JP6295692B2 - Steelmaking slag treatment method - Google Patents

Description

  The present invention relates to a steelmaking slag treatment method for treating steelmaking slag generated in a steelmaking process for removing impurities in hot metal.

In the steel making process, impurities such as silicon (Si), phosphorus (P), and carbon (C) in the hot metal are removed. In this converter steelmaking process, desiliconization, dephosphorization, and decarburization refining are continuously performed as one step, and the slag generated at that time is discharged, and the dephosphorization treatment is performed to remove silicon and phosphorus in hot metal. There is a case where a decarburization treatment step of removing carbon from molten iron is performed after discharging slag generated by performing the step.
In the dephosphorization process described above, a slag is formed by supplying a slagging agent such as quicklime to the hot metal in the reaction vessel, oxygen is blown toward the hot metal and the slag, and impurities in the hot metal are reacted with the slag. Oxygen blowing (oxidation refining) to be removed is performed. In this oxygen blowing, phosphorus is removed from the hot metal by a dephosphorization reaction as represented below at the interface between the slag and the hot metal.
2 [P] + 5Fe ²⁺ + 8O ²⁻ → 2PO ₄ ³⁻ + 5Fe

In addition, in the decarburization process, additional iron-forming agent such as quick lime is supplied to the hot metal after the dephosphorization process as needed, and carbon in the hot metal is removed by blowing oxygen toward the hot metal. ing.
Here, in the dephosphorization process and the decarburization process in the steel making process, slag (steel slag) that reacts with the hot metal is generated. Since this steelmaking slag contains a relatively large amount of iron such as granular iron and iron oxide and phosphoric acid, for example, Patent Document 1-3 proposes a method for recovering valuable metals such as iron and phosphorus from steelmaking slag. Has been.
Patent Document 4 discloses a technique for effectively utilizing steelmaking slag as a metal material for smelting reduction and as a slagging agent.

Japanese Patent Laid-Open No. 52-033897 JP 2009-132544 A Special table 2003-520899 gazette JP 09-272908 A

By the way, in patent document 1, 2, since it aims at collection | recovery of the phosphorus from steelmaking slag, P concentration is high in the collection | recovery metal after processing steelmaking slag. In order to return the recovered metal to the steelmaking process, it is necessary to perform a dephosphorization process, and dephosphorization slag is generated during the dephosphorization process. For this reason, there existed a problem that the generation amount of slag increased as a whole steelmaking process. In this case, the T.I. The Fe concentration was about 0.9 mass%. T. T. The Fe concentration means mass% with respect to the mass of iron slag constituting the iron oxide present in the slag.
Moreover, in patent document 3, although it aims at collection | recovery of the iron content in steelmaking slag, when iron oxide in steelmaking slag is fully reduced (the T.Fe density | concentration in this case slag is 2.2 mass%) Degree), phosphorus and silicon are also reduced and included in the recovered metal. For this reason, it is necessary to perform a dephosphorization process with respect to the collection | recovery metal, and there existed a problem that the generation amount of slag increased as a whole steelmaking process.
Furthermore, Patent Document 4 aims to utilize steelmaking slag as a metal material for smelting reduction and as a slagging agent. The Fe concentration was about 3 mass%.

Furthermore, in the techniques described in Patent Documents 1-4, as described above, the T.S. Since the Fe concentration is lowered, the melting point of the slag increases and the fluidity decreases. Therefore, it is necessary to add SiO ₂ , Al ₂ O _3, etc. to the slag in order to ensure the fluidity of the slag and to facilitate handling such as transferring the slag from the processing furnace to the slag pan etc. There was a problem that the amount of slag increased.

In addition, since the above-mentioned steelmaking slag contains unhatched lime (free CaO), it is known that this free CaO reacts with water to become Ca (OH) _{2 and} volume expands. Then, when using steelmaking slag, in order to suppress the above-mentioned volume expansion, steam aging which makes free CaO Ca (OH) ₂ beforehand may be performed. When performing this steam aging, it is necessary to reduce the particle size of the slag so that the steam is sufficiently supplied to the inside of the slag, so that a large lump of slag could not be obtained.

Furthermore, the dephosphorization slag produced in the dephosphorization process has a low strength because it contains many CO gas bubbles.
From the above, steelmaking slag is mainly used in low-grade applications such as roadbed materials for temporary roads and lower-layer roadbed materials for civil engineering work, and should be used for high-grade applications such as concrete aggregates and upper-layer roadbed materials. I could not.
In addition, since steelmaking slag has a high basicity CaO / SiO ₂ , the pH increases due to elution of Ca ions. Therefore, when using it for civil engineering work, etc., take measures to prevent leakage of high pH water. There was a need.

  This invention is made in view of the situation mentioned above, Comprising: While reducing the generation amount of steelmaking slag, the processing method of the steelmaking slag which can obtain the modified slag which can be used for a wide use is provided. With the goal.

In order to solve the above problems, a steelmaking slag treatment method according to the present invention is a method for treating steelmaking slag generated in a steelmaking process for removing impurities in the hot metal, and charging the steelmaking slag into a converter. Heating and adding a reducing carbon material to obtain a reformed slag and a recovered metal. Before the Fe concentration becomes less than 5 mass%, the reforming treatment step is terminated, so that the P concentration in the recovered metal is 0.01 mass% or less, and thus steel slag generated in the steelmaking process is generated. It is characterized by reducing the amount .

  According to the steelmaking slag treatment method of this configuration, the reforming and reducing treatment step of adding the reducing carbonaceous material to the steelmaking slag is performed in the T.S. Since it complete | finishes before Fe density | concentration becomes less than 5 mass%, it can suppress that P and Si in steelmaking slag can be suppressed, and can suppress P density | concentration and Si density | concentration in collection | recovery metal low. Therefore, it is not necessary to add a slag-forming agent to the recovered metal for the dephosphorization process, and the amount of slag generated can be reduced throughout the steelmaking process.

  Moreover, since the steelmaking slag is reheated, the steelmaking slag is modified, and the basicity of the slag is lowered and free CaO can be slagged. Further, since steam aging can be omitted, it is not necessary to reduce the particle size of the slag, and a large lump reformed slag can be obtained. Further, the obtained modified slag has a sufficient strength because the amount of contained bubbles is reduced. From the above, the obtained modified slag can be used for high-grade applications.

Here, in the steelmaking slag treatment method according to the present invention, the steelmaking process includes a dephosphorization process for removing silicon and phosphorus in the hot metal and a decarburization process for removing carbon from the hot metal. In addition, as the steelmaking slag, one or both of the dephosphorization slag generated in the dephosphorization process and the decarburization slag generated in the decarburization process may be processed.
In this case, the dephosphorization slag generated in the dephosphorization process and the decarburization slag generated in the decarburization process can be modified, and the amount of slag generated can be suppressed and the obtained reforming can be performed. Quality slag can be used for high-grade applications.

Moreover, in the processing method of the steelmaking slag which concerns on this invention, T. in the said reforming slag after the said reforming reduction process process is complete | finished. The Fe concentration is preferably in the range of 5 mass% to 10 mass%.
According to the steel slag treatment method of this configuration, the T.I. content in the reformed slag after the reforming and reducing process is completed. Since the Fe concentration is set to 5 mass% or more, the P concentration in the recovered metal can be reduced, and when returning the recovered metal to the steelmaking process, a fermenting agent is used for dephosphorizing the recovered metal. No need to add. Therefore, the generation amount of slag can be reduced throughout the steel making process. On the other hand, the T.I. Since the Fe concentration is 10 mass% or less, a part of the iron oxide in the steelmaking slag can be reduced and recovered.

In the processing method of the steel slag according to the present invention, the reforming reduction treatment step after completion the reforming the slag basicity of _{(CaO mass%) / (SiO} 2 mass%), and 1.7 or less It is preferable.
According to the steelmaking slag treatment method of this configuration, the basicity (CaO mass% ) / (SiO ₂ mass% ) of the modified slag after completion of the reforming and reducing treatment step is set to 1.7 or less. Even if slag dissolves in water, the pH does not become high, and it is not necessary to take measures against water leakage.

Furthermore, in the steel slag treatment method according to the present invention, it is preferable to transfer the recovered metal after completion of the reforming reduction treatment step into a reaction vessel in which the decarburization treatment step is performed.
According to the steelmaking slag processing method of this configuration, as described above, since the P concentration in the recovered metal is low, the dephosphorization process can be omitted, and the amount of slag generated can be reliably reduced. It becomes.

  As described above, according to the present invention, it is possible to provide a steelmaking slag treatment method that can reduce the amount of steelmaking slag generated and obtain a modified slag that can be used in a wide range of applications.

It is a flowchart which shows an example of the steelmaking process in which the processing method of the steelmaking slag which is this embodiment is implemented. T. in slag It is a graph which shows the relationship between Fe density | concentration and the phosphorus density | concentration (% P) in a metal.

Below, the processing method of the steelmaking slag which is one Embodiment of this invention is demonstrated with reference to attached drawing. In addition, this invention is not limited to the following embodiment.
The steelmaking slag treatment method according to the present embodiment performs the reforming reduction treatment on the steelmaking slag (dephosphorization slag 11, decarburization slag 12) generated in the course of the steelmaking process, thereby recovering the reformed slag 15 and recovery. The metal 16 is obtained. In FIG. 1, an example of the steelmaking process in which the processing method of the steelmaking slag which is this embodiment is implemented is shown.

  In the steelmaking process, as shown in FIG. 1, first, the hot metal generated in the blast furnace is transferred to the converter (converter A), and the hot lime (on the hot metal stored in the converter (converter A)) A slag is formed by adding a slagging agent such as CaO), and oxygen is blown toward the hot metal, thereby removing phosphorus in the hot metal by a reaction between the hot metal and the slag (dephosphorization treatment step S01). In the dephosphorization step S01, Si in the hot metal is also oxidized and taken into the slag. After the dephosphorization process S01 is completed, the dephosphorization slag 11 produced in the dephosphorization process S01 is discharged from the converter (converter A) and temporarily stored in the slag yard.

After the dephosphorization slag 11 is discharged, a slag is formed on the hot metal in the converter (converter A) by adding a slagging agent such as quick lime (CaO) as necessary, toward the hot metal. By blowing oxygen, carbon in the hot metal is removed (decarburization process step S02). In addition, the decarburization slag 12 produced | generated by this decarburization process process S02 is discharged | emitted from a converter (converter A), and is once stored in a slag yard.
In this way, the steelmaking process (dephosphorization treatment step S01, decarburization treatment step S02) removes phosphorus and carbon in the hot metal to obtain molten steel.
Next, the obtained molten steel is made into a slab through a secondary smelting step S03 and a continuous casting step S04.

  Here, the dephosphorization slag 11 produced in the dephosphorization treatment step S01 and the decarburization slag 12 produced in the decarburization treatment step S02 are charged into another converter (converter B) and subjected to the reforming reduction treatment. Is implemented (reforming and reducing treatment step S10). Here, the temperature condition of the reforming reduction treatment step S10 is set in a range of 1350 ° C. or higher and 1500 ° C. or lower. In this reforming reduction treatment step S10, the dephosphorization slag 11 and the decarburization slag 12 may be mixed and charged into the converter (converter B), or the dephosphorization slag 11 and the decarburization slag 12 may be charged. May be charged into the converter (converter B) alone.

In the reforming reduction treatment step S10, the SiO ₂ -containing reforming material and the reducing carbon material (for example, pulverized coal) are added to the dephosphorization slag 11 and the decarburization slag 12 charged in the converter (converter B). Is added and oxygen is supplied to melt the dephosphorization slag 11 and the decarburization slag 12 to perform the reforming reduction treatment. By this reforming and reducing treatment step S10, the dephosphorization slag 11 and the decarburized slag 12 are reformed and reduced, and the reformed slag 15 and the recovered metal 16 are obtained. In the reforming reduction treatment step S10, the molten dephosphorization slag 11 and decarburization slag 12 may be directly supplied.

In the steelmaking slag treatment method according to the present embodiment, the T.S. Before the Fe concentration becomes less than 5 mass%, the reforming reduction treatment step S10 is finished. Further, in the present embodiment, the T.I. The reducing carbonaceous material (for example, pulverized coal) is added so that the Fe concentration falls within the range of 5 mass% to 10 mass%.
Furthermore, in the present embodiment, the basicity (CaO) / (SiO ₂ ) of the reformed slag 15 after the reforming and reducing treatment step S10 ends is 1.7 or less due to SiO ₂ input from the ash of the reducing carbon material. Become.

In addition, the T.V. The Fe concentration can be calculated by analyzing the exhaust gas flow rate, the CO concentration, the CO ₂ concentration, and the H ₂ concentration in the reforming reduction treatment step S10, and by the balance of carbon, hydrogen, and oxygen. Specifically, the total amount of oxygen in CO, the oxygen in CO ₂ and the H ₂ O content obtained by equilibrium calculation balances the amount of oxygen blown in and the total amount of oxygen in the reduced iron oxide, so The reduction state is evaluated from the information, and the T.O. The Fe concentration can be calculated.

Here, T. in the slag. FIG. 2 shows the relationship between the Fe concentration (% T. Fe) and the phosphorus concentration (% P) in the metal. According to FIG. 2, it can be seen that the phosphorus concentration (% P) in the metal increases as the total iron concentration (% T.Fe) in the slag decreases. This is because P is reduced after Fe in the slag is reduced. Since Si in the slag is reduced after P is reduced, the Si concentration is sufficiently low when the P concentration in the recovered metal is low.
In the present embodiment, the T.I. Since the reforming and reducing treatment step S10 is completed before the Fe concentration becomes less than 5 mass%, the P concentration in the recovered metal 16 is low. Specifically, the P concentration is 0.01 mass%. It is as follows. That is, the recovered metal 16 has a P concentration equivalent to that of the hot metal after the dephosphorization process S01.

Therefore, in the present embodiment, the recovered metal 16 obtained in the reforming reduction treatment step S10 is transferred to the converter (converter A) that performs the decarburization treatment step S02.
The reformed slag 15 is discharged from the converter (converter B) and shipped as an upper layer roadbed material, cement aggregate, temporary road material, lower layer roadbed material, or the like.

  According to the steelmaking slag treatment method of the present embodiment configured as described above, a reforming reduction treatment step of adding a reducing carbonaceous material to the steelmaking slag (dephosphorization slag 11, decarburization slag 12). S10 is the T.S. Since it is completed before the Fe concentration becomes less than 5 mass%, it is possible to suppress the reduction of P and Si in the steelmaking slag (dephosphorization slag 11, decarburization slag 12), and the P concentration in the recovered metal 16 , Si concentration is lowered. Therefore, it is not necessary to perform the dephosphorization process on the recovered metal 16, it is possible to suppress the generation of new slag by the dephosphorization process of the recovered metal 16, and it is possible to reduce the amount of slag generated as a whole steelmaking process. It becomes.

  Moreover, since the modified slag 15 is obtained by reheating the steelmaking slag (dephosphorized slag 11, decarburized slag 12), the basicity of the modified slag 15 is lowered and free CaO is slagged. Can do. This makes it possible to omit steam aging. Further, the modified slag 15 can be used for high-grade applications such as upper roadbed materials and cement aggregates.

In the steel slag treatment method according to the present embodiment, the T.V. Since the Fe concentration is in the range of 5 mass% or more and 10 mass% or less, the P concentration and the Si concentration in the recovered metal 16 can be lowered, and the dephosphorization treatment for the recovered metal 16 can be omitted. Further, the T.I. Since the Fe concentration is 10 mass% or less, the iron content in the steelmaking slag (dephosphorization slag 11 and decarburization slag 12) can be reduced and recovered.
Here, T. in the slag. When the Fe concentration exceeds 10 mass%, iron oxide in the slag reacts with C in the molten iron, CO gas is generated in the slag, and the slag tends to become porous. For this reason, in the present embodiment, the T.V. It is desirable that the Fe concentration be 10 mass% or less.

Furthermore, in the steel slag treatment method according to the present embodiment, the basicity (CaO) / (SiO ₂ ) of the modified slag 15 is 1.7 or less, so even if the modified slag 15 comes into contact with water. Since there is little elution of Ca ions, the pH does not become high and there is no need to take measures against water leakage.
In addition, when the basicity (CaO) / (SiO ₂ ) does not become 1.7 or less due to SiO ₂ input from the ash of the reducing carbon material, or when it is desired to further reduce the basicity (CaO) / (SiO ₂ ). May further add a SiO ₂ source as a modifier.

In the steelmaking slag treatment method according to the present embodiment, since the recovered metal 16 is transferred to the decarburizing process S02, the dephosphorization process for the recovered metal 16 can be omitted without fail. The generation amount of slag can be reliably reduced as a whole process.
In the present invention, the T.I. Since the Fe concentration is secured at 5 mass% or more, the melting point is low, and it is not necessary to add a modifier such as SiO ₂ or Al ₂ O ₃ to the slag. Therefore, an increase in the amount of slag due to the addition of the modifier can be suppressed.

Furthermore, in the steelmaking slag treatment method according to the present embodiment, the exhaust gas flow rate and CO concentration, CO ₂ concentration, and H ₂ concentration in the reforming and reducing treatment step S10 are analyzed, and reforming is performed by carbon, hydrogen and oxygen balance. T. of slag 15 Since the Fe concentration is calculated, the T.I. Before the Fe concentration becomes less than 5 mass%, the reforming reduction treatment step S10 can be surely terminated, and the recovered metal 16 having a low P concentration can be obtained.

As mentioned above, although the processing method of the steelmaking slag which is embodiment of this invention was demonstrated, this invention is not limited to this, In the range which does not deviate from the technical idea of the invention, it can change suitably.
For example, in the present embodiment, the reforming and reducing process is described as being performed in a converter, but the present invention is not limited to this, and the reforming and reducing process may be performed in another reaction vessel.

In the following, the results of experiments conducted to confirm the effects of the present invention will be described.
The blast furnace hot metal shown in Table 1 was charged into a 100 t converter (converter A), quick lime was added as a slagging agent to form slag on the hot metal, and oxygen was blown toward the hot metal to remove the slag. Phosphorus treatment was performed. The dephosphorization slag discharged after this dephosphorization process was 2.8 t (excluding the granular iron). The composition of the dephosphorized slag was as shown in Table 2.
Further, after dephosphorization slag was discharged, decarburization treatment was performed by adding quick lime as a slagging agent to form slag on the hot metal and blowing oxygen toward the hot metal. The decarburized slag discharged after this decarburization treatment was 3.7 t (excluding granular iron). The composition of the decarburized slag was shown in Table 3.

  Next, after adding 50t of hot metal to another converter (converter B), mixed slag mixed with the above dephosphorization slag and decarburized slag and anthracite are continuously supplied and reformed at 1450 ° C. Reduction treatment was performed. In one treatment, 50 t (including granular iron) of mixed slag was used. The composition of the mixed slag used at this time is shown in Table 4, and the composition of anthracite is shown in Table 5.

During this reforming and reduction treatment, the exhaust gas flow rate, the CO concentration, the CO ₂ concentration, and the H ₂ concentration are analyzed, and the T. The Fe concentration was calculated. After charging a predetermined amount of the mixed slag, the T.I. When the Fe concentration reached 5 mass%, the treatment was terminated, and the reformed slag was discharged with the recovered metal remaining. Here, the composition of the obtained modified slag is shown in Table 6, and the composition of the recovered metal is shown in Table 7.
This reforming and reduction treatment was repeatedly performed to process a total of 400 t (including the granular iron content, the slag content was 360 t) of mixed slag.

  As a result of this reforming and reducing treatment, 328 t of reformed slag was obtained, and the amount of generated slag of 32 t was reduced with respect to the mixed slag 360 t. In this modified slag, undehydrated lime (free CaO) was not included, steam aging was unnecessary, and a modified high strength without bubbles was obtained. It could also be used for high-grade applications such as upper roadbed materials and cement aggregates.

  Further, after repeatedly performing the reforming and reducing treatment, the amount of metal in the converter B was 151 t. Of these, 101 t was tapped and decarburized in converter A. As shown in Table 7, since the metal contained no Si and P was 0.009 mass%, the dephosphorization process could be omitted. Therefore, it is not necessary to use a slagging agent for dephosphorization treatment, and the amount of slag generated can be suppressed.

Specifically, the slag processed in the converter B (slag generated in the converter A) 400t (including the granular iron content, the slag content is 360t) is the total amount of slag processed 56 times in the converter A. Therefore, when the metal obtained in the converter B is used in the 57th process in the converter A, the slag generation amount is 56 times compared to the 57 slag generation normally. it can.
As described above, by the steel slag treatment method of the present invention, a total amount of slag generation of 38.5 t (32 t + 2.8 t + 3.7 t) could be reduced. This is a reduction of about 10%.

The blast furnace hot metal shown in Table 1 was charged into a 100 t converter (converter A), quick lime was added as a slagging agent to form slag on the hot metal, and oxygen was blown toward the hot metal to remove the slag. Phosphorus treatment was performed. The dephosphorization slag discharged after this dephosphorization process was 2.8 t (excluding the granular iron). The composition of the dephosphorized slag was as shown in Table 2.
Further, after dephosphorization slag was discharged, decarburization treatment was performed by adding quick lime as a slagging agent to form slag on the hot metal and blowing oxygen toward the hot metal. The decarburized slag discharged after this decarburization treatment was 3.7 t (excluding granular iron). The composition of the decarburized slag was shown in Table 3.

  Next, after adding 50t of hot metal to another converter (converter B), mixed slag mixed with the above dephosphorization slag and decarburized slag and anthracite are continuously supplied and reformed at 1450 ° C. Reduction treatment was performed. In one treatment, 50 t (including granular iron) of mixed slag was used. The composition of the mixed slag used at this time is shown in Table 4, and the composition of anthracite is shown in Table 5.

During this reforming and reduction treatment, the exhaust gas flow rate, the CO concentration, the CO ₂ concentration, and the H ₂ concentration are analyzed, and the T. The Fe concentration was calculated. After charging a predetermined amount of the mixed slag, the T.I. The treatment was terminated when the Fe concentration reached 9 mass%, and the reformed slag was discharged while the recovered metal remained. Here, the composition of the obtained modified slag is shown in Table 8, and the composition of the recovered metal is shown in Table 9.
This reforming and reduction treatment was repeatedly carried out to treat a total of 500 tons of mixed slag (including the granular iron content and 450 tons of slag).

  As a result of this reforming and reducing process, 430 t of reformed slag was obtained, and the amount of slag generated by 20 t was reduced with respect to 450 t of the mixed slag. In this modified slag, undehydrated lime (free CaO) was not included, steam aging was unnecessary, and a modified high strength without bubbles was obtained. It could also be used for high-grade applications such as upper roadbed materials and cement aggregates.

  Further, after repeatedly performing the reforming and reducing treatment, the amount of metal in the converter B was 151 t. Of these, 101 t was tapped and decarburized in converter A. As shown in Table 9, since the metal contained no Si and P was 0.008 mass%, the dephosphorization process could be omitted. Therefore, it is not necessary to use a slagging agent for dephosphorization treatment, and the amount of slag generated can be suppressed.

Specifically, the slag processed in the converter B (slag generated in the converter A) 500t (including the granular iron content, the slag content is 450t) is the total amount of slag processed 69 times in the converter A. Therefore, when the metal obtained in the converter B is used in the 70th processing in the converter A, the slag generation amount is 69 times compared to the 70 times of slag normally generated. it can.
As described above, the steelmaking slag treatment method of the present invention was able to reduce the total amount of slag generation of 26.5 t (20 t + 2.8 t + 3.7 t). This is a reduction of approximately 6%.

In one converter (converter A), normal operation was performed, and in another converter (converter B), the dephosphorization slag discharged from the converter A was subjected to reforming and reducing treatment. In addition, the reforming reduction treatment of decarburized slag was not performed. The composition of the dephosphorization slag used was shown in Table 2.
After 50 ton of molten iron was charged into the converter B, the above-described dephosphorization slag and anthracite having the composition shown in Table 5 were continuously supplied, and a reforming reduction treatment was performed at 1450 ° C. In one treatment, 50 t (including granular iron) of dephosphorization slag was used.

During this reforming and reduction treatment, the exhaust gas flow rate, the CO concentration, the CO ₂ concentration, and the H ₂ concentration are analyzed, and the T. The Fe concentration was calculated. After charging a predetermined amount of the mixed slag, the T.I. When the Fe concentration reached 5 mass%, the treatment was terminated, and the reformed slag was discharged with the recovered metal remaining. Here, the composition of the obtained modified slag is shown in Table 10, and the composition of the recovered metal is shown in Table 11.
This reforming and reduction treatment was repeatedly performed to treat a total of 400 t (including granular iron, slag was 360 t) of dephosphorized slag.

  As a result of this reforming and reducing treatment, 322 t of reformed slag was obtained. In this modified slag, undehydrated lime (free CaO) was not included, steam aging was unnecessary, and a modified high strength without bubbles was obtained. It could also be used for high-grade applications such as upper roadbed materials and cement aggregates.

  In addition, after repeatedly performing the reforming and reducing treatment, the amount of metal in the converter B was 162 t. Of these, 112 t was extracted and decarburized in converter A. As shown in Table 11, since the metal did not contain Si and P was 0.01 mass%, the dephosphorization process in the converter A could be omitted. Therefore, it is not necessary to use a slagging agent for dephosphorization treatment, and the amount of slag generated can be suppressed.

  Here, when the dephosphorization slag 360t (not including granular iron) of the converter A was processed, the decarburization slag of the converter A was 476 t (not including granular iron). As a result of this reforming and reducing process, 38t (360t-322t) has been reduced, so that approximately 5% of the total amount generated has been reduced.

  As described above, from the results of Example 1, Example 2 and Example 3, according to the steelmaking slag treatment method of the present invention, the amount of steelmaking slag generated can be reduced, and reforming that can be used in a wide range of applications. It was confirmed that slag can be obtained.

11 Dephosphorization slag 12 Decarburization slag 15 Reformed slag 16 Recovered metal S01 Dephosphorization process S02 Decarburization process S10 Reformation reduction process

Claims (5)

A method for treating steelmaking slag generated in a steelmaking process for removing impurities in hot metal,
The steelmaking slag is charged into a converter and heated, and by adding a reducing carbon material, a reforming reduction treatment step for obtaining a reforming slag and a recovered metal is provided.
T. in the modified slag. Before the Fe concentration becomes less than 5 mass%, by terminating the reforming reduction treatment step, the P concentration in the recovered metal is set to 0.01 mass% or less,
Therefore , the processing method of the steelmaking slag characterized by reducing the generation amount of the steel slag generated in the said steelmaking process . The steel making process has a dephosphorization process for removing silicon and phosphorus in the hot metal and a decarburization process for removing carbon from the hot metal,
The steelmaking slag according to claim 1, wherein one or both of the dephosphorization slag generated in the dephosphorization process and the decarburization slag generated in the decarburization process are processed as the steelmaking slag. Method.   In the reformed slag after completion of the reforming reduction treatment step, the T.I. The method for treating steelmaking slag according to claim 1 or 2, wherein the Fe concentration is in the range of 5 mass% to 10 mass%. The reforming reduction treatment step after completion the reforming basicity of slag (CaO _{mass%) /} the (SiO 2 mass%), one of claims 1 to 3, characterized in that a 1.7 The method for processing steelmaking slag according to claim 1.   The steel recovery slag according to any one of claims 1 to 4, wherein the recovered metal after completion of the reforming reduction treatment step is transferred into a reaction vessel in which the decarburization treatment step is performed. Processing method.

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