JP6221707B2 - Slag processing method and slag processing apparatus - Google Patents

Description

  The present invention relates to a slag treatment method and a slag treatment apparatus in which molten slag generated in a steelmaking process is temporarily held in a molten state in a slag holding furnace and then injected and reduced into an electric furnace.

  Slag (steel slag) produced by desulfurization, dephosphorization, or decarburization refining using a converter or the like in a steelmaking process contains a large amount of CaO. For this reason, since steelmaking slag has high expansibility and poor volume stability, conventionally, reuse to cement raw materials, aggregates, and the like has been limited. However, in recent years, there has been a demand for separation and recovery of valuable materials such as Fe and P from steelmaking slag, while reforming steelmaking slag to high-quality slag and reusing it, while the demand for resource recycling is increasing. Various slag treatment methods have been proposed so far.

  For example, in Patent Document 1, steel slag is added to the molten steel in the melting furnace, heat and reducing material are added to transform the steel slag, and Fe, Mn, and P in the slag are transferred to the molten metal. A slag treatment method is disclosed, which includes a first step of obtaining Mn and P, and second and third steps of oxidizing Mn and P in the molten metal and sequentially transferring them to a metamorphic slag and sequentially taking out high Mn slag and high P slag. Yes.

  In Patent Document 2, steel slag with an iron oxide content of more than 5 wt% is introduced into a steel bath with a carbon content of less than 1.5 wt%, and then the steel bath is carbonized by introducing carbon or a carbon carrier to contain the carbon. A method is disclosed in which a steel bath with a rate of greater than 2.0 wt% is obtained and thereafter the oxide in the steel slag is reduced. In this method, in order to suppress slag firing (slag forming) and eruption from the furnace (overflow) due to a violent reaction with the steel bath when slag is charged, the carbon content of the steel bath is reduced before slag is charged. The reaction rate at the time of slag injection is eased by setting, and the carbon content is then increased to reduce the slag.

  Non-Patent Document 1 discloses a result of a steel slag powder, a carbon material powder, and a slag modifier powder charged in an electric furnace and subjected to a slag reduction test. Furthermore, Patent Document 3 discloses a method of recovering valuable metals by reducing molten slag generated by non-ferrous refining with a carbonaceous reducing material in an open DC electric furnace, separating it into a metal layer and a slag layer. Has been.

  In addition, in Patent Document 4, in order to melt and reform steelmaking slag having low fluidity at low temperatures, the slag surface layer is added before and after the modifier is added or sprayed to the low fluidity steelmaking slag contained in the container. A method is disclosed in which after stirring mechanically, a mixed layer of slag and modifier is heated and melted using a heating burner, and the resulting molten slag is discharged from a container and solidified.

Japanese Patent Laid-Open No. 52-033897 Special table 2003-520899 gazette Australian Patent AU-B-20553 / 95 Specification JP 2005-146357 A

Scandinavian Journal of Metallurgy 2003; 32: p. 7-14

  However, in the slag treatment method described in Patent Document 1, since the reduction treatment is performed using a converter, the molten metal and slag are strongly stirred. For this reason, if the carbon concentration of the molten metal is high when the slag is charged, the reaction is promoted by the slag coming into contact with the molten metal and forming occurs. In order to avoid this, it is necessary to repeat the batch process in order to increase the carbon concentration of the molten metal by introducing carbon in order to promote the reduction reaction after the slag is introduced into the molten metal having a low carbon concentration. That is, in order to obtain a slag having a required component composition, it is necessary to repeatedly perform a plurality of batch processes (multiple slag reduction processes and Mn and P oxidation and removal processes), so that work efficiency and productivity are improved. descend.

  Similarly, in the slag reduction method described in Patent Document 2, since the reduction treatment is performed using a converter, in order to reduce or increase the carbon concentration in the molten iron and perform the slag reduction treatment, decarburization heating and heating are performed. The batch process of charcoal reduction is repeated, and the work efficiency and productivity are reduced.

  On the other hand, in the reduction test described in Non-Patent Document 1, a solidified cold steelmaking slag pulverized product is treated, and in the method described in Patent Document 3, the solidified cold slag is treated. In this case, in order to perform the reduction treatment of slag, it is necessary to heat and melt the cold slag, and the energy intensity increases accordingly.

  As described above, the conventional methods (Patent Documents 1 and 2) in which hot steelmaking slag is recycled by batch processing have a problem that work efficiency and productivity of slag processing are low. On the other hand, in the conventional methods (Non-patent Document 1 and Patent Document 3) in which cold steelmaking slag is heated and melted for recycling, there is a problem that the energy intensity required for the slag treatment increases.

  Therefore, the inventors of the present application can treat the molten steelmaking slag (hereinafter referred to as molten slag) generated in the steelmaking process in the molten state without solidifying in order to reduce the energy intensity. In order to improve the working efficiency and productivity, the inventors have intensively studied a method that can continuously perform the reduction treatment of the molten slag.

  If molten slag is put in a molten state on molten iron in an electric furnace, the energy intensity can be suppressed as compared with the case where cold slag is heated and melted. However, when molten slag is put on the molten iron in the electric furnace, the slag suddenly reacts with the molten iron to cause bumping (slag forming), and when this becomes severe, the slag overflows from the electric furnace (overflow) May occur. Therefore, it is necessary to take measures to suppress such slag forming and prevent overflow.

  In a reduction furnace (converter, etc.), the reduction reaction is promoted by the reaction between slag and molten iron, and C in the molten iron reduces FeO in the slag. Need to be repeated, resulting in lower work efficiency. In contrast, it was found that the reduction reaction in the electric furnace is dominated by the reaction between iron (FeO) and carbon (C) in the slag rather than between the slag and molten iron. Therefore, when an electric furnace is used, even if the C concentration in the molten iron is as low as about 1.5% by mass, it is possible to perform slag reduction treatment without carburizing, and work efficiency can be improved. It turns out that it can improve. Therefore, using an electric furnace instead of a reducing furnace can be one of the measures for suppressing slag forming when molten slag is charged.

  However, the C concentration in the molten iron in the electric furnace may be high. Therefore, even in such a case, the inventors of the present application can suppress slag forming and the like at the time of slag injection, and appropriately perform molten slag with high work efficiency without performing decarburization / carburization processing. We studied earnestly about the method of reduction treatment and repeated experiments.

  As a result, (a) the high-temperature molten slag having fluidity is not directly charged into the electric furnace, but once held in the slag holding furnace disposed adjacent to the electric furnace, the overflow does not occur. The molten slag is gradually injected into the electric furnace from the slag holding furnace while adjusting the injection amount, and (b) a molten slag layer (preferably an inert reduced slag layer on the molten iron layer in the electric furnace) ) As a buffer zone and injecting molten slag into the molten slag layer from a slag holding furnace proved to be preferable from the viewpoint of suppressing slag forming during slag charging and avoiding overflow did.

  In this way, by using the slag holding furnace and injecting the molten slag into the molten slag layer in the electric furnace while adjusting the injection amount of the molten slag, it is possible to suppress the occurrence of rapid slag forming during the slag injection and to decarburize. -It is possible to continuously perform slag reduction treatment in an electric furnace without carburizing.

  However, it is not always easy to stably adjust the injection amount of the molten slag using the slag holding furnace. For example, if the molten slag charged into the slag holding furnace already contains solidified slag, these slags are irregularly mixed with the molten slag and injected from the slag holding furnace into the electric furnace. There is a possibility that the amount of molten slag injected will vary with respect to the planned amount. In addition, when a spout is formed on one side of the slag holding furnace and the molten slag is caused to flow down from the spout by pouring the slag holding furnace and injected into the electric furnace, a part of the molten slag is in the slag holding furnace. It cools and solidifies and gradually adheres to the inner surface of the slag holding furnace including the spout. Therefore, when the slag holding furnace is used for a long time, the injection path of the molten slag becomes narrow due to the slag adhering to the inner surface of the spout part, and even if the slag holding furnace is tilted by a predetermined angle, A planned amount of molten slag may not be injected.

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to melt the molten slag when it is injected from the slag holding furnace into the electric furnace that performs the reduction treatment of the molten slag. It is an object of the present invention to provide a new and improved slag treatment method and slag treatment device that make it possible to stably control the injection amount of slag.

In order to solve the above problems, according to an aspect of the present invention, the molten slag produced in the steel making process was put into the slag holding furnace a molten state, the molten slag formed in the dissolved iron layer and the molten iron layer The molten slag is injected from the slag holding furnace onto the molten slag layer in the electric furnace containing the layer, and the molten slag is continuously reduced in the electric furnace, and the valuable material in the molten slag is contained in the molten iron layer. The slag treatment method is to collect the molten slag by adjusting the injection speed of the molten slag and the electric power supplied to the electric furnace, and measuring the actual cumulative injection amount by the injection of the molten slag, and the molten slag is reduced by the electric furnace. When the planned cumulative injection amount is calculated when injected at a target injection speed according to the capacity, and the difference exceeds the first threshold based on the difference between the actual cumulative injection amount and the planned cumulative injection amount , the electric furnace For injecting molten slag into The slag holding furnace by controlling the tilting angle of the slag holding furnace by tilting means for tilting and adjusting the injection rate of the molten slag, when the difference exceeds a second threshold value larger than the first threshold, Furthermore, the reduction power of the electric furnace is calculated based on the effective electric power obtained by subtracting the electric power corresponding to the circuit loss and heat loss in the electric furnace from the electric power supplied to the electric furnace, and the slag is adjusted to adjust the electric power supplied to the electric furnace. A processing method is provided.
The electric furnace has a tap outlet and a tap outlet, and when the thickness of the molten slag layer reaches a predetermined layer thickness, the reduced slag of the molten slag layer is discharged from the tap outlet, When the interface of the molten iron layer approaches the tap outlet, the molten iron in the molten iron layer is discharged from the tap port, so that the reduction treatment of the molten slag may be continued without interruption.

In order to solve the above problems, according to another aspect of the present invention, the molten slag produced in the steel making process was put into the slag holding furnace a molten state, is formed on the dissolved iron layer and the molten iron layer The molten slag is poured from the slag holding furnace onto the molten slag layer in the electric furnace containing the molten slag layer, and the molten slag is continuously reduced in the electric furnace, thereby converting the valuable material in the molten slag into molten iron. A slag treatment device that is recovered in a layer, and when adjusting the injection rate of molten slag and the power supplied to the electric furnace, measuring means for measuring the actual cumulative injection amount by injection of molten slag, When the planned cumulative injection amount is calculated when injected at a target injection rate according to the reduction processing capacity of the furnace, and the difference exceeds the first threshold based on the difference between the actual cumulative injection amount and the planned cumulative injection amount In addition, the molten slag in the electric furnace By controlling the tilt angle of the slag holding furnace by tilting means for tilting the slag holding furnace to enter, injection rate control means and the second difference is greater than the first threshold value to adjust the injection rate of the molten slag When the threshold value of the electric furnace is exceeded, the reduction processing capacity of the electric furnace is calculated based on the effective power obtained by subtracting the electric power corresponding to the circuit loss and heat loss in the electric furnace from the electric power supplied to the electric furnace. and power supply means for adjusting the power supplied, Ru includes a slag processing device is provided.
The electric furnace has a tapping outlet and a tapping outlet. When the thickness of the molten slag layer reaches a predetermined layer thickness, the reducing slag of the molten slag layer is discharged from the tapping outlet. Slag discharging means,
In the case where the interface of the molten iron layer approaches the outlet, the molten iron discharging means for discharging the molten iron in the molten iron layer from the outlet may be provided, and the reduction treatment of the molten slag may be continued without interruption.

  By setting the target injection speed of molten slag according to the reduction capacity of the electric furnace, it is expected that the molten slag is injected from the slag holding furnace to the electric furnace at an appropriate injection speed. Even if the molten slag injection rate deviates from the target injection rate for some reason, the molten slag injection rate can be adjusted based on the difference between the actual and planned cumulative slag injection rate. Can be stably controlled.

  As described above, according to the present invention, when the molten slag is injected from the slag holding furnace into the electric furnace that executes the reduction treatment of the molten slag, the injection amount of the molten slag can be stably controlled.

It is process drawing which shows the slag processing process which concerns on one Embodiment of this invention. It is a mimetic diagram showing the whole slag processing equipment composition concerning the embodiment. It is a longitudinal cross-sectional view which shows the slag holding furnace (holding attitude | position) which concerns on the same embodiment. It is a longitudinal cross-sectional view which shows the slag holding furnace (injection attitude | position) which concerns on the same embodiment. It is a figure for demonstrating calculation of the target injection | pouring speed | rate of molten slag in the embodiment. It is a graph which shows the relationship between the supply electric power and the target injection | pouring speed | rate of molten slag in the same embodiment, and the relationship between the amount of cumulative supply electric power and the scheduled accumulation injection | pouring amount of molten slag. It is a flowchart which shows the example of the adjustment process of the injection | pouring speed | rate of molten slag in the embodiment. It is a flowchart which shows the example of the control for increasing the injection | pouring speed | rate of molten slag in the same embodiment. It is a flowchart which shows the example of the control for reducing the injection | pouring speed | rate of molten slag in the same embodiment. It is a graph which shows the relationship between the electric power supplied to the electric furnace in Example 1 of this invention, the injection | pouring speed | rate of molten slag, and the accumulation injection | pouring amount of molten slag. It is a graph which shows the relationship between the electric power supplied to the electric furnace in Example 2 of this invention, the injection | pouring speed | rate of molten slag, and the accumulation injection | pouring amount of molten slag. It is a graph which shows the relationship between the electric power supplied to the electric furnace in Example 3 of this invention, the injection | pouring speed | rate of molten slag, and the accumulation injection | pouring amount of molten slag.

  Exemplary embodiments of the present invention will be described below 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.

[1. Overview of slag treatment process]
First, an outline of a slag processing process according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a process diagram showing a slag treatment process according to this embodiment.

  As shown in FIG. 1, hot metal is produced using a blast furnace in the iron making process (S1), and pig iron is refined into steel using a converter or the like in the steel making process (S2). This steel making process (S2) is a desulfurization, dephosphorization, and decarburization process that removes sulfur, phosphorus, carbon, etc. in the hot metal, and gas, sulfur, etc., remaining in the molten steel, and component adjustment. The secondary refining process (S6) which performs, and the casting process (S7) which casts molten steel with a continuous casting machine.

  In the steelmaking step (S2), the hot metal is refined in the converter using a flux mainly composed of calcium oxide. At this time, oxygen, blown into the converter, oxidizes C, Si, P, Mn and the like in the hot metal, and the oxide is combined with calcium oxide and generated as slag. Moreover, in each process (S3, S4, S5) of desulfurization, dephosphorization, and decarburization, slag (desulfurization slag, dephosphorization slag, decarburization slag) having different components is generated.

  In this specification, the slag produced | generated at the said steelmaking process is named generically as steelmaking slag, and the said steelmaking slag is the concept containing desulfurization slag, dephosphorization slag, and decarburization slag. Steelmaking slag in a molten state at high temperature is referred to as molten slag, and similarly, desulfurized slag, decarburized slag, and dephosphorized slag in molten state are respectively melted desulfurized slag, molten dephosphorized slag, and molten decarburized slag. Called.

  In the slag treatment step (S10), the molten slag generated in the steel making step (S2) is transported from the converter to the electric furnace in a molten state, and continuously reduced and melt-modified in the electric furnace. Then, valuable materials (feature 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. At this time, in the electric furnace, a reduction process of oxides such as Fe and P in the molten slag, a process of separating granular iron (iron) from the slag, a process of adjusting the basicity of the slag, and the like are performed.

  As a result, high-phosphorus molten iron containing phosphorus and the like separated from the molten slag is recovered, and molten slag, which is steelmaking slag, is reduced and reformed, and high-quality reduced slag equivalent to blast furnace slag is recovered. . Since this reduced slag is less expansible than steelmaking slag, it can be effectively recycled into cement raw materials, fine aggregates, ceramic products and the like.

  Further, the recovered high-phosphorus molten iron is subjected to dephosphorization treatment (S11) to oxidize P in the molten iron and transfer it to the slag, so that the high-phosphorus molten iron is separated into high phosphate slag and molten iron. Is done. High phosphoric acid slag can be recycled as phosphoric acid fertilizer or phosphoric acid raw material. Further, the molten iron is recycled to the steel making process (S2) and is put into a converter or the like.

  In addition, when the molten iron discharged from the blast furnace is used as the molten iron accommodated in the electric furnace, a low silicon hot metal is obtained by performing a dephosphorizing process (S11) on the high phosphorus molten iron. Therefore, it can be recycled to the converter as it is.

  The outline of the slag processing process according to the present embodiment has been described above. In the present process, it is preferable to treat the molten dephosphorization slag among the various molten slags generated in the steel making step (S2). The molten dephosphorized slag is at a lower temperature than the molten decarburized slag, but contains a large amount of granular iron and phosphoric acid. For this reason, recovery efficiency of valuable elements (Fe, P, etc.) by this process becomes high by melt-modifying molten dephosphorization slag not by oxidation treatment but by reduction treatment. Therefore, in the following description, an example in which molten dephosphorization slag is mainly used as the molten slag to be processed will be described. However, the molten slag of the present invention is not limited to molten dephosphorization slag, and any steelmaking slag generated in the steelmaking process such as molten desulfurization slag and molten decarburization slag can be used.

[2. Slag treatment equipment configuration]
Next, slag processing equipment for realizing the slag processing process will be described with reference to FIG. FIG. 2 is a schematic diagram illustrating the overall configuration of the slag treatment facility according to the present embodiment.

  As shown in FIG. 2, the slag treatment facility includes an electric furnace 1 and a slag holding furnace 2 disposed obliquely above the electric furnace 1. In addition, a slag pan 3 is used to introduce the molten slag 4 into the slag holding furnace 2, and this slag pan 3 is a converter (not shown) used in the steel making process and the slag holding furnace 2. Reciprocate between them. The molten slag 4 discharged from the converter is put into the slag pan 3. The slag pan 3 is charged into the slag holding furnace 2 after conveying the molten slag 4 from the converter to the slag holding furnace 2. The slag holding furnace 2 can also store and hold the molten slag 4 and injects the held molten slag 4 into the electric furnace 1 continuously or intermittently.

  Note that the molten slag 4 held in the slag holding furnace 2 does not need to be completely melted, and may have fluidity that can be injected from the slag holding furnace 2 into the electric furnace 1. That is, even if a part of the molten slag 4 is melted and the remaining part is solidified, it is only necessary to have fluidity as a whole.

  The electric furnace 1 reduces and reforms the molten slag 4 using a reducing material such as a carbonaceous material and a secondary material such as a modifying material. The electric furnace 1 is a reduction-type electric furnace for melting and reducing the molten slag 4 as described above, and is composed of, for example, a fixed DC electric furnace. The outer shell of the electric furnace 1 includes a furnace bottom 11, a furnace wall 12, and a furnace lid 13, and a slag inlet 14 is formed on one side of the furnace lid 13. Thus, the electric furnace 1 has a sealed structure except for the slag inlet 14 so that the furnace space can be kept warm.

  In the center of the electric furnace 1, an upper electrode 15 and a furnace bottom electrode 16 are disposed so as to face each other in the vertical direction. A DC power source is applied to the upper electrode 15 and the furnace bottom electrode 16 to generate an arc discharge between both the electrodes 15 and 16, thereby reducing the molten slag 4. If the upper electrode 15 is a hollow electrode as shown in the figure, the auxiliary material can be charged into the arc spot through the hollow electrode without installing a separate material charging device.

  A furnace wall 12 of the electric furnace 1 is provided with a tap outlet 17 for discharging reduced slag and a tap outlet 18 for discharging molten iron. The pouring gate 17 is arranged at a height position corresponding to the molten slag layer 5 on the molten iron layer 6, and the pouring gate 18 is arranged at a height position corresponding to the molten iron layer 6 on the furnace bottom side.

FIG. 2 illustrates a case where the raw material supply devices 31, 32 and 33 are all provided in the electric furnace 1. The raw material supply device 31 is provided when iron-containing materials such as iron scrap and direct reduced iron (DRI) are supplied into the electric furnace 1. Moreover, the raw material supply apparatus 33 is provided when supplying fine powdery iron-containing material (for example, FeO powder), such as dust powder containing iron, into the electric furnace 1 through the hollow electrode (upper electrode 15). Thereby, these iron-containing materials can be melted and recycled in the electric furnace 1. Further, the raw material supply device 32 is necessary for supplying auxiliary raw materials such as a reducing material and a reforming material necessary for the reduction treatment of the molten slag 4, and here, in the electric furnace 1 through the hollow electrode (upper electrode 15). The case where it supplies to is illustrated. As the reducing material, for example, fine powdery carbon materials such as coke powder, smokeless coal powder, and graphite powder are used. Further, the modifier is mainly for adjusting the concentration of SiO ₂ , Al ₂ O ₃ or MgO in the slag, and for example, silica sand, fly ash, MgO powder, waste refractory powder and the like can be used.

  With reference to FIG. 2, the reduction process of the molten slag 4 using the electric furnace 1 having the above configuration will be described.

  First, a considerable amount of molten iron (for example, molten iron transported from a blast furnace) is stored in advance in the electric furnace 1 as a molten iron layer 6 as seed hot water. The C concentration of molten iron is usually 1.5% by mass to 4.5% by mass. In the electric furnace 1, the present inventors correlate the C concentration (mass%) of the molten iron with the total Fe concentration (T.Fe) (mass%) of the molten slag 4 (reduced slag) after the reduction treatment. It has been confirmed by experiments. For example, when the C concentration of the molten iron exceeds 3% by mass, the reduction of the oxide in the molten slag 4 is promoted, and (T.Fe) of the reduced slag can be reduced to 1% by mass or less. Therefore, it is preferable to adjust the C concentration of the molten iron in the molten iron layer 6 in accordance with the desired (T.Fe) of the reduced slag.

  Next, after supplying electric power to the electric furnace 1 and operating it continuously, an amount of molten slag 4 corresponding to the reduction processing capacity of the electric furnace 1 (for example, the amount of electric power supplied to the electric furnace 1 per unit time) Injection into the electric furnace 1 from the holding furnace 2. The molten slag 4 injected into the electric furnace 1 forms a molten slag layer 5 on the molten iron layer 6. Further, the auxiliary materials such as the reducing material (carbon material) and the reforming material are continuously fed into the molten slag layer 5 in the electric furnace 1 through the upper electrode 15, for example. In the electric furnace 1, the temperature of the molten iron layer 6 is controlled to be, for example, 1400 ° C. to 1550 ° C., and the temperature of the molten slag layer 5 is, for example, 1500 ° C. to 1650 ° C. This temperature control can be performed by adjusting the supply amount of the molten slag 4 or adjusting the power supply amount within a range where the power supply amount per unit time is constant.

As a result, the reduction reaction of the molten slag 4 in the molten slag layer 5 proceeds in the electric furnace 1 by the arc heat between the upper electrode 15 and the furnace bottom electrode 16. In this reduction treatment, oxides (FeO, P ₂ O _{5 and the} like) contained in the molten slag 4 are reduced by carbon of the carbonaceous material in the molten slag layer 5 to produce Fe and P, and the Fe, P Moves from the molten slag layer 5 to the molten iron layer 6 (molten iron) on the furnace bottom side. On the other hand, the surplus carbon material C does not move to the molten iron layer 6 but is suspended in the molten slag layer 5. In the reduction treatment, the slag component in the molten slag 4 is reformed by the modifying material.

  In the above reduction treatment, FeO contained in the injected molten slag 4 preferentially reacts with C of the carbonaceous material in the molten slag layer 5 rather than C contained in the molten iron in the molten iron layer 6 (FeO + C → Fe + CO ↑). That is, since carbon C of the input carbon material does not move to the molten iron layer 6 but is suspended in the molten slag layer 5, a reduction reaction of FeO + C → Fe + CO ↑ hardly occurs at the interface between the molten iron layer 6 and the molten slag layer 5. . For this reason, the reduction reaction proceeds preferentially in the molten slag layer 5, and the generated reduced iron (Fe) moves to the molten iron layer 6.

  Thus, in the reduction treatment by the electric furnace 1, the reaction between FeO and C in the molten slag layer 5 is more dominant than the reaction between FeO in the molten slag layer 5 and C in the molten iron layer 6. is there. Therefore, when the molten slag 4 is injected into the electric furnace 1, the molten slag layer 5 on the molten iron layer 6 becomes a buffer zone for the reaction between the injected molten slag 4 and the molten iron in the molten iron layer 6. Rapid reaction between the slag 4 and molten iron can be suppressed.

  That is, by injecting the molten slag 4 into the molten slag layer 5 having a low FeO concentration, the FeO concentration of the injected molten slag 4 can be reduced, and the injected molten slag 4 and the molten iron of the molten iron layer 6 can be reduced. Direct contact can be suppressed. Therefore, when the molten slag 4 is injected from the slag holding furnace 2 to the electric furnace 1, a sudden boiling phenomenon (slag forming) due to a rapid reaction between the molten slag 4 and the molten iron can be suppressed, and the molten slag 4 is outside the electric furnace 1. The phenomenon of overflowing (overflow) can be avoided.

  As described above, the oxide contained in the molten slag 4 injected into the molten slag layer 5 in the electric furnace 1 is reduced, and Fe and P are recovered from the molten slag 4 to the molten iron layer 6. The slag component of the molten slag 4 is modified. Therefore, if the reduction process proceeds after the injection of the molten slag 4, the components of the molten slag layer 5 are gradually reformed from the molten slag 4 (steel slag) to reduced slag (high quality slag equivalent to blast furnace slag). Go. The molten slag layer 5 modified to reduced slag becomes a buffer zone having a lower FeO concentration. Therefore, when newly injecting the molten slag 4 from the slag holding furnace 2 into the molten slag layer 5, more slag forming is performed. It becomes possible to suppress it reliably.

Further, as the reduction treatment proceeds, Fe moves into the molten iron, and the layer thickness of the molten iron layer 6 gradually increases.
In addition, the layer thickness of the molten slag layer 5 is preferably 100 mm to 600 mm, more preferably 100 mm to 800 mm, from the viewpoint of expressing a function as a buffer zone. For this reason, when the molten slag 4 is injected and the thickness of the molten slag layer 5 reaches a predetermined layer thickness, the spout 17 is opened and the reduced slag of the molten slag layer 5 is discharged. Moreover, when the interface of the molten iron layer 6 approaches the hot metal outlet 17, the hot water outlet 18 is opened, and the molten iron (for example, high P hot metal) of the molten iron layer 6 is discharged. In this manner, reducing slag is intermittently discharged and recovered from the hot water outlet 18 and the molten iron is intermittently discharged and recovered. Thereby, in the electric furnace 1, the reduction process of the molten slag 4 can be continued without interruption.

Further, during operation of the electric furnace 1 (that is, during the reduction process), high temperature exhaust gas containing CO, H _2, etc. is generated by reducing the oxide of the molten slag 4 using carbon of carbonaceous material. To do. For example, when reducing iron oxide, CO gas is generated by the reaction of FeO + C → Fe + CO ↑. The exhaust gas flows into the slag holding furnace 2 through the slag inlet 14 of the electric furnace 1 and is discharged outside through the slag holding furnace 2 as an exhaust path. Thus, by making the electric furnace 1 into a closed type and using the slag holding furnace 2 as an exhaust path, the atmosphere in the electric furnace 1 includes CO gas generated by a reduction reaction and H ₂ generated from a carbonaceous material (reducing material). Maintained in a reducing atmosphere with the main component. Therefore, the oxidation reaction on the surface of the molten slag layer 5 can be prevented.

[3. Slag holding furnace configuration]
Next, with reference to FIG. 3 and FIG. 4, the structure of the slag holding furnace which concerns on this embodiment is explained in full detail. FIG. 3 is a longitudinal sectional view showing the slag holding furnace 2 (holding posture) according to the present embodiment, and FIG. 4 is a longitudinal sectional view showing the slag holding furnace 2 (injecting posture) according to the present embodiment.

  As shown in FIG. 3, the slag holding furnace 2 is a heat-resistant container and has a function of holding a high-temperature molten slag 4 and injecting it into the electric furnace 1. The slag holding furnace 2 has a structure capable of holding the molten slag 4 and adjusting the injection amount of the molten slag 4 into the electric furnace 1, and also functions as an exhaust path for the exhaust gas generated in the electric furnace 1. To do. The slag holding furnace 2 injects the slag holding furnace body 20 (hereinafter referred to as “furnace body 20”) for storing and holding the molten slag 4 and the molten slag 4 in the furnace body 20 into the electric furnace 1. And a spout portion 21 for the purpose.

  The furnace body 20 is a sealed container including a lower wall 22, a side wall 23, and an upper wall 24, and has an internal space for storing the molten slag 4. The lower wall 22 is composed of an iron skin 22a and a heat insulating material 22b outside the iron skin 22a, and an inner refractory 22c inside the iron skin 22a, and is excellent in strength and heat resistance. A lining refractory is also applied to the inner surfaces of the side wall 23 and the upper wall 24.

  A gas discharge port 25 and a slag input port 26 are provided on the upper portion of the furnace body 20 on the furnace lid 27 side. The gas discharge port 25 is an exhaust port for discharging the exhaust gas of the electric furnace 1 and is connected to an intake device such as a dust collector (not shown). By this intake device, the atmosphere in the slag holding furnace 2 is maintained in a negative pressure state. The slag inlet 26 is an opening for introducing the molten slag 4 from the upper slag pot 3 into the furnace body 20. An openable / closable furnace lid 27 is installed at the slag inlet 26, and the furnace lid 27 is opened when the molten slag 4 is charged. On the other hand, when the molten slag 4 is not charged, the furnace and the furnace lid 27 are closed and the slag charging port 26 is closed, so that outside air can be prevented from entering the furnace body 20 and the inside of the furnace body 20 can be kept warm.

  The spout portion 21 is a cylindrical portion provided on the electric furnace 1 side of the furnace body 20. The internal space of the spout 21 is a slag injection path 28 for injecting the molten slag 4 from the furnace body 20 into the electric furnace 1, and the opening formed at the tip of the spout 21 is the spout 29. The slag injection path 28 is narrower in the vertical direction and the furnace width direction (perpendicular to the paper surface of FIG. 3) than the internal space of the furnace body 20, and is curved downward as it goes forward in the injection direction. Further, the internal space of the furnace body 20 is gradually narrowed toward the spout portion 21 side. The shape of the furnace body 20 and the spout portion 21 is suitable for adjusting the injection amount when the molten slag 4 in the furnace body 20 is injected into the electric furnace 1.

  The spout 21 of the slag holding furnace 2 is connected to the slag inlet 14 of the electric furnace 1. In the illustrated example, the slag inlet 14 of the electric furnace 1 is made thicker than the spout 21 and the tip of the spout 21 is inserted into the slag inlet 14. There is a gap. In addition, the connection structure of the spout part 21 and the slag injection port 14 is not limited to such an example, and variously, such as connecting both together airtightly using a bellows or the like, or connecting a filler filled in a gap between the two. Can be changed.

Due to the structure of the slag holding furnace 2, when the dust collector (not shown) is operated with the furnace lid 27 closed, and the atmosphere in the slag holding furnace 2 is brought into a negative pressure state, the slag holding furnace 2 is It functions as an exhaust path for exhaust gas generated in the electric furnace 1. That is, the exhaust gas containing CO and H ₂ generated by the reduction treatment in the electric furnace 1 passes through the slag inlet 14 of the electric furnace 1 and the spout part 21 of the slag holding furnace 2 as shown by arrows in FIG. Then, it flows into the furnace body 20 of the slag holding furnace 2 in a negative pressure state. At this time, since the inside of the slag holding furnace 2 is maintained at a negative pressure, the exhaust gas in the electric furnace 1 is not affected even though outside air may enter through the gap between the connecting portions of the electric furnace 1 and the slag holding furnace 2. There is no leakage from the gap to the outside. Further, the exhaust gas flowing into the slag holding furnace 2 advances into the furnace body 20 and is discharged from the gas discharge port 25, reaches a dust collector (not shown), and is processed.

(Tilt device)
A tilting device 40 is provided on the lower side of the furnace body 20 of the slag holding furnace 2. The tilting device 40 has a function of tilting the slag holding furnace 2 toward the pouring part 21 and injecting the molten slag 4 in the furnace body 20 into the electric furnace 1 from the pouring part 21. The tilting device 40 includes a cylinder 41, support members 42 and 43, a tilting shaft 44, and a carriage 45.

  The cylinder 41 is composed of, for example, a hydraulic cylinder, and generates power for tilting the slag holding furnace 2. The upper end of the cylinder 41 is connected to the lower wall 22 of the furnace body 20 at a position where the slag holding furnace 2 is tiltably spaced toward the electric furnace 1, and the lower end of the cylinder 41 is connected to the upper surface of the carriage 45. The tilting shaft 44 is provided below the spout portion 21 of the slag holding furnace 2 and serves as the central axis of the tilting operation of the slag holding furnace 2. The support members 42 and 43 are coupled to each other by a tilting shaft 44 so as to be rotatable. The upper end of the support member 42 is connected to the lower side of the spout portion 21, and the lower end of the support member 43 is connected to the upper surface of the carriage 45. The slag holding furnace 2 is tiltably supported by the cylinder 41, the support members 42 and 43, and the tilt shaft 44.

  With the tilting device 40 having such a configuration, the slag holding furnace 2 can be tilted between the holding posture (FIG. 3) and the pouring posture (FIG. 4) around the tilting shaft 44. Here, as shown in FIG. 3, the holding posture is a posture when the slag holding furnace 2 holds the molten slag 4 in the furnace body 20 without injecting the molten slag 4 into the electric furnace 1. On the other hand, as shown in FIG. 4, the pouring posture is a posture when the slag holding furnace 2 is tilted toward the spout 21 and the molten slag 4 in the furnace body 20 is poured into the electric furnace 1. .

  When changing the slag holding furnace 2 from the holding position to the pouring position, the cylinder 41 is extended, the rear part of the furnace body 20 is lifted, and the slag holding furnace 2 is tilted toward the electric furnace 1 with the tilting shaft 44 as the center. As a result, as shown in FIG. 4, the position of the spout portion 21 is relatively low with respect to the furnace body 20, so that the molten slag 4 held in the furnace body 20 is moved to the spout portion 21 side. Then, it flows from the spout 29 through the slag injection path 28 and is poured into the electric furnace 1. On the other hand, when changing the slag holding furnace 2 from the pouring posture to the holding posture, the cylinder 41 is contracted to return the furnace body 20 to the holding posture. As a result, as shown in FIG. 3, the position of the spout portion 21 is relatively high with respect to the furnace body 20, and the liquid level of the molten slag 4 in the furnace body 20 is lower than the slag injection path 28. The molten slag 4 is held in the furnace body 20 without being injected into the electric furnace 1.

  Here, when the slag holding furnace 2 is in the pouring posture, the tilting angle of the slag holding furnace 2 can be adjusted by controlling the extension length of the cylinder 41 and the pouring speed of the molten slag 4 can be controlled. In the illustrated example, the tilt angle 423 of the slag holding furnace 2 is set so that the central axis 421 of the support member 42 when the slag holding furnace 2 is in the holding position (FIG. 3) and the slag holding furnace 2 is in the injection position (FIG. 4). ) Is defined as an angle formed by the central axis 422 of the support member 42. The greater the tilt angle 423, the lower the position of the spout portion 21 with respect to the furnace body 20, and the molten slag 4 is injected into the electric furnace 1 at a high injection speed.

  The trolley | bogie 45 supports the tilting apparatus 40 so that a movement is possible. By using the carriage 45 to move the slag holding furnace 2 backward or forward, the slag holding furnace 2 can be easily inspected, replaced, or repaired.

  As described above, by tilting the slag holding furnace 2 using the tilting device 40, it is possible to inject the molten slag 4 into the electric furnace 1 intermittently or to control the injection amount. When injecting the molten slag 4 into the electric furnace 1, an appropriate amount of injection is used using the tilting device 40 so that the injected molten slag 4 does not rapidly react with the molten iron in the electric furnace 1 and overflow from the electric furnace 1. It is preferable to inject the molten slag 4 intermittently while controlling (i.e., adjusting the tilt angle 423 of the slag holding furnace 2). If the injection speed is too high during the injection of the molten slag 4, the molten slag 4 may be in a forming state in the electric furnace 1, and overflow may occur. In this case, the tilt angle 423 of the slag holding furnace 2 is decreased by the tilting device 40 and the injection of the molten slag 4 is temporarily stopped, or the injection amount is reduced to calm the reaction in the electric furnace 1. Is preferable.

  In addition, as a method of injecting the molten slag 4 intermittently from the slag holding furnace 2 to the electric furnace 1, a method of injecting the molten slag 4 while repeating injection and interruption of the molten slag 4 or in the slag holding furnace 2 at a predetermined time interval. There is a method of injecting a predetermined amount of molten slag 4 held in a batch, and any method may be employed in the embodiment of the present invention. It is also possible to continuously inject molten slag 4 from the slag holding furnace 2 into the electric furnace 1. In addition, when injecting molten slag 4 intermittently, confirm beforehand by experiment etc. that the total amount of molten slag 4 to be injected all at once is an amount that does not cause overflow due to slag forming. Is desirable.

(Control device)
A control device 50 is connected to the tilting device 40 described above. The control device 50 includes a tilt control unit 51 that controls the tilting device 40 during the injection of the molten slag 4 to adjust the injection speed of the molten slag 4. The tilt control unit 51 can be realized as, for example, a control circuit or a computer that executes a program stored in a memory by a CPU (Central Processing Unit). The tilt control unit 51 may include an output device such as a monitor for presenting information to the operator, and an input device such as a button for acquiring an operation input of the operator.

  The tilt control unit 51 calculates a planned cumulative injection amount when the molten slag is injected at a target injection speed corresponding to the reduction processing capacity of the electric furnace 1, and based on the difference between the actual cumulative injection amount and the planned cumulative injection amount. And having a function of adjusting the injection rate of the molten slag.

  Here, the reduction capacity of the electric furnace is calculated according to the amount of power supplied to the electric furnace 1, more specifically, the amount of power applied to the electrodes 15 and 16 of the electric furnace 1. Means a large amount of molten slag. Since the amount of power supplied to the electric furnace 1 is notified from the power control unit 52, the reduction capacity of the electric furnace 1 is calculated based on the amount of supplied power, and the molten slag 4 corresponding to the reduction capacity of the electric furnace 1 is calculated. The target injection rate can be determined. Based on the target injection speed of the molten slag 4 and the planned injection time, the planned cumulative injection amount at the injection time is calculated.

  On the other hand, the actual cumulative injection amount of the molten slag 4 means the cumulative value of the amount of molten slag 4 injected into the electric furnace 1, and the mass of the slag holding furnace 2 including the molten slag 4 as described later. The amount of change can be measured by the weigher 55. The tilt control unit 51 is configured to reduce the difference based on the difference between the planned cumulative injection amount calculated based on the target injection speed of the molten slag 4 and the actual cumulative injection amount of the molten slag 4. Adjust the injection rate of 4. Details of this adjustment control will be described later.

  In the present specification, the “injection speed of the molten slag 4” means an injection amount of the molten slag 4 per unit time. In the case where the molten slag 4 is intermittently injected at a predetermined time interval, for example, the injection speed is defined as an average injection amount of one injection cycle.

  Similarly to the tilt control unit 51, the power control unit 52 is also realized as a computer in which a CPU executes a program stored in a control circuit or memory, for example. The power control unit 52 controls the amount of power supplied to the electric furnace 1 based on the temperatures of the molten slag layer 5 and the molten iron layer 6 measured by, for example, thermometers 53 and 54. For example, when the temperature of the molten slag layer 5 or the molten iron layer 6 exceeds a predetermined value and is about to be overheated, the power control unit 52 decreases the amount of power supplied to the electric furnace 1 so that the molten slag layer 5 Alternatively, overheating of the molten iron layer 6 is prevented. In such a case, the tilt control unit 51 recalculates the target injection speed of the molten slag 4 in accordance with the fluctuation in the amount of power supplied to the electric furnace 1 notified from the power control unit 52.

  On the other hand, the tilt control unit 51 integrates the injection amount of the molten slag 4 based on the amount of time change of the mass of the slag holding furnace 2 including the internal molten slag 4 measured by the weighing instrument 55. The actual cumulative injection amount is calculated. The tilt control unit 51 compares the actual cumulative injection amount with the planned cumulative injection amount when it is assumed that the molten slag 4 is continuously injected at a predetermined target injection speed, and the molten slag 4 is reduced so as to reduce this difference. Adjust the injection rate. That is, the tilt control unit 51 adjusts the tilt angle 423 of the slag holding furnace 2 based on the above difference.

  In addition, when the difference between the actual cumulative injection amount and the planned cumulative injection amount is large, slag is difficult to be injected due to adhesion of solidified slag to the spout portion of the slag holding furnace 2. it is conceivable that. In that case, the tilt control unit 51 adjusts the tilt angle 423 to a larger angle so that the actual cumulative injection amount approaches the planned cumulative injection amount.

  Even when the predetermined amount of molten slag 4 is not injected from the slag holding furnace 2 to the electric furnace 1 at a predetermined inclination angle 423 by the control of the tilt control unit 51, the injection speed of the molten slag 4 is increased. And the reduction capacity of the electric furnace 1 can be balanced, and the reduction reaction in the electric furnace 1 can be stabilized.

  However, if the molten slag 4 injected from the slag holding furnace 2 into the electric furnace 1 does not recover to the predetermined amount even by the control by the tilt control part 51 as described above, the electric power control part 52 is in the electric furnace. The reduction capacity of the electric furnace 1 is temporarily reduced by reducing the amount of power supplied to 1. As a result, the target injection speed of the molten slag 4 based on the reduction capacity of the electric furnace 1 is reduced, and as a result, the difference between the actual cumulative injection amount and the planned cumulative injection amount can be reduced. When the difference between the actual cumulative injection amount and the planned cumulative injection amount becomes sufficiently small, the temporary change of the control values such as the tilt angle 423 and the power supply amount is returned to the original value, and the originally planned power Control at the target injection rate calculated based on the supply amount and the power supply amount is resumed.

[4. Calculation of slag target injection speed]
Next, with reference to FIG. 5 and FIG. 6, calculation of the target injection speed of molten slag in the present embodiment will be described. FIG. 5 is a diagram for explaining calculation of the target injection rate of the molten slag 4 in the present embodiment.

As shown in FIG. 5, the target injection speed V _t of the molten slag 4 is calculated based on the effective power P _eff calculated from the supplied power P _act . Hereinafter, each calculation process will be described in more detail.

The supplied power P _act is the amount of power supplied per unit time to the electric furnace 1 by the power control unit 52. The power control unit 52 basically controls the supplied power _Pact to be constant at a predetermined value, but the thermometer indicates that the temperature of the molten slag layer 5 or the molten iron layer 6 has exceeded a predetermined value as described above. When detected by 53, 54, the supply power _Pact is decreased. The power control unit 52 notifies the tilt control unit 51 of the value of the supply power P _act when, for example, the control of the supply power P _act is started and when the supply power P _act is changed.

The tilt control unit 51 calculates the effective power P _eff based on the notified supply power P _act . The effective power P _eff is calculated by subtracting the circuit loss power P _loss1 and the heat loss power P _loss2 from the supply power P _act . Here, the circuit loss power P _loss1 is a power corresponding to a circuit loss in the electric system of the electric furnace 1, and can be calculated based on a resistance value of the electric system, a secondary current value flowing through the electric system, or the like. The heat loss power P _loss2 is electric power corresponding to the heat released from the furnace body of the electric furnace 1 to the outside, and the heat radiation amount from each of the furnace bottom 11, the furnace wall 12, and the furnace lid 13 of the electric furnace 1, And can be calculated based on the amount of heat of exhaust gas.

Note that the values of the circuit loss power P _loss1 and the heat loss power P _loss2 used for the calculation of the effective power P _eff in the tilt control unit 51 are quantified in advance by actual measurement or the like and stored in the tilt control unit 51, for example. Also good. Alternatively, fixed values based on actual measurement results may be used as the values of the circuit loss power P _loss1 and the heat loss power P _loss2 .

Further, the tilt control unit 51 calculates the target injection speed V _t based on the effective power P _eff . Here, the target injection speed V _t (kg / min) is obtained by dividing the effective power P _eff (kW) by the power unit r _C (kW · min / kg). The electric power consumption unit r _C expresses the energy required for the reduction reaction of the molten slag 4 in the electric furnace 1 as the amount of electric power per unit mass. As the electric power unit, a fixed value based on an actual measurement result or the like may be used in addition to the theoretical calculation value by the reduction heat of the oxide in the slag per unit slag amount.

Through the calculation process as described above, the tilt control unit 51 calculates the target injection speed V _t of the molten slag 4. Furthermore, based on the calculated target injection rate V _t, (input amount per unit time) poured speed of the auxiliary raw materials such as carbonaceous material to be charged into the electric furnace 1 are preferably determined.

Figure 6 is a graph showing the relationship of the relationship between the target injection rate V _t of the supplied power P _act and the molten slag 4, and the cumulative amount of power supply and the expected cumulative injection amount of the molten slag in the embodiment. In the example shown in FIG. 6 (A), at time t, the power control unit 52 to supply power _{P act,} it is changed from _{P act1} small _{P act2} than _{P act1.} The tilt control unit 51 notified of the changed supply power P _act2 from the power control unit 52 re-executes the calculation of the target injection speed V _t based on the supply power P _act2, and based on the result, the injection rate _{V t,} to change from _{V t1} to a smaller _{V t2} than _{V t1.} Here, the target injection rate _{V t1, V t2,} because they are calculated respectively on the basis of the supply to the electric furnace 1 power _{P act1, P act2,} is a target injection speed corresponding to the reduction capability of the electric furnace 1 . As a result, as shown in FIG. 6B, after the time t, as the increase in the cumulative power supply amount becomes gentle, the increase in the planned cumulative injection amount of the molten slag 4 also becomes gentle. Therefore, when the supply power _Pact to the electric furnace 1 is suppressed and the reduction processing capacity is reduced, the molten slag 4 corresponding to the reduced reduction processing capacity is injected into the electric furnace 1, Subsequently, stable reduction treatment can be performed in the electric furnace 1.

[5. Adjustment control of injection speed according to the actual cumulative injection amount of molten slag]
Next, with reference to FIGS. 7-9, the adjustment control of the injection | pouring speed | rate according to the performance accumulation injection | pouring amount of the molten slag in this embodiment is demonstrated. FIG. 7 is a flowchart showing an example of adjustment control of the injection rate of the molten slag 4 in the present embodiment.

In the illustrated example, first, the tilt control unit 51 calculates a planned cumulative injection amount Q _plan of the molten slag 4 (step S101). Expected cumulative injection amount Q _plan is from time t _a to time t _b, the molten slag when the slag 4 is continuously injected at a target injection rate V _t that is calculated by the calculating process as depicted in Figure 5 of the 4 is an integral value of the injection amount. Therefore, the estimated cumulative injection amount Q _plan can be expressed as, for example, Equation 1 below. V _t (t) represents a value at each time t of the target injection speed V _t as exemplified in FIG. 6A, for example.

Next, the tilt control unit 51 calculates the actual cumulative injection amount Q _act of the molten slag 4 (step S103). Actual cumulative injection amount Q _act are actual values of the injection amount of the molten slag 4 between, for example, from time t _a to time t _b. In the period from time t _a to time t _b Without introduction of molten slag 4 from the slag pot 3 to the slag holding furnace 2, the actual cumulative injection amount Q _act was determined by weighing 55, and time t _a as the mass change of the slag holding furnace 2 between the time t _b (amount corresponding mass of the electric furnace 1 is injected into the molten slag 4 is decreased), for example expressed as equation 2 below. W (t) represents the mass of the slag holding furnace 2 at each time t.

Then, the tilt control unit 51 compares the actual cumulative injection amount _{Q act} of molten slag 4 scheduled cumulative injection amount _{Q plan} (step S105, S107). Here, when the actual cumulative injection amount Q _act is lower than the planned cumulative injection amount Q _plan and the difference between these injection amounts (| Q _Plan −Q _act |) exceeds the threshold th1 (in the case of YES in step S105). The tilt control unit 51 executes control for increasing the injection speed (step S120). Details of the control in step S120 will be described later.

On the other hand, when the actual cumulative injection amount Q _act exceeds the planned cumulative injection amount Q _plan and the difference between these injection amounts (| Q _plan −Q _act |) exceeds the threshold th2 (in the case of YES in step S107), The tilt control unit 51 executes control for reducing the injection speed (step S140). The specific control content in step S140 will also be described later. The threshold value th2 may be the same value as the threshold value th1 or a different value. Note that a threshold used as a condition for controlling the injection rate, such as the thresholds th1 and th2, is also referred to as a first threshold in this specification.

Step S105, if it is determined that either NO in S107 in the appropriate range for actual cumulative injection amount _{Q act} of molten slag 4 plan cumulative injection amount _{Q plan} (range difference is a predetermined threshold) Therefore, the tilt control unit 51 does not execute the injection speed adjustment control.

  FIG. 8 is a flowchart showing an example of control for increasing the injection rate of the molten slag 4 in the present embodiment. The illustrated control process corresponds to the process described as step S120 in the flowchart of FIG.

In the illustrated example, first, the cylinder 41 is extended to increase the tilt angle 423 of the slag holding furnace 2 (step S121). Here, the control of the extension length of the cylinder 41 may be automatically executed by the tilt control unit 51, or the actual cumulative injection amount Q _act or the planned cumulative injection amount Q displayed on the monitor of the tilt control unit 51. _It may be executed in accordance with an operation input given to the tilt control unit 51 by an operator who refers to information such as “ _plan” .

  The tilt angle 423 is a control value for the injection rate of the molten slag 4. That is, if the tilt angle 423 is increased, the injection rate of the molten slag 4 is also expected to increase. However, as described above, the molten slag 4 is not necessarily melted due to the slag solidified and adhered to the inner surface of the slag holding furnace 2. The injection rate of the slag 4 may not increase as expected.

Therefore, after increasing the tilt angle 423 in step S121 described above, the tilt control unit 51 again the difference between the actual cumulative injection amount _{Q act} of molten slag 4 scheduled cumulative injection amount _{Q plan (| Q plan -Q act} |) Is calculated, and it is determined whether or not the difference is larger than the threshold th3 (step S123). The threshold th3 is a value larger than the threshold th1.

When it is determined in step S123 that the difference is larger than the threshold th3 (YES), the injection speed of the molten slag 4 is not sufficiently increased by increasing the tilt angle 423 in step S121, and the tilt angle 423 is increased. It is presumed that the difference between the actual cumulative injection amount _Qact and the planned cumulative injection amount _Qplan has increased even after the increase. In this case, the power control unit 52 executes control to reduce the power supply _Pact supplied to the electric furnace 1 (step S125). Note that a threshold used as a condition for executing control of supplied power, such as the threshold th3, is also referred to as a second threshold in this specification. The second threshold value is larger than the first threshold value.

Here, the control of the supplied power P _act by the power control unit 52 may be automatically executed by transmitting a control signal from the tilt control unit 51, or the results displayed on the monitor of the tilt control unit 51. It may be executed according to an operation input given to the tilt control unit 51 or the power control unit 52 by an operator who refers to information such as the cumulative injection amount _Qact and the planned cumulative injection amount _Qplan . Further, the control of the supplied power P _act by the power control unit 52 in step S125 may be executed, for example, by setting the supplied power P _act to 0 (power off), or by reducing the supplied power P _act by a predetermined decrease width. The supply of power may be performed by continuing while decreasing.

Next, the tilt control unit 51 calculates again the difference (| Q _plan −Q _act |) between the actual cumulative injection amount Q _act and the planned cumulative injection amount Q _plan of the molten slag 4, and whether or not the difference has become zero. Is determined (step S127). Increase in tilt angle 423 in step S121, and by a decrease of the supply power _{P act} at step S125, the difference between the expected cumulative injection amount _{Q plan} and actual cumulative injection amount _{Q act} of molten slag 4 approaches zero shrinking It is expected to be. When the difference becomes 0 (or falls to a predetermined range close to 0), the tilt control unit 51 restores control values such as the tilt angle 423 and the supplied power P _act (step S129).

  FIG. 9 is a flowchart showing an example of control for reducing the injection rate of the molten slag 4 in the present embodiment. The illustrated control process corresponds to the process described as step S140 in the flowchart of FIG.

In the illustrated example, first, the cylinder 41 is contracted to decrease the tilt angle 423 of the slag holding furnace 2 (step S141). Here, similarly to step S121 shown in FIG. 8 above, the control of the extension length of the cylinder 41 may be automatically executed by the tilt control unit 51, for example, or displayed on the monitor of the tilt control unit 51. The operation may be executed according to an operation input given to the tilt control unit 51 by an operator who refers to information such as the actual cumulative injection amount _Qact and the planned cumulative injection amount _Qplan .

Next, the tilt control unit 51 calculates again the difference (| Q _plan −Q _act |) between the actual cumulative injection amount Q _act and the planned cumulative injection amount Q _plan of the molten slag 4, and whether or not the difference has become zero. Is determined (step S143). Due to the decrease of the tilt angle 423 in step S141, the difference between the actual cumulative injection amount _{Qact of} the molten slag 4 and the planned cumulative injection amount _Qplan is expected to decrease and approach zero. The tilt control unit 51 returns the tilt angle 423 to the original when the difference becomes 0 (or falls to a predetermined range close to 0) (step S145).

In the control process illustrated in FIG. 9, control of the supplied power P _act by the power control unit 52 is not executed. This is because, in many cases, the supply power P _act in normal times is often set near the upper limit of the safe operating range, and the actual cumulative injection amount Q _{act of} the molten slag 4 is too large. This is because it is not easy to increase the supplied power P _act . Further, when the actual cumulative injection amount of the molten slag 4 Q _act is small (smaller than the actual injection rate is the target injection rate V _t) is, increasing the tilt angle 423, solidified slag holding furnace 2 while there is a possibility that the injection rate does not increase because of such slag adhering to the inner surface (larger than the actual injection rate is the target injection rate V _t) actual cumulative injection amount Q _act often the molten slag 4 when If the tilt angle 423 is decreased, the injection speed is likely to decrease. However, in the case where the normal supply power _Pact is set with a margin with respect to the safe operating range, the power control is performed as in step S125 shown in FIG. The unit 52 may control the supplied power P _act . In this case, the threshold value (second threshold value) used as a condition for executing the control of the supplied power is larger than the threshold value th2 (first threshold value) used as the condition for executing the control for decreasing the injection rate. It is.

Next, examples of the present invention will be described. In addition, the following Examples are only the example conditions adopted in order to confirm the implementability and effect of this invention, and this invention is not limited to the conditions of the following Examples.

Example 1
First, Embodiment 1 of the present invention will be described with reference to FIG. In Example 1, a closed DC electric furnace was used as the electric furnace 1. As the molten slag 4, molten molten slag discharged from the converter was used, and the molten slag 4 was put into the slag holding furnace 2 in a molten state having fluidity. Furthermore, in the electric furnace 1, there is a molten iron layer 6 made of about 130 tons of pig iron, and a molten slag layer 5 made of reduced molten slag (reduced slag) about 200 mm thick on the molten iron layer 6. Under such conditions, molten slag 4 is intermittently injected from the slag holding furnace 2 into the molten slag layer 5 in the electric furnace 1, and power of 30 MW is applied to the electrodes 15 and 16 of the electric furnace 1 to The molten slag 4 was reduced in the furnace 1.

FIG. 10 is a graph showing the relationship between the power supplied to the electric furnace 1, the injection speed of the molten slag 4, and the cumulative injection amount of the molten slag 4 in the present embodiment. In this example, from time 0, the supply power P _act to the electric furnace 1 was set to 30 MW, and the reduction treatment of the molten slag 4 was started. At this time, the target injection speed V _t of the molten slag 4 from the slag holding furnace 2 was set to 800 kg / min as a result of the calculation shown in FIG. Since the target injection speed V _t is calculated based on the electric power P _act supplied to the electric furnace 1, the target injection speed V _t is a target injection speed corresponding to the reduction processing capability of the electric furnace 1. In addition, as electric power corresponding to the circuit loss and the heat loss in the electric furnace 1, a fixed value of 9 MW is adopted based on the result of actual measurement.

At the start of the process, the cylinder 41 was extended to tilt the slag holding furnace 2 at a tilt angle 423 corresponding to the target injection speed V _t (800 kg / min). In FIG. 10, the target value (thick line) of the molten slag injection speed As shown by the actual value (thin line), the molten slag 4 could be injected at an injection rate close to the target injection rate V _t (800 kg / min) if averaged with slight fluctuations. Therefore, in the molten slag cumulative injection amount shown in FIG. 10, the actual value almost coincides with the planned value (thick line) (therefore, the thin line indicating the actual value is not shown).

However, at time t1 (21 minutes), the temperature of the molten slag layer 5 and the molten iron layer 6 rises by about 100 ° C. from the specified values (the molten slag layer 5 is about 1450 ° C. and the molten iron layer 6 is about 1550 ° C.). since that some detected by the thermometer 53, the power control unit 52 changes the supply power _{P act} to the electric furnace 1 from 30MW to 15 MW. Accordingly, the tilt control unit 51 re-executes the calculations, changing the target injection rate _{V t} of molten slag 4 to 350 kg / min. Correspondingly, the tilt control unit 51 contracts the cylinder 41 to reduce the tilt angle 423 of the slag holding furnace 2 to a value corresponding to the target injection speed V _t after the change. The molten slag 4 could be injected at an injection speed close to the target injection speed V _t (350 kg / min).

After that, at time t2 (27 minutes), the temperature of the molten slag layer 5 and the molten iron layer 6 has dropped to around a prescribed value (in this embodiment, within a range of about ± 25 ° C.). the supply power _{P act} to the electric furnace 1 was returned from 15MW to 30 MW. Accordingly, the tilt control unit 51 returns the target injection rate _{V t} of molten slag 4 from 350 kg / min to 800 kg / min. Again, on average, the molten slag 4 could be injected at an injection rate close to the target injection rate V _t (800 kg / min). In the present embodiment, the process is terminated at time t3 (41 minutes), but the process can actually be continued for a longer time.

In this embodiment, by calculating the target injection rate V _t on the basis of the supplied power P _act to the electric furnace 1, regardless of the variations in the supply power P _act, the target injection in accordance with the reduction capacity of the electric furnace 1 it was possible to inject a molten slag 4 at a speed V _t. As a result, it was possible to continuously and stably reduce the molten slag 4 in the electric furnace 1 without causing rapid slag forming during slag injection.

(Example 2)
Next, Embodiment 2 of the present invention will be described with reference to FIG. Also in this embodiment, under the same conditions as in Example 1, for although in an electric furnace 1 was subjected to a reduction treatment of the slag 4, the actual injection rate of the molten slag 4 was far below the target injection rate V _t, The injection speed adjustment control by the tilt control unit 51 was executed.

FIG. 11 is a graph showing the relationship between the power supplied to the electric furnace 1, the injection rate of the molten slag 4, and the cumulative injection amount of the molten slag 4 in this embodiment. Also in this example, similarly to the first example, from time 0, the supply power P _act to the electric furnace 1 was set to 30 MW, and the reduction treatment of the molten slag 4 was started. In this case, the target injection rate _{V t} of molten slag 4 as a result of the calculation as shown in FIG. 5 above, was set at 800 kg / min. As the power corresponding to the circuit loss and heat loss in the electric furnace 1, a fixed value of 9 MW is adopted as in the first embodiment. However, even if the cylinder 41 is extended and the slag holding furnace 2 is tilted at the tilt angle 423 corresponding to the target injection speed V _t (800 kg / min), the target value (thick line) of the molten slag injection speed in FIG. as indicated by the actual value (thin line), the actual injection rate of the molten slag 4 was far below the target injection rate V _t.

As a result, as shown by the target value (thick line) and the actual value (thin line) of the molten slag cumulative injection amount, a difference occurs between the actual cumulative injection amount Q _act of the molten slag 4 and the planned cumulative injection amount Q _plan. Gradually expanded. Then, at time t1 (10 min), the difference between the actual cumulative injection amount _{Q act} scheduled cumulative injection amount _{Q plan} is, due to exceeding the threshold th1 described with reference to FIG. 7, the tilt control unit 51, the slag holding furnace Control was performed to increase the tilt angle 423 of 2 to an angle corresponding to an injection speed of 1200 kg / min.

However, still, the actual injection rate of the molten slag 4 is lower than the target injection speed V _t, the difference between the actual cumulative injection amount Q _act scheduled cumulative injection amount Q _plan of molten slag 4 was further expanded. At time t2 (21 minutes), the difference between the actual cumulative injection amount _{Q act} scheduled cumulative injection amount _{Q plan} is, since even exceeds the threshold th3 described in FIG. 8, the power control unit 52 to the electric furnace 1 Control was performed to reduce the supplied power P _act to zero.

As a result, as a result of the planned cumulative injection amount Q _plan no longer increasing, the difference from the actual cumulative injection amount Q _act is reduced, and the difference becomes zero at time t3 (27 minutes). The power control unit 52 restored the tilt angle 423 and the supplied power _Pact . Specifically, the tilt control unit 51 returns the tilt angle 423 to an angle corresponding to an injection speed of 800 kg / min, and the power control unit 52 resumes the supply of power to the electric furnace 1 with the supply power P _act being 30 MW. .

However, after that, the actual injection speed of the molten slag 4 is lower than the target injection speed V _t , and at the time t4 (32 minutes), the difference between the actual cumulative injection quantity _Qact and the planned cumulative injection quantity _Qplan is The threshold value th1 was exceeded again. Here, similarly to time t1, when the tilt control unit 51 performs control to increase the tilt angle 423 of the slag holding furnace 2 to an angle corresponding to the injection rate of 1200 kg / min, this time the injection rate of the molten slag 4 increases. On average, the molten slag 4 was injected at an injection rate of about 1200 kg / min.

As a result, the difference between the actual cumulative injection amount _Qact and the planned cumulative injection amount _Qplan has decreased, and the difference has become zero at time t5 (39 minutes), so that the tilt control unit 51 tilts the slag holding furnace 2. The angle 423 was returned to an angle corresponding to an injection rate of 800 kg / min. Thereafter, the process was completed at time t6 (41 minutes) without causing a large difference between the actual cumulative injection amount _Qact and the planned cumulative injection amount _Qplan .

In the present embodiment, although the actual injection rate of molten slag 4 is significantly lower than the target injection rate V _t calculated based on the power supply P _act supplied to the electric furnace 1, the actual cumulative injection amount Q _act And control the tilt angle 423 of the slag holding furnace 2 to increase the injection speed of the molten slag 4 based on the difference between the estimated cumulative injection amount _Qplan and the supply power _Pact to the electric furnace 1 By temporarily suppressing the reduction treatment capacity of the electric furnace 1, it was possible to prevent further increase in the difference between the actual cumulative injection amount _Qact and the planned cumulative injection amount _Qplan . As a result, it was possible to continuously and stably reduce the molten slag 4 in the electric furnace 1 without causing rapid slag forming during slag injection.

(Example 3)
Next, Embodiment 3 of the present invention will be described with reference to FIG. Also in this embodiment, under the same conditions as in Example 1, for although in an electric furnace 1 was subjected to a reduction treatment of the slag 4, the actual injection rate of the molten slag 4 greatly exceeded the target injection rate V _t, The injection speed adjustment control by the tilt control unit 51 was executed.

FIG. 12 is a graph showing the relationship between the power supplied to the electric furnace 1, the injection speed of the molten slag 4, and the cumulative injection amount of the molten slag 4 in this embodiment. Also in this example, similarly to the first example, from time 0, the supply power P _act to the electric furnace 1 was set to 30 MW, and the reduction treatment of the molten slag 4 was started. In this case, the target injection rate _{V t} of molten slag 4 as a result of the calculation as shown in FIG. 5 above, was set at 800 kg / min. As the power corresponding to the circuit loss and heat loss in the electric furnace 1, a fixed value of 9 MW is adopted as in the first and second embodiments. However, when the cylinder 41 is extended and the slag holding furnace 2 is tilted at the tilt angle 423 corresponding to the target injection speed V _t (800 kg / min), the target value (thick line) of the molten slag injection speed in FIG. as indicated by the actual value (thin line), the actual injection rate of the molten slag 4 greatly exceeded the target injection rate V _t.

As a result, as shown by the target value (thick line) and the actual value (thin line) of the molten slag cumulative injection amount, a difference occurs between the actual cumulative injection amount Q _act of the molten slag 4 and the planned cumulative injection amount Q _plan. Gradually expanded. At time t1 (11 minutes), the difference between the actual cumulative injection amount _Qact and the planned cumulative injection amount _Qplan exceeds the threshold value t2 described in FIG. The control was performed by reducing the tilt angle 423 of 2 and returning the slag holding furnace 2 to the holding posture. As a result, the injection speed of the molten slag 4 became zero as shown in the figure.

As a result, the actual cumulative injection amount Q _act no longer increases. As a result, the difference from the planned cumulative injection amount Q _plan is reduced, and the difference becomes zero at time t2 (18 minutes). The tilt angle 423 was again set to an angle corresponding to the target injection speed V _t (800 kg / min), and the injection of the molten slag 4 was resumed. Thereafter, if the actual injection speed of the molten slag 4 is averaged, it is stabilized at about 800 kg / min, and there is no significant difference between the actual cumulative injection amount _Qact and the planned cumulative injection amount _Qplan, and the time t3 The processing was completed at (41 minutes).

In this embodiment, although the actual injection rate of the molten slag 4 greatly exceeds the target injection rate V _t calculated based on the power supply P _act supplied to the electric furnace 1, the actual cumulative injection amount Q _act will by controlling the tilt angle 423 of the slag holding furnace 2 on the basis of the difference between the cumulative injection amount Q _plan, to prevent further expansion of the difference between the actual cumulative injection amount Q _act scheduled cumulative injection amount Q _plan and I was able to. As a result, it was possible to continuously and stably reduce the molten slag 4 in the electric furnace 1 without causing rapid slag forming during slag injection.

From the above results, the target injection speed V _t of the molten slag 4 is set according to the reduction processing capacity of the electric furnace, and the planned cumulative injection amount Q _plan calculated based on the target injection speed V _t and the molten slag by adjusting the injection rate of the molten slag 4 based on 4 of the difference between the actual cumulative injection amount Q _act, if for example such as the actual injection rate of the molten slag 4 for some reason deviates from the target injection rate V _t In addition, it has been demonstrated that the molten slag 4 can be reduced continuously and stably in the electric furnace 1.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. 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 2 Slag holding furnace 3 Slag pan 4 Molten slag 5 Molten slag layer 6 Molten iron layer 14 Slag inlet 15 Upper electrode 16 Furnace electrode 17 Outlet 18 Outlet 40 Tilting device 41 Cylinder 42, 43 Support member 421 422 Central axis 423 Tilt angle 44 Tilt axis 50 Control device 51 Tilt controller 52 Power controller 53, 54 Thermometer 55 Weigher

Claims (4)

The molten slag produced in the steel making process was put into the slag holding furnace molten state, the molten slag layer in the electric furnace for containing a molten slag layer which is formed on the soluble iron layer the molten iron layer, Injecting the molten slag from the slag holding furnace , continuously reducing the molten slag in the electric furnace, and recovering valuable materials in the molten slag in the molten iron layer,
When adjusting the injection speed of the molten slag and the electric power supplied to the electric furnace, the actual cumulative injection amount by the injection of the molten slag is measured,
Calculate the planned cumulative injection amount when the molten slag is injected at a target injection rate according to the reduction capacity of the electric furnace,
Based on the difference between the actual cumulative injection amount and the planned cumulative injection amount,
By controlling the tilt angle of the slag holding furnace by tilting means for tilting the slag holding furnace to inject the molten slag into the electric furnace when the difference exceeds a first threshold, Adjust the injection rate of molten slag ,
When the difference exceeds a second threshold value that is larger than the first threshold value, further based on the effective power obtained by subtracting the power corresponding to the circuit loss and heat loss in the electric furnace from the power supplied to the electric furnace. A slag treatment method for calculating a reduction treatment capacity of the electric furnace and adjusting a power supplied to the electric furnace . The electric furnace is
It has a tap and a tap.
When the layer thickness of the molten slag layer reaches a predetermined layer thickness, the reduced slag of the molten slag layer is discharged from the tap outlet,
When the interface of the molten iron layer approaches the outlet, the molten iron of the molten iron layer is discharged from the outlet,
The reduction treatment of the molten slag is continued without interruption,
The slag processing method according to claim 1. The molten slag produced in the steel making process was put into the slag holding furnace molten state, the molten slag layer in the electric furnace for containing a molten slag layer which is formed on the soluble iron layer the molten iron layer, Injecting the molten slag from the slag holding furnace , continuously reducing the molten slag in the electric furnace, and recovering valuable materials in the molten slag in the molten iron layer,
Measuring means for measuring the actual cumulative injection amount due to the injection of the molten slag when adjusting the injection speed of the molten slag and the electric power supplied to the electric furnace ;
Calculate the planned cumulative injection amount when the molten slag is injected at a target injection rate according to the reduction capacity of the electric furnace,
Based on the difference between the actual cumulative injection amount and the planned cumulative injection amount,
By controlling the tilt angle of the slag holding furnace by tilting means for tilting the slag holding furnace to inject the molten slag into the electric furnace when the difference exceeds a first threshold, Injection rate control means for adjusting the injection rate of the molten slag ;
When the difference exceeds a second threshold value that is larger than the first threshold value, further based on the effective power obtained by subtracting the power corresponding to the circuit loss and heat loss in the electric furnace from the power supplied to the electric furnace. Calculating the reduction processing capacity of the electric furnace and adjusting the power supplied to the electric furnace ;
Ru equipped with, slag processing equipment. The electric furnace is
It has a tap and a tap.
Reduced slag discharge means for discharging the reduced slag of the molten slag layer from the outlet when the thickness of the molten slag layer reaches a predetermined layer thickness;
A molten iron discharging means for discharging the molten iron of the molten iron layer from the tap hole when the interface of the molten iron layer approaches the tap hole;
The reduction treatment of the molten slag is continued without interruption,
The slag processing apparatus according to claim 3 .

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