe melting damage of the top blowing lance was observed. This is presumably because the secondary combustion region is in the vicinity of the top blow lance.

In Inventive Examples 8 to 15, after controlling X ₀ sinθ / H to a range of 0.10 or more and 0.75 or less, the oxygen ratio from the subhole nozzle was changed to 3 to 35%. The operation was performed. At any level, the ingot in the furnace tended to dissolve well in the whole area, but at the level where the oxygen ratio from the sub-hole nozzle was 3% (Example 8 of the present invention), the amount of dissolved metal was slightly less This is considered to be because the secondary combustion heat could not be sufficiently applied due to a small oxygen supply from the sub-hole nozzle. In addition, at the level where the oxygen ratio from the sub-hole nozzle was 35% (Example 15 of the present invention), although the dissolution of the metal was good, the wear of the furnace refractory tends to deteriorate somewhat. It is thought that the amount of heat generated by secondary combustion was too much. From these results, it was found that the oxygen ratio from the sub-hole nozzle is preferably controlled in the range of 5 to 30%.

  As described above, it was confirmed that by using the present invention, the furnace body adhering metal can be uniformly melted over the entire area of the furnace simultaneously with the refining process without deteriorating the wear of the furnace body refractory and the top blowing lance. As a result, effects such as converter productivity improvement and yield improvement can be obtained.

The cross-sectional schematic in case a subhole nozzle is a Laval nozzle shape is shown. It is a section schematic diagram showing an example of a converter type refining furnace to which the present invention is applied. It is an enlarged view of the top blowing lance shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Converter type refining furnace 2 Top blowing lance 3 Iron skin 4 Refractory 5 Outlet 6 Bottom blowing tuyere 7 Gas introduction pipe 8 Hot metal 9 Slag 10 Lance body 11 Nozzle tip 12 Outer pipe 13 Middle pipe 14 Inner pipe 15 Main hole Nozzle 16 Sub-hole nozzle 17 Laval nozzle 18 Throttle part 19 Throat 20 Skirt part dt Throat diameter de Outlet diameter

Claims (3)

When refining the hot metal or molten steel contained in the converter-type refining furnace by supplying oxygen from the top blowing lance, a main hole nozzle for blowing in the vertically downward direction or diagonally downward direction is arranged at the tip of the top blowing lance. A sub-hole nozzle in a horizontal or diagonally downward direction is disposed on the side surface of the upper blow lance above the upper blow lance at a predetermined distance from the tip of the upper blow lance, and the flow velocity of the oxygen jet ejected from the sub-hole nozzle is (1 ) So that the condition of the formula is satisfied, any of the number of sub-hole nozzles installed, the outlet diameter of the sub-hole nozzle, the throat diameter of the sub-hole nozzle, the inclination angle of the sub-hole nozzle, the acid feed rate from the sub-hole nozzle A refining method in a converter type refining furnace, wherein one or two or more are adjusted and oxygen is supplied from the upper blowing lance.

However, in the equation (1), X ₀ is the distance (m) from the outlet of the sub-hole nozzle to the point where the central flow velocity of the oxygen jet ejected from the sub-hole nozzle is reduced to 30 m / s, and θ is the sub-hole nozzle. The angle between the center line of the top blow lance and the center line of the top blowing lance (deg .: 0 ° <θ ≦ 90 °), and H is from the center of the top blowing lance to the side wall of the converter-type refining furnace And X ₀ can be obtained by the following equations (2), (3), and (4).

In the equations (2) to (4), de is the outlet diameter (mm) of the sub-hole nozzle, V ₀ is the flow velocity (m / s) of the oxygen jet at the sub-hole nozzle outlet, and P ₀ is the sub-hole nozzle diameter. absolute pressure display of the oxygen back pressure hole nozzle ^{(kgf / cm 2), P} e is the absolute pressure indication of the ambient pressure of the converter type refining furnace (kgf / cm ^2: under atmospheric pressure 1.033kgf / cm ² ), F is the acid feed rate (Nm ³ / hr) from the sub-hole nozzle, n is the number of sub-hole nozzles, and dt is the throat diameter (mm) of the sub-hole nozzle.   The refining method in a converter type refining furnace according to claim 1, wherein the acid feed rate from the sub-hole nozzle is in the range of 5 to 30% of the acid feed rate from the main hole nozzle.   The refining method in a converter type refining furnace according to claim 1 or 2, wherein the oxygen supply flow path to the sub-hole nozzle and the oxygen supply flow path to the main hole nozzle are the same.

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