A method for preparing nickel-iron alloy using laterite nickel ore

Abstract

The present invention discloses a method for preparing nickel-iron alloy by using laterite nickel ore, belonging to the technical field of non-ferrous metal metallurgy. The method for preparing nickel-iron alloy by using laterite nickel ore of the present invention comprises the following steps: preparing the laterite nickel ore into pellets, then carrying out oxidation roasting and reduction roasting in sequence, and then carrying out smelting separation treatment to obtain nickel-iron alloy. Compared with the conventional laterite nickel ore treatment process, the present invention does not need to add solid carbonaceous reducing agents, alkali metal salt additives, etc. in the reduction stage, which can effectively reduce the treatment cost of laterite nickel ore and reduce the corrosion effect of additives on equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of non-ferrous metal metallurgy, and particularly to a method for preparing nickel-iron alloy by using laterite nickel ore. Background Art

[0002] In recent years, under the background of the full rise of the new energy battery industry and the rapid development of high-nickel and low-cobalt ternary precursors, the global demand for nickel resources has increased sharply, and laterite nickel ore has become an important development target for nickel resource supply. The mineralization process of laterite nickel ore is complex, and there are significant differences in the element content and ore phase composition of each ore layer. According to the different element contents, laterite nickel ore can be divided into three categories: limonite type, clay type, and humus type (silica-magnesium type), and most of them occur with the characteristics of low nickel and iron and high silica and magnesium.

[0003] At present, for the development and utilization of such low-grade laterite nickel ore, domestic and foreign scholars have proposed a series of technical solutions, mainly including rotary kiln pre-reduction - submerged arc furnace smelting method, reduction roasting - magnetic separation method, rotary hearth furnace pre-reduction - electric furnace smelting and separation method, and reduction sulfide smelting method. The rotary kiln pre-reduction - submerged arc furnace smelting method has mature technology, simple equipment, and high production efficiency, but has problems such as high energy consumption, large slag volume, high smelting temperature, and dust pollution. The reduction roasting - magnetic separation method has the advantages of low production cost and low energy consumption, but has problems such as rotary kiln ring formation and difficult reduction degree control. The rotary hearth furnace pre-reduction - electric furnace smelting and separation method has low energy consumption and a wide range of applicable raw materials and fuels, but has low thermal efficiency, high energy consumption, and high requirements for pellet strength. The reduction sulfide smelting method has mature technology, simple operation, and flexible product form, but has low nickel recovery rate, high energy consumption, and large pollution. The invention patent CN109097562A relates to a method for selective sulfide roasting of laterite nickel ore. In this method, laterite nickel ore is mixed and pelletized with raw materials including a carbonaceous reducing agent, a sulfiding agent, an alkali metal salt additive, and a binder. The obtained pellets are subjected to primary roasting at a low temperature and secondary roasting at a high temperature in sequence. The roasted material is used to recover nickel products by flotation, and the flotation tailings are used to recover iron products by magnetic separation. This method enables nickel to be selectively converted into nickel sulfide ore that is easy to separate by flotation through reduction-sulfide roasting, while iron is selectively converted into magnetite that is easy to separate by magnetic separation, and has good recovery effects on nickel and iron. However, when using this method to treat laterite nickel ore, multiple additives such as alkali metal salts need to be added, resulting in high production costs and serious corrosion of equipment. In addition, the sulfide roasting tail gas contains a large amount of SO2 gas, polluting the environment. Therefore, it is of great significance to develop a green, efficient, and economical method for treating low-grade laterite nickel ore. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing nickel-iron alloy using laterite nickel ore, so as to solve the problems existing in the above-mentioned prior art. The method of the present invention can achieve the efficient, clean and comprehensive utilization of low-grade silicon-magnesium type laterite nickel ore resources, and overcome the problems of large environmental pollution, high energy consumption, long process flow, low comprehensive recovery rate of nickel and iron, etc. existing in the existing processes.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: A method for preparing nickel-iron alloy using laterite nickel ore, comprising the following steps:

[0007] Prepare the laterite nickel ore into pellets, then carry out oxidative roasting and reduction roasting in sequence, and then carry out smelting separation treatment to obtain nickel-iron alloy.

[0008] Further, the pellets include the following raw materials: laterite nickel ore, binder and water;

[0009] The addition amount of the binder is 1-2% of the total mass of the laterite nickel ore and the binder;

[0010] The addition amount of the water is 7.5-10% of the total mass of the laterite nickel ore and the binder.

[0011] Further, the method for preparing the pellets includes the following steps:

[0012] Crush and grind the laterite nickel ore (grind to a particle size of <74μm with a content of ≥80%), then mix it evenly with the binder, then add water and mix well, stuff the material, form pellets, and dry to obtain the pellets.

[0013] Furthermore, the stuffing time is 35-40min; the binder includes sodium-based bentonite with a particle size of <74μm; the particle size of the formed pellets is 10-13mm; the drying temperature is 80-120°C, and the time is 30-60min; the water content of the pellets is <10%.

[0014] Further, the oxidative roasting specifically includes: preheating and then oxidative roasting in an air atmosphere.

[0015] Further, the preheating temperature is 800-900°C, and the time is 10-20min;

[0016] The oxidative roasting temperature is 1100-1200°C, and the time is 15-30min.

[0017] The compressive strength of the pellets obtained by oxidative roasting is >2500N.

[0018] Further, the reduction roasting includes gas-based reduction roasting.

[0019] Further, the reducing gas used in the gas-based reduction roasting includes a mixed gas of CO, H2, CO2, and N2 (waste gas generated by coal combustion); the flow rate of the reducing gas is 3 - 5 L / min;

[0020] The temperature of the reduction roasting is 800 - 1100 °C, and the time is 60 - 90 min.

[0021] Furthermore, in the mixed gas of CO, H2, CO2, and N2, the volume ratio of H2 to CO is (1.0 - 2.5):1, and the volume fractions of both CO2 and N2 are 5%.

[0022] In the metallized pellets obtained by reduction roasting, the nickel metallization rate > 87% and the iron metallization rate > 55%.

[0023] Further, before the smelting separation treatment, it also includes: after crushing the metallized pellets obtained by reduction roasting (crushing to a particle size < 1 mm), mixing them evenly with a carbonaceous reducing agent and a fluxing agent.

[0024] Further, the carbonaceous reducing agent includes coal or graphite; the particle size of the coal or graphite < 1 mm.

[0025] The molar ratio of carbon in the carbonaceous reducing agent to the total amount of oxygen in the iron and nickel oxides in the metallized pellets is (1.2 - 1.5):1;

[0026] The fluxing agent includes fluorite (CaF2) and lime (CaO); the particle size of the fluxing agent < 1 mm.

[0027] The temperature of the smelting separation treatment is 1500 - 1650 °C, and the time is 40 - 60 min.

[0028] Furthermore, the addition amount of fluorite is 2 - 6% of the mass of the metallized pellets; the addition amount of lime is determined according to the melt basicity (CaO / SiO2), and adding lime makes the melt basicity 0.8 - 1.2.

[0029] In the nickel-iron alloy, the nickel grade > 18%, the nickel recovery rate > 85%, the iron grade > 75%, and the iron recovery rate > 55%.

[0030] Performing smelting separation treatment on the metallized pellets obtained by reduction roasting, while quickly melting, controlling the reduction potential of the system (adding carbonaceous reducing agent, fluxing agent, etc.) and the properties of the slag, the reduction of nickel and iron and the separation of slag and iron can be completed.

[0031] The present invention discloses the following technical effects:

[0032] (1) The process flow of the present invention is simple, the raw material applicability is strong, the industrial application is energy-saving and environment-friendly, the nickel-iron recovery rate is high, and it is easy to realize large-scale application.

[0033] (2) Based on gas-based direct reduction, this invention uses coal gas (a mixture of CO, H2, CO2, and N2) as a reducing agent in the reduction roasting stage, replacing the solid reducing agent coal in the traditional laterite nickel ore roasting process. While ensuring the full reduction of nickel-iron oxides, it reduces CO2 emissions, with advantages such as high reduction efficiency, cleanliness, and environmental friendliness.

[0034] (3) Compared with the conventional laterite nickel ore treatment process, this invention does not require the addition of solid carbonaceous reducing agents, alkali metal salt additives, etc. in the reduction stage, which can effectively reduce the treatment cost of laterite nickel ore and reduce the corrosion of additives on equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To more clearly illustrate the technical solutions in the embodiments of this invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of this invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1 It is a schematic flow diagram of preparing ferronickel alloy using laterite nickel ore in this invention. DETAILED DESCRIPTION OF THE INVENTION

[0037] Now, various exemplary embodiments of this invention will be described in detail. This detailed description should not be considered as a limitation of this invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of this invention.

[0038] It should be understood that the terms used in this invention are only for describing specific embodiments and are not used to limit this invention. Additionally, for the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in this invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0039] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0040] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the description of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of the present invention are obvious to those skilled in the art. The description and examples of this application are merely exemplary.

[0041] The schematic process diagram of preparing nickel-iron alloy from laterite nickel ore by the present invention is shown in Figure 1 .

[0042] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0043] Example 1

[0044] A method for preparing nickel-iron alloy from laterite nickel ore:

[0045] (1) Raw material preparation

[0046] Crush and grind the laterite nickel ore sample (grind to a particle size of <74μm with a content of 85%), mix the finely ground laterite nickel ore powder sample and sodium-based bentonite with a particle size of <74μm (the addition amount of sodium-based bentonite is 1% of the total mass of laterite nickel ore and sodium-based bentonite) evenly in a planetary mixer, then take out the mixture, externally add 8% by mass of water (the addition amount of water is 8% of the total mass of laterite nickel ore and binder), mix well and then let it stand (for 35 minutes).

[0047] The total Fe content in the laterite nickel ore is 10.53 wt.%, the Ni content is 0.85 wt.%, the MgO content is 33.21 wt.%, the SiO2 content is 36.53 wt.%, the Al2O3 content is 1.87 wt.%, and the balance is impurities.

[0048] (2) Pellet preparation

[0049] Place the material after standing in a disc pelletizer to prepare green pellets with a particle size of 10 mm. After the green pellets are made, put them into a blast drying oven and dry them at 80°C for 60 minutes (under air atmosphere) to obtain dry pellets with a water content of 9.5%.

[0050] (3) Preheating and oxidative roasting

[0051] Place the dried pellets in a muffle furnace, first preheat them at 800°C for 20 minutes, then adjust the temperature of the muffle furnace to 1100°C and carry out oxidative roasting for 20 minutes to obtain oxidized roasted pellets with a compressive strength of 2600 N. Both preheating and oxidative roasting are carried out under air atmosphere.

[0052] (4) Gas-based reduction roasting

[0053] Place the oxidized roasted pellets in a closed reduction furnace, and introduce a mixed gas of CO, H2, CO2 and N2 (the volume ratio of H2 and CO in the mixed gas is 2.0:1, and the volume fractions of CO2 and N2 are both 5%) for reduction roasting operation. The flow rate of the mixed gas is 3 L / min, the temperature of reduction roasting is 800 °C, and the time of reduction roasting is 90 min to obtain metallized pellets with a nickel metallization rate of 92% and an iron metallization rate of 57%.

[0054] (5) Smelting and separation treatment

[0055] Crush the metallized pellets obtained by reduction roasting into powder samples with a particle size < 1 mm, and mix the powder samples evenly with pulverized coal with a particle size < 1 mm and a flux (fluorite and lime) with a particle size < 1 mm. Among them, the molar ratio of carbon in the pulverized coal to the total molar amount of oxygen in iron and nickel oxides in the metallized pellets is 1.2:1. The addition amount of fluorite is 4% of the mass of the metallized pellets, and the addition amount of lime is determined according to the melt basicity (CaO / SiO2). Add lime to make the melt basicity 0.8; then place the mixture in an induction furnace for smelting and separation treatment. The temperature of smelting and separation treatment is 1650 °C, and the smelting and separation time is 40 min. Finally, a nickel-iron alloy is obtained, with a nickel grade (mass percentage content of nickel in the nickel-iron alloy) of 20.23%, a nickel recovery rate of 95.82%, an iron grade (mass percentage content of iron in the nickel-iron alloy) of 78.14%, and an iron recovery rate of 54.21%.

[0056] Example 2

[0057] A method for preparing nickel-iron alloy using laterite nickel ore:

[0058] (1) Raw material preparation

[0059] Crush and grind the laterite nickel ore sample (grind it to a particle size < 74 μm with a content of 80%). Mix the finely ground laterite nickel ore powder sample and sodium-based bentonite with a particle size < 74 μm (the addition amount of sodium-based bentonite is 2% of the total mass of laterite nickel ore and sodium-based bentonite) evenly in a planetary mixer. Then take out the mixture and externally add 9.5% by mass of water (the addition amount of water is 9.5% of the total mass of laterite nickel ore and binder) and mix well, and then leave it for 40 min for material retting.

[0060] The total Fe content in the laterite nickel ore is 9.82 wt.%, the Ni content is 0.91 wt.%, the MgO content is 32.65 wt.%, the SiO2 content is 38.97 wt.%, the Al2O3 content is 0.83 wt.%, and the balance is impurities.

[0061] (2) Pellet preparation

[0062] The stuff that has been sealed is placed in a disc pelletizer to prepare green pellets with a particle size of 10 mm. After the green pellets are made, they are put into a forced-air drying oven and dried for 45 min under the condition of a temperature of 100 °C (in an air atmosphere) to obtain dried pellets with a water content of 9.0%.

[0063] (3) Preheating and oxidative roasting

[0064] The dried pellets are placed in a muffle furnace, preheated at 900 °C for 15 min first, and then the temperature of the muffle furnace is adjusted to 1200 °C for oxidative roasting for 15 min to obtain oxidized roasted pellets with a compressive strength of 2700 N. Both preheating and oxidative roasting are carried out in an air atmosphere.

[0065] (4) Gas-based reduction roasting

[0066] The oxidized roasted pellets are placed in a closed reduction furnace, and a mixed gas of CO, H2, CO2, and N2 (the volume ratio of H2 and CO in the mixed gas is 2.5:1, and the volume fractions of CO2 and N2 are both 5%) is introduced for reduction roasting operation. The flow rate of the mixed gas is 4.5 L / min, the reduction roasting temperature is 950 °C, and the reduction roasting time is 78 min to obtain metallized pellets with a nickel metallization rate of 97% and an iron metallization rate of 59%.

[0067] (5) Smelting and separation treatment

[0068] The metallized pellets obtained by reduction roasting are crushed into powder samples with a particle size < 1 mm. The powder samples are mixed evenly with pulverized coal with a particle size < 1 mm and a flux (fluorite and lime) with a particle size < 1 mm. Among them, the ratio of the amount of substance of carbon in the pulverized coal to the total amount of substance of oxygen in the iron and nickel oxides in the metallized pellets is 1.5:1. The addition amount of fluorite is 2% of the mass of the metallized pellets, and the addition amount of lime is determined according to the melt basicity (CaO / SiO2). Lime is added to make the melt basicity 1.0; subsequently, the mixture is placed in an induction furnace for smelting and separation treatment. The smelting and separation treatment temperature is 1550 °C, and the smelting and separation time is 50 min. Finally, a nickel-iron alloy is obtained with a nickel grade of 19.85%, a nickel recovery rate of 96.27%, an iron grade of 76.38%, and an iron recovery rate of 55.62%.

[0069] Example 3

[0070] A method for preparing nickel-iron alloy using laterite nickel ore:

[0071] (1) Raw material preparation

[0072] The laterite nickel ore sample is crushed and ground (ground to a particle size of less than 74 μm with a content of 85% in the particle size fraction). The finely ground laterite nickel ore powder sample and sodium-based bentonite with a particle size of less than 74 μm (the addition amount of sodium-based bentonite is 1.5% of the total mass of laterite nickel ore and sodium-based bentonite) are mixed evenly in a planetary mixer. Subsequently, the mixed material is taken out, and water with a mass fraction of 8.0% (the addition amount of water is 8.0% of the total mass of laterite nickel ore and binder) is externally added and thoroughly mixed, followed by material sealing (for 35 minutes).

[0073] The total Fe content in the laterite nickel ore is 10.68 wt.%, the Ni content is 0.85 wt.%, the MgO content is 33.56 wt.%, the SiO2 content is 38.11 wt.%, the Al2O3 content is 1.32 wt.%, and the balance is impurities.

[0074] (2) Pellet preparation

[0075] The sealed material is placed in a disk pelletizer to prepare green pellets with a particle size of 12 mm. After the green pellets are made, they are put into a forced-air drying oven and dried for 30 minutes at a temperature of 120 °C (under an air atmosphere), obtaining dried pellets with a water content of 8.7%.

[0076] (3) Preheating and oxidative roasting

[0077] The dried pellets are placed in a muffle furnace, preheated at 850 °C for 20 minutes first, and then the temperature of the muffle furnace is adjusted to 1100 °C for oxidative roasting for 30 minutes, obtaining oxidized roasted pellets with a compressive strength of 2650 N. Both preheating and oxidative roasting are carried out under an air atmosphere.

[0078] (4) Gas-based reduction roasting

[0079] The oxidized roasted pellets are placed in a closed reduction furnace, and a mixed gas of CO, H2, CO2, and N2 is introduced (the volume ratio of H2 and CO in the mixed gas is 2.0:1, and the volume fractions of CO2 and N2 are both 5%) for reduction roasting operation. The flow rate of the mixed gas is 5 L / min, the reduction roasting temperature is 1100 °C, and the reduction roasting time is 60 minutes, obtaining metallized pellets with a nickel metallization rate of 96% and an iron metallization rate of 57%.

[0080] (5) Smelting separation treatment

[0081] The metallized pellets obtained by reduction roasting are crushed into a powder sample with a particle size < 1 mm. The powder sample is uniformly mixed with pulverized coal with a particle size < 1 mm and a flux (fluorite and lime) with a particle size < 1 mm. Among them, the molar ratio of carbon in the pulverized coal to the total molar amount of oxygen in iron and nickel oxides in the metallized pellets is 1.3:1. The addition amount of fluorite is 2% of the mass of the metallized pellets, and the addition amount of lime is determined according to the melt basicity (CaO / SiO2). Lime is added to make the melt basicity 1.2. Subsequently, the mixture is placed in an induction furnace for smelting and separation treatment. The temperature of the smelting and separation treatment is 1550 °C, and the smelting and separation time is 60 min. Finally, a nickel-iron alloy is obtained, with a nickel grade of 22.32%, a nickel recovery rate of 97.68%, an iron grade of 75.13%, and an iron recovery rate of 56.36%.

[0082] Comparative Example 1

[0083] Same as Example 3, the only difference is that there is no preheating and oxidation roasting stage.

[0084] Comparative Example 2

[0085] Same as Example 3, the only difference is that pure CO is used as the reducing gas in the gas-based reduction roasting stage.

[0086] Comparative Example 3

[0087] Same as Example 3, the only difference is that pure H2 is used as the reducing gas in the gas-based reduction roasting stage.

[0088] Comparative Example 4

[0089] Same as Example 3, the only difference is that the reducing gas flow rate in the gas-based reduction stage is 1 L / min.

[0090] Comparative Example 5

[0091] Same as Example 3, the only difference is that the reducing gas flow rate in the gas-based reduction stage is 8 L / min.

[0092] Comparative Example 6

[0093] Same as Example 3, the only difference is that the temperature of the reduction roasting in step (4) is 600 °C.

[0094] Comparative Example 7

[0095] Same as Example 3, the only difference is that the temperature of the reduction roasting in step (4) is 1200 °C.

[0096] The results of the nickel grade, iron grade, nickel recovery rate, and iron recovery rate of the nickel-iron alloys prepared in Comparative Examples 1-7 are shown in Table 1.

[0097] Table 1 Nickel grade, iron grade, nickel recovery rate, and iron recovery rate of nickel-iron alloys

[0098]

[0099] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing nickel-iron alloy using laterite nickel ore, characterized in that: The following steps are involved: The laterite nickel ore is prepared into pellets, and then oxidative roasting and reduction roasting are performed in sequence, and then smelting treatment is performed to obtain nickel-iron alloy; The pellets include the following raw materials: laterite nickel ore, a binder and water; The amount of the binder added is 1-2% of the total mass of the laterite nickel ore and the binder; The reduction roasting is gas-based reduction roasting; The reducing gas used in the gas-based reduction roasting includes a mixed gas of CO, H2, CO2 and N2; the flow rate of the reducing gas is 3 to 5 L / min; Before the melting treatment, the process also includes: crushing the metallized pellets obtained after the reduction roasting and mixing them evenly with the carbonaceous reducing agent and the flux; The flux includes fluorite and lime.

2. The method according to claim 1, characterized in that The amount of water added is 7.5-10% of the total mass of the laterite nickel ore and the binder.

3. The method according to claim 2, characterized in that The method for preparing the pellets comprises the following steps: The laterite nickel ore is crushed and mixed evenly with a binder, and then water is added to fully mix, and the material is simmered, pelletized, and dried to obtain the pellets.

4. The method according to claim 1, characterized in that The oxidation roasting specifically includes: oxidation roasting after preheating in an air atmosphere.

5. The method according to claim 4, characterized in that The preheating temperature is 800-900°C and the time is 10-20 minutes; The temperature of the oxidation roasting is 1100-1200° C., and the time is 15-30 minutes.

6. The method according to claim 1, characterized in that The reduction roasting is carried out at a temperature of 800 to 1100° C. and for a time of 60 to 90 minutes.

7. The method according to claim 1, characterized in that The carbonaceous reducing agent includes coal or graphite; The ratio of the amount of carbon in the carbonaceous reducing agent to the total amount of oxygen in the iron and nickel oxides in the metallized pellets is (1.2-1.5):1; The temperature of the melting treatment is 1500-1650° C., and the time is 40-60 minutes.

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