A method for separating nickel and iron by chlorination roasting of nickel and iron alloy

Abstract

The present invention discloses a method for separating nickel and iron from a nickel-iron alloy by chlorination roasting: (1) placing the nickel-iron alloy in a roasting furnace; (2) introducing a gaseous chlorinating agent into the roasting furnace for staged roasting to obtain roasting slag and a roasting gas phase; wherein the gaseous chlorinating agent is a mixture of chlorine and gaseous ferric chloride; and (3) condensing the roasting gas phase obtained in step (2) in stages to obtain solid ferric chloride and liquid silicon tetrachloride, respectively. The present invention controls the composition of the chlorinating agent during the chlorination roasting process to achieve selective and directional volatilization of iron into the gas phase while preventing nickel from being chlorinated. Thus, nickel and iron in the nickel-iron alloy can be separated in a single step, and the process flow is short.

Description

Technical Field

[0001] The invention belongs to the field of resource utilization, and in particular relates to a method for separating nickel and iron by chlorination roasting of nickel-iron alloy. Background Art

[0002] Nickel, known as the "vitamin of industry," is widely used in sectors such as industrial machinery manufacturing, aerospace, and nuclear reactors. It is also a key raw material for a variety of batteries, including nickel-metal hydride (NiMH) batteries, nickel-cadmium (NiCd) batteries, and ternary lithium-ion batteries. It is widely used in portable devices, electric vehicles, and energy storage batteries. Currently, 70% of nickel consumption is used in stainless steel, 16% in alloys other than stainless steel, and 8% in protective and decorative coatings. Battery consumption accounts for only 5%. However, with the rapid development of the global electric vehicle industry, the share of nickel in stainless steel is expected to decline from 70% to 52% by 2030, while the share of nickel in batteries will increase from 5% to 31%. Therefore, supplying ferronickel (FeNickel) raw materials derived from mature laterite nickel ore smelting processes to industries other than stainless steel, such as the electric vehicle industry, will be crucial for ensuring a balanced supply and demand for nickel across various sectors. However, the iron content of ferronickel alloys is very high, necessitating the development of efficient iron separation processes to produce nickel-rich powder.

[0003] Patent application number CN202310067518.6 discloses a method for preparing battery-grade iron phosphate using nickel-iron alloy, which comprises heating and acid-dissolving the nickel-iron alloy, and then reacting the leachate with a complexing agent, iron phosphate seeds, phosphoric acid, and an oxidant to obtain a dihydrate iron phosphate precipitate, which is then washed with hot water and finally mixed with a reducing agent for solid-phase oxidation reaction to prepare battery-grade iron phosphate; by adding a complexing agent, it can form [Ni(NH3)4] with nickel ions. 2+ The group effectively removes nickel ions, prevents nickel ions from entering the iron phosphate lattice during the preparation of iron phosphate, and reduces the possibility of nickel ions being adsorbed by iron phosphate. Patent application number CN202211585186.2 discloses a method for jointly treating laterite nickel ore and nickel-iron alloy and recovering nickel and iron. The method utilizes the high acid and Fe-rich atmospheric pressure leaching solution of laterite nickel ore. 3+ The nickel-iron alloy is treated by using the nickel-iron to neutralize the residual acid in the leachate, and the residual acid and Fe in the leachate are used to 3+The strong oxidizing property of nickel-iron promotes the dissolution of nickel-iron, achieving efficient recovery of nickel and iron, and ultimately obtaining iron phosphate and battery-grade nickel sulfate. The patent application with patent application number CN202211380295.0 discloses a method for extracting iron from nickel-iron alloy and preparing hydrogen peroxide, which uses sulfuric acid to leach the nickel-iron alloy, collects the tail gas generated by the heating reaction of the slurry during the leaching process, and performs desulfurization and purification operations to recover hydrogen and purify it, and then uses it to prepare hydrogen peroxide. The patent application with patent application number CN202211252938.3 discloses a method for preparing nickel sulfate from nickel-iron alloy powder, which mixes the nickel-iron alloy powder with concentrated sulfuric acid, roasts it twice, grinds the roasted material, adds water to the ground material for leaching, separates the liquid and solid, and obtains nickel sulfate solution and iron slag. This method can obtain nickel sulfate solution by mixing acid, roasting, and then leaching in water. The patent application with patent number CN202211191569.1 discloses a method for producing battery-grade iron phosphate using an iron-based nickel-containing alloy, which mainly includes acid leaching nickel-iron alloy powder to obtain a leachate, and after impurities are removed, an iron-containing solution is obtained for preparing iron phosphate. The patent application with patent number CN202211126429.6 discloses a method and application for preparing lithium iron phosphate from nickel-iron alloy. The nickel-iron alloy is leached by combining an organic acid and an oxidant, and then the iron salt and nickel salt in the nickel-iron alloy are precipitated step by step by using an organic precipitant. The iron salt precipitate can be directly used to prepare lithium iron phosphate, and the nickel salt precipitate can be used as a nickel source for the subsequent preparation of ternary positive electrode materials.

[0004] It can be seen that the above-mentioned method for high-value utilization of nickel-iron alloy mainly uses reagents to wet-leach the nickel-iron alloy to destroy the dense structure of the nickel-iron alloy, while allowing the nickel, iron, etc. in the alloy to enter the solution, and then the solution is purified and partially extracted to obtain valuable metals. When the above-mentioned method leaches the nickel-iron alloy, both nickel and iron enter the leachate, which is not selective, resulting in subsequent lengthy extraction processes such as impurity removal and separation. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a method for separating nickel and iron by chlorination roasting of nickel-iron alloy, so as to solve the technical problems such as the difficulty in separating nickel and iron, the long process flow and the complex process in the current high-value utilization of nickel-iron alloy.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0007] A method for separating nickel iron by chlorination roasting of nickel iron alloy comprises the following steps:

[0008] (1) placing nickel-iron alloy in a roasting furnace;

[0009] (2) introducing a gaseous chlorinating agent into a roasting furnace for staged roasting to obtain roasting slag and roasting gas phase; wherein the gaseous chlorinating agent is a mixture of chlorine and gaseous ferric chloride;

[0010] (3) The roasting gas phase obtained in step (2) is condensed in sections to obtain solid ferric chloride and liquid silicon tetrachloride respectively.

[0011] In the above-mentioned method for separating nickel iron by chlorination roasting of nickel iron alloy, preferably, in step (2), the staged roasting is divided into two stages, wherein the roasting temperature of the first stage is 550-690°C and the roasting time is 5-15 minutes; the roasting temperature of the second stage is 550-750°C and the roasting time is 30-180 minutes.

[0012] In the above-mentioned method for separating nickel iron by chlorination roasting of nickel iron alloy, preferably, in step (2), during the first roasting process, the molar ratio of chlorine in the gaseous chlorinating agent to iron in the nickel iron alloy is 1:5 to 1:10.

[0013] In the above-mentioned method for separating nickel iron by chlorination roasting of nickel iron alloy, preferably, in step (2), during the second stage roasting process, the molar ratio of chlorine in the gaseous chlorinating agent to iron in the nickel iron alloy is 3:1 to 60:1.

[0014] In the above-mentioned method for separating nickel iron by chlorination roasting of nickel iron alloy, preferably, in step (2), during the first roasting process, the molar ratio of chlorine gas in the gaseous chlorinating agent to gaseous ferric chloride is not higher than 0.5.

[0015] In the above-mentioned method for separating nickel iron by chlorination roasting of nickel iron alloy, preferably, in step (2), during the second stage roasting process, the molar ratio of chlorine gas to gaseous ferric chloride in the gaseous chlorinating agent is 8 to 15.

[0016] In the above-mentioned method for separating nickel iron by chlorination roasting of nickel iron alloy, preferably, in step (3), the staged condensation means that the roasting gas phase is first condensed at 80-260°C for one stage and then condensed at 25-30°C for a second stage.

[0017] In the above-mentioned method for separating nickel iron by chlorination roasting of nickel iron alloy, preferably, the roasting slag obtained in step (2) is ball milled to obtain nickel-rich powder.

[0018] In the above-mentioned method for separating nickel iron by chlorination roasting of nickel iron alloy, preferably, in step (1), the particle size of the nickel iron alloy is 0.3 to 4 cm.

[0019] In the above-mentioned method for separating nickel iron by chlorination roasting of nickel iron alloy, preferably, in step (2), argon gas is used to exhaust the air in the roasting furnace before roasting.

[0020] The present invention realizes the selective directional volatilization of iron by controlling the composition and roasting temperature of the chlorinating agent in the chlorination roasting process, while preventing nickel from being chlorinated. Its main principle is to preferentially form a ferrous chloride solid film or a ferrous chloride liquid film on the surface of the nickel-iron alloy by regulating the composition of the chlorinating agent. The solid film or the liquid film can effectively control the reaction rate and course of the chlorination process, provide a reaction intermediate, and then avoid the chlorination and volatilization loss of nickel in the nickel-iron alloy. The principle mainly involved is as follows:

[0021] Membrane Construction: During this stage, the molar ratio of chlorine to gaseous ferric chloride in the gaseous chlorinating agent is controlled to be no higher than 0.5. By controlling the ratio of chlorine to ferric chloride in the chlorinating agent, the main reactions achieved are: FeCl3(g)+Fe→FeCl2(l) or FeCl3+Fe→FeCl2(s), Cl2(g)+Fe→FeCl2(l) or Cl2+Fe→FeCl2(s); accompanied by a small amount of Cl2(g)+Fe→FeCl3(g). Since the reaction primarily occurs on the surface of the nickel-iron alloy particles in the early stages, the resulting solid or liquid ferrous chloride film adheres to the nickel-iron alloy surface, forming an intermediate transition layer. Simultaneously, a small amount of Cl2(g)+Fe→FeCl3(g) occurs. The generation of ferric chloride gas can create certain gaps in the transition layer.

[0022] Directional chlorination and volatilization of iron: In this stage, the molar ratio of chlorine to gaseous ferric chloride in the gaseous chlorinating agent is 8-15. Chlorine contacts the intermediate transition layer, and the main reaction is: FeCl2(s / l)+Cl2(g)→FeCl3(g), which triggers the volatilization of ferrous chloride in the solid or liquid ferrous chloride film. However, due to the simultaneous occurrence of FeCl3(g)+Fe→FeCl2(l) or FeCl3+Fe→FeCl2(s), Cl2(g)+Fe→FeCl2(l) or Cl2+Fe→FeCl2(s), the transition layer is always present on the surface of the nickel-iron alloy, resulting in the volatilization of iron mainly occurring in the transition layer, which effectively inhibits the reaction rate, reduces local overheating, and prevents the chlorination of nickel and the outward volatilization of nickel (the boiling point of NiCl2 is 973°C, and the volatilization starting temperature is 671°C). This achieves the directional volatilization of iron in the nickel-iron alloy, while the nickel remains in the slag in the form of metallic nickel.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] (1) The present invention controls the composition of the chlorinating agent during the chlorination roasting process to achieve selective and directional volatilization of iron into the gas phase, while preventing nickel from being chlorinated. The separation of nickel and iron in the nickel-iron alloy can be achieved in only one step, and the process flow is short.

[0025] (2) The method of the present invention has a high resource utilization rate, and the iron volatilization rate is as high as over 90%. The volatilized iron can be condensed to obtain a high-quality ferric chloride product, while the nickel does not volatilize and remains in the slag in the form of particles. The slag can be easily ground into powder, and the powder can be used as the nickel front-end raw material required for power battery production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The figure is a process flow chart for separating nickel iron by chlorination roasting of nickel iron alloy in the present invention.

[0027] Figure 2 This is a phase analysis diagram of the nickel-rich powder obtained in Example 2 of the present invention.

[0028] Figure 3 This is a phase analysis diagram of the nickel-rich powder obtained in Example 3 of the present invention.

[0029] Figure 4 This is a phase analysis diagram of the calcined material obtained under the conditions of group a in comparative example 1 of the present invention.

[0030] Figure 5 This is a phase analysis diagram of the calcined material obtained under the conditions of group b in comparative example 1 of the present invention.

[0031] Figure 6 This is a phase analysis diagram of the calcined material obtained under the conditions of group C in comparative example 1 of the present invention. DETAILED DESCRIPTION

[0032] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0033] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0034] Unless otherwise specified, all reagents and raw materials used in the present invention are commercially available products or products that can be prepared by known methods.

[0035] The composition and particle size of the nickel-iron alloys treated in the following examples and comparative examples are shown in Table 1.

[0036] Table 1: Chemical composition of nickel-iron alloy (wt%)

[0037]

[0038] The gaseous ferric chloride in the following examples is formed by heating ferric chloride in a heating furnace.

[0039] Example 1:

[0040] A method for separating ferronickel by chlorination roasting of ferronickel of the present invention, the process flow is as follows Figure 1 As shown, the following steps are included:

[0041] (1) Nickel-iron alloy iron particles with a particle size of 1 to 2 cm are naturally piled up in a roasting furnace, and then argon gas is passed through the furnace to exhaust the air.

[0042] (2) A chlorinating agent is introduced into a roasting furnace for one-stage roasting, wherein the chlorinating agent is chlorine gas and gaseous ferric chloride, and the molar ratio of chlorine gas to gaseous ferric chloride is 0.1, the molar ratio of chlorine in the chlorinating agent to iron in the nickel-iron alloy is 1:5, the one-stage roasting temperature is controlled to 600° C., and the roasting is carried out for 10 minutes.

[0043] (3) After the first stage of roasting, the composition of the chlorinating agent is immediately adjusted and the second stage of roasting is started. During the second stage of roasting, the molar ratio of chlorine gas to gaseous ferric chloride is 8, and the molar ratio of chlorine in the chlorinating agent to iron in the nickel-iron alloy is 9:1. The roasting temperature is controlled at 600°C and the roasting time is 70 minutes to obtain the second stage roasting slag and gas.

[0044] (4) The roasting gas obtained in step (3) was subjected to staged condensation, with the first stage condensation temperature controlled at 150° C. to obtain solid ferric chloride, and the second stage condensation temperature controlled at 25° C. to obtain silicon tetrachloride. The solid ferric chloride obtained by the first stage condensation was subjected to component analysis, and the results showed that the purity of the ferric chloride was 99.4%. The silicon tetrachloride obtained by the second stage condensation was subjected to analysis, and the results showed that the purity of the silicon tetrachloride was 97.5%.

[0045] (5) The second-stage calcined slag was ball-milled with steel balls for 3 minutes to obtain nickel-rich powder. The chemical composition analysis of the nickel-rich powder showed that the volatility of iron was 93.7% and the volatility of nickel was 0%.

[0046] Example 2:

[0047] A method for separating ferronickel by chlorination roasting of ferronickel of the present invention, the process flow is as follows Figure 1 As shown, the following steps are included:

[0048] (1) Nickel-iron alloy iron particles with a particle size of 1 to 2 cm are naturally piled up in a roasting furnace, and then argon gas is passed through the furnace to exhaust the air.

[0049] (2) A chlorinating agent is introduced into a roasting furnace for one-stage roasting, wherein the chlorinating agent is chlorine gas and gaseous ferric chloride, and the molar ratio of chlorine gas to gaseous ferric chloride is 0.2, the molar ratio of chlorine in the chlorinating agent to iron in the nickel-iron alloy is 1:6, the one-stage roasting temperature is controlled to 680° C., and the roasting is performed for 8 minutes.

[0050] (3) After the first stage of roasting, the composition of the chlorinating agent is immediately adjusted and the second stage of roasting is started. During the second stage of roasting, the molar ratio of chlorine gas to gaseous ferric chloride is 12, and the molar ratio of chlorine in the chlorinating agent to iron in the nickel-iron alloy is 20:1. The roasting temperature is controlled at 680°C and the roasting time is 70 minutes to obtain the second stage roasting slag and gas.

[0051] (4) The roasting gas obtained in step (3) was subjected to staged condensation, with the first stage condensation temperature controlled at 100° C. to obtain solid ferric chloride, and the second stage condensation temperature controlled at 25° C. to obtain silicon tetrachloride. A component analysis of the solid ferric chloride obtained by the first stage condensation showed that the purity of the ferric chloride was 98.2%. A component analysis of the silicon tetrachloride obtained by the second stage condensation showed that the purity of the silicon tetrachloride was 97.7%.

[0052] (5) The second-stage calcined slag was ball-milled with steel balls for 3 minutes to obtain nickel-rich powder. The nickel-rich powder was subjected to phase and chemical composition analysis. The phase analysis showed that Figure 2 As shown, the results show that the main phases of nickel-rich powder are Ni, N3Fe, and FeCl3 (the iron chloride is a hydrate mainly due to the absorption of moisture in the air during the detection process). Chemical composition analysis shows that the volatility of iron is 94.9% and the volatility of nickel is 0%.

[0053] Example 3:

[0054] A method for separating ferronickel by chlorination roasting of ferronickel of the present invention, the process flow is as follows Figure 1 As shown, the following steps are included:

[0055] (1) Nickel-iron alloy iron particles with a particle size of 1 to 2 cm are naturally piled up in a roasting furnace, and then argon gas is passed through the furnace to exhaust the air.

[0056] (2) A chlorinating agent is introduced into a roasting furnace for one-stage roasting, wherein the chlorinating agent is chlorine gas and gaseous ferric chloride, and the molar ratio of chlorine gas to gaseous ferric chloride is 0.4, the molar ratio of chlorine in the chlorinating agent to iron in the nickel-iron alloy is 1:8, the one-stage roasting temperature is controlled to 650° C., and the roasting is carried out for 5 minutes.

[0057] (3) After the first stage of roasting, the composition of the chlorinating agent is immediately adjusted and the second stage of roasting is started. During the second stage of roasting, the molar ratio of chlorine gas to gaseous ferric chloride is 8, and the molar ratio of chlorine in the chlorinating agent to iron in the nickel-iron alloy is 55:1. The roasting temperature is controlled to 650°C and the roasting is carried out for 150 minutes to obtain second stage roasting slag and gas.

[0058] (4) The roasting gas obtained in step (3) was subjected to staged condensation, with the first stage condensation temperature controlled at 100° C. to obtain solid ferric chloride, and the second stage condensation temperature controlled at 25° C. to obtain silicon tetrachloride. The solid ferric chloride obtained by the first stage condensation was subjected to component analysis, and the results showed that the purity of the ferric chloride was 99.1%. The silicon tetrachloride obtained by the second stage condensation was subjected to analysis, and the results showed that the purity of the silicon tetrachloride was 97.2%.

[0059] (5) The second-stage roasting slag was ball-milled with steel balls for 3 minutes to obtain nickel-rich powder. The phase analysis was as follows: Figure 3 As shown, the results show that the main phases of nickel-rich powder are Ni, Ni3Fe, FeCl2, and FeCl3 (the iron chloride is a hydrate mainly due to the absorption of moisture in the air during the detection process). The chemical composition shows that the volatility of iron is 98.3% and the volatility of nickel is 0%.

[0060] Comparative Example 1:

[0061] The chlorination roasting method of nickel-iron alloy in this comparative example comprises the following steps:

[0062] (1) Nickel-iron alloy iron particles with a particle size of 1 to 2 cm were naturally piled and arranged in a roasting furnace, and then argon gas was passed through the furnace to exhaust the air in the furnace. Three independent experiments were carried out.

[0063] (2) Chlorine gas was introduced into the calcination furnace for calcination at a temperature of 600°C for 80 min. The three independent experiments were identical except for the amount of chlorine added. The amounts of chlorine added in the three independent experiments were: 3:1 (a), 10:1 (b), and 25:1 (c), respectively, based on the molar ratio of chlorine in chlorine gas to iron in nickel-iron alloy.

[0064] (3) After the calcination experiment, the calcined slag was taken for phase and chemical composition analysis. The phase analysis results are as follows Figure 4 、 Figure 5 and Figure 6 As shown. The result shows that all 3 groups of experiments of this comparative example have NiCl2 generation, show that chlorine roasting nickel-iron alloy easily causes the volatilization loss of nickel when chlorinating iron, nickel is also chlorinated simultaneously, and most of nickel has also been converted into nickel chloride in the slag. This is mainly due to adopting chlorine direct chlorination roasting nickel-iron alloy, because chlorination reaction is too violent and reaction exothermic, has caused local high temperature, has caused the chlorination and volatilization of nickel. Chemical composition analysis shows that the volatility of iron in 3 groups of independent experiments is respectively 62.4% (a), 86.7% (b), 95.7% (c), and the volatility of nickel is 3.9% (a), 6.4% (b), 16.5% (c).

Claims

1. A method for separating nickel iron by chlorination roasting of nickel iron alloy, characterized in that: The following steps are involved: (1) Placing the nickel-iron alloy in a roasting furnace; (2) introducing a gaseous chlorinating agent into a roasting furnace for staged roasting to obtain roasting slag and roasting gas phase; wherein the gaseous chlorinating agent is a mixture of chlorine and gaseous ferric chloride; the staged roasting is divided into two stages, wherein the roasting temperature of the first stage is 550-690°C and the roasting time is 5-15 minutes; the roasting temperature of the second stage is 550-750°C and the roasting time is 30-180 minutes; during the first stage roasting process, the molar ratio of chlorine in the gaseous chlorinating agent to the molar ratio of iron in the nickel-iron alloy is 1:5-1:10, and the molar ratio of chlorine in the gaseous chlorinating agent to gaseous ferric chloride is not higher than 0.5; during the second stage roasting process, the molar ratio of chlorine in the gaseous chlorinating agent to the molar ratio of iron in the nickel-iron alloy is 3:1-60:1, and the molar ratio of chlorine in the gaseous chlorinating agent to gaseous ferric chloride is 8-15; (3) The roasting gas phase obtained in step (2) is condensed in sections to obtain solid ferric chloride and liquid silicon tetrachloride respectively.

2. The method for separating ferronickel by chlorination roasting of ferronickel according to claim 1, wherein In step (3), the staged condensation means that the roasting gas phase is first condensed at 80 to 260°C for one stage and then condensed at 25 to 30°C for a second stage.

3. The method for separating ferronickel by chlorination roasting of ferronickel according to claim 1, wherein The calcined slag obtained in step (2) is ball-milled to obtain nickel-rich powder.

4. The method for separating ferronickel by chlorination roasting of ferronickel according to claim 1, wherein In step (1), the particle size of the nickel-iron alloy is 0.3 to 4 cm.

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