A process for producing nickel-iron alloy by smelting laterite nickel ore using the RKEF process.

Abstract

This invention belongs to the field of pyrometallurgical technology, specifically relating to a process for producing nickel-iron alloy by smelting laterite nickel ore using the RKEF process. The process includes the following steps: (1) preparing laterite nickel ore powder, semi-coke powder, and quicklime powder; (2) mixing laterite nickel ore powder and quicklime powder evenly to obtain mixed powder A; (3) mixing mixed powder A evenly with the semi-coke powder obtained in step (1) to obtain mixed powder B; (4) adding composite additives to mixed powder B to obtain mixed powder C; (5) calcining mixed powder C obtained in step (4); (6) cooling the calcined product with the furnace, crushing and magnetically separating it to obtain the main product nickel-iron alloy and the by-product slag. This invention reduces the smelting temperature of the electric furnace by reducing the slag viscosity and melting temperature, thereby reducing energy consumption, saving energy consumption, reducing production costs, and improving the nickel reduction rate.

Description

Technical Field

[0001] This invention belongs to the field of pyrometallurgical technology, specifically relating to a process for producing nickel-iron alloy by smelting laterite nickel ore using the RKEF process. Background Technology

[0002] Nickel is an important metallic element, frequently used in the production of stainless steel and high-performance alloys due to its excellent physical and chemical properties. Furthermore, nickel is widely used in the field of power batteries for new energy vehicles, earning it the title of "white oil of the 21st century." It is a crucial material foundation for the development of the new energy industry and determines the lifeline of the new energy industry chain. With the rapid growth in global demand for nickel resources, approximately 28% of the world's exploitable nickel resources are sulfide nickel ore, while the remaining 72% are laterite nickel ore. Due to its abundant resources, laterite nickel ore has become the main raw material for nickel production.

[0003] Currently, the rotary kiln-electric furnace (RKEF) smelting technology is the mainstream process for producing high-nickel ferroalloys from laterite nickel ore using pyrometallurgical methods. The process flow is as follows: the laterite nickel ore is first dehydrated in a drying kiln; then, it is pre-reduced by roasting at 850-1000℃ in a rotary kiln to remove crystal water; the high-temperature charge is then directly fed into an electric furnace for reduction smelting at 1500-1600℃ to produce ferroalloys. This process has advantages such as high ferroalloy grade, low levels of harmful elements, strong raw material adaptability, high production efficiency, and mature technology. However, it also has problems such as high energy consumption, large slag volume, and severe dust pollution. Electricity consumption in the electric furnace smelting process accounts for more than 50% of the operating cost. Laterite nickel ore has a very low nickel grade (generally less than 2.5%), resulting in a large slag volume during electric furnace smelting, with a slag-to-gold ratio (mass ratio) reaching 5:1 or even higher. The key task of an electric arc furnace is to achieve effective slag-gold separation, and good slag fluidity is essential for this separation. Therefore, obtaining high-temperature, highly fluid slag requires a significant amount of electrical energy. Reducing energy consumption is therefore a crucial way to lower production costs.

[0004] Chinese Patent CN101413055B discloses a process for directly producing nickel-iron alloy powder from laterite nickel ore. This invention involves crushing and grinding the laterite nickel ore, adding additives, mixing and agglomerating, drying the agglomerates, and then using coal as a reducing agent at a certain temperature to reduce nickel and iron to metallic nickel and metallic iron. The reduction products are then crushed and ground again, and separated using a weak magnetic separation method to obtain magnetic products.

[0005] It is a nickel-iron alloy powder.

[0006] Chinese Patent CN108559838B describes a method for preparing nickel-iron alloys by mixed smelting of laterite nickel ore. This invention uses different types of laterite nickel ore as raw materials to achieve comprehensive utilization of siliceous magnesium type and limonite type laterite nickel ore, and effectively prepares nickel-iron alloys from the two types of laterite nickel ore for stainless steel smelting.

[0007] However, the nickel reduction rate in existing technologies is generally low, typically around 92%. Therefore, the purpose of this application is to reduce energy consumption while increasing the nickel reduction rate. Summary of the Invention

[0008] The purpose of this invention is to provide a process for producing nickel-iron alloy by smelting laterite nickel ore using the RKEF process.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A process for producing nickel-iron alloy by smelting laterite nickel ore using the RKEF process includes the following steps:

[0011] (1) The laterite nickel ore, semi-coke and industrial lime are crushed separately and screened to obtain laterite nickel ore powder, semi-coke powder and quicklime powder respectively;

[0012] (2) Mix the laterite nickel ore powder and quicklime powder obtained in step (1) evenly to obtain mixed powder A;

[0013] (3) Mix the mixed powder A obtained in step (2) with the semi-coke powder obtained in step (1) evenly to obtain mixed powder B;

[0014] (4) Add composite additives to the mixed powder B obtained in step (3) to obtain mixed powder C;

[0015] (5) The mixed powder C obtained in step (4) is calcined, and argon gas is introduced as a protective gas during the process;

[0016] (6) After roasting, the product is cooled in the furnace, crushed and magnetically separated to obtain the main product nickel-iron alloy and the by-product slag.

[0017] Preferably, in step (2), quicklime powder accounts for 5-20% of the mass of mixed powder A.

[0018] Preferably, in step (3), the semi-coke accounts for 3.5%-6.5% of the mass of the mixed powder B.

[0019] Preferably, the composite additives include graphite powder, fluorite, and alumina.

[0020] Preferably, the graphite powder has an average specific surface area of ​​20~30m² / g, a particle size D50 of 20~50μm, and is added at a rate of 0.8%~1.2% of the mass of the mixed powder B.

[0021] Preferably, the particle size D50 of fluorite is 50~80μm, the free CaO content in fluorite is ≤0.8wt%, and the amount of fluorite added accounts for 1.0%~1.5% of the mass of mixed powder B.

[0022] Preferably, the alumina is α-Al2O3, and the amount of alumina added makes the mass ratio of Al2O3 / SiO2 in the slag 0.3~0.4.

[0023] Preferably, the calcination conditions are as follows: the heating rate is 10-12℃ / min in the 0-800℃ stage, the heating rate is 6-8℃ / min in the 800-1300℃ stage, the heating rate is 3-5℃ / min in the 1300-1600℃ stage, and the temperature is held at 1600℃ for 1-1.2 hours.

[0024] Preferably, argon gas is introduced as a protective gas during the roasting process.

[0025] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0026] 1. This invention reduces the smelting temperature of the electric furnace by lowering the viscosity and melting temperature of the slag, thereby reducing energy consumption, saving energy, and reducing production costs.

[0027] 2. This invention, by adding an appropriate amount of industrial lime to nickel ore, can effectively reduce the melting point and viscosity of the ore, thereby significantly reducing power consumption during the smelting process and lowering production costs. Simultaneously, under relatively low smelting temperatures, precise control of the carbon content can promote effective separation of slag and iron during electric furnace smelting, thereby improving nickel recovery and achieving efficient resource utilization.

[0028] 3. This invention significantly improves the overall efficiency of nickel-iron alloy preparation by forming a synergistic additive system of graphite powder, fluorite, and α-Al2O3. Graphite powder enhances the microscopic reducing atmosphere with its high specific surface area, forming a macroscopic and microscopic reduction synergy with semi-coke; fluorite efficiently destroys the silicon-oxygen structure of slag, reducing viscosity and melting point, and facilitating the separation of nickel-iron particles; α-Al2O3 precisely controls the Al2O3 / SiO2 ratio of slag, ensuring system stability; the three synergistically compensate for the shortcomings of single additives, enabling the nickel reduction rate to exceed 95%, while reducing roasting energy consumption, reducing slag agglomeration, and improving the grade of nickel-iron alloy and magnetic separation recovery rate. Attached Figure Description

[0029] Figure 1 The melting point is the slag by-product of Examples 1-8 and Comparative Examples 1-5. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] All raw materials used in the following embodiments of the present invention are commercially available products:

[0032] The main components of laterite nickel ore include (by mass percentage): 1.71% Ni, 20.76% TFe (total iron), 24.20% MgO, 1.03% CaO, 34.22% SiO2, 2.63% Al2O3, and 1.28% Cr2O3.

[0033] Semi-coke: Particle size less than 5mm, carbon content 87wt%.

[0034] Example 1

[0035] This embodiment provides a process for producing nickel-iron alloy by smelting laterite nickel ore using the RKEF process, including the following steps:

[0036] (1) The laterite nickel ore, semi-coke and industrial lime are crushed separately and screened to a particle size of ≤2mm to obtain laterite nickel ore powder, semi-coke powder and quicklime powder respectively;

[0037] (2) The laterite nickel ore powder and quicklime powder obtained in step (1) are mixed evenly at a mass ratio of 95:5, with a total weight of 144g, to obtain mixed powder A;

[0038] (3) Mix the mixed powder A obtained in step (2) with the semi-coke powder obtained in step (1) at a mass ratio of 96:4, and the total weight is 150g to obtain mixed powder B;

[0039] (4) Add composite additives to the mixed powder B obtained in step (3) to obtain mixed powder C; the composite additives include graphite powder, fluorite and alumina. The average specific surface area of ​​graphite powder is 26 m² / g, the particle size D50 is 38 μm, and the amount added accounts for 0.9% of the mass of mixed powder B; the particle size D50 of fluorite is 67 μm, the free CaO content in fluorite is 0.6 wt%, and the amount added of fluorite accounts for 1.2% of the mass of mixed powder B; the alumina is α-Al2O3, and the amount of alumina added makes the final Al2O3 / SiO2 mass ratio of the slag 0.37;

[0040] (5) The mixed powder C obtained in step (4) is calcined. The calcination conditions are: the heating rate is 10℃ / min in the 0-800℃ stage, 6℃ / min in the 800-1300℃ stage, 5℃ / min in the 1300-1600℃ stage, and the temperature is held for 1 hour after reaching 1600℃. Argon gas is introduced as a protective gas during the process.

[0041] (6) After roasting, the product is cooled in the furnace, crushed and magnetically separated to obtain the main product nickel-iron alloy and the by-product slag.

[0042] Example 2

[0043] The difference between this embodiment and embodiment 1 is that: (2) the laterite nickel ore powder and quicklime powder obtained in step (1) are mixed evenly at a mass ratio of 90:10, with a total weight of 144g.

[0044] Example 3

[0045] The difference between this embodiment and embodiment 1 is that: (2) the laterite nickel ore powder and quicklime powder obtained in step (1) are mixed evenly at a mass ratio of 85:15, with a total weight of 144g.

[0046] Example 4

[0047] The difference between this embodiment and embodiment 1 is that: (2) the laterite nickel ore powder and quicklime powder obtained in step (1) are mixed evenly at a mass ratio of 80:20, with a total weight of 144g.

[0048] Example 5

[0049] The difference between this embodiment and embodiment 2 is that: (2) the laterite nickel ore powder and quicklime powder obtained in step (1) are mixed evenly at a mass ratio of 90:10, and the total weight is 144.75g; (3) the mixed powder obtained in step (2) is mixed evenly with the semi-coke obtained in step (1) at a mass ratio of 96.5:3.5, and the total weight is 150g.

[0050] Example 6

[0051] The difference between this embodiment and embodiment 2 is that: (2) the laterite nickel ore powder and quicklime powder obtained in step (1) are mixed evenly at a mass ratio of 90:10, with a total weight of 140.25g; (3) the mixed powder obtained in step (2) is mixed evenly with the semi-coke obtained in step (1) at a mass ratio of 93.5:6.5, with a total weight of 150g.

[0052] Example 7

[0053] The difference between this embodiment and embodiment 6 is that: (5) the mixed powder C obtained in step (4) is calcined, the heating regime is 10℃ / min in the 0-800℃ stage, 6℃ / min in the 800-1300℃ stage, 5℃ / min in the 1300-1600℃ stage, and held at 1550℃ for 1 hour, and argon gas is introduced as a protective gas during the process.

[0054] Example 8

[0055] The difference between this embodiment and embodiment 6 is that: (5) the mixed powder C obtained in step (4) is calcined, the heating regime is 10℃ / min in the 0-800℃ stage, 6℃ / min in the 800-1300℃ stage, 5℃ / min in the 1300-1600℃ stage, and held at 1650℃ for 1 hour, and argon gas is introduced as a protective gas during the process.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 1 is that: (2) the laterite nickel ore powder and quicklime powder obtained in step (1) are mixed evenly at a mass ratio of 100:0, with a total weight of 144g;

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 1 is that: (2) the laterite nickel ore powder and quicklime powder obtained in step (1) are mixed evenly at a mass ratio of 75:25, with a total weight of 144g;

[0060] Comparative Example 3

[0061] The difference between this comparative example and Example 2 is that: (2) the laterite nickel ore powder and quicklime powder obtained in step (1) are mixed evenly at a mass ratio of 90:10, with a total weight of 145.5g; (3) the mixed powder obtained in step (2) is mixed evenly with the semi-coke obtained in step (1) at a mass ratio of 97:3, with a total weight of 150g.

[0062] Comparative Example 4

[0063] The difference between this comparative example and Example 2 is that: (2) the laterite nickel ore powder and quicklime powder obtained in step (1) are mixed evenly at a mass ratio of 90:10, with a total weight of 139.5g; (3) the mixed powder obtained in step (2) is mixed evenly with the semi-coke obtained in step (1) at a mass ratio of 93:7, with a total weight of 150g.

[0064] Comparative Example 5

[0065] The difference between this comparative example and Example 6 is that: (5) the mixed powder C obtained in step (4) is calcined, the heating regime is 10℃ / min in the 0-800℃ stage, 6℃ / min in the 800-1300℃ stage, 5℃ / min in the 1300-1600℃ stage, and held at 1500℃ for 1 hour, and argon gas is introduced as a protective gas during the process.

[0066] Comparative Example 6

[0067] The difference between this comparative example and Example 7 is that the composite additive includes fluorite and alumina. The particle size D50 of the fluorite is 67 μm, the free CaO content in the fluorite is 0.6 wt%, and the amount of fluorite added accounts for 1.2% of the mass of the mixed powder B. The alumina is α-Al2O3, and the amount of alumina added makes the final Al2O3 / SiO2 ratio of the slag = 0.37.

[0068] Comparative Example 7

[0069] The difference between this comparative example and Example 7 is that the average specific surface area of ​​the graphite powder is 10 m² / g and D50 = 100 μm.

[0070] Comparative Example 8

[0071] The difference between this comparative example and Example 7 is that the key parameters of fluorite do not meet the standard: the free CaO content in fluorite is 2.0 wt%.

[0072] Comparative Example 9

[0073] The difference between this comparative example and Example 7 is that α-alumina is replaced with γ-Al2O3, which makes the final Al2O3 / SiO2 mass ratio of the slag 0.5.

[0074] Comparative Example 10

[0075] The difference between this comparative example and Example 7 is as follows: Referring to CN102643976B, a composite additive for producing nickel-iron particles from laterite nickel ore and its usage method, the composite additive includes the following components by mass percentage: quicklime 50%, fluorite 32%, soda ash 15% and boric acid 3%, and the amount of composite additive added accounts for 7% of the mass of mixed powder B.

[0076] Performance testing

[0077] The nickel content in laterite nickel ore powder and by-product slag from Examples 1-8 and Comparative Examples 1-10 was detected using chemical analysis. The reduction rate of nickel was then calculated using the formula: Reduction rate = (Final nickel content / Initial nickel content) × 100%. The results are shown in Table 1.

[0078] According to the metallurgical industry standard YB / T186-2014, the melting point of the by-product slag in Examples 1-8 and Comparative Examples 1-5 was determined using an LZ-Ⅲ type slag melting temperature characteristic tester. The results are as follows: Figure 1 As shown.

[0079] Table 1 Experimental parameters and test results

[0080]

[0081] A comprehensive analysis of Examples 1-4 and Comparative Examples 1-2 reveals that controlling the CaO content in the slag between 5-20% not only lowers the slag's melting point and achieves energy savings, but also increases the nickel reduction rate to over 90%. When the CaO content deviates from this range, the slag's melting point increases, its fluidity decreases, leading to increased energy consumption and a reduced nickel reduction rate.

[0082] Comparative results from Examples 2, 5-6, and 3-4 show that when the carbon content is below 3.5%, the nickel reduction rate is less than 90%, indicating an incomplete reduction reaction. While a lower melting point and higher nickel reduction rate can be maintained when the carbon content exceeds 7%, the values ​​are close to those at a carbon content of 6.5%, suggesting that further increasing the carbon content has no significant effect on improving the nickel reduction rate. Therefore, considering both reduction efficiency and economics, the appropriate carbon content should be controlled between 3.5% and 6.5%.

[0083] Comparative Examples 7-8 and Comparative Example 5 show that the nickel reduction rate decreases significantly when the smelting temperature is below 1550°C. Conversely, energy consumption increases sharply when the smelting temperature is above 1650°C. Therefore, the smelting temperature should be controlled between 1550-1650°C to ensure a high nickel reduction rate while consuming relatively low energy.

[0084] Comparative Example 6 shows that the absence of graphite powder reduces the intensity of the reducing atmosphere and prevents synergy with macroscopic reduction (semi-coke) and microscopic reduction, resulting in insufficient local reduction. Although fluorite and Al2O3 can still regulate the fluidity of slag, the reduction bottleneck leads to a decrease in the reduction rate.

[0085] Comparative Example 7 shows that the graphite powder has insufficient specific surface area, resulting in a reduced contact area with the mineral powder and a decrease in the efficiency of the interfacial reduction reaction; the particle size is too large, resulting in poor dispersibility and uneven local reduction atmosphere.

[0086] As shown in Comparative Example 8, excessive free CaO in fluorite leads to an excessively high CaO / SiO2 ratio in the slag, causing the slag to become "over-alkalized" and agglomerate, resulting in poor fluidity and a decrease in the reduction rate.

[0087] As shown in Comparative Example 9, γ-Al2O3 is easily converted to α-Al2O3 at high temperatures, accompanied by volume shrinkage, which leads to unstable slag structure, excessive Al2O3 / SiO2 ratio, and destruction of the stable structure of CaO-SiO2-Al2O3-MgO quaternary slag. This results in a slight increase in slag viscosity, a decrease in the agglomeration effect of nickel-iron particles, and a decrease in local fluidity and reduction rate.

[0088] As can be seen from Comparative Example 10, the composite additive of the present invention is superior to the product of the prior art.

[0089] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for producing nickel-iron alloy by smelting laterite nickel ore using the RKEF process, characterized in that, Includes the following steps: (1) The laterite nickel ore, semi-coke and industrial lime are crushed separately and screened to obtain laterite nickel ore powder, semi-coke powder and quicklime powder respectively; (2) Mix the laterite nickel ore powder and quicklime powder obtained in step (1) evenly to obtain mixed powder A; (3) Mix the mixed powder A obtained in step (2) with the semi-coke powder obtained in step (1) evenly to obtain mixed powder B; (4) Add composite additives to the mixed powder B obtained in step (3) to obtain mixed powder C; the composite additives include graphite powder, fluorite and alumina; The graphite powder has an average specific surface area of ​​20-30 m² / g and a particle size D50 of 20-50 μm; the amount of graphite powder added accounts for 0.8%-1.2% of the mass of mixed powder B; the fluorite has a particle size D50 of 50-80 μm and a free CaO content ≤0.8 wt%; the amount of fluorite added accounts for 1.0%-1.5% of the mass of mixed powder B; the alumina is α-Al₂O₃, and the amount of alumina added makes the Al₂O₃ / SiO₂ mass ratio in the slag 0.3-0.4; (5) The mixed powder C obtained in step (4) is calcined, and argon gas is introduced as a protective gas during the process; (6) After roasting, the product is cooled in the furnace, crushed and magnetically separated to obtain the main product nickel-iron alloy and the by-product slag.

2. The process for producing nickel-iron alloy by smelting laterite nickel ore using the RKEF process according to claim 1, characterized in that, In step (2), quicklime powder accounts for 5-20% of the mass of mixed powder A.

3. The process for producing nickel-iron alloy by smelting laterite nickel ore using the RKEF process according to claim 1, characterized in that, In step (3), the semi-coke accounts for 3.5%-6.5% of the mass of the mixed powder B.

4. The process for producing nickel-iron alloy by smelting laterite nickel ore using the RKEF process according to claim 1, characterized in that, The calcination conditions are as follows: the heating rate is 10-12℃ / min in the 0-800℃ stage, 6-8℃ / min in the 800-1300℃ stage, and 3-5℃ / min in the 1300-1600℃ stage. After reaching 1600℃, the temperature is maintained for 1-1.2 hours.

5. The process for producing nickel-iron alloy by smelting laterite nickel ore using the RKEF process according to claim 1, characterized in that, Argon gas is introduced as a protective gas during the roasting process.

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