Method for utilizing electric furnace dust and granular material

Abstract

This application relates to a method for utilizing electric furnace dust and granulated material. The method includes: mixing electric furnace dust, powdered carbonaceous material, and bentonite at a mass ratio of 1:(4~20):(3~5) to obtain a mixture; granulating the mixture to obtain granules with a diameter of 10mm~15mm; before adding scrap steel and molten iron after tapping from the converter, sequentially adding the granules and 2t~4t of granulated carbonaceous material into the converter furnace, and shaking the converter once after adding the granules and carbonaceous material; allowing the converter to settle to allow the zinc component in the granules to volatilize and be captured; after settling, adding scrap steel and molten iron to the converter and performing top and bottom blowing steelmaking, wherein the top blowing oxygen supply intensity is controlled at 2.7 Nm³ during the steelmaking process. 3 / (t·min)~3.1Nm 3 / (t·min), bottom blowing gas supply intensity is 0.03Nm 3 / (t·min)~0.05Nm 3 / (t·min). This method completes zinc reduction-volatilization-capture directly during the converter's "empty furnace" window without the need for a rotary kiln / rotary hearth furnace, followed by seamless steelmaking.

Description

Technical Field

[0001] This application belongs to the field of steelmaking technology, and in particular relates to a method for utilizing electric furnace dust and granular materials. Background Technology

[0002] With the rapid increase in the proportion of electric arc furnace (EAF) processes, the annual emissions of EAF dust have exceeded two million tons. EAF dust is classified as hazardous waste due to its enrichment in heavy metals such as Zn, Pb, and Cr, but it also contains 10%–40% ZnO and 30%–55% total iron, making it an important secondary resource. Current pyrometallurgical treatment requires the construction of new rotary kilns or rotary hearth furnaces, which involve high investment, large land area, and high energy consumption, and cannot be coupled online with the main steelmaking line. If the dust is directly added to the converter in a cold state, a series of problems will occur, including zinc circulation enrichment, furnace lining erosion, molten pool heat loss, and uncontrolled splashing, leading to smelting instability. Summary of the Invention

[0003] This application provides a method for utilizing electric furnace dust and granular materials to solve the following technical problem: how to efficiently recover zinc from electric furnace dust and simultaneously utilize iron oxides in a converter without building a rotary kiln / rotary hearth furnace.

[0004] In a first aspect, embodiments of this application provide a method for utilizing electric furnace dust, the method comprising: Electric furnace dust, powdered carbonaceous materials and bentonite are mixed at a mass ratio of 1:(4~20):(3~5) to obtain a mixture; The mixture is granulated to obtain granules with a diameter of 10 mm to 15 mm; Before the steel tapping process is completed and before scrap steel and molten iron are added, the granular material and 2t~4t of granular carbonaceous material are added to the converter furnace in sequence, and the converter is shaken back and forth once after the granular material and granular carbonaceous material are added. The converter is left to stand for 15 to 20 minutes to allow the zinc component in the granular material to volatilize and be captured. After the settling period, scrap steel and molten iron are added to the converter, and top and bottom blowing steelmaking is carried out. The oxygen supply intensity of the top blowing is controlled at 2.7 Nm³ during the steelmaking process. 3 / (t·min)~3.1Nm 3 / (t·min), bottom blowing gas supply intensity is 0.03Nm 3 / (t·min)~0.05Nm 3 / (t·min).

[0005] Optionally, the mass fraction of ZnO in the electric furnace dust is 10% to 40%.

[0006] Optionally, the maximum particle size of the powdered carbonaceous material is ≤100μm, and 75% of the powdered carbonaceous material by mass fraction has a particle size ≤50μm.

[0007] Optionally, the maximum particle size of the bentonite is ≤100μm, and the particle size of 75% of the bentonite by mass fraction is ≤50μm.

[0008] Optionally, the amount of granular material added is 3t / furnace to 6t / furnace.

[0009] Optionally, during the top and bottom combined blowing steelmaking process, when the oxygen blowing amount accounts for 2% to 5% of the total oxygen blowing amount, 15 kg / t steel to 18 kg / t steel of lime and 5 kg / t steel to 7 kg / t steel of lightly calcined dolomite are added to the converter. When the oxygen blowing rate accounts for 25% to 30% of the total oxygen blowing rate, lime of 15 kg / t steel to 18 kg / t steel and lightly calcined dolomite of 10 kg / t steel to 15 kg / t steel are added to the converter again.

[0010] Optionally, in the top and bottom blowing steelmaking process: When the oxygen blowing volume accounts for 0~10% of the total oxygen blowing volume, the oxygen lance position is 220cm. When the oxygen blowing volume accounts for 10% to 15% of the total oxygen blowing volume, the oxygen lance position is 200cm. When the oxygen blowing volume accounts for 15% to 40% of the total oxygen blowing volume, the oxygen lance position is continuously lowered from 200cm to 180cm. When the oxygen blowing volume accounts for 40% to 100% of the total oxygen blowing volume, the oxygen lance position should be maintained at 180cm.

[0011] Optionally, in the top and bottom blowing steelmaking process, the final slag basicity is 3.0~3.5, the FeO mass fraction in the final slag is 16%~20%, and the MgO mass fraction in the final slag is 9%~15%.

[0012] Secondly, this application provides a granular material composed of electric furnace dust, powdered carbonaceous material and bentonite in a mass ratio of 1:(4~20):(3~5). The diameter of the granular material is 10mm~15mm, and the mass fraction of ZnO in the electric furnace dust is 10%~40%.

[0013] Optionally, the maximum particle size of the powdered carbonaceous material is ≤100μm, and 75% of the powdered carbonaceous material by mass fraction has a particle size ≤50μm; The maximum particle size of the bentonite is ≤100μm, and the particle size of 75% of the bentonite by mass fraction is ≤50μm. The technical solution provided in this application has the following advantages compared to the prior art: This application provides a method for utilizing electric furnace dust. This method, without the need for a rotary kiln / rotary hearth furnace, directly completes zinc reduction-volatilization-collection during the converter's "empty furnace" window, followed by seamless steelmaking. Its fundamental innovation can be summarized as "three couplings and one inhibition": 1. The granular material is mixed with carbon at a ratio of 1:4 to 20. Carbon acts as both a solid reducing agent for ZnO (ZnO + C → Zn↑ + CO) and a stepwise reducing agent for Fe2O3 (Fe2O3 → Fe3O4 → FeO → Fe). The high carbon ratio ensures that carbon surrounds each dust particle, forming a strong local reducing potential; the 10–15 mm particle size + bentonite binding ensures particle strength while leaving channels for CO / Zn gas to escape, avoiding "metallization" and blockage.

[0014] 2. After the converter taps the steel, the furnace still maintains a residual heat atmosphere of over 1200℃ and rich in CO. After the particles enter the furnace, the furnace body is "shaken back and forth once" to make the particles spread evenly on the surface of the molten pool and expand the contact area with the high-temperature gas phase. During the 15-20 minute settling period, the reduced Zn(g) rises with the furnace gas and is captured by the post-dust collection system, realizing the short-process volatilization of "furnace is kiln".

[0015] 3. After settling, add scrap steel and molten iron, along with residual carbon and reduced FeO, into the molten pool: carbon provides the chemical heat required for subsequent heating, and FeO directly participates in slag formation, reducing lime consumption; top blowing 2.7–3.1 Nm 3 / (t·min) High oxygen intensity rapid decarburization and heating, bottom blowing 0.03–0.05 Nm 3 Weak stirring (t·min) avoids slag entrapment and ensures metal recovery >90%.

[0016] 4. Taking advantage of the high CO partial pressure (>40kPa) and extremely low O2 partial pressure in the converter, Zn(g) is "encased" by the CO atmosphere during its ascent, with a secondary oxidation rate of <3%; at the same time, the excess particulate carbon forms a carburized layer, further blocking the internal diffusion of O2.

[0017] Through the above-mentioned "three couplings and one suppression", the four steps of "reduction-volatilization-dust collection-steelmaking" are completed in a single converter without the need for additional kilns, achieving efficient zinc recovery (>85%) and simultaneous utilization of iron resources, with the shortest process and lowest energy consumption. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0020] In a first aspect, embodiments of this application provide a method for utilizing electric furnace dust, the method comprising: Electric furnace dust, powdered carbonaceous materials and bentonite are mixed at a mass ratio of 1:(4~20):(3~5) to obtain a mixture; The mixture is granulated to obtain granules with a diameter of 10 mm to 15 mm; Before the steel tapping process is completed and before scrap steel and molten iron are added, the granular material and 2t~4t of granular carbonaceous material are added to the converter furnace in sequence, and the converter is shaken back and forth once after the granular material and granular carbonaceous material are added. The converter is left to stand for 15 to 20 minutes to allow the zinc component in the granular material to volatilize and be captured. After the settling period, scrap steel and molten iron are added to the converter, and top and bottom blowing steelmaking is carried out. The oxygen supply intensity of the top blowing is controlled at 2.7 Nm³ during the steelmaking process. 3 / (t·min)~3.1Nm 3 / (t·min), bottom blowing gas supply intensity is 0.03Nm 3 / (t·min)~0.05Nm 3 / (t·min).

[0021] Excessive amounts of powdered carbonaceous material with mass ratios of 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, and 1:20 surround the ZnO and Fe2O3 particles in the electric furnace dust, thereby forming a strong reducing micro-region with a local CO partial pressure ≥0.1MPa inside the particles. This allows ZnO to be reduced to Zn vapor by carbon and separated from the iron oxides. The addition of bentonite at mass ratios of 3%, 3.5%, 4%, 4.5%, and 5% causes the mixture to produce a liquid-phase binding water film, thereby consolidating the electric furnace dust particles and powdered carbonaceous material particles into one, thus avoiding dust generation during subsequent transportation and addition processes and ensuring close contact between the reducing agent and the oxides.

[0022] Granulation diameters of 10mm, 11mm, 12mm, 13mm, 14mm, and 15mm maintain skeletal gaps within the converter furnace, allowing Zn vapor to escape rapidly and thus shortening the volatilization time. Simultaneously, a particle size of 10-15mm ensures that the temperature gradient from the surface to the interior of the particles is ≤50℃ during a 15-20 minute settling period, thereby preventing particle bursting and maintaining the ventilation channels within the furnace.

[0023] When the converter tapping temperature reaches ≥1250℃, add 2t, 2.2t, 2.5t, 2.8t, 3.0t, 3.2t, 3.5t, 3.8t, and 4.0t of granular carbonaceous material to lay a bottom layer, and then add granular material on top. This physically isolates the granular material from the converter magnesia-carbon lining, thereby inhibiting the erosion of the lining by the low-melting-point Zn-Fe alloy phase generated during reduction. Shake once to homogenize the thickness of the granular material layer to 100mm±20mm, thereby increasing the contact area between the granular material and the high-temperature gas phase, and thus improving the Zn reduction-volatilization rate.

[0024] The particles were allowed to stand for 15, 16, 17, 18, 19, and 20 minutes to raise the center temperature to ≥1100℃, thereby ensuring that the ZnO reduction reaction was ≥85% complete and that the Zn vapor concentration reached ≥15 g / Nm³. 3 This is to ensure efficient dust collection by the subsequent dust collection system.

[0025] Top-blown oxygen supply intensities: 2.7, 2.8, 2.9, 3.0, 3.1 Nm 3 / (t·min) and bottom blowing 0.03, 0.04, 0.05 Nm 3The composite blowing process with a rate of / (t·min) enables the decarburization rate of the molten pool to reach 0.18~0.22%C / min, thereby rapidly melting iron oxides into the slag and reducing them to metallic iron, thus achieving simultaneous recovery of iron resources; at the same time, the high stirring energy can suppress the secondary oxidation of Zn vapor, thereby ensuring a total zinc recovery rate of ≥80%, thus solving the technical problem of "efficiently recovering zinc and simultaneously utilizing iron oxides without building a rotary kiln / rotary hearth furnace".

[0026] In some embodiments, the mass fraction of ZnO in the electric furnace dust is 10% to 40%.

[0027] The mass fraction of ZnO in the electric furnace dust is 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, and 40%. A ZnO mass fraction of 10-40% results in 100-400 kg of ZnO per ton of granular material. Under the condition of a carbon excess coefficient ≥1.2, a theoretical Zn vapor production of 33-132 kg is achieved. This ensures that the secondary zinc oxide grade of the dust collection system is ≥30%, thereby meeting the economic threshold of the subsequent wet zinc extraction process and solving the technical problem of "efficient zinc recovery".

[0028] In some embodiments, the maximum particle size of the powdered carbonaceous material is ≤100μm, and 75% of the powdered carbonaceous material by mass fraction has a particle size ≤50μm.

[0029] Carbon particles with a diameter ≤50μm and a specific surface area ≥200cm² 2 / g, thus achieving a carbon-zinc oxide interfacial reaction rate constant ≥0.05s at 1100℃. -1 This allows the ZnO reduction reaction to be completed at a rate of ≥90% within 15 minutes, thereby shortening the settling time and increasing the converter operating rate, thus solving the technical problem of "efficient zinc recovery without additional kiln construction".

[0030] In some embodiments, the maximum particle size of the bentonite is ≤100μm, and the particle size of 75% of the bentonite by mass fraction is ≤50μm.

[0031] Bentonite particles with a particle size ≤50μm absorb water and expand at a rate ≥300% within 2 minutes, thereby forming a capillary bond force ≥1.5kN / m during the granulation process. This results in a drop strength of ≥8 times / 0.5m for the granules, thus preventing pulverization during the belt conveyor-feeding process, ensuring that the reducing agent and oxide do not separate, and maintaining a high zinc recovery rate.

[0032] In some embodiments, the amount of granular material added is 3t / furnace to 6t / furnace.

[0033] The amount of granular material added is 3t / furnace, 3.2t / furnace, 3.5t / furnace, 3.8t / furnace, 4.0t / furnace, 4.2t / furnace, 4.5t / furnace, 4.8t / furnace, 5.0t / furnace, 5.2t / furnace, 5.5t / furnace, 5.8t / furnace, and 6.0t / furnace. The 3-6t granular material brings in 300-2400kg of ZnO, thus forming a Zn load of 1.4-11.4kg / t steel in the 210t converter. This allows the daily output of secondary zinc oxide from the dust collection system to reach 1-8t, thereby meeting the balance of the steel plant's self-produced zinc recycling volume and solving the technical problem of "efficient zinc recovery". At the same time, the 6t upper limit ensures that the granular material layer thickness is ≤150mm, thus avoiding a furnace temperature drop of >80℃ during the settling period. This ensures that the temperature during the subsequent molten iron addition process is ≥1300℃, thereby maintaining the steelmaking rhythm.

[0034] In some embodiments, during the top and bottom combined blowing steelmaking process, when the amount of oxygen blown accounts for 2% to 5% of the total amount of oxygen blown, 15 kg / t steel to 18 kg / t steel of lime and 5 kg / t steel to 7 kg / t steel of lightly calcined dolomite are added to the converter. When the oxygen blowing rate accounts for 25% to 30% of the total oxygen blowing rate, lime of 15 kg / t steel to 18 kg / t steel and lightly calcined dolomite of 10 kg / t steel to 15 kg / t steel are added to the converter again.

[0035] During the top and bottom combined blowing steelmaking process, when the oxygen blowing rate accounts for 2%, 3%, 4%, and 5% of the total oxygen blowing rate, lime of 15 kg / t steel, 16 kg / t steel, 17 kg / t steel, and 18 kg / t steel, and light-burned dolomite of 5 kg / t steel, 6 kg / t steel, and 7 kg / t steel, are added to the converter. When the oxygen blowing rate accounts for 25%, 26%, 27%, 28%, 29%, and 30% of the total oxygen blowing rate, lime of 15 kg / t steel, 16 kg / t steel, 17 kg / t steel, and 18 kg / t steel, and light-burned dolomite of 10 kg / t steel, 11 kg / t steel, 12 kg / t steel, 13 kg / t steel, 14 kg / t steel, and 15 kg / t steel, are added again. The first stage involves adding lime and lightly calcined dolomite to achieve an initial slag basicity of 2.0-2.2, which rapidly combines the SiO2 brought in by the granular material into CaO·SiO2, thereby inhibiting the formation of low-volatility zinc silicate from SiO2 and ZnO, thus increasing the Zn volatilization rate by ≥5%. The second stage involves adding lime and lightly calcined dolomite to raise the slag basicity to 3.0-3.5, thereby controlling the FeO activity at 0.25-0.30, which promotes the reduction of iron oxides to metallic iron at the slag-gold interface, thereby increasing the iron recovery rate by ≥2%, and thus solving the technical problem of "simultaneous utilization of iron oxides".

[0036] In some embodiments, during the top and bottom blowing steelmaking process: When the oxygen blowing volume accounts for 0~10% of the total oxygen blowing volume, the oxygen lance position is 220cm. When the oxygen blowing volume accounts for 10% to 15% of the total oxygen blowing volume, the oxygen lance position is 200cm. When the oxygen blowing volume accounts for 15% to 40% of the total oxygen blowing volume, the oxygen lance position is continuously lowered from 200cm to 180cm. When the oxygen blowing volume accounts for 40% to 100% of the total oxygen blowing volume, the oxygen lance position should be maintained at 180cm.

[0037] The 220cm gun position ensures that the oxygen jet impact depth is ≤200mm, thereby avoiding premature burning of residual carbon in the granular material due to the initial violent decarburization exothermic reaction, thus ensuring that the reduction reaction lasts for 15 minutes; the 180cm gun position ensures that the jet impact depth is ≥400mm, thereby strengthening the stirring of the molten pool, thereby reducing FeO in the slag to metallic iron, improving the iron recovery rate, and thus solving the technical problem of "simultaneous utilization of iron oxides".

[0038] In some embodiments, during the top-and-bottom combined blowing steelmaking process, the final slag basicity is 3.0 to 3.5, the FeO mass fraction in the final slag is 16% to 20%, and the MgO mass fraction in the final slag is 9% to 15%.

[0039] The final slag basicity is 3.0, 3.1, 3.2, 3.3, 3.4, and 3.5; the final slag FeO mass fraction is 16%, 17%, 18%, 19%, and 20%; and the final slag MgO mass fraction is 9%, 10%, 11%, 12%, 13%, 14%, and 15%. A basicity of 3.0–3.5 ensures that the CaO activity in the slag is ≥0.6, thereby increasing the phosphorus distribution ratio (Lp) to 80–100, thus guaranteeing a dephosphorization rate ≥90%. FeO of 16–20% provides oxygen potential to promote decarburization while avoiding excessive FeO leading to iron loss, thus stabilizing the iron recovery rate at 92–94%. MgO of 9–15% lowers the slag melting point to 1400–1450℃, thereby improving the slag splashing and furnace protection effect, and thus solving the dual technical problems of "converter lining maintenance" and "iron resource recovery".

[0040] Secondly, this application provides a granular material composed of electric furnace dust, powdered carbonaceous material and bentonite in a mass ratio of 1:(4~20):(3~5). The diameter of the granular material is 10mm~15mm, and the mass fraction of ZnO in the electric furnace dust is 10%~40%.

[0041] This granular material can achieve the triple integration of "micron-level contact between carbon and oxides + air permeability of the particle skeleton + strength and shatter resistance" before entering the furnace, thereby ensuring the success of the "15-minute settling-reduction-volatilization" process window in the subsequent converter, thus solving the technical problem of "efficiently recovering zinc and simultaneously utilizing iron oxides without building a kiln".

[0042] In some embodiments, the maximum particle size of the powdered carbonaceous material is ≤100 μm, and 75% of the powdered carbonaceous material by mass fraction has a particle size ≤50 μm; The maximum particle size of the bentonite is ≤100μm, and the particle size of 75% of the bentonite by mass fraction is ≤50μm.

[0043] This particle size combination ensures that the carbon-oxide interface distance inside the granules is ≤25μm, thereby shortening the solid-solid reduction reaction time to ≤900s and ensuring that the zinc reduction rate is ≥90% within a 15min settling period. At the same time, the bentonite particle size of ≤50μm allows the formation of a continuous gel network after water absorption, thereby increasing the compressive strength of the particles to ≥10N / particle, thus avoiding breakage during conveyor belt transport, maintaining close contact between the reducing agent and the oxide, and ultimately solving the technical problem of "efficient zinc recovery".

[0044] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0045] I. Implementation Examples Example 1 Step a: Mix electric furnace dust, powdered carbonaceous material and bentonite at a mass ratio of 1:12:3.6 to obtain a mixture; Step b: Granulate the mixture to obtain granules with a diameter of 12mm; Step c: After the 210t converter finishes tapping and before scrap steel and molten iron are added, add 4t of granular material and 3.5t of granular carbonaceous material into the converter furnace in sequence, and shake the converter back and forth once after adding the granular material and granular carbonaceous material. Step d: Let the converter stand for 17 minutes to allow the zinc component in the granules to volatilize and be captured; Step e: After settling, add scrap steel and molten iron to the converter and perform top and bottom blowing steelmaking. During the steelmaking process, control the top blowing oxygen supply intensity to 2.9 Nm. 3 / (t·min), bottom blowing gas supply intensity is 0.04Nm 3 / (t·min).

[0046] The ZnO mass fraction in the electric furnace dust described in claim 2 is 28.6%; the parameters in claims 3, 4, 5, 6, 7, and 8 are all implemented according to the intermediate values ​​of the claims.

[0047] Example 2 Step a: Mix electric furnace dust, powdered carbonaceous material and bentonite at a mass ratio of 1:5.5:4.1 to obtain a mixture; Step b: Granulate the mixture to obtain granules with a diameter of 14.5 mm; Step c: After the 210t converter finishes tapping and before scrap steel and molten iron are added, add 5t of granular material and 4t of granular carbonaceous material to the converter furnace in sequence, and shake the converter back and forth once after adding the granular material and granular carbonaceous material. Step d: Let the converter stand for 20 minutes to allow the zinc component in the granular material to volatilize and be captured; Step e: After settling, add scrap steel and molten iron to the converter and perform top and bottom blowing steelmaking. During the steelmaking process, control the top blowing oxygen supply intensity to 2.8 Nm. 3 / (t·min), bottom blowing gas supply intensity is 0.035Nm 3 / (t·min).

[0048] The ZnO mass fraction in the electric furnace dust described in claim 2 is 12.3%; the parameters of the other claims are implemented according to the intermediate values.

[0049] Example 3 Step a: Mix electric furnace dust, powdered carbonaceous material and bentonite at a mass ratio of 1:15.5:4.8 to obtain a mixture; Step b: Granulate the mixture to obtain granules with a diameter of 11 mm; Step c: After the 210t converter finishes tapping and before scrap steel and molten iron are added, add 3t of granular material and 4t of granular carbonaceous material to the converter furnace in sequence, and shake the converter back and forth once after adding the granular material and granular carbonaceous material. Step d: Let the converter stand for 15 minutes to allow the zinc component in the granular material to volatilize and be captured; Step e: After settling, add scrap steel and molten iron to the converter and perform top and bottom blowing steelmaking. During the steelmaking process, control the top blowing oxygen supply intensity to 3.0 Nm. 3 / (t·min), bottom blowing gas supply intensity is 0.05Nm 3 / (t·min).

[0050] The ZnO mass fraction in the electric furnace dust described in claim 2 is 36.4%; the parameters of the other claims are implemented according to the intermediate values.

[0051] Example 4 Step a: Mix electric furnace dust, powdered carbonaceous material and bentonite in a mass ratio of 1:4:3 to obtain a mixture; Step b: Granulate the mixture to obtain granules with a diameter of 10 mm; Step c: After the 210t converter finishes tapping and before scrap steel and molten iron are added, add 3t of granular material and 2t of granular carbonaceous material to the converter furnace in sequence, and shake the converter back and forth once after adding the granular material and granular carbonaceous material. Step d: Let the converter stand for 15 minutes to allow the zinc component in the granular material to volatilize and be captured; Step e: After settling, add scrap steel and molten iron to the converter and perform top and bottom blowing steelmaking. During the steelmaking process, control the top blowing oxygen supply intensity to 2.7 Nm. 3 / (t·min), bottom blowing gas supply intensity is 0.03Nm 3 / (t·min).

[0052] The ZnO mass fraction in the electric furnace dust described in claim 2 is 10%; the parameters of the other claims are implemented according to the minimum value.

[0053] Example 5 Step a: Mix electric furnace dust, powdered carbonaceous material and bentonite at a mass ratio of 1:20:5 to obtain a mixture; Step b: Granulate the mixture to obtain granules with a diameter of 15mm; Step c: After the 210t converter finishes tapping and before scrap steel and molten iron are added, add 6t of granular material and 4t of granular carbonaceous material to the converter furnace in sequence, and shake the converter back and forth once after adding the granular material and granular carbonaceous material. Step d: Let the converter stand for 20 minutes to allow the zinc component in the granular material to volatilize and be captured; Step e: After settling, add scrap steel and molten iron to the converter and perform top and bottom blowing steelmaking. During the steelmaking process, control the top blowing oxygen supply intensity to 3.1 Nm³. 3 / (t·min), bottom blowing gas supply intensity is 0.05Nm 3 / (t·min).

[0054] The ZnO mass fraction in the electric furnace dust described in claim 2 is 40%; the parameters of the other claims are executed at their maximum values.

[0055] Example 6 Step a: Mix electric furnace dust, powdered carbonaceous material and bentonite in a mass ratio of 1:8:4 to obtain a mixture; Step b: Granulate the mixture to obtain granules with a diameter of 13mm; Step c: After the 180t converter finishes tapping and before scrap steel and molten iron are added, add 3.5t of granular material and 2.5t of granular carbonaceous material to the converter furnace in sequence, and shake the converter back and forth once after adding the granular material and granular carbonaceous material. Step d: Let the converter stand for 18 minutes to allow the zinc component in the granules to volatilize and be captured; Step e: After settling, add scrap steel and molten iron to the converter and perform top and bottom blowing steelmaking. During the steelmaking process, control the top blowing oxygen supply intensity to 2.85 Nm. 3 / (t·min), bottom blowing gas supply intensity is 0.04Nm 3 / (t·min).

[0056] The ZnO mass fraction in the electric furnace dust described in claim 2 is 20%; the parameters of the other claims are implemented according to the intermediate values.

[0057] Example 7 Step a: Mix electric furnace dust, powdered carbonaceous material and bentonite at a mass ratio of 1:10:3.5 to obtain a mixture; Step b: Granulate the mixture to obtain granules with a diameter of 11.5 mm; Step c: After the 300t converter finishes tapping and before scrap steel and molten iron are added, add 5.5t of granular material and 3t of granular carbonaceous material into the converter furnace in sequence, and shake the converter back and forth once after adding the granular material and granular carbonaceous material. Step d: Let the converter stand for 16 minutes to allow the zinc component in the granules to volatilize and be captured; Step e: After settling, add scrap steel and molten iron to the converter and perform top and bottom blowing steelmaking. During the steelmaking process, control the top blowing oxygen supply intensity to 2.9 Nm. 3 / (t·min), bottom blowing gas supply intensity is 0.045Nm 3 / (t·min).

[0058] The ZnO mass fraction in the electric furnace dust described in claim 2 is 25%; the parameters of the other claims are implemented according to the intermediate values.

[0059] Example 8 Step a: Mix electric furnace dust, powdered carbonaceous material and bentonite in a mass ratio of 1:6:3.2 to obtain a mixture; Step b: Granulate the mixture to obtain granules with a diameter of 12.5 mm; Step c: After the 210t converter finishes tapping and before scrap steel and molten iron are added, add 4.2t of granular material and 3t of granular carbonaceous material into the converter furnace in sequence, and shake the converter back and forth once after adding the granular material and granular carbonaceous material. Step d: Let the converter stand for 19 minutes to allow the zinc component in the granular material to volatilize and be captured; Step e: After settling, add scrap steel and molten iron to the converter and perform top and bottom blowing steelmaking. During the steelmaking process, control the top blowing oxygen supply intensity to 2.95 Nm. 3 / (t·min), bottom blowing gas supply intensity is 0.035Nm 3 / (t·min).

[0060] The ZnO mass fraction in the electric furnace dust described in claim 2 is 15%; the parameters of the other claims are implemented according to the intermediate values.

[0061] Example 9 Step a: Mix electric furnace dust, powdered carbonaceous material and bentonite at a mass ratio of 1:18:4.5 to obtain a mixture; Step b: Granulate the mixture to obtain granules with a diameter of 14 mm; Step c: After the 210t converter finishes tapping and before scrap steel and molten iron are added, add 5.8t of granular material and 3.8t of granular carbonaceous material to the converter furnace in sequence, and shake the converter back and forth once after adding the granular material and granular carbonaceous material. Step d: Let the converter stand for 17 minutes to allow the zinc component in the granules to volatilize and be captured; Step e: After settling, add scrap steel and molten iron to the converter and perform top and bottom blowing steelmaking. During the steelmaking process, control the top blowing oxygen supply intensity to 3.05 Nm. 3 / (t·min), bottom blowing gas supply intensity is 0.05Nm 3 / (t·min).

[0062] The ZnO mass fraction in the electric furnace dust described in claim 2 is 38%; the parameters of the other claims are implemented according to the intermediate values.

[0063] II. Comparative Example Comparative Example 1 Step a: Do not add any granular material or granular carbonaceous material to the converter; Step b: Immediately after the converter tapping is completed, add scrap steel and molten iron, and smelt according to the conventional top and bottom blowing steelmaking system; Step c: Control the top-blown oxygen supply intensity to 2.9 Nm during the steelmaking process. 3 / (t·min), bottom blowing gas supply intensity is 0.04Nm 3 / (t·min).

[0064] Comparative Example 2 Step a: Mix electric furnace dust, powdered carbonaceous material and bentonite in a mass ratio of 1:1:1 to obtain a mixture; Step b: Granulate the mixture to obtain granules with a diameter of 20mm; Step c: After the 210t converter finishes tapping and before scrap steel and molten iron are added, add 7t of granular material and 1t of granular carbonaceous material to the converter furnace in sequence, and shake the converter back and forth once after adding the granular material and granular carbonaceous material. Step d: Let the converter stand for 5 minutes to allow the zinc component in the granules to volatilize and be captured; Step e: After settling, add scrap steel and molten iron to the converter and perform top and bottom blowing steelmaking. During the steelmaking process, control the top blowing oxygen supply intensity to 2.9 Nm. 3 / (t·min), bottom blowing gas supply intensity is 0.04Nm 3 / (t·min).

[0065] Comparative Example 3 Step a: Mix electric furnace dust, powdered carbonaceous material and bentonite at a mass ratio of 1:25:6 to obtain a mixture; Step b: Granulate the mixture to obtain granules with a diameter of 8mm; Step c: After the 210t converter finishes tapping and before scrap steel and molten iron are added, add 2t of granular material and 5t of granular carbonaceous material to the converter furnace in sequence, and shake the converter back and forth once after adding the granular material and granular carbonaceous material. Step d: Let the converter stand for 25 minutes to allow the zinc component in the granules to volatilize and be captured; Step e: After settling, add scrap steel and molten iron to the converter and perform top and bottom blowing steelmaking. During the steelmaking process, control the top blowing oxygen supply intensity to 2.9 Nm. 3 / (t·min), bottom blowing gas supply intensity is 0.04Nm 3 / (t·min).

[0066] III. Results Data Experimental methods for evaluating results: Zinc volatilization rate: Immediately after the settling period, all dust was collected using the converter dust collection system. The ZnO mass fraction in the dust was determined by XRF and the volatilization rate was calculated by comparing it with the initial ZnO mass fraction of the granular material.

[0067] Secondary zinc oxide grade: The ZnO mass fraction of the same dust sample was independently re-determined by hydrochloric acid dissolution-EDTA titration, and the average of the two determinations was taken.

[0068] Iron recovery rate: Based on the total amount of metallic iron fed into the furnace, the amount of metallic iron recovered is obtained by multiplying the final steel composition by the weight of the molten steel, and the recovery rate is calculated.

[0069] Lime consumption per ton of steel: Weigh the total amount of lime actually fed into the furnace and divide it by the number of qualified molten steel tons.

[0070] Furnace lining erosion rate: The residual thickness of the trunnion area is measured by a laser thickness gauge after smelting, and the difference between the residual thickness and the thickness before smelting is divided by the number of smelting furnaces.

[0071] Table 1. Results data for both the examples and comparative examples.

[0072] As shown in Table 1, the technological advancements of this application's technical solution include: 1. The lowest zinc volatilization rate of 75.1% (Example 4) is still higher than the highest value of 65.3% in the comparative example, which shows that the combination of "mass ratio 1:(4~20):(3~5) + standing for 15~20 min" described in the examples of this application can improve the zinc reduction-volatilization efficiency by at least 9.8 percentage points under the condition of not building a rotary kiln / rotary hearth furnace, thereby solving the technical problem of "efficient zinc recovery".

[0073] 2. The lowest value of secondary zinc oxide grade, 28.4% (Example 4), is still higher than the highest value of 22.1% in the comparative example. This indicates that the raw material range of "ZnO 10%~40%" described in the embodiments of this application and the particle size combination of "≤50μm carbon / bentonite" described in claims 3 and 4 can increase the high value-added secondary zinc oxide grade obtained by the dust collection system by at least 6.3 percentage points, thereby solving the potential defect of "low economic value of zinc products".

[0074] 3. The lowest iron recovery rate of 91.9% (Example 4) is still higher than the highest value of 90.1% in the comparative example, which shows that the dual control range of "final slag basicity 3.0~3.5 + FeO 16%~20%" described in the examples of this application can increase the recovery rate of iron oxides reduced to metallic iron at the slag-gold interface by at least 1.8 percentage points, thereby solving the technical problem of "simultaneous utilization of iron oxides".

[0075] 4. The highest lime consumption per ton of steel (36 kg) (Example 4) is still lower than the lowest value of 38 kg in the comparative example, which shows that the "staged slag making" system described in this application reduces lime consumption by at least 2 kg / t of steel, thereby solving the derivative demand of "reducing auxiliary material costs".

[0076] 5. The highest erosion rate of the furnace lining, 0.14 mm / furnace (Example 4), is still lower than the lowest value of 0.20 mm / furnace in the comparative example. This shows that the "first lay particulate carbonaceous material for isolation + shake and lay flat" step described in the embodiments of this application reduces the erosion rate of the furnace lining by at least 0.06 mm / furnace, thereby solving the associated problem of "difficult maintenance of converter lining".

[0077] In summary, the data chain in Table 1 proves that, without the construction of a rotary kiln / rotary hearth furnace, the method combination in the embodiments of this application simultaneously achieves five technological advancements: "increased zinc recovery rate, increased zinc product grade, increased iron recovery rate, decreased auxiliary material consumption, and decreased furnace lining erosion," thereby comprehensively solving the technical problem of "efficiently recovering zinc from electric furnace dust and simultaneously utilizing iron oxides."

[0078] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for utilizing electric furnace dust, characterized in that, The method includes: Electric furnace dust, powdered carbonaceous materials and bentonite are mixed at a mass ratio of 1:(4~20):(3~5) to obtain a mixture; The mixture is granulated to obtain granules with a diameter of 10 mm to 15 mm; Before the steel tapping process is completed and before scrap steel and molten iron are added, the granular material and 2t~4t of granular carbonaceous material are added to the converter furnace in sequence, and the converter is shaken back and forth once after the granular material and granular carbonaceous material are added. The converter is left to stand for 15 to 20 minutes to allow the zinc component in the granular material to volatilize and be captured. After the settling period, scrap steel and molten iron are added to the converter, and top and bottom blowing steelmaking is carried out. The oxygen supply intensity of the top blowing is controlled at 2.7 Nm³ during the steelmaking process. 3 / (t·min)~3.1Nm 3 / (t·min), bottom blowing gas supply intensity is 0.03Nm 3 / (t·min)~0.05Nm 3 / (t·min).

2. The method for utilizing electric furnace dust according to claim 1, characterized in that, The mass fraction of ZnO in the electric furnace dust is 10%~40%.

3. The method for utilizing electric furnace dust according to claim 1, characterized in that, The maximum particle size of the powdered carbonaceous material is ≤100μm, and 75% of the powdered carbonaceous material by mass fraction has a particle size ≤50μm.

4. The method for utilizing electric furnace dust according to claim 1, characterized in that, The maximum particle size of the bentonite is ≤100μm, and the particle size of 75% of the bentonite by mass fraction is ≤50μm.

5. The method for utilizing electric furnace dust according to claim 1, characterized in that, The amount of granular material added is 3t / furnace to 6t / furnace.

6. The method for utilizing electric furnace dust according to claim 1, characterized in that, During the top and bottom combined blowing steelmaking process, when the oxygen blowing amount accounts for 2% to 5% of the total oxygen blowing amount, 15 kg / t steel to 18 kg / t steel of lime and 5 kg / t steel to 7 kg / t steel of lightly calcined dolomite are added to the converter. When the oxygen blowing rate accounts for 25% to 30% of the total oxygen blowing rate, lime of 15 kg / t steel to 18 kg / t steel and lightly calcined dolomite of 10 kg / t steel to 15 kg / t steel are added to the converter again.

7. The method for utilizing electric furnace dust according to claim 1, characterized in that, During the top and bottom blowing steelmaking process: When the oxygen blowing volume accounts for 0-10% of the total oxygen blowing volume, the oxygen lance position is 220cm. When the oxygen blowing volume accounts for 10% to 15% of the total oxygen blowing volume, the oxygen lance position is 200cm. When the oxygen blowing volume accounts for 15% to 40% of the total oxygen blowing volume, the oxygen lance position is continuously lowered from 200cm to 180cm. When the oxygen blowing volume accounts for 40% to 100% of the total oxygen blowing volume, the oxygen lance position should be maintained at 180cm.

8. The method for utilizing electric furnace dust according to claim 1, characterized in that, In the top-and-bottom combined blowing steelmaking process, the final slag basicity is 3.0~3.5, the FeO mass fraction in the final slag is 16%~20%, and the MgO mass fraction in the final slag is 9%~15%.

9. A granular material, characterized in that, The granular material is composed of electric furnace dust, powdered carbonaceous material and bentonite in a mass ratio of 1:(4~20):(3~5). The diameter of the granular material is 10mm~15mm, and the mass fraction of ZnO in the electric furnace dust is 10%~40%.

10. The granular material according to claim 9, characterized in that, The maximum particle size of the powdered carbonaceous material is ≤100μm, and 75% of the powdered carbonaceous material by mass fraction has a particle size ≤50μm. The maximum particle size of the bentonite is ≤100μm, and the particle size of 75% of the bentonite by mass fraction is ≤50μm.

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