JP7280480B2 - Arc electric furnace, slag discharge method in arc electric furnace, and method for producing molten metal - Google Patents

Description

The present application discloses an electric arc furnace, a method for removing slag in an electric arc furnace, a method for producing molten metal, and the like.

Arc electric furnaces that heat and melt metals using electrical energy are widely used. For example, a solid metal is placed inside an electric arc furnace, and an electric current in the form of an arc is generated between an electrode and a solid metal source to heat the solid metal. Molten metal can be obtained. Alternatively, the molten metal can be maintained in a molten state in the electric furnace by introducing the molten metal into the arc-type electric furnace and heating the molten metal by generating an arc-shaped current between the electrode and the molten metal. can. Here, when the molten metal is heated and held by the electric arc furnace, impurities in the molten metal may rise to the liquid surface of the molten metal. Taking molten steel as an example of the molten metal, impurities in the molten steel mainly rise to the top of the molten steel in the form of oxides, forming slag on the liquid surface of the molten steel. Slag and impurities (hereinafter sometimes referred to as "slag, etc.") floating on the upper part of the molten metal are usually discharged out of the furnace through a slag outlet provided in the electric furnace.

Electric furnaces generally have a large furnace diameter, which tends to reduce the thickness of slag and the like on the liquid surface of the molten metal. In order to efficiently discharge the slag and the like on the surface of the molten metal to the outside of the furnace, it is often the case that component adjustment using a slag-forming material, slag forming using carbon injection, or the like is performed. Conventionally, when discharging slag, etc. on the surface of the molten metal to the outside of the furnace, the furnace body is not tilted, and the slag, etc. is discharged so as to overflow from the slag discharge port (Patent Document 1, etc.). Alternatively, slag or the like has been discharged by tilting the furnace body. That is, it has been common practice to discharge slag and the like by utilizing the potential energy resulting from the difference between the height of the slag surface and the height of the slag outlet.

On the other hand, it is also conceivable to insert a jig for scraping out from the slag outlet and scrape out the liquid surface of the molten metal by human power, machine operation, robot, or the like. This is not easy to install in a large electric furnace, and there are problems such as excessive heat removal and impure gas contamination due to the wide opening of the slag outlet. Operation and installation of robots, etc. have restrictions such as installation locations. Moreover, when it is performed manually, the physical load on the operator is large. It is also conceivable to transfer kinetic energy to slag or the like present on the liquid surface of the molten metal to promote discharge of the slag or the like. For example, referring to the technique disclosed in Patent Document 2, gas may be blown upward inside the electric furnace to push out slag or the like with the gas flow. However, the technology disclosed in Patent Document 2 is a technology for discharging slag from the tundish, and considering the structure of the lid of the electric furnace, the size of the electric furnace, etc., the technology disclosed in Patent Document 2 cannot be used in the electric furnace. It is difficult to apply it as it is to

Japanese Patent No. 3783261 JP-A-8-57599

As described above, when slag or the like is discharged from the slag outlet of an arc electric furnace, conventionally, only the potential energy due to the thickness of the slag or the like can be used, and the slag or the like is discharged at a slow rate. In particular, an arc electric furnace has a large furnace diameter and an electrode, etc., is inserted into the furnace cover, so that the tilt angle is inevitably smaller than that of a converter furnace, which is, for example, several degrees. That is, there is a limit to promoting the discharge of slag and the like by tilting the furnace. In addition, in order to prevent a decrease in metal yield, the metal surface is restricted to a position lower than the slag discharge port. Furthermore, when the thickness of the slag, etc. becomes thin, the flow frictional force acting between the wall surface or the bottom surface of the slag discharge port and the slag, etc., prevents the discharge of the slag, etc. from progressing. is difficult to raise sufficiently.

On the other hand, according to the new findings of the present inventors, the discharge speed of slag, etc. can be sufficiently increased only by blowing gas upward inside the electric arc furnace and imparting kinetic energy to slag, etc. due to the gas flow. can be difficult. Slag, etc. pushed by the gas form a vortex near the slag outlet and move in the direction of escaping from the slag outlet. .

As described above, in arc electric furnaces, there is a new technology that can increase the amount of slag discharged per unit time (discharge rate) and maintain the discharge rate at a high level even when the thickness of slag is thin. is necessary.

As one means for solving the above problems, the present application is capable of heating molten metal and discharging slag or impurities floating on the liquid surface of the molten metal to the outside. at least one slag outlet provided in the side of the electric furnace for discharging the slag or impurities from the interior of the electric furnace to the exterior; at least one gas blowing means installed inside the slag outlet , the gas blowing means having a gas blowing position inside the slag outlet, the gas blowing means In a state where the molten metal is placed inside the furnace, a gas is blown from above the liquid surface of the molten metal to the liquid surface of the molten metal or the slag or impurities existing on the liquid surface of the molten metal. , an electric arc furnace configured to be able to guide the slag or impurities present at the surface of the molten metal to the outlet of the slag outlet.

In the arc electric furnace of the present disclosure, the at least one gas blowing means includes a gas blowing port provided on the upper part of the inner wall of the slag outlet, a lance provided on the upper part of the slag outlet, and the exhaust. It may be at least one selected from burners provided above the slag mouth.

The arc electric furnace of the present disclosure may be configured such that the traveling direction of the gas blown out from the at least one gas blowing means is 15 degrees or more and 60 degrees or less with respect to a horizontal plane.

As one of the means for solving the above problems, the present application heats the molten metal placed inside the arc electric furnace of the present disclosure by arc discharge, and the slag or impurities on the liquid surface of the molten metal and blowing gas from the gas blowing means provided inside the slag outlet to the liquid surface of the molten metal or the slag or impurities present on the liquid surface of the molten metal, a slag exhausting step of guiding the slag or impurities on the liquid surface of the molten metal to the outlet of the slag exhaust port and discharging them to the outside of the electric furnace;
, wherein the gas blowing means has a gas blowing position inside the slag outlet .

In the slag discharge method of the present disclosure, in the slag discharge process, the blowing width W1 of the gas blown out from the gas blowing means may be set to at least half the minimum width W2 of the liquid surface of the molten metal at the slag outlet. good.

As one of the means for solving the above problems, the present application includes a step of discharging slag by the slag discharging method of the present disclosure, and a step of taking out the molten metal inside the electric furnace to the outside. A method of manufacturing metal is disclosed.

According to the technology of the present disclosure, in an arc electric furnace, it is possible to increase the discharge amount (discharge rate) of slag or the like per unit time, and to maintain the discharge rate at a high level even when the thickness of the slag or the like is thin. be.

1 is a schematic diagram for explaining the configuration of an arc electric furnace 100; FIG. FIG. 1(A) is a diagram schematically showing the shape (end surface) in a horizontal cross section, and FIG. 1(B) is a diagram schematically showing the shape (end surface) in the IB-IB vertical cross section of FIG. 1(A). is. 4 is a schematic diagram for explaining the function of gas blowing means 10. FIG. 2 is a schematic diagram for explaining a blowing width W1 of gas blown from a gas blowing means 10; FIG. FIG. 3 is a schematic diagram for explaining the minimum width W2 of the liquid surface of the molten metal at the slag outlet 20; FIG. 4 is a diagram for explaining the flow of the slag removal method S10 in the electric arc furnace 100; FIG. 3 is a schematic diagram for explaining the configuration of arc electric furnaces according to Comparative Examples 1 and 2; FIG. 6A is a diagram schematically showing the shape (end face) in the horizontal cross section, and FIG. 6B is a diagram schematically showing the shape (end face) in the VIB-VIB vertical cross section of FIG. 6A. is. It is a figure which shows one of the water model experiment results. It is a figure which shows one of the water model experiment results. FIG. 3 is a schematic diagram for explaining the configuration of arc electric furnaces according to Examples 3 and 4;

1. Arc Electric Furnace FIG. 1 schematically shows an example of the configuration of an arc electric furnace 100 . As shown in FIG. 1, the arc electric furnace 100 is capable of heating the molten metal 1 by arc discharge, and removes slag or impurities (such as slag 2) floating on the liquid surface of the molten metal 1. It is configured so that it can be discharged to the outside. Specifically, the arc-type electric furnace 100 includes at least one slag outlet 20 provided on the side surface of the electric furnace 100 for discharging the slag or the like 2 from the inside of the electric furnace 100 to the outside, and the slag outlet 20 and at least one gas blowing means 10 installed inside. In a state where the molten metal 1 is arranged inside the electric furnace 100, the gas blowing means 10 blows the liquid surface of the molten metal 1 or slag or the like existing on the liquid surface of the molten metal 1 from above the liquid surface of the molten metal 1. 2 to guide the slag or the like 2 present on the liquid surface of the molten metal 1 to the outlet of the slag outlet 20 .

1.1. gas blowing means 10
The function of the gas blowing means 10 provided in the arc electric furnace 100 will be described with reference to FIG. The gas blowing means 10 blows the liquid surface of the molten metal 1 or slag or the like 2 existing on the liquid surface of the molten metal 1 from above the liquid surface of the molten metal 1 in a state where the molten metal 1 is arranged inside the electric furnace. The slag or the like 2 present on the surface of the molten metal 1 can be guided to the exit of the slag outlet 10 by blowing gas to the slag outlet 10 . For example, the gas blowing means 10 may have gas blowing holes (blowing holes 10a, see FIG. 3). Further, as shown in FIG. 2, the area α where the extended line of the gas blowing hole of the gas blowing means 10 and the liquid surface of the molten metal 1 intersect (the area α where the gas is blown on the liquid surface of the molten metal 1) is the gas blowing area. It is preferable that the gas is blown obliquely downward from the gas blowing means 10 so as to be arranged obliquely below the hole. Furthermore, it is preferable to adjust the orientation of the gas blowing means 10 inside the slag discharge port 20 so that the gas blown out from the gas blowing means 10 is directed toward the outlet of the slag discharge port 20 . As far as the inventors have confirmed, when the traveling direction of the gas blown out from at least one gas blowing means 10 is configured to be 15 degrees or more and 60 degrees or less with respect to the horizontal plane, slag or the like 2 is discharged. Efficiency can be further improved. That is, as shown in FIG. 2(B), the angle θ between the traveling direction of the gas from the gas blowing means 20 and the horizontal plane may be 15 degrees or more and 60 degrees or less.

The gas blowing means 10 may be configured so as to be capable of blowing gas with a predetermined blowing width W1. The "gas blowing width W1" from the gas blowing means 10 will be described with reference to FIG.

In the embodiment shown in FIG. 3A, only one gas blowing means 10 is provided inside the slag outlet 20 for one slag outlet 20 provided in the electric arc furnace 100. , the gas blowing means 10 has a blowing hole 10 a , and the blowing hole 10 a is directed to the exit of the slag outlet 20 . In this case, the horizontal opening length of the blowout hole 10a is defined as "width" or "horizontal width", and the vertical opening length is defined as "height" or "vertical width". The longest opening length in the horizontal direction of the blow-out hole 10a (that is, the longest part of the "lateral width") is defined as the "gas blow-out width W1".

In the form shown in FIG. 3A, the shape of the blowout hole 10a is not particularly limited, and various shapes such as a polygonal shape and a circular shape can be adopted. From the viewpoint of easily increasing the blowing width W1, the gas blowing means 10 may have a wide gas blowing port 10a. In other words, the gas blowing means 10 may have the blowing port 10a whose width is larger than its height. Moreover, the gas blowing means 10 may have a plurality of blowing ports 10a. When the gas blowing means 10 has a plurality of blowing holes 10a in the width direction, a straight line connecting the center of the gas blowing hole 10a arranged at one end in the width direction and the center of the blowing hole 10a arranged at the other end in the width direction is The length of the identified straight line projected onto the horizontal plane is defined as the "gas blowing width W1". When the gas blowing means 10 has a plurality of blowing holes 10a in the height direction, the longest lateral width of the plurality of blowing holes 10a is defined as "gas blowing width W1". When the gas blowing means 10 has a plurality of blowing holes 10a in both directions (including oblique directions) in the width direction and the height direction, the gas blowing holes 10a are arranged at the center of the gas blowing hole 10a arranged at one end in the width direction and at the other end in the width direction. A straight line connecting the center of the blowout hole 10a is specified, a length L1 obtained by projecting the straight line onto a horizontal plane, and a longest length L2 among the widths of the plurality of blowout holes 10a are specified, and L1 and L2 are specified. The longer one of them is defined as "gas blowing width W1".

In the form shown in FIG. 3B, a plurality of gas blowing means 10 are arranged in parallel in the width direction inside one slag outlet 20 provided in the electric arc furnace 100. Each of the plurality of gas blowing means 10 has a blowing hole 10 a , and each blowing hole 10 a is directed to the outlet of the slag discharge port 20 . That is, each gas is blown out from a plurality of gas blowing means 10 , and the direction of each gas is directed toward the exit of the slag outlet 20 . In this case, in the horizontal cross section, from the center (the center of the figure) of the blowout hole 10a of the gas blowout means 10 arranged at the right end toward the slag outlet 20, the center of the blowout hole 10a of the gas blowout means 10 arranged at the left end The length up to (the center of the figure) is defined as "gas blowing width W1". That is, when a plurality of gas blowing means 10 are provided in front of the slag discharge port 20, the center of the blowing hole 10a of the gas blowing means 10 arranged at one end in the width direction and the center of the blowing hole 10a of the gas blowing means 10 arranged at the other end in the width direction A straight line connecting the center of the blowout hole 10a is specified, and the length obtained by projecting the straight line onto the horizontal plane is defined as "gas blowout width W1".

In the form shown in FIG. 3B, the shape of each blowout hole 10a is not particularly limited, and various shapes such as a polygonal shape and an elliptical shape can be adopted. From the viewpoint of easily increasing the blowout width W1, at least one gas blowout means 10 among the plurality of gas blowout means 10 may have a wide gas blowout port 10a. In other words, at least one gas blowing means 10 may have a blowing opening 10a whose width is greater than its height. Moreover, at least one gas blowing means 10 may have a plurality of blowing ports 10a. When the gas blowing means 10 has a plurality of blowing holes 10a, the position of the center of the longer one of L1 or L2 is regarded as the position of the center (the center of the figure) of the blowing holes 10a, and W1 is specified as described above. . In FIG. 3B, the gas blowing directions from the plurality of gas blowing means 10 are directed parallel to each other, but they may not be parallel.

Specific examples of the gas blowing means 10 provided in the arc electric furnace 100 include, for example, a gas blowing port provided on the upper part of the inner wall of the slag outlet 20, a lance provided on the upper part of the slag outlet 20, and At least one selected from the burners provided above the slag outlet 20 can be mentioned. As the gas blowing means 10, a gas blowing port, a lance, and a burner may be used together. The structure of the gas outlet is not particularly limited. For example, there is a form in which a hole is provided in the inner wall of the slag outlet 20 and the gas is blown from the hole to the liquid surface of the molten metal 1 or the slag or the like 2 existing on the liquid surface of the molten metal 1 . For the structure of the lance, for example, the structure of a conventionally known converter top blowing lance may be referred to. The type of gas to be blown out from the gas outlet or the lance inside the electric arc furnace 100 is not particularly limited. For example, the gas outlet or lance may be configured to be able to blow inert gas or nitrogen gas. On the other hand, the structure of the burner may be the same as that of conventionally known burners. A burner is usually configured to be capable of blowing a combustible gas. There are no particular restrictions on the type of combustible gas. When a burner is used as the gas blowing means 10, the temperature of the slag or the like 2 can be raised. Since the viscosity of the slag or the like 2 generally decreases as the temperature rises, the slag or the like 2 can be discharged more efficiently through the slag discharge port 20 by extruding the slag or the like 2 while raising the temperature with a burner. .

The velocity and flow rate of the gas blown out from the gas blowing means 10 are not particularly limited, and may be appropriately determined according to the scale of the electric furnace, the amount of slag or the like 2 to be discharged, and the like.

As described above, the gas blowing means 10 has the function of blowing the gas onto the liquid surface of the molten metal 1 to impart kinetic energy to the slag or the like 2, but may have other functions. For example, it may have a function of blowing a reaction gas or an inert gas into the molten metal 1 .

As shown in FIG. 1, one of the characteristics of the arc electric furnace 100 is that the position of gas blowing by the gas blowing means 10 (for example, the position of the blowing hole) is inside the slag outlet 20 . By upwardly blowing the gas inside the slag discharge port 20 so that the slag or the like 2 moves toward the exit of the slag discharge port 20, the efficiency of discharging the slag or the like 2 is remarkably improved. In the electric arc furnace 100 , at least one gas blowing means 10 may be provided inside at least the slag port 20 . In the electric arc furnace 100, the gas blowing means 10 may be provided inside the electric furnace 100 (for example, see FIG. 6) in addition to the inside of the slag outlet 20. In this case, the gas blowing means provided inside the electric furnace 100 blows the gas from above the liquid surface of the molten metal 1 to the liquid surface of the molten metal 1 or the slag or the like 2 existing on the liquid surface of the molten metal 1. It may be configured to be able to guide the slag or the like 2 existing on the liquid surface of the molten metal 1 to the entrance of the slag outlet 20 provided on the side surface of the electric furnace 100 by spraying. When the gas blowing means 10 is provided inside the electric furnace 100, the gas blowing means 10 may be fixed to, for example, the furnace lid 41 or the side wall 43 of the furnace. The gas blowing means 10 provided inside the electric furnace 100 may have the above blowing width W1.

The gas blowing means 10 does not need to be rigidly fixed inside the slag outlet 20, and may be attached inside the slag outlet 20 so that the gas blowing direction can be changed. For example, the gas blowing means 10 may be rotatably mounted inside the slag outlet 20 .

1.2. slag outlet 20
The shape of the slag outlet 20 in the horizontal section and the minimum width W2 of the liquid surface of the molten metal 1 at the slag outlet 20 will be described with reference to FIG. As shown in FIG. 4A, in the arc electric furnace 100, for example, the opening width is substantially the same from the entrance side (the inside of the electric furnace) to the exit side (the outside of the electric furnace) in the horizontal cross section. A tailings port 20 may be employed. In this case, the "minimum width W2 of the liquid surface of the molten metal 1 at the slag outlet 20" matches the opening widths of the slag outlet 20 on the inlet side and the outlet side.

The shape of the slag discharge port 20 is not limited to the shape shown in FIG. 4(A). For example, the slag port 20 may have a shape that tapers from the inside to the outside of the electric furnace 100 in a horizontal cross section. Specifically, as shown in FIG. 4B, in the slag outlet 20, the opening width Wa on the outlet side (outside the electric furnace) is larger than the opening width Wb on the inlet side (inside the electric furnace). may be narrower. When the shape of the slag port 20 is tapered in this way, the "minimum width W2 of the liquid surface of the molten metal 1 at the slag port 20" must match the opening width Wa of the slag port 20 on the exit side. Become.

Alternatively, the slag outlet 20 may have a shape that tapers from the inside to the outside of the electric furnace 100 in a horizontal cross section. Specifically, as shown in FIG. 4C, in the slag port 20, the opening width Wb on the inlet side (inside the electric furnace) is larger than the opening width Wa on the outlet side (outside the electric furnace). may be narrower. In this case, the "minimum width W2 of the liquid surface of the molten metal 1 at the slag outlet 20" matches the opening width Wb of the slag outlet 20 on the inlet side.

The relationship between the opening width Wa on the outlet side of the slag outlet 20, the opening width Wb on the inlet side, and the length L of the slag outlet 20 (horizontal distance between the inlet side opening and the outlet side opening) is particularly limited. not a thing The length L of the slag outlet 20 is generally equal to or greater than the thickness of the side wall 43 of the electric furnace. Depending on the arrangement of the slag door 21 and the movable range of a pot (not shown) that receives the discharged slag, etc., the slag outlet 20 may be installed so as to protrude from the outer wall of the electric furnace. is longer than the thickness of the side wall 43 .

The shape of the opening on the inlet side and the shape of the opening on the outlet side of the slag discharge port 20 are not particularly limited. Various shapes such as a polygonal shape and a circular shape can be adopted as the shape of the opening when viewed from the front. The specific values of the opening widths Wa and Wb, the opening height and the length L of the slag outlet 20 are not particularly limited, and are appropriately determined according to the scale of the electric arc furnace 100, the thickness of the side wall 43, and the like. be able to.

In FIG. 1, the inlet side and the outlet side of the slag outlet 20 have substantially the same height in the horizontal direction, but the form of the slag outlet 20 is not limited to this. The height of the inlet side of the slag discharge port 20 may be higher than the height of the outlet side, or the height of the inlet side of the slag discharge port 20 may be lower than the height of the outlet side. You may

In FIG. 1, the shape of the inner wall of the slag outlet 20 is flat (straight in both horizontal and vertical sections), but the form of the slag outlet 20 is limited to this. not something. The shape of the inner wall of the slag discharge port 20 may be curved (curved in at least one of the horizontal and vertical sections). In addition, the slag outlet 20 may have unevenness on the inner wall.

Although FIG. 1 shows a mode in which only one slag outlet 20 is provided on the side surface of the electric furnace, the number of slag outlets 20 is not limited to one. It is also possible to set the number of the slag outlets 20 to two or more according to the scale of the electric arc furnace 100 or the like.

The position of the slag outlet 20 on the side of the electric furnace is not particularly limited. Depending on the position of the slag outlet 20, the amount of the molten metal 1 to be placed inside can be determined.

1.3. Other Configurations The arc-type electric furnace 100 may be provided with the gas blowing means 10 and the slag outlet 20 described above, and the configuration other than this may be the same as the conventional one. As described above, the arc electric furnace 100 has a space in which molten metal is arranged. Here, a fire-resistant wall made of fire-resistant blocks may be formed on the inner wall of the space to protect the outer wall. In addition to the fireproof wall, it is also common to install a cooling panel member that protects the outer wall by circulating cooling water inside.

As shown in FIG. 1, an electric furnace ceiling member (furnace lid) 41 is connected to the upper portion of the electric arc furnace 100, which covers the open upper portion and has an electrode 30 for generating arc heat. Although not shown, the electric furnace ceiling member 41 includes an exhaust pipe for discharging a large amount of waste gas and dust generated in the melting and refining processes, an inlet for introducing a solid metal source and secondary materials, and other items. piping or the like may be connected. In the electric arc furnace 100, an electric current in the form of an arc is generated between the electrode 30 and solid metal or molten metal to heat and melt the solid metal or heat and hold the molten metal.

As shown in FIG. 1, in the electric arc furnace 100, a structure that can be opened and closed, that is, a slag door 11, may be provided at the slag discharge port 20 for slag discharge control and furnace atmosphere control. Alternatively, the slag door 11 may not be used, and an open slag discharge port 20 may be used.

As shown in FIG. 1, in the arc electric furnace 100, an outlet 42a may be provided in the furnace bottom 42 to allow the molten metal to flow out. Alternatively, the furnace bottom 42 may not have the outlet 42a, and the molten metal may flow out by tilting. The same applies to the case of tilting the furnace body when discharging the slag or the like 2, but if the tilting angle of the furnace body is large, installation of equipment associated with the electric furnace 100 such as the electrode 30 becomes difficult. It is preferable that the tilting angle of the furnace body when discharging the slag or the like 2 is 10 degrees or less compared to that during operation (during arc discharge).

In FIG. 1, a plurality of electrodes 30 are drawn assuming an AC electric furnace, but the arc electric furnace 100 is not limited to an AC electric furnace and may be a DC electric furnace. In this case, the number of electrodes 30 may be one or plural.

2. Slag Discharge Method in Arc Electric Furnace The technology of the present disclosure also has an aspect as a slag removal method in an arc electric furnace. FIG. 5 shows the flow of the slag discharge method S10 in the arc electric furnace 100. As shown in FIG. As shown in FIG. 5, the slag removal method S10 heats the molten metal 1 placed inside the arc electric furnace 100 by arc discharge, and floats the slag or the like 2 on the liquid surface of the molten metal 1. , a surfacing step S1, and blowing gas from a gas blowing means 10 provided inside the slag outlet 20 to the liquid surface of the molten metal 1 or the slag or the like 2 existing on the liquid surface of the molten metal 1, so that the molten metal 1 and a slag discharge step S2 for guiding the slag or the like 2 on the liquid surface of the furnace to the exit of the slag discharge port 20 and discharging it to the outside of the electric furnace 100.

2.1. Floating step S1
In the slag discharge method S10 of the present disclosure, in the floating step S1, the molten metal 1 placed inside the arc electric furnace 100 as described above is heated by arc discharge. “Molten metal placed inside the arc electric furnace” means molten metal obtained by storing a solid metal inside the arc electric furnace 100 and then melting the solid metal by arc discharge, or The molten metal is placed so that the molten metal is poured into the arc electric furnace 100, or the solid metal is put into the furnace holding the molten metal and then the solid metal is melted by arc discharge. It includes various forms such as molten metal. The molten metal 1 may contain impurities as long as the slag or the like 2 can float on the surface of the liquid. Examples of such molten metal 1 include molten steel, various iron alloys including stainless steel, and nickel. Molten steel with slag formation is particularly preferred. Since the conditions for heating the molten metal by arc discharge are the same as in the conventional art, detailed explanations are omitted here.

In the levitation step S1, the molten metal 1 as described above is heated by arc discharge, and slag or the like 2 is levitated on the surface of the molten metal 1. As shown in FIG. For example, by continuing to heat the molten metal, the slag or the like 2 naturally rises to the surface of the molten metal 1 and a layer of the slag or the like 2 can be formed on the liquid surface of the molten metal 1 . The slag or the like 2 may exist as a continuous layer over the entire liquid surface of the molten metal 1, or may exist dispersedly in some places on the liquid surface.

2.2. Waste disposal process S2
In the slag discharge step S2, the gas blowing means 10 installed inside the slag outlet 20 removes the liquid surface of the molten metal 1 or slag existing on the liquid surface of the molten metal 1 from above the liquid surface of the molten metal 1. By blowing gas onto the molten metal 1 and the like 2 , the slag and the like 2 existing on the liquid surface of the molten metal 1 is guided to the outlet of the slag outlet 20 and discharged to the outside of the electric furnace 100 . "Blowing gas to the liquid surface of the molten metal 1 or to the slag or the like 2 existing on the liquid surface of the molten metal 1" means blowing the gas only to the liquid surface of the molten metal 1, blowing the gas only to the slag or the like 2. It is a concept that includes both the form and the form in which the gas is blown to both the liquid surface of the molten metal 1 and the slag 2 or the like. In particular, a mode of blowing gas onto at least the slag or the like 2 existing on the liquid surface of the molten metal 1 (a mode of blowing the gas only on the slag or the like 2, and a mode of blowing the gas on both the liquid surface of the molten metal 1 and the slag or the like 2) ). Here, according to the new findings of the present inventor, when discharging slag and the like on the surface of the molten metal through the slag discharge port 20, if gas is blown upward inside the electric furnace, the molten metal Even if the kinetic energy of the gas flow is applied to the slag, etc. on the liquid surface, it may be difficult to sufficiently increase the discharge speed of the slag, etc. discharged from the slag outlet. Slag, etc. pushed by the gas form a vortex near the slag outlet and move in the direction of escaping from the slag outlet. . As a result of earnest research, the present inventor found that the slag discharge efficiency of the electric arc furnace 100 changes depending on the location of gas blowing. Specifically, according to the new knowledge of the present inventors, compared to the case where the gas blowing means 10 is installed inside the electric furnace 100, when the gas blowing means 10 is installed inside the slag outlet 20 , the slag or the like 2 can be efficiently extruded from the slag outlet 20 to the outside of the electric furnace 100, and the slag or the like 2 inside the electric furnace 100 can be efficiently attracted to the inside of the slag outlet 20. It is possible to remarkably improve the efficiency of discharging the slag 2 and the like. In particular, in the slag discharge step S2, the direction of the gas blown from the gas blowing means 10 is directed toward the outlet of the slag outlet 20, and the blowing width W1 of the gas from the gas blowing means 10 is set to the slag outlet 20. When it is half or more (50% or more) of the minimum width W2 of the liquid surface of the molten metal 1 in , the efficiency of discharging the slag or the like 2 is further significantly improved. Note that "the direction of the gas blown out from the gas blowing means 10 is directed toward the outlet of the slag outlet 20" means that the traveling direction of the gas blown out from the gas blowing means 10 has a horizontal component and a vertical component. , it means that the outlet of the slag outlet 20 exists on the extension of the horizontal component. It is not necessary for the gas blown out from the gas blowing means 10 to reach the outlet of the slag outlet 20 .

In the slag discharge step S2, as described above, the blowing width W1 of the gas from the gas blowing means 10 is preferably half or more (50% or more) of the minimum width W2 of the liquid surface of the molten metal 1 at the slag discharge port 20. . More preferably, the blowout width W1 is 60% or more of the minimum width W2. The upper limit of the blowout width W1 with respect to the minimum width W2 is not particularly limited. For example, the blowout width W1 can be set to 120% or less of the minimum width W2.

In the slag discharge step S2, the flow rate of the gas from the gas blowing means 10 may be appropriately adjusted according to the scale of the electric furnace 100 and the like. For example, a unit furnace area sprayed on the liquid surface of the molten metal 1, a gas flow rate per unit time (that is, a flow rate normalized by the surface (upper surface) area of the molten metal in the furnace per unit time ) may be 1 to 100 Nm ³ /h/m ² . In addition, from the viewpoint of suppressing melting damage of the gas blowing means 10 and blowing the gas more efficiently by the liquid surface of the molten metal 1, in the slag exhausting step S2, the gas blowing position of the gas blowing means 10 is set to the liquid level of the molten metal 1. The height from the surface may be 0.1 m or more and 2.0 m or less.

In the above description, steps S1 and S2 were explained independently, but these steps may be performed simultaneously, or their order may be changed or partly repeated.

3. Method for Producing Molten Metal The technology of the present disclosure also has an aspect as a method for producing molten metal. That is, the molten metal production method of the present disclosure includes a step of performing slag removal by the above-described slag removal method S10, and a step of taking out the molten metal 1 inside the electric furnace 100 to the outside. The molten metal 1 inside the electric furnace 100 may be taken out through the outlet 42a of the furnace bottom 42 of the electric furnace 100, for example, as described above. Alternatively, the molten metal 1 may flow out by tilting the furnace body.

In a conventional arc electric furnace, when discharging slag, etc. existing on the liquid surface of the molten metal to the outside through a slag outlet provided on the side of the electric furnace, the height of the slag surface and the slag outlet It used the potential energy due to the difference in height. However, in such a form, there was a problem that the discharge speed of slag was slow. In order to solve this problem, the inventor of the present invention has the idea of blowing gas onto the liquid surface of the molten metal using a gas blowing means (for example, a top blowing lance) to give kinetic energy to the slag, etc., thereby facilitating the discharge of the slag, etc. The effect was confirmed by a water model experiment. As a result, although gas blowing accelerates the discharge of slag and the like, there are cases where the discharge rate of slag and the like cannot be sufficiently increased depending on the conditions of gas blowing (position of gas blowing). It is thought that the reason for this is that the slag, etc. pushed by the gas move in the direction of escaping from the slag outlet, and the given kinetic energy is not efficiently utilized for the discharge flow. Therefore, the present inventors have studied the gas blowing conditions so that the kinetic energy given by the gas is efficiently utilized for discharging slag and the like. As a result, by blowing gas inside the slag outlet, it is possible to increase the flow rate of slag, etc., toward the outlet of the slag outlet, while suppressing the backflow of slag, etc. in the slag outlet. The inventors have found that the kinetic energy generated can be efficiently used for discharging slag and the like. Hereinafter, the effects of the technique of the present disclosure will be described in more detail with reference to examples. An example shown below shows an example of the technology of the present disclosure. The technology of the present disclosure is not limited to the examples shown below.

In the following examples, the case of using a top-blowing lance as the gas blowing means will be exemplified. In the following embodiments, for convenience of explanation, a lance with a circular or regular polygonal outlet is referred to as a "narrow lance", and a wide lance with a rectangular or elliptical outlet is referred to as a "wide lance". shall be referred to as

1. Water Model Experiment A water model experiment was conducted using a simulated electric furnace vessel with a furnace diameter of 70 cm and variously changing the shape of the lance (blowing width W1) and the position of the lance. In the water model experiment, salt water (specific gravity 1.15 g/cm ³ ) was used as a simulated metal fluid, silicone oil (specific gravity 0.965 g/cm ³ ) was used as a simulated slag fluid, and the slag thickness at the liquid surface was 50 mm. bottom. The width W2 of the slag outlet in the water model experiment was fixed at 200 mm, and the traveling direction of the gas blown out from the lance was set at 60 degrees with respect to the horizontal plane.

As a result of the water model experiment, it was found that the slag flow velocity near the point where the gas hits the slag increases by blowing the gas. This is the same effect as described in Patent Document 2. However, the increase in discharge rate due to the increase in slag flow rate was not necessarily large. When the width of the flow path changes rapidly at the slag outlet, the pushed slag flow cannot enter the slag outlet, and escapes or reverses in the lateral direction near the entrance of the slag outlet, forming a vortex and discharging. This is thought to be because it may interfere with

1.1. Regarding the lance installation location As shown in Fig. 1, the lance is installed inside the slag outlet and the gas is blown upward, and as shown in Fig. 6, the lance is installed inside the electric furnace and the gas It was confirmed whether or not the slag discharge efficiency changed between the case of blowing and the case of blowing. The results are shown in FIG. In FIG. 7, "wide lance" is the case of using a lance having a rectangular blowing hole with a vertical width of 1.5 mm and a width W1 of 100 mm (W1/W2=0.5). "Multiple lances" is a case in which a plurality of lances with an inner diameter of 5 mm are arranged at intervals of 20 mm (W1/W2=0.5). 05) is used. The vertical axis in FIG. 7 represents the residual thickness (mm) of the slag in the simulated electric furnace vessel after 5 minutes from the start of the slag discharge.

As is clear from the results shown in FIG. 7, regardless of the blowout width W1 of the lance, the lance is installed inside the slag outlet more than when the lance is installed inside the electric furnace and the gas is blown upward. The slag discharge efficiency was remarkably improved when the gas was blown upward.

1.2. Regarding the relationship between W1 and W2 Next, on the premise that a lance is installed inside the slag outlet and the gas is blown upward, an experiment was conducted by changing the blowing width W1 of the lance. As a result of the experiment, by increasing the blowing width W1 of the lance and pushing out the slag widely toward the outlet of the slag outlet, the back flow of slag from the slag outlet is reduced even if the opening width W2 of the slag outlet is the same. It was found that the gas blowing energy was used more efficiently for the tailings. FIG. 8 and Table 1 below show changes in the slag removal efficiency when W1/W2 is changed in the water model experiment. FIG. 8A shows the case where the total gas flow rate is constant, and FIG. 8B shows the case where the gas flow rate per unit area of the blow-out hole is constant. In FIG. 8 and Table 1, "wide lance" is the case of using a lance having a rectangular blowout hole with a vertical width of 1.5 mm and a width of W1. A "narrow lance" is a case in which a plurality of lances with an inner diameter of 5 mm are arranged at intervals of 20 mm, and a lance with an inner diameter of 10 mm is used. In addition, "narrow lance" and "wide lance" in FIG. 8 and Table 1 refer to the case where one lance is installed inside one slag outlet as shown in FIG. This is the case where a plurality of lances are arranged side by side in the width direction inside one slag discharge port as shown in FIG. 3(B). The vertical axis in FIG. 8 represents the residual thickness (mm) of the slag in the simulated electric furnace vessel after 5 minutes from the start of the slag discharge.

As shown in FIG. 8 and Table 1, even when the total gas flow rate is constant and when the gas flow rate per unit area of the blowout hole (≈flow velocity) is constant, when W1/W2≧0.5 The slag removal efficiency was further improved. That is, it can be said that the slag discharge efficiency can be further improved by increasing the width of the blowout hole of the lance installed inside the slag discharge port or the installation width of the plurality of lances.

2. Actual machine test (Example 1)
The pellets were reduced in a shaft furnace to produce DRI with a reduction rate of 90%. Next, 100 tons of this DRI is charged into the DC electric furnace described above (width of slag W2 = 1.0 m, see Fig. 4A) on a scale of 100 tons, and 10 tons of coal is used as a reducing agent to melt and Reduction was performed to produce hot metal with [C] = 3.5 mass% and a temperature of 1400°C. At this time, an arc was generated using the upper electrode as a cathode and the lower electrode as an anode, and quicklime was added so that the slag basicity was 1.3. The S concentration in the produced hot metal was 0.0033 mass%, and the S concentration in the slag was 0.33 mass%.

The slag amount M1 after the completion of dissolution and reduction of DRI was 19.5 t. A wide lance (W1/W2=0.6) installed at the upper part of the slag outlet of the DC electric furnace was lowered and arranged as shown in FIGS. 1 and 3(A). N ₂ gas was blown to the slag surface at 26 Nm ³ /h/m ² (unit furnace area, flow rate per unit time, hereinafter the same) so that the slag was directed to the outlet of the slag outlet, and slag was discharged for 5 minutes. . As a result, the discharged slag amount M2 was 12.5t, and the slag removal rate was 64% from the ratio of M1 and M2.

(Example 2)
Hot metal was produced under the same conditions as in Example 1, and the amount of slag M1 after the completion of dissolution and reduction of DRI was 23 t. A plurality of lances (3 lances, W1/W2=0.6) installed above the slag outlet of the DC electric furnace were lowered to arrange the lances as shown in FIG. 3(B). N ₂ gas was blown to the slag surface at 26 Nm ³ /h/m ² so that the slag was directed toward the slag outlet, and slag was discharged for 5 minutes. As a result, the discharged slag amount M2 was 13.5t, and the slag removal rate was 59% from the ratio of M1 and M2.

(Example 3)
Hot metal was produced under the same conditions as in Example 1, and the amount of slag M1 after the completion of dissolution and reduction of DRI was 21 t. As shown in FIG. 9, N ₂ Gas was blown onto the slag surface at 26 Nm ³ /h/m ² and slag was performed for 5 minutes. As a result, the discharged slag amount M2 was 12.5t, and the slag removal rate was 60% from the ratio of M1 and M2.

(Example 4)
Hot metal was produced under the same conditions as in Example 1, and the amount of slag M1 after the completion of dissolution and reduction of DRI was 22 t. As shown in FIG. 9, three gas outlets (W1/W2=0.6 (W1 is From the identification by the method shown in FIG. 3(B))), N ₂ gas was sprayed on the slag surface at 26 Nm ³ /h/m ² and slag was discharged for 5 minutes. As a result, the discharged slag amount M2 was 13 tons, and the slag removal rate was 59% from the ratio of M1 and M2.

(Example 5)
Hot metal was produced under the same conditions as in Example 1, and the amount of slag M1 after the completion of dissolution and reduction of DRI was 20 t. A narrow lance (W1/W2=0.06) installed above the slag outlet of the DC electric furnace was lowered to form a lance arrangement as shown in FIG. 3(A). N ₂ gas was blown to the slag surface at 26 Nm ³ /h/m ² so that the slag was directed toward the slag outlet, and slag was discharged for 5 minutes. As a result, the discharged slag amount M2 was 11t, and the slag removal rate was 55% from the ratio of M1 and M2.

(Comparative example 1)
Hot metal was produced under the same conditions as in Example 1, and the amount of slag M1 after the completion of dissolution and reduction of DRI was 20 t. A wide lance (W1/W2=0.6) installed in the upper part of the DC electric furnace described above was lowered to form a lance arrangement as shown in FIG. N ₂ gas was blown to the slag surface at 26 Nm ³ /h/m ² so that the slag was directed toward the slag outlet, and slag was discharged for 5 minutes. As a result, the discharged slag amount M2 was 10.5t, and the slag removal rate was 53% from the ratio of M1 and M2.

(Comparative example 2)
Hot metal was produced under the same conditions as in Example 1, and the amount of slag M1 after the completion of dissolution and reduction of DRI was 20.5 t. A narrow lance (W1/W2=0.06) installed in the upper part of the DC electric furnace described above was lowered to form a lance arrangement as shown in FIG. N ₂ gas was blown to the slag surface at 26 Nm ³ /h/m ² so that the slag was directed toward the slag outlet, and slag was discharged for 5 minutes. As a result, the discharged slag amount M2 was 9t, and the slag removal rate was 44% from the ratio of M1 and M2.

(Comparative Example 3)
Hot metal was produced under the same conditions as in Example 1, and the amount of slag M1 after the completion of dissolution and reduction of DRI was 20 t. The slag was exhausted for 5 minutes without gas blowing by the lance. As a result, the discharged slag amount M2 was 8.5t, and the slag removal rate was 43% from the ratio of M1 and M2.

The experimental conditions and experimental results of Examples 1 to 5 and Comparative Examples 1 to 3 are summarized in Table 2 below.

In Comparative Example 3, which has the same form as the conventional form, the slag removal rate was 43%. % rose slightly. However, in both Comparative Examples 2 and 3, the slag removal rate did not exceed 50%.

As in Comparative Example 1, as a result of performing top blowing with a wide lance inside the electric furnace, the slag removal rate increased to 53%. It has been found that it is necessary to increase the blowing width of the gas in order to achieve a sufficient slag removal rate when the gas is top-blown inside the electric furnace.

On the other hand, as in Examples 1 to 5, when the lance is installed inside the slag outlet and the gas is blown upward, the slag discharge rate is 55% or more even if the blowing width of the lance is narrow, and the comparative example Remarkable slag improvement effect was confirmed as compared with 1 to 3. In addition, the slag removal rate could be further improved by increasing the blowing width of the lance, as in the case of installing a lance inside the electric furnace and blowing the gas upward.

In addition, in the above-described embodiment, an embodiment in which slag is discharged while producing molten steel in the electric arc furnace was illustrated, but the technique of the present disclosure is not limited to this embodiment. A similar effect can be expected even when a molten metal other than molten steel is produced.

1 molten metal 2 slag or impurities 10 gas blowing means 20 slag outlet 21 slag door 30 electrode 41 furnace lid (ceiling member)
42 Furnace bottom 42a Molten metal outlet 43 Side wall 100 Arc electric furnace

Claims (6)

An arc electric furnace configured to be able to heat molten metal and to discharge slag or impurities floating on the liquid surface of the molten metal to the outside,
At least one slag outlet provided on the side surface of the electric furnace for discharging the slag or impurities from the inside of the electric furnace to the outside, and at least one gas outlet provided inside the slag outlet. means and
The gas blowing means has a gas blowing position inside the slag outlet,
When the molten metal is placed inside the electric furnace, the gas blowing means blows out the slag existing on the liquid surface of the molten metal or on the liquid surface of the molten metal from above the liquid surface of the molten metal. Alternatively, it is configured to be able to guide the slag or impurities present on the liquid surface of the molten metal to the outlet of the slag outlet by blowing gas onto the impurities.
Arc electric furnace. The at least one gas blowing means includes a gas blowing port provided at the upper part of the inner wall of the slag outlet, a lance provided at the upper part of the slag outlet, and a burner provided at the upper part of the slag outlet. is at least one selected from
The arc electric furnace according to claim 1. The traveling direction of the gas blown out from the at least one gas blowing means is configured to be 15 degrees or more and 60 degrees or less with respect to a horizontal plane.
The arc electric furnace according to claim 1 or 2. A surfacing process in which the molten metal placed inside the arc electric furnace according to any one of claims 1 to 3 is heated by arc discharge to float the slag or impurities on the liquid surface of the molten metal. and,
Gas is blown from the gas blowing means provided inside the slag outlet to the liquid surface of the molten metal or the slag or impurities present on the liquid surface of the molten metal, thereby a slag exhausting step of guiding the slag or impurities to the exit of the slag exhaust port and discharging it to the outside of the electric furnace;
with
The gas blowing means has a gas blowing position inside the slag outlet,
A slag removal method in an electric arc furnace. In the slag discharge step, the blowing width W1 of the gas blown out from the gas blowing means is set to be at least half of the minimum width W2 of the liquid surface of the molten metal at the slag outlet.
The waste disposal method according to claim 4. A step of performing waste disposal by the waste disposal method according to claim 4 or 5;
A step of taking out the molten metal inside the electric furnace to the outside;
comprising
Method for producing molten metal.

Images