Method for recovering iron and valuable metals from steelmaking dust

Abstract

The present invention relates to a method for recovering iron and valuable metals from steelmaking dust. Specifically, according to one embodiment of the present invention, a method for recovering iron and valuable metals from steelmaking dust may be provided, the method including a steelmaking dust treatment process for treating steelmaking dust to produce an intermediate product containing iron, an intermediate product treatment process for heating the intermediate product charged into a melting furnace within a preset temperature range so that the intermediate product is melted and reduced, and a recovery process for recovering metallic iron produced by reduction from the intermediate product and housed in the melting furnace in a molten state, and recovering valuable metals produced in the form of dust in the intermediate product treatment process, the intermediate product treatment process including a reducing agent charging process for charging a reducing agent containing carbon into the melting furnace so that an amount of the metallic iron reduced from the intermediate product is increased, and the reducing agent is charged into the melting furnace at an equivalent ratio of 1.7 to 3.1 relative to the iron oxide contained in the intermediate product.

Description

[Technical field]

[0001] The present invention relates to a method for recovering iron and valuable metals from steelmaking dust. [Background technology]

[0002] Recently, the damage caused by air pollution due to dust has been increasing as the amount of dust generated is increasing. In particular, the amount of electric arc furnace dust (EAFD), which is highly polluted by heavy metals, generated in Japan has exceeded 360,000 tons per year and is continuously increasing. As a result, a method of burying steel dust is being used to treat steel dust.

[0003] However, simply burying steel dust pollutes the soil and groundwater, causing environmental pollution. Also, steel dust contains a large amount of valuable metals, but if the steel dust is buried, the valuable metals contained in the steel dust cannot be recycled and must be disposed of. Therefore, methods of treating steel dust that can recycle valuable metals while preventing pollution of the ecosystem and environment are being developed.

[0004] For example, steel dust can be used as a raw material in a process for producing crude zinc oxide. In the process for producing crude zinc oxide, steel dust is treated using a rotary hearth furnace (RHF) or a rotary kiln (RK). In this case, an intermediate product is produced together with the crude zinc oxide. Here, the intermediate product contains metallic iron and iron oxide, and impurities such as zinc, lead, and silver.

[0005] However, the intermediate product generated in the process of producing crude zinc oxide has an iron content of about 70%, and only 40% to 70% of the iron contained in the intermediate product is present in the form of metallic iron. In other words, 30% to 60% of the iron contained in the intermediate product is present in the form of iron oxide. As such, while the intermediate product has a low iron content, it has a high impurity content, making it difficult to use it as a raw material for ironmaking, steelmaking, etc., and most of it is landfilled as industrial waste. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in light of the above-mentioned background, and aims to improve the iron recovery rate and increase the iron content from intermediate products generated in the process of treating steelmaking dust.

[0007] Another object of the present invention is to improve the recovery rate of valuable metals, such as zinc, lead, and silver, generated in the process of treating steelmaking dust, and to recycle these valuable metals.

[0008] Another object of the present invention is to improve the recovery rate of iron and valuable metals, reduce the amount of iron and valuable metals that are landfilled, and reduce landfill costs.

[0009] Another object of the present invention is to reduce the amount of slag generated by increasing the amount of iron and valuable metals recovered, thereby minimizing the amount of slag to be treated and thereby reducing costs. [Means for solving the problem]

[0010] According to an embodiment of the present invention, there may be provided a method for recovering iron and valuable metals from steelmaking dust, the method including: a steelmaking dust treatment process for treating steelmaking dust to produce an intermediate product containing iron; an intermediate product treatment process for heating the intermediate product charged into a melting furnace within a preset temperature range so that the intermediate product is melted and reduced; and a recovery process for recovering metallic iron produced by reduction from the intermediate product and housed in the melting furnace in a molten state, and recovering valuable metals produced in the form of dust in the intermediate product treatment process, the intermediate product treatment process including a reducing agent charging process for charging a reducing agent containing carbon into the melting furnace so that an amount of the metallic iron reduced from the intermediate product is increased, and the reducing agent is charged into the melting furnace at an equivalent ratio of 1.7 to 3.1 relative to the iron oxide contained in the intermediate product.

[0011] According to one embodiment of the present invention, there can be provided a method for recovering iron and valuable metals from steelmaking dust, wherein the reducing agent has a diameter of 5 mm to 20 mm.

[0012] According to an embodiment of the present invention, the intermediate product treatment process includes a flux charging process of charging a flux into the melting furnace to adjust the basicity (CaO / SiO2) of slag generated in the intermediate product treatment process, and the flux is charged into the melting furnace so that the basicity of the slag is 0.4 to 1.5.

[0013] According to an embodiment of the present invention, there may be provided a method for recovering iron and valuable metals from steel dust, wherein the flux includes one or more of limestone, quartz sand, and dolomite.

[0014] According to an embodiment of the present invention, there may be provided a method for recovering iron and valuable metals from steelmaking dust, the recovering step including a metallic iron recovery step of discharging the metallic iron contained in the melting furnace in a molten state from the melting furnace, and recovering the discharged metallic iron in the form of an ingot through a casting process.

[0015] According to an embodiment of the present invention, there may be provided a method for recovering iron and valuable metals from steelmaking dust, wherein the recovery step includes a valuable metal recovery step of recovering the valuable metals through a bag filter step.

[0016] According to one embodiment of the present invention, there is provided a method for recovering iron and valuable metals from steelmaking dust, wherein the iron content of the metallic iron recovered in the recovery step is 90% or more and 97% or less.

[0017] According to one embodiment of the present invention, a method for recovering iron and valuable metals from steelmaking dust may be provided, wherein the melting furnace is one of a Submerged Arc Furnace (SAF), an Alternating Current Electronic Arc Furnace (ACEAF), and a Direct Current Electronic Arc Furnace (DC EAF).

[0018] According to an embodiment of the present invention, there may be provided a method for recovering iron and valuable metals from steelmaking dust, wherein the temperature range in the intermediate product treatment step is 1450° C. or more and 1650° C. or less.

[0019] According to one embodiment of the present invention, the steelmaking dust treatment process may provide a method for recovering iron and valuable metals from steelmaking dust, by treating the steelmaking dust to generate crude zinc oxide and the intermediate product. Effect of the Invention

[0020] According to the present invention, it is possible to improve the iron recovery rate from an intermediate product generated in a process for treating steelmaking dust, thereby increasing the iron content.

[0021] In addition, the recovery rate of valuable metals such as zinc, lead and silver generated in the process of treating steelmaking dust can be improved, and valuable metals can be recycled.

[0022] It is also possible to improve the recovery rate of iron and valuable metals, reduce the amount of iron and valuable metals that are landfilled, and reduce landfill costs.

[0023] In addition, by improving the recovery amount of iron and valuable metals, the amount of slag generated can be reduced, and the amount of slag to be treated can be minimized, resulting in cost savings. [Brief description of the drawings]

[0024] [Figure 1] 1 is a process diagram sequentially illustrating a method for recovering iron and valuable metals from steelmaking dust according to an embodiment of the present invention. FIG. [Diagram 2] FIG. 2 is a process diagram sequentially showing the intermediate product processing steps of FIG. 1. [Diagram 3] FIG. 2 is a process diagram sequentially showing the recovery process of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The embodiments of the present invention are illustrated for the purpose of explaining the technical idea of ​​the present invention, and the scope of the invention is not limited to the embodiments presented below or the specific explanations of these embodiments.

[0026] The present invention will now be described with reference to the drawings.

[0027] FIG. 1 is a flow chart sequentially illustrating a method for recovering iron and valuable metals from steelmaking dust according to one embodiment of the present invention.

[0028] 1, in a method (S1) for recovering iron and valuable metals from steelmaking dust, iron and valuable metals can be recovered from steelmaking dust. The method (S1) for recovering iron and valuable metals from steelmaking dust can include a steelmaking dust processing step (S100), an intermediate product processing step (S200), and a recovery step (S300).

[0029] In the steel dust treatment process (S100), crude zinc oxide and intermediate products may be produced by treating steel dust. In this specification, steel dust (EAF Dust, Electric Arc Furnace Dust) refers to fine powder that is collected through a cooling process of scattered dust or gas generated during the melting process of an electric furnace using iron scrap as a main raw material. For example, steel dust may contain iron oxide, valuable metals such as lead, zinc, silver, etc., and harmful heavy metals such as cadmium, mercury, chromium, etc. Meanwhile, in the steel dust treatment process (S100), steel dust may be heated using a rotary hearth reduction furnace (RHF) or a rotary kiln (RK). In this case, the steel dust may undergo a reduction reaction, and zinc may be produced by reducing zinc oxide contained in the steel dust. For example, zinc may be produced in a gaseous state, and the zinc produced in the gaseous state may be recovered as crude zinc oxide through a reoxidation and cooling process. Additionally, intermediate products may be produced by reducing steelmaking dust.

[0030] In this specification, the intermediate product includes iron, and may include iron oxide and metallic iron. For example, the intermediate product may include metallic iron produced by reducing iron oxide contained in steelmaking dust, and iron oxide that remains without being completely reduced. The intermediate product may also include valuable metals such as zinc, lead, and silver.

[0031] Meanwhile, the reactions in which steelmaking dust is reduced to iron oxide and metallic iron in the steelmaking dust treatment process (S100) are as shown in the following reaction formulas 1 to 5.

[0032] C(s) + O2(g) = CO2(g)…(Reaction 1)

[0033] C(s) + CO2(g) = 2CO(g)…(Reaction 2)

[0034] 3Fe2O3(s) + CO(g) = 2Fe3O4(s) + CO2(g)…(Reaction 3)

[0035] Fe3O4(s) + CO(g) = 3FeO(s) + CO2(g)…(Reaction 4)

[0036] FeO(s) + CO(g) = Fe(s) + CO2(g)…(Reaction 5)

[0037] In addition, in the steel dust treatment process (S100), the intermediate product is described as being produced together with crude zinc oxide, but this is merely an example and does not limit the present invention. Therefore, the intermediate product may be produced in a separate process that does not produce crude zinc oxide.

[0038] The steelmaking dust treatment process (S100) may include a steelmaking dust roasting process.

[0039] Referring to FIG. 2, in the intermediate product treatment process (S200), the melting furnace may be heated to a preset temperature range. In this case, the intermediate product charged in the melting furnace is melted, and iron oxide contained in the intermediate product charged in the melting furnace is reduced to metallic iron. In this case, reduction and melting of the intermediate product may be performed simultaneously. Also, valuable metals may be generated in the form of dust in the intermediate product treatment process (S200). Such intermediate product treatment process (S200) may include an intermediate product charging process (S210), a reducing agent charging process (S220), a flux charging process (S230), and a heating process (S240).

[0040] In the intermediate product charging step (S210), the intermediate product generated in the steel dust processing step (S100) is charged into the melting furnace. For example, the intermediate product generated in the steel dust processing step (S100) may be charged into the melting furnace immediately in a high temperature state. The intermediate product charged into the melting furnace in the intermediate product charging step (S210) may have a diameter of 10 mm to 20 mm. If the diameter of the intermediate product is less than 10 mm, the intermediate product is lost due to dust collection during the process of transporting and charging the intermediate product. That is, the intermediate product is mixed with dust, and the quality of valuable metals obtained from the dust decreases. In addition, if the diameter of the intermediate product is more than 20 mm, a raw material clogging phenomenon occurs due to the intermediate product during the process of transporting and charging the intermediate product, and there is a problem that the intermediate product cannot be smoothly charged into the melting furnace. In addition, the melting furnace may be a SAF (Submerged Arc Furnace) electric furnace. However, this is merely an example, and the melting furnace may be one of an AC EAF (Alternating Current Electronic Arc Furnace) electric furnace and a DC EAF (Direct Current Electronic Arc Furnace) electric furnace. Also, in this specification, the melting furnace is described as an electric furnace, but this is merely an example, and the melting furnace may use a heating means such as an induction furnace.

[0041] In the reducing agent charging step (S220), a reducing agent is charged into the melting furnace so as to increase the amount of metallic iron reduced from the intermediate product. The reducing agent may include carbon, and may include one or more of coal and coke. The reducing agent is charged into the melting furnace at an equivalent ratio of 1.7 to 3.1 relative to the iron oxide contained in the intermediate product. Here, the equivalent is a value obtained by dividing the mass of the substance by the molar mass, and the equivalent ratio of the reducing agent to the iron oxide means a ratio of the reducing agent equivalent obtained by dividing the mass of the reducing agent by the molar mass of the reducing agent and the iron equivalent obtained by dividing the mass of the iron oxide by the molar mass of iron. For example, if the reducing agent is charged into the melting furnace at an equivalent ratio of less than 1.7 relative to the iron oxide contained in the intermediate product, the amount of the reducing agent reduced to metallic iron decreases, and the recovery rate of metallic iron decreases. In addition, if the reducing agent is charged into the melting furnace at an equivalent ratio exceeding 3.1 with respect to the iron oxide contained in the intermediate product, impurities other than the intermediate product are reduced, the metallic iron content decreases, the fluidity of the slag deteriorates, and the processing cost increases. Such a reducing agent may be charged into the melting furnace as it is mixed with the iron oxide. In addition, the reducing agent charged into the melting furnace in the reducing agent charging step (S220) may have a diameter of 5 mm to 20 mm. If the diameter of the reducing agent is less than 5 mm, the reducing agent is lost due to dust collection, and if the diameter of the reducing agent is more than 20 mm, the reaction area is small and the reaction does not proceed smoothly.

[0042] In the flux charging step (S230), a flux is charged into the melting furnace to increase the amount of metallic iron reduced from the intermediate product and improve the fluidity of the slag. Here, the flux is used to adjust the basicity (CaO / SiO2) of the slag generated when the intermediate product is melted and reduced, and may be charged into the melting furnace so that the basicity of the slag is 0.4 to 1.5. For example, if the basicity of the slag is less than 0.4, the viscosity of the slag becomes too high, making it difficult to tap the subsequent molten metallic iron. Also, if the basicity of the slag exceeds 1.5, the efficiency of reducing metallic iron decreases and the amount of slag generated increases.

[0043] Also, the flux may include one or more of limestone, quartz sand, and dolomite. For example, when an intermediate product having a low ratio of calcium oxide (CaO) is charged into the melting furnace in the intermediate product charging step (S210), limestone may be charged into the melting furnace in the flux charging step (S230). As another example, when an intermediate product having a high ratio of calcium oxide is charged into the melting furnace in the intermediate product charging step (S210), quartz sand may be charged into the melting furnace in the flux charging step (S230). The flux charged into the melting furnace in the flux charging step (S230) may have a diameter of 5 mm to 20 mm. When the diameter of the flux is less than 5 mm, flux loss occurs due to dust collection during the process of transporting and charging the flux. That is, the flux is mixed with dust, and the grade of valuable metals obtained from the dust decreases. In addition, if the diameter of the flux exceeds 20 mm, a raw material clogging phenomenon occurs due to intermediate products during the process of transporting and charging the flux, making it difficult to smoothly charge the flux into the melting furnace.

[0044] Meanwhile, the intermediate product charging step (S210), the reducing agent charging step (S220), and the flux charging step (S230) may be performed simultaneously or sequentially. For example, when the intermediate product charging step (S210), the reducing agent charging step (S220), and the flux charging step (S230) are performed simultaneously, the intermediate product, the reducing agent, and the flux are charged into the melting furnace in a mixed state. Also, the intermediate product, the reducing agent, and the flux may be continuously charged into the melting furnace for a predetermined time. As an example, the intermediate product, the reducing agent, and the flux are continuously charged into a 500 KVA SAF melting furnace for 3 to 4 hours based on 1 ton. If 1 ton of the intermediate product, the reducing agent, and the flux are charged in less than 3 hours, the intermediate product, the reducing agent, and the flux will accumulate on the slag without being melted, and more heat energy will be supplied to melt them, resulting in heat loss. In addition, if 1 ton of the intermediate product, the reducing agent, and the flux is charged for more than 4 hours, the recovery efficiency of iron and valuable metals will be low. In this specification, the description is based on charging 1 ton of the intermediate product, the reducing agent, and the flux into a 500 KVA SAF melting furnace, but this is merely an example and does not limit the present invention.

[0045] Meanwhile, when the intermediate product charging step (S210), the reducing agent charging step (S220), and the flux charging step (S230) are performed, the intermediate product, the reducing agent, and the flux may be charged into the melting furnace in a state where molten metal and slag are formed inside the melting furnace. That is, after a certain amount of metallic iron is initially melted to form slag and molten metal, the intermediate product charging step (S210), the reducing agent charging step (S220), and the flux charging step (S230) are additionally performed. In this case, even if the charged intermediate product is reduced and gas is generated, the generated gas is easily released to the outside because the raw material layer does not cover the slag and metal layers. In other words, there is an effect of preventing the foaming phenomenon of the molten metal and slag caused by the generated gas. In addition, since the raw material layer does not cover the slag and metal layers, zinc is prevented from remaining as zinc oxide in the raw material layer. In this case, there is an effect that valuable metals such as zinc and lead can be easily recovered since the dust is easily discharged to the outside.

[0046] In the heating step (S240), the intermediate product charged in the melting furnace is heated to a preset temperature range so that the intermediate product is melted and reduced. For example, in the heating step (S240), the inside of the melting furnace can be heated by supplying power to the electric furnace. In other words, the electric furnace is supplied with power to heat the intermediate product charged therein, and for example, power of 1,400 kWh to 1,700 kWh per ton of intermediate product can be supplied. In this case, the temperature inside the electric furnace can be adjusted to 1,450°C to 1,650°C, and the intermediate product can be melted and reduced in this temperature range. If the temperature inside the electric furnace is lower than 1,450°C, the intermediate product cannot be melted and reduced smoothly, and if the temperature inside the electric furnace is higher than 1,650°C, manganese or silicon can be reduced and flow in as impurities, which can reduce the quality of the produced metallic iron.

[0047] Meanwhile, the reactions in which iron oxide is reduced to metallic iron by a reducing agent in the heating step (S240) are shown in the following reaction formulas 6 to 8.

[0048] FeO(s) + C(s) = Fe + CO(g)…(Reaction 6)

[0049] FeO(s) + CO(g) = Fe(s) + CO2(g)…(Reaction 7)

[0050] CO2(g) + C(s) = 2CO(g)…(Reaction 8)

[0051] The intermediate product processing step (S200) may include an intermediate product smelting step.

[0052] 3, in the recovery step (S300), metallic iron and valuable metals contained in the melting furnace are recovered. The content of metallic iron recovered in this recovery step (S300) may be 90% or more and 97% or less. This recovery step (S300) may include a metallic iron recovery step (S310), a valuable metal recovery step (S320), and a slag recovery step (S330).

[0053] In the metallic iron recovery step (S310), the metallic iron that is reduced from the intermediate product in the intermediate product treatment step (S200) and placed in the melting furnace in a molten state is recovered. For example, the metallic iron placed in the melting furnace in a molten state is located at the bottom of the melting furnace due to phase separation caused by the difference in specific gravity with the slag. In this case, the metallic iron in a molten state can be discharged through a discharge passage at the bottom of the melting furnace. In addition, the metallic iron discharged from the melting furnace can be recovered in the form of an ingot, which is a rectangular hexahedron having a size of 50 cm x 20 cm x 5 cm, through a casting process. The carbon content of the metallic iron discharged from the melting furnace can be 0.5% to 2.5%, and the metallic iron can be pig iron. In addition, the iron content of the metallic iron recovered in the metallic iron recovery step (S310) can be 90% or more and 97% or less.

[0054] In the valuable metal recovery step (S320), valuable metals generated in the form of dust in the intermediate product treatment step (S200) are recovered. For example, in the valuable metal recovery step (S320), valuable metals may be recovered through a bag filter process. In addition, valuable metals may include one or more of zinc (Zn), lead (Pb), and silver (Ag).

[0055] In the slag recovery step (S330), the slag contained in the melting furnace is recovered. For example, in the melting furnace, the slag is located on top of the metallic iron due to phase separation caused by the difference in specific gravity between the slag and the metallic iron, and when the metallic iron is discharged through the metallic iron recovery step (S310), it can be discharged from the melting furnace through a discharge passage. A portion of the slag recovered in the slag recovery step (S330) can be recycled as a cement raw material, etc.

[0056] The contents and recovery rates of metallic iron and valuable metals produced according to the embodiment of the present invention will be described below. In this embodiment, four different intermediate products were charged into a melting furnace, and the contents (wt%) of each component of the charged intermediate products are shown in Table 1 below. [Table 1]

[0057] [Example 1] In Example 1, 1 ton of intermediate product A was charged into a melting furnace, and then coal was used as a reducing agent and was mixed in such that the iron oxide ratio contained in intermediate product A was 2.5 equivalent ratio. In this case, the basicity of the slag was 0.6. The contents (wt%) and recovery rates (%) of metallic iron, slag, and dust produced in Example 1 are shown in Table 2 below. [Table 2]

[0058] In Example 1, the recovery rate of iron recovered as metallic iron was 98.00%, and the recovery rates of zinc and lead recovered as dust were 98.65% and 99.49%, respectively.

[0059] [Example 2] In Example 2, 1 ton of intermediate product A was charged into a melting furnace, and then coal was used as a reducing agent, and the coal was mixed so that the iron oxide ratio contained in intermediate product A was 2.5 equivalent ratio. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The contents (weight %) and recovery rates (%) of metallic iron, slag, and dust produced in Example 2 are shown in Table 3 below. [Table 3]

[0060] In Example 2, the recovery rate of iron recovered as metallic iron was 98.18%, and the recovery rates of zinc and lead recovered as dust were 98.96% and 99.04%, respectively.

[0061] [Example 3] In Example 3, 1 ton of intermediate product B was charged into the melting furnace, and then coal was used as a reducing agent, and the coal was mixed so that the iron oxide ratio contained in intermediate product B was 2.5 equivalent ratio. In addition, 111 kg of quartz sand was charged into the melting furnace so that the basicity of the slag was 0.6. The contents (weight %) and recovery rates (%) of metallic iron, slag, and dust produced in Example 3 are shown in Table 4 below. [Table 4]

[0062] In Example 3, the recovery rate of iron recovered as metallic iron was 98.23%, and the recovery rates of zinc and lead recovered as dust were 97.86% and 97.12%, respectively.

[0063] [Example 4] In Example 4, 1 ton of intermediate product C was charged into the melting furnace, and then coal was used as a reducing agent, and the coal was mixed so that the iron oxide ratio contained in intermediate product C was 2.5 equivalent ratio. In addition, 92 kg of quartz sand was charged into the melting furnace so that the basicity of the slag was 0.6. The contents (weight %) and recovery rates (%) of metallic iron, slag, and dust produced in Example 4 are shown in Table 5 below. [Table 5]

[0064] In Example 4, the recovery rate of iron recovered as metallic iron was 98.21%, and the recovery rates of zinc and lead recovered as dust were 99.33% and 98.56%, respectively.

[0065] [Example 5] In Example 5, 1 ton of intermediate product D was charged into a melting furnace, and then coal was used as a reducing agent, and the coal was mixed so that the iron oxide ratio contained in intermediate product D was 2.5 equivalent ratio. In addition, 150 kg of quartz sand was charged into the melting furnace so that the basicity of the slag became 0.6. The contents (wt%) and recovery rates (%) of metallic iron, slag, and dust produced in Example 5 are shown in Table 6 below. [Table 6]

[0066] In Example 5, the recovery rate of iron recovered as metallic iron was 98.41%, and the recovery rates of zinc and lead recovered as dust were 98.21% and 99.70%, respectively. Intermediate products B, C and D used in Examples 3 to 5 each had a higher iron content than intermediate product A used in Examples 1 and 2, and the metallic iron content produced in Examples 3 to 5 was higher than the metallic iron content produced in Examples 1 and 2. Furthermore, in all of Examples 1 to 5, the recovery rate of iron recovered as metallic iron was 98% or more, and the recovery rates of zinc and lead recovered as dust were 97% or more.

[0067] As described above, according to each embodiment of the present invention, it is possible to produce metallic iron having a content of 90% or more, and thus improve the recovery rate of metallic iron. In addition, it is possible to improve the recovery rate of valuable metals such as zinc and lead, and thus recycle them. In this case, it is possible to significantly reduce the amount of iron and valuable metals that are buried in landfill sites, and thus reduce the cost required for landfilling. In addition, by improving the recovery amount of iron and valuable metals, it is possible to reduce the amount of slag generated, and thus minimize the amount of slag to be treated, and thus reduce costs.

[0068] [Example 6] In Example 6, 1 ton of intermediate product A was charged into a melting furnace, and then coal was used as a reducing agent, and the coal was mixed so that the iron oxide ratio contained in intermediate product A was 2.1 equivalent ratio. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The contents (weight %) and recovery rates (%) of metallic iron, slag, and dust produced in Example 6 are shown in Table 7 below. [Table 7]

[0069] In Example 6, the recovery rate of iron recovered as metallic iron was 96.73%, and the recovery rates of zinc and lead recovered as dust were 99.67% and 99.27%, respectively.

[0070] [Example 7] In Example 7, 1 ton of intermediate product A was charged into a melting furnace, and then coal was used as a reducing agent, and the coal was mixed so that the iron oxide ratio contained in intermediate product A was 1.7 equivalent ratio. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The contents (weight %) and recovery rates (%) of metallic iron, slag, and dust produced in Example 7 are shown in Table 8 below. [Table 8]

[0071] In Example 7, the recovery rate of iron recovered as metallic iron was 96.01%, and the recovery rates of zinc and lead recovered as dust were 98.67% and 99.49%, respectively.

[0072] [Example 8] In Example 8, 1 ton of intermediate product A was charged into a melting furnace, and then coal was used as a reducing agent, and the coal was mixed so that the iron oxide ratio contained in intermediate product A was 3.1 equivalent ratio. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The contents (weight %) and recovery rates (%) of metallic iron, slag, and dust produced in Example 8 are shown in Table 9 below. [Table 9]

[0073] In Example 8, the recovery rate of iron recovered as metallic iron was 95.64%, and the recovery rates of zinc and lead recovered as dust were 98.46% and 99.20%, respectively.

[0074] [Comparative Example 1] In Comparative Example 1, 1 ton of intermediate product A was charged into a melting furnace, and then coal was used as a reducing agent and was blended so that the iron oxide ratio contained in intermediate product A was 1.3 equivalent ratio. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The contents (weight %) and recovery rates (%) of metallic iron, slag, and dust generated in Comparative Example 1 are shown in Table 10 below. [Table 10]

[0075] In Comparative Example 1, the recovery rate of iron recovered as metallic iron was 85.48%, and the recovery rates of zinc and lead recovered as dust were 98.33% and 97.11%, respectively.

[0076] [Comparative Example 2] In Comparative Example 2, 1 ton of intermediate product A was charged into a melting furnace, and then coal was used as a reducing agent and was blended so that the iron oxide ratio contained in intermediate product A was 4.6 equivalent ratio. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The contents (weight %) and recovery rates (%) of metallic iron, slag, and dust generated in Comparative Example 2 are shown in Table 11 below. [Table 11]

[0077] In Comparative Example 2, the recovery rate of iron recovered as metallic iron is 89.68%, and the recovery rates of zinc and lead recovered as dust are 98.39% and 99.23%, respectively. Comparing Comparative Examples 1 and 2 with Examples 6 to 8, it can be seen that when the reducing agent is charged into the melting furnace so that the iron oxide ratio contained in the intermediate product deviates from the equivalent ratio of 1.7 to 3.1, the recovery rate of metallic iron drops sharply. In other words, when the reducing agent is charged into the melting furnace at the equivalent ratio of 1.7 to 3.1 to the iron oxide ratio contained in the intermediate product, there is an effect of improving the recovery rate of iron. In addition, there is an effect of preventing an increase in costs due to excessive charging of the reducing agent.

[0078] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, it should be understood by those skilled in the art that the present invention may be embodied in other specific forms without changing the technical concept or essential characteristics of the present invention.

[0079] Therefore, it should be understood that the above-described embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims rather than the detailed description above, and all modifications and alterations derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. a steel dust processing step of processing steel dust to generate an intermediate product containing iron; an intermediate product treatment step of heating the intermediate product charged in a melting furnace within a preset temperature range so that the intermediate product is melted and reduced; and a recovery step of recovering metallic iron produced by reduction from the intermediate product and contained in the melting furnace in a molten state, and recovering valuable metals produced in the form of dust in the intermediate product treatment step, the intermediate product processing step includes a reducing agent charging step of charging a reducing agent containing carbon into the melting furnace so as to increase the amount of the metallic iron reduced from the intermediate product, The reducing agent is charged into the melting furnace in an equivalent ratio of 1.7 to 3.1 relative to the iron oxide contained in the intermediate product.

2. The method for recovering iron and valuable metals from steelmaking dust according to claim 1, wherein the reducing agent has a diameter of 5 mm to 20 mm.

3. The intermediate product treatment step is performed by adjusting the basicity (CaO / SiO ２ A flux charging step of charging a flux into the melting furnace to adjust the melting temperature; 2. The method for recovering iron and valuable metals from steelmaking dust according to claim 1, wherein the flux is charged into the melting furnace so that the basicity of the slag is 0.4 to 1.

5.

4. 4. The method for recovering iron and valuable metals from steel dust according to claim 3, wherein the flux comprises one or more of limestone, quartz sand and dolomite.

5. 2. The method for recovering iron and valuable metals from steelmaking dust as set forth in claim 1, wherein the recovery process includes a metallic iron recovery process of discharging the metallic iron contained in the melting furnace in a molten state from the melting furnace and recovering the discharged metallic iron in the form of an ingot through a casting process.

6. The method for recovering iron and valuable metals from steelmaking dust according to claim 1, wherein the recovery step includes a valuable metal recovery step of recovering the valuable metals through a bag filter step.

7. 2. The method for recovering iron and valuable metals from steelmaking dust according to claim 1, wherein the iron content of the metallic iron recovered in the recovery step is 90% or more and 97% or less.

8. 2. The method for recovering iron and valuable metals from steelmaking dust according to claim 1, wherein the temperature range in the intermediate product treatment step is 1450°C or more and 1650°C or less.

9. 2. The method for recovering iron and valuable metals from steelmaking dust according to claim 1, wherein the melting furnace is one of a Submerged Arc Furnace (SAF) electric furnace, an Alternating Current Electronic Arc Furnace (ACEAF) electric furnace, and a Direct Current Electronic Arc Furnace (DCEAF) electric furnace.

10. The method for recovering iron and valuable metals from steelmaking dust according to claim 1 , wherein the steelmaking dust treatment step treats the steelmaking dust to produce crude zinc oxide and the intermediate product.

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