JP2021134386A - Method for melting cold iron source with slag reduction - Google Patents

Abstract

To carry out a process without enlarging the scale of equipment and without reducing the volume in a furnace, when steel slag is reformed into a material usable for various applications, valuable elements such as Fe and P in the steelmaking slag are reduced and recovered into molten iron, and then molten iron from which Fe components are recovered is recycled into a steelmaking process.SOLUTION: Steel slag 24 in a molten state or solidified at a high temperature is charged onto the deposited part of a cold iron source 23 charged into an electric furnace 1. After the cold iron source 23 is partially melted by direct current or alternating current arc heating, a carbon material is charged into the melting pool as a reducing material, and a slag modifier containing SiO2 and Al2O3 as a component composition is charged to reduce the slag, the melted molten iron is carbonized, the molten iron is discharged, leaving the seed iron, from the tapping hole, and the reduced slag is discharged from the slag discharge port.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for melting a cold iron source with slag reduction.

Regarding the amount of steelmaking slag discharged, the amount of discharged slag is being reduced by improving the hot metal pretreatment. On the other hand, regarding the utilization of the discharged steelmaking slag, since the steelmaking slag has a high basicity, there are problems such as water immersion expansion and high pH water elution. Measures such as steam aging are taken against it.

On the other hand, technologies have been developed for reducing and reforming discharged slag to convert it into slag equivalent to blast furnace slag to expand its applications and at the same time recover valuable Fe and P contained in the slag. At that time, in order to minimize the required energy, it is effective to reduce the high-temperature steelmaking slag as it is without cooling and solidifying it, and various methods have been devised.

In Patent Document 1, hot steelmaking slag is flowed from a slag supply container (slag holding furnace) onto molten iron housed in an electric furnace, a reducing material is supplied to the molten slag layer, and the molten iron and the molten slag layer are formed. Disclosed is a steelmaking slag reduction treatment method in which the reduction treatment of hot steelmaking slag is continued in a non-oxidizing atmosphere while the molten slag of the molten slag layer or the molten iron is intermittently discharged by energizing and heating. There is. The steelmaking slag is reduced and the steelmaking slag is modified into materials that can be used for various purposes such as cement raw materials, earthwork materials, and ceramic products, and valuable elements such as Mn and P in the steelmaking slag are added to molten iron. After that, Fe and Mn are recycled to the steelmaking process, and P is recovered as an oxide by subjecting molten iron to an oxidation treatment, and is intended to be used as a phosphoric acid fertilizer or a phosphoric acid raw material. In the structure of Patent Document 1, instead of directly charging the molten slag into the electric furnace, the molten slag is temporarily held in a slag holding furnace arranged adjacent to the electric furnace, and the molten slag layer is used as a buffer zone on the molten iron layer in the electric furnace. After forming, the molten slag is gradually injected while adjusting the injection amount, so that there is a problem that the scale of the equipment becomes large.

The invention described in Patent Document 2 is characterized in that an electric furnace forming a molten iron layer and a molten slag layer has a shallow bottom portion at the bottom of the furnace, and the slag is charged from a transport container toward the shallow bottom portion. do. By continuously reducing, melting and reforming in the electric furnace, valuable resources (valuable elements such as Fe and P) in the molten slag are recovered in the molten iron layer which is the lower layer of the molten slag layer. The recovered high-phosphorus molten iron is subjected to a dephosphorization treatment to oxidize P in the molten iron and transfer it into the slag, whereby the high-phosphorus molten iron is separated into high-phosphate slag and molten iron. High phosphoric acid slag can be recycled as phosphoric acid fertilizer, phosphoric acid raw material, or the like. In addition, molten iron is recycled in the steelmaking process and put into a converter or the like. Since the molten slag is injected into the shallow bottom portion, it is possible to prevent the molten slag immediately after being injected and the molten iron layer in the electric furnace from being violently mixed, and it is possible to prevent the formation of forming. On the other hand, as a result of providing the shallow bottom portion, there is a problem that the internal volume of the furnace is reduced.

In an electric furnace, molten steel is formed by melting a cold iron source such as scrap. When attempting to perform secondary refining and continuous casting of molten steel melted in an electric furnace together with molten steel melted in a converter at a converter factory, the heat size of the electric furnace is smaller than that of a normal converter, and the converter factory Then, it is difficult to install it together with a converter because the capacity of the ladle does not match that of the existing secondary smelting and continuous casting machines and the time matching cannot be obtained well. In addition, electric furnace steel has a high [N] and trump element, and there are steel types that can only be achieved with converter steel.

Patent Document 3 includes an arc that includes a melting chamber and a shaft-type preheating chamber that is directly connected to the upper part of the melting chamber, and introduces exhaust gas generated in the melting chamber into the preheating chamber to preheat the cold iron source in the preheating chamber. A method of operating an arc furnace using a furnace is disclosed. The arc furnace is operated with the carbon concentration of the molten metal discharged from the arc furnace set to 1 mass% or more. By setting the carbon concentration of the molten metal to 1 mass% or more, the hot metal (molten metal) produced by using an arc furnace can be mixed with the hot metal of the blast furnace and incorporated into a part of the process flow by the blast furnace-converter method.

International release WO2014 / 003123 International release WO2018 / 110171 Japanese Unexamined Patent Publication No. 2010-265485

In the present invention, steelmaking slag is reduced in an electric furnace containing molten iron, and the steelmaking slag is modified into a material that can be used for various purposes such as cement raw materials, earthwork materials, and ceramic products, and in steelmaking slag. In the case of reducing and recovering valuable elements such as Mn and P in molten iron and then recycling the molten iron from which Fe and Mn are recovered into a steelmaking process, without using a large-scale facility as described in Patent Document 1. A method for melting a cold iron source accompanied by slag reduction, which does not require a shallow bottom portion as described in Patent Document 2 in the shape of the bottom of an electric furnace and can produce molten iron that can be easily recycled in the converter process. The purpose is to provide. Further, P produced by reducing steelmaking slag is also intended to be recovered as an oxide by subjecting molten iron to an oxidation treatment and used as a phosphoric acid fertilizer or a phosphoric acid raw material.

That is, the gist of the present invention is as follows.
[1] A cold iron source is charged into an electric furnace containing a seed bath, and a molten or high-temperature solidified steel slag is charged from above the deposited portion of the cold iron source and cooled by direct or AC arc heating. After the iron source is partially melted, a carbonaceous material is added to the molten pool as a reducing agent, and a slag modifier containing at least one _{of SiO 2} and Al ₂ O _{3 is added as a component composition to reduce the slag.} A method for melting a cold iron source with slag reduction, which comprises charcoalizing molten iron, discharging the molten iron from a hot water outlet leaving a seed bath, and then discharging reduced slag from a slag discharge port.
[2] The steelmaking slag is charged through an opening formed by moving the furnace lid of the electric furnace or opening the slag inlet of the furnace lid, and the slag pot containing the steelmaking slag. The steelmaking slag to be charged shall be charged directly from or through a trough, and the steelmaking slag to be charged shall be placed on the deposited portion of the cold iron source or on the solidified slag further deposited on the deposited portion of the cold iron source. The method for melting a cold iron source with slag reduction according to [1], which comprises charging in.
[3] The cold with slag reduction according to [1] or [2], wherein the reducing agent and the slag modifier are supplied through a raw material input pipe provided on the furnace lid while performing arc heating. Method of melting iron source.
[4] During the reduction of the slag, the lance is inserted into the slag layer, and the stirring gas is blown through the lance to stir the inside of the slag. The method for melting a cold iron source with slag reduction according to any one of [1] to [3].
[5] Any of [1] to [4], wherein one or both of the waste containing phosphoric acid and the high-phosphorus iron ore are charged through the raw material input pipe together with the reducing agent and the slag modifier. The method for melting a cold iron source with slag reduction according to one of the above.

In the present invention, steelmaking slag is reduced in an electric furnace containing molten iron, and the steelmaking slag is modified into a material that can be used for various purposes such as cement raw materials, earthwork materials, and ceramic products, and in steelmaking slag. When valuable elements such as Fe and P are reduced and recovered in molten iron, and then the molten iron from which Fe is recovered is recycled to the steelmaking process, a cold iron source is charged into the electric furnace containing the seed bath. By charging steelmaking slag in a molten state or solidified at high temperature from above the deposited part of the cold iron source, it is possible to perform processing without increasing the scale of the equipment and without reducing the internal volume of the furnace. It becomes.

It is a figure which shows the situation which the steelmaking slag is charged from the deposit part of the cold iron source in the melting method of a cold iron source of this invention. It is a figure which shows the addition state of a coal material and a slag modifier in the melting method of a cold iron source of this invention. It is a figure which shows the stirring state of the molten iron layer in the melting method of a cold iron source of this invention. It is a figure which shows the situation which the steelmaking slag is charged from the deposit part of the cold iron source in the melting method of a cold iron source of this invention. It is a figure which shows the addition state of a coal material and a slag modifier, and the agitation state of a slag layer in the method of melting a cold iron source of this invention.

Hereinafter, embodiments suitable for the present invention will be described in detail with reference to the drawings.
First, an outline of a method for melting a cold iron source accompanied by slag reduction, which is carried out using the electric furnace of the present invention, will be described.

In the ironmaking process, hot metal is produced using a blast furnace, and in the steelmaking process, pig iron is refined into steel using a converter or the like. This steelmaking process involves desulfurization, dephosphorization, and decarburization to remove sulfur, phosphorus, carbon, etc. in the hot metal, and component adjustment by removing gas such as hydrogen and sulfur remaining in the molten steel. It includes a next refining step and a casting step of casting molten steel with a continuous casting machine.

Of the steelmaking processes, dephosphorization and decarburization are mainly performed in a converter. In the converter, hot metal is refined using a flux containing calcium oxide as the main component. At this time, oxygen blown into the converter oxidizes C, Si, P, Mn, etc. in the hot metal, and the oxide is combined with calcium oxide to form slag. Further, in each step of desulfurization, dephosphorization, and decarburization, slag having different components (desulfurization slag, dephosphorization slag, decarburization slag) is generated. The slag remaining in the ladle after continuous casting is called ladle slag.

In the present invention, steelmaking slag is a general term for slag produced in the steelmaking process, and the steelmaking slag is a concept including desulfurization slag, derinsing slag, decarburization slag, and ladle slag. Further, steelmaking slag in a high-temperature molten state is referred to as molten slag, and similarly, desulfurized slag, decarburized slag, and derinsed slag in a molten state are referred to as molten desulfurized slag, molten derinsed slag, and molten decarburized slag, respectively.

In the slag processing process, the steelmaking slag produced in the above steelmaking process is transferred from the converter to the electric furnace in a molten state, and the steelmaking slag charged in the electric furnace is continuously reduced, melted and reformed. , Valuable resources (valuable elements such as Fe and P) in the molten slag are recovered in the molten iron layer which is the lower layer of the molten slag layer.

Conventionally, a molten iron bath is formed in advance in an electric furnace, molten steelmaking slag is added from above the molten iron bath, and a charcoal material is added as a reducing agent to the molten pool to perform reduction melting and reforming treatment of the slag. Was there. At this time, it is important to suppress slag forming at the time of slag injection. Therefore, as described above, in Patent Document 1, after forming the reduced molten slag layer on the molten iron layer in the electric furnace as a buffer band, the molten slag is gradually injected while adjusting the injection amount. The means are adopted. Further, Patent Document 2 is characterized in that a shallow bottom portion is provided at the bottom portion of the electric furnace, and the molten slag is charged from the transport container toward the shallow bottom portion.

By the way, in an electric furnace, a cold iron source such as iron scrap, pig iron, or reduced iron is charged into the electric furnace and melted by arc heating to form molten iron. In order to promote the dissolution of the cold iron source, a seed bath is formed in the electric furnace, and the dissolution of the cold iron source is promoted by increasing the carbon concentration in the seed bath and the molten iron in which the melting has progressed. In the initial stage of melting after the cold iron source is charged into the electric furnace, the seed water is stored at the bottom of the electric furnace, and the cold iron sources are piled up to form a sedimentary part.

In the present invention, when the cold iron source is charged into the electric furnace and the cold iron source deposit is formed, the molten steelmaking slag is poured from above the cold iron source deposit to melt the slag. The idea was to suppress the agitation of slag and molten iron, and as a result, to suppress the forming of slag.
Then, as shown in FIGS. 1 and 4, the cold iron source 23 is charged into the electric furnace 1 in which the seed bath 28 is housed, and the steelmaking slag is melted or solidified at a high temperature from above the deposited portion of the cold iron source 23. 24 is charged, and after the cold iron source 23 is partially melted by DC or AC arc heating, as shown in FIGS. 2 and 5, slag forming is performed by adding the carbonaceous material 26 as a reducing agent to the molten pool. It was found that the slag was suppressed and the reduction, melting and reforming of the slag proceeded well. At this time, in the electric furnace, the basicity of the slag is adjusted by adding the slag modifier 27, and the oxides such as Fe and P in the molten slag are reduced, and the slag is converted into granular iron (iron). Separation progresses. If the deposited thickness of the cold iron source 23 formed directly under the slag is not sufficient, the solidified slag 25 is charged, the solidified slag 25 is deposited on the cold iron source 23 deposited portion, and the steelmaking slag is formed. It may be charged on the solidified slag 25 and the undissolved cold iron source 23 in a piled state (see FIG. 4).

As the cold iron source to be charged into the electric furnace, iron scrap, pig iron, reduced iron and the like can be used. It is preferable to install a preheating furnace for preheating the cold iron source in the electric furnace, and to charge the cold iron source preheated in the preheating furnace into the electric furnace. As shown in FIG. 4, the preheating furnace includes a shaft-type preheating furnace 7 directly connected to the upper part of the electric furnace, and the exhaust gas generated in the electric furnace is introduced into the preheating furnace to introduce the cold iron in the preheating furnace 7. The source can be preheated.

As the steelmaking slag charged into the electric furnace, a steelmaking slag in a molten state or a steelmaking slag solidified at a high temperature can be used.

Coke, coal, or the like can be used as the charcoal material used as the reducing agent and the charcoal material. By adding the carbonaceous material, the reduction reaction of oxides such as Fe and P in the slag layer is promoted, and the molten iron layer is charcoalized to increase the carbon concentration of the molten iron. When the carbon concentration of the molten iron is 1% by mass or more, the molten iron can be used as it is, or after the molten iron is dephosphorized, it can be mixed with the blast furnace hot metal and used as the main raw material for the converter.

The steelmaking slag charged into the electric furnace is a _{high basicity slag having a high basicity (CaO / SiO 2} mass ratio), and is difficult to dissolve because it has a high melting point as it is. Further, in order to reduce the P component in the slag and transfer it into the molten iron layer, it is preferable that the basicity of the slag is low. Therefore, in the present invention, a slag modifier containing at least one _{of SiO 2} and Al ₂ O ₃ as a component composition is further charged into the electric furnace. By steelmaking slag and slag modifying agent are mixed, reduces the basicity of the slag, Al ₂ O ₃ concentration is increased, it is possible to lower the melting point of the slag after mixing as a result, the dissolution of the steel slag The slag reduction can proceed quickly. As the slag component after the addition of the slag modifier _{, it is preferable that the basicity is in the range of 0.8 to 1.3 and Al 2} O ₃ is in the range of 8 to 13% by mass.

The preferred ranges of the SiO ₂ concentration, Al ₂ O ₃ concentration, and the amount of the slag modifier added (ratio to the steelmaking slag to be charged) in the slag modifier vary depending on the components of the steelmaking slag to be charged. After the steelmaking slag and the slag modifier are mixed, the basicity of the slag may be 1.3 or less and the Al ₂ O ₃ concentration may be 8% by mass or more. For example, _{by appropriately blending silica sand having a SiO 2} concentration of 99% by _{mass, brick slag having an Al 2} O ₃ concentration of 83% by mass, and _{fly ash having a SiO 2} concentration of 59% by mass and an Al ₂ O ₃ concentration of 23% by mass. The slag composition can be adjusted to the optimum range, and slag dissolution can be suitably promoted. As the slag modifier, in addition to fly ash, silica sand, and brick scrap, sewage sludge ash, aluminum dross, and the like can be used.

As a result, high-phosphorus molten iron containing phosphorus and the like separated from molten slag is recovered, and molten slag, which is steelmaking slag, is reduced and reformed to recover high-quality reduced slag equivalent to blast furnace slag. .. This reduction slag, FeO compared with the previous reduction, due to the low content of such P ₂ O _5, it can be recycled to the cement material, ceramic products and the like. Further, if the components are adjusted so that the basicity of the molten slag is low, the expansion property becomes low, so that it can be used as a roadbed material, an aggregate, or a stone material.

Further, the recovered high-phosphorus molten iron is subjected to a dephosphorization treatment to oxidize P in the molten iron and transfer it into the slag, whereby the high-phosphorus molten iron becomes high-phosphate slag and molten iron (low-phosphorus hot metal). Is separated into. The high phosphoric acid slag can be commercialized as a phosphoric acid fertilizer, a phosphoric acid raw material, or the like. Further, molten iron (low phosphorus hot metal) is recycled in the steelmaking process, mixed with blast furnace hot metal, and then put into a converter or the like.

The outline of the slag processing process according to the present embodiment has been described above. Of the various steelmaking slags produced in the above steelmaking process, this process preferably targets melt-derinsed slag. Molten dephosphorized slag has a lower temperature than molten decarburized slag, but contains a large amount of granular iron and phosphoric acid, and is generally low in basicity. Therefore, by melt-modifying the melt-derinsed slag by a reduction treatment instead of an oxidation treatment, the recovery efficiency of valuable elements (Fe, P, etc.) by this process is increased, and the modification for lowering the basicity is performed. Since the amount of pawnbroker can be reduced, it also leads to the reduction of energy requirement. Therefore, in the following description, an example in which molten derinsed slag is mainly used as the molten slag to be treated will be described. However, the molten steelmaking slag of the present invention is not limited to the melt derinsing slag, and any steelmaking slag generated in the steelmaking process such as the melt desulfurization slag and the melt decarburized slag can be used.

By reducing in an electric furnace, the upper heat of the slag works advantageously, and by suspending the reducing agent in the slag, the CO reaction between the slag metals can be suppressed and the slag forming can be suppressed.

As the electric furnace used in the present invention, any of a stationary DC current furnace, a tilting DC current furnace, and an AC current furnace may be used. As shown in FIGS. 2 and 4, the electrode 3 is provided through the furnace lid 2 of the electric furnace 1, and the cold iron source and the steelmaking slag are heated by the heating by the electrode 3, and the molten iron layer 21 is placed in the electric furnace. The molten slag layer 22 is formed.

In the electric furnaces shown in FIGS. 1 to 3, the furnace lid is not provided with a slag inlet, and when the slag is charged into the electric furnace 1, the furnace lid 2 is moved laterally to form the slag. The steelmaking slag 24 is charged into the electric furnace 1 from the slag pan 4 via the opening (see FIG. 1).

In the electric furnace shown in FIGS. 4 and 5, a slag inlet 6 is installed in the furnace lid 2. Steelmaking slag is charged into the electric furnace via an opening formed by opening the slag inlet 6 of the furnace lid 2. In the example shown in FIG. 4, a gutter 5 is provided, the slag pot 4 is tilted to allow the steelmaking slag 24 to flow down to the gutter 5, and the steelmaking slag 24 enters the electric furnace 1 from the slag inlet 6 via the gutter 5. Is charged. Further, in the electric furnace shown in FIGS. 4 and 5, a preheating furnace 7 is arranged on the furnace lid 2. A cold iron source is supplied from the cold iron source hopper 8 into the preheating furnace 7, and the sensible heat of the electric furnace exhaust gas is used to raise the temperature of the cold iron source in the preheating furnace 7. Regarding the arrangement position of the slag inlet 6 and the preheating furnace 7 in the electric furnace 1, in the example shown in FIG. 4, the slag inlet 6 and the preheating furnace 7 are arranged at 180 ° to each other with respect to the central axis of the electric furnace 1. It is drawn as it is. Preferably, the slag inlet 6 and the preheating furnace 7 are arranged at positions of 90 to 120 ° with respect to the central axis of the electric furnace 1.

As shown in FIGS. 2 and 5, a raw material input pipe 9 is provided on the furnace lid 2. The carbonaceous material 26 and the slag modifier 27 can be charged into the electric furnace via the raw material input pipe 9. It is preferable that the charcoal material 26 and the slag modifier 27 are made into granules and supplied from the raw material input pipe 9 while being arc-heated. In order to prevent decarburization loss due to the intrusion of air into the electric furnace, it is preferable to maintain the closed state of the electric furnace as much as possible and perform reduction treatment and charcoalization in a non-oxidizing atmosphere. Regarding the addition of the charcoal material, the powdered charcoal material may be added by blowing it into the slag layer.

In the present invention, preferably, the slag layer 22 or the molten iron layer 21 can be agitated by inserting the lance 13 into the slag layer 22 or the molten iron layer 21 in the electric furnace 1 and blowing a stirring gas from the tip of the lance 13. .. The lance 13 can open the slug door 12 of the electric furnace 1 and insert it into the furnace through the open portion (see FIGS. 3 and 5).

In order to preferentially heat the slag by arc heating during the reduction of the slag and promote the agitation in the slag, it is preferable to insert a gas blowing lance into the slag layer to perform the gas agitation. In the example shown in FIG. 5, the tip of the lance 13 inserted via the slag door 12 is immersed in the slag layer 22, and the slag layer 22 is agitated by blowing an inert gas from the tip of the lance 13.

When the cold iron source is completely melted and the carbon concentration in the molten iron layer rises and the temperature rises, the energization is stopped. After the energization is completed, the tip of the lance 13 is immersed in the molten iron layer 21 to stir the gas. By doing so, the slag metal temperature can be made uniform. In the example shown in FIG. 3, the tip of the lance 13 inserted via the slag door 12 is immersed in the molten iron layer 21, and the inert gas is blown from the tip of the lance 13 to stir the molten iron layer 21 and the slag layer 22. Is going. The gas may be blown into the molten iron layer 21 by bottom blowing instead of the above lance immersion.

Along with the reducing agent and the slag modifier, one or both of the phosphoric acid-containing waste and the high-phosphorus iron ore can be charged through the raw material input pipe. As the waste containing phosphoric acid, a phosphoric acid source generated in sewage treatment or the like can also be recovered, and the silica source contained therein can be used as a slag modifier. In particular, sludge incinerator ash can be preferably used. As a result, the P concentration in the molten iron is increased, the molten iron is dephosphorized in the next step, the P ₂ O ₅ concentration in the derinsed slag is increased, and the value as a phosphate fertilizer raw material or other phosphorus product raw material is increased. Can be increased. Low boiling point harmful elements such as Cd, As, and Pb contained in sewage sludge are vaporized and removed by a high-temperature arc frame and do not remain in hot metal or high phosphate slag, so they can be safely recycled.
By increasing the amount of steelmaking slag charged, the P concentration in molten iron can also be increased.

In the dissolution process of Hiyatetsu source using an electric furnace, by applying the present invention, it is not necessary to introduce new flux during Hiyatetsu source dissolution, it is replaced with a high P ₂ O ₅ concentration steel slag can.

The iron source produced by the blast furnace method produces a large amount of _{CO 2 because it is produced by reducing iron ore with coke.} Therefore, as part of measures against global warming, it is required to reduce the ratio of the blast furnace method and increase the ratio of the electric furnace steel manufacturing method that melts iron scrap with electric energy. On the other hand, as described above, when the molten steel melted in the electric furnace is subjected to secondary refining and continuous casting together with the molten steel melted in the converter at the converter factory, the electric furnace heats up as compared with the normal converter. Due to its small size, the capacity of the pan does not match that of the existing secondary smelting and continuous casting machines at the converter factory, and time matching cannot be achieved well, so it is difficult to install it together with the converter. In addition, electric furnace steel has a high [N] and trump element, and there are steel types that can only be achieved with converter steel.

On the other hand, in the present invention, hot metal having a carbon concentration of 1% by mass or more is melted in an electric furnace. Even if the heat size of the electric furnace is smaller than the heat size of the converter, the heat size of the converter can be matched by mixing the hot metal produced in the electric furnace and the blast furnace hot metal. As a result, in a steelmaking factory having a converter, it becomes possible to produce hot metal in an electric furnace. Further, even if the cold iron source is melted in an electric furnace, the Trump element concentration and the molten steel nitrogen concentration can be reduced by diluting with hot metal in a blast furnace and blowing in a converter.

[Example 1]
As shown in FIGS. 1 and 2, the present invention was carried out using an electric furnace in which the furnace lid 2 of the electric furnace 1 is removed and an iron source is charged.

As the seed hot water 28, the furnace lid 2 of the electric furnace 1 (DC or AC electric furnace) containing about 40 tons of hot metal is slid open, and a cold iron source 60 tons preheated to 800 ° C. is opened in a charging bucket (not shown). It was charged in an electric furnace. Iron scrap and pig iron were used as cold iron sources. As shown in FIG. 1, in the electric furnace 1, a layer of the seed bath 28 is formed at the bottom, and the cold iron source 23 forms a deposit portion.

Melt decarburized slag or melt derinsed slag generated in a converter is used as the steelmaking slag 24, transported in a slag pot 4, and as shown in FIG. 1, the slag pot 4 is tilted to be piled up in the electric furnace 1. A 50 ton steelmaking slag 24 was charged from above the cold iron source 23 in a molten state. The charged steelmaking slag had a temperature of 1350 ° C., a component composition of CaO: 37.1%, SiO ₂ : 15.3%, and T.I. Fe: 21%, P ₂ O ₅ : 3.2%.

After the steelmaking slag was charged, the furnace lid 2 was closed, the electrode 3 was lowered, and the arc heat treatment was started at an output of 50 MW (see FIG. 2).
At the stage when the molten pool was formed, as shown in FIG. 2, coke powder was intermittently charged as a coal material 26 from above for a total of 7.5 tons via the raw material input pipe 9 provided in the furnace lid 2. The sealed state was maintained as much as possible to prevent decarburization loss due to air intrusion.
On the way, the furnace lid was opened and an additional 60 tons of cold iron source was charged.
Together with the addition of the charcoal material 26, 7.0 tons of silica sand and 4.0 tons of alumina-based brick scraps were added as the slag modifier 27. Overall average composition of the slag Aratameshitsuzai _{27, SiO} 2: 63 _wt%, Al ₂ O 3: was 30 wt%. In order to promote the reduction reaction in the slag and carburizing into the metal layer, the lance 13 was inserted into the furnace from the slag door 12, the lance was immersed in the slag layer, and ^{nitrogen gas was stirred at 60 Nm 3} / h (lance). See FIG. 5 for the arrangement of 13.

When the cold iron source is completely melted, the hot metal [C] is 2%, and the temperature exceeds 1500 ° C., the energization is stopped, and the tip of the lance 13 is immersed in the molten iron layer 21 as shown in FIG. 3, 60 Nm ³ /. The nitrogen gas of h was stirred to make the slag metal temperature uniform.

After the completion of the electric furnace refining, the electric furnace was tilted to discharge the hot metal constituting the molten iron layer 21 from the hot water outlet hole 11 into a ladle (not shown), leaving about 40 tons of seed hot water in the furnace. The electric furnace was tilted to the opposite side, the slag door 12 was opened to serve as a slag discharge port, and reduced slag was discharged from the slag port. The amount of hot metal discharged was 133 tons, and the amount of reduced slag was 46 tons. The metal components were C: 2.1%, P: 0.41%, and Si: 0.12%. The slag component is T.I. Fe: 1.0%, P ₂ O ₅ : 0.31%, CaO: 39.6%, SiO ₂ : 31.6%.

The hot metal contained in the ladle was dephosphorized with a dephosphorizing agent containing an oxidizing agent of oxygen and iron oxide and quicklime to obtain P: 0.11% in the hot metal. After the dephosphorization treatment, 137 tons of blast furnace hot metal was added to the hot metal to make 270 tons, which was charged into the converter. The slag obtained by the dephosphorization treatment was 6.1 tons, and the slag component was T.I. Fe: 12.5%, P ₂ O ₅ : 15.1%, and after cooling, it was crushed to use as a fertilizer raw material.

[Example 2]
As shown in FIGS. 4 and 5, the present invention was carried out using an electric furnace 1 in which a preheating furnace 7 is installed and a cold iron source is charged from the preheating furnace 7. Iron scrap was used as the cold iron source. The slag inlet 6 is arranged in the furnace lid 2 at a position 120 ° from the preheating furnace 7 with respect to the central axis of the electric furnace 1. Further, a gutter 5 for guiding the molten slag flowing out of the slag pan 4 to the slag inlet 6 is provided.

The cold iron source was charged into the preheating furnace 7 from the cold iron source hopper 8, the temperature of the cold iron source 23 was raised to about 800 ° C. in the preheating furnace 7, and then the cold iron source 23 was intermittently discharged into the electric furnace 1. .. Next, the lid of the slag inlet 6 was opened. Since the deposited thickness of the cold iron source 23 formed directly under the slag input port 6 was slightly thin, 20 tons of solidified steelmaking slag (solidified slag 25) was charged from the slag input port 6 to form the cold iron source 23 deposited portion. Solidified slag 25 was deposited on top. Next, from the slag pot 4, 30 tons of steelmaking slag 24 melted via the gutter 5 is injected into the furnace from the slag inlet 6, and is placed on the solidified slag 25 and the undissolved cold iron source 23 in a piled state directly below. The whole amount was charged. At that time, energization was stopped in order to suppress the reduction reaction of slag. The charged steelmaking slag had a temperature of 1350 ° C., a component composition of CaO: 37.1%, SiO ₂ : 15.3%, and T.I. Fe: 21%, P ₂ O ₅ : 3.2%.

After the slag charging was completed, the slag inlet 6 was closed, the electrode 3 was lowered, and the arc heat treatment was started with an output of 50 MW.
At the stage when the molten pool was formed, as shown in FIG. 5, coke powder was intermittently charged as a coal material 26 from above for a total of 7.5 tons via the raw material charging pipe 9 provided in the furnace lid 2. In order to prevent decarburization loss due to air intrusion, the sealed state was maintained as much as possible.
Together with the addition of the charcoal material 26, 7.0 tons of silica sand and 4.0 tons of alumina-based brick scraps were added as the slag modifier 27. Overall average composition of the slag Aratameshitsuzai _{27, SiO} 2: 63 _wt%, Al ₂ O 3: was 30 wt%. In order to promote the reduction reaction in the slag layer and carburizing into the molten iron layer, the lance 13 was inserted into the furnace from the slag door 12, and as shown in FIG. 5, 60 Nm ³ / h from the tip of the lance 13 into the slag layer 22. Nitrogen gas was blown in and stirred.

When the charged 120 tons of cold iron source was completely melted and the C: 2% of the molten iron layer 21 and the temperature exceeded 1500 ° C., the energization was stopped. The lance 13 was lowered to a position where the tip of the lance 13 was immersed in the molten iron layer 21 (see FIG. 3), ^{and nitrogen gas was blown in and stirred at 60 Nm 3} / h to make the slag metal temperature uniform.

After the completion of the electric furnace refining, the electric furnace was tilted to discharge the hot metal constituting the molten iron layer 21 from the hot water outlet hole 11 into a ladle (not shown), leaving about 40 tons of seed hot water in the furnace. The electric furnace was tilted to the opposite side, the slag door 12 was opened, and the reduced slag was discharged from the slag port. The amount of hot metal discharged was 133 tons, and the amount of reduced slag was 52 tons. The metal components were C: 2.1%, P: 0.41%, and Si: 0.12%. The slag component is T.I. Fe: 1.0%, P ₂ O ₅ : 0.31%, CaO: 39.6%, SiO ₂ : 31.6%.

The hot metal contained in the ladle was dephosphorized with a dephosphorizing agent containing an oxidizing agent of oxygen and iron oxide and quicklime to obtain P: 0.11% in the hot metal. After the dephosphorization treatment, 137 tons of blast furnace hot metal was added to the hot metal to make 270 tons, which was charged into the converter. The slag obtained by dephosphorization was 6.1 tons, and the slag component was T.I. Fe: 12.5%, P ₂ O ₅ : 15.1%, and after cooling, it was crushed to use as a fertilizer raw material.

1 Electric furnace 2 Furnace lid 3 Electrode 4 Slag pot 5 Slag 6 Slag inlet 7 Preheating furnace 8 Cold iron source hopper 9 Raw material inlet pipe 11 Hot water hole 12 Slug door 13 Lance 21 Molten iron layer 22 Slag layer 23 Cold iron source 24 Steelmaking slag 25 Solidified slag 26 Charcoal material 27 Slag modifier 28 Seed hot water

Claims (5)

A cold iron source is charged into the electric furnace containing the seed water, and a molten or high-temperature solidified steel slag is charged from above the accumulated portion of the cold iron source, and the cold iron source is heated by direct or AC arc heating. After partial dissolution, a carbonaceous material is added as a reducing agent to the molten pool, _{and a slag modifier containing at least one of SiO 2} and Al ₂ O ₃ is added as a component composition to reduce the slag and melt the molten iron. A method for melting a cold iron source with slag reduction, which comprises charcoalizing the hot metal, discharging the hot metal from the hot water hole leaving the seed water, and then discharging the reduced slag from the slag discharge port. The steelmaking slag is charged by moving the furnace lid of the electric furnace or via an opening formed by opening the slag inlet of the furnace lid, and directly from a slag pot containing the steelmaking slag or. It shall be charged through a trough, and at that time, the steelmaking slag to be charged shall be charged on the deposited portion of the cold iron source or on the solidified slag further deposited on the deposited portion of the cold iron source. The method for melting a cold iron source with slag reduction according to claim 1. The cold iron source with slag reduction according to claim 1 or 2, wherein the reducing agent and the slag modifier are supplied through a raw material input pipe provided on the furnace lid while performing arc heating. Dissolution method. During the reduction of the slag, the lance is inserted into the slag layer, and the stirring gas is blown through the lance to stir the inside of the slag. The method for melting a cold iron source with slag reduction according to any one of claims 1 to 3, which is characteristic. One of claims 1 to 4, wherein one or both of the waste containing phosphoric acid and the high-phosphorus iron ore are charged through the raw material input pipe together with the reducing agent and the slag modifier. The method for melting a cold iron source with slag reduction according to.

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