JP6429190B2 - Electric furnace for melting steelmaking slag - Google Patents

Description

  The present invention relates to an electric furnace for melting treatment of steelmaking slag, and more particularly to an electric furnace for smelting reduction treatment of steelmaking slag having a furnace wall composed of an iron skin on the outside and a refractory brick wall on the inside.

In recent years, a method for recovering valuable materials by melting and reducing steelmaking slag generated in various kilns such as hot metal pretreatment furnaces, converters, electric furnaces, degassing furnaces, and adjusting and modifying slag components Has been developed. Steelmaking slag contains 5 mass%-40 mass% of FeO, for example, and C / S is about 1-4. Here, C / S represents the ratio of CaO to SiO _{2 in} the slag (CaO / SiO ₂ ) and is also called basicity. As a method of smelting reduction treatment of such steelmaking slag, for example, a method using a smelting reduction furnace described in Patent Document 1 or an arc electric furnace described in Patent Document 2 is known.

According to the example of the conventional technology as described above, the DC arc electric furnace for smelting and reducing steelmaking slag is inserted from the slag inlet, the tap, the tap, the furnace lid, and the center of the furnace lid. And a charging furnace for holding the steelmaking slag in a molten state is connected to the inlet of the slag. In the smelting reduction treatment, molten slag is intermittently charged from a charging furnace into a DC arc electric furnace, and a reducing material and a slag modifier are added while arc melting. The molten iron containing iron recovered from the slag is discharged from the tap at the bottom of the furnace, and the slag whose components are adjusted is discharged from the tap. The slag component adjustment is performed, for example, so that FeO is 1% by mass or less and C / S is about 0.5 to 1.5 depending on the use of slag. Here, MgO—Cr ₂ O ₃ brick is generally used for the refractory brick wall of the conventional DC arc electric furnace. Since C / S fluctuates greatly during the slag smelting reduction treatment, MgO—Cr ₂ O ₃ brick, which has excellent corrosion resistance against both high C / S and low C / S slag, is advantageous.

  On the other hand, Patent Document 3 describes a three-phase AC arc furnace for melting metal, which has a furnace wall composed of an iron skin on the outside and a refractory brick wall on the inside, for melting raw materials such as metal scrap. In the technique described in Patent Document 3, the furnace wall of the hot spot portion, which is a location where slag melts in a three-phase AC arc furnace, is cooled by a refrigerant generating means that generates a refrigerant composed of water mist and air. At this time, the refractory brick in the hot spot portion is made refractory brick made of MgO-C refractory having a carbon content of 30% by mass to 50% by weight, thereby enabling efficient cooling. As a result, damage to the MgO—C refractory can be suppressed, and its durability can be greatly improved.

  In addition to the electric furnace, a converter is an example of a kiln that requires corrosion resistance to steelmaking slag. A refractory brick made of an MgO—C refractory having a graphite content of 20% by mass or less is generally used for the furnace wall at the portion of the converter that contacts the slag. Here, according to Patent Document 4, in the MgO-C refractory, when the graphite content is high, the spall resistance and the dissolution resistance of MgO are improved, while the oxidation resistance to FeO in the steelmaking slag is The overall wear of the brick increases because it becomes lower. In Non-Patent Document 1, because of the above-described properties, the portion that contacts the slag in the converter has a refractory brick made of an MgO—C refractory having a graphite content of 11% by mass to 15% by mass. Is described as lining construction.

JP 2014-105915 A JP 2013-124417 A JP-A-11-223464 JP 2005-214548 A

Proceedings INFACON X, “Transformation through Technology”, pp. 466-476, 2004

When processing steelmaking slag, the conventional refractory brick wall, MgO-Cr ₂ O ₃ brick, is advantageous in terms of corrosion resistance. However, when the slag component is adjusted and modified, the refractory brick wall This causes a problem that the Cr ₂ O ₃ concentration in the slag increases due to the melting damage.

  On the other hand, in Patent Document 3, a refractory brick made of MgO-C refractory having a carbon content of 30 to 50% by weight is used on the furnace wall of the hot spot portion of the AC electric furnace, and this is used as a water mist. And it cools with the refrigerant | coolant generating means which generate | occur | produces the refrigerant | coolant which consists of air. Since the amount of slag is small in the furnace for melting metal scrap, the wear of the furnace wall bricks in the hot spot part has become a high temperature exceeding 2000 ° C. due to radiation. It is considered that this is a MgO—C reaction that disappears upon reaction. Wear due to this reaction occurs depending on the temperature of the brick regardless of the presence or absence of molten slag or molten metal, and is reduced by setting the temperature of the brick to about 1700 ° C. or less.

  However, in a DC electric furnace for steelmaking slag treatment, the amount of slag is large, the amount of FeO contained in the slag is large (for example, 5 mass% to 40 mass%), and the C / S of the slag is also high (for example, 1-4). Furnace wall brick wear is caused by oxidation and melting of brick by steelmaking slag. Therefore, even if the refrigerant generating means for generating the refrigerant composed of water mist and air as in Patent Document 3 is used, the cooling effect is not sufficient because the heat transfer coefficient is small. In other words, a DC electric furnace for steelmaking slag treatment can cool the furnace wall brick using such a refrigerant generating means, but the refractory brick in contact with the slag exceeding 1600 ° C. is used for cooling the wall. Is not sufficient, and therefore wear of bricks in contact with the slag cannot be suppressed. Therefore, it is difficult to apply the technique of Patent Document 3 to a DC electric furnace for steelmaking slag treatment.

  On the other hand, the slag generated in the converter, like the slag handled by the DC electric furnace for steelmaking slag treatment, contains much FeO contained in the slag (for example, 5 mass% to 40 mass%), and the C / S of the slag is also high. . However, since the converter is an open-air furnace, unlike a closed DC electric furnace, the furnace wall has a low graphite content of 20% by mass or less MgO− with an importance on oxidation resistance. Refractory bricks made of C-based refractories are used. As described above, a technique for improving the durability by suppressing the wear of the furnace wall brick in a DC electric furnace for steelmaking slag treatment has not yet been proposed.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to level out the wear of work bricks in each part constituting the refractory brick wall in a DC electric furnace for steelmaking slag. It is an object of the present invention to provide a new and improved electric furnace for melting treatment of steelmaking slag, which can be improved in durability.

When steelmaking slag is melted in a DC electric furnace, FeO in the slag mainly reacts with a reducing material containing carbonaceous matter, and FeO is reduced to Fe. Further, the addition of slag modifier consisting mainly of SiO ₂ or the like and _Al 2 _{O 3,} C / S of the slag is adjusted to about 0.5 to 1.5. As described above, when MgO—Cr ₂ O ₃ brick having excellent corrosion resistance is used for the wall of a DC electric furnace, Cr ₂ O ₃ may be eluted, which may affect the slag reforming as described above. . Therefore, the present inventors examined the possibility of an MgO—C brick as a brick that can replace the MgO—Cr ₂ O ₃ brick.

  When the FeO in the slag comes into contact with the MgO-C brick, it reacts with the graphite in the brick and is reduced, and the brick is worn with this reduction. MgO-C bricks have corrosion resistance if the C / S of the slag is high, but are inferior in corrosion resistance to slag modifiers, low C / S steelmaking slag, and slag after modification. Therefore, MgO-C brick is not usually used in a DC electric furnace for steelmaking slag.

  However, the present inventors have formed a solidified layer of slag on the brick surface by cooling the back surface of the MgO-C brick, so that FeO in the slag, slag modifier, low C / S steelmaking slag and modification It has been found that wear due to later slag can be reduced. The present inventors further reduced the wear due to the solidified layer when MgO—C brick having a graphite content of 30% by mass to 50% by mass was used, and when the strong cooling by water cooling was performed as a cooling method for the back of the brick. It was found that it was realized well.

  Suppression of the wear of the furnace wall bricks using the solidified layer of slag as described above is very effective for improving the durability. However, in order to realize this, it is necessary to cool the working surface of the work brick at the part in contact with the molten slag to be equal to or lower than the solidification start temperature of the slag. Water cooling is effective as a cooling means for this purpose, but if the work brick is uniformly water cooled, the work brick in the part that contacts the metal (metal part) and the part that does not contact the melt (free board part) As for bricks, even if they are not cooled, wear due to melting damage is small, so excessive cooling results in heat loss.

  Therefore, after making the back surface of the entire work brick a water-cooled structure, the work brick at the portion in contact with the slag is made to have high thermal conductivity by increasing the graphite content, thereby improving the slag resistance and the cooling effect. On the other hand, for the work bricks other than the part in contact with the slag, the thermal conductivity is lowered by lowering the graphite content to some extent, and the heat loss due to excessive water cooling is suppressed.

That is, the present invention is characterized by the following configuration.
(1) An electric furnace for smelting reduction treatment of steelmaking slag having a furnace wall composed of an iron skin on the outside and a refractory brick wall on the inside, at least the furnace wall being in contact with the slag stored in the furnace It is provided on the outer periphery of the furnace wall at the site and is provided with a cooling means for cooling the iron skin, the refractory brick wall is arranged at the site in contact with the slag, and the graphite content is 30% by mass to 50% by mass. Electricity for smelting reduction treatment of steelmaking slag, including MgO-C brick of low thermal conductivity, which is disposed at a portion other than the portion in contact with slag and having a graphite content of 10% by mass to 25% by mass Furnace.
(2) The electric furnace for smelting reduction treatment of steelmaking slag according to (1), wherein an amorphous refractory having a carbon content of 5% by mass or less is filled between the iron shell and the refractory brick wall.

  In the above configuration, MgO—C brick with high thermal conductivity is used for work bricks in contact with the slag, giving priority to corrosion resistance against the steelmaking slag. The highly heat-conductive MgO-C brick has a graphite content of 30% by mass to 50% by mass in order to sufficiently reduce the temperature of the operating surface by cooling from the outside of the furnace wall and thereby improve the corrosion resistance. If the graphite content is less than 30% by mass, the temperature of the working surface is not sufficiently lowered, so that the corrosion resistance may be insufficient. On the other hand, if the graphite content exceeds 50% by mass, the operating surface temperature decreases beyond the level necessary to obtain corrosion resistance, resulting in an increase in heat loss.

  On the other hand, the work bricks other than the portion in contact with the slag, that is, the work bricks of the metal part and the free board part are low thermal conductive MgO-C bricks having a graphite content of 10% by mass to 25% by mass. As described above, since it is not necessary to cool the working surface of the furnace wall at this portion, it is not necessary to increase the thermal conductivity of the work brick. Rather, it is desirable that the thermal conductivity is low in order to reduce heat loss. However, if the graphite content is less than 10% by mass, the thermal expansion of the work bricks becomes remarkable due to the relatively high content of magnesia, and there is a possibility that damage due to peeling will increase due to insufficient spalling resistance. There is. Therefore, the MgO—C brick has a graphite content of 10% by mass or more even at a portion other than the portion in contact with the slag. Further, the spalling resistance is significantly improved by increasing the graphite content, and the graphite content is up to about 25% by mass. Even if the graphite content is further increased, the increase in heat loss is more remarkable. is there. Accordingly, the MgO—C brick has a graphite content of 25% by mass or less except for the portion in contact with the slag.

  In addition, the site | part which contacts slag as used in this specification means the part which may contact | connect slag during operation in the furnace wall of an electric furnace. During operation, the molten iron (metal) is stored in the lower layer in the electric furnace, and the slag is melted and reduced while the slag is stored in the upper layer. At this time, Fe generated by reducing FeO contained in the slag moves to the molten iron layer, whereby the interface between the slag and the metal rises. Moreover, if molten iron is discharged | emitted from a sprue opening, the interface of slag and a metal will fall. Therefore, the lower limit of the portion that may come into contact with the slag during operation is determined from the interface between the slag and metal in the average operation state, taking into account the height of the spout and the discharge conditions of the molten iron. It will be in a position that is lowered to the metal side by the height. For example, the lower limit position may be a position that is lowered about 100 mm toward the metal side from the average interface between the slag and the metal.

  On the other hand, the hot water surface of the slag stored in the electric furnace during operation also varies as the process proceeds. More specifically, when slag is newly charged from the charging furnace, the molten metal level of the slag rises. Moreover, if molten iron is discharged | emitted from the molten iron layer in the lower layer of slag via a tap, or if slag itself is discharged from a tap, the molten metal level of slag will fall. Therefore, the upper limit of the portion that may come into contact with the slag during operation is determined in consideration of the slag charging speed and the conditions for discharging molten iron and slag from the slag surface in the average operation state. The position is raised by the height of.

  In the following description, the portion of the furnace wall above the upper limit of the portion that may be in contact with the slag is also referred to as a free board portion. Similarly, in the following description, the portion of the furnace wall that is below the lower limit of the portion that may contact the slag and above the hearth surface, that is, the portion of the furnace wall that is exclusively in contact with the metal is referred to as the metal portion. Say.

  In addition, when a cooling means for cooling the iron skin of the furnace wall is provided in the electric furnace, in order to increase the adhesion between the iron skin and the work brick and ensure thermal conductivity, the gap between the iron skin and the work brick is secured. Filled with an irregular refractory such as stamp material. However, in order to prevent electric leakage from the graphite electrode to the iron skin, it is necessary to fill an amorphous refractory having a certain electric resistance. Basically, the discharge from the graphite electrode goes to the anode brick at the bottom of the furnace with higher conductivity through the molten metal, so it is not necessary to completely insulate, and a relatively high level of insulation is sufficient. It is. Therefore, it is possible to use a conventional refractory material such as a stamp material. However, when it is necessary to more reliably prevent leakage, the carbon content of the filled amorphous refractory may be 5% by mass or less in order to suppress conductivity. Alternatively, the filled refractory does not have to contain carbon. In order to maximize the thermal conductivity between the iron skin and the work brick, the lining thickness of the amorphous refractory is 100 mm or less, more preferably 70 mm or less. If higher thermal conductivity is required, a dense structure with high thermal conductivity is likely to be formed. Therefore, it is preferable to use an amorphous refractory as a stamp material.

  As described above, according to the present invention, in a DC electric furnace for steelmaking slag, it is possible to level the wear of the work bricks of each part constituting the refractory brick wall and improve the durability, and further It is possible to reduce the heat loss of cooling at a portion other than the portion in contact with.

It is a schematic longitudinal cross-sectional view of the DC electric furnace for the melting process of the steelmaking slag which concerns on one Example of this invention. It is a graph which shows the cost computed from the result of the operation using the electric furnace shown in FIG.

  Hereinafter, preferred embodiments and examples of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  As the MgO—C brick for the furnace wall used in the present invention, MgO—C brick generally used in converters, electric furnaces and the like can be used. However, as already explained, in the part in contact with the slag stored in the furnace, the highly heat-conductive MgO-C brick having a graphite content of 30% by mass to 50% by mass, except for the part in contact with the slag. A low thermal conductivity MgO-C brick having a graphite content of 10% by mass to 25% by mass is disposed.

Further, in the MgO-C brick used in the present invention, the remaining component other than graphite is magnesia (MgO), but in addition to graphite and magnesia, metals such as aluminum and silicon, metal carbides such as B ₄ C, and carbon black In addition, one or more of the organic binder and pitch may be contained at 7% by mass or less.

  Moreover, a stamp material, a press-fitting material, or mortar can be filled as an indeterminate refractory material disposed between the work brick and the iron shell on the furnace wall. A stamp material may be used when it is desired to increase the density and to increase the thermal conductivity. In the case where the insulation is increased as required, it is preferable that the carbon component such as graphite and silicon carbide in the amorphous refractory is 5 mass% or less or does not contain a carbon component. In addition, the amorphous refractory may be a magnesia type when it is necessary to suppress an excessive reaction with the work brick.

  The hearth brick of the hearth is arranged in the almost central part of the hearth, which is a portion located directly under the cathode electrode, and is a fired MgO-C brick impregnated with tar or pitch from the viewpoint of electrical conductivity and corrosion resistance. preferable. More specifically, as the MgO-C brick for the anode of the hearth, one containing about 10% to 30% by weight of scaly graphite and heat-treated at 800 ° C. or higher and impregnated with tar or pitch is used. be able to. The carbon-based stamp material between the anode MgO-C brick and the electrode uses a carbon-based stamp material in order to ensure conductivity. As this stamp material, a carbon-based stamp material used in an ordinary electric furnace or the like can be used. More specifically, a stamp material having a carbon content of 70 mass% to 99 mass% can be used.

  Since bricks other than the anode of the hearth do not contact the slag, the slag resistance is not required. Moreover, since graphite is easily dissolved in metal, it is preferable to arrange MgO bricks having excellent corrosion resistance against molten metal in portions other than the anode of the hearth. More specifically, what is generally used as a permanent brick such as a converter or an electric furnace can be used as the MgO brick for the hearth. That is, the MgO content is 90% by mass or more, does not contain graphite, and is fired at 1000 ° C. or more. In addition, when the wear of the hot metal contact portion of the hearth brick is large, the wear can be suppressed by using the MgO-C brick as the hot water contact portion. In this case, it is desirable to use those having a graphite content of 10% by mass to 25% by mass in consideration of wear resistance and thermal shock resistance.

  FIG. 1 is a schematic longitudinal sectional view of a DC electric furnace for melting treatment of steelmaking slag according to one embodiment of the present invention. Referring to FIG. 1, in the electric furnace 1, an amorphous refractory 13 is lined on the inner side of the iron skin 10, and a work brick on the furnace wall is further arranged on the inner side. For work bricks, low heat conductive bricks 3 (3 steps) placed on the free board from the top, high heat conductive bricks 4 (4 steps) placed on the slag, and low heat conduction placed on the metal part Includes 5 bricks (2 stages). Here, the low thermal conductive bricks 3 and 5 arranged in the free board part and the metal part are both MgO—C bricks containing 20% by mass of scaly graphite. Moreover, the highly heat conductive brick 4 arrange | positioned in the site | part which touches slag is a MgO-C brick containing 40 mass% of scaly graphite. It should be noted that the tap for discharging the slag and the tap for discharging the molten iron are not shown.

  In the electric furnace 1, a water cooling jacket 11 is installed on the outer periphery of the furnace wall except for a portion close to the furnace bottom. The amorphous refractory 13 filled between the work brick on the furnace wall and the water-cooled jacket 11 is a magnesia material stamp material of silica-based bond that does not contain carbon, and has a thickness of about 50 mm. Tar impregnated MgO-C brick is disposed as the anode brick 6 as the anode brick 6 and the fired MgO brick is disposed as the hearth brick 7 around the central portion of the hearth (just below the graphite electrode). The anode brick 6 was a tar-impregnated MgO-C brick having a graphite content of 23% by mass. A carbon-based stamp material 9 having a carbon content of 95% by mass is filled between the anode brick 6 and the lower electrode.

  As described above, when MgO-C brick is disposed in the hot water contact part of the hearth, in order to prevent electric leakage, an MgO brick or a stamp material is used between the MgO-C brick on the furnace wall. It is desirable to intervene.

  In the figure, line A indicates the position of the highest slag hot water surface assumed during operation. Line B shows the position of the interface between the lowest slag and molten iron expected during operation. Accordingly, the portion of the furnace wall that may come into contact with the slag during operation is in the range between line A and line B.

  In the electric furnace according to the embodiment of the present invention, the cooling means (water cooling jacket 11 in the case of the electric furnace 1) arranged at the outer periphery of the furnace wall covers at least the range between the line A and the line B. . As already described, at least in this range, it is necessary to increase the corrosion resistance by sufficiently lowering the temperature of the operating surface by cooling the furnace wall by the cooling means. The cooling means may not be arranged outside the above range. Even in that case, if the work bricks placed in areas other than the part in contact with the slag are made of MgO-C bricks with low thermal conductivity as described above, the atmosphere in the furnace or the heat of the metal will be prevented from being damaged by the iron skin. it can.

  Or when importance is attached to the stability of operation, you may arrange | position a cooling means besides the site | part which touches slag. As an example of this, in the electric furnace 1, the water cooling jacket 11 is arranged on the entire free board part and a part other than the part near the furnace bottom of the metal part. Also in this case, as described above, the effect of reducing the heat loss can be obtained by using the low-conductivity MgO-C brick as described above for the work bricks arranged other than the portion in contact with the slag. is there.

Next, the results of experiments on the relationship between the graphite content of the work bricks on the furnace wall and the durability in the operation using the electric furnace 1 as described above will be described. In the experiment conducted as an example and a comparative example, in the electric furnace 1 shown in FIG. 1, molten slag (CaO 45 mass%, SiO ₂ 15 mass%, FeO 15 mass% (including Fe), other The component was subjected to smelting reduction treatment at a temperature of 1650 ° C. for 40 hours, and then the average wear size (mm) of bricks at each part was measured. For the free board part, the part in contact with the slag (slag line), and the metal part, the graphite content of the work brick was changed, and the amount of brick wear, heat loss, and spall resistance at each part were measured. . The MgO—C brick contains 2% by mass of aluminum, 0.5% of boron carbide, and 2% by mass of amorphous carbon in addition to graphite, and the balance is magnesia. Table 1 shows the results of the experiment. In addition, the amount of wear of the brick is indicated by an index with the average wear size (mm) of each part in Example 1 as 100. The smaller the wear index, the smaller the wear. Similarly, the heat loss is also indicated by an index with Example 1 as 100. The smaller the heat loss index, the smaller the heat loss.

  Among the examples shown in Table 1, Examples 1 to 3 are examples in which the graphite content of the MgO-C brick in contact with the slag is different in the range of 30% by mass to 50% by mass. In any example, the amount of wear is small and good durability is obtained. On the other hand, Comparative Example 1 is an example in which the graphite content of the MgO-C brick at the portion in contact with the slag is 20% by mass. In Comparative Example 1, although the heat loss is smaller than that in Example 1, the amount of wear of the MgO-C brick is large because the cooling of the operating surface of the furnace wall is insufficient. Comparative Example 2 is an example in which the graphite content of the MgO-C brick at the portion in contact with the slag is 60%. In Comparative Example 2, the heat loss is increased although there is almost no difference in the amount of wear compared to, for example, Example 3 (the graphite content of the same part is 50% by mass).

  Examples 4 and 5 are examples in which the graphite content of the MgO-C brick in the free board part is different in the range of 10% by mass to 25% by mass. In any example, the amount of wear is small and good durability is obtained. In Example 4, the occurrence of a slight spall in the free board portion was observed, but since the wear is small compared to the maximum worn portion, it is considered that there is no problem. However, when importance is attached to the stability of the operation, a refractory lining using a wear brick having a higher graphite content and higher spall resistance is preferred. On the other hand, the comparative example 3 is an example which made the graphite content rate of the MgO-C brick of a free board part 5 mass%. In Comparative Example 3, the amount of wear was large because the peeling due to spalling became significant, and the durability was reduced. Comparative Example 4 is an example in which the graphite content of the MgO-C brick in the free board part is 40% by mass. In Comparative Example 4, the heat loss is increased although there is almost no difference in the amount of wear compared to, for example, Example 5 (the graphite content of the same part is 25% by mass).

  Example 6 and Example 7 are examples in which the graphite content of the MgO-C brick in the metal part is different in the range of 10% by mass to 25% by mass. In any example, the amount of wear is small and good durability is obtained. In Example 6, the occurrence of a slight spall in the metal part was recognized, but since the wear is small compared to the maximum worn part, it is considered that there is no problem. However, when importance is attached to the stability of the operation, a refractory lining using a wear brick having a higher graphite content and higher spall resistance is preferred. On the other hand, the comparative example 5 is an example which made the graphite content rate of the MgO-C brick of a metal part 5 mass%. In Comparative Example 5, since the peeling due to spalling became significant, the amount of wear was large and the durability was lowered. Comparative Example 6 is an example in which the graphite content of the MgO-C brick in the metal part is 40% by mass. In Comparative Example 6, for example, heat loss is increased although there is almost no difference in the amount of wear compared to Example 7 (the graphite content of the same part is 25% by mass). Moreover, in the electric furnace 1, the water cooling jacket 11 is not installed in the outer periphery of a furnace wall in the part near a furnace bottom among metal parts. Therefore, in Comparative Example 6, the temperature of the iron skin 10 on the back side of the work brick exceeded the allowable range in this portion, and damage to the iron skin 10 occurred.

  FIG. 2 is a diagram showing the operating costs calculated based on the amount of brick wear and heat loss in the examples of the present invention and the comparative examples shown in Table 1 as indices based on Example 1. Referring to FIG. 2, the costs in the examples are lower than those in the comparative examples, and it can be seen that the electric furnace according to the embodiment of the present invention can be operated at a lower cost than the conventional electric furnace.

  As mentioned above, although preferred embodiment and the Example of this invention were described in detail, referring an accompanying drawing, this invention is not limited to this example. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Electric furnace 3,5 Low heat conductive brick 4 High heat conductive brick 6 Anode brick 7 Hearth brick 9 Stamping material 10 Iron skin 11 Water-cooled jacket 13 Amorphous refractory

Claims (2)

An electric furnace for smelting reduction treatment of steelmaking slag having a furnace wall composed of an iron skin on the outside and a refractory brick wall on the inside,
A cooling means for cooling the iron skin disposed at an outer periphery of the furnace wall at a site where at least the furnace wall is in contact with the slag stored in the furnace;
The refractory brick wall is
A highly heat-conductive MgO-C brick that is disposed at a site in contact with the slag and has a graphite content of 30% by mass to 50% by mass,
An electric furnace for smelting reduction treatment of steelmaking slag, comprising a low thermal conductivity MgO-C brick, which is disposed in a region other than the portion in contact with the slag and has a graphite content of 10% by mass to 25% by mass. The electric furnace for smelting reduction treatment of steelmaking slag according to claim 1, wherein an amorphous refractory having a carbon content of 5% by mass or less is filled between the iron skin and the refractory brick wall.

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