Method for recovering iron and valuable metals from steelmaking dust

Abstract

This invention provides a method for recovering iron and valuable metals from steelmaking dust, which can improve the iron recovery rate from intermediate products generated in the process of treating steelmaking dust and increase the iron content. [Solution] The method for recovering iron and valuable metals from steelmaking dust according to the present invention includes: a steelmaking dust treatment step of treating steelmaking dust to produce an intermediate product containing iron; an intermediate product treatment step of heating the intermediate product, which has been charged into a melting furnace, to a temperature range that has already been set so that it is melted and reduced; and a recovery step of recovering metallic iron that has been reduced from the intermediate product and is contained in the melting furnace while still molten, and recovering valuable metals that have been generated in dust form in the intermediate product treatment step, wherein the intermediate product treatment 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 metallic iron reduced from the intermediate product, and 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.

Description

Technical Field

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

Background Art

[0002] Recently, with the increasing generation amount of dust, which is one of the wastes, the damage caused by air pollution due to dust has increased rapidly. In particular, the domestic generation amount of electric arc furnace dust (EAFD), which has a high pollution degree of heavy metals among dusts, exceeds 360,000 tons per year and is continuously increasing. Accordingly, a method of embedding steelmaking dust to treat steelmaking dust is being utilized.

[0003] However, the method of simply embedding steelmaking dust pollutes soil and groundwater and causes environmental pollution. In addition, although steelmaking dust contains a large amount of valuable metals, when steelmaking dust is embedded, the valuable metals contained in the steelmaking dust cannot be recycled and must be discarded. Therefore, a method for treating steelmaking dust that can recycle valuable metals while preventing the ecosystem and environment from being polluted has been developed.

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

[0005] However, the intermediate products generated in the process of producing crude zinc oxide have an iron content of approximately 70%, and only 40% to 70% of the iron in these intermediate products exists in the form of metallic iron. In other words, 30% to 60% of the iron in these intermediate products exists in the form of iron oxide. Thus, while the intermediate products have a low iron content, they have a high impurity content, making them difficult to use as raw materials for ironmaking and steelmaking, and the majority of them end up being landfilled as industrial waste. [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention was conceived in view of the aforementioned background, and aims to improve the iron recovery rate from intermediate products generated in the process of treating steelmaking dust, thereby increasing the iron content.

[0007] Furthermore, the aim 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] Furthermore, the aim is to improve the recovery rate of iron and valuable metals, reduce the amount of iron and valuable metals sent to landfills, and decrease landfill costs.

[0009] Furthermore, the aim is to reduce the amount of slag generated and minimize the amount of slag that needs to be processed by improving the recovery rate of iron and valuable metals, thereby saving costs. [Means for solving the problem]

[0010] According to one embodiment of the present invention, a method for recovering iron and valuable metals from steelmaking dust is provided, comprising: a steelmaking dust treatment step of treating steelmaking dust to produce an intermediate product containing iron; an intermediate product treatment step of heating the intermediate product, which has been charged into a melting furnace, to a pre-set temperature range so that it 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 while still molten, and recovering valuable metals produced in dust form in the intermediate product treatment step, wherein the intermediate product treatment 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 metallic iron reduced from the intermediate product, and 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.

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

[0012] According to one embodiment of the present invention, a method for recovering iron and valuable metals from steelmaking dust is provided, wherein the intermediate product treatment step includes a flux charging step of charging a flux into the melting furnace to adjust the basicity (CaO / SiO2) of the slag produced in the intermediate product treatment step, the flux being charged into the melting furnace such that the basicity of the slag is 0.4 to 1.5.

[0013] According to one embodiment of the present invention, a method for recovering iron and valuable metals from steelmaking dust is provided, wherein the flux comprises one or more of limestone, quartz sand, and dolomite.

[0014] According to one embodiment of the present invention, a method for recovering iron and valuable metals from steelmaking dust is provided, wherein the recovery step includes a metal iron recovery step in which the molten metal iron contained in the melting furnace is discharged from the melting furnace, and the discharged metal iron is recovered in the form of an ingot through a casting step.

[0015] According to one embodiment of the present invention, a method for recovering iron and valuable metals from steelmaking dust is provided, wherein the recovery step includes a valuable metal recovery step in which the valuable metals are recovered through a bag filter step.

[0016] According to one embodiment of the present invention, a method for recovering iron and valuable metals from steelmaking dust is provided, 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 is provided, wherein the melting furnace is one of a SAF (Submerged Arc Furnace) electric furnace, an ACEAF (Alternating Current Electronic Arc Furnace) electric furnace, and a DCEAF (Direct Current Electronic Arc Furnace) electric furnace.

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

[0019] According to one embodiment of the present invention, the steelmaking dust treatment step provides a method for recovering iron and valuable metals from steelmaking dust, wherein the steelmaking dust is treated to produce crude zinc oxide and the intermediate product. [Effects of the Invention]

[0020] According to the present invention, it is possible to improve the iron recovery rate from intermediate products generated in the process of treating steelmaking dust, and to increase the iron content.

[0021] Furthermore, it improves the recovery rate of valuable metals such as zinc, lead, and silver generated in the process of treating steelmaking dust, thus enabling the recycling of valuable metals.

[0022] In addition, it is possible to improve the recovery rates of iron and valuable metals, reduce the amount of iron and valuable metals to be landfilled, and decrease the landfill cost.

[0023] In addition, by improving the recovery amount of iron and valuable metals, it is possible to reduce the amount of slag generated, minimize the amount of slag to be processed, and achieve the effect of cost reduction.

Brief Description of the Drawings

[0024] [Figure 1] It is a process diagram sequentially showing a method for recovering iron and valuable metals from steelmaking dust according to an embodiment of the present invention. [Figure 2] It is a process diagram sequentially showing the intermediate product treatment process of FIG. 1. [Figure 3] It is a process diagram sequentially showing the recovery process of FIG. 1.

Modes for Carrying Out the Invention

[0025] Each embodiment of the present invention is illustrated for the purpose of explaining the technical idea of the present invention. The scope of rights according to the present invention is not limited to each of the embodiments presented below or the specific descriptions regarding these embodiments.

[0026] Hereinafter, the present invention will be described with reference to the drawings.

[0027] FIG. 1 is a process diagram sequentially showing a method for recovering iron and valuable metals from steelmaking dust according to an embodiment of the present invention.

[0028] Referring to FIG. 1, in the method (S1) for recovering iron and valuable metals from steelmaking dust, iron and valuable metals can be recovered from the steelmaking dust. Such a method (S1) for recovering iron and valuable metals from steelmaking dust may include a steelmaking dust treatment process (S100), an intermediate product treatment process (S200), and a recovery process (S300).

[0029] In the steelmaking dust treatment process (S100), steelmaking dust can be treated to produce crude zinc oxide and intermediate products. In this specification, steelmaking dust (EAFDust, Electric Arc Furnace Dust) refers to fine particulate powder collected after a cooling process from scattered dust or gas generated during the melting process of an electric furnace using iron scrap as the main raw material. For example, steelmaking dust may contain iron oxide, valuable metals such as lead, zinc, and silver, and harmful heavy metals such as cadmium, mercury, and chromium. On the other hand, in the steelmaking dust treatment process (S100), steelmaking dust can be heated using a rotary hearth furnace (RHF) or a rotary kiln (RK). In this case, the steelmaking dust can undergo a reduction reaction, and zinc can be produced by the reduction of zinc oxide contained in the steelmaking dust. For example, zinc can be produced in a gaseous state, and the zinc produced in a gaseous state can be recovered as crude zinc oxide through a re-oxidation and cooling process. Furthermore, intermediate products may be generated when steelmaking dust is reduced.

[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 the reduction of iron oxide contained in steelmaking dust, and iron oxide that remains unreduced. The intermediate product may also include valuable metals such as zinc, lead, and silver.

[0031] On the other hand, the reaction in which steelmaking dust is reduced to iron oxide and metallic iron in the steelmaking dust treatment process (S100) is as shown in the following reaction equations 1 to 5.

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

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

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

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

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

[0037] Furthermore, although it is stated that the intermediate product is produced together with crude zinc oxide in the steelmaking dust treatment process (S100), this is merely an example and does not limit the present invention. Therefore, the intermediate product can also 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 Figure 2, in the intermediate product processing step (S200), the melting furnace can be heated to a pre-set temperature range. In this case, the intermediate product charged into the melting furnace melts, and the iron oxide contained in the intermediate product charged into the melting furnace is reduced to metallic iron. In this case, the reduction and melting of the intermediate product can occur simultaneously. In addition, valuable metals can be generated in dust form in the intermediate product processing step (S200). Such an intermediate product processing step (S200) may include an intermediate product charging step (S210), a reducing agent charging step (S220), a flux charging step (S230), and a heating step (S240).

[0040] In the intermediate product charging process (S210), the intermediate products generated in the steelmaking dust treatment process (S100) are charged into the melting furnace. For example, the intermediate products generated in the steelmaking dust treatment process (S100) can be immediately charged into the melting furnace at a high temperature. The intermediate products charged into the melting furnace in the intermediate product charging process (S210) may have a diameter of 10 mm to 20 mm. If the diameter of the intermediate products is less than 10 mm, loss of intermediate products due to dust collection occurs during the transport and charging process. That is, the intermediate products are mixed with dust, and the quality of the valuable metals obtained from the dust decreases. Also, if the diameter of the intermediate products is greater than 20 mm, a clogging phenomenon by the intermediate products occurs during the transport and charging process, which prevents the intermediate products from being smoothly charged into the melting furnace. Furthermore, the melting furnace may be an SAF (Submerged Arc Furnace) electric furnace. However, this is merely an example, and the melting furnace may be either an ACEAF (Alternating Current Electronic Arc Furnace) electric furnace or a DCEAF (Direct Current Electronic Arc Furnace) electric furnace. Also, although the melting furnace is described as an electric furnace in this specification, this is merely an example, and heating means such as an induction furnace may be used for the melting furnace.

[0041] In the reducing agent charging process (S220), a reducing agent is charged into the melting furnace in such a way that the amount of metallic iron reduced from the intermediate product increases. The reducing agent may contain carbon and may contain 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, equivalent is the value obtained by dividing the mass of the substance by its molar mass, and the equivalent ratio of the reducing agent to iron oxide means the ratio of the reducing agent equivalent (mass of the reducing agent divided by its molar mass) to the iron equivalent (mass of iron oxide divided by its molar mass). 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 reduced to metallic iron decreases, and the recovery rate of metallic iron decreases. Furthermore, if the reducing agent is charged into the melting furnace at a ratio of iron oxide to the intermediate product that exceeds 3.1 equivalents, impurities other than the intermediate product will be reduced, lowering the metallic iron content, worsening the fluidity of the slag, and increasing processing costs. Such reducing agents may be charged into the melting furnace while still mixed with iron oxide. In addition, the reducing agent charged into the melting furnace in the reducing agent charging process (S220) may have a diameter of 5 mm to 20 mm. If the diameter of the reducing agent is less than 5 mm, loss of the reducing agent due to dust collection will occur, and if the diameter of the reducing agent is greater than 20 mm, the reaction area will be small and the reaction will not proceed smoothly.

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

[0043] Furthermore, the flux may contain one or more of the following: limestone, quartz sand, and dolomite. For example, if an intermediate product with a low proportion of calcium oxide (CaO) is charged into the melting furnace in the intermediate product charging process (S210), limestone may be charged into the melting furnace in the flux charging process (S230). As another example, if an intermediate product with a high proportion of calcium oxide is charged into the melting furnace in the intermediate product charging process (S210), quartz sand may be charged into the melting furnace in the flux charging process (S230). The flux charged into the melting furnace in the flux charging process (S230) may have a diameter of 5 mm to 20 mm. If the diameter of the flux is less than 5 mm, loss of flux due to dust collection occurs during the transport and charging process. That is, the flux is mixed with dust, and the quality of the valuable metals obtained from the dust decreases. Furthermore, if the flux diameter exceeds 20 mm, a clogging phenomenon occurs due to intermediate products during the transport and charging process of the flux, making it difficult to smoothly charge the flux into the melting furnace.

[0044] On the other hand, the intermediate product charging process (S210), the reducing agent charging process (S220), and the flux charging process (S230) can be performed simultaneously or sequentially. For example, when the intermediate product charging process (S210), the reducing agent charging process (S220), and the flux charging process (S230) are performed simultaneously, the intermediate product, reducing agent, and flux are charged into the melting furnace while still mixed. Alternatively, the intermediate product, reducing agent, and flux can be continuously charged into the melting furnace over a predetermined period of time. As an example, the intermediate product, reducing agent, and flux are charged into a 500 kVA SAF melting furnace continuously for 3 to 4 hours, based on a standard of 1 ton. If 1 ton of intermediate product, reducing agent, and flux is charged in less than 3 hours, the intermediate product, reducing agent, and flux will accumulate on top of the slag without melting, requiring more thermal energy to melt them, resulting in heat loss. Furthermore, if 1 ton of intermediate products, reducing agent, and flux is charged over a period of more than 4 hours, the recovery efficiency of iron and valuable metals will be reduced. In this specification, the charging of 1 ton of intermediate products, reducing agent, and flux into a 500 kVA SAF melting furnace has been used as a standard, but this is merely an example and does not limit the present invention.

[0045] On the other hand, when the intermediate product charging process (S210), the reducing agent charging process (S220), and the flux charging process (S230) are performed, the intermediate product, reducing agent, and flux can be charged into the melting furnace when molten metal and slag have formed inside the melting furnace. That is, after a predetermined amount of metallic iron is initially melted and slag and molten metal are formed, the intermediate product charging process (S210), the reducing agent charging process (S220), and the flux charging process (S230) are performed in addition. 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 layer. In other words, the generated gas has the effect of preventing the foaming phenomenon of the molten metal and slag from occurring. Also, because the raw material layer does not cover the slag and metal layer, zinc is prevented from remaining as zinc oxide in the raw material layer. In this case, the dust is easily released to the outside, which has the effect of easily recovering valuable metals such as zinc and lead.

[0046] In the heating step (S240), the intermediate product charged into the melting furnace is heated to a pre-set temperature range so that it 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 inside, and as an example, power of 1,400 kWh to 1,700 kWh per ton of intermediate product may be supplied. In this case, the temperature inside the electric furnace can be adjusted to 1450°C to 1650°C, and the intermediate product can be melted and reduced within this temperature range. If the temperature inside the electric furnace is below 1450°C, the melting and reduction of the intermediate product may not proceed smoothly, and if the temperature inside the electric furnace is above 1650°C, manganese or silicon may be reduced and flow in as impurities, which may reduce the quality of the metallic iron produced.

[0047] On the other hand, the reaction in which iron oxide is reduced to metallic iron by a reducing agent during the heating process (S240) is as shown in the following reaction equations 6 to 8.

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

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

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

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

[0052] Referring to Figure 3, in the recovery process (S300), metallic iron and valuable metals contained in the melting furnace are recovered. The metallic iron content recovered in this recovery process (S300) may be between 90% and 97%. This recovery process (S300) may include a metallic iron recovery process (S310), a valuable metal recovery process (S320), and a slag recovery process (S330).

[0053] In the metallic iron recovery process (S310), the metallic iron that has been reduced from the intermediate products in the intermediate product processing process (S200) and contained in the melting furnace in a molten state is recovered. For example, the metallic iron contained in the melting furnace in a molten state will be 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 molten metallic iron can be discharged through the discharge channel at the bottom of the melting furnace. Alternatively, the metallic iron discharged from the melting furnace can be recovered in the form of an ingot, which is a hexahedron measuring 50cm × 20cm × 5cm, through the casting process. The carbon content of the metallic iron discharged from the melting furnace may be 0.5% to 2.5%, and the metallic iron may be pig iron. Furthermore, the iron content of the metallic iron recovered in the metallic iron recovery process (S310) may be between 90% and 97%.

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

[0055] In the slag recovery process (S330), slag contained in the melting furnace is recovered. For example, in the melting furnace, slag is located above the metallic iron due to phase separation caused by the difference in specific gravity between it and the metallic iron. When the metallic iron is discharged through the metallic iron recovery process (S310), the slag can be discharged from the melting furnace through the discharge channel. Some of the slag recovered in this slag recovery process (S330) can be recycled as a raw material for cement, etc.

[0056] The following describes the content and recovery rate of metallic iron and valuable metals produced according to the embodiments of the present invention. In this embodiment, four different intermediate products were charged into the melting furnace as described below, and the content (weight %) of each component of the charged intermediate products is 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 coal was used as a reducing agent. The coal was blended so that its iron oxide content in intermediate product A was 2.5 equivalents. In this case, the basicity of the slag was 0.6. The content (weight %) and recovery rate (%) 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%, while 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 the melting furnace, and coal was used as a reducing agent. The coal was blended so that its iron oxide content was 2.5 equivalents of that in intermediate product A. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The content (weight %) and recovery rate (%) 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%, while 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 coal was used as a reducing agent. The coal was blended so that it was in a ratio of 2.5 equivalents to the iron oxide contained in intermediate product B. In addition, 111 kg of quartz sand was charged into the melting furnace so that the basicity of the slag was 0.6. The content (weight %) and recovery rate (%) 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%, while 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 coal was used as a reducing agent. The coal was blended so that its iron oxide content was 2.5 equivalents of that in intermediate product C. In addition, 92 kg of quartz sand was charged into the melting furnace so that the basicity of the slag was 0.6. The content (weight %) and recovery rate (%) 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%, while 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 the melting furnace, and coal was used as a reducing agent. The coal was blended so that its iron oxide content was 2.5 equivalents of that contained in intermediate product D. In addition, 150 kg of quartz sand was charged into the melting furnace so that the basicity of the slag was 0.6. The content (weight %) and recovery rate (%) 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 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 that produced in Examples 1 and 2. Furthermore, in Examples 1 to 5, the recovery rate of iron recovered as metallic iron was 98% or higher, and the recovery rates of zinc and lead recovered as dust were 97% or higher.

[0067] As described above, each embodiment of the present invention makes it possible to produce metallic iron with a content of 90% or more, and has the effect of improving the recovery rate of metallic iron. It also has the effect of improving the recovery rate of valuable metals such as zinc and lead, and enabling their recycling. In this case, the amount of iron and valuable metals that are buried in landfills can be significantly reduced, and the cost required for landfill can be reduced. Furthermore, by improving the amount of iron and valuable metals recovered, the amount of slag generated can be reduced, and the amount of slag that needs to be processed can be minimized, resulting in cost savings.

[0068] [Example 6] In Example 6, 1 ton of intermediate product A was charged into the melting furnace, and coal was used as a reducing agent. The coal was blended so that its iron oxide content was 2.1 equivalents relative to the iron oxide contained in intermediate product A. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The content (weight %) and recovery rate (%) 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%, while 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 the melting furnace, and coal was used as a reducing agent. The coal was blended so that it was in a ratio of 1.7 equivalents to the iron oxide contained in intermediate product A. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The content (weight %) and recovery rate (%) 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%, while 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 the melting furnace, and coal was used as a reducing agent. The coal was blended so that its iron oxide content was 3.1 equivalents relative to the iron oxide contained in intermediate product A. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The content (weight %) and recovery rate (%) 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%, while 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 the melting furnace, and coal was used as a reducing agent. The coal was blended so that its iron oxide content was 1.3 equivalents of that in intermediate product A. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The content (weight %) and recovery rate (%) of metallic iron, slag, and dust produced 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%, while 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 the melting furnace, and coal was used as a reducing agent. The coal was blended so that the iron oxide ratio in intermediate product A was 4.6 equivalents. In addition, 20 kg of limestone was charged into the melting furnace so that the basicity of the slag was 0.8. The content (weight %) and recovery rate (%) of metallic iron, slag, and dust produced 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 was 89.68%, while the recovery rates of zinc and lead recovered as dust were 98.39% and 99.23%, respectively. Comparing Comparative Examples 1 and 2 with Examples 6 to 8, it can be confirmed that when the reducing agent is charged into the melting furnace in a manner that deviates from the iron oxide ratio of 1.7 to 3.1 equivalents contained in the intermediate product, the recovery rate of metallic iron decreases sharply. In other words, when the reducing agent is charged into the melting furnace at an iron oxide ratio of 1.7 to 3.1 equivalents contained in the intermediate product, the recovery rate of iron is improved. Furthermore, this has the effect of preventing the excessive charging of the reducing agent and the resulting increase in costs.

[0078] Although embodiments of the present invention have been described above with reference to the attached drawings, those with ordinary skill in the art to which the present invention pertains should be able to understand that the present invention can be implemented in other specific forms without changing its technical idea or essential features.

[0079] Therefore, the embodiments described above should be understood to be illustrative and not limiting in all respects. The scope of the present invention is indicated more by the claims than by the detailed description above, and all modifications or modified forms derived from the meaning and scope of the claims and the concept of equivalents thereto should be interpreted as being included within the scope of the present invention.

Claims

1. A steelmaking dust treatment process that processes steelmaking dust to produce an intermediate product containing iron, An intermediate product processing step involves heating the intermediate product, which has been charged into a melting furnace, within a pre-set temperature range so that it is melted and reduced. The process includes a recovery step of recovering metallic iron generated by reduction from the intermediate product and contained in the melting furnace while still molten, and recovering valuable metals generated in dust form in the intermediate product processing step, The intermediate product treatment step includes a reducing agent charging step of charging a carbon-containing reducing agent into the melting furnace in such a way that the amount of metallic iron reduced from the intermediate product increases. A method for recovering iron and valuable metals from steelmaking dust, wherein the reducing agent is charged into the melting furnace in an equivalent ratio of 1.7 to 3.1 iron oxides 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 involves determining the basicity (CaO / SiO) of the slag produced in the intermediate product treatment step. ２ This includes a flux charging step of charging flux into the melting furnace to adjust the temperature. The method for recovering iron and valuable metals from steelmaking dust according to claim 1, wherein the flux is charged into the melting furnace such that the basicity of the slag is 0.4 to 1.

5.

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

5. A method for recovering iron and valuable metals from steelmaking dust according to claim 1, wherein the recovery step includes a metal iron recovery step of discharging the molten metal iron contained in the melting furnace from the melting furnace and recovering the discharged metal iron in the form of an ingot through a casting step.

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

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

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

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