Method for flash iron extraction and alloying by electric arc furnace using (nickel) copper powder tailings

Abstract

This invention discloses a method for rapid iron and alloy extraction from (nickel) copper powder tailings in an electric arc furnace, belonging to the field of solid waste resource utilization technology in non-ferrous metal smelting. The method involves first drying the (nickel) copper powder tailings and mixing it with a slag-forming agent and a reducing agent in a specific ratio; then, the mixture is injected through a top lance of the electric arc furnace, utilizing the high temperature of the electric arc to instantly melt and rapidly reduce the powder, forming a molten pool for constant-temperature smelting; finally, slag is skimmed, slag is retained, and the furnace is started up and steel is tapped. Compared with traditional processes, this invention has a shorter process flow, eliminates the need for agglomeration and large amounts of scrap steel, achieves an iron recovery rate exceeding 95%, an iron grade ≥95.4%, and significantly reduces the cost per ton of steel; it can also co-process low-grade slag such as vanadium, titanium, and manganese to prepare high-value-added alloys, solving the problem of low tailings utilization and realizing efficient resource utilization and green, low-carbon smelting of (nickel) copper tailings.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology in non-ferrous metal smelting, and specifically relates to a method for rapid iron and alloy extraction in an electric arc furnace using (nickel) copper powder tailings. Background Technology

[0002] (Nickel)copper powder tailings are the main solid waste generated during the pyrometallurgical smelting of (nickel)copper products. my country's annual discharge exceeds 30 million tons, with a cumulative stockpile of over 500 million tons. This type of solid waste typically contains 35% to 50% iron, as well as SiO2, CaO, Al2O3, and trace amounts of Zn and Pd, making it a highly promising secondary iron ore resource.

[0003] Currently, copper smelting tailings are mostly disposed of through stockpiling or low-value-added methods, with a utilization rate generally less than 40%. Valuable metals such as Fe, Cu, and Zn contained in the slag are encapsulated in the silicate slag phase, making effective separation impossible. Most processes can only recover a small amount of high-value metals, while a large amount of valuable metals are lost with the waste slag, resulting in serious waste of resources. At the same time, the product forms are relatively simple, mostly low-grade ferroalloys or building materials, lacking high-value-added products. Moreover, the products have high impurity content and mixed composition, which cannot meet the needs of high-end steel production.

[0004] Traditional processes employ a "mineral processing-pelletizing-blast furnace ironmaking" method, requiring pretreatment of tailings slag such as fine grinding and agglomeration. This process is cumbersome, energy-intensive, and results in molten iron with a high impurity content, necessitating additional refining processes. Furthermore, traditional AC electric arc furnaces rely heavily on scrap steel as their primary raw material, with raw material costs accounting for over 70% of their total cost.

[0005] For example, Chinese invention patent (CN102051428B) discloses a process for treating copper ore beneficiation tailings and nickel molten slag using a submerged arc furnace-shaking furnace-steelmaking electric arc furnace-refining furnace method. The process involves mixing copper ore beneficiation tailings with a carbonaceous reducing agent, granulating them into pellets, and then smelting them in a submerged arc furnace to obtain silicon-containing molten iron. After desulfurization, low-sulfur silicon-containing molten iron is obtained. Nickel molten slag is added to a shaking furnace, lime is added, and the low-sulfur silicon-containing molten iron is stirred and reduced to obtain reduced iron. The reduced iron is then fed into an electric arc furnace, where lime is added for desulfurization, decarburization, and dephosphorization treatment, ultimately yielding molten steel. This achieves comprehensive recovery of valuable metals from both the tailings and molten slag. While this patent rationally utilizes the composition of copper ore beneficiation tailings and fully recovers valuable metals from both the tailings and nickel molten slag, achieving comprehensive utilization, the process is cumbersome, lengthy, and suffers from high energy consumption and low processing efficiency, resulting in high costs for industrial application.

[0006] Although some patents have proposed improvement methods based on the above-mentioned shortcomings, the target objects, improvement measures and technical effects of these improvement methods are difficult to meet the actual application needs of (nickel) copper powder tailings reuse.

[0007] For example, Chinese invention patent (CN116103466B) discloses a method and system for high-efficiency steelmaking by top-injection of powder for large electric arc furnaces. Although the method calculates and allocates the amount of oxygen injected from the furnace top and furnace wall, the type of carrier gas medium, the type and amount of powder injected from the furnace top, and divides the injection stages, the powder is injected into the electric arc furnace molten pool in a top-blowing manner during the smelting process to enhance the stirring capacity of the molten pool, improve the reaction efficiency, and improve the quality of molten steel, the powder injected is dust, lime and carbon powder. The purpose is to improve the oxygen utilization rate and reduce the consumption of carbon powder and lime. Smelting still requires a large amount of scrap steel to be added into the furnace.

[0008] Based on the aforementioned technical requirements, our company has modified the existing electric arc furnace system and proposed a process route that pre-treats solid waste into powder, injects it into the electric arc furnace through a spray gun, and uses the high temperature of the electric arc to instantly melt the powdered material. Specifically, we have proposed a method for flash iron extraction and alloying using (nickel) copper powder tailings. Summary of the Invention

[0009] One object of the present invention is to disclose a method for flash iron and alloy extraction using (nickel) copper powder tailings, comprising the following steps: Step 1: Dry the (nickel) copper powder tailings to control the moisture content of the (nickel) copper powder tailings; Step 2: Mix the materials obtained in Step 1, the slag-forming agent, and the reducing agent evenly, and sieve through a 325-mesh screen; Step 3: The electric arc furnace is powered for smelting. The top spray gun of the electric arc furnace begins to descend and spray the mixed material. The high temperature generated by the electric arc melts the powdered mixed material instantly and causes a reduction reaction, forming a molten pool inside the furnace for continuous smelting. Step 4: After smelting, remove the top layer of slag and then tap the steel.

[0010] Preferably, in step one, the drying temperature is 120-150°C, and the (nickel) copper powder tailings are dried until the moisture content is 4-8%.

[0011] Preferably, in step two, the slag-forming agent is lime and fluorite.

[0012] Preferably, in step two, the reducing agent is at least one of coal pellets, carbon powder, and coke powder.

[0013] Preferably, in step two, the amount of lime added is adjusted to control the binary basicity of the slag, CaO / SiO2, to be 1.0~1.8. Preferably, in step two, the mass percentage of each raw material is: (nickel) copper powder tailings 60%-80%, lime 20%-35%, fluorite 1%-3%, and reducing agent 2%-5%.

[0014] Preferably, in step three, the air pressure inside the spray gun is 0.4-0.6 MPa.

[0015] Preferably, in step three, the feeding and powder spraying speed of the mixture is 1.2-2.0 t / min.

[0016] Preferably, in step three, the molten pool temperature is 1500-1630℃ and the melting time is 40-60 min.

[0017] Preferably, in step three, the remaining lime is added in batches during the smelting process to form slag, and after the slag foams and stabilizes, the carbon content of iron and alloys is reduced to 1-3%. Preferably, in step four, after the smelting is completed, the AC electric arc furnace is tilted to (-15)-(-10)° to remove the upper layer of slag, and 1 / 3-1 / 2 of the molten pool is retained for the next hot start-up by using slag retention operation; then the electric arc furnace is tilted to 25°-40° to tap steel.

[0018] Preferably, in step two, at least one of low-grade vanadium slag, titanium slag, manganese slag, niobium slag, and rare earth slag is added to form a high-value composite iron-based alloy.

[0019] The present invention has the following beneficial effects: This invention provides a method for flash iron extraction and alloying using (nickel) copper powder tailings. It abandons the lengthy process of traditional "ore dressing-pelletizing-blast furnace ironmaking" and directly processes (nickel) copper powder tailings with flash melting at the top of an electric arc furnace. The high temperature of the electric arc causes the powder material to melt instantly and be rapidly reduced, fully releasing valuable iron elements. The iron recovery rate is as high as 95% or more. There is no need for complex pretreatment such as agglomeration. The smelting time is greatly shortened, the processing efficiency is significantly improved, and the cost of industrial application is greatly reduced.

[0020] It eliminates the need for large amounts of scrap steel, reducing reliance on high-quality scrap steel and significantly lowering raw material costs. By adopting furnace gas internal circulation reuse and slag retention hot start-up processes, it recovers waste heat in the furnace, reduces inert gas consumption, and achieves higher energy utilization.

[0021] It can be synergistically incorporated with various industrial solid wastes such as low-grade vanadium slag, titanium slag, and manganese slag to prepare high-value-added composite iron-based alloys such as ferrovanadium and ferromanganese in situ, realizing the synergistic utilization of multiple solid wastes and product diversification, and solving the problems of single products and low added value in traditional processes. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] The (nickel) copper powder tailings used in the following examples were taken from a large copper smelter in China, and the typical composition is shown in Table 1.

[0024] Table 1 Typical chemical composition of (nickel) copper powder tailings (mass percentage, %) Example 1

[0025] The iron content of the (nickel) copper powder tailings is 40.2%. Step 1: Solid waste pretreatment The (nickel) copper powder tailings are dried to a moisture content of 5% using a waste heat treatment device and then loaded into a raw material tank.

[0026] Step 2, Ingredients: Take 70% (nickel) copper powder tailings, 26.5% lime, 1.5% fluorite, and 2% coke powder by mass ratio, mix them evenly, and sieve through a 325-mesh sieve to control the binary basicity of the slag CaO / SiO2 = 1.4.

[0027] Step 3: Flash melting in an AC electric arc furnace: The mixture was injected into a 10t AC electric arc furnace at a rate of 1.6t / min, with the power supply controlled at 700kVA / t, arc voltage at 380V, working current at 11kA, molten pool temperature at 1600℃, and melting time at 40min. After the slag foams and stabilizes, use a fixed tool to take a 300-500g slag sample and test the binary alkalinity in the slag sample. If it is lower than the expected index, add limestone and let it stand and melt completely.

[0028] Step 4: Steel casting: Tilting the AC electric arc furnace to (-15) - (-10)° removes the upper layer of slag, leaving 1 / 3 of the molten pool for the next heat start-up; then, the furnace is tilted to 25°-40° for tapping. The chemical composition of the obtained molten steel is shown in Table 2, with an iron content of 95.8% and an iron recovery rate of 95.1%. Example 2

[0029] The iron content of the (nickel) copper powder tailings is 42.8%.

[0030] Step 1: Solid waste pretreatment (Nickel) copper powder tailings and low-grade vanadium slag are dried to a moisture content of 4%.

[0031] Step 2, Ingredients: Take 60% (nickel) copper powder tailings, 5% low-grade vanadium slag (vanadium content in slag is 8%), 30% lime, 2% fluorite, and 3% coke powder by mass ratio, mix them evenly, and sieve through a 325-mesh sieve to control the binary basicity of the slag CaO / SiO2=1.2.

[0032] Step 3: Flash melting in an AC electric arc furnace: The mixture was injected into a 10t AC electric arc furnace at a rate of 1.4t / min, with the power supply controlled at 650kVA / t, arc voltage at 360V, working current at 10.5kA, molten pool temperature at 1620℃, and melting time at 35min.

[0033] Step 4: Tapping the steel. Tilting the AC electric arc furnace to (-15)-(-10)° removes the upper layer of slag, leaving 1 / 3 of the molten pool for the next hot start-up; then the electric arc furnace is tilted to 25°-40° for tapping.

[0034] The chemical composition of the obtained molten steel is shown in Table 2. The iron content is 95.6%, the vanadium content is 1.7%, and the iron recovery rate is 95.7%. Example 3

[0035] The iron content of the (nickel) copper powder tailings is 39.5%.

[0036] Step 1: Solid waste pretreatment The (nickel) copper powder tailings were dried to a moisture content of 6%.

[0037] Step 2, Ingredients: Take 65% (nickel) copper powder tailings, 10% low-grade vanadium slag (7% V content in slag), 21.5% lime, 1.5% fluorite, and 2% coke powder by mass ratio, mix them evenly, and sieve through a 325-mesh sieve to control the binary basicity of the slag CaO / SiO2 = 1.1.

[0038] Step 3: Flash melting in an AC electric arc furnace: The mixture was injected into a 10t AC electric arc furnace at a rate of 1.8t / min, with the power supply controlled at 750kVA / t, arc voltage at 390V, working current at 11.5kA, molten pool temperature at 1650℃, and melting time at 30min.

[0039] Step 4: Tapping the steel. Tilting the AC electric arc furnace to (-15)-(-10)° removes the upper layer of slag, leaving 1 / 2 of the molten pool for the next hot start-up; then the electric arc furnace is tilted to 25°-40° for tapping.

[0040] The chemical composition of the obtained molten steel is shown in Table 2. The iron content is 95.4%, the vanadium content is 2.7%, and the iron recovery rate is 95.5%.

[0041] Comparative Example Using the same raw materials in a traditional AC electric arc furnace steelmaking process: 1. Grind the (nickel) copper powder tailings to -200 mesh (90% of the powder) to form pellets with a diameter of 10-15mm, and dry them until the moisture content is ≤1%; 2. Add 60% pellets and 40% scrap steel to a 50t AC electric arc furnace by mass ratio, control the power supply to 800kVA / t, and the melting time to 45min; 3. The steel produced has an iron content of 94.8% and an iron recovery rate of 84.2%. The cost per ton of steel is 280 yuan higher than that of the previous example.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for using (nickel) copper powder tailings for electric arc furnace flash iron and alloy extraction, characterized by, Includes the following steps: Step 1: Dry the (nickel) copper powder tailings to control the moisture content of the (nickel) copper powder tailings; Step 2: Mix the materials obtained in Step 1, the slag-forming agent, and the reducing agent evenly, and sieve through a 325-mesh screen; Step 3: The electric arc furnace is powered for smelting. The top spray gun of the electric arc furnace begins to descend and spray the mixed material. The high temperature generated by the electric arc melts the powdered mixed material instantly and causes a reduction reaction, forming a molten pool inside the furnace for continuous smelting. Step 4: After smelting, remove the top layer of slag and then tap the steel.

2. The method for rapid iron and alloy extraction in an electric arc furnace using (nickel) copper powder tailings as described in claim 1, characterized in that, In step one, the drying temperature is 120-150℃, and the (nickel) copper powder tailings are dried until the moisture content is 4-8%.

3. The method for rapid iron and alloy extraction in an electric arc furnace using (nickel) copper powder tailings as described in claim 1, characterized in that... In step two, the slag-forming agents are lime and fluorite.

4. The method for rapid iron and alloy extraction in an electric arc furnace using (nickel) copper powder tailings as described in claim 1, characterized in that, In step two, the reducing agent is at least one of coal briquettes, carbon powder, and coke powder.

5. The method for rapid iron and alloy extraction in an electric arc furnace using (nickel) copper powder tailings as described in claim 1, characterized in that, In step two, the amount of lime added is adjusted to control the binary basicity of the slag, CaO / SiO2, to be 1.0~1.

8.

6. The method for rapid iron and alloy extraction in an electric arc furnace using (nickel) copper powder tailings as described in claim 1, characterized in that, In step two, the mass percentage of each raw material is as follows: (nickel) copper powder tailings 60%-80%, lime 20%-35%, fluorite 1%-3%, and reducing agent 2%-5%.

7. The method for rapid iron and alloy extraction in an electric arc furnace using (nickel) copper powder tailings as described in claim 1, characterized in that, In step three, the air pressure inside the spray gun is 0.4-0.6 MPa.

8. The method for rapid iron and alloy extraction in an electric arc furnace using (nickel) copper powder tailings as described in claim 1, characterized in that, In step four, after the melting is completed, the AC electric arc furnace is tilted to (-15)-(-10)° to remove the upper layer of slag, and 1 / 3-1 / 2 of the molten pool is retained for the hot start of the next furnace using the slag retention operation; then the electric arc furnace is tilted to 25°-40° to tap the steel.

9. The method for rapid iron and alloy extraction in an electric arc furnace using (nickel) copper powder tailings as described in claim 1, characterized in that... In step two, at least one of the following is added: low-grade vanadium slag, titanium slag, manganese slag, niobium slag, and rare earth slag.

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